NMR Water Self–Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions

PubMed Central

Bai, Ruiliang; Basser, Peter J.; Briber, Robert M.; Horkay, Ferenc

2013-01-01

Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca2+ and Na+. Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na+ on the mobility of water molecules was practically undetectable. By contrast, addition of Ca2+ strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced. PMID:24409001

NMR Water Self-Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions.

PubMed

Bai, Ruiliang; Basser, Peter J; Briber, Robert M; Horkay, Ferenc

2014-03-15

Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca 2+ and Na + . Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na + on the mobility of water molecules was practically undetectable. By contrast, addition of Ca 2+ strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced.

Manufacturing polymer light emitting diode with high luminance efficiency by solution process

NASA Astrophysics Data System (ADS)

Kim, Miyoung; Jo, SongJin; Yang, Ho Chang; Yoon, Dang Mo; Kwon, Jae-Taek; Lee, Seung-Hyun; Choi, Ju Hwan; Lee, Bum-Joo; Shin, Jin-Koog

2012-06-01

While investigating polymer light emitting diodes (polymer-LEDs) fabricated by solution process, surface roughness influences electro-optical (E-O) characteristics. We expect that E-O characteristics such as luminance and power efficiency related to surface roughness and layer thickness of emitting layer with poly-9-Vinylcarbazole. In this study, we fabricated polymer organic light emitting diodes by solution process which guarantees easy, eco-friendly and low cost manufacturing for flexible display applications. In order to obtain high luminescence efficiency, E-O characteristics of these devices by varying parameters for printing process have been investigated. Therefore, we optimized process condition for polymer-LEDs by adjusting annealing temperatures of emission, thickness of emission layer showing efficiency (10.8 cd/A) at 10 mA/cm2. We also checked wavelength dependent electroluminescence spectrum in order to find the correlation between the variation of efficiency and the thickness of the layer.

Effect of polymer matrix on structure of Se particles formed in aqueous solutions during redox process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suvorova, E. I., E-mail: suvorova@ns.crys.ras.ru; Klechkovskaya, V. V.

2010-12-15

Transmission electron microscopy and X-ray energy dispersive microanalysis study of the structure of particles formed during the reduction of Se(IV) to Se(0) in aqueous solutions in the presence of amphiphilic polymers showed the formation of Se/polymer composite particles. The content of carbon inside the particles can be as large as 80 at %. Polymers deeply influence the structure of particles. Depending on polymers, the composite particles may be unstable with time and they spontaneously evolve from Se/polymer composite particles to crystalline particles of monoclinic Se. For the stable ones, addition of bacterial cellulose Acetobacter xylinum gel-film can induce crystallization inmore » the particles which expel the polymeric material. The Se/polymer composite particles and Se crystalline particles exhibit different sensitivity to electron irradiation and stiffness.« less

Effect of pH on chitosan hydrogel polymer network structure.

PubMed

Xu, Hongcheng; Matysiak, Silvina

2017-06-29

Chitosan is a molecule that can form water-filled 3D polymer networks with a wide range of applications. A new coarse-grained model for chitosan hydrogel was developed to explore its pH-dependent self-assembly behavior and mechanical properties. Our results indicate that the underlying polymer physical crosslinking pattern induced by solution pH has a significant effect on hydrogel elastic moduli. With this model, we obtain pH-dependent structural and mechanical property changes in agreement with experimental observations, and provide a molecular mechanism behind the changes in polymer crosslinking patterns.

Thermoluminescence of the Films, Nanocomposites, and Solutions of the Silicon Organic Polymer Poly(di- n-hexyl silane)

NASA Astrophysics Data System (ADS)

Ostapenko, N. I.; Kerita, O. A.; Ostapenko, Yu. V.

2018-03-01

A comparative study of low-temperature thermoluminescence (5-120 K) of silicon organic polymer poly(di-n-hexyl silane) films, nanocomposites (when the polymer is introduced into nanopores of silica MCM-41 and SBA-15 with diameter of pores 2.8 and 10 nm) as well as solutions of polymer in tetrahydrofuran with different concentrations from 10-3 to 10-5 mol/L was carried out. It was shown that it is possible to control the number of charge carrier traps, as well as their energy distribution by changing the diameter of silica nanopores. It is established that maxima and FWHMs of the thermoluminescence curves of nanocomposites significantly depend on the pore diameter of the nanoporous silica. This result agrees with the data obtained in the investigation of polymer solutions. In the nanocomposite with a minimum pore diameter (2.8 nm), the number and depth of the traps as well as dispersion of their energy are significantly reduced compared to their values in the polymer film.

Convective polymer assembly for the deposition of nanostructures and polymer thin films on immobilized particles.

PubMed

Richardson, Joseph J; Björnmalm, Mattias; Gunawan, Sylvia T; Guo, Junling; Liang, Kang; Tardy, Blaise; Sekiguchi, Shota; Noi, Ka Fung; Cui, Jiwei; Ejima, Hirotaka; Caruso, Frank

2014-11-21

We report the preparation of polymer particles via convective polymer assembly (CPA). Convection is used to move polymer solutions and cargo through an agarose gel that contains immobilized template particles. This method both coats and washes the particles in a process that is amenable to automation, and does not depend on passive diffusion or electrical currents, thus facilitating incorporation of fragile and nanoscale objects, such as liposomes and gold nanoparticles, into the thin polymer films. Template dissolution leads to the formation of stable polymer particles and capsules.

DNA translocation across protein channels: How does a polymer worm through a hole?

NASA Astrophysics Data System (ADS)

Muthukumar, M.

2001-03-01

Free energy barriers control the translocation of polymers through narrow channels. Based on an analogy with the classical nucleation and growth process, we have calculated the translocation time and its dependencies on the length, stiffness, and sequence of the polymer, solution conditions, and the strength of the driving electrochemical potential gradient. Our predictions will be compared with experimental results and prospects of reading polymer sequences.

Investigating the Influence of Polymers on Supersaturated Flufenamic Acid Cocrystal Solutions.

PubMed

Guo, Minshan; Wang, Ke; Hamill, Noel; Lorimer, Keith; Li, Mingzhong

2016-09-06

The development of enabling formulations is a key stage when demonstrating the effectiveness of pharmaceutical cocrystals to maximize the oral bioavailability for poorly water soluble drugs. Inhibition of drug crystallization from a supersaturated cocrystal solution through a fundamental understanding of the nucleation and crystal growth is important. In this study, the influence of the three polymers of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and a copolymer of N-vinly-2-pyrrodidone (60%) and vinyl acetate (40%) (PVP-VA) on the flufenamic acid (FFA) crystallization from three different supersaturated solutions of the pure FFA and two cocrystals of FFA-NIC CO and FFA-TP CO has been investigated by measuring nucleation induction times and desupersaturation rates in the presence and absence of seed crystals. It was found that the competition of intermolecular hydrogen bonding among drug/coformer, drug/polymer, and coformer/polymer was a key factor responsible for maintaining supersaturation through nucleation inhibition and crystal growth modification in a cocrystal solution. The supersaturated cocrystal solutions with predissolved PEG demonstrated more effective stabilization in comparison to the pure FFA in the presence of the same polymer. In contrast, neither of the two cocrystal solutions, in the presence of PVP or PVP-VA, exhibited a better performance than the pure FFA with the same predissolved polymer. The study suggests that the selection of a polymeric excipient in a cocrystal formulation should not be solely dependent on the interplay of the parent drug and polymer without considering the coformer effects.

Self-Assembled CNT-Polymer Hybrids in Single-Walled Carbon Nanotubes Dispersed Aqueous Triblock Copolymer Solutions

NASA Astrophysics Data System (ADS)

Vijayaraghavan, D.; Manjunatha, A. S.; Poojitha, C. G.

2018-04-01

We have carried out scanning electron microscopy (SEM), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), electrical conductivity, and 1H NMR studies as a function of temperature on single-walled carbon nanotubes (SWCNTs) dispersed aqueous triblock copolymer (P123) solutions. The single-walled carbon nanotubes in this system aggregate to form bundles, and the bundles aggregate to form net-like structures. Depending on the temperature and phases of the polymer, this system exhibits three different self-assembled CNT-polymer hybrids. We find CNT-unimer hybrid at low temperatures, CNT-micelle hybrid at intermediate temperatures wherein the polymer micelles are adsorbed in the pores of the CNT nets, and another type of CNT-micelle hybrid at high temperatures wherein the polymer micelles are adsorbed on the surface of the CNT bundles. Our DSC thermogram showed two peaks related to these structural changes in the CNT-polymer hybrids. Temperature dependence of the 1H NMR chemical shifts of the molecular groups of the polymer and the AC electrical conductivity of the composite also showed discontinuous changes at the temperatures at which the CNT-polymer hybrid's structural changes are seen. Interestingly, for a higher CNT concentration (0.5 wt.%) in the system, the aggregated polymer micelles adsorbed on the CNTs exhibit cone-like and cube-like morphologies at the intermediate and at high temperatures respectively.

Both solubility and chemical stability of curcumin are enhanced by solid dispersion in cellulose derivative matrices.

PubMed

Li, Bin; Konecke, Stephanie; Wegiel, Lindsay A; Taylor, Lynne S; Edgar, Kevin J

2013-10-15

Amorphous solid dispersions (ASD) of curcumin (Cur) in cellulose derivative matrices, hydroxypropylmethylcellulose acetate succinate (HPMCAS), carboxymethylcellulose acetate butyrate (CMCAB), and cellulose acetate adipate propionate (CAAdP) were prepared in order to investigate the structure-property relationship and identify polymer properties necessary to effectively increase Cur aqueous solution concentration. XRD results indicated that all investigated solid dispersions were amorphous, even at a 9:1 Cur:polymer ratio. Both stability against crystallization and Cur solution concentration from these ASDs were significantly higher than those from physical mixtures and crystalline Cur. Remarkably, curcumin was also stabilized against chemical degradation in solution. Chemical stabilization was polymer-dependent, with stabilization in CAAdP>CMCAB>HPMCAS>PVP, while matrices enhanced solution concentration as PVP>HPMCAS>CMCAB≈CAAdP. HPMCAS/Cur dispersions have useful combinations of pH-triggered release profile, chemical stabilization, and strong enhancement of Cur solution concentration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Roles of Segmental and Oligomeric Diffusion on the Gel Effect in Free Radical Polymerization

NASA Astrophysics Data System (ADS)

Wisnudel, M. B.; Torkelson, J. M.

1996-03-01

Termination between radicals has been simulated by phosphorescence quenching, showing strong roles for segmental and oligomeric radical self-diffusion in the origin of the gel effect. Quenching rate constants (k_q) were measured between benzil-terminated polymer as a function of anthracene-terminated polymer in polymer solutions. In dilute solution, interactions between 10k or 73k MW benzil-terminated polystyrene (PS- B) and anthracence-terminated polystyrene (PS-A) of varying MW, the MW effect is weaker than the Smoluchowski eq. prediction (kq MW^- 0.5). At higher concentration, interactions of PS-B and PS-A of like MW show only weak dependence of kq on MW and a concentration dependence similar to that of segmental mobility, indicating that segmental diffusion is important in termination. Finally, with interactions between 73k MW PS-B and PS-A of varying MW at 35 wt% PS, kq decreases by a factor of 10 in going from MW's of 100 to 1000 g/mol; beyond 1000 g/mol, kq is MW independent. Such effects cannot be explained by polymer-radical self-diffusion. However, they support the notion that the gel effect onset is associated with the concentration dependence of oligomeric radical self-diffusion and polymer radical chain-end segmental mobility.

Theory of DNA electrophoresis in physical gels and entangled polymer solutions

NASA Astrophysics Data System (ADS)

Duke, Thomas; Viovy, Jean Louis

1994-03-01

A scaling theory is presented for the electrophoretic mobility of DNA in sieving media that form dynamically evolving meshworks, such as physical gels and solutions of entangled polymers. In such media, the topological constraints on the DNA's motion are perpetually changing as cross links break and rejoin or as the polymers diffuse. It is shown that if the rate of constraint release falls within a certain range (which depends on the field strength), fractionation can be extended to higher molecular weights than would be feasible using a permanent gel of equivalent pore size. This improvement is a consequence of the disruptive effect that constraint release has on the mechanism of molecular orientation. Numerical simulations support the predictions of the theory. The possibility of realizing such a system in practice, with the aim of improving on current electrophoresis methods, is commented upon. It is suggested that semidilute polymer solutions may be a versatile medium for the rapid separation of long single-stranded DNA molecules, and the particular quality of solution required is identified.

Statistical and hydrodynamic properties of double-ring polymers with a fixed linking number between twin rings.

PubMed

Uehara, Erica; Deguchi, Tetsuo

2014-01-28

For a double-ring polymer in solution we evaluate the mean-square radius of gyration and the diffusion coefficient through simulation of off-lattice self-avoiding double polygons consisting of cylindrical segments with radius rex of unit length. Here, a self-avoiding double polygon consists of twin self-avoiding polygons which are connected by a cylindrical segment. We show numerically that several statistical and dynamical properties of double-ring polymers in solution depend on the linking number of the constituent twin ring polymers. The ratio of the mean-square radius of gyration of self-avoiding double polygons with zero linking number to that of no topological constraint is larger than 1, in particular, when the radius of cylindrical segments rex is small. However, the ratio is almost constant with respect to the number of vertices, N, and does not depend on N. The large-N behavior of topological swelling is thus quite different from the case of knotted random polygons.

Nanoparticle stability in semidilute and concentrated polymer solutions.

PubMed

Dutta, Nupur; Green, David

2008-05-20

The wetting of PDMS-grafted silica spheres (PDMS- g-silica) is connected to their depletion restabilization in semidilute and concentrated PDMS/cyohexane polymer solutions. Specifically, we found that a wetting diagram of chemically identical graft and free homopolymers predicts stability of hard, semisoft, and soft spheres as a function of the bulk free polymer volume fraction, graft density, and the graft and free polymer chain lengths. The transition between stable and aggregated regions is determined optically and with dynamic light scattering. The point of demarcation between the regions occurs when the graft and free polymer chains are equal in length. When graft chains are longer than free chains, the particles are stable; in contrast, the particles are unstable when the opposite is true. The regions of particle stability and instability are corroborated with theoretical self-consistent mean-field calculations, which not only show that the grafted brush is responsible for particle dispersion in the complete wetting region but also aggregation in the incomplete wetting region. Ultimately, our results indicate that depletion restabilization depends on the interfacial properties of the nanoparticles in semidilute and concentrated polymer solutions.

Design of Donor Polymers with Strong Temperature-Dependent Aggregation Property for Efficient Organic Photovoltaics.

PubMed

Hu, Huawei; Chow, Philip C Y; Zhang, Guangye; Ma, Tingxuan; Liu, Jing; Yang, Guofang; Yan, He

2017-10-17

Bulk heterojunction (BHJ) organic solar cells (OSCs) have attracted intensive research attention over the past two decades owing to their unique advantages including mechanical flexibility, light weight, large area, and low-cost fabrications. To date, OSC devices have achieved power conversion efficiencies (PCEs) exceeding 12%. Much of the progress was enabled by the development of high-performance donor polymers with favorable morphological, electronic, and optical properties. A key problem in morphology control of OSCs is the trade-off between achieving small domain size and high polymer crystallinity, which is especially important for the realization of efficient thick-film devices with high fill factors. For example, the thickness of OSC blends containing state-of-the-art PTB7 family donor polymers are restricted to ∼100 nm due to their relatively low hole mobility and impure polymer domains. To further improve the device performance and promote commercialization of OSCs, there is a strong demand for the design of new donor polymers that can achieve an optimal blend morphology containing highly crystalline yet reasonably small domains. In this Account, we highlight recent progress on a new family of conjugated polymers with strong temperature-dependent aggregation (TDA) property. These polymers are mostly disaggregated and can be easily dissolved in solution at high temperatures, yet they can strongly aggregate when the solution is cooled to room temperature. This unique aggregation property allows us to control the disorder-order transition of the polymer during solution processing. By preheating the solution to high temperature (∼100 °C), the polymer chains are mostly disaggregated before spin coating; as the temperature of the solution drops during the spin coating process, the polymer can strongly aggregate and form crystalline domains yet that are not excessivelylarge. The overall blend morphology can be optimized by various processing conditions (e.g., temperature, spin-rates, concentration, etc.). This well-controlled and near-optimal BHJ morphology produced over a dozen cases of efficient OSCs with an active layer nearly 300 nm thick that can still achieve high FFs (70-77%) and efficiencies (10-11.7%). By studying the structure-property relationships of the donor polymers, we show that the second position branched alkyl chains and the fluorination on the polymer backbone are two key structural features that enable the strong TDA property. Our comparative studies also show that the TDA polymer family can be used to match with non-fullerene acceptors yielding OSCs with low voltage losses. The key difference between the empirical matching rules for fullerene and non-fullerene OSCs is that TDA polymers with slightly reduced crystallinity appear to match better with small molecular acceptors and yield higher OSC performances.

Length scale dependence of the dynamic properties of hyaluronic acid solutions in the presence of salt.

PubMed

Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik

2010-12-02

In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D(NSE) measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D(DLS). This behavior contrasts with neutral polymer solutions. With increasing salt content, D(DLS) approaches D(NSE), which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hückel length.

Chemotaxis of Molecular Dyes in Polymer Gradients in Solution.

PubMed

Guha, Rajarshi; Mohajerani, Farzad; Collins, Matthew; Ghosh, Subhadip; Sen, Ayusman; Velegol, Darrell

2017-11-08

Chemotaxis provides a mechanism for directing the transport of molecules along chemical gradients. Here, we show the chemotactic migration of dye molecules in response to the gradients of several different neutral polymers. The magnitude of chemotactic response depends on the structure of the monomer, polymer molecular weight and concentration, and the nature of the solvent. The mechanism involves cross-diffusion up the polymer gradient, driven by favorable dye-polymer interaction. Modeling allows us to quantitatively evaluate the strength of the interaction and the effect of the various parameters that govern chemotaxis.

Molecular Level Investigations of Interfacial Friction of Polymer Brush Surfaces

NASA Astrophysics Data System (ADS)

Perry, Scott

2005-03-01

The development of synthetic polymer lubricants to mimic joint lubrication within the human body will be presented. Unlike most industrial applications involving oils and greases, lubrication of these joints is accomplished in an aqueous environment. Fundamentally, water is a poor lubricant in most settings due to the weak pressure dependence of its viscosity, yet the contacting surfaces of skeletal joints function with low friction throughout a lifetime. Motivated by the molecular structure of materials making up joint surfaces, interfacial friction between polymer brush surfaces under aqueous environments has been probed with an array of molecularly sensitive surface analytical techniques including atomic force microscopy. The brush surfaces, comprised of poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), have been generated through the spontaneous adsorption of polymer from solution onto oxide substrates and sodium borosilicate surfaces (AFM tip). The character of the polymer films has been investigated in-situ with the quartz crystal microbalance (QCM) and atomic force microscope (AFM) and ex-situ with ellipsometry and X-ray photoelectron spectroscopy (XPS). The interfacial friction measurements have been carried out on polymer-coated substrates with bare or polymer-coated, microsphere-attached tips in over a range of solution conditions. It was found that the adsorption of polymer on oxides strikingly reduced the interfacial friction, resulting in ultra-low friction under certain conditions. By using a series of PLL-g-PEG polymers differing from each other in PEG side-chain length and grafting ratio, we observed that frictional properties of polymer-coated interfaces strongly depend on the architecture of PLL-g-PEG. Polymer-film formation and the influence of polymer architecture will be reviewed while the role of solvent and manifestation of ultra-low friction will be discussed in detail.

Self-Organization of Polymer Brush Layers in a Poor Solvent

NASA Astrophysics Data System (ADS)

Karim, A.; Tsukruk, V. V.; Douglas, J. F.; Satija, S. K.; Fetters, L. J.; Reneker, D. H.; Foster, M. D.

1995-10-01

Synthesis of densely grafted polymer brushes from good solvent polymer solutions is difficult when the surface interaction is only weakly attractive because of the strong steric repulsion between the polymer chains. To circumvent this difficulty we graft polymer layers in a poor solvent to exploit attractive polymer-polymer interactions which largely nullify the repulsive steric interactions. This simple strategy gives rise to densely grafted and homogeneous polymer brush layers. Model end-grafted polystyrene chains (M_w = 105,000) are prepared in the poor solvent cyclohexane (9.5 °C) where the chains are chemically attached to the surface utilizing a trichlorosilane end-group. Polished silicon wafers were then exposed to the reactive polymer solutions for a series of “induction times” tau_I and the evolving layer was characterized by X-ray reflectivity and atomic force microscopy. Distinct morphologies were found depending on tau_I. For short tau_I, corresponding to a grafting density less than 5 mg/m^2, the grafted layer forms an inhomogeneous island-like structure. At intermediate tau_I, where the coverage becomes percolating, a surface pattern develops which appears similar to spinodal decomposition in bulk solution. Finally, after sufficiently long tau_I, a dense and nearly homogeneous layer with a sharp interface is formed which does not exhibit surface pattern formation. The stages of brush growth are discussed qualitatively in terms of a random deposition model.

Size-dependent penetrant diffusion in polymer glasses.

PubMed

Meng, Dong; Zhang, Kai; Kumar, Sanat K

2018-05-18

Molecular Dynamics simulations are used to understand the underpinning basis of the transport of gas-like solutes in deeply quenched polymeric glasses. As found in previous work, small solutes, with sizes smaller than 0.15 times the chain monomer size, move as might be expected in a medium with large pores. In contrast, the motion of larger solutes is activated and is strongly facilitated by matrix motion. In particular, solute motion is coupled to the local elastic fluctuations of the matrix as characterized by the Debye-Waller factor. While similar ideas have been previously proposed for the viscosity of supercooled liquids above their glass transition, to our knowledge, this is the first illustration of this concept in the context of solute mass transport in deeply quenched polymer glasses.

Solution-based single molecule imaging of surface-immobilized conjugated polymers.

PubMed

Dalgarno, Paul A; Traina, Christopher A; Penedo, J Carlos; Bazan, Guillermo C; Samuel, Ifor D W

2013-05-15

The photophysical behavior of conjugated polymers used in modern optoelectronic devices is strongly influenced by their structural dynamics and conformational heterogeneity, both of which are dependent on solvent properties. Single molecule studies of these polymer systems embedded in a host matrix have proven to be very powerful to investigate the fundamental fluorescent properties. However, such studies lack the possibility of examining the relationship between conformational dynamics and photophysical response in solution, which is the phase from which films for devices are deposited. By developing a synthetic strategy to incorporate a biotin moiety as a surface attachment point at one end of a polyalkylthiophene, we immobilize it, enabling us to make the first single molecule fluorescence measurements of conjugated polymers for long periods of time in solution. We identify fluctuation patterns in the fluorescence signal that can be rationalized in terms of photobleaching and stochastic transitions to reversible dark states. Moreover, by using the advantages of solution-based imaging, we demonstrate that the addition of oxygen scavengers improves optical stability by significantly decreasing the photobleaching rates.

Threshold-like complexation of conjugated polymers with small molecule acceptors in solution within the neighbor-effect model.

PubMed

Sosorev, Andrey Yu; Parashchuk, Olga D; Zapunidi, Sergey A; Kashtanov, Grigoriy S; Golovnin, Ilya V; Kommanaboyina, Srikanth; Perepichka, Igor F; Paraschuk, Dmitry Yu

2016-02-14

In some donor-acceptor blends based on conjugated polymers, a pronounced charge-transfer complex (CTC) forms in the electronic ground state. In contrast to small-molecule donor-acceptor blends, the CTC concentration in polymer:acceptor solution can increase with the acceptor content in a threshold-like way. This threshold-like behavior was earlier attributed to the neighbor effect (NE) in the polymer complexation, i.e., next CTCs are preferentially formed near the existing ones; however, the NE origin is unknown. To address the factors affecting the NE, we record the optical absorption data for blends of the most studied conjugated polymers, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene) (P3HT), with electron acceptors of fluorene series, 1,8-dinitro-9,10-antraquinone (), and 7,7,8,8-tetracyanoquinodimethane () in different solvents, and then analyze the data within the NE model. We have found that the NE depends on the polymer and acceptor molecular skeletons and solvent, while it does not depend on the acceptor electron affinity and polymer concentration. We conclude that the NE operates within a single macromolecule and stems from planarization of the polymer chain involved in the CTC with an acceptor molecule; as a result, the probability of further complexation with the next acceptor molecules at the adjacent repeat units increases. The steric and electronic microscopic mechanisms of NE are discussed.

Hydrogel films and coatings by swelling-induced gelation

PubMed Central

Moreau, David; Chauvet, Caroline; Etienne, François; Rannou, François P.

2016-01-01

Hydrogel films used as membranes or coatings are essential components of devices interfaced with biological systems. Their design is greatly challenged by the need to find mild synthesis and processing conditions that preserve their biocompatibility and the integrity of encapsulated compounds. Here, we report an approach to produce hydrogel films spontaneously in aqueous polymer solutions. This method uses the solvent depletion created at the surface of swelling polymer substrates to induce the gelation of a thin layer of polymer solution. Using a biocompatible polymer that self-assembles at high concentration [poly(vinyl alcohol)], hydrogel films were produced within minutes to hours with thicknesses ranging from tens to hundreds of micrometers. A simple model and numerical simulations of mass transport during swelling capture the experiments and predict how film growth depends on the solution composition, substrate geometry, and swelling properties. The versatility of the approach was verified with a variety of swelling substrates and hydrogel-forming solutions. We also demonstrate the potential of this technique by incorporating other solutes such as inorganic particles to fabricate ceramic-hydrogel coatings for bone anchoring and cells to fabricate cell-laden membranes for cell culture or tissue engineering. PMID:27821765

Poly(styrene-co-butadiene) random copolymer thin films and nanostructures on a mica surface: morphology and contact angles of nanodroplets.

PubMed

McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios

2017-09-20

The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.

Tuning the critical solution temperature of polymers by copolymerization

NASA Astrophysics Data System (ADS)

Schulz, Bernhard; Chudoba, Richard; Heyda, Jan; Dzubiella, Joachim

2015-12-01

We study statistical copolymerization effects on the upper critical solution temperature (CST) of generic homopolymers by means of coarse-grained Langevin dynamics computer simulations and mean-field theory. Our systematic investigation reveals that the CST can change monotonically or non-monotonically with copolymerization, as observed in experimental studies, depending on the degree of non-additivity of the monomer (A-B) cross-interactions. The simulation findings are confirmed and qualitatively explained by a combination of a two-component Flory-de Gennes model for polymer collapse and a simple thermodynamic expansion approach. Our findings provide some rationale behind the effects of copolymerization and may be helpful for tuning CST behavior of polymers in soft material design.

Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

DOE PAGES

Pace, Natalie A.; Zhang, Weimin; Arias, Dylan H.; ...

2017-11-30

The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. We investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side-chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically and is strongly dependent on side-chain identity. These results show that it may be necessary to carefullymore » engineer the solid-state microstructure of these 'singlet fission polymers' to produce the long-lived triplets needed to realize efficient photovoltaic devices.« less

Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, Natalie A.; Zhang, Weimin; Arias, Dylan H.

The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. We investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side-chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically and is strongly dependent on side-chain identity. These results show that it may be necessary to carefullymore » engineer the solid-state microstructure of these 'singlet fission polymers' to produce the long-lived triplets needed to realize efficient photovoltaic devices.« less

Subtle charge balance controls surface-nucleated self-assembly of designed biopolymers.

PubMed

Charbonneau, Céline; Kleijn, J Mieke; Cohen Stuart, Martien A

2014-03-25

We report the surface-nucleated self-assembly into fibrils of a biosynthetic amino acid polymer synthesized by the yeast Pichia pastoris. This polymer has a block-like architecture, with a central silk-like block labeled SH, responsible for the self-assembly into fibrils, and two collagen-like random coil end blocks (C) that colloidally stabilize the fibers in aqueous solution. The silk-like block contains histidine residues (pKa≈6) that are positively charged in the low pH region, which hinders self-assembly. In aqueous solution, CSHC self-assembles into fibers above a pH-dependent critical nucleation concentration Ccb. Below Ccb, where no self-assembly occurs in solution, fibril formation can be induced by a negatively charged surface (silica) in the pH range of 3.5-7. The density of the fibers at the surface and their length are controlled by a subtle balance in charge between the protein polymer and the silica surface, which is evidenced from the dependence on pH. With increasing number density of the fibers at the surface, their average length decreases. The results can be explained on the basis of a nucleation-and-growth mechanism: the surface density of fibers depends on the rate of nucleation, while their growth rate is limited by transport of proteins from solution. Screening of the charges on the surface and histidine units by adding NaCl influences the nucleation-and-growth process in a complicated fashion: at low pH, the growth is improved, while at high pH, the nucleation is limited. Under conditions where nucleation in the bulk solution is not possible, growth of the surface-nucleated fibers into the solution--away from the surface--can still occur.

Pair interactions in polyelectrolyte-nanoparticle systems: Influence of dielectric inhomogeneities and the partial dissociation of polymers and nanoparticles.

PubMed

Pryamitsyn, Victor; Ganesan, Venkat

2015-10-28

We study the effective pair interactions between two charged spherical particles in polyelectrolyte solutions using polymer self-consistent field theory. In a recent study [V. Pryamitsyn and V. Ganesan, Macromolecules 47, 6095 (2015)], we considered a model in which the particles possess fixed charge density, the polymers contain a prespecified amount of dissociated charges and, the dielectric constant of the solution was assumed to be homogeneous in space and independent of the polymer concentration. In this article, we present results extending our earlier model to study situations in which either or both the particle and the polymers possess partially dissociable groups. Additionally, we also consider the case when the dielectric constant of the solution depends on the local concentration of the polymers and when the particle's dielectric constant is lower than that of the solvent. For each case, we quantify the polymer-mediated interactions between the particles as a function of the polymer concentrations and the degree of dissociation of the polymer and particles. Consistent with the results of our previous study, we observe that the polymer-mediated interparticle interactions consist of a short-range attraction and a long-range repulsion. The partial dissociablity of the polymer and particles was seen to have a strong influence on the strength of the repulsive portion of the interactions. Rendering the dielectric permittivity to be inhomogeneous has an even stronger effect on the repulsive interactions and results in changes to the qualitative nature of interactions in some parametric ranges.

Polymer Inverse Temperature-Dependent Solubility: A Visual Demonstration of the Importance of "T[Delta]S" in the Gibbs Equation

ERIC Educational Resources Information Center

Bergbreiter, David E.; Mijalis, Alexander J.; Fu, Hui

2012-01-01

Reversible polymer dehydration and precipitation from water due to the unfavorable entropy of hydration is examined using a melting-point apparatus. The thermoresponsive lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) is responsible for these effects. An experiment is described that allows students to…

Reexamination of the Classical View of how Drag-Reducing Polymer Solutions Modify the Mean Velocity Profile: Baseline Results

NASA Astrophysics Data System (ADS)

Farsiani, Yasaman; Baade, Jacquelyne; Elbing, Brian

2016-11-01

Recent numerical and experimental data have shown that the classical view of how drag-reducing polymer solutions modify the mean turbulent velocity profile is incorrect. The classical view is that the log-region is unmodified from the traditional law-of-the-wall for Newtonian fluids, though shifted outward. Thus the current study reexamines the modified velocity distribution and its dependence on flow and polymer properties. Based on previous work it is expected that the behavior will depend on the Reynolds number, Weissenberg number, ratio of solvent viscosity to the zero-shear viscosity, and the ratio between the coiled and fully extended polymer chain lengths. The long-term objective for this study includes a parametric study to assess the velocity profile sensitivity to each of these parameters. This study will be performed using a custom design water tunnel, which has a test section that is 1 m long with a 15.2 cm square cross section and a nominal speed range of 1 to 10 m/s. The current presentation focuses on baseline (non-polymeric) measurements of the velocity distribution using PIV, which will be used for comparison of the polymer modified results. Preliminary polymeric results will also be presented. This work was supported by NSF Grant 1604978.

Tunable thermoresponsive pyrrolidone-based polymers from pyroglutamic acid, a bio-derived resource.

PubMed

Bhat, Rajani; Pietrangelo, Agostino

2013-03-12

A series of pyrrolidone-based polymers is prepared from pyroglutamic acid, a bio-derived resource. Polymers bearing simple alkoxy substituents (e.g., methoxy, ethoxy, and butoxy) are soluble in common organic solvents and possess glass transition temperatures that are dependent on the length of the alkoxy residue. Replacing these substituents with an ether moiety (CH3 OCH2 CH2 O-) affords a highly sensitive and reversible thermoresponsive polymer with a lower critical solution temperature (LCST) of 42 °C in water. Copolymers composed of repeat units bearing both the ether and simple alkoxy residues are found to exhibit LCSTs that are highly dependent on the nature of the hydrophobic alkoxy residue suggesting that the LCSTs of these polymers can be successfully tuned by simply tailoring the copolymer structure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthetic vascular graft fabrication by a precipitation-flotation method.

PubMed

Kowligi, R R; von Maltzahn, W W; Eberhart, R C

1988-01-01

The authors report a new technique for fabricating synthetic vascular grafts. It involves spraying a polymer solution (generated by mixing polymer solution and nitrogen gas in a spray nozzle) onto the surface of a flowing nonsolvent liquid (water): polymer fibers form during precipitation of the spray drops as they travel on the water surface, until picked up by a partially submerged rotating mandrel. Depending on process conditions, these fibers may aggregate to form a continuous layer or remain separated until they are picked up. A number of independent process variables allow control of characteristics of the conduits: gas and polymer solution feed rates, nozzle traverse speed, nonsolvent (water) flow rate, spray-mandrel spacing, and mandrel rpm. The SEM reveals that the graft wall consists of numerous fused polymeric fibers arrayed in both the circumferential and axial directions. The inner surface resembles a mesh of closely spaced fused fibers. The conduits have walls with interconnected pores (water permeabilities between 0.05 to 7.0 ml/min-cm2); nonporous surfaces also can be made. Tensile stress of the grafts at failure (in radial direction) varied between 0.05 to 2.3 MPa, whereas elongation at break ranged between 150 to 600%, depending on the porosity and fabrication conditions. A major advantage of this technique is its ability to produce grafts of a wide variety of fiber sizes and fusion characteristics in an inexpensive, safe, and reliable fashion.

Viscometric and misting properties of polymer-modified fuel

NASA Technical Reports Server (NTRS)

Grens, E. A., II; Williams, M. C.

1982-01-01

Solutions of polyisobutylenes L160, L200, B200, and B230 in Jet-A were prepared at concentrations up to 3000 ppm. These polymers have molecular weights in the range 5 to 9 x 1,00,000 and have previously been shown to induce anti-misting properties in Jet-A. In connection with the pumpability of such solutions, especially at low temperatures, the shear viscosity, eta, of these solutions was measured at temperatures 25 C, 0 C, and -25 C. Concentration-dependence of eta was very similar for all four polymer solutes, the increase of eta(c) at 3000 ppm being roughly four-fold (relative to Jet-A) for the L-series and five-fold for the B-series. This behavior prevailed at all temperatures, and there was no evidence of phase separation or other chemical instability at -25 C at any concentration. In the more practical c-range for anti-misting applications, say within 1000 ppm, the increase of eta(c) was only twofold.

Magnetic Alignment of γ-Fe2O3 Nanoparticles in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Jimenez, Andrew; Kumar, Sanat K.; Jestin, Jacques

Recent work in nanocomposites has been heavily focused on controlling the dispersion state of filler particles. The use of internal self-assembly based on matrix properties provides a limited solution to the desire for specified organizations. By introducing a magnetic field during the casting of a polymer solution it has been shown that particles can be oriented to form anisotropic structures - commonly sought after for improved mechanical properties. Here, magnetic nanoparticles were cast in two different polymer matrices to study the effect of various forces that lead to this highly desired alignment. The addition of the magnetic field as an external trigger was shown to not necessarily force the clustering, but rather orient the agglomerates already available in solution. This demonstrates the importance of other dominant forces introduced into the system by characteristics of the polymers themselves. While this magnetic field provides a direction for the sample, the key forces lie in the interactions between the polymers and nanoparticles (as well as their solvent). The study shows a dependence of anisotropy on the particle loading, matrix, and casting time, from which continued work hopes to quantify the clustering necessary to optimize alignment in the composite.

Vertical Phase Segregation Induced by Dipolar Interactions in Planar Polymer Brushes

DOE PAGES

Mahalik, Jyoti P.; Sumpter, Bobby G.; Kumar, Rajeev

2016-09-13

In this paper, we present a generalized theory for studying structural properties of a planar dipolar polymer brush immersed in a polar solvent. We show that an explicit treatment of the dipolar interactions yields a macroscopic concentration dependent effective “chi” (the Flory–Huggins-like interaction) parameter. Furthermore, it is shown that the concentration dependent chi parameter promotes phase segregation in polymer solutions and brushes so that the polymer-poor phase consists of a finite/nonzero polymer concentration. Such a destabilization of the homogeneous phase by the dipolar interactions appears as vertical phase segregation in a planar polymer brush. In a vertically phase segregated polymermore » brush, the polymer-rich phase near the grafting surface coexists with the polymer-poor phase at the other end. Predictions of the theory are directly compared with prior reported experimental results for dipolar polymers in polar solvents. Excellent agreements with the experimental results are found, hinting that the dipolar interactions play a significant role in vertical phase segregation of planar polymer brushes. We also compare our field theoretical approach with the two-state and other models invoking ad hoc concentration dependence of the chi parameter. Interplay between the short-ranged excluded volume interactions and long-ranged dipolar interactions is shown to play an important role in affecting the vertical phase separation. Finally, effects of mismatch between the dipole moments of the polymer segments and the solvent molecules are investigated in detail.« less

A study of normoxic polymer gel using monomer 2-hydroxyethyl methacrylate (HEMA)

NASA Astrophysics Data System (ADS)

Ishak, Siti Atiqah; Mustafa, Iskandar Shahrim; Rahman, Azhar Abdul; Moktar, Mohd; Min, Ung Ngie

2015-04-01

The aim of this study is to determine the sensitivity of HEMA-polymer gel mixture consist of monomer 2-hydroxyethyl methacrylate (HEMA) with different types of composition. Several composition of HEMA-polymer gel were fabricated and the gels were irradiated with radiation dose between 10 cGy to 100cGy by using x-ray machine and 100 cGy to 1400 cGy by using 6 MV photon beam energy of linear accelerator. The degree of polymerization was evaluated by using magnetic resonance imaging (MRI) with dependence of R2-dose response. Polymer gel consists of cross-linker, anti-oxidant Tetrakis(Hydroxymethyl)phosphonium chloride solution (THPC) and oxygen scavenger hydroquinone shows a stable sensitivity with highest dose dependency. Besides, the results shows the stage polymerization consist of induction, propagation, termination, and chain transfer were dependence with type of chemical mixture and radiation dose. Thus, normoxic HEMA-polymer gel with the different gel formulations can have a better dose resolution and an appropriate recipe must be selected to increase of the sensitivity required and the stability of the dosimeter.

A study of normoxic polymer gel using monomer 2-hydroxyethyl methacrylate (HEMA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishak, Siti Atiqah; Mustafa, Iskandar Shahrim; Rahman, Azhar Abdul

2015-04-24

The aim of this study is to determine the sensitivity of HEMA-polymer gel mixture consist of monomer 2-hydroxyethyl methacrylate (HEMA) with different types of composition. Several composition of HEMA-polymer gel were fabricated and the gels were irradiated with radiation dose between 10 cGy to 100cGy by using x-ray machine and 100 cGy to 1400 cGy by using 6 MV photon beam energy of linear accelerator. The degree of polymerization was evaluated by using magnetic resonance imaging (MRI) with dependence of R2-dose response. Polymer gel consists of cross-linker, anti-oxidant Tetrakis(Hydroxymethyl)phosphonium chloride solution (THPC) and oxygen scavenger hydroquinone shows a stable sensitivitymore » with highest dose dependency. Besides, the results shows the stage polymerization consist of induction, propagation, termination, and chain transfer were dependence with type of chemical mixture and radiation dose. Thus, normoxic HEMA-polymer gel with the different gel formulations can have a better dose resolution and an appropriate recipe must be selected to increase of the sensitivity required and the stability of the dosimeter.« less

Chemistry and adhesive properties of poly(arylene ether)s containing heterocyclic units

NASA Technical Reports Server (NTRS)

Connell, John W.

1991-01-01

Novel poly(arylene ether)s containing heterocyclic units were prepared, characterized, and evaluated as adhesives and composite matrices. The polymers were prepared by reacting a heterocyclic bisphenol with an activated aromatic dihalide in a polar aprotic solvent, using potassium carbonate. The polymerizations were generally carried out in N,N-dimethylacetamide at 155 C. In some cases, where the polymers were semicrystalline, higher temperatures and thus higher boiling solvents were necessary to keep the polymers in solution. Heterocyclic rings incorporated into the poly(arylene ether) backbone include phenylquinoxaline, phenylimidazole, benzimidazole, benzoxazole, 1,3,4-oxadiazole, and 1,2,4-triazole. The polymers were characterized by differential scanning calorimetry, solution viscosity, X-ray diffraction, thin film, and adhesive and (in some cases) composite properties. The glass transition temperatures, crystalline melt temperature, solubility, and mechanical properties varied depending upon the heterocyclic ring. The chemistry and properties of these materials are discussed.

Removal of phenol from aqueous solution using polymer inclusion membrane based on mixture of CTA and CA

NASA Astrophysics Data System (ADS)

Benosmane, Nadjib; Boutemeur, Baya; Hamdi, Safouane M.; Hamdi, Maamar

2018-03-01

Nowadays, there are increasingly stringent regulations requiring more and more treatment of industrial effluents to generate product waters which could be easily reused or disposed of to the environment without any harmful effects. In the present work, the removal of phenol from aqueous solution across polymer inclusion membrane (PIM), based on mixture of cellulose triacetate and cellulose acetate as support (75/25%), calix[4]resorcinarene derivative as a carrier and 2-nitrophenyl octyl ether (2-NPOE) as plasticizer was investigated. The experimental part of this investigation involved the influence of carrier nature, plasticizer concentration, pH phases, and phenol initial concentration on the removal efficiency of phenol from synthetic wastewater. A PIM containing 0.1 g (of mixture polymer), (0.15 g/g mixture of polymer) of carrier and (0.03 ml/g mixture of polymer) of 2-NPOE provided the highest percentage of phenol removal efficiency over a 6-day transport; the removal was found to be about 95%, indeed the removal was found to be highly dependent of pH phases. The feed solution in these transport experiments was at pH 2, while the stripping solution contained 0.20 M NaOH. This study claims that the PIM with a mixture of cellulose derivatives can be used effectively to remove phenols from wastewaters.

Protein-Style Dynamical Transition in a Non-Biological Polymer and a Non-Aqueous Solvent.

PubMed

Mamontov, E; Sharma, V K; Borreguero, J M; Tyagi, M

2016-03-31

Temperature-dependent onset of apparent anharmonicity in the microscopic dynamics of hydrated proteins and other biomolecules has been known as protein dynamical transition for the last quarter of a century. Using neutron scattering and molecular dynamics simulation, techniques most often associated with protein dynamical transition studies, we have investigated the microscopic dynamics of one of the most common polymers, polystyrene, which was exposed to toluene vapor, mimicking the process of protein hydration from water vapor. Polystyrene with adsorbed toluene is an example of a solvent-solute system, which, unlike biopolymers, is anhydrous and lacks hydrogen bonding. Nevertheless, it exhibits the essential traits of the dynamical transition in biomolecules, such as a specific dependence of the microscopic dynamics of both solvent and host on the temperature and the amount of solvent adsorbed. We conclude that the protein dynamical transition is a manifestation of a universal solvent-solute dynamical relationship, which is not specific to either biomolecules as solute, or aqueous media as solvent, or even a particular type of interactions between solvent and solute.

Dynamics of nanoparticles in complex fluids

NASA Astrophysics Data System (ADS)

Omari, Rami A.

Soft matter is a subfield of condensed matter including polymers, colloidal dispersions, surfactants, and liquid crystals. These materials are familiar from our everyday life- glues, paints, soaps, and plastics are examples of soft materials. Many phenomena in these systems have the same underlying physical mechanics. Moreover, it has been recognized that combinations of these systems, like for example polymers and colloids, exhibit new properties which are not found in each system separately. These mixed systems have a higher degree of complexity than the separate systems. In order to understand their behavior, knowledge from each subfields of soft matter has to be put together. One of these complex systems is the mixture of nanoparticles with macromolecules such as polymers, proteins, etc. Understanding the interactions in these systems is essential for solving various problems in technological and medical fields, such as developing high performance polymeric materials, chromatography, and drug delivery vehicles. The author of this dissertation investigates fundemental soft matter systems, including colloid dispersions in polymer solutions and binary mixture. The diffusion of gold nanoparticles in semidilute and entangled solutions of polystyrene (PS) in toluene were studied using fluorescence correlation spectroscopy (FCS). In our experiments, the particle radius (R ≈ 2.5 nm) was much smaller compared to the radius of gyration of the chain but comparable to the average mesh size of the fluctuating polymer network. The diffusion coefficient (D) of the particles decreased monotonically with polymer concentration and it can be fitted with a stretched exponential function. At high concentration of the polymer, a clear subdiffusive motion of the particles was observed. The results were compared with the diffusion of free dyes, which showed normal diffusive behavior for all concentrations. In another polymer solution, poly ethylene glycol (PEG) in water, the diffusion of the gold nanoparticles depends on the dimentionless length scale R/zeta, where R is the radius of the nanoparticle and zeta is the average mesh size of the fluctuating polymer network. FCS were used to study the critical adsorption on curved surfaces by utilizing spherical nanoparticles immersed in a critical binary liquid mixture of 2,6 lutidine + water. The temperature dependence of the adsorbed film thickness and excess adsorption was determined from FCS measurements of the enlarged effective hydrodynamic radius of the particles. Our results indicated that the adsorbed film thickness is of the order of correlation length associated with concentration fluctuations. The excess adsorption per unit area increases following a power law in reduced temperature with an exponent of -1, which is the mean-field value for the bulk susceptibility exponent. The kinetics of adsorption of gold nanoparticles in polymer solutions on silicon substrate was studied using ellipsometry by measuring the thickness of the adsorbed layer versus time. The data showed an exponential growth with relaxation time constants, which is proportional to the diffusion of the gold nanoparticles in polymer solution.

NMR (Nuclear Magnetic Resonance) and macromolecular migration in a melt or in concentrated solutions

NASA Technical Reports Server (NTRS)

Addad, J. P. C.

1983-01-01

The purpose of this paper is to analyze the migration process of long polymer molecules in a melt or in concentrated solutions as it may be observed from the dynamics of the transverse magnetization of nuclear spins linked to these chains. The low frequency viscoelastic relaxation of polymer systems is known to be mainly controlled by the mechanism of dissociation of topological constraints excited on chains and which are called entanglements. This mechanism exhibits a strong dependence upon the chain molecular weight. These topological constraints also govern the diffusion process of polymer chains. So, the accurate description of the diffusion motion of a chain may be a convenient way to characterize disentanglement processes necessarily involved in any model proposed to explain viscoelastic effects.

Suppression of the Saffman-Taylor instability through injection of a finite slug of polymer

NASA Astrophysics Data System (ADS)

Beeson-Jones, Timothy H.; Woods, Andrew W.

2014-11-01

During secondary oil recovery, relatively mobile water can channel through oil owing to the Saffman-Taylor instability. Injection of a finite slug of polymer solution from a central well prior to the water flood suppresses the growth of the instability by reducing the adverse mobility ratio at the leading interface. A linear stability analysis of an axisymmetric base state identifies how perturbations on the leading and trailing interfaces become coupled. It also reveals the dependence of the long-time algebraic growth of each mode on the mobility ratios across the two interfaces. The viscosity of the polymer solution which minimizes the growth rate of the instability is identified, and the impact of different slug sizes on this growth is described. Funded by EPSRC & BP.

Thermal casting process for the preparation of anisotropic membranes and the resultant membrane

DOEpatents

Caneba, Gerard T. M.; Soong, David S.

1987-01-01

A method for providing anisotropic polymer membranes from a binary polymer/solvent solution using a thermal inversion process. A homogeneous binary solution is cast onto a support and cooled in such a way as to provide a differential in cooling rate across the thickness of the resulting membrane sheet. Isotropic or anisotropic structures of selected porosities can be produced, depending on the initial concentration of polymer in the selected solvent and on the extent of the differential in cooling rate. This differential results in a corresponding gradation in pore size. The method may be modified to provide a working skin by applying a rapid, high-temperature pulse to redissolve a predetermined thickness of the membrane at one of its faces and then freezing the entire structure.

Thermal casting process for the preparation of membranes

DOEpatents

Caneba, G.T.M.; Soong, D.S.

1985-07-10

Disclosed is a method for providing anisotropic polymer membrane from a binary polymer/solvent solution using a thermal inversion process. A homogeneous binary solution is cast onto a support and cooled in such a way as to provide a differential in cooling rate across the thickness of the resulting membrane sheet. Isotropic or anisotropic structures of selected porosities can be produced, depending on the initial concentration of polymer in the selected solvent and on the extent of the differential in cooling rate. This differential results in a corresponding gradation in pore size. The method may be modified to provide a working skin by applying a rapid, high-temperature pulse to redissolve a predetermined thickness of the membrane at one of its faces and then freezing the entire structure.

Conformational and Structural Properties of High Functionality Dendrimer-like Star Polymers Synthesized from Living Polymerization Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pople, John A

2001-03-22

The design, synthesis and solution properties of dendritic-linear hybrid macromolecules is described. The synthetic strategy employs living ring-opening polymerization in combination with selective and quantitative organic transformations for the preparation of new molecular architectures similar to classical star polymers and dendrimers. The polymers were constructed from high molecular weight poly(e-caprolactone) initiated from the surface hydroxyl groups of dendrimers derived from bis(hydroxymethyl) propionic acid (bis-MPA) in the presence of stannous 2-ethyl hexanoate (Sn(Oct)2). In this way, star and hyperstar poly(e-caprolactones) were elaborated depending on the generation of dendrimer employed. The ROP from these hydroxy groups was found to be a facilemore » process leading to controlled molecular weight, low dispersity products (Mw/Mn) < 1.15. In addition to the use of dendrimers as building blocks to star polymers, functional dendrons derived from bis-MPA were attached to chain ends of the star polymers, yielding structures that closely resemble that of the most advanced dendrimers. Measurements of the solution properties (hydrodynamic volume vs. molecular weight) on the dendritic-linear hybrids show a deviation from linearity, with a lower than expected hydrodynamic volume, analogous to the solution properties of dendrimers of high generation number. The onset of the deviation begins with the polymers initiated from the second generation dendrimer of bis-MPA and becomes more exaggerated with the higher generations. It was found that polymerization amplifies the nonlinear solution behavior of dendrimers. Small angle neutron scattering (SANS) measurements revealed that the radius of gyration scaled with arm functionality (f) as f 2/3, in accordance with the Daoud-Cotton model for many arm star polymer.« less

Klucel™ EF and ELF polymers for immediate-release oral dosage forms prepared by melt extrusion technology.

PubMed

Mohammed, Noorullah Naqvi; Majumdar, Soumyajit; Singh, Abhilasha; Deng, Weibin; Murthy, Narasimha S; Pinto, Elanor; Tewari, Divya; Durig, Thomas; Repka, Michael A

2012-12-01

The objective of this research work was to evaluate Klucel™ hydroxypropylcellulose (HPC) EF and ELF polymers, for solubility enhancement as well as to address some of the disadvantages associated with solid dispersions. Ketoprofen (KPR), a Biopharmaceutics Classification System class II drug with poor solubility, was utilized as a model compound. Preliminary thermal studies were performed to confirm formation of a solid solution/dispersion of KPR in HPC matrix and also to establish processing conditions for hot-melt extrusion. Extrudates pelletized and filled into capsules exhibited a carrier-dependent release with ELF polymer exhibiting a faster release. Tablets compressed from milled extrudates exhibited rapid release owing to the increased surface area of the milled extrudate. Addition of mannitol (MNT) further enhanced the release by forming micro-pores and increasing the porosity of the extrudates. An optimized tablet formulation constituting KPR, MNT, and ELF in a 1:1:1 ratio exhibited 90% release in 15 min similar to a commercial capsule formulation. HPC polymers are non-ionic hydrophilic polymers that undergo polymer-chain-length-dependent solubilization and can be used to enhance solubility or dissolution rate of poorly soluble drugs. Dissolution/release rate could be tailored for rapid-release applications by selecting a suitable HPC polymer and altering the final dosage form. The release obtained from pellets was carrier-dependent and not drug-dependent, and hence, such a system can be effectively utilized to address solubility or precipitation issues with poorly soluble drugs in the gastrointestinal environment.

Fluorescence turn-on responses of anionic and cationic conjugated polymers toward proteins: effect of electrostatic and hydrophobic interactions.

PubMed

Pu, Kan-Yi; Liu, Bin

2010-03-11

Cationic and anionic poly(fluorenyleneethynylene-alt-benzothiadiazole)s (PFEBTs) are designed and synthesized via Sonagashira coupling reaction to show light-up signatures toward proteins. Due to the charge transfer character of the excited states, the fluorescence of PFEBTs is very weak in aqueous solution, while their yellow fluorescence can be enhanced by polymer aggregation. PFEBTs show fluorescence turn-on rather than fluorescence quenching upon complexation with proteins. Both electrostatic and hydrophobic interactions between PFEBTs and proteins are found to improve the polymer fluorescence, the extent of which is dependent on the nature of the polymer and the protein. Changes in solution pH adjust the net charges of proteins, providing an effective way to manipulate electrostatic interactions and in turn the increment in the polymer fluorescence. In addition, the effect of protein digestion on the fluorescence of polymer/protein complexes is probed. The results indicate that electrostatic interaction induced polymer fluorescence increase cannot be substantially reduced through cleaving protein into peptide fragments. In contrast, hydrophobic interactions, mainly determined by the hydrophobicity of proteins, can be minimized by digestion, imparting a light-off signature for the polymer/protein complexes. This study thus not only highlights the opportunities of exerting nonspecific interactions for protein sensing but also reveals significant implications for biosensor design.

Self-consistent field theory of polymer-ionic molecule complexation.

PubMed

Nakamura, Issei; Shi, An-Chang

2010-05-21

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C(i) ((a))(kDelta)(=0 or 1), whose average determines the number of adsorbed molecules, n(BI). Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for n(BI) are obtained, depending on the equilibrium constant of single-ion binding. Spinodal lines calculated from the mean-field free energy exhibit closed-loop regions where the homogeneous phase becomes unstable. This phase instability is driven by the excluded-volume interaction due to the single occupancy of ion-binding sites on the polymers. Moreover, sol-gel transitions are examined using a critical degree of conversion. A gel phase is induced when the concentration of adsorbates is increased. At a higher concentration of the adsorbates, however, a re-entrance from a gel phase into a sol phase arises from the correlation between unoccupied and occupied ion-binding sites. The theory is applied to a model system, poly(vinyl alcohol) and borate ion in aqueous solution with sodium chloride. Good agreement between theory and experiment is obtained.

Multicolor Luminescence from Conjugates of Genetically Encoded Elastin-like Polymers and Terpyridine-Lanthanides

DOE PAGES

Ghosh, Koushik; Balog, Eva Rose M.; Kahn, Jennifer L.; ...

2015-08-20

Functional hybrid materials with optically active metal-ligand moieties embedded within a polymer matrix have a great potential in (bio)materials science, including applications in light-emitting diode devices. Here, we report a simple strategy to incorporate terpyridine derivatives into the side chains of elastin-like polymers (ELPs). The further binding of trivalent lanthanide ions with the terpyridine ligands generated an array of photoluminescence ranging from the visible to the near-infrared regions. Lastly, as thin films, these ELP-based optical materials also exhibited distinct morphologies that depend upon the temperature of the aqueous solutions from which the hybrid polymers were spin coated or drop cast.

The effect of the molecular orientation on the release of antimicrobial substances from uniaxially drawn polymer matrixes.

PubMed

Iconomopoulou, S M; Voyiatzis, G A

2005-03-21

A new method of controlled release of low molecular weight biocides incorporated in polymer matrixes is described. The molecular orientation of uniaxially drawn biocide doped polymer films is suggested as a significant parameter for controlled release monitoring. Triclosan, a well-established widespread antibacterial agent, has been incorporated into high density polyethylene (HDPE) films that have been subsequently uniaxially drawn at different draw ratios. The molecular orientation developed was estimated utilizing polarized mu-Raman spectra. Biocide incorporated polymer films, drawn at different draw ratios, have been immersed in ethanol-water solutions (EtOH) and in physiological saline. The release of Triclosan out of the polymer matrix was probed with UV-Vis absorption spectroscopy for a period of time up to 15 months. In all cases, although the film surface of the drawn samples exposed to the liquid solution was higher than the undrawn one, the relevant release rate from the drawn specimens was lower than the non-stretched samples depending on the molecular orientation developed during the drawing process. A note is made of the fact that no significant molecular orientation relaxation of the polyethylene films has been observed even after such a long time of immersion of the drawn films in the liquid solutions.

Hydrodynamic chromatography of macromolecules using polymer monolithic columns.

PubMed

Edam, Rob; Eeltink, Sebastiaan; Vanhoutte, Dominique J D; Kok, Wim Th; Schoenmakers, Peter J

2011-12-02

The selectivity window of size-based separations of macromolecules was tailored by tuning the macropore size of polymer monolithic columns. Monolithic materials with pore sizes ranging between 75 nm and 1.2 μm were prepared in situ in large I.D. columns. The dominant separation mechanism was hydrodynamic chromatography in the flow-through pores. The calibration curves for synthetic polymers matched with the elution behavior by HDC separations in packed columns with 'analyte-to-pore' aspect ratios (λ) up to 0.2. For large-macropore monoliths, a deviation in retention behavior was observed for small polystyrene polymers (M(r)<20 kDa), which may be explained by a combined HDC-SEC mechanism for λ<0.02. The availability of monoliths with very narrow pore sizes allowed investigation of separations at high λ values. For high-molecular weight polymers (M(r)>300,000 Da) confined in narrow channels, the separation strongly depended on flow rate. Flow-rate dependent elution behavior was evaluated by calculation of Deborah numbers and confirmed to be outside the scope of classic shear deformation or slalom chromatography. Shear-induced forces acting on the periphery of coiled polymers in solution may be responsible for flow-rate dependent elution. Copyright © 2011 Elsevier B.V. All rights reserved.

Aggregation of flexible polyelectrolytes: Phase diagram and dynamics.

PubMed

Tom, Anvy Moly; Rajesh, R; Vemparala, Satyavani

2017-10-14

Similarly charged polymers in solution, known as polyelectrolytes, are known to form aggregated structures in the presence of oppositely charged counterions. Understanding the dependence of the equilibrium phases and the dynamics of the process of aggregation on parameters such as backbone flexibility and charge density of such polymers is crucial for insights into various biological processes which involve biological polyelectrolytes such as protein, DNA, etc. Here, we use large-scale coarse-grained molecular dynamics simulations to obtain the phase diagram of the aggregated structures of flexible charged polymers and characterize the morphology of the aggregates as well as the aggregation dynamics, in the presence of trivalent counterions. Three different phases are observed depending on the charge density: no aggregation, a finite bundle phase where multiple small aggregates coexist with a large aggregate and a fully phase separated phase. We show that the flexibility of the polymer backbone causes strong entanglement between charged polymers leading to additional time scales in the aggregation process. Such slowing down of the aggregation dynamics results in the exponent, characterizing the power law decay of the number of aggregates with time, to be dependent on the charge density of the polymers. These results are contrary to those obtained for rigid polyelectrolytes, emphasizing the role of backbone flexibility.

Programmable Payload Release from Transient Polymer Microcapsules Triggered by a Specific Ion Coactivation Effect.

PubMed

Tang, Shijia; Tang, Liuyan; Lu, Xiaocun; Liu, Huiying; Moore, Jeffrey S

2018-01-10

Stimuli-responsive materials activated by a pair of molecular or ionic species are of interest in the design of chemical logic gates and signal amplification schemes. There are relatively few materials whose coactivated response has been well-characterized. Here, we demonstrate a specific ion coactivation (SICA) effect at the interfaces of transient polymer solids and liquid solutions. We found that depolymerization of the transient polymer, cyclic poly(phthalaldehyde) (cPPA), exhibited a SICA effect when the cPPA core-shell microcapsules were suspended in ion-containing acidic methanol solutions. Significant acceleration in cPPA depolymerization rate is triggered by the combination of acid and ion coactivators. Intriguingly, the SICA effect is related to the Hofmeister behavior. The SICA effect is primarily determined by anions, and cations exhibit a secondary effect that modulates the coactivation strength. Based on these observations, we developed cPPA programmable microcapsules whose payload release rates depend on the composition and concentration of the salt/acidic-methanol solutions.

Recognition-Mediated Hydrogel Swelling Controlled by Interaction with a Negative Thermoresponsive LCST Polymer.

PubMed

Belal, Khaled; Stoffelbach, François; Lyskawa, Joël; Fumagalli, Matthieu; Hourdet, Dominique; Marcellan, Alba; Smet, Lieselot De; de la Rosa, Victor R; Cooke, Graeme; Hoogenboom, Richard; Woisel, Patrice

2016-11-02

Most polymeric thermoresponsive hydrogels contract upon heating beyond the lower critical solution temperature (LCST) of the polymers used. Herein, we report a supramolecular hydrogel system that shows the opposite temperature dependence. When the non-thermosesponsive hydrogel NaphtGel, containing dialkoxynaphthalene guest molecules, becomes complexed with the tetra cationic macrocyclic host CBPQT 4+ , swelling occurred as a result of host-guest complex formation leading to charge repulsion between the host units, as well as an osmotic contribution of chloride counter-ions embedded in the network. The immersion of NaphtGel in a solution of poly(N-isopropylacrylamide) with tetrathiafulvalene (TTF) end groups complexed with CBPQT 4+ induced positive thermoresponsive behaviour. The LCST-induced dethreading of the polymer-based pseudorotaxane upon heating led to transfer of the CBPQT 4+ host and a concomitant swelling of NaphtGel. Subsequent cooling led to reformation of the TTF-based host-guest complexes in solution and contraction of the hydrogel. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

General solutions for the oxidation kinetics of polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillen, K.T.; Clough, R.L.; Wise, J.

1996-08-01

The simplest general kinetic schemes applicable to the oxidation of polymers are presented, discussed and analyzed in terms of the underlying kinetic assumptions. For the classic basic autoxidation scheme (BAS), which involves three bimolecular termination steps and is applicable mainly to unstabilized polymers, typical assumptions used singly or in groups include (1) long kinetic chain length, (2) a specific ratio of the termination rate constants and (3) insensitivity to the oxygen concentration (e.g., domination by a single termination step). Steady-state solutions for the rate of oxidation are given in terms of one, two, three, or four parameters, corresponding respectively tomore » three, two, one, or zero kinetic assumptions. The recently derived four-parameter solution predicts conditions yielding unusual dependencies of the oxidation rate on oxygen concentration and on initiation rate, as well as conditions leading to some unusual diffusion-limited oxidation profile shapes. For stabilized polymers, unimolecular termination schemes are typically more appropriate than bimolecular. Kinetics incorporating unimolecular termination reactions are shown to result in very simple oxidation expressions which have been experimentally verified for both radiation-initiated oxidation of an EPDM and thermoxidative degradation of nitrile and chloroprene elastomers.« less

Laser performance of Coumarin 540A dye molecules in polymeric host media with different viscosities: From liquid solution to solid polymer matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costela, A.; Garcia-Moreno, I.; Barroso, J.

1998-01-01

Photophysical parameters and lasing properties of Coumarin 540A dye molecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylate). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influence of the rigidity of the medium on the radiative processes. The photodegradation mechanisms acting on the fluorophores are analyzed by following the dependence of laser induced fluorescence and laser output on the number of pump laser pulses. The fluorescence redistribution after pattern photobleaching technique is used, and Fick{close_quote}s second law is applied tomore » study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined. {copyright} {ital 1998 American Institute of Physics.}« less

Low-Temperature Chemiluminescence From cis-1,4-Polybutadiene, 1,2-Polybutadiene, and trans-Polypentenamer at Temperatures Near Ambient

NASA Technical Reports Server (NTRS)

Nathan, Richard A.; Mendenhall, G. David; Birts, Michelle A.; Ogle, Craig A.; Golub, Morton A.

1978-01-01

The chemiluminescence emission at 25-60 C was measured from films of cis-1,4-polybutadiene, 1,2-polybutadiene, and trans-polypentenamer. The polymers were autoxidized previously in air 100 C, or allowed to react with singlet molecular oxygen in solution, and then cast into films. Values of beta(or k(sub d,((1)O2 yields (3)03)/k(sub r)((1)O2 + polymer yields products)) were determined in benzene for cis-1,4-polybutadiene and cis-1,4-polyisoprene, and for model compounds cis-3-hexene and cis-3-methyl-3-hexene by independent methods. The chemiluminescence emission from irradiated films of the polymers containing a dye sensitizer showed a complicated time dependence, and the results depended on the length of irradiation.

Space Environmentally Stable Polyimides and Copolyimides

NASA Technical Reports Server (NTRS)

Watson, Kent A.; Connell, John W.

2000-01-01

Polyimides with a unique combination of properties including low color in thin films, atomic oxygen (AO), ultra-violet (UV) radiation resistance, solubility in organic solvents in the imide form, high glass transition (T(sub g)) temperatures and high thermal stability have been prepared and characterized. The polymers were prepared by reacting a novel aromatic diamine with aromatic dianhydrides in a polar aprotic solvent. The solubility of the polymers in the imide form as well as the color density of thin films were dependent upon the chemical structure of the dianhydride. Several thin films (25-50 mm thick) prepared by solution casting of amide acid or imide solutions exhibited very low color and high optical transparency (approximately 90%) as determined by UV/visible spectroscopy. The polymers exhibited T(sub g)s >200 C depending upon the structure of the dianhydride and temperatures of 5% weight loss approximately 500C in air as determined by dynamic thermogravimetric analysis. Thin films coated with silver/inconel were exposed to a high fluence of AO and 1000 equivalent solar hours of UV radiation. The effects of these exposures on optical properties were minor. These space environmentally durable polymers are potentially useful in a variety of applications on spacecraft such as thin film membranes on antennas, second-surface mirrors, thermal/optical coatings and multi-layer thermal insulation (MLI) blanket materials. The chemistry, physical and mechanical properties of the polymers as well as their responses to AO and UV exposure will be discussed.

The effect of side-chain substitution and hot processing on diketopyrrolopyrrole-based polymers for organic solar cells.

PubMed

Heintges, Gaël H L; Leenaers, Pieter J; Janssen, René A J

2017-07-14

The effects of cold and hot processing on the performance of polymer-fullerene solar cells are investigated for diketopyrrolopyrrole (DPP) based polymers that were specifically designed and synthesized to exhibit a strong temperature-dependent aggregation in solution. The polymers, consisting of alternating DPP and oligothiophene units, are substituted with linear and second position branched alkyl side chains. For the polymer-fullerene blends that can be processed at room temperature, hot processing does not enhance the power conversion efficiencies compared to cold processing because the increased solubility at elevated temperatures results in the formation of wider polymer fibres that reduce charge generation. Instead, hot processing seems to be advantageous when cold processing is not possible due to a limited solubility at room temperature. The resulting morphologies are consistent with a nucleation-growth mechanism for polymer fibres during drying of the films.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis.

PubMed

Dereymaker, Aswin; Scurr, David J; Steer, Elisabeth D; Roberts, Clive J; Van den Mooter, Guy

2017-04-03

Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer remains amorphous after coating of the rate controlling membrane, whether formed from an ethanol solution or an aqueous dispersion.

Theoretical and experimental investigation of drug-polymer interaction and miscibility and its impact on drug supersaturation in aqueous medium.

PubMed

Baghel, Shrawan; Cathcart, Helen; O'Reilly, Niall J

2016-10-01

Amorphous solid dispersions (ASDs) have the potential to offer higher apparent solubility and bioavailability of BCS class II drugs. Knowledge of the solid state drug-polymer solubility/miscibility and their mutual interaction are fundamental requirements for the effective design and development of such systems. To this end, we have carried out a comprehensive investigation of various ASD systems of dipyridamole and cinnarizine in polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) at different drug loadings. Theoretical and experimental examinations (by implementing binary and ternary Flory-Huggins (F-H) theory) related to drug-polymer interaction/miscibility including solubility parameter approach, melting point depression method, phase diagram, drug-polymer interaction in the presence of moisture and the effect of drug loading on interaction parameter were performed. The information obtained from this study was used to predict the stability of ASDs at different drug loadings and under different thermal and moisture conditions. Thermal and moisture sorption analysis not only provided the composition-dependent interaction parameter but also predicted the composition dependent miscibility. DPM-PVP, DPM-PAA and CNZ-PAA systems have shown molecular level mixing over the complete range of drug loading. For CNZ-PVP, the presence of a single Tg at lower drug loadings (10, 20 and 35%w/w) indicates the formation of solid solution. However, drug recrystallization was observed for samples with higher drug weight fractions (50 and 65%w/w). Finally, the role of polymer in maintaining drug supersaturation has also been explored. It has been found that drug-polymer combinations capable of hydrogen-bonding in the solution state (DPM-PVP, DPM-PAA and CNZ-PAA) are more effective in preventing drug crystallization compared to the drug-polymer systems without such interaction (CNZ-PVP). The DPM-PAA system outperformed all other ASDs in various stability conditions (dry-state, in the presence of moisture and in solution state), which was attributed to the drug's low crystallization tendency, the strong DPM-PAA interaction, the robustness of this interaction against moisture or water and the ability of PAA in maintaining DPM supersaturation. Copyright © 2016 Elsevier B.V. All rights reserved.

Protein-style dynamical transition in a non-biological polymer and a non-aqueous solvent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamontov, E.; Sharma, V. K.; Borreguero, J. M.

Using neutron scattering and molecular dynamics simulation, techniques most often associated with protein dynamical transition studies, we have investigated the microscopic dynamics of one of the most common polymers, polystyrene, which was exposed to toluene vapor, mimicking the process of protein hydration from water vapor. Polystyrene with adsorbed toluene is an example of a solvent-solute system, which, unlike biopolymers, is anhydrous and lacks hydrogen bonding. Nevertheless, it exhibits the essential traits of the dynamical transition in biomolecules, such as a specific dependence of the microscopic dynamics of both solvent and host on the temperature and the amount of solvent adsorbed.more » Ultimately, we conclude that the protein dynamical transition is a manifestation of a universal solvent-solute dynamical relationship, which is not specific to either biomolecules as solute, or aqueous media as solvent, or even a particular type of interactions between solvent and solute.« less

Protein-style dynamical transition in a non-biological polymer and a non-aqueous solvent

DOE PAGES

Mamontov, E.; Sharma, V. K.; Borreguero, J. M.; ...

2016-03-15

Using neutron scattering and molecular dynamics simulation, techniques most often associated with protein dynamical transition studies, we have investigated the microscopic dynamics of one of the most common polymers, polystyrene, which was exposed to toluene vapor, mimicking the process of protein hydration from water vapor. Polystyrene with adsorbed toluene is an example of a solvent-solute system, which, unlike biopolymers, is anhydrous and lacks hydrogen bonding. Nevertheless, it exhibits the essential traits of the dynamical transition in biomolecules, such as a specific dependence of the microscopic dynamics of both solvent and host on the temperature and the amount of solvent adsorbed.more » Ultimately, we conclude that the protein dynamical transition is a manifestation of a universal solvent-solute dynamical relationship, which is not specific to either biomolecules as solute, or aqueous media as solvent, or even a particular type of interactions between solvent and solute.« less

Method of forming a foamed thermoplastic polymer

DOEpatents

Duchane, D.V.; Cash, D.L.

1984-11-21

A solid thermoplastic polymer is immersed in an immersant solution comprising a compatible carrier solvent and an infusant solution containing an incompatible liquid blowing agent for a time sufficient for the immersant solution to infuse into the polymer. The carrier solvent is then selectively extracted, preferably by a solvent exchange process in which the immersant solution is gradually diluted with and replaced by the infusant solution, so as to selectively leave behind the infustant solution permanently entrapped in the polymer. The polymer is then heated to volatilize the blowing agent and expand the polymer into a foamed state.

A new scaling for the rotational diffusion of molecular probes in polymer solutions.

PubMed

Qing, Jing; Chen, Anpu; Zhao, Nanrong

2017-12-13

In the present work, we propose a new scaling form for the rotational diffusion coefficient of molecular probes in semi-dilute polymer solutions, based on a theoretical study. The mean-field theory for depletion effect and semi-empirical scaling equation for the macroscopic viscosity of polymer solutions are properly incorporated to specify the space-dependent concentration and viscosity profiles in the vicinity of the probe surface. Following the scheme of classical fluid mechanics, we numerically evaluate the shear torque exerted on the probes, which then allows us to further calculate the rotational diffusion coefficient D r . Particular attention is given to the scaling behavior of the retardation factor R rot ≡ D/D r with D being the diffusion coefficient in pure solvent. We find that R rot has little relevance to the macroscopic viscosity of the polymer solution, while it can be well featured by the characteristic length scale r h /δ, i.e. the ratio between the hydrodynamic radius of the probe r h and the depletion thickness δ. Correspondingly, we obtain a novel scaling form for the rotational retardation factor, following R rot = exp[a(r h /δ) b ] with rather robust parameters of a ≃ 0.51 and b ≃ 0.56. We apply the theory to an extensive calculation for various probes in specific polymer solutions of poly(ethylene glycol) (PEG) and dextran. Our theoretical results show good agreements with the experimental data, and clearly demonstrate the validity of the new scaling form. In addition, the difference of the scaling behavior between translational and rotational diffusions is clarified, from which we conclude that the depletion effect plays a more significant role on the local rotational diffusion rather than the long-range translation diffusion.

A new method to simulate the effects of viscous fingering on miscible displacement processes in porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vossoughi, S.; Green, D.W.; Smith, J.E.

This paper presents a new method to simulate the effects of viscous fingering on miscible displacement processes in porous media. The method is based on the numerical solution of a general form of the convection-dispersion equation. In this equation the convection term is represented by a fractional flow function. The fractional flow function is derived from Darcy's law using a concentration-dependent, average viscosity and relative flow area to each fluid at any point in the bed. The method was extended to the description of a polymer flood by including retention and inaccessible pore volume. A Langmuir-type model for polymer retentionmore » in the rock was used. The resulting convection-dispersion equation for displacement by polymer was then solved numerically by the use of a finite element method with linear basis functions and Crank-Nicholson derivative approximation. History matches were performed on four sets of laboratory data to verify the model. These were: an unfavorable viscosity ratio displacement, stable displacement of glycerol by polymer solution, unstable displacement of brine by a slug of polymer solution, and a favorable viscosity ratio displacement. In general, computed results from the model matched laboratory data closely. Good agreement of the model with experiments over a significant range of variables lends support to the analysis.« less

Study on improving viscosity of polymer solution based on complex reaction

NASA Astrophysics Data System (ADS)

Sun, G.; Li, D.; Zhang, D.; Xu, T. H.

2018-05-01

The current status of polymer flooding Technology on high salinity oil reservoir is not ideal. A method for increasing the viscosity of polymer solutions is urgently needed. This paper systematically studied the effect of ions with different mass concentrations on the viscosity of polymer solutions. Based on the theory of complex reaction, a countermeasure of increasing viscosity of polymer solution under conditions of high salinity reservoir was proposed. The results show that Ca2+ and Mg2+ have greater influence on the solution viscosity than K+ and Na+. When the concentration of divalent ions increases from 0 mg/L to 80 mg/L, the viscosity of the polymer solution decreases from 210 mPa·s to 38.6 mPa·s. The viscosity of the polymer solution prepared from the sewage treated with the Na2C2O4 increased by 25.3%. Atomic force microscopy test results show that Na2C2O4 can effectively shield the divalent metal ions, so that the polymer molecules in the solution stretch more, thereby increasing the solution viscosity. Atomic force microscopy test results show that Na2C2O4 can effectively shield the divalent metal ions, so that the polymer molecules in the solution stretch more, thereby increasing the solution viscosity.

Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers.

PubMed

Rodríguez-Dorado, Rosalía; Carro, Antonia M; Chianella, Iva; Karim, Kal; Concheiro, Angel; Lorenzo, Rosa A; Piletsky, Sergey; Alvarez-Lorenzo, Carmen

2016-09-01

Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions.

Quantum dot-containing polymer particles with thermosensitive fluorescence.

PubMed

Generalova, Alla N; Oleinikov, Vladimir A; Sukhanova, Alyona; Artemyev, Mikhail V; Zubov, Vitaly P; Nabiev, Igor

2013-01-15

Composite polymer particles consisting of a solid poly(acrolein-co-styrene) core and a poly(N-vinylcaprolactam) (PVCL) polymer shell doped with CdSe/ZnS semiconductor quantum dots (QDs) were fabricated. The temperature response of the composite particles was observed as a decrease in their hydrodynamic diameter upon heating above the lower critical solution temperature of the thermosensitive PVCL polymer. Embedding QDs in the PVCL shell yields particles whose fluorescence is sensitive to temperature changes. This sensitivity was determined by the dependence of the QD fluorescence intensity on the distances between them in the PVCL shell, which reversibly change as a result of the temperature-driven conformational changes in the polymer. The QD-containing thermosensitive particles were assembled with protein molecules in such a way that they retained their thermosensitive properties, including the completely reversible temperature dependence of their fluorescence response. The composite particles developed can be used as local temperature sensors, as carriers for biomolecules, as well as in biosensing and various bioassays employing optical detection schemes. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparison of Methods for Characterizing Nonideal Solute Self-Association by Sedimentation Equilibrium

PubMed Central

Scott, David J.; Winzor, Donald J.

2009-01-01

Abstract We have examined in detail analytical solutions of expressions for sedimentation equilibrium in the analytical ultracentrifuge to describe self-association under nonideal conditions. We find that those containing the radial dependence of total solute concentration that incorporate the Adams-Fujita assumption for composition-dependence of activity coefficients reveal potential shortcomings for characterizing such systems. Similar deficiencies are shown in the use of the NONLIN software incorporating the same assumption about the interrelationship between activity coefficients for monomer and polymer species. These difficulties can be overcome by iterative analyses incorporating expressions for the composition-dependence of activity coefficients predicted by excluded volume considerations. A recommendation is therefore made for the replacement of current software packages by programs that incorporate rigorous statistical-mechanical allowance for thermodynamic nonideality in sedimentation equilibrium distributions reflecting solute self-association. PMID:19651047

Method of forming a foamed thermoplastic polymer

DOEpatents

Duchane, David V.; Cash, David L.

1986-01-01

A method of forming a foamed thermoplastic polymer. A solid thermoplastic lymer is immersed in an immersant solution comprising a compatible carrier solvent and an infusant solution containing an incompatible liquid blowing agent for a time sufficient for the immersant solution to infuse into the polymer. The carrier solvent is then selectively extracted, preferably by a solvent exchange process in which the immersant solution is gradually diluted with and replaced by the infusant solution, so as to selectively leave behind the infusant solution permanently entrapped in the polymer. The polymer is then heated to volatilize the blowing agent and expand the polymer into a foamed state.

The effect of polymer composition on the gelation behavior of PLGA-g-PEG biodegradable thermoreversible gels.

PubMed

Tarasevich, B J; Gutowska, A; Li, X S; Jeong, B-M

2009-04-01

Graft copolymers consisting of a poly(D,L-lactic acid-co-glycolic acid) backbone grafted with polyethylene glycol side chains were synthesized and formed thermoreversible gels in aqueous solutions that exhibited solution behavior at low temperature and sol-to-gel transitions at higher temperature. The composition of the polymer and relative amounts of polylactic acid, glycolic acid, and ethylene glycol were varied by controlling the precursor concentrations and reaction temperature. The gelation temperature could be systematically tailored from 15 to 34 degrees C by increasing the concentration of polyethylene glycol in the graft copolymer. The gelation temperature also depended on the polymer molecular weight and concentration. This work has importance for the development of water soluble gels with tailored compositions and gelation temperatures for use in tissue engineering and as injectable depots for drug delivery. Copyright 2008 Wiley Periodicals, Inc.

Morphology dependent amplified spontaneous emission in π-conjugated polymer

NASA Astrophysics Data System (ADS)

Wang, Yuchen; Yang, Xiao; Wang, Ruizhi; Li, Li; Li, Heng

2015-08-01

The amplified spontaneous emission (ASE) spectra of a π-conjugated polymer Poly [2-methoxy-5-(2‧-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) are studied in as-cast film, annealed film, 1 mg/ml solution and 2.5 mg/ml solution, respectively, using a 10 ns pulsed laser as an excitation source. We found that for annealed film (420 K), the ASE is hardly achieved compared to the as-cast film, which is consistent with the formation of the aggregation; whereas the film's temperature had much less effect on its ASE threshold. In solution, the ASE spectra show both 0-0 peak and 0-1 peak in 1 mg/ml solution, but only 0-1 peak in 2.5 mg/ml one. When the temperature of solution increases slightly from 300 K to 330 K, the ASE threshold increases dramatically in 1 mg/ml solution but slightly in 2.5 mg/ml one. Our results show the important role the morphology played in the ASE spectra in both film and solution. Therefore, controlling the interchain interaction in PCPs may be the key factor for performance of the organic lasers.

Theory of Random Copolymer Fractionation in Columns

NASA Astrophysics Data System (ADS)

Enders, Sabine

Random copolymers show polydispersity both with respect to molecular weight and with respect to chemical composition, where the physical and chemical properties depend on both polydispersities. For special applications, the two-dimensional distribution function must adjusted to the application purpose. The adjustment can be achieved by polymer fractionation. From the thermodynamic point of view, the distribution function can be adjusted by the successive establishment of liquid-liquid equilibria (LLE) for suitable solutions of the polymer to be fractionated. The fractionation column is divided into theoretical stages. Assuming an LLE on each theoretical stage, the polymer fractionation can be modeled using phase equilibrium thermodynamics. As examples, simulations of stepwise fractionation in one direction, cross-fractionation in two directions, and two different column fractionations (Baker-Williams fractionation and continuous polymer fractionation) have been investigated. The simulation delivers the distribution according the molecular weight and chemical composition in every obtained fraction, depending on the operative properties, and is able to optimize the fractionation effectively.

Osmotic pressure and virial coefficients of star and comb polymer solutions: dissipative particle dynamics.

PubMed

Wang, Tzu-Yu; Fang, Che-Ming; Sheng, Yu-Jane; Tsao, Heng-Kwong

2009-03-28

The effects of macromolecular architecture on the osmotic pressure pi and virial coefficients (B(2) and B(3)) of star and comb polymers in good solvents are studied by dissipative particle dynamics simulations for both dilute and semiconcentrated regimes. The dependence of the osmotic pressure on polymer concentration is directly calculated by considering two reservoirs separated by a semipermeable, fictitious membrane. Our simulation results show that the ratios A(n+1) identical with B(n+1)/R(g)(3n) are essentially constant and A(2) and A(3) are arm number (f) dependent, where R(g) is zero-density radius of gyration. The value of dimensionless virial ratio g = A(3)/A(2)(2) increases with arm number of stars whereas it is essentially arm number independent for comb polymers. In semiconcentrated regime the scaling relation between osmotic pressure and volume fraction, pi proportional to phi(lambda), still holds for both star and comb polymers. For comb polymers, the exponent lambda is close to lambda(*) (approximately = 2.73 for linear chains) and is independent of the arm number. However, for star polymers, the exponent lambda deviates from lambda(*) and actually grows with increasing the arm number. This may be attributed to the significant ternary interactions near the star core in the many-arm systems.

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetatexanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan gum gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar. Performance and produced polymer evaluation of four alkaline-surfactant-polymer projects concluded that only one of the projects could have benefited from combining the alkaline-surfactant-polymer and gelation technologies. Cambridge, the 1993 Daqing, Mellott Ranch, and the Wardlaw alkaline-surfacant-polymer floods were studied. An initial gel treatment followed by an alkaline-surfactant-polymer flood in the Wardlaw field would have been a benefit due to reduction of fracture flow.« less

Synthesis, Biodegradability, and Biocompatibility of Lysine Diisocyanate–Glucose Polymers

PubMed Central

ZHANG, JIAN-YING; BECKMAN, ERIC J.; HU, JING; YANG, GUO-GUANG; AGARWAL, SUDHA; HOLLINGER, JEFFREY O.

2016-01-01

The success of a tissue-engineering application depends on the use of suitable biomaterials that degrade in a timely manner and induce the least immunogenicity in the host. With this purpose in mind, we have attempted to synthesize a novel nontoxic biodegradable lysine diisocyanate (LDI)-and glucose-based polymer via polymerization of highly purified LDI with glucose and its subsequent hydration to form a spongy matrix. The LDI–glucose polymer was degradable in aqueous solutions at 37, 22, and 4°C, and yielded lysine and glucose as breakdown products. The degradation products of the LDI–glucose polymer did not significantly affect the pH of the solution. The physical properties of the polymer were found to be adequate for supporting cell growth in vitro, as evidenced by the fact that rabbit bone marrow stromal cells (BMSCs) attached to the polymer matrix, remained viable on its surface, and formed multilayered confluent cultures with retention of their phenotype over a period of 2 to 4 weeks. These observations suggest that the LDI–glucose polymer and its degradation products were nontoxic in vitro. Further examination in vivo over 8 weeks revealed that subcutaneous implantation of hydrated matrix degraded in vivo three times faster than in vitro. The implanted polymer was not immunogenic and did not induce antibody responses in the host. Histological analysis of the implanted polymer showed that LDI–glucose polymer induced a minimal foreign body reaction, with formation of a capsule around the degrading polymer. The results suggest that biodegradable peptide-based polymers can be synthesized, and may potentially find their way into biomedical applications because of their biodegradability and biocompatibility. PMID:12459056

Application of solution-processed V2O5 in inverted polymer solar cells based on fluorine-doped tin oxide substrate.

PubMed

Wu, Jian; Zhang, Yupeng; He, Yeyuan; Liu, Chunyu; Guolt, Wenbin; Ruan, Shengping

2014-06-01

We used a hydrothermal method to synthesis the solution-processed V2O5 as anode buffer layer, which applied on inverted polymer solar cells based on FTO substrate. The structure of the device is glass/FTO/TiO2/P3HT:PCBM/V2O5/Ag. We discussed the dependence of device performance on the concentrations of V2O5 solution. It is found that when the concentration of V2O5 is 300 microg/ml, the power conversion efficiency (PCE of 2.38%) is the highest, which is much higher than that of the device without anode buffer layer (PCE of only 0.87%). Moreover, it can significantly reduce the energy consumption and make it more cost-effective.

Sweet Polymers: Poly(2-ethyl-2-oxazoline) Glycopolymers by Reductive Amination.

PubMed

Mees, Maarten A; Effenberg, Christiane; Appelhans, Dietmar; Hoogenboom, Richard

2016-12-12

Carbohydrates are important in signaling, energy storage, and metabolism. Depending on their function, carbohydrates can be part of larger structures, such as glycoproteins, glycolipids, or other functionalities (glycoside). To this end, polymers can act as carriers of carbohydrates in so-called glycopolymers, which mimic the multivalent carbohydrate functionalities. We chose a biocompatible poly(2-ethyl-2-oxazoline) (PEtOx) as the basis for making glycopolymers. Via the partial hydrolysis of PEtOx, a copolymer of PEtOx and polyethylenimine (PEI) was obtained; the subsequent reductive amination with the linear forms of glucose and maltose yielded the glycopolymers. The ratios of PEtOx and carbohydrates were varied systematically, and the solution behaviors of the resulting glycoconjugates are discussed. Dynamic light scattering (DLS) revealed that, depending on the carbohydrate ratio, the glycopolymers were either fully water-soluble or formed agglomerates in a temperature-dependent manner. Finally, these polymers were tested for their biological availability by studying their lectin binding ability with Concanavalin A.

Verification of the modified model of the drying process of a polymer liquid film on a flat substrate by experiment (2): through more accurate experiment

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2006-05-01

We have proposed and modified a model of drying process of polymer solution coated on a flat substrate for flat polymer film fabrication and have presented the fruits through Photomask Japan 2002, 2003, 2004 and so on. And for example numerical simulation of the model qualitatively reappears a typical thickness profile of the polymer film formed after drying, that is, the profile that the edge of the film is thicker and just the region next to the edge's bump is thinner. Then we have clarified dependence of distribution of polymer molecules on a flat substrate on a various parameters based on analysis of many numerical simulations. Then we done a few kinds of experiments so as to verify the modified model and reported the initial result of them through Photomask Japan 2005. Through the initial result we could observe some results supporting the modified model. But we could not observe a characteristic region of a valley next to the edge's bump of a polymer film after drying because a shape of a solution's film coated on a substrate in the experiment was different from one in resists' coating and drying process or imagined in the modified model. In this study, we improved above difference between experiment and the model and did experiments for verification again with a shape of a solution's film coated on a substrate coincident with one imagined in the modified model and using molar concentration. As a result, some were verified more strongly and some need to be examined again. That is, we could confirm like results of last experiment that the smaller average molecular weight of Metoloses was, the larger the gradient of thickness profile of a polymer thin film was. But we could not observe a depression just inside the edge of the thin film also in this improved experiment. We may be able to enumerate the fact that not an organic solution but an aqueous solution was used in the experiment as the cause of non-formation of the depression.

Coupling the Alkaline-Surfactant-Polymer Technology and the Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding froin swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan guin gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar.« less

Poly(hydroxy alkanoate)s in Medical Applications

PubMed Central

Luef, K. P.; Stelzer, F.; Wiesbrock, F.

2017-01-01

This review summarizes the state-of-the-art knowledge of the usage of poly(hydroxy alkanoate)s in medical and sanitary applications. Depending on the monomers incorporated into the polymers and copolymers, this class of polymers exhibits a broad range of (thermo-)plastic properties, enabling their processing by, e.g., solution casting or melt extrusion. In this review, strategies for the polymer analogous modification of these materials and their surfaces are highlighted and correlated with the potential applications of the corresponding materials and blends. While the commercial availability of purified PHAs is addressed in brief, special focus is put on the (bio-)degradability of these polymers and ways to influence the degradation mechanism and/or the duration of degradation. PMID:28239227

Removal of Cu(II) in water by polymer enhanced ultrafiltration: Influence of polymer nature and pH.

PubMed

Kochkodan, Olga D; Kochkodan, Viktor M; Sharma, Virender K

2018-01-02

This study presents an efficient removal of Cu(II) in water using the polymer enhanced ultrafiltration (PEUF) method. Polymer of different molecular weight (MW) (polyethyleneimine (PEI), sodium lignosulfonates (SLS) and dextrans) were investigated to evaluate efficiency in removal of Cu(II) in water by the PEUF method. The decomposition of Cu(II)-polymer complex was also evaluated in order to reuse polymers. Cu(II) complexation depends on the MW of chelating polymer and the pH of feed solution. It was found that the Cu(II) rejection increased with the polymer dosage with high removal of Cu(II) when using PEI and SLS at a 10:20 (mg/mg) ratio ([Cu(II)]:[polymer]). It was found that the maximum chelating capacity was 15 mg of Cu(II) per 20 mg of PEI. The Cu(II)-PEI complex could be decomposed by acid addition and the polymer could be efficiently reused with multiple complexation-decomplexation cycles. A conceptual flow chart of the integrated process of efficient removal of Cu(II) by PEUF method is suggested.

Enhanced polymer capture speed and extended translocation time in pressure-solvation traps

NASA Astrophysics Data System (ADS)

Buyukdagli, Sahin

2018-06-01

The efficiency of nanopore-based biosequencing techniques requires fast anionic polymer capture by like-charged pores followed by a prolonged translocation process. We show that this condition can be achieved by setting a pressure-solvation trap. Polyvalent cation addition to the KCl solution triggers the like-charge polymer-pore attraction. The attraction speeds-up the pressure-driven polymer capture but also traps the molecule at the pore exit, reducing the polymer capture time and extending the polymer escape time by several orders of magnitude. By direct comparison with translocation experiments [D. P. Hoogerheide et al., ACS Nano 8, 7384 (2014), 10.1021/nn5025829], we characterize as well the electrohydrodynamics of polymers transport in pressure-voltage traps. We derive scaling laws that can accurately reproduce the pressure dependence of the experimentally measured polymer translocation velocity and time. We also find that during polymer capture, the electrostatic barrier on the translocating molecule slows down the liquid flow. This prediction identifies the streaming current measurement as a potential way to probe electrostatic polymer-pore interactions.

Impact of Backbone Tether Length and Structure on the Electrochemical Performance of Viologen Redox Active Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgess, Mark; Chénard, Etienne; Hernández-Burgos, Kenneth

The design of chemically stable and electrochemically reversible redox active polymers (RAPs) is of great interest for energy storage technologies. Particularly, RAPs are new players for flow batteries relying on a size-exclusion based mechanism of electrolyte separation, but few studies have provided detailed molecular understanding of redox polymers in solution. Here, we use a systematic molecular design approach to investigate the impact of linker and redox-pendant electronic interactions on the performance of viologen RAPs. We used scanning electrochemical microscopy, cyclic voltammetry, bulk electrolysis, temperature-dependent absorbance, and spectroelectrochemistry to study the redox properties, charge transfer kinetics, and self-exchange of electrons throughmore » redox active dimers and their equivalent polymers. Stark contrast was observed between the electrochemical properties of viologen dimers and their corresponding polymers. Electron self-exchange kinetics in redox active dimers that only differ by their tether length and rigidity influences their charge transfer properties. Predictions from the Marcus Hush theory were consistent with observations in redox active dimers, but they failed to fully capture the behavior of macromolecular systems. For example, polymer bound viologen pendants, if too close in proximity, do not retain chemical reversibility. In contrast to polymer films, small modifications to the backbone structure decisively impact the bulk electrolysis of polymer solutions. This first comprehensive study highlights the careful balance between electronic interactions and backbone rigidity required to design RAPs with superior electrochemical performance.« less

Closed-form solution of the Ogden-Hill's compressible hyperelastic model for ramp loading

NASA Astrophysics Data System (ADS)

Berezvai, Szabolcs; Kossa, Attila

2017-05-01

This article deals with the visco-hyperelastic modelling approach for compressible polymer foam materials. Polymer foams can exhibit large elastic strains and displacements in case of volumetric compression. In addition, they often show significant rate-dependent properties. This material behaviour can be accurately modelled using the visco-hyperelastic approach, in which the large strain viscoelastic description is combined with the rate-independent hyperelastic material model. In case of polymer foams, the most widely used compressible hyperelastic material model, the so-called Ogden-Hill's model, was applied, which is implemented in the commercial finite element (FE) software Abaqus. The visco-hyperelastic model is defined in hereditary integral form, therefore, obtaining a closed-form solution for the stress is not a trivial task. However, the parameter-fitting procedure could be much faster and accurate if closed-form solution exists. In this contribution, exact stress solutions are derived in case of uniaxial, biaxial and volumetric compression loading cases using ramp-loading history. The analytical stress solutions are compared with the stress results in Abaqus using FE analysis. In order to highlight the benefits of the analytical closed-form solution during the parameter-fitting process experimental work has been carried out on a particular open-cell memory foam material. The results of the material identification process shows significant accuracy improvement in the fitting procedure by applying the derived analytical solutions compared to the so-called separated approach applied in the engineering practice.

Isolation and characterization of chitin and chitosan from marine origin.

PubMed

Nwe, Nitar; Furuike, Tetsuya; Tamura, Hiroshi

2014-01-01

Nowadays, chitin and chitosan are produced from the shells of crabs and shrimps, and bone plate of squid in laboratory to industrial scale. Production of chitosan involved deproteinization, demineralization, and deacetylation. The characteristics of chitin and chitosan mainly depend on production processes and conditions. The characteristics of these biopolymers such as appearance of polymer, turbidity of polymer solution, degree of deacetylation, and molecular weight are of major importance on applications of these polymers. This chapter addresses the production processes and conditions to produce chitin, chitosan, and chito-oligosaccharide and methods for characterization of chitin, chitosan, and chito-oligosaccharide. © 2014 Elsevier Inc. All rights reserved.

Relaxation model of radiation-induced conductivity in polymers

NASA Astrophysics Data System (ADS)

Zhutayeva, Yu. R.; Khatipov, S. A.

1999-05-01

The paper suggests a relaxation model of radiation-induced conductivity (RIC) in polymers. According to the model, the transfer of charges generated in the polymer volume by ionizing radiation takes place with the participation of molecular relaxation processes. The mechanism of electron transport consists in the transfer of the charge directly between traps when they draw close to one another due to the rotation of macromolecule segments. The numerical solutions of the corresponding kinetic equations for different distribution functions Q( τ) of the times of molecular relaxation and for different functions of the probability P( τ, τ') of charge transfer in the `overlapping' regions of the diffusion spheres of the segments are analyzed. The relaxation model provides an explanation of the non-Arrhenius behavior of the RIC temperature dependence, the power dependence of RIC on the dose rate with a power index in the interval 0.5-1.0, the appearance of maxima in the curves of the RIC temporal dependence and their irreversible character in the region of large dose rates (more than 1 Gy/s). The model can be used for interpreting polymer RIC in conditions of kinetic mobility of macromolecules.

Water-soluble polymers for recovery of metal ions from aqueous streams

DOEpatents

Smith, Barbara F.; Robison, Thomas W.

1998-01-01

A process of selectively separating a target metal contained in an aqueous solution by contacting the aqueous solution containing a target metal with an aqueous solution including a water-soluble polymer capable of binding with the target metal for sufficient time whereby a water-soluble polymer-target metal complex is formed, and, separating the solution including the water-soluble polymer-target metal complex from the solution is disclosed.

Delivery of fullerene-containing complexes via microgel swelling and shear-induced release.

PubMed

Tarabukina, Elena; Zoolshoev, Zoolsho; Melenevskaya, Elena; Budtova, Tatiana

2010-01-15

The absorption and release of poly(vinylpyrrolidone)-fullerene C60 complexes (PVP/C60) from a model microgel is studied. A dry microgel based on a chemically cross-linked sodium polyacrylate was swollen in the aqueous solutions of complexes which were afterwards released under shear stress. First, gel swelling degree in static conditions in the excess of PVP/C60 solutions was studied: the degree of swelling decreases with the increase in PVP/C60 concentration. While pure PVP is homogeneously distributed between the gel and the surrounding solution, a slight concentration of complexes outside the gel was recorded. It was attributed to PVP/C60 hydrophobicity leading to the decrease in the thermodynamic quality of fullerene-containing solution being gel solvent. The release of PVP/C60 solutions induced by shear was studied with counter-rotating rheo-optical technique and compared with PVP solution release under the same conditions. The amount of solution released depends on polymer concentration and shear strain. Contrary to pure PVP solutions in which rate of release decreases with the increase in polymer concentration, PVP/C60 complexes are released faster when fullerene concentration inside the gel is higher.

Preparation and electrochemical characterization of polymer electrolytes based on electrospun poly(vinylidene fluoride- co-hexafluoropropylene)/polyacrylonitrile blend/composite membranes for lithium batteries

NASA Astrophysics Data System (ADS)

Raghavan, Prasanth; Zhao, Xiaohui; Shin, Chorong; Baek, Dong-Ho; Choi, Jae-Won; Manuel, James; Heo, Min-Yeong; Ahn, Jou-Hyeon; Nah, Changwoon

Apart from PEO based solid polymer electrolytes, tailor-made gel polymer electrolytes based on blend/composite membranes of poly(vinylidene fluoride- co-hexafluoropropylene) and polyacrylonitrile are prepared by electrospinning using 14 wt% polymer solution in dimethylformamide. The membranes show uniform morphology with an average fiber diameter of 320-490 nm, high porosity and electrolyte uptake. Polymer electrolytes are prepared by soaking the electrospun membranes in 1 M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate. Temperature dependent ionic conductivity and their electrochemical performance are studied. The blend/composite polymer electrolytes show good ionic conductivity in the range of 10 -3 S cm -1 at ambient temperature and good electrochemical performance. All the Polymer electrolytes show an anodic stability >4.6 V with stable interfacial resistance with storage time. The prototype cell shows good charge-discharge properties and stable cycle performance with comparable capacity fade compared to liquid electrolyte under the test conditions.

Directed ordering of phase separated domains and dewetting of thin polymer blend films on a topographically patterned substrate.

PubMed

Bhandaru, Nandini; Karim, Alamgir; Mukherjee, Rabibrata

2017-07-21

Substrate pattern guided self-organization of ultrathin and confined polymeric films on a topographically patterned substrate is a useful approach for obtaining ordered meso and nano structures over large areas, particularly if the ordering is achieved during film preparation itself, eliminating any post-processing such as thermal or solvent vapor annealing. By casting a dilute solution of two immiscible polymers, polystyrene (PS) and polymethylmethacrylate (PMMA), from a common solvent (toluene) on a topographically patterned substrate with a grating geometry, we show the formation of self-organized meso patterns with various degrees of ordering. The morphology depends on both the concentration of the dispensed solution (C n ) and the blend composition (R B ). Depending on the extent of dewetting during spin coating, the final morphologies can be classified into three distinct categories. At a very low C n the solution dewets fully, resulting in isolated polymer droplets aligned along substrate grooves (Type 1). Type 2 structures comprising isolated threads with aligned phase separated domains along each substrate groove are observed at intermediate C n . A continuous film (Type 3) is obtained above a critical concentration (C n *) that depends on R B . While the extent of ordering of the domains gradually diminishes with an increase in film thickness for Type 3 patterns, the size of the domains remains much smaller than that on a flat substrate, resulting in significant downsizing of the features due to the lateral confinement imposed on the phase separation process by the topographic patterns. Finally, we show that some of these structures exhibit excellent broadband anti-reflection (AR) properties.

Polymer relaxation and stretching dynamics in semi-dilute DNA solutions: a single molecule study

NASA Astrophysics Data System (ADS)

Hsiao, Kai-Wen; Brockman, Christopher; Schroeder, Charles

2015-03-01

In this work, we study polymer relaxation and stretching dynamics in semi-dilute DNA solutions using single molecule techniques. Using this approach, we uncover a unique scaling relation for longest polymer relaxation time that falls in the crossover regime described by semi-flexible polymer solutions, which is distinct from truly flexible polymer chains. In addition, we performed a series of step-strain experiments on single polymers in semi-dilute solutions in planar extensional flow using an automated microfluidic trap. In this way, we are able to precisely control the flow strength and the amount of strain applied to single polymer chains, thereby enabling direct observation of the full stretching and relaxation process in semi-dilute solutions during transient start-up and flow cessation. Interestingly, we observe polymer individualism in the conformation of single chains in semi-dilute solutions, which to our knowledge has not yet been observed. In addition, we observe the relaxation data can be explained by a multi-exponential decay process after flow cessation in semi-dilute solutions. Overall, our work reports key advance in non-dilute polymer systems from a molecular perspective via direct observation of dynamics in strong flows. DOW fellowship.

Functionalized polymers for binding to solutes in aqueous solutions

DOEpatents

Smith, Barbara F.; Robison, Thomas W.

2006-11-21

A functionalized polymer for binding a dissolved molecule in an aqueous solution is presented. The polymer has a backbone polymer to which one or more functional groups are covalently linked. The backbone polymer can be such polymers as polyethylenimine, polyvinylamine, polyallylamine, and polypropylamine. These polymers are generally water-soluble, but can be insoluble when cross-linked. The functional group can be for example diol derivatives, polyol derivatives, thiol and dithiol derivatives, guest-host groups, affinity groups, beta-diphosphonic acids, and beta-diamides

Reduced viscosity for flagella moving in a solution of long polymer chains

NASA Astrophysics Data System (ADS)

Zhang, Yuchen; Li, Gaojin; Ardekani, Arezoo M.

2018-02-01

The bacterial flagellum thickness is smaller than the radius of gyration of long polymer chain molecules. The flow velocity gradient over the length of polymer chains can be nonuniform and continuum models of polymeric liquids break in this limit. In this work, we use Brownian dynamics simulations to study a rotating helical flagellum in a polymer solution and overcome this limitation. As the polymer size increases, the viscosity experienced by the flagellum asymptotically reduces to the solvent viscosity. The contribution of polymer molecules to the local viscosity in a solution of long polymer chains decreases with the inverse of polymer size to the power 1/2. The difference in viscosity experienced by the bacterial cell body and flagella can predict the nonmonotonic swimming speed of bacteria in polymer solutions.

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-10-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or more efficient areal sweep efficiency for those with high permeability contrast ''thief zones''. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or those with thief zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. A priormore » fluid-fluid report discussed interaction of different gel chemical compositions and alkaline-surfactant-polymer solutions. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses. Aluminum-polyacrylamide, flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9. Chromium acetate-polyacrylamide flowing and rigid flowing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid flowing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid flowing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid flowing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. None of the gels tested appeared to alter alkaline-surfactant-polymer solution oil recovery. Total waterflood plus chemical flood oil recovery sequence recoveries were all similar. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate gels that were stable to injection of alkaline-surfactant-polymer solutions at 72 F were stable to injection of alkaline-surfactant-polymer solutions at 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Xanthan gum-chromium acetate gels maintained gel integrity in linear corefloods after injection of an alkaline-surfactant-polymer solution at 125 F. At 175 F, Xanthan gum-chromium acetate gels were not stable either with or without subsequent alkaline-surfactant-polymer solution injection. Numerical simulation demonstrated that reducing the permeability of a high permeability zone of a reservoir with gel improved both waterflood and alkaline-surfactant-polymer flood oil recovery. A Minnelusa reservoir with both A and B sand production was simulated. A and B sands are separated by a shale layer. A sand and B sand waterflood oil recovery was improved by 196,000 bbls when a gel was placed in the B sand. A sand and B sand alkaline-surfactant-polymer flood oil recovery was improved by 596,000 bbls when a gel was placed in the B sand. Alkaline-surfactant-polymer flood oil recovery improvement over a waterflood was 392,000 bbls. Placing a gel into the B sand prior to an alkaline-surfactant-polymer flood resulted in 989,000 bbl more oil than only water injection.« less

Single polymer dynamics in semi-dilute unentangled and entangled solutions: from molecular conformation to normal stress

NASA Astrophysics Data System (ADS)

Schroeder, Charles

Semi-dilute polymer solutions are encountered in a wide array of applications such as advanced 3D printing technologies. Semi-dilute solutions are characterized by large fluctuations in concentration, such that hydrodynamic interactions, excluded volume interactions, and transient chain entanglements may be important, which greatly complicates analytical modeling and theoretical treatment. Despite recent progress, we still lack a complete molecular-level understanding of polymer dynamics in these systems. In this talk, I will discuss three recent projects in my group to study semi-dilute solutions that focus on single molecule studies of linear and ring polymers and a new method to measure normal stresses in microfluidic devices based on the Stokes trap. In the first effort, we use single polymer techniques to investigate the dynamics of semi-dilute unentangled and semi-dilute entangled DNA solutions in extensional flow, including polymer relaxation from high stretch, transient stretching dynamics in step-strain experiments, and steady-state stretching in flow. In the semi-dilute unentangled regime, our results show a power-law scaling of the longest polymer relaxation time that is consistent with scaling arguments based on the double cross-over regime. Upon increasing concentration, we observe a transition region in dynamics to the entangled regime. We also studied the transient and steady-state stretching dynamics in extensional flow using the Stokes trap, and our results show a decrease in transient polymer stretch and a milder coil-to-stretch transition for semi-dilute polymer solutions compared to dilute solutions, which is interpreted in the context of a critical Weissenberg number Wi at the coil-to-stretch transition. Interestingly, we observe a unique set of polymer conformations in semi-dilute unentangled solutions that are highly suggestive of transient topological entanglements in solutions that are nominally unentangled at equilibrium. Taken together, these results suggest that the transient stretching pathways in semi-dilute solution extensional flows are qualitatively different than for both dilute solutions and for semi-dilute solutions in shear flow. In a second effort, we studied the dynamics of ring polymers in background solutions of semi-dilute linear polymers. Interestingly, we observe strikingly large fluctuations in steady-state polymer extension for ring polymers in flow, which occurs due to the interplay between polymer topology and concentration leading to chain `threading' in flow. In a third effort, we developed a new microfluidic method to measure normal stress and extensional viscosity that can be loosely described as passive yet non-linear microrheology. In particular, we incorporated 3-D particle imaging velocimetry (PIV) with the Stokes trap to study extensional flow-induced particle migration in semi-dilute polymer solutions. Experimental results are analyzed using the framework of a second-order-fluid model, which allows for measurement of normal stress and extensional viscosity in semi-dilute polymer solutions, all of which is a first-of-its-kind demonstration. Microfluidic measurements of extensional viscosity are directly compared to the dripping-onto-substrate or DOS method, and good agreement is generally observed. Overall, our work aims to provide a molecular-level understanding of the role of polymer topology and concentration on bulk rheological properties by using single polymer techniques.

The effect of solute concentration on hindered gradient diffusion in polymeric gels

NASA Astrophysics Data System (ADS)

Buck, Kristan K. S.; Dungan, Stephanie R.; Phillips, Ronald J.

1999-10-01

The effect of solute concentration on hindered diffusion of sphere-like colloidal solutes in stiff polymer hydrogels is examined theoretically and experimentally. In the theoretical development, it is shown that the presence of the gel fibres enhances the effect of concentration on the thermodynamic driving force for gradient diffusion, while simultaneously reducing the effect of concentration on the hydrodynamic drag. The result is that gradient diffusion depends more strongly on solute concentration in gels than it does in pure solution, by an amount that depends on the partition coefficient and hydraulic permeability of the gel solute system. Quantitative calculations are made to determine the concentration-dependent diffusivity correct to first order in solute concentration. In order to compare the theoretical predictions with experimental data, rates of diffusion have been measured for nonionic micelles and globular proteins in solution and agarose hydrogels at two gel concentrations. The measurements were performed by using holographic interferometry, through which one monitors changes in refractive index as gradient diffusion takes place within a transparent gel. If the solutes are modelled as spheres with short-range repulsive interactions, then the experimentally measured concentration dependence of the diffusivities of both the protein and micelles is in good agreement with the theoretical predictions.

Osmotic pressure driven protein release from viscous liquid, hydrophobic polymers based on 5-ethylene ketal ε-caprolactone: potential and mechanism.

PubMed

Babasola, Iyabo Oladunni; Zhang, Wei; Amsden, Brian G

2013-11-01

In this study, the potential of low molecular weight, viscous liquid polymers based on 5-ethylene ketal ε-caprolactone for localized delivery of proteins via an osmotic pressure release mechanism was investigated. Furthermore, the osmotic release mechanism from viscous liquid polymers was elucidated. 5-Ethylene ketal ε-caprolactone was homopolymerized or copolymerized with D,L-lactide (DLLA) by ring-opening polymerization. Polymer hydrophobicity was adjusted by choice of initiator; hydrophobic polymers were prepared by initiating with octan-1-ol, while more hydrophilic polymers were prepared by initiating with 350 g/mol methoxy poly(ethylene glycol) (PEG). Particles consisting of bovine serum albumin (BSA) as a model protein drug were co-lyophilized with trehalose at 50:50 and 10:90 (w/w) ratios and were mixed into the polymers at 1% and/or 5% (w/w) particle loading. The release and mechanism of release of BSA from the polymers were assessed in vitro. BSA was released in a sustained manner, with a near zero-order release profile and with minimal burst effect for 5-80 days depending on the polymer's hydrophilicity; the release was faster from the PEG initiated polymers than from the octan-1-ol initiated polymers. Increasing the particle loading from 1% to 5% (w/w) resulted in a more noticeable burst effect, but did not significantly increase the mass fraction release rate. This release behavior was determined to proceed as follows. Release from the polymer was triggered by the water activity gradient between the surrounding aqueous medium and the saturated solution, which forms when water is absorbed from the surrounding medium to dissolve a given particle. The generated pressure initiates swelling around the particle/polymer interface and creates a superhydrated polymer region through which the solute is transported by convection, at a rate determined by the osmotic pressure generated. Copyright © 2013 Elsevier B.V. All rights reserved.

Particle characterization of poorly water-soluble drugs using a spray freeze drying technique.

PubMed

Kondo, Masahiro; Niwa, Toshiyuki; Okamoto, Hirokazu; Danjo, Kazumi

2009-07-01

A spray freeze drying (SFD) method was developed to prepare the composite particles of poorly water-soluble drug. The aqueous solution dissolved drug and the functional polymer was sprayed directly into liquid nitrogen. Then, the iced droplets were lyophilized with freeze-dryer to prepare solid particles. Tolbutamide (TBM) and hydroxypropylmethylcellulose (HPMC) were used as a model drug and water-soluble polymeric carrier in this study, respectively. The morphological observation of particles revealed that the spherical particles having porous structure could be obtained by optimizing the loading amount of drug and polymer in the spray solution. Especially, SFD method was characterized that the prepared particles had significantly larger specific surface area comparing with those prepared by the standard spray drying technique. The physicochemical properties of the resultant particles were found to be dependent on the concentration of spray solution. When the solution with high content of drug and polymer was used, the particle size of the resulting composite particles increased and they became spherical. The specific surface area of the particles also increased as a result of higher concentration of solution. The evaluation of spray solution indicated that these results were dependent on the viscosity of spray solution. In addition, when composite particles of TBM were prepared using the SFD method with HPMC as a carrier, the crystallinity of TBM decreased as the proportion of HPMC increased. When the TBM : HPMC ratio reached 1 : 5, the crystallinity of the particles completely disappeared. The dissolution tests showed that the release profiles of poorly water-soluble TBM from SFD composite particles were drastically improved compared to bulk TBM. The 70% release time T(70) of composite particles prepared by the SFD method in a solution of pH 1.2 was quite smaller than that of bulk TBM, while in a solution of pH 6.8, it was slightly lower. In addition, the release rates were faster than those of standard spray dried (SD) composite particles for solutions of pH 1.2 and 6.8, respectively. When composite particles were prepared from mixtures with various composition ratios, T(70) was found to decrease as the proportion of HPMC increased; the release rate was faster than that of bulk TBM in a solution of pH 6.8, as well as solution of pH 1.2.

Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.

PubMed

Congdon, Thomas; Dean, Bethany T; Kasperczak-Wright, James; Biggs, Caroline I; Notman, Rebecca; Gibson, Matthew I

2015-09-14

Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes.

Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers

PubMed Central

2015-01-01

Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL–1. Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes PMID:26258729

Synthesis and characterization of ion containing polymers

NASA Astrophysics Data System (ADS)

Dou, Shichen

Two types of ion-containing polymers are included in this dissertation. The first was focused on the rheology, solvation, and correlation length of polyelectrolyte solutions in terms of charge density, solvent dielectric constant, and solvent quality. The second was focused on the PEO-based polyester ionomers as single ion conductors. A series of polyelectrolytes with varied charge density (0.03 < alpha < 0.6) and counterions (Cl- and I-) were investigated in good solvent (EG, NMF, and GC) and poor solvent (DW and F). The concentration dependence of the specific viscosity and relaxation time of polyelectrolytes in solution agrees with Dobrynin's theoretical predictions at c < c**. Effective charge density greatly impacts the viscosity of polyelectrolyte semidilute solutions, while residual salt significantly reduces the viscosity of polyelectrolyte solutions at concentrations c < 2cs/f. For polyelectrolyte solutions with less condensed counterions, the correlation length obtained from SAXS and rheology perfectly matches and agrees with de Gennes prediction. Dobrynin scaling model successfully predicts the rheology of polyelectrolyte solutions in all cases: without salt, with low residual salt, and with high residual salt concentration. PEO-based polyester ionomers were synthesized by melt polycondensation. Mn was determined using the 1H NMR of ionomers. No ion-cluster was observed from the DSC, SAXS, and rheology measurements. Ionic conductivity greatly depends on the Tg, T-T g and ion content of the ionomers. PEG600-PTMO650 (z)-Li copolyester ionomers show microphase separation and much lower ionic conductivity, compared to that of PE600-Li. PTMO650-Li shows nonconductor behavior.

Polymer concentration and properties of elastic turbulence in a von Karman swirling flow

NASA Astrophysics Data System (ADS)

Jun, Yonggun; Steinberg, Victor

2017-10-01

We report detailed experimental studies of statistical, scaling, and spectral properties of elastic turbulence (ET) in a von Karman swirling flow between rotating and stationary disks of polymer solutions in a wide, from dilute to semidilute entangled, range of polymer concentrations ϕ . The main message of the investigation is that the variation of ϕ just weakly modifies statistical, scaling, and spectral properties of ET in a swirling flow. The qualitative difference between dilute and semidilute unentangled versus semidilute entangled polymer solutions is found in the dependence of the critical Weissenberg number Wic of the elastic instability threshold on ϕ . The control parameter of the problem, the Weissenberg number Wi, is defined as the ratio of the nonlinear elastic stress to dissipation via linear stress relaxation and quantifies the degree of polymer stretching. The power-law scaling of the friction coefficient on Wi/Wic characterizes the ET regime with the exponent independent of ϕ . The torque Γ and pressure p power spectra show power-law decays with well-defined exponents, which has values independent of Wi and ϕ separately at 100 ≤ϕ ≤900 ppm and 1600 ≤ϕ ≤2300 ppm ranges. Another unexpected observation is the presence of two types of the boundary layers, horizontal and vertical, distinguished by their role in the energy pumping and dissipation, which has width dependence on Wi and ϕ differs drastically. In the case of the vertical boundary layer near the driving disk, wvv is independent of Wi/Wic and linearly decreases with ϕ /ϕ * , while in the case of the horizontal boundary layer wvh its width is independent of ϕ /ϕ * , linearly decreases with Wi/Wic , and is about five times smaller than wvv. Moreover, these Wi and ϕ dependencies of the vertical and horizontal boundary layer widths are found in accordance with the inverse turbulent intensity calculated inside the boundary layers Vθh/Vθh rms and Vθv/Vθv rms , respectively. Specifically, the dependence of Vθv/Vθv rms in the vertical boundary layer on Wi and ϕ agrees with a recent theoretical prediction [S. Belan, A. Chernych, and V. Lebedev, Boundary layer of elastic turbulence (unpublished)].

Morphological study on small molecule acceptor-based organic solar cells with efficiencies beyond 7% (Presentation Recording)

NASA Astrophysics Data System (ADS)

Ma, Wei; Yan, He

2015-10-01

Despite the essential role of fullerenes in achieving best-performance organic solar cells (OSCs), fullerene acceptors have several drawbacks including poor light absorption, high-cost production and purification. For this reason, small molecule acceptor (SMA)-based OSCs have attracted much attention due to the easy tunability of electronic and optical properties of SMA materials. In this study, polymers with temperature dependent aggregation behaviors are combined with various small molecule acceptor materials, which lead to impressive power conversion efficiencies of up to 7.3%. The morphological and aggregation properties of the polymer:small molecule blends are studied in details. It is found that the temperature-dependent aggregation behavior of polymers allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:small molecule morphology that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of small molecules. As a result, several cases of highly efficient (PCE between 6-7.3%) SMA OSCs are achieved. The second part of this presentation will describe the morphology of a new small molecule acceptor with a unique 3D structure. The relationship between molecular structure and morphology is revealed.

PEG-poly(amino acid) block copolymer micelles for tunable drug release.

PubMed

Ponta, Andrei; Bae, Younsoo

2010-11-01

To achieve tunable pH-dependent drug release in tumor tissues. Poly(ethylene glycol)-poly(aspartic acid) [PEG-p(Asp)] containing 12 kDa PEG and pAsp (5, 15, and 35 repeating units) were prepared. Hydrazide linkers with spacers [glycine (Gly) and 4-aminobenzoate (Abz)] were introduced to PEG-p(Asp), followed by drug conjugation [doxorubicin (DOX)]. The block copolymer-drug conjugates were either reconstituted or dialyzed in aqueous solutions to prepare micelles. Drug release patterns were observed under sink conditions at pH 5.0 and 7.4, 37°C, for 48 h. A collection of six block copolymers with different chain lengths and spacers was synthesized. Drug binding yields were 13-43.6%. The polymer-drug conjugates formed <50 nm polymer micelles irrespective of polymer compositions. Gly-introduced polymer micelles showed marginal change in particle size (40 ± 10 nm), while the size of Abz-micelles increased gradually from 10 to 40 nm as the polymer chain lengths increased. Drug release patterns of both Gly and Abz micelles were pH-dependent and tunable. The spacers appear to play a crucial role in controlling drug release and stability of polymer micelles in combination with block copolymer chain lengths. A drug delivery platform for tunable drug release was successfully developed with polymer micelles possessing spacer-modified hydrazone drug-binding linkers.

Effect of Surface Hydration on Antifouling Properties of Mixed Charged Polymers.

PubMed

Leng, Chuan; Huang, Hao; Zhang, Kexin; Hung, Hsiang-Chieh; Xu, Yao; Li, Yaoxin; Jiang, Shaoyi; Chen, Zhan

2018-05-07

Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water, and how such structures change while exposing to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property while other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.

Development and Characterization of Poly(1-vinylpyrrolidone-co-vinyl acetate) Copolymer Based Polymer Electrolytes

PubMed Central

Sa'adun, Nurul Nadiah; Subramaniam, Ramesh; Kasi, Ramesh

2014-01-01

Gel polymer electrolytes (GPEs) are developed using poly(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] as the host polymer, lithium bis(trifluoromethane) sulfonimide [LiTFSI] as the lithium salt and ionic liquid, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMImTFSI] by using solution casting technique. The effect of ionic liquid on ionic conductivity is studied and the optimum ionic conductivity at room temperature is found to be 2.14 × 10−6 S cm−1 for sample containing 25 wt% of EMImTFSI. The temperature dependence of ionic conductivity from 303 K to 353 K exhibits Arrhenius plot behaviour. The thermal stability of the polymer electrolyte system is studied by using thermogravimetric analysis (TGA) while the structural and morphological properties of the polymer electrolyte is studied by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD), respectively. PMID:25431781

Preceramic Polymers for Use as Fiber Coatings

NASA Technical Reports Server (NTRS)

Heimann, P. J.; Hurwitz, F. I.; Wheeler, D.; Eldridge, J.; Baranwal, R.; Dickerson, R.

1996-01-01

Polymeric precursors to Si-C-O, SI-B-N and Si-C were evaluated for use as ceramic interfaces in ceramic matrix composites. Use of the preceramic polymers allows for easy dip coating of fibers from dilute solutions of a polymer, which are then pyrolyzed to obtain the ceramic. SCS-0 fibers (Textron Specialty Materials, Lowell, MA) were coated with polymers from three systems: polysilsesquioxanes, polyborosilazanes and polycarbosilanes. The polysilsesquioxane systems were shown to produce either silicon oxycarbide or silicon oxynitride, depending on the pyrolysis conditions, and demonstrated some promise in an RBSN (reaction-bonded silicon nitride) matrix model system. Polyborosilazanes were shown, in studies of bulk polymers, to give rise to oxidation resistant Si-B-N ceramics which remain amorphous to temperatures of 1600 C, and should therefore provide a low modulus interface. Polycarbosilanes produce amorphous carbon-rich Si-C materials which have demonstrated oxidation resistance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

Nonlinear Layer-by-Layer Films: Effects of Chain Diffusivity on Film Structure and Swelling

DOE PAGES

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

2017-08-09

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

Association behaviors of dodecyltrimethylammonium bromide with double hydrophilic block co-polymer poly(ethylene glycol)-block-poly(glutamate sodium).

PubMed

Han, Yuchun; Xia, Lin; Zhu, Linyi; Zhang, Shusheng; Li, Zhibo; Wang, Yilin

2012-10-30

The association behaviors of single-chain surfactant dodecyltrimethylammonium bromide (DTAB) with double hydrophilic block co-polymers poly(ethylene glycol)-b-poly(sodium glutamate) (PEG(113)-PGlu(50) or PEG(113)-PGlu(100)) were investigated using isothermal titration microcalorimetry, cryogenic transmission electron microscopy, circular dichroism, ζ potential, and particle size measurements. The electrostatic interaction between DTAB and the oppositely charged carboxylate groups of PEG-PGlu induces the formation of super-amphiphiles, which further self-assemble into ordered aggregates. Dependent upon the charge ratios between DTAB and the glutamic acid residue of the co-polymer, the mixture solutions can change from transparent to opalescent without precipitation. Dependent upon the chain length of the PGlu block, the mixture of DTAB and PEG-PGlu diblocks can form two different aggregates at their corresponding electroneutral point. Spherical and rod-like aggregates are formed in the PEG(113)-PGlu(50)/DTAB mixture, while the vesicular aggregates are observed in the PEG(113)-PGlu(100)/DTAB mixture solution. Because the PEG(113)-PGlu(100)/DTAB super-amphiphile has more hydrophobic components than that of the PEG(113)-PGlu(50)/DTAB super-amphiphile, the former prefers forming the ordered aggregates with higher curvature, such as spherical and rod aggregates, but the latter prefers forming vesicular aggregates with lower curvature.

Composite membranes, methods of making same, and applications of same

DOEpatents

Pintauro, Peter N.; Park, Andrew; Ballengee, Jason

2016-05-24

In one aspect of the present invention, a method of fabricating a composite membrane includes: forming a first polymer solution from a first polymer and a second polymer solution from a second polymer, respectively, where the first polymer includes a charged polymer and the second polymer includes an uncharged polymer; electrospinning, separately and simultaneously, the first and second polymer solutions to form a dual fiber mat with first polymer fibers and second polymer fibers; and processing the dual fiber mat by softening and flowing one of the first or second polymer fibers to fill in the void space between the other of the first and second polymer fibers so as to form the composite membrane. In some embodiments, the composite membrane may be a proton exchange membrane (PEM) or an anion exchange membrane (AEM).

Nanopore detection of DNA molecules in crowded neutral polymer solutions

NASA Astrophysics Data System (ADS)

Sharma, Rajesh Kumar; Dai, Liang; Doyle, Patrick; Garaj, Slaven

Nanopore sensing is a precise technique for analysis of the structure and dynamics of individual biomolecules in different environments, and has even become a prominent technique for next-gen DNA sequencing. In the nanopore sensor, an individual DNA molecule is electrophoretically translocated through a single, nanometer-scaled pore in a solid-state membrane separating two chambers filled with electrolyte. The conformation of the molecule is deduced from modulations in the ionic current through the pore during the translocation event. Using nanopores, we investigated the dynamics of the DNA molecules in a crowded solution of neutral polymers of different sizes and concentrations. The translocation dynamics depends significantly on the size and concentration of the polymers, as different contributions to the electrophoretic and entropic forces on the DNA molecules come into play. This setup offers an excellent, tuneable model-system for probing biologically relevant questions regarding the behaviour of DNA molecules in highly confined and crowded environments. Singapore-MIT Alliance for Research and Technology.

Early turbulence in von Karman swirling flow of polymer solutions

NASA Astrophysics Data System (ADS)

Burnishev, Yuri; Steinberg, Victor

2015-01-01

We present quantitative experimental results on the transition to early turbulence in von Karman swirling flow of water- and water-sugar-based polymer solutions compared to the transition to turbulence in their Newtonian solvents by measurements of solely global quantities as torque Γ(t) and pressure p(t) with large statistics as a function of Re. For the first time the transition values of Re_c\\textit{turb} to fully developed turbulence and turbulent drag reduction regime Re_c\\textit{TDR} are obtained as functions of elasticity El by using the solvents with different viscosities and polymer concentrations ϕ. Two scaling regions for fundamental turbulent characteristics are identified and they correspond to the turbulent and TDR regimes. Both Re_c\\textit{turb} and Re_c\\textit{TDR} are found via the dependence of the friction coefficient Cf and Cp, defined through scaled average torque \\barΓ and rms pressure fluctuations p\\textit{rms} , respectively, on Re for different El and ϕ and via the limits of the two scaling regions.

Interaction between xanthan gum and cationic cellulose JR400 in aqueous solution.

PubMed

Li, Haiping; Hou, Wanguo; Li, Xiuzhi

2012-06-05

The electrostatic and hydrogen bonding interactions between xanthan gum (XG) and semisynthetic cationic cellulose (JR400) in aqueous solution are investigated via stability map, FT-IR spectra, thermogravimetric analysis, potentiometric measurement and rheological method. The stability map shows three regions, a stable region with XG as the major component, a flocculated region and another stable region with JR400 as the major component. The stability of mixing system depends on both the concentration fraction of JR400 (fJR) and the overlapping concentrations of these two polymers. In the region near the stoichiometric fJR, the mixture shows stoichiometric flocculation, which is independent of the total polymer concentration. However, in the regions away from the stoichiometric fJR, the mixtures are stable when the concentration of major polymer component is higher than its overlapping concentration. In stable regions, the electrostatic and hydrogen bonding interactions can enhance the viscosity of mixing system at appropriate fJR values. Copyright © 2012 Elsevier Ltd. All rights reserved.

Smart membranes: Hydroxypropyl cellulose for flavor delivery

NASA Astrophysics Data System (ADS)

Heitfeld, Kevin A.

2007-12-01

This work focuses on the use of temperature responsive gels (TRGs) (polymeric hydrogels with a large temperature-dependent change in volume) for flavor retention at cooking temperatures. Specifically, we have studied a gel with a lower critical solution temperature (LCST) that swells at low temperatures and collapses at high temperatures. In the collapsed state, the polymer acts as a transport barrier, keeping the volatile flavors inside. An encapsulation system was designed to utilize the solution (phase separation) behavior of a temperature responsive gel. The gel morphology was understood and diffusive properties were tailored through morphology manipulation. Heterogeneous and homogeneous gels were processed by understanding the effect of temperature on gel morphology. A morphology model was developed linking bulk diffusive properties to molecular morphology. Flavor was encapsulated within the gel and the emulsifying capability was determined. The capsules responded to temperature similarly to the pure polymer. The release kinetcs were compared to commercial gelatin capsules and the temperature responsive polymer took longer to release.

Shock wave emission from laser-induced cavitation bubbles in polymer solutions.

PubMed

Brujan, Emil-Alexandru

2008-09-01

The role of extensional viscosity on the acoustic emission from laser-induced cavitation bubbles in polymer solutions and near a rigid boundary is investigated by acoustic measurements. The polymer solutions consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose (CMC) aqueous solution with a weak elastic component. A reduction of the maximum amplitude of the shock wave pressure and a prolongation of the oscillation period of the bubble were found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. In both polymer solutions, however, the shock pressure decays proportionally to r(-1) with increasing distance r from the emission centre.

Impact of heat treatment on the physical properties of noncrystalline multisolute systems concentrated in frozen aqueous solutions.

PubMed

Izutsu, Ken-ichi; Yomota, Chikako; Kawanishi, Toru

2011-12-01

The purpose of this study was to elucidate the effect of heat treatment on the miscibility of multiple concentrated solutes that mimic biopharmaceutical formulations in frozen solutions. The first heating thermal analysis of frozen solutions containing either a low-molecular-weight saccharide (e.g., sucrose, trehalose, and glucose) or a polymer (e.g., polyvinylpyrrolidone and dextran) and their mixtures from -70°C showed a single transition at glass transition temperature of maximally freeze-concentrated solution (T(g) ') that indicated mixing of the freeze-concentrated multiple solutes. The heat treatment of single-solute and various polymer-rich mixture frozen solutions at temperatures far above their T(g) ' induced additional ice crystallization that shifted the transitions upward in the following scan. Contrarily, the heat treatment of frozen disaccharide-rich solutions induced two-step heat flow changes (T(g) ' splitting) that suggested separation of the solutes into multiple concentrated noncrystalline phases, different in the solute compositions. The extent of the T(g) ' splitting depended on the heat treatment temperature and time. Two-step glass transition was observed in some sucrose and dextran mixture solids, lyophilized after the heat treatment. Increasing mobility of solute molecules during the heat treatment should allow spatial reordering of some concentrated solute mixtures into thermodynamically favorable multiple phases. Copyright © 2011 Wiley-Liss, Inc.

Influence of Weak Base Addition to Hole-Collecting Buffer Layers in Polymer:Fullerene Solar Cells.

PubMed

Seo, Jooyeok; Park, Soohyeong; Song, Myeonghun; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo

2017-02-09

We report the effect of weak base addition to acidic polymer hole-collecting layers in normal-type polymer:fullerene solar cells. Varying amounts of the weak base aniline (AN) were added to solutions of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The acidity of the aniline-added PEDOT:PSS solutions gradually decreased from pH = 1.74 (AN = 0 mol% ) to pH = 4.24 (AN = 1.8 mol %). The electrical conductivity of the PEDOT:PSS-AN films did not change much with the pH value, while the ratio of conductivity between out-of-plane and in-plane directions was dependent on the pH of solutions. The highest power conversion efficiency (PCE) was obtained at pH = 2.52, even though all devices with the PEDOT:PSS-AN layers exhibited better PCE than those with the pristine PEDOT:PSS layers. Atomic force microscopy investigation revealed that the size of PEDOT:PSS domains became smaller as the pH increased. The stability test for 100 h illumination under one sun condition disclosed that the PCE decay was relatively slower for the devices with the PEDOT:PSS-AN layers than for those with pristine PEDOT:PSS layers.

Method of solution preparation of polyolefin class polymers for electrospinning processing included

NASA Technical Reports Server (NTRS)

Rabolt, John F. (Inventor); Givens, Steven R. (Inventor); Lee, Keun-Hyung (Inventor)

2011-01-01

A process to make a polyolefin fiber which has the following steps: mixing at least one polyolefin into a solution at room temperature or a slightly elevated temperature to form a polymer solution and electrospinning at room temperature said polymer solution to form a fiber.

Dynamics of Nanoparticles in Entangled Polymer Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, Pooja; Mangal, Rahul; Kohle, Ferdinand

The mean square displacement < r 2 > of nanoparticle probes dispersed in simple isotropic liquids and in polymer solutions is interrogated using fluorescence correlation spectroscopy and single-particle tracking (SPT) experiments. Probe dynamics in different regimes of particle diameter (d), relative to characteristic polymer length scales, including the correlation length (ξ), the entanglement mesh size (a), and the radius of gyration (R g), are investigated. In simple fluids and for polymer solutions in which d >> R g, long-time particle dynamics obey random-walk statistics < r 2 >:t, with the bulk zero-shear viscosity of the polymer solution determining the frictionalmore » resistance to particle motion. In contrast, in polymer solutions with d < R g, polymer molecules in solution exert noncontinuum resistances to particle motion and nanoparticle probes appear to interact hydrodynamically only with a local fluid medium with effective drag comparable to that of a solution of polymer chain segments with sizes similar to those of the nanoparticle probes. Under these conditions, the nanoparticles exhibit orders of magnitude faster dynamics than those expected from continuum predictions based on the Stokes–Einstein relation. SPT measurements further show that when d > a, nanoparticle dynamics transition from diffusive to subdiffusive on long timescales, reminiscent of particle transport in a field with obstructions. This last finding is in stark contrast to the nanoparticle dynamics observed in entangled polymer melts, where X-ray photon correlation spectroscopy measurements reveal faster but hyperdiffusive dynamics. As a result, we analyze these results with the help of the hopping model for particle dynamics in polymers proposed by Cai et al. and, on that basis, discuss the physical origins of the local drag experienced by the nanoparticles in entangled polymer solutions.« less

Dynamics of Nanoparticles in Entangled Polymer Solutions

DOE PAGES

Nath, Pooja; Mangal, Rahul; Kohle, Ferdinand; ...

2017-12-01

The mean square displacement < r 2 > of nanoparticle probes dispersed in simple isotropic liquids and in polymer solutions is interrogated using fluorescence correlation spectroscopy and single-particle tracking (SPT) experiments. Probe dynamics in different regimes of particle diameter (d), relative to characteristic polymer length scales, including the correlation length (ξ), the entanglement mesh size (a), and the radius of gyration (R g), are investigated. In simple fluids and for polymer solutions in which d >> R g, long-time particle dynamics obey random-walk statistics < r 2 >:t, with the bulk zero-shear viscosity of the polymer solution determining the frictionalmore » resistance to particle motion. In contrast, in polymer solutions with d < R g, polymer molecules in solution exert noncontinuum resistances to particle motion and nanoparticle probes appear to interact hydrodynamically only with a local fluid medium with effective drag comparable to that of a solution of polymer chain segments with sizes similar to those of the nanoparticle probes. Under these conditions, the nanoparticles exhibit orders of magnitude faster dynamics than those expected from continuum predictions based on the Stokes–Einstein relation. SPT measurements further show that when d > a, nanoparticle dynamics transition from diffusive to subdiffusive on long timescales, reminiscent of particle transport in a field with obstructions. This last finding is in stark contrast to the nanoparticle dynamics observed in entangled polymer melts, where X-ray photon correlation spectroscopy measurements reveal faster but hyperdiffusive dynamics. As a result, we analyze these results with the help of the hopping model for particle dynamics in polymers proposed by Cai et al. and, on that basis, discuss the physical origins of the local drag experienced by the nanoparticles in entangled polymer solutions.« less

Synthesis and phase behavior of end-functionalized associating polymers

NASA Astrophysics Data System (ADS)

Wrue, Michelle H.

We have explored polymer blend phase behavior in the presence of multiple hydrogen bonding end-groups. This work details the synthesis of functionalized polymers and their subsequent use in miscibility studies. The synthesis of end-functionalized hydrogen bonding polymers and the investigation of their physical properties and miscibility is presented. Mono-functional and telechelic ureidopyrimidinone (UPy) functionalized polymers were prepared by two main routes: post-polymerization functionalization (of commercially available or synthesized polymers); and polymerization of monomers using a functionalized initiator. UPy-functionalized polymers were prepared with a variety of polymer backbones including poly(ethylene oxide)s; poly(butadiene)s, poly(dimethyl siloxanxe)s; poly(styrene)s and poly(methyl methacrylate)s. The most successful route to polymers with UPy end-groups was atom transfer radical polymerization (ATRP) using a UPy-functionalized initiator, followed by atom transfer radical coupling (ATRC). The incorporation of ureidopyrimidinone end-groups was shown to affect the physical properties of the polymer backbone. Parent polymers that were liquids became viscous liquids or waxy solids upon UPy-functionalization of chain end. UPy-functionalization of a hydroxyl-terminated polybutadiene (HO-PB-OH) resulted in a waxy solid while the HO-PB-OH precursor was a viscous liquid. The thermal properties of functionalized polymers also differed from those of the unfunctionalized parent polymers. Hot-stage optical microscopy revealed that UPy-functionalized PEO displayed a depressed melting point relative to the analogous unfunctionalized precursor. Differential scanning calorimetry was also used to investigate the synthesized UPy-polymers. UPy-functionalized polystyrenes and poly(methyl methacrylate)s showed an increased T g compared to the equivalent homopolymer standards. This increased Tg was determined to be dependent upon the fraction of UPy groups present and chemical cleavage of the end-groups resulted in Tgs near those observed for polymer standards of comparable molecular weight. Aggregation of UPy end-groups in solution was observed using gel permeation chromatography. Aggregation was only observed for telechelic samples of low molecular weight, indicating that the aggregation of end-groups is dependent upon the concentration of the end-groups. The effect of UPy end-groups on blend miscibility was studied in solution using laser light scattering and in the melt state was using laser light scattering, optical microscopy and differential scanning calorimetry. The incorporation of associating groups onto one end of either blend component decreases miscibility relative to unfunctionalized parent blends. Lower miscibility was also observed for blends in which both components were mono-functionalized with associating end-groups. The largest decrease in miscibility was observed for blends containing telechelic UPy-functionalized polymers, which were immiscible across the entire composition range.

Thermoresponsive N-alkoxyalkylacrylamide polymers as a sieving matrix for high-resolution DNA separations on a microfluidic chip

PubMed Central

Root, Brian E.; Hammock, Mallory L.; Barron, Annelise E.

2012-01-01

In recent years, there has been an increasing demand for a wide range of DNA separations that require the development of materials to meet the needs of high resolution and high throughput. Here, we demonstrate the use of thermoresponsive N-alkoxyalkylacrylamide polymers as a sieving matrix for DNA separations on a microfluidic chip. The viscosities of the N-alkoxyalkylacrylamide polymers are more than an order of magnitude lower than that of a linear polyacrylamide of corresponding molecular weight, allowing rapid loading of the microchip. At 25 °C, N-alkoxyalkylacrylamide polymers can provide improved DNA separations compared to LPA in terms of reduced separation time and increased separation efficiency, particularly for the larger DNA fragments. The improved separation efficiency in N-alkoxyalkylacrylamide polymers is attributed to the peak widths increasing only slightly with DNA fragment size, while the peak widths increase appreciably above 150 bp using an LPA matrix. Upon elevating the temperature to 50 °C, the increase in viscosity of the N-alkoxyalkylacrylamide solutions is dependent upon their overall degree of hydrophobicity. The most hydrophobic polymers exhibit an LCST below 50 °C, undergoing a coil-to-globule transition followed by chain aggregation. DNA separation efficiency at 50 °C therefore decreases significantly with increasing hydrophobic character of the polymers, and no separations were possible with solutions with an LCST below 50 °C. The work reported here demonstrates the potential for this class of polymer to be used for applications such as PCR product and RFLP sizing, and provides insight into the effect of polymer hydrophobicity on DNA separations. PMID:19053065

Accurate coarse-grained models for mixtures of colloids and linear polymers under good-solvent conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

D’Adamo, Giuseppe, E-mail: giuseppe.dadamo@sissa.it; Pelissetto, Andrea, E-mail: andrea.pelissetto@roma1.infn.it; Pierleoni, Carlo, E-mail: carlo.pierleoni@aquila.infn.it

2014-12-28

A coarse-graining strategy, previously developed for polymer solutions, is extended here to mixtures of linear polymers and hard-sphere colloids. In this approach, groups of monomers are mapped onto a single pseudoatom (a blob) and the effective blob-blob interactions are obtained by requiring the model to reproduce some large-scale structural properties in the zero-density limit. We show that an accurate parametrization of the polymer-colloid interactions is obtained by simply introducing pair potentials between blobs and colloids. For the coarse-grained (CG) model in which polymers are modelled as four-blob chains (tetramers), the pair potentials are determined by means of the iterative Boltzmannmore » inversion scheme, taking full-monomer (FM) pair correlation functions at zero-density as targets. For a larger number n of blobs, pair potentials are determined by using a simple transferability assumption based on the polymer self-similarity. We validate the model by comparing its predictions with full-monomer results for the interfacial properties of polymer solutions in the presence of a single colloid and for thermodynamic and structural properties in the homogeneous phase at finite polymer and colloid density. The tetramer model is quite accurate for q ≲ 1 (q=R{sup ^}{sub g}/R{sub c}, where R{sup ^}{sub g} is the zero-density polymer radius of gyration and R{sub c} is the colloid radius) and reasonably good also for q = 2. For q = 2, an accurate coarse-grained description is obtained by using the n = 10 blob model. We also compare our results with those obtained by using single-blob models with state-dependent potentials.« less

COUPLING THE ALKALINE-SURFACTANT-POLYMER TECHNOLOGY AND THE GELATION TECHNOLOGY TO MAXIMIZE OIL PRODUCTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-04-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or more efficient areal sweep efficiency for those with high permeability contrast ''thief zones''. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or those with thief zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. A priormore » fluid-fluid report discussed interaction of different gel chemical compositions and alkaline-surfactant-polymer solutions. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses. Aluminum-polyacrylamide, flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9. Chromium acetate-polyacrylamide flowing and rigid flowing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid flowing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid flowing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid flowing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. None of the gels tested appeared to alter alkaline-surfactant-polymer solution oil recovery. Total waterflood plus chemical flood oil recovery sequence recoveries were all similar.« less

Nanoprobe diffusion in entangled polymer solutions: Linear vs. unconcatenated ring chains

NASA Astrophysics Data System (ADS)

Nahali, Negar; Rosa, Angelo

2018-05-01

We employ large-scale molecular dynamics computer simulations to study the problem of nanoprobe diffusion in entangled solutions of linear polymers and unknotted and unconcatenated circular (ring) polymers. By tuning both the diameter of the nanoprobe and the density of the solution, we show that nanoprobes of diameter smaller than the entanglement distance (tube diameter) of the solution display the same (Rouse-like) behavior in solutions of both polymer architectures. Instead, nanoprobes with larger diameters appear to diffuse markedly faster in solutions of rings than in solutions of linear chains. Finally, by analysing the distribution functions of spatial displacements, we find that nanoprobe motion in rings' solutions shows both Gaussian and ergodic behaviors, in all regimes considered, while, in solutions of linear chains, nanoprobes exceeding the size of the tube diameter show a transition to non-Gaussian and non-ergodic motion. Our results emphasize the role of chain architecture in the motion of nanoprobes dispersed in polymer solutions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Surface interaction forces of cellulose nanocrystals grafted with thermoresponsive polymer brushes.

PubMed

Zoppe, Justin O; Osterberg, Monika; Venditti, Richard A; Laine, Janne; Rojas, Orlando J

2011-07-11

The colloidal stability and thermoresponsive behavior of poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals (CNCs) of varying graft densities and molecular weights was investigated. Indication of the grafted polymer brushes was obtained after AFM imaging of CNCs adsorbed on silica. Also, aggregation of the nanoparticles carrying grafts of high degree of polymerization was observed. The responsiveness of grafted CNCs in aqueous dispersions and as an ultrathin film was evaluated by using light scattering, viscosimetry, and colloidal probe microscopy (CPM). Light transmittance measurements showed temperature-dependent aggregation originating from the different graft densities and molecular weights. The lower critical solution temperature (LCST) of grafted poly(NiPAAm) brushes was found to decrease with the ionic strength, as is the case for free poly(NiPAAm) in aqueous solution. Thermal responsive behavior of grafted CNCs in aqueous dispersions was observed by a sharp increase in dispersion viscosity as the temperature approached the LCST. CPM in liquid media for asymmetric systems consisting of ultrathin films of CNCs and a colloidal silica probe showed the distinctive effects of the grafted polymer brushes on interaction and adhesive forces. The origin of such forces was found to be mainly electrostatic and steric in the case of bare and grafted CNCs, respectively. A decrease in the onset of attractive and adhesion forces of grafted CNCs films were observed with the ionic strength of the aqueous solution. The decreased mobility of polymer brushes upon partial collapse and decreased availability of hydrogen bonding sites with higher electrolyte concentration were hypothesized as the main reasons for the less prominent polymer bridging between interacting surfaces.

A new method to simulate the effects of viscous fingering on miscible displacement processes in porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vossoughi, S.; Green, D.W.; Smith, J.E.

Dispersion and viscous fingering are important parameters in miscible displacement. Effects of dispersion on concentration profiles in porous media can be simulated when the viscosity ratio is favorable. The capability to simulate viscous fingering is limited. This paper presents a new method to simulate effects of viscous fingering on miscible displacement processes in porous media. The method is based on the numerical solution of a general form of the convection-dispersion equation. In this equation the convection term is represented by a fractional flow function. The fractional flow function is derived from Darcy's law by using a concentration-dependent average viscosity andmore » relative flow area to each fluid at any point in the bed. The method was extended to the description of a polymer flood by including retention and inaccessible PV. A Langmuir-type model for polymer retention in the rock was used. The resulting convection-dispersion equation for displacement by polymer was solved numerically by the use of a finite-element method with linear basis functions and Crank-Nicholson derivative approximation. History matches were performed on four sets of laboratory data to verify the model: (1) an unfavorable viscosity ratio displacement, (2) stable displacement of glycerol by polymer solution, (3) unstable displacement of brine by a slug of polymer solution, and (4) a favorable viscosity ratio displacement. In general, computed results from the model matched laboratory data closely. Good agreement of the model with experiments over a significant range of variables lends support to the analysis.« less

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices.

PubMed

Yang, Qing-Dan; Li, Ho-Wa; Cheng, Yuanhang; Guan, Zhiqiang; Liu, Taili; Ng, Tsz-Wai; Lee, Chun-Sing; Tsang, Sai-Wing

2016-03-23

Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy. Using this approach, we find that some of the BHJ blends simply follow vacuum level alignment, but others show strong energy level shifting as a result of Fermi level pinning. Independently, by measuring the temperature-dependent open-circuit voltage (VOC), we find that the effective energy gap (Eeff), the energy difference between the highest occupied molecular orbital of the polymer donor (EHOMO-D) and lowest unoccupied molecular orbital of the PCBM acceptor (ELUMO-A), obtained by photoemission spectroscopy in all polymer:PCBM blends has an excellent agreement with the extrapolated VOC at 0 K. Consequently, the photovoltage loss of various organic BHJ photovoltaic devices at room temperature is in a range of 0.3-0.6 V. It is believed that the demonstrated direct measurement approach of the energy level alignment in solution-processed organic BHJ will bring deeper insight into the origin of the VOC and the corresponding photovoltage loss mechanism in organic photovoltaic cells.

Designing Solvent Exchange-Induced In Situ Forming Gel from Aqueous Insoluble Polymers as Matrix Base for Periodontitis Treatment.

PubMed

Srichan, Tharatree; Phaechamud, Thawatchai

2017-01-01

An in situ forming gel is a dosage form which is promised for site-specific therapy such as periodontal pocket of periodontitis treatment. Ethylcellulose, bleached shellac, and Eudragit RS were applied in this study as a polymeric matrix for in situ forming gel employing N-methyl pyrrolidone (NMP) as solvent. Solutions comprising ethylcellulose, bleached shellac, and Eudragit RS in NMP were evaluated for viscosity, rheology, and rate of water penetration. Ease of administration by injection was determined as the force required to expel polymeric solutions through a needle using texture analyzer. In vitro gel formation and in vitro gel degradation were conducted after injection into phosphate buffer solution pH 6.8. Ethylcellulose, bleached shellac, and Eudragit RS could form the in situ gel, in vitro. Gel viscosity and pH value depended on percentage amount of the polymer, whereas the water diffusion at early period likely relied on types of polymer. Furthermore, the solutions containing higher polymer concentration exhibited the lower degree of degradation. All the preparations were acceptable as injectable dosage forms because the applied force was lower than 50 N. All of them inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyrommonas gingivalis growth owing to antimicrobial activity of NMP which exhibited a potential use for periodontitis treatment. Moreover, the developed systems presented as the solvent exchange induced in situ forming gel and showed capability to be incorporated with the suitable antimicrobial active compounds for periodontitis treatment which should be further studied.

Modification of vortex ring formation using dilute polymer solution

NASA Astrophysics Data System (ADS)

Jordan, Daniel; Krane, Michael; Peltier, Joel; Patterson, Eric; Fontaine, Arnold

2006-11-01

This talk will present the results of an experimental study to determine the effect of dilute polymer solution on the formation of a vortex ring. Experiments were conducted in a large, glass tank, filled with water. Vortex rings were produced by injecting a slug of dilute polymer solution into the tank through a nozzle. The injection was controlled by a prescribed piston motion in the nozzle. For the same piston motion, vortex rings were produced for 3 concentrations of the polymer solution, including one with no polymer. The vortex ring flowfield was measured using DPIV. Differences between the 3 cases of polymer concentration in vortex ring formation time, circulation, size, and convection speed are presented.

Intrachain exciton dynamics in conjugated polymer chains in solution.

PubMed

Tozer, Oliver Robert; Barford, William

2015-08-28

We investigate exciton dynamics on a polymer chain in solution induced by the Brownian rotational motion of the monomers. Poly(para-phenylene) is chosen as the model system and excitons are modeled via the Frenkel exciton Hamiltonian. The Brownian fluctuations of the torsional modes were modeled via the Langevin equation. The rotation of monomers in polymer chains in solution has a number of important consequences for the excited state properties. First, the dihedral angles assume a thermal equilibrium which causes off-diagonal disorder in the Frenkel Hamiltonian. This disorder Anderson localizes the Frenkel exciton center-of-mass wavefunctions into super-localized local exciton ground states (LEGSs) and higher-energy more delocalized quasi-extended exciton states (QEESs). LEGSs correspond to chromophores on polymer chains. The second consequence of rotations-that are low-frequency-is that their coupling to the exciton wavefunction causes local planarization and the formation of an exciton-polaron. This torsional relaxation causes additional self-localization. Finally, and crucially, the torsional dynamics cause the Frenkel Hamiltonian to be time-dependent, leading to exciton dynamics. We identify two distinct types of dynamics. At low temperatures, the torsional fluctuations act as a perturbation on the polaronic nature of the exciton state. Thus, the exciton dynamics at low temperatures is a small-displacement diffusive adiabatic motion of the exciton-polaron as a whole. The temperature dependence of the diffusion constant has a linear dependence, indicating an activationless process. As the temperature increases, however, the diffusion constant increases at a faster than linear rate, indicating a second non-adiabatic dynamics mechanism begins to dominate. Excitons are thermally activated into higher energy more delocalized exciton states (i.e., LEGSs and QEESs). These states are not self-localized by local torsional planarization. During the exciton's temporary occupation of a LEGS-and particularly a quasi-band QEES-its motion is semi-ballistic with a large group velocity. After a short period of rapid transport, the exciton wavefunction collapses again into an exciton-polaron state. We present a simple model for the activated dynamics which is in agreement with the data.

Relating hydrogen-bonding interactions with the phase behavior of naproxen/PVP K 25 solid dispersions: evaluation of solution-cast and quench-cooled films.

PubMed

Paudel, Amrit; Nies, Erik; Van den Mooter, Guy

2012-11-05

In this work, we investigated the relationship between various intermolecular hydrogen-bonding (H-bonding) interactions and the miscibility of the model hydrophobic drug naproxen with the hydrophilic polymer polyvinylpyrrolidone (PVP) across an entire composition range of solid dispersions prepared by quasi-equilibrium film casting and nonequilibrium melt quench cooling. The binary phase behavior in solid dispersions exhibited substantial processing method dependence. The solid state solubility of crystalline naproxen in PVP to form amorphous solid dispersions was 35% and 70% w/w naproxen in solution-cast films and quench-cooled films, respectively. However, the presence of a single mixed phase glass transition indicated the amorphous miscibility to be 20% w/w naproxen for the films, beyond which amorphous-amorphous and/or crystalline phase separations were apparent. This was further supported by the solution state interactions data such as PVP globular size distribution and solution infrared spectral profiles. The borderline melt composition showed cooling rate dependence of amorphization. The glass transition and melting point depression profiles of the system were treated with the analytical expressions based on Flory-Huggins mixing theory to interpolate the equilibrium solid solubility. FTIR analysis and subsequent spectral deconvolution revealed composition and miscibility dependent variations in the strength of drug-polymer intermolecular H-bonding. Two types of H-bonded populations were evidenced from 25% w/w and 35% w/w naproxen in solution-cast films and quench-cooled films, respectively, with the higher fraction of strongly H-bonded population in the drug rich domains of phase separated amorphous film compositions and highly drug loaded amorphous quench-cooled dispersions.

Porous fiber formation in polymer-solvent system undergoing solvent evaporation

NASA Astrophysics Data System (ADS)

Dayal, Pratyush; Kyu, Thein

2006-08-01

Temporal evolution of the fiber morphology during dry spinning has been investigated in the framework of Cahn-Hilliard equation [J. Chem. Phys. 28, 258 (1958)] pertaining to the concentration order parameter or volume fraction given by the Flory-Huggins free energy of mixing [P. J. Flory, Principles of Polymer Chemistry (Cornell University Press, Ithaca, NY, 1953), p. 672] in conjunction with the solvent evaporation rate. To guide the solvent evaporation induced phase separation, equilibrium phase diagram of the starting polymer solution was established on the basis of the Flory-Huggins free energy of mixing. The quasi-steady-state approximation has been adopted to account for the nonconserved nature of the concentration field caused by the solvent loss. The process of solvent evaporation across the fiber skin-air interface was treated in accordance with the classical Fick's law [R. B. Bird et al., Transport Phenomena (J. Wiley, New York, 1960), p. 780]. The simulated morphologies include gradient type, hollow fiber type, bicontinuous type, and host-guest type. The development of these diverse fiber morphologies is explicable in terms of the phase diagram of the polymer solution in a manner dependent on the competition between the phase separation dynamics and rate of solvent evaporation.

Structural dependence of MEH-PPV chromism in solution.

PubMed

de Magalhães, Carlos E T; Savedra, Ranylson M L; Dias, Karina S; Ramos, Rodrigo; Siqueira, Melissa F

2017-03-01

The chromism observed in the MEH-PPV polymer in tetrahydrofuran (THF) solution is discussed as a function of the structural morphology of the backbone chains. To evaluate this phenomenon, we carried out simulations employing a hybrid methodology using molecular dynamics and quantum mechanical approaches. Our results support the hypothesis that the morphological order-disorder transition is related to the change from red to blue phase observed experimentally. The morphological disorder is associated with total or partial twisted arrangements in the polymer backbone, which induces an electronic conjugation length more confined to shorter segments. In addition, the main band of the MEH-PPV UV-Vis spectrum at the lower wavelength is related to the blue phase, in contrast to the red phase found for the more planar backbone chains.

Structural modification in the formation of starch - silver nanocomposites

NASA Astrophysics Data System (ADS)

Begum, S. N. Suraiya; Aswal, V. K.; Ramasamy, Radha Perumal

2016-05-01

Polymer based nanocomposites have gained wide applications in field of battery technology. Starch is a naturally occurring polysaccharide with sustainable properties such as biodegradable, non toxic, excellent film forming capacity and it also act as reducing agent for the metal nanoparticles. In our research various concentration of silver nitrate (AgNO3) was added to the starch solution and films were obtained using solution casting method. Surface electron microscope (SEM) of the films shows modifications depending upon the concentration of AgNO3. Small angle neutron scattering (SANS) analysis showed that addition of silver nitrate modifies the starch to disc like structures and with increasing the AgNO3 concentration leads to the formation of fractals. This research could benefit battery technology where solid polymer membranes using starch is used.

Manipulating Hydrophobic Interactions in Associative Polymer Solutions via Surfactant-Cyclodextrin Complexation

NASA Astrophysics Data System (ADS)

Talwar, Sachin; Harding, Jonathon; Khan, Saad A.

2008-07-01

Associative polymers in combination with cyclodextrin (CD) provide a potent tool to manipulate the solution rheology of aqueous solutions. In this study, we discuss the viability and scope of employing surfactants in such systems to facilitate a more versatile and effective tailoring of rheological properties. A model hydrophobically modified alkali-soluble emulsion (HASE) polymer is used which forms a transient physical network of intra- and inter-molecular hydrophobic junctions in solution arising from the interactions between hydrophobic groups grafted on the polymer backbone. The presence of these hydrophobic junctions significantly enhances the solution rheological properties with both the steady state viscosity and dynamic moduli exhibiting an increase by several orders of magnitude. The ability of nonionic surfactants to modulate and recover the hydrophobic interactions in these polymer solutions in the presence of cyclodextrin is examined. The presence of either a- or β-CD results in a dramatic decrease in viscosity and viscoelastic properties of the HASE polymer solution resulting from the encapsulation of polymer hydrophobes by CDs. Addition of nonionic surfactants to such systems promotes a competition between CDs and surfactant molecules to complex with polymer hydrophobes thereby altering the hydrophobic interactions. In this regard, nonylphenol ethoxylates (NPe) with different ethylene oxide (EO) chain lengths, which determine the surfactant hydrophilic-lipophilic balance (HLB), are used.

Hopping Diffusion of Nanoparticles in Polymer Matrices

PubMed Central

2016-01-01

We propose a hopping mechanism for diffusion of large nonsticky nanoparticles subjected to topological constraints in both unentangled and entangled polymer solids (networks and gels) and entangled polymer liquids (melts and solutions). Probe particles with size larger than the mesh size ax of unentangled polymer networks or tube diameter ae of entangled polymer liquids are trapped by the network or entanglement cells. At long time scales, however, these particles can diffuse by overcoming free energy barrier between neighboring confinement cells. The terminal particle diffusion coefficient dominated by this hopping diffusion is appreciable for particles with size moderately larger than the network mesh size ax or tube diameter ae. Much larger particles in polymer solids will be permanently trapped by local network cells, whereas they can still move in polymer liquids by waiting for entanglement cells to rearrange on the relaxation time scales of these liquids. Hopping diffusion in entangled polymer liquids and networks has a weaker dependence on particle size than that in unentangled networks as entanglements can slide along chains under polymer deformation. The proposed novel hopping model enables understanding the motion of large nanoparticles in polymeric nanocomposites and the transport of nano drug carriers in complex biological gels such as mucus. PMID:25691803

Confined dynamics of grafted polymer chains in solutions of linear polymer

DOE PAGES

Poling-Skutvik, Ryan D.; Olafson, Katy N.; Narayanan, Suresh; ...

2017-09-11

Here, we measure the dynamics of high molecular weight polystyrene grafted to silica nanoparticles dispersed in semidilute solutions of linear polymer. Structurally, the linear free chains do not penetrate the grafted corona but increase the osmotic pressure of the solution, collapsing the grafted polymer and leading to eventual aggregation of the grafted particles at high matrix concentrations. Dynamically, the relaxations of the grafted polymer are controlled by the solvent viscosity according to the Zimm model on short time scales. On longer time scales, the grafted chains are confined by neighboring grafted chains, preventing full relaxation over the experimental time scale.more » Adding free linear polymer to the solution does not affect the initial Zimm relaxations of the grafted polymer but does increase the confinement of the grafted chains. Finally, our results elucidate the physics underlying the slow relaxations of grafted polymer.« less

Confined dynamics of grafted polymer chains in solutions of linear polymer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poling-Skutvik, Ryan D.; Olafson, Katy N.; Narayanan, Suresh

Here, we measure the dynamics of high molecular weight polystyrene grafted to silica nanoparticles dispersed in semidilute solutions of linear polymer. Structurally, the linear free chains do not penetrate the grafted corona but increase the osmotic pressure of the solution, collapsing the grafted polymer and leading to eventual aggregation of the grafted particles at high matrix concentrations. Dynamically, the relaxations of the grafted polymer are controlled by the solvent viscosity according to the Zimm model on short time scales. On longer time scales, the grafted chains are confined by neighboring grafted chains, preventing full relaxation over the experimental time scale.more » Adding free linear polymer to the solution does not affect the initial Zimm relaxations of the grafted polymer but does increase the confinement of the grafted chains. Finally, our results elucidate the physics underlying the slow relaxations of grafted polymer.« less

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, Ronald F.; Brown, John D.

1996-01-01

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm.sup.3 and open porosity provided by well interconnected strut morphology is formed.

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1996-03-19

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam are disclosed. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm{sup 3} and open porosity provided by well interconnected strut morphology is formed.

Wrapping conformations of a polymer on a curved surface

NASA Astrophysics Data System (ADS)

Lin, Cheng-Hsiao; Tsai, Yan-Chr; Hu, Chin-Kun

2007-03-01

The conformation of a polymer on a curved surface is high on the agenda for polymer science. We assume that the free energy of the system is the sum of bending energy of the polymer and the electrostatic attraction between the polymer and surface. As is also assumed, the polymer is very stiff with an invariant length for each segment so that we can neglect its tensile energy and view its length as a constant. Based on the principle of minimization of free energy, we apply a variation method with a locally undetermined Lagrange multiplier to obtain a set of equations for the polymer conformation in terms of local geometrical quantities. We have obtained some numerical solutions for the conformations of the polymer chain on cylindrical and ellipsoidal surfaces. With some boundary conditions, we find that the free energy profiles of polymer chains behave differently and depend on the geometry of the surface for both cases. In the former case, the free energy of each segment distributes within a narrower range and its value per unit length oscillates almost periodically in the azimuthal angle. However, in the latter case the free energy distributes in a wider range with larger value at both ends and smaller value in the middle of the chain. The structure of a polymer wrapping around an ellipsoidal surface is apt to dewrap a polymer from the endpoints. The dependence of threshold lengths for a polymer on the initially anchored positions is also investigated. With initial conditions, the threshold wrapping length is found to increase with the electrostatic attraction strength for the ellipsoidal surface case. When a polymer wraps around a sphere surface, the threshold length increases monotonically with the radius without the self-intersection configuration for a polymer. We also discuss potential applications of the present theory to DNA/protein complex and further researches on DNA on the curved surface.

Electrical memory characteristics of a nondoped pi-conjugated polymer bearing carbazole moieties.

PubMed

Park, Samdae; Lee, Taek Joon; Kim, Dong Min; Kim, Jin Chul; Kim, Kyungtae; Kwon, Wonsang; Ko, Yong-Gi; Choi, Heungyeal; Chang, Taihyun; Ree, Moonhor

2010-08-19

Poly[bis(9H-carbazole-9-ethyl)dipropargylmalonate] (PCzDPM) is a novel pi-conjugated polymer bearing carbazole moieties that has been synthesized by polymerization of bis(9H-carbazole-9-ethyl)dipropargylmalonate with the aid of molybdenum chloride solution as the catalyst. This polymer is thermally stable up to 255 degrees C under a nitrogen atmosphere and 230 degrees C in air ambient; its glass-transition temperature is 147 or 128 degrees C, depending on the polymer chain conformation (helical or planar structure). The charge-transport characteristics of PCzDPM in nanometer-scaled thin films were studied as a function of temperature and film thickness. PCzDPM films with a thickness of 15-30 nm were found to exhibit very stable dynamic random access memory (DRAM) characteristics without polarity. Furthermore, the polymer films retain DRAM characteristics up to 180 degrees C. The ON-state current is dominated by Ohmic conduction, and the OFF-state current appears to undergo a transition from Ohmic to space-charge-limited conduction with a shallow-trap distribution. The ON/OFF switching of the devices is mainly governed by filament formation. The filament formation mechanism for the switching process is supported by the metallic properties of the PCzDPM film, which result in the temperature dependence of the ON-state current. In addition, the structure of this pi-conjugated polymer was found to vary with its thermal history; this change in structure can affect filament formation in the polymer film.

High energy density capacitors for low cost applications

NASA Astrophysics Data System (ADS)

Iyore, Omokhodion David

Polyvinylidene fluoride (PVDF) and its copolymers with trifluoroethylene, hexafluoropropylene and chlorotrifluoroethylene are the most widely investigated ferroelectric polymers, due to their relatively high electromechanical properties and potential to achieve high energy density. [Bauer, 2010; Zhou et al., 2009] The research community has focused primarily on melt pressed or extruded films of PVDF-based polymers to obtain the highest performance with energy density up to 25 Jcm-3. [Zhou et al., 2009] Solution processing offers an inexpensive, low temperature alternative, which is also easily integrated with flexible electronics. This dissertation focuses on the fabrication of solution-based polyvinylidene fluoride-hexafluoropropylene metal-insulator-metal capacitors on flexible substrates using a photolithographic process. Capacitors were optimized for maximum energy density, high dielectric strength and low leakage current density. It is demonstrated that with the right choice of solvent, electrodes, spin-casting and annealing conditions, high energy density thin film capacitors can be fabricated repeatably and reproducibly. The high electric field dielectric constants were measured and the reliabilities of the polymer capacitors were also evaluated via time-zero breakdown and time-dependent breakdown techniques. Chapter 1 develops the motivation for this work and provides a theoretical overview of dielectric materials, polarization, leakage current and dielectric breakdown. Chapter 2 is a literature review of polymer-based high energy density dielectrics and covers ferroelectric polymers, highlighting PVDF and some of its derivatives. Chapter 3 summarizes some preliminary experimental work and presents materials and electrical characterization that support the rationale for materials selection and process development. Chapter 4 discusses the fabrication of solution-processed PVDF-HFP and modification of its properties by photo-crosslinking. It is followed by a comparison of the structural, chemical and electrical properties of the neat and crosslinked films. Chapter 5 investigates the reliability and lifetime of PVDF-HFP thin films via time-zero and time-dependent dielectric breakdown. A power law relationship between the breakdown strength and characteristic breakdown time was determined, allowing extrapolation of lifetime at a desired operating voltage. The dissertation concludes with a summary and project outlook in chapter 7.

Boiling characteristics of dilute polymer solutions and implications for the suppression of vapor explosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, K.H.; Kim, M.H.

Quenching experiments of hot solid spheres in dilute aqueous solutions of polyethylene oxide polymer have been conducted for the purpose of investigating the physical mechanisms of the suppression of vapor explosions in this polymer solutions. Two spheres of 22.2mm and 9.5mm-diameter were tested in the polymer solutions of various concentrations at 30{degrees}C. Minimum film boiling temperature ({Delta}T{sub MFB}) in this highly-subcooled liquid rapidly decreased from over 700{degrees}c for pure water to about 150{degrees}C as the polymer concentration was increased up to 300ppm for 22.2mm sphere, and it decreased to 350{degrees}C for 9.5mm sphere. This rapid reduction of minimum film boilingmore » temperature in the PEO aqueous solutions can explain its ability of the suppression of spontaneous vapor explosions. The ability of suppression of vapor explosions by dilute polyethylene oxide solutions against an external trigger pressure was tested by dropping molten tin into the polymer solutions at 25{degrees}C. It was observed that in 50ppm solutions more mass fragmented than in pure water, but produced weaker explosion pressures. The explosion was completely suppressed in 300ppm solutions with the external trigger. The debris size distributions of fine fragments smaller than 0.7mm were shown almost identical regardless of the polymer concentrations.« less

Controlling Molecular Ordering in Solution-State Conjugated Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev

Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less

Controlling Molecular Ordering in Solution-State Conjugated Polymers

DOE PAGES

Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; ...

2015-07-17

Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less

Transport of organic solutes through amorphous teflon AF films.

PubMed

Zhao, Hong; Zhang, Jie; Wu, Nianqiang; Zhang, Xu; Crowley, Katie; Weber, Stephen G

2005-11-02

Fluorous media have great potential for selective extraction (e.g., as applied to organic synthesis). Fluorous polymer films would have significant advantages in fluorous separations. Stable films of Teflon AF 2400 were cast from solution. Films appear defect-free (SEM; AFM). Rigid aromatic solutes are transported (from chloroform solution to chloroform receiving phase) in a size-dependent manner (log permeability is proportional to -0.0067 times critical volume). Benzene's permeability is about 2 orders of magnitude higher than in comparable gas-phase experiments. The films show selectivity for fluorinated solutes in comparison to the hydrogen-containing control. Transport rates are dependent on the solvent making up the source and receiving phases. The effect of solvent is, interestingly, not due to changes in partition ratio, but rather it is due to changes in the solute diffusion coefficient in the film. Solvents plasticize the films. A less volatile compound, -COOH-terminated poly(hexafluoropropylene oxide) (4), plasticizes the films (T(g) = -40 degrees C). Permeabilities are decreased in comparison to 4-free films apparently because of decreased diffusivity of solutes. The slope of dependence of log permeability on critical volume is not changed, however.

Polymer waveguide based hybrid opto-electric integration technology

NASA Astrophysics Data System (ADS)

Mao, Jinbin; Deng, Lingling; Jiang, Xiyan; Ren, Rong; Zhai, Yumeng; Wang, Jin

2014-10-01

While monolithic integration especially based on InP appears to be quite an expensive solution for optical devices, hybrid integration solutions using cheaper material platforms are considered powerful competitors because of the high freedom of design, yield optimization and relative cost-efficiency. Among them, the polymer planar-lightwave circuit (PLC) technology is regarded attractive as polymer offers the potential of fairly simple and low-cost fabrication, and of low-cost packaging. In our work, polymer PLC was fabricated by using the standard reactive ion etching (RIE) technique, while other active and passive devices can be integrated on the polymer PLC platform. Exemplary polymer waveguide devices was a 13-channel arrayed waveguide grating (AWG) chip, where the central channel cross-talk was below -30dB and the polarization dependent frequency shift was mitigated by inserting a half wave plate. An optical 900 hybrid was also realized with one 2×4 multi-mode interferometer (MMI). The excess insertion losses are below 4dB for the C-band, while the transmission imbalance is below 1.2dB. When such an optical hybrid was integrated vertically with mesa-type photodiodes, the responsivity of the individual PD was around 0.06 A/W, while the 3 dB bandwidth reaches 24 ~ 27 GHz, which is sufficient for 100Gbit/s receivers. Another example of the hybrid integration was to couple the polymer waveguides to fiber by applying fiber grooves, whose typical loss value was 0.2 dB per-facet over a broad spectral range from 1200-1600 nm.

Surface design for controlled crystallization: the role of surface chemistry and nanoscale pores in heterogeneous nucleation.

PubMed

Diao, Ying; Myerson, Allan S; Hatton, T Alan; Trout, Bernhardt L

2011-05-03

Current industrial practice for control of primary nucleation (nucleation from a system without pre-existing crystalline matter) during crystallization from solution involves control of supersaturation generation, impurity levels, and solvent composition. Nucleation behavior remains largely unpredictable, however, due to the presence of container surfaces, dust, dirt, and other impurities that can provide heterogeneous nucleation sites, thus making the control and scale-up of processes that depend on primary nucleation difficult. To develop a basis for the rational design of surfaces to control nucleation during crystallization from solution, we studied the role of surface chemistry and morphology of various polymeric substrates on heterogeneous nucleation using aspirin as a model compound. Nucleation induction time statistics were utilized to investigate and quantify systematically the effectiveness of polymer substrates in inducing nucleation. The nucleation induction time study revealed that poly(4-acryloylmorpholine) and poly(2-carboxyethyl acrylate), each cross-linked by divinylbenzene, significantly lowered the nucleation induction time of aspirin while the other polymers were essentially inactive. In addition, we found the presence of nanoscopic pores on certain polymer surfaces led to order-of-magnitude faster aspirin nucleation rates when compared with surfaces without pores. We studied the preferred orientation of aspirin crystals on polymer films and found the nucleation-active polymer surfaces preferentially nucleated the polar facets of aspirin, guided by hydrogen bonds. A model based on interfacial free energies was also developed which predicted the same trend of polymer surface nucleation activities as indicated by the nucleation induction times.

Characterization of polymer adsorption onto drug nanoparticles using depletion measurements and small-angle neutron scattering.

PubMed

Goodwin, Daniel J; Sepassi, Shadi; King, Stephen M; Holland, Simon J; Martini, Luigi G; Lawrence, M Jayne

2013-11-04

Production of polymer and/or surfactant-coated crystalline nanoparticles of water-insoluble drugs (nanosuspensions) using wet bead milling is an important formulation approach to improve the bioavailability of said compounds. Despite the fact that there are a number of nanosuspensions on the market, there is still a deficiency in the characterization of these nanoparticles where further understanding may lead to the rational selection of polymer/surfactant. To this end small-angle neutron scattering (SANS) measurements were performed on drug nanoparticles milled in the presence of a range of polymers of varying molecular weight. Isotopic substitution of the aqueous solvent to match the scattering length density of the drug nanoparticles (i.e., the technique of contrast matching) meant that neutron scattering resulted only from the adsorbed polymer layer. The layer thickness and amount of hydroxypropylcellulose adsorbed on nabumetone nanoparticles derived from fitting the SANS data to both model-independent and model dependent volume fraction profiles were insensitive to polymer molecular weight over the range Mv = 47-112 kg/mol, indicating that the adsorbed layer is relatively flat but with tails extending up to approximately 23 nm. The constancy of the absorbed amount is in agreement with the adsorption isotherm determined by measuring polymer depletion from solution in the presence of the nanoparticles. Insensitivity to polymer molecular weight was similarly determined using SANS measurements of nabumetone or halofantrine nanoparticles stabilized with hydroxypropylmethylcellulose or poly(vinylpyrrolidone). Additionally SANS studies revealed the amount adsorbed, and the thickness of the polymer layer was dependent on both the nature of the polymer and drug particle surface. The insensitivity of the adsorbed polymer layer to polymer molecular weight has important implications for the production of nanoparticles, suggesting that lower molecular weight polymers should be used when preparing nanoparticles by wet bead milling since nanoparticle formation is more rapid but with no likely consequence on the resultant physical stability of the nanoparticles.

Compatibility Studies Of Blends Of PPG 4000 And PEG 4000 Using Viscosity Technique

NASA Astrophysics Data System (ADS)

Venkatramanan, K.; Arumugam, V.

2010-06-01

Certain properties of polymers can be enhanced by mixing it with another polymer. When two or more polymers are intimately mixed in a single continuous solid product, the composition is generally referred to as a polymer blend or polyblend. Depending upon the degree of miscibility or immiscibility, such a polyblend may resemble a random copolymer or a block or graft copolymer or it may show micro or macro heterogeneous separation into a multiphase system. Viscosity method is simple and it offers very useful information about the relationship between dilute solution properties and bulk structure of the polymer blend. The basic idea of using viscosity as a parameter for compatibility determination of polymer blends lies in the fact that in solution the repulsive interaction may cause shrinkage of polymer coils resulting in a viscosity of the polymer mixture that is lower than the value calculated from viscosities of the pure components on the assumption of the additive law. In the present study, an attempt has been made to blend PPG 4000 with PEG 4000 in 1,4 -Dioxane at 303K at 1% concentration. The blend compositions were formed in the ratio 0:1, 0.2:0.8, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.8:0.2, 1:0. Relative viscosity of the blend compositions was determined and the values are nonlinear which showed incompatibility. Miscibility nature of the blends were determined further using additive law, log additive law and free volume additive law and the experimental values in all the cases showed negative deviation which is a characteristic of immiscible blend. The miscibility nature of the blend was further confirmed through density, ultrasonic velocity, refractive index and other techniques. The blend showed immiscibility.

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Kruse, Nancy H. M. (Inventor); Fox, Robert L. (Inventor); Tran, Sang Q. (Inventor)

1995-01-01

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate is disclosed. The process may be used to prepare both rigid and flexible cables and circuit boards. A substrate is provided and a polymeric solution comprising a self-bonding, soluble polymer and a solvent is applied to the substrate. Next, the polymer solution is dried to form a polymer coated substrate. The polymer coated substrate is metallized and patterned. At least one additional coating of the polymeric solution is applied to the metallized, patterned, polymer coated substrate and the steps of metallizing and patterning are repeated. Lastly, a cover coat is applied. When preparing a flexible cable and flexible circuit board, the polymer coating is removed from the substrate.

Combined Mechanical and Electrical Study of Polymers of Biological Origin

NASA Astrophysics Data System (ADS)

Zsoldos, G.; Szoda, K.; Marossy, K.

2017-02-01

Thermally Simulated Depolarization Current measurement is an excellent but not widely used method for identifying relaxation processes in polymers. The DMA method is used here to analyze the mechanical changes depend on temperature in biopolymers. The two techniques take advantage of the energy changes involved in the various phase transitions of certain polymer molecules. This allows for several properties of the material to be ascertained; melting points, enthalpies of melting, crystallization temperatures, glass transition temperatures and degradation temperatures. The examined biopolymer films are made from biological materials such as proteins and polysaccharides. These materials have gained wide usage in pharmaceutical, medical and food areas. The uses of biopolymer films depend on their structure and mechanical properties. This work is based on pectin and gelatin films. The films were prepared by casting. The casting technique used aqueous solutions in each case of sample preparation. The manufacturing process of the pectin and gelatin films was a single stage solving process.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

2016-05-01

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengwa, R. J., E-mail: rjsengwa@rediffmail.com; Dhatarwal, Priyanka, E-mail: dhatarwalpriyanka@gmail.com; Choudhary, Shobhna, E-mail: shobhnachoudhary@rediffmail.com

2016-05-06

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF{sub 4}) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governedmore » by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10{sup −6} S cm{sup −1} which suggests the suitability of the SPE film for rechargeable lithium batteries.« less

For Stimul-Responsive Polymers with Enhanced Efficiency in Reservoir Recovery Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles McCormick; Roger Hester

Acrylamide-based hydrophobically modified (HM) polybetaines containing N-butylphenylacrylamide (BPAM) and varying amounts of either sulfobetaine (3-(2-acrylamido-2-methylpropanedimethylammonio)-1-propanesulfonate, AMPDAPS) or carboxybetaine (4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate, AMPDAB) comonomers were synthesized via micellar copolymerization. The terpolymers were characterized via {sup 13}C NMR and UV spectroscopies, classical and dynamic light scattering, and potentiometric titration. The response of aqueous polymer solutions to various external stimuli, including changes in solution pH, electrolyte concentration, and the addition of small molecule surfactants, was investigated using surface tension and rheological measurements. Low charge density terpolymers were found to show greater viscosity enhancement upon the addition of surfactant compared to the high charge densitymore » terpolymers. The addition of sodium dodecyl sulfate (SDS) produced the largest maximum in solution viscosity, while N-dodecyl-N,N,N-trimethylammonium bromide (DTAB), N-dodecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-12), and Triton X-100 tended to show reduced viscosity enhancement. In most cases, the high charge density carboxybetaine terpolymer exhibited diminished solution viscosities upon surfactant addition. In our last report, we discussed solution thermodynamic theory that described changes in polymer coil conformation as a function of solution temperature and polymer molecular weight. These polymers contained no ionic charges. In this report, we expand polymer solution theory to account for the electrostatic interactions present in solutions of charged polymers. Polymers with ionic charges are referred to as polyions or polyelectrolytes.« less

Influence of pH and temperature of dip-coating solution on the properties of cellulose acetate-ceramic composite membrane for ultrafiltration.

PubMed

Kaur, Harjot; Bulasara, Vijaya Kumar; Gupta, Raj Kumar

2018-09-01

Polymer-ceramic composite membranes were prepared by dip coating technique using 5 wt.% cellulose acetate (CA) solution at different temperatures (15 °C, 25 °C and 40 °C). The effect of pH (2-12) of the polymeric solution on the properties of the membranes was studied using SEM, EDAX, FTIR, gas and liquid permeation. The thickness of the polymeric layer depended on the interaction of CA solution with the surface of ceramic support. Membrane permeability decreased with increase in pH because of decrease in pore size and porosity resulting from strong interaction of the polymer layer with the ceramic support. The porosity and mean pore size of the prepared membranes were found to be 28-60% and 30-47 nm (ultrafiltration range), respectively. The optimized membrane (pH 7) was used for ultrafiltration of oil in water emulsions (100 and 200 mg/L). Oil rejection of 99.61% was obtained for 100 mg/L of oil concentration in water. Copyright © 2018 Elsevier Ltd. All rights reserved.

Physicochemical characterization and drug-release properties of celecoxib hot-melt extruded glass solutions.

PubMed

Andrews, Gavin P; Abu-Diak, Osama; Kusmanto, Febe; Hornsby, Peter; Hui, Zhai; Jones, David S

2010-11-01

The interest in hot-melt extrusion (HME) as a drug delivery technology for the production of glass solutions is growing rapidly. HME glass solutions have a tendency to recrystallize during storage and also typically have a very dense structure, restricting the ingress of dissolution fluid and retarding drug release. In this study, we have used HME to manufacture glass solutions containing celecoxib (CX) and polyvinylpyrrolidone (PVP) and have assessed the use of supercritical carbon dioxide (scCO2) as a pore-forming agent to enhance drug release. Differential scanning calorimetry confirmed the formation of glass solutions following extrusion. All extrudates exhibited a single glass transition temperature (Tg), positioned between the Tg values of CX and PVP. The instability of glass solutions is a significant problem during storage. Stabilization may be improved through the appropriate choice of excipient to facilitate drug–polymer interactions. The Gordon–Taylor equation showed that the Tg values of all extrudates expected on ideal mixing were lower than those observed experimentally. This may be indicative of drug–polymer interactions that decrease free volume and elevate the Tg. Molecular interactions between CX and PVP were further confirmed using Fourier transform infrared and Raman spectroscopy. Storage stability of the extrudates was shown to be dependent on drug loading. Samples containing a higher CX loading were less stable, which we ascribed to decreased Tg and hence increased mobility within the drug–polymer matrix. The solubility of CX was improved through the formulation of extruded glass solutions, but release rate was relatively slow. Exposure of extrudates to scCO2 had no effect on the solid-state properties of CX but did produce a highly porous structure. The drug-release rate from extrudates after scCO2 exposure was significantly higher.

Microcontact printing for patterning carbon nanotube/polymer composite films with electrical conductivity.

PubMed

Ogihara, Hitoshi; Kibayashi, Hiro; Saji, Tetsuo

2012-09-26

Patterned carbon nanotube (CNT)/acrylic resin composite films were prepared using microcontact printing (μCP). To prepare ink for μCP, CNTs were dispersed into propylene glycol monomethyl ether acetate (PGMEA) solution in which acrylic resin and a commercially available dispersant (Disperbyk-2001) dissolved. The resulting ink were spin-coated onto poly(dimethylsiloxane) (PDMS) stamps. By drying solvent components from the ink, CNT/polymer composite films were prepared over PDMS stamps. Contact between the stamps and glass substrates provided CNT/polymer composite patternings on the substrates. The transfer behavior of the CNT/polymer composite films depended on the thermal-treatment temperature during μCP; thermal treatment at temperatures near the glass-transition temperature (T(g)) of the acrylic resin was effective to form uniform patternings on substrates. Moreover, contact area between polymer and substrates also affect the transfer behavior. The CNT/polymer composite films showed high electrical conductivity, despite the nonconductivity of polymer components, because CNTs in the films were interconnected. The electrical conductivity of the composite films increased as CNT content in the film became higher; as a result, the composite patternings showed almost as high electrical conductivity as previously reported CNT/polymer bulk composites.

Control of polymer network topology in semi-batch systems

NASA Astrophysics Data System (ADS)

Wang, Rui; Olsen, Bradley; Johnson, Jeremiah

Polymer networks invariably possess topological defects: loops of different orders. Since small loops (primary loops and secondary loops) both lower the modulus of network and lead to stress concentration that causes material failure at low deformation, it is desirable to greatly reduce the loop fraction. We have shown that achieving loop fraction close to zero is extremely difficult in the batch process due to the slow decay of loop fraction with the polymer concentration and chain length. Here, we develop a modified kinetic graph theory that can model network formation reactions in semi-batch systems. We demonstrate that the loop fraction is not sensitive to the feeding policy if the reaction volume maintains constant during the network formation. However, if we initially put concentrated solution of small junction molecules in the reactor and continuously adding polymer solutions, the fractions of both primary loop and higher-order loops will be significantly reduced. There is a limiting value (nonzero) of loop fraction that can be achieved in the semi-batch system in condition of extremely slow feeding rate. This minimum loop fraction only depends on a single dimensionless variable, the product of concentration and with single chain pervaded volume, and defines an operating zone in which the loop fraction of polymer networks can be controlled through adjusting the feeding rate of the semi-batch process.

Motion of Molecular Probes and Viscosity Scaling in Polyelectrolyte Solutions at Physiological Ionic Strength

PubMed Central

Sozanski, Krzysztof; Wisniewska, Agnieszka; Kalwarczyk, Tomasz; Sznajder, Anna; Holyst, Robert

2016-01-01

We investigate transport properties of model polyelectrolyte systems at physiological ionic strength (0.154 M). Covering a broad range of flow length scales—from diffusion of molecular probes to macroscopic viscous flow—we establish a single, continuous function describing the scale dependent viscosity of high-salt polyelectrolyte solutions. The data are consistent with the model developed previously for electrically neutral polymers in a good solvent. The presented approach merges the power-law scaling concepts of de Gennes with the idea of exponential length scale dependence of effective viscosity in complex liquids. The result is a simple and applicable description of transport properties of high-salt polyelectrolyte solutions at all length scales, valid for motion of single molecules as well as macroscopic flow of the complex liquid. PMID:27536866

Universal ultrafast signatures of photoexcitations in conjugated polymers: excitons and charge-transfer polarons

NASA Astrophysics Data System (ADS)

McBranch, Duncan W.; Kraabel, Brett; Xu, Su; Wang, Hsing-Lin; Klimov, Victor I.

1999-12-01

Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solution of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C6O, we assign these secondary species as bound polarons.

Mussel-inspired polydopamine biopolymer decorated with magnetic nanoparticles for multiple pollutants removal.

PubMed

Zhang, Shengxiao; Zhang, Yuanyuan; Bi, Guoming; Liu, Junshen; Wang, Zhigang; Xu, Qiang; Xu, Hui; Li, Xiaoyan

2014-04-15

The polydopamine polymer decorated with magnetic nanoparticles (Fe3O4/PDA) was synthesized and applied for removal of multiple pollutants. The resulted Fe3O4/PDA was characterized with elemental analysis, thermo-gravimetric analyses, vibrating sample magnetometer, high resolution transmission electron microscope, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. The self-polymerization of dopamine could be completed within 8h, and Fe3O4 nanoparticles were embedded into PDA polymer. Superparamagnetism and large saturation magnetization facilitated collection of sorbents with a magnet. Based on the catechol and amine groups, the PDA polymer provided multiple interactions to combine with pollutants. To investigate the adsorption ability of Fe3O4/PDA, heavy metal ions and dyes were selected as target pollutants. The adsorption of pollutants was pH dependent due to the variation of surface charges at different solution pH. The removal efficiencies of cation pollutants enhanced with solution pH increasing, and that of anion pollutant was just the opposite. Under the optimal solution pH, the maximum adsorption capacity calculated from Langmuir adsorption isotherm for methylene blue, tartrazine, Cu(2+), Ag(+), and Hg(2+) were 204.1, 100.0, 112.9, 259.1, and 467.3 mg g(-1), respectively. The Fe3O4/PDA shows great potential for multiple pollutants removal, and this study is the first application of PDA polymer in environmental remediation. Copyright © 2014 Elsevier B.V. All rights reserved.

Capillary Thinning and Pinch-off Dynamics and Printability of Polyelectrolyte Solutions

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Jimenez, Leidy N.; Dinic, Jelena; Parsi, Nikila

Biological macromolecules like proteins, DNA and polysaccharides, and many industrial polymers, are classified together as polyelectrolytes for in solution, the repeat units in their backbone are decorated with disassociated, charge-bearing ionic groups, surrounded by counter-ions. In diverse applications like inkjet printing, sprayable cosmetics and insecticides, paints and coatings that involve formation of fluid columns or sheets that undergo progressive thinning and pinch-off into drops, the dominant flow within the necking filament is extensional in nature. The extensional rheology response of the charged macromolecular solutions is not as well understood as that of their uncharged counterparts. Here focus on the characterization of capillary thinning and pinch-off dynamics, extensional rheology and printability of two model systems: sodium (polystyrene sulfonate) and poly(acrylic acid) by using dripping-onto-substrate (DoS) rheometry technique. Both the measured extensional relaxation times and the extensional viscosity values show salt- and polymer concentration-dependent behavior that is not expected or anticipated from the typical shear rheology response.

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study.

PubMed

Ferro, Monica; Castiglione, Franca; Punta, Carlo; Melone, Lucio; Panzeri, Walter; Rossi, Barbara; Trotta, Francesco; Mele, Andrea

2016-08-15

The chemical cross-linking of β-cyclodextrin (β-CD) with ethylenediaminetetraacetic dianhydride (EDTA) led to branched polymers referred to as cyclodextrin nanosponges (CDNSEDTA). Two different preparations are described with 1:4 and 1:8 CD-EDTA molar ratios. The corresponding cross-linked polymers were contacted with 0.27 M aqueous solution of ibuprofen sodium salt (IP) leading to homogeneous, colorless, drug loaded hydrogels. The systems were characterized by high resolution magic angle spinning (HR-MAS) NMR spectroscopy. Pulsed field gradient spin echo (PGSE) NMR spectroscopy was used to determine the mean square displacement (MSD) of IP inside the polymeric gel at different observation times td. The data were further processed in order to study the time dependence of MSD: MSD = f(td). The proposed methodology is useful to characterize the different diffusion regimes that, in principle, the solute may experience inside the hydrogel, namely normal or anomalous diffusion. The full protocols including the polymer preparation and purification, the obtainment of drug-loaded hydrogels, the NMR sample preparation, the measurement of MSD by HR-MAS NMR spectroscopy and the final data processing to achieve the time dependence of MSD are here reported and discussed. The presented experiments represent a paradigmatic case and the data are discussed in terms of innovative approach to the characterization of the transport properties of an encapsulated guest within a polymeric host of potential application for drug delivery.

Method for separating water soluble organics from a process stream by aqueous biphasic extraction

DOEpatents

Chaiko, David J.; Mego, William A.

1999-01-01

A method for separating water-miscible organic species from a process stream by aqueous biphasic extraction is provided. An aqueous biphase system is generated by contacting a process stream comprised of water, salt, and organic species with an aqueous polymer solution. The organic species transfer from the salt-rich phase to the polymer-rich phase, and the phases are separated. Next, the polymer is recovered from the loaded polymer phase by selectively extracting the polymer into an organic phase at an elevated temperature, while the organic species remain in a substantially salt-free aqueous solution. Alternatively, the polymer is recovered from the loaded polymer by a temperature induced phase separation (cloud point extraction), whereby the polymer and the organic species separate into two distinct solutions. The method for separating water-miscible organic species is applicable to the treatment of industrial wastewater streams, including the extraction and recovery of complexed metal ions from salt solutions, organic contaminants from mineral processing streams, and colorants from spent dye baths.

Morphology and thermodynamic characteristics of selenium-containing nanostructures based on polymethacrylic acid

NASA Astrophysics Data System (ADS)

Valueva, S. V.; Borovikova, L. N.; Vylegzhanina, M. E.; Sukhanova, T. E.

2010-09-01

The morphology and thermodynamic characteristics of nanostructures formed as a result of the reduction of the selenium ion in a selenite-ascorbate redox system in water solutions of polymethacrylic acid were studied by molecular optics and atomic-force microscopy. The dependence of the morphology of the selenium-containing nanostructures on the mass selenium-to-polymer ratio (ν) in solution was determined. It was established that a large number of macromolecules (up to 4300) is adsorbed on the selenium nanoparticles, leading to the formation of nanostructures with super-high molecular mass and an almost spherical form. It was shown that the density of the nanostructures, as calculated on the basis of the experimental data on the size and molecular mass of the nanocomposite, depends substantially on the selenium concentrations in the solution. The thermodynamic state of the solutions of nanostructures is described.

Deformation analysis of polymers composites: rheological model involving time-based fractional derivative

NASA Astrophysics Data System (ADS)

Zhou, H. W.; Yi, H. Y.; Mishnaevsky, L.; Wang, R.; Duan, Z. Q.; Chen, Q.

2017-05-01

A modeling approach to time-dependent property of Glass Fiber Reinforced Polymers (GFRP) composites is of special interest for quantitative description of long-term behavior. An electronic creep machine is employed to investigate the time-dependent deformation of four specimens of dog-bond-shaped GFRP composites at various stress level. A negative exponent function based on structural changes is introduced to describe the damage evolution of material properties in the process of creep test. Accordingly, a new creep constitutive equation, referred to fractional derivative Maxwell model, is suggested to characterize the time-dependent behavior of GFRP composites by replacing Newtonian dashpot with the Abel dashpot in the classical Maxwell model. The analytic solution for the fractional derivative Maxwell model is given and the relative parameters are determined. The results estimated by the fractional derivative Maxwell model proposed in the paper are in a good agreement with the experimental data. It is shown that the new creep constitutive model proposed in the paper needs few parameters to represent various time-dependent behaviors.

Structural modification in the formation of starch – silver nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begum, S. N. Suraiya; Ramasamy, Radha Perumal, E-mail: perumal.ramasamy@gmail.com; Aswal, V. K.

Polymer based nanocomposites have gained wide applications in field of battery technology. Starch is a naturally occurring polysaccharide with sustainable properties such as biodegradable, non toxic, excellent film forming capacity and it also act as reducing agent for the metal nanoparticles. In our research various concentration of silver nitrate (AgNO{sub 3}) was added to the starch solution and films were obtained using solution casting method. Surface electron microscope (SEM) of the films shows modifications depending upon the concentration of AgNO{sub 3}. Small angle neutron scattering (SANS) analysis showed that addition of silver nitrate modifies the starch to disc like structuresmore » and with increasing the AgNO{sub 3} concentration leads to the formation of fractals. This research could benefit battery technology where solid polymer membranes using starch is used.« less

Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

NASA Astrophysics Data System (ADS)

Abd El-Rehim, H. A.

2005-10-01

Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

Molecular dynamics simulations of poly (ethylene oxide) hydration and conformation in solutions

NASA Astrophysics Data System (ADS)

Dahal, Udaya; Dormidontova, Elena

Polyethylene oxide (PEO) is one of the most actively used polymers, especially in biomedical applications due to its high hydrophilicity, biocompatibility and potency to inhibit protein adsorption. PEO solubility and conformation in water depends on its capability to form hydrogen bonds. Using atomistic molecular dynamics simulations we investigated the details of water packing around PEO chain and characterized the type and lifetime of hydrogen bonds in aqueous and mixed solvent solutions. The observed polymer chain conformation varies from an extended coil in pure water to collapsed globule in hexane and a helical-like conformation in pure isobutyric acid or isobutyric acid -water mixture in agreement with experimental observations. We'll discuss the implications of protic solvent arrangement and stability of hydrogen bonds on PEO chain conformation and mobility. This research is supported by NSF (DMR-1410928).

Erythrocyte interactions - Comparison of the aggregation power of polymer molecules used in medicine - Not only size does matter.

PubMed

Jovtchev, S; Alexandrov, S; Hristova-Avakumova, N; Miteva, S; Traikov, L; Gerasimova, D; Stoeff, S

2016-01-01

Different colloids are used as a part of solutions for fluid resuscitation and organ preservation: hydroxyethyl starches (HES), dextran (Dx), polyethylene glycols (PEG), polyvinyl pyrrolidone (PVP). Some of the problems associated with their application are addressed to alteration in erythrocyte (ERY) rheology. We intended to estimate in vitro and compare the aggregation power (AP) of these molecules related to ERY interactions. Washed human ERY are used during the study. The zeta sedimentation technique is used to quantify the cell aggregation. Zeta sedimentation ratio (ZSR) based indices (AI) are calculated. The hydrodynamic radius (Rh) of the polymer molecules is determined using viscometry. For all polymers tested a linear range in the relationship AI - concentration was found. The slope of the calculated line was interpreted as measure of the molecule's AP. The following ranking was obtained: PEG >PVP >DX >HES. Within the same chemical type of polymer, increasing Rh of the molecules leads to elevated AI. Comparison of the AP of molecules with similar Rh reveals a significant dependence on their chemical nature. Our results show that molecule's AP is significantly dependent on their chemical nature - i.e. not only molecular size does matter.

Effects of humidity and solution viscosity on electrospun fiber morphology.

PubMed

Nezarati, Roya M; Eifert, Michelle B; Cosgriff-Hernandez, Elizabeth

2013-10-01

Electrospinning is a popular technique to fabricate tissue engineering scaffolds due to the exceptional tunability of fiber morphology that can be used to control scaffold mechanical properties, degradation rate, and cell behavior. Although the effects of modulating processing or solution parameters on fiber morphology have been extensively studied, there remains limited understanding of the impact of environmental parameters such as humidity. To address this gap, three polymers (poly(ethylene glycol) [PEG], polycaprolactone [PCL], and poly(carbonate urethane) [PCU]) were electrospun at a range of relative humidities (RH = 5%-75%) and the resulting fiber architecture characterized with scanning electron microscopy. Low relative humidity (< 50%) resulted in fiber breakage for all three polymers due to decreased electrostatic discharge from the jet. At high relative humidity (> 50%), three distinct effects were observed based on individual polymer properties. An increase in fiber breakage and loss of fiber morphology occurred in the PEG system as a result of increased water absorption at high relative humidity. In contrast, surface pores on PCL fibers were observed and hypothesized to have formed via vapor-induced phase separation. Finally, decreased PCU fiber collection occurred at high humidity likely due to increased electrostatic discharge. These findings highlight that the effects of relative humidity on electrospun fiber morphology are dependent on polymer hydrophobicity, solvent miscibility with water, and solvent volatility. An additional study was conducted to highlight that small changes in molecular weight can strongly influence solution viscosity and resulting fiber morphology. We propose that solution viscosity rather than concentration is a more useful parameter to report in electrospinning methodology to enable reproduction of findings. In summary, this study further elucidates key mechanisms in electrospun fiber formation that can be utilized to fabricate tissue engineering scaffolds with tunable and reproducible properties.

Effects of Humidity and Solution Viscosity on Electrospun Fiber Morphology

PubMed Central

Nezarati, Roya M.; Eifert, Michelle B.

2013-01-01

Electrospinning is a popular technique to fabricate tissue engineering scaffolds due to the exceptional tunability of fiber morphology that can be used to control scaffold mechanical properties, degradation rate, and cell behavior. Although the effects of modulating processing or solution parameters on fiber morphology have been extensively studied, there remains limited understanding of the impact of environmental parameters such as humidity. To address this gap, three polymers (poly(ethylene glycol) [PEG], polycaprolactone [PCL], and poly(carbonate urethane) [PCU]) were electrospun at a range of relative humidities (RH=5%–75%) and the resulting fiber architecture characterized with scanning electron microscopy. Low relative humidity (<50%) resulted in fiber breakage for all three polymers due to decreased electrostatic discharge from the jet. At high relative humidity (>50%), three distinct effects were observed based on individual polymer properties. An increase in fiber breakage and loss of fiber morphology occurred in the PEG system as a result of increased water absorption at high relative humidity. In contrast, surface pores on PCL fibers were observed and hypothesized to have formed via vapor-induced phase separation. Finally, decreased PCU fiber collection occurred at high humidity likely due to increased electrostatic discharge. These findings highlight that the effects of relative humidity on electrospun fiber morphology are dependent on polymer hydrophobicity, solvent miscibility with water, and solvent volatility. An additional study was conducted to highlight that small changes in molecular weight can strongly influence solution viscosity and resulting fiber morphology. We propose that solution viscosity rather than concentration is a more useful parameter to report in electrospinning methodology to enable reproduction of findings. In summary, this study further elucidates key mechanisms in electrospun fiber formation that can be utilized to fabricate tissue engineering scaffolds with tunable and reproducible properties. PMID:23469941

Use of gold nanoparticles as crosslink agent to form chitosan nanocapsules: study of the direct interaction in aqueous solutions.

PubMed

Prado-Gotor, R; López-Pérez, G; Martín, M J; Cabrera-Escribano, F; Franconetti, A

2014-06-01

A systematic study of the interaction between free anionic gold nanoparticles and chitosan in a solution is presented. A spectroscopic study of the interaction between 10nm gold nanoparticles and low molecular weight chitosan is reported as a function of the concentration and pH of the polymer in a solution. Zeta potential measurements and TEM images indicate the effective aggregation of the nanoparticles in the presence of chitosan. At the same time, anionic gold nanoparticles act as crosslink agents to form chitosan nanocapsules with an average molecular size of 260nm. The changes of the surface plasmon band due to the adsorption of the polymer on the nanoparticle surface allow using of the citrate gold nanoparticles as sensors of the polymer for analytical purposes. The limit of detection for chitosan biopolymer is 69nM. The optimum pH for the interaction between the biopolymer and the nanoparticles is found at a value of 6.4, obtained from spectrophotometric measurements and applying a deconvolution analysis of the experimental data. A simple model based on molecular surface electrostatic interactions is proposed to understand the pH dependence of the investigated system. Copyright © 2014 Elsevier Inc. All rights reserved.

Characteristics of nano-sized yttria powder synthesized by a polyvinyl alcohol solution route at low temperature.

PubMed

Lee, Sang-Jin; Jung, Choong-Hwan

2012-01-01

Nano-sized yttria (Y2O3) powders were successfully synthesized at a low temperature of 400 degrees C by a simple polymer solution route. PVA polymer, as an organic carrier, contributed to an atom-scale homogeneous precursor gel and it resulted in fully crystallized, nano-sized yttria powder with high specific surface area through the low temperature calcination. In this process, the content of PVA, calcination temperature and heating time affected the microstructure and crystallization behavior of the powders. The development of crystalline phase and the final particle size were strongly dependant on the oxidation reaction from the polymer burn-out step and the PVA content. In this paper, the PVA solution technique for the fabrication of nano-sized yttria powders is introduced. The effects of PVA content and holding time on the powder morphology and powder specific surface area are also studied. The characterization of the synthesized powders is examined by using XRD, DTA/TG, SEM, TEM and nitrogen gas adsorption. The yttria powder synthesized from the PVA content of 3:1 ratio and calcined at 400 degrees C had a crystallite size of about 20 nm or less with a high surface areas of 93.95-120.76 m2 g(-1).

Mechanical properties of shape memory polymers for morphing aircraft applications

NASA Astrophysics Data System (ADS)

Keihl, Michelle M.; Bortolin, Robert S.; Sanders, Brian; Joshi, Shiv; Tidwell, Zeb

2005-05-01

This investigation addresses basic characterization of a shape memory polymer (SMP) as a suitable structural material for morphing aircraft applications. Tests were performed for monotonic loading in high shear at constant temperature, well below, or just above the glass transition temperature. The SMP properties were time-and temperature-dependent. Recovery by the SMP to its original shape needed to be unfettered. Based on the testing SMPs appear to be an attractive and promising component in the solution for a skin material of a morphing aircraft. Their multiple state abilities allow them to easily change shape and, once cooled, resist large loads.

Unraveling the Solution-State Supramolecular Structures of Donor-Acceptor Polymers and their Influence on Solid-State Morphology and Charge-Transport Properties.

PubMed

Zheng, Yu-Qing; Yao, Ze-Fan; Lei, Ting; Dou, Jin-Hu; Yang, Chi-Yuan; Zou, Lin; Meng, Xiangyi; Ma, Wei; Wang, Jie-Yu; Pei, Jian

2017-11-01

Polymer self-assembly in solution prior to film fabrication makes solution-state structures critical for their solid-state packing and optoelectronic properties. However, unraveling the solution-state supramolecular structures is challenging, not to mention establishing a clear relationship between the solution-state structure and the charge-transport properties in field-effect transistors. Here, for the first time, it is revealed that the thin-film morphology of a conjugated polymer inherits the features of its solution-state supramolecular structures. A "solution-state supramolecular structure control" strategy is proposed to increase the electron mobility of a benzodifurandione-based oligo(p-phenylene vinylene) (BDOPV)-based polymer. It is shown that the solution-state structures of the BDOPV-based conjugated polymer can be tuned such that it forms a 1D rod-like structure in good solvent and a 2D lamellar structure in poor solvent. By tuning the solution-state structure, films with high crystallinity and good interdomain connectivity are obtained. The electron mobility significantly increases from the original value of 1.8 to 3.2 cm 2 V -1 s -1 . This work demonstrates that "solution-state supramolecular structure" control is critical for understanding and optimization of the thin-film morphology and charge-transport properties of conjugated polymers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rheological Behavior Xanthan and SlurryPro Polymer Solutions Evaluated as Shear Thinning Delivery Fluids for Subsurface Remediation

NASA Astrophysics Data System (ADS)

Zhong, L.; Oostrom, M.; Truex, M.; Vermeul, V.

2011-12-01

Shear thinning fluids can be applied as a delivery means to enhance the uniformity of remedial amendment distribution in heterogeneous aquifers, thereby to improve remediation performance. The rheological behavior of biopolymer xanthan gum and synthetic polymer SlurryPro were tested, and their influence on the amendment delivery performance was evaluated. The impact of polymer concentration, basic water chemistry, salinity (e.g., Br-, Na+, Ca2+ concentrations), remedial amendments (phosphate, sodium lactate, ethyl lactate, lactate oil, whey), sediments, and the mixing approach on the rheological properties of the polymer solutions was determined. The SlurryPro polymer lost shear-thinning properties even at relatively low solution ionic strength. However, the xanthan gum polymer maintained shear-thinning properties under most of the tested conditions, though with some loss in absolute viscosity with increasing ionic strength. Xanthan appeared to be the better candidate for enhanced amendment delivery. Increasing in xanthan concentration not only increased the solution viscosity, but also increased degree of shear thinning. Addition of salt decreased the solution viscosity and the degree of shear thinning, while the influence was diminished when the polymer concentration was higher. After reaching a critical xanthan concentration, addition of salt increased solution viscosity. The degradation of xanthan and SlurryPro in the presence of site aquifer materials and microbes was studied in batch tests in which the field sediment/water ratio was simulated. The viscosity of the polymer solutions dropped 85% or more in the first week, while the solution chemical oxygen demand (COD) decreasing occurred at a much slower rate.

Addition of ferrocene controls polymorphism and enhances charge mobilities in poly(3-hexylthiophene) thin-film transistors

NASA Astrophysics Data System (ADS)

Smith, Brandon; Clark, Michael; Grieco, Christopher; Larsen, Alec; Asbury, John; Gomez, Enrique

2015-03-01

Crystalline organic molecules often exhibit the ability to form multiple crystal structures depending on the processing conditions. Exploiting this polymorphism to optimize molecular orbital overlap between adjacent molecules within the unit lattice of conjugated polymers is an approach to enhance charge transport within the material. We have demonstrated the formation of tighter π- π stacking poly(3-hexylthiophene-2,5-diyl) polymorphs in films spin coated from ferrocene-containing solutions using grazing incident X-ray diffraction. As a result, we found that the addition of ferrocene to casting solutions yields thin-film transistors which exhibit significantly higher source-drain current and charge mobilities than neat polymer devices. Insights gleaned from ferrocene/poly(3-hexylthiophene) mixtures can serve as a template for selection and optimization of next generation small molecule/polymer systems possessing greater baseline charge mobilities. Ultimately, the development of such techniques to enhance the characteristics of organic transistors without imparting high costs or loss of advantageous properties will be a critical factor determining the future of organic components within the electronics market.

Macroion induced dehydration of weak polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Zheng, Zhongli; Zhu, Y. Elaine

2014-03-01

The interaction of macroions, including polyelectrolytes, DNAs, and proteins, with polymer and cellular surfaces is critically related to many biomolecular activities, such as protein adsorption and DNA hybridization at probe surfaces. In an experimental approach to examine the macroion electrostatic interaction with a polymer surface while minimizing the long-debated hydrophobic interaction, we study the interaction of molybdenum-based inorganic polyoxometalate (POM) nanoclusters carrying 42 negative charges as model hydrophilic macroions with surface-tethered poly-2-vinylpyridine (P2VP) brushes immersed in aqueous solutions. By AFM, QCM, and contact goniometer, we have observed the collapse of P2VP chains by adding POM macroions at a constant pH. Surprisingly, added POM macroions can cause the shift of swollen-to-collapse transition pH to a lower value, in contrast to the shift to high pH value by adding simple monovalent salts. At sufficiently high POM concentration, a stable POM-P2VP composite layer, showing little dependence on solution pH and additional salts, can be formed, suggesting a simple route to construct meso-porous polymer membranes.

Photophysical and morphological implications of single-strand conjugated polymer folding in solution

DOE PAGES

Fauvell, Thomas J.; Zheng, Tianyue; Jackson, Nicholas E.; ...

2016-04-08

Organic semiconductors have garnered substantial interest in optoelectronics, but their device performances exhibit strong dependencies on material crystallinity and packing. In an effort to understand the interactions dictating the morphological and photophysical properties of a high-performing photovoltaic polymer, PTB7, a series of short oligomers and low molecular weight polymers of PTB7 were synthesized. Chain-length dependent optical studies of these oligomers demonstrate that PTB7’s low-energy visible absorption is largely due to self-aggregation-induced ordering, rather than in-chain charge transfer, as previously thought. By examining molecular weight and concentration dependent optical properties, supplemented by molecular dynamics simulations, we attribute polymeric PTB7’s unique midgapmore » fluorescence and concentration independent absorption spectrum to an interplay between low molecular weight unaggregated strands and high-molecular weight self-aggregated (folded) strands. Specifically, we propose that the onset of PTB7 self-folding occurs between 7 and 13 repeat units, but the aggregates characteristic of polymeric PTB7 only develop at lengths of ~30 repeat units. Atomistic molecular dynamics simulations of PTB7 corroborate these conclusions, and a simple relation is proposed which quantifies the free-energy of conjugated polymer folding. Lastly, this study provides detailed guidance in the design of intra- and interchain contributions to the photophysical and morphological properties of polymeric semiconductors.« less

Multilevel non-volatile data storage utilizing common current hysteresis of networked single walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Hwang, Ihn; Wang, Wei; Hwang, Sun Kak; Cho, Sung Hwan; Kim, Kang Lib; Jeong, Beomjin; Huh, June; Park, Cheolmin

2016-05-01

The characteristic source-drain current hysteresis frequently observed in field-effect transistors with networked single walled carbon-nanotube (NSWNT) channels is problematic for the reliable switching and sensing performance of devices. But the two distinct current states of the hysteresis curve at a zero gate voltage can be useful for memory applications. In this work, we demonstrate a novel non-volatile transistor memory with solution-processed NSWNTs which are suitable for multilevel data programming and reading. A polymer passivation layer with a small amount of water employed on the top of the NSWNT channel serves as an efficient gate voltage dependent charge trapping and de-trapping site. A systematic investigation evidences that the water mixed in a polymer passivation solution is critical for reliable non-volatile memory operation. The optimized device is air-stable and temperature-resistive up to 80 °C and exhibits excellent non-volatile memory performance with an on/off current ratio greater than 104, a switching time less than 100 ms, data retention longer than 4000 s, and write/read endurance over 100 cycles. Furthermore, the gate voltage dependent charge injection mediated by water in the passivation layer allowed for multilevel operation of our memory in which 4 distinct current states were programmed repetitively and preserved over a long time period.The characteristic source-drain current hysteresis frequently observed in field-effect transistors with networked single walled carbon-nanotube (NSWNT) channels is problematic for the reliable switching and sensing performance of devices. But the two distinct current states of the hysteresis curve at a zero gate voltage can be useful for memory applications. In this work, we demonstrate a novel non-volatile transistor memory with solution-processed NSWNTs which are suitable for multilevel data programming and reading. A polymer passivation layer with a small amount of water employed on the top of the NSWNT channel serves as an efficient gate voltage dependent charge trapping and de-trapping site. A systematic investigation evidences that the water mixed in a polymer passivation solution is critical for reliable non-volatile memory operation. The optimized device is air-stable and temperature-resistive up to 80 °C and exhibits excellent non-volatile memory performance with an on/off current ratio greater than 104, a switching time less than 100 ms, data retention longer than 4000 s, and write/read endurance over 100 cycles. Furthermore, the gate voltage dependent charge injection mediated by water in the passivation layer allowed for multilevel operation of our memory in which 4 distinct current states were programmed repetitively and preserved over a long time period. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00505e

Sequential pH-dependent adsorption of ionic amphiphilic diblock copolymer micelles and choline oxidase onto conductive substrates: toward the design of biosensors.

PubMed

Sigolaeva, Larisa V; Günther, Ulrike; Pergushov, Dmitry V; Gladyr, Snezhana Yu; Kurochkin, Ilya N; Schacher, Felix H

2014-07-01

This work examines the fabrication regime and the properties of polymer-enzyme thin-films adsorbed onto conductive substrates (graphite or gold). The films are formed via two-steps, sequential adsorption of poly(n-butylmethacrylate)-block-poly(N,N-dimethylaminoethyl methacrylate) (PnBMA-b-PDMAEMA) diblock copolymer micelles (1st step of adsorption), followed by the enzyme choline oxidase (ChO) (2nd step of adsorption). The solution properties of both adsorbed components are studied and the pH-dependent step-by-step fabrication of polymer-enzyme biosensor coatings reveals rather drastic differences in their enzymatic activities in dependence on the pH of both adsorption steps. The resulting hybrid thin-films represent highly active biosensors for choline with a low detection limit of 30 nM and a good linearity in a range between 30 nM and 100 μM. The sensitivity is found to be 175 μA mM(-1) cm(-2) and the operational stability of the polymer-enzyme thin-films can be additionally improved via enzyme-to-enzyme crosslinking with glutaraldehyde. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Corrugated grating on organic multilayer Bragg reflector

NASA Astrophysics Data System (ADS)

Jaquet, Sylvain; Scharf, Toralf; Herzig, Hans Peter

2007-08-01

Polymeric multilayer Bragg structures are combined with diffractive gratings to produce artificial visual color effects. A particular effect is expected due to the angular reflection dependence of the multilayer Bragg structure and the dispersion caused by the grating. The combined effects can also be used to design particular filter functions and various resonant structures. The multilayer Bragg structure is fabricated by spin-coating of two different low-cost polymer materials in solution on a cleaned glass substrate. These polymers have a refractive index difference of about 0.15 and permit multilayer coatings without interlayer problems. Master gratings of different periods are realized by laser beam interference and replicated gratings are superimposed on the multilayer structure by soft embossing in a UV curing glue. The fabrication process requires only polymer materials. The obtained devices are stable and robust. Angular dependent reflection spectrums for the visible are measured. These results show that it is possible to obtain unexpected reflection effects. A rich variety of color spectra can be generated, which is not possible with a single grating. This can be explained by the coupling of transmission of grating orders and the Bragg reflection band. A simple model permits to explain some of the spectral vs angular dependence of reflected light.

Biodegradable "Smart" Polyphosphazenes with Intrinsic Multifunctionality as Intracellular Protein Delivery Vehicles.

PubMed

Martinez, Andre P; Qamar, Bareera; Fuerst, Thomas R; Muro, Silvia; Andrianov, Alexander K

2017-06-12

A series of biodegradable drug delivery polymers with intrinsic multifunctionality have been designed and synthesized utilizing a polyphosphazene macromolecular engineering approach. Novel water-soluble polymers, which contain carboxylic acid and pyrrolidone moieties attached to an inorganic phosphorus-nitrogen backbone, were characterized by a suite of physicochemical methods to confirm their structure, composition, and molecular sizes. All synthesized polyphosphazenes displayed composition-dependent hydrolytic degradability in aqueous solutions at neutral pH. Their formulations were stable at lower temperatures, potentially indicating adequate shelf life, but were characterized by accelerated degradation kinetics at elevated temperatures, including 37 °C. It was found that synthesized polyphosphazenes are capable of environmentally triggered self-assembly to produce nanoparticles with narrow polydispersity in the size range of 150-700 nm. Protein loading capacity of copolymers has been validated via their ability to noncovalently bind avidin without altering biological functionality. Acid-induced membrane-disruptive activity of polyphosphazenes has been established with an onset corresponding to the endosomal pH range and being dependent on polymer composition. The synthesized polyphosphazenes facilitated cell-surface interactions followed by time-dependent, vesicular-mediated, and saturable internalization of a model protein cargo into cancer cells, demonstrating the potential for intracellular delivery.

The adsorption of cationic and amphoteric copolymers on glass surfaces: zeta potential measurements, adsorption isotherm determination, and FT Raman characterization.

PubMed

Tartakovsky, Alla; Drutis, Dane M; Carnali, Joseph O

2003-07-15

The adsorption of cationic and amphoteric copolymers onto controlled pore glass (CPG) powders has been studied by measurement of the powder particle zeta (zeta) potential, by determination of the adsorption isotherm, and by FT Raman measurements of the polymer-coated powder. The cationic polymers consisted chiefly of homopolymers of dimethyldiallylammonium chloride (DMDAAC) or copolymers of DMDAAC and acrylamide. The amphoteric polymers studied included copolymers of DMDAAC and acrylic acid. The comonomer ratio was varied to explore the dependence of cationic charge density on the extent and effect of adsorption. Both types of polymers adsorb onto the anionic glass surface via an ion-exchange mechanism. Consequently, a correspondingly higher mass of a low-charge-density copolymer adsorbs than of a cationic homopolymer. The presence of the anionic portion in the amphoteric polymers does not significantly alter this picture. The zeta potential, however, reflects the overall nature of the polymer. Cationic polymers effectively neutralize the glass surface, while amphoteric polymers leave the zeta potential net negative. Adsorption isotherms, determined via the depletion technique using colloidal titration, were used to "calibrate" a FT Raman method. The latter was used to determined the amount of adsorbed polymer under solution conditions in which colloidal titration could not be performed.

Athermal Photonic Devices and Circuits on a Silicon Platform

NASA Astrophysics Data System (ADS)

Raghunathan, Vivek

In recent years, silicon based optical interconnects has been pursued as an effective solution that can offer cost, energy, distance and bandwidth density improvements over copper. Monolithic integration of optics and electronics has been enabled by silicon photonic devices that can be fabricated using CMOS technology. However, high levels of device integration result in significant local and global temperature fluctuations that prove problematic for silicon based photonic devices. In particular, high temperature dependence of Si refractive index (thermo-optic (TO) coefficient) shifts the filter response of resonant devices that limit wavelength resolution in various applications. Active thermal compensation using heaters and thermo-electric coolers are the legacy solution for low density integration. However, the required electrical power, device foot print and number of input/output (I/O) lines limit the integration density. We present a passive approach to an athermal design that involves compensation of positive TO effects from a silicon core by negative TO effects of the polymer cladding. In addition, the design rule involves engineering the waveguide core geometry depending on the resonance wavelength under consideration to ensure desired amount of light in the polymer. We develop exact design requirements for a TO peak stability of 0 pm/K and present prototype performance of 0.5 pm/K. We explore the material design space through initiated chemical vapor deposition (iCVD) of 2 polymer cladding choices. We study the effect of cross-linking on the optical properties of a polymer and establish the superior performance of the co-polymer cladding compared to the homo-polymer. Integration of polymer clad devices in an electronic-photonic architecture requires the possibility of multi-layer stacking capability. We use a low temperature, high density plasma chemical vapor deposition of SiO2/SiN x to hermetically seal the athermal. Further, we employ visible light for post-fabrication trimming of athermal rings by sandwiching a thin photosensitive layer of As2S3 in between amorphous Si core and polymer top cladding. System design of an add-drop filter requires an optimum combination of channel counts performance and power handling capacity for maximum aggregate bandwidth. We establish the superior performance of athermal add-drop filter compared to a standard filter treating bandwidth as the figure-of-merit. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

Gravity-Driven Thin Film Flow of an Ellis Fluid.

PubMed

Kheyfets, Vitaly O; Kieweg, Sarah L

2013-12-01

The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity ( η 0 ), τ 1/2 , and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ , on the front velocity saturation depended on τ 1/2 . This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications.

New way of polymer design for organic solar cells using the quinoid structure

NASA Astrophysics Data System (ADS)

Berube, Nicolas; Gaudreau, Josiane; Cote, Michel

2013-03-01

Research in organic photovoltaic applications are receiving a great interest as they offer an environmentally clean and low-cost solution to the world's rising energy needs. Controlling the device's active polymer optical bandgap is an important step that affects its absorption of the solar spectrum, and ultimately, its power conversion efficiency. The use of fused heterocycles that favors the polymer's quinoid structure has been a known method to lower the bandgap, for example, with isothianapthene, but there is a lack of quantifiable data on this effect. Density functional theory (DFT) calculations were done on over 60 polymers with bandgaps between 0.5 eV and 4 eV. They clearly show that low bandgaps are observed in copolymers that carefully stands between their quinoid and aromatic structures. Such balance can be obtained by mixing monomer units with quinoid characteristics with aromatic ones. Time-dependant DFT results also links low bandgaps with lower reorganization energy, which means that polymers with this structural form could possess higher charge mobilities. This link between the geometrical structure and the bandgap is compatible with a vast variety of polymers and is more convincing than the commonly used donor-acceptor method of polymer design.

Highly elastic polymer solutions under shear: Polymer migration, viscoelastic instabilities, and anomalous rheology

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M.J.; Muller, S.J.

1996-12-31

The use of highly elastic polymer solutions has been remarkably successful in elucidating the behavior of polymeric materials under flowing conditions. Here, we present the results of an extensive experimental study into the shear behavior of an athermal, dilute, binary polymer solution that is believed to be free of many of these effects. Under extended shearing, we observe the migration of polymer species: after shearing for several hundred hours, concentrations that are more than double the initial uniform value can be achieved. Although the solutions are well-described by dumbbell models in shear flows on short-time scales, theoretical predictions substantially underestimatemore » the rate of migration. Flow visualization and rheometric experiments suggest that the origin of this discrepancy could be the anomalous long-time rheology of these solutions. While these fluids display the well-known elastic instability in cone and plate flow above a critical Deborah number, extended shearing reveals that the toroidal secondary flow is eventually replaced by a purely azimuthal shearing flow. In addition, when sheared below the critical condition for the instability, the solutions exhibit a slow but reversible decay in normal stresses. The shear-induced migration of polymer species has been predicted by numerous theoretical studies. However, observations on the highly elastic polymer solutions that are most likely to show polymer migration, are complicated by a number of different physical processes that occur as a result of shearing. These phenomena, which include shear-induced phase separation, elastically-induced hydrodynamic instabilities, mixed solvent effects, shear-induced aggregation, and anomalous transient shear and normal stress behavior are often observed at times earlier than and at shear rates less than those where migration is predicted to occur; hence, the experimental detection of polymer migration has been thwarted by these other physical processes.« less

Studies on the effect of dispersoid(ZrO2) in PVdF-co-HFP based gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Sivakumar, M.; Subadevi, R.; Muthupradeepa, R.

2013-06-01

Gel polymer electrolytes containing poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) / Lithium bis(trifluoromethane sulfon)imide (LiTFSI) / mixture of ethylene carbonate and propylene carbonate (EC+PC) with different concendration of ZrO2 has been prepared using the solution casting technique. The conductivity of the prepared electrolyte sample has been determined by AC impedance technique in the range 303-353K. The temperature dependent ionic conductivity plot seems to obey VTF relation. The maximum ionic conductivity value of 4.46 × 10-3S/cm has been obtained for PVdF-co-HFP(32%) - LiTFSI(8%) - EC+PC (60%) + ZrO2(6wt%) based polymer electrolyte. The surface morphology of the prepared electrolyte sample has been studied using SEM.

Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

ERIC Educational Resources Information Center

Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

2011-01-01

This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

Polymer diffusion in the interphase between surface and solution.

PubMed

Weger, Lukas; Weidmann, Monika; Ali, Wael; Hildebrandt, Marcus; Gutmann, Jochen Stefan; Hoffmann-Jacobsen, Kerstin

2018-05-22

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of polyethylene glycol solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in solution is assigned to long range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling (D~N -1 ) indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale.

Solution-Based 3D Printing of Polymers of Intrinsic Microporosity.

PubMed

Zhang, Fengyi; Ma, Yao; Liao, Jianshan; Breedveld, Victor; Lively, Ryan P

2018-05-28

Current additive manufacturing methods have significant limitations in the classes of compatible polymers. Many polymers of significant technological interest cannot currently be 3D printed. Here, a generalizable method for 3D printing of viscous tenary polymer solutions (polymer/solvent/nonsolvent) is applied to both "intrinsically porous" (a polymer of intrinsic microporosity, PIM-1) and "intrinsically nonporous" (cellulose acetate) polymers. Successful ternary ink formulations require balancing of solution thermodynamics (phase separation), mass transfer (solvent evaporation), and rheology. As a demonstration, a microporous polymer (PIM-1) incompatible with current additive manufacturing technologies is 3D printed into a high-efficiency mass transfer contactor exhibiting hierarchical porosity ranging from sub-nanometer to millimeter pores. Short contactors (1.27 cm) can fully purify (<1 ppm) toluene vapor (1000 ppm) in N 2 gas for 1.7 h, which is six times longer than PIM-1 in traditional structures, and more than 4000 times the residence time of gas in the contactor. This solution-based additive manufacturing approach greatly extends the range of 3D-printable materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NMR investigations of self-aggregation characteristics of SDS in a model assembled tri-block copolymer solution.

PubMed

Kumar, B V N Phani; Priyadharsini, S Umayal; Prameela, G K S; Mandal, Asit Baran

2011-08-01

The present work was undertaken with a view to understand the influence of a model non-ionic tri-block copolymer PEO-PPO-PEO (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)) with molecular weight 5800 i.e., P123 [(EO)(20)-(PO)(70)-(EO)(20)] on the self-aggregation characteristics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D(2)O) using NMR chemical shift, self-diffusion and nuclear spin-relaxation as suitable experimental probes. In addition, polymer diffusion has been monitored as a function of SDS concentration. The concentration-dependent chemical shift, diffusion data and relaxation data indicated the significant interaction of polymeric micelles with SDS monomers and micelles at lower and intermediate concentrations of SDS, whereas the weak interaction of the polymer with SDS micelles at higher concentrations of SDS. It has been observed that SDS starts aggregating on the polymer at a lower concentration i.e., critical aggregation concentration (cac=1.94 mM) compared to polymer-free situation, and the onset of secondary micelle concentration (C(2)=27.16 mM) points out the saturation of the 0.2 wt% polymer or free SDS monomers/micelles at higher concentrations of SDS. It has also been observed that the parameter cac is almost independent in the polymer concentrations of study. The TMS (tetramethylsilane) has been used as a solubilizate to measure the bound diffusion coefficient of SDS-polymer mixed system. The self-diffusion data were analyzed using two-site exchange model and the obtained information on aggregation dynamics was commensurate with that inferred from chemical shift and relaxation data. The information on slow motions of polymer-SDS system was also extracted using spin-spin and spin-lattice relaxation rate measurements. The relaxation data points out the disintegration of polymer network at higher concentrations of SDS. The present NMR investigations have been well corroborated by surface tension and conductivity measurements. Copyright © 2011 Elsevier Inc. All rights reserved.

Transport and retention of surfactant- and polymer-stabilized engineered silver nanoparticles in silicate-dominated aquifer material.

PubMed

Adrian, Yorck F; Schneidewind, Uwe; Bradford, Scott A; Simunek, Jirka; Fernandez-Steeger, Tomas M; Azzam, Rafig

2018-05-01

Packed column experiments were conducted to investigate the transport and blocking behavior of surfactant- and polymer-stabilized engineered silver nanoparticles (Ag-ENPs) in saturated natural aquifer media with varying content of material < 0.063 mm in diameter (silt and clay fraction), background solution chemistry, and flow velocity. Breakthrough curves for Ag-ENPs exhibited blocking behavior that frequently produced a delay in arrival time in comparison to a conservative tracer that was dependent on the physicochemical conditions, and then a rapid increase in the effluent concentration of Ag-ENPs. This breakthrough behavior was accurately described using one or two irreversible retention sites that accounted for Langmuirian blocking on one site. Simulated values for the total retention rate coefficient and the maximum solid phase concentration of Ag-ENPs increased with increasing solution ionic strength, cation valence, clay and silt content, decreasing flow velocity, and for polymer-instead of surfactant-stabilized Ag-ENPs. Increased Ag-ENP retention with ionic strength occurred because of compression of the double layer and lower magnitudes in the zeta potential, whereas lower velocities increased the residence time and decreased the hydrodynamics forces. Enhanced Ag-ENP interactions with cation valence and clay were attributed to the creation of cation bridging in the presence of Ca 2+ . The delay in breakthrough was always more pronounced for polymer-than surfactant-stabilized Ag-ENPs, because of differences in the properties of the stabilizing agents and the magnitude of their zeta-potential was lower. Our results clearly indicate that the long-term transport behavior of Ag-ENPs in natural, silicate dominated aquifer material will be strongly dependent on blocking behavior that changes with the physicochemical conditions and enhanced Ag-ENP transport may occur when retention sites are filled. Copyright © 2018 Elsevier Ltd. All rights reserved.

Second virial coefficient of starch

NASA Astrophysics Data System (ADS)

Wohlfarth, Ch.

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Effects of surfactant micelles on viscosity and conductivity of poly(ethylene glycol) solutions

NASA Astrophysics Data System (ADS)

Wang, Shun-Cheng; Wei, Tzu-Chien; Chen, Wun-Bin; Tsao, Heng-Kwong

2004-03-01

The neutral polymer-micelle interaction is investigated for various surfactants by viscometry and electrical conductometry. In order to exclude the well-known necklace scenario, we consider aqueous solutions of low molecular weight poly(ethylene glycol) (2-20)×103, whose radial size is comparable to or smaller than micelles. The single-tail surfactants consist of anionic, cationic, and nonionic head groups. It is found that the viscosity of the polymer solution may be increased several times by micelles if weak attraction between a polymer segment and a surfactant exists, ɛ

In Vivo Biological Evaluation of High Molecular Weight Multifunctional Acid-Degradable Polymeric Drug Carriers with Structurally Different Ketals.

PubMed

Shenoi, Rajesh A; Abbina, Srinivas; Kizhakkedathu, Jayachandran N

2016-11-14

Understanding the influence of degradable chemical moieties on in vivo degradation, tissue distribution, and excretion is critical for the design of novel biodegradable drug carriers. Polyketals have recently emerged as a promising therapeutic delivery platform due to their ability to degrade under mild acidic intracellular compartments and generation of nontoxic degradation products. However, the effect of chemical structure of the ketal groups on the in vivo degradation, biodistribution, and pharmacokinetics of water-soluble ketal-containing polymers has not been explored. In the present work, we synthesized high molecular weight, water-soluble biodegradable hyperbranched polyglycerols (BHPGs) through the incorporation of structurally different ketal groups into the main chain of highly biocompatible polyglycerols. BHPGs showed pH and ketal group structure dependent degradation in buffer solutions. When the polymers were intravenously administered in mice, a strong dependence of in vivo degradation, biodistribution, and clearance on the ketal group structure was observed. All the BHPGs demonstrated degradation and clearance in vivo, with minimal tissue accumulation. Interestingly, an unanticipated degradation behavior of BHPGs with structurally different ketal groups was observed in vivo in comparison to their degradation in buffer solutions. BHPGs with cyclohexyl ketal (CHK) and cyclopentyl ketal (CPK) groups degraded much faster and were cleared from circulation much rapidly, while BHPG with glycerol hydroxy butanone ketal (GHBK) group degraded at a much slower rate and exhibited similar plasma half-life as that of nondegradable HPG. BHPG-GHBK also showed significantly lower tissue accumulation than nondegradable HPG after 30 days of administration. The difference in in vivo degradation may be attributed to the difference in hydrophobic characteristics of different ketal containing polymers, which may change their interaction with proteins and cells in vivo. This is the first study that demonstrates the influence of chemical structure of ketal groups on in vivo degradation and circulation profile of polymers, and through proper surface modifications, these polymers would be useful as multifunctional drug carriers.

Humidity-insensitive water evaporation from molecular complex fluids.

PubMed

Salmon, Jean-Baptiste; Doumenc, Frédéric; Guerrier, Béatrice

2017-09-01

We investigated theoretically water evaporation from concentrated supramolecular mixtures, such as solutions of polymers or amphiphilic molecules, using numerical resolutions of a one-dimensional model based on mass transport equations. Solvent evaporation leads to the formation of a concentrated solute layer at the drying interface, which slows down evaporation in a long-time-scale regime. In this regime, often referred to as the falling rate period, evaporation is dominated by diffusive mass transport within the solution, as already known. However, we demonstrate that, in this regime, the rate of evaporation does not also depend on the ambient humidity for many molecular complex fluids. Using analytical solutions in some limiting cases, we first demonstrate that a sharp decrease of the water chemical activity at high solute concentration leads to evaporation rates which depend weakly on the humidity, as the solute concentration at the drying interface slightly depends on the humidity. However, we also show that a strong decrease of the mutual diffusion coefficient of the solution enhances considerably this effect, leading to nearly independent evaporation rates over a wide range of humidity. The decrease of the mutual diffusion coefficient indeed induces strong concentration gradients at the drying interface, which shield the concentration profiles from humidity variations, except in a very thin region close to the drying interface.

Inhibition of the solid state transformation of carbamazepine in aqueous solution: impact of polymeric properties.

PubMed

Gift, Alan D; Hettenbaugh, Jacob A; Quandahl, Rachel A; Mapes, Madison

2017-11-06

The effects of polymers on the anhydrate-to-hydrate transformation of carbamazepine (CBZ) was investigated. The three types of polymers studied were polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and substituted celluloses which included hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC). Anhydrous CBZ was added to dilute aqueous polymer solutions and Raman spectroscopy measurements were collected to monitor the kinetics of the solution-mediated transformation to CBZ dihydrate. Polymers exhibiting the greatest inhibition were able to reduce the growth phase of the solution-mediated transformation and change the habit of the hydrate crystal indicating polymer adsorption to the hydrate crystal surface as the mechanism of inhibition. The results of the various polymers showed that short chain substituted celluloses (HPMC and MC) inhibited the CBZ transformation to a much greater extent than longer chains. The same trend was observed for PVP and PVA, but to a lesser extent. These chain length effects were attributed to changes in polymer confirmation when adsorbed on the crystal surface. Additionally, decreasing the percentage of hydroxyl groups on the PVA polymer backbone reduced the ability of the polymer to inhibit the transformation and changing the degree of substitutions of methyl and hydroxypropyl groups on the cellulosic polymer backbone had no effect on the transformation.

Second virial coefficient of hydroxypropyl starch

NASA Astrophysics Data System (ADS)

Wohlfarth, Ch.

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Bulk Heterojunction versus Diffused Bilayer: The Role of Device Geometry in Solution p-Doped Polymer-Based Solar Cells.

PubMed

Loiudice, Anna; Rizzo, Aurora; Biasiucci, Mariano; Gigli, Giuseppe

2012-07-19

We exploit the effect of molecular p-type doping of P3HT in diffused bilayer (DB) polymer solar cells. In this alternative device geometry, the p-doping is accomplished in solution by blending the F4-TCNQ with P3HT. The p-doping both increases the film conductivity and reduces the potential barrier at the interface with the electrode. This results in an excellent power conversion efficiency of 4.02%, which is an improvement of ∼48% over the p-doped standard bulk heterojunction (BHJ) device. Combined VOC-light intensity dependence measurements and Kelvin probe force microscopy reveal that the DB device configuration is particularly advantageous, if compared to the conventional BHJ, because it enables optimization of the donor and acceptor layers independently to minimize the effect of trapping and to fully exploit the improved transport properties.

The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badita, C. R., E-mail: ramona@tandem.nipne.ro; University of Bucharest, Faculty of Physics, Atomiştilor 405, CP MG - 11, RO – 077125, Bucharest-Magurele; Aranghel, D., E-mail: daranghe@nipne.ro

2016-03-25

Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca{sup 2+} ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca{supmore » 2+} concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.« less

The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Badita, C. R.; Aranghel, D.; Radulescu, A.; Anitas, E. M.

2016-03-01

Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca2+ ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca2+ concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.

A novel model of photothermal diffusion (PTD) for polymer nano-composite semiconducting of thin circular plate

NASA Astrophysics Data System (ADS)

Lotfy, Kh.

2018-05-01

In this article, theoretical discussions for a novel mathematical-physical Photothermal diffusion (PTD) model in the generalized thermoelasticity theory with photothermal processes and chemical action are introduced. The mean idea of this model depends on the interaction between quasi-particles (plasma waves) that depends on the kind of the used materials, the mechanical forces acting on the surface, the generalized thermo and mass diffusion (due to coupling of temperature fields with thermal waves and chemical potential) and the elastic waves. The one dimensional Laplace transforms is used to obtain the exact solution for some physical and chemical quantities for a thin circular plate of a semiconducting polymer nanocomposite such as silicon (Si). New variables are deduced and discussed. The obtained results of the physical quantities are presented analytically and illustrated graphically with some important applications.

Preparation and release characteristics of polymer-coated and blended alginate microspheres.

PubMed

Lee, D W; Hwang, S J; Park, J B; Park, H J

2003-01-01

To prevent a rapid drug release from alginate microspheres in simulated intestinal media, alginate microspheres were coated or blended with polymers. Three polymers were selected and evaluated such as HPMC, Eudragit RS 30D and chitosan, as both coating materials and additive polymers for controlling the drug release. This study focused on the release characteristics of polymer-coated and blended alginate microspheres, varying the type of polymer and its concentration. The alginate microspheres were prepared by dropping the mixture of drug and sodium alginate into CaCl(2) solution using a spray-gun. Polymer-coated microspheres were prepared by adding alginate microspheres into polymer solution with mild stirring. Polymer-blended microspheres were prepared by dropping the mixture of drug, sodium alginate and additive polymer with plasticizer into CaCl(2) solution. In vitro release test was carried out to investigate the release profiles in 500 ml of phosphate buffered saline (PBS, pH 7.4). As the amount of polymer in sodium alginate or coating solution increase, the drug release generally decreased. HPMC-blended microspheres swelled but withstood the disintegration, showing an ideal linear release profiles. Chitosan-coated microspheres showed smooth and round surface and extended the release of drug. In comparison with chitosan-coated microspheres, HPMC-blended alginate microspheres can be easily made and used for controlled drug delivery systems due to convenient process and controlled drug release.

Micropollutant sorption to membrane polymers: a review of mechanisms for estrogens.

PubMed

Schäfer, Andrea I; Akanyeti, Ime; Semião, Andrea J C

2011-05-11

Organic micropollutants such as estrogens occur in water in increasing quantities from predominantly anthropogenic sources. In water such micropollutants partition not only to surfaces such as membrane polymers but also to any other natural or treatment related surfaces. Such interactions are often observed as sorption in treatment processes and this phenomenon is exploited in activated carbon filtration, for example. Sorption is important for polymeric materials and this is used for the concentration of such micropollutants for analytical purposes in solid phase extraction. In membrane filtration the mechanism of micropollutant sorption is a relatively new discovery that was facilitated through new analytical techniques. This sorption plays an important role in micropollutant retention by membranes although mechanisms of interaction are to date not understood. This review is focused on sorption of estrogens on polymeric surfaces, specifically membrane polymers. Such sorption has been observed to a large extent with values of up to 1.2 ng/cm(2) measured. Sorption is dependent on the type of polymer, micropollutant characteristics, solution chemistry, membrane operating conditions as well as membrane morphology. Likely contributors to sorption are the surface roughness as well as the microporosity of such polymers. While retention-and/or reflection coefficient as well as solute to effective pore size ratio-controls the access of such micropollutants to the inner surface, pore size, porosity and thickness as well as morphology or shape of inner voids determines the available area for sorption. The interaction mechanisms are governed, most likely, by hydrophobic as well as solvation effects and interplay of molecular and supramolecular interactions such as hydrogen bonding, π-cation/anion interactions, π-π stacking, ion-dipole and dipole-dipole interactions, the extent of which is naturally dependent on micropollutant and polymer characteristics. Systematic investigations are required to identify and quantify both relative contributions and strength of such interactions and develop suitable surface characterisation tools. This is a difficult endeavour given the complexity of systems, the possibility of several interactions taking place simultaneously and the generally weaker forces involved. Copyright © 2010 Elsevier B.V. All rights reserved.

Formalism for calculation of polymer-solvent-mediated potential

NASA Astrophysics Data System (ADS)

Zhou, Shiqi

2006-07-01

A simple theoretical approach is proposed for calculation of a solvent-mediated potential (SMP) between two colloid particles immersed in a polymer solvent bath in which the polymer is modeled as a chain with intramolecular degrees of freedom. The present recipe is only concerned with the estimation of the density profile of a polymer site around a single solute colloid particle instead of two solute colloid particles separated by a varying distance as done in existing calculational methods for polymer-SMP. Therefore the present recipe is far simpler for numerical implementation than the existing methods. The resultant predictions for the polymer-SMP and polymer solvent-mediated mean force (polymer-SMMF) are in very good agreement with available simulation data. With the present recipe, change tendencies of the contact value and second virial coefficiency of the SMP as a function of size ratio between the colloid particle and polymer site, the number of sites per chain, and the polymer concentration are investigated in detail. The metastable critical polymer concentration as a function of size ratio and the number of sites per chain is also reported for the first time. To yield the numerical solution of the present recipe at less than 1min on a personal computer, a rapid and accurate algorithm for the numerical solution of the classical density functional theory is proposed to supply rapid and accurate estimation of the density profile of the polymer site as an input into the present formalism.

How Does a Hydrophobic Macromolecule Respond to Mixed Osmolyte Environment?

PubMed

Tah, Indrajit; Mondal, Jagannath

2016-10-04

The role of the protecting osmolyte Trimethyl N-oxide (TMAO) in counteracting the denaturing effect of urea on a protein is quite well established. However, the mechanistic role of osmolytes on the hydrophobic interaction underlying protein folding is a topic of contention and is emerging as a key area of biophysical interest. Although recent experiment and computer simulation have established that individual aqueous solution of TMAO and urea respectively stabilizes and destabilizes the collapsed conformation of a hydrophobic polymer, it remains to be explored how a mixed aqueous solution of protecting and denaturing osmolytes influences the conformations of the polymer. In order to bridge the gap, we have simulated the conformational behavior of both a model hydrophobic polymer and a synthetic polymer polystyrene in an aqueous mixture of TMAO and urea. Intriguingly, our free energy based simulations on both the systems show that even though a pure aqueous solution of TMAO stabilizes the collapsed or globular conformation of the hydrophobic polymer, addition of TMAO to an aqueous solution of urea further destabilizes the collapsed conformation of the hydrophobic polymer. We also observe that the extent of destabilization in a mixed osmolyte solution is relatively higher than that in pure aqueous urea solution. The reinforcement of the denaturation effect of the hydrophobic macromolecule in a mixed osmolyte solution is in stark contrast to the well-known counteracting role of TMAO in proteins under denaturing condition of urea. In both model and realistic systems, our results show that in a mixed aqueous solution, greater number of cosolutes preferentially bind to the extended conformation of the polymer relative to that in the collapsed conformation, thereby complying with Tanford-Wyman preferential solvation theory disfavoring the collapsed conformation. The results are robust across a range of osmolyte concentrations and multiple cosolute forcefields. Our findings unequivocally imply that the action of mixed osmolyte solution on hydrophobic polymer is significantly distinct from that of proteins.

Use DNA solutions to model polymer entanglement in flow: simultaneous rheometric and particle-tracking velocimetric measurements

NASA Astrophysics Data System (ADS)

Boukany, Pouyan; Wang, Shi-Qing

2008-03-01

Entangled aqueous DNA solutions are ideal as a model system to examine nonlinear flow features including stress overshoot in startup shear and shear thinning phenomenon. These soft systems can be strongly entangled with 60 entanglement points per chain and a terminal relaxation time as long as 1000 s at 1 % concentration [1-2]. They allow a comparison between the steady state attained with a startup shear and that attained through an ``infinitely'' slow ramping up of the applied shear rate. Indeed, startup shear in the nonlinear (stress plateau) region causes the DNA solutions to yield inhomogeneously, resulting in permanent shear banding. However, the slowly ramped-up shear into the same final rate as applied in startup shear allowed the solutions to avoid shear inhomogeneity. Thus, we demonstrated that it is possible for the final steady states to be different depending on how an entangled system is brought into the same final experimental condition. This result implies that it is ill-defined to pursue conventional constitutive relationship in flow of entangled polymers. [1] Boukany, P. E.; Hu, T. H.; Wang, S. Q. textitMacromolecules 2007, under review. [2] Boukany, P. E.; Wang, S. Q. J. Rheol. 2007, under review.

Preparation and characterization of MWCNT nanofiller incorporated polymer composite for lithium battery applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradeepa, P.; Raj, S. Edwin; Selvakumar, K.

Poly (ethyl methacrylate) based polymer electrolyte films were prepared by solution casting technique incorporating multi-walled carbon nanotube (MWCNT) as filler and characterized using XRD and Ac impedance analysis. The electrical conductivity is increased with increasing filler concentration (upto 6wt %), which is attributed to the formation of charge transfer complexes. The maximum ionic conductivity value is found to be 1.171×10{sup −3} Scm{sup −1} at 303K for PEMA (19wt %) -LiClO{sub 4} (8wt %) -MWCNT (6wt %) -PC (67wt %) electrolyte system. The temperature dependent ionic conductivity plot seems to obey Vogel -Tamman-Fulcher relation.

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.; Baklagina, Yu. G.; Romanov, D. P.; Kononova, S. V.; Volod'ko, A. V.; Ermak, I. M.; Klechkovskaya, V. V.; Skorik, Yu. A.

2016-11-01

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan-hyaluronic acid, chitosan-alginic acid, and chitosan-carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Effect of polymers in solution culture on growth and mineral composition of tomatoes. [Lycopersicon esculentum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, A.

Tomato (Lycopersicon esculentum Mill. cv. Tropic) plants were grown for 26 days from transplanting in full nutrient solution with and without polymers in nutrient solution at two different pH values. An aninoic polyacrylamide and a polysaccharide (from guar bean) each at 100 mg L/sup -1/ in solution slightly improved yields at both pH values. A cationic polymer at the same concentration decreased yields. There were no apparent nutritional reasons for the effects. 1 table.

From intermediate anisotropic to isotropic friction at large strain rates to account for viscosity thickening in polymer solutions

NASA Astrophysics Data System (ADS)

Stephanou, Pavlos S.; Kröger, Martin

2018-05-01

The steady-state extensional viscosity of dense polymeric liquids in elongational flows is known to be peculiar in the sense that for entangled polymer melts it monotonically decreases—whereas for concentrated polymer solutions it increases—with increasing strain rate beyond the inverse Rouse time. To shed light on this issue, we solve the kinetic theory model for concentrated polymer solutions and entangled melts proposed by Curtiss and Bird, also known as the tumbling-snake model, supplemented by a variable link tension coefficient that we relate to the uniaxial nematic order parameter of the polymer. As a result, the friction tensor is increasingly becoming isotropic at large strain rates as the polymer concentration decreases, and the model is seen to capture the experimentally observed behavior. Additional refinements may supplement the present model to capture very strong flows. We furthermore derive analytic expressions for small rates and the linear viscoelastic behavior. This work builds upon our earlier work on the use of the tumbling-snake model under shear and demonstrates its capacity to improve our microscopic understanding of the rheology of entangled polymer melts and concentrated polymer solutions.

Nanostructures and nanosecond dynamics at the polymer/filler interface

NASA Astrophysics Data System (ADS)

Koga, Tad; Barkley, Deborah; Endoh, Maya; Masui, Tomomi; Kishimoto, Hiroyuki; Nagao, Michihiro; Taniguchi, Takashi

We report in-situ nanostructures and nanosecond dynamics of polybutadiene (PB) chains bound to carbon black (CB) fillers (the so-called ``bound polymer layer (BPL)'') in polymer solutions (from dilute to concentrated solutions). The BPL on the CB fillers were extracted by solvent leaching of a CB-filled PB compound and subsequently dispersed in deuterated toluene (a good solvent) to label the BPL for ``contrast-matching'' small-angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. The SANS results demonstrate that the BPL is composed of two regions regardless of molecular weights of PB: the inner unswollen region of 0.5 nm thick and outer swollen region where the polymer chains display a parabolic profile with a diffuse tail. In addition, the NSE results show that the dynamics of the swollen bound chains in the polymer solutions can be explained by the collective dynamics, the so-called ``breathing mode''. Intriguingly, it was also indicative that the collective dynamics is independent of the polymer concentrations and is much faster than that predicted from the solution viscosity. We will discuss the mechanism at the bound polymer-free polymer interface at the nanometer scale. T.K. acknowledges the financial support from NSF Grant (CMMI-1332499).

Probing solvation decay length in order to characterize hydrophobicity-induced bead-bead attractive interactions in polymer chains.

PubMed

Das, Siddhartha; Chakraborty, Suman

2011-08-01

In this paper, we quantitatively demonstrate that exponentially decaying attractive potentials can effectively mimic strong hydrophobic interactions between monomer units of a polymer chain dissolved in aqueous solvent. Classical approaches to modeling hydrophobic solvation interactions are based on invariant attractive length scales. However, we demonstrate here that the solvation interaction decay length may need to be posed as a function of the relative separation distances and the sizes of the interacting species (or beads or monomers) to replicate the necessary physical interactions. As an illustrative example, we derive a universal scaling relationship for a given solute-solvent combination between the solvation decay length, the bead radius, and the distance between the interacting beads. With our formalism, the hydrophobic component of the net attractive interaction between monomer units can be synergistically accounted for within the unified framework of a simple exponentially decaying potential law, where the characteristic decay length incorporates the distinctive and critical physical features of the underlying interaction. The present formalism, even in a mesoscopic computational framework, is capable of incorporating the essential physics of the appropriate solute-size dependence and solvent-interaction dependence in the hydrophobic force estimation, without explicitly resolving the underlying molecular level details.

Polymers in the gut compress the colonic mucus hydrogel.

PubMed

Datta, Sujit S; Preska Steinberg, Asher; Ismagilov, Rustem F

2016-06-28

Colonic mucus is a key biological hydrogel that protects the gut from infection and physical damage and mediates host-microbe interactions and drug delivery. However, little is known about how its structure is influenced by materials it comes into contact with regularly. For example, the gut abounds in polymers such as dietary fibers or administered therapeutics, yet whether such polymers interact with the mucus hydrogel, and if so, how, remains unclear. Although several biological processes have been identified as potential regulators of mucus structure, the polymeric composition of the gut environment has been ignored. Here, we demonstrate that gut polymers do in fact regulate mucus hydrogel structure, and that polymer-mucus interactions can be described using a thermodynamic model based on Flory-Huggins solution theory. We found that both dietary and therapeutic polymers dramatically compressed murine colonic mucus ex vivo and in vivo. This behavior depended strongly on both polymer concentration and molecular weight, in agreement with the predictions of our thermodynamic model. Moreover, exposure to polymer-rich luminal fluid from germ-free mice strongly compressed the mucus hydrogel, whereas exposure to luminal fluid from specific-pathogen-free mice-whose microbiota degrade gut polymers-did not; this suggests that gut microbes modulate mucus structure by degrading polymers. These findings highlight the role of mucus as a responsive biomaterial, and reveal a mechanism of mucus restructuring that must be integrated into the design and interpretation of studies involving therapeutic polymers, dietary fibers, and fiber-degrading gut microbes.

Polymer-induced phase separation and crystallization in immunoglobulin G solutions.

PubMed

Li, Jianguo; Rajagopalan, Raj; Jiang, Jianwen

2008-05-28

We study the effects of the size of polymer additives and ionic strength on the phase behavior of a nonglobular protein-immunoglobulin G (IgG)-by using a simple four-site model to mimic the shape of IgG. The interaction potential between the protein molecules consists of a Derjaguin-Landau-Verwey-Overbeek-type colloidal potential and an Asakura-Oosawa depletion potential arising from the addition of polymer. Liquid-liquid equilibria and fluid-solid equilibria are calculated by using the Gibbs ensemble Monte Carlo technique and the Gibbs-Duhem integration (GDI) method, respectively. Absolute Helmholtz energy is also calculated to get an initial coexisting point as required by GDI. The results reveal a nonmonotonic dependence of the critical polymer concentration rho(PEG) (*) (i.e., the minimum polymer concentration needed to induce liquid-liquid phase separation) on the polymer-to-protein size ratio q (equivalently, the range of the polymer-induced depletion interaction potential). We have developed a simple equation for estimating the minimum amount of polymer needed to induce the liquid-liquid phase separation and show that rho(PEG) (*) approximately [q(1+q)(3)]. The results also show that the liquid-liquid phase separation is metastable for low-molecular weight polymers (q=0.2) but stable at large molecular weights (q=1.0), thereby indicating that small sizes of polymer are required for protein crystallization. The simulation results provide practical guidelines for the selection of polymer size and ionic strength for protein phase separation and crystallization.

Preparation of poly(acrylamide-co-acrylic acid)-grafted gum and its flocculation and biodegradation studies.

PubMed

Mittal, H; Mishra, Shivani B; Mishra, A K; Kaith, B S; Jindal, R; Kalia, S

2013-10-15

Biodegradation studies of Gum ghatti (Gg) and acrylamide-co-acrylic acid based flocculants [Gg-cl-poly(AAm-co-AA)] have been reported using the soil composting method. Gg-cl-poly(AAm-co-AA) was found to degrade 89.76% within 60 days. The progress of biodegradation at each stage was monitored through FT-IR and SEM. Polymer was synthesized under pressure using potassium persulphate-ascorbic acid as a redox initiator and N,N'-methylene-bis-acrylamide as a crosslinker. Synthesized polymer was found to show pH, temperature and ionic strength of the cations dependent swelling behavior. Gg-cl-poly(AAm-co-AA) was utilized for the selective absorption of saline from different petroleum fraction-saline emulsions. The flocculation efficiency of the polymer was studied as a function of polymer dose, temperature and pH of the solution. Gg-cl-poly(AAm-co-AA) showed maximum flocculation efficiency with 20 mol L(-1) polymer dose in acidic medium at 50 °C. Copyright © 2013. Published by Elsevier Ltd.

Structural and optical characterization of PVA:KMnO4 based solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Abdullah, Omed Gh.; Aziz, Shujahadeen B.; Rasheed, Mariwan A.

Solid polymer electrolyte films of polyvinyl alcohol (PVA) doped with a different weight percent of potassium permanganate (KMnO4) were prepared by standard solution cast method. XRD and FTIR techniques were performed for structural study. Complex formation between the PVA polymer and KMnO4 salt was confirmed by Fourier transform infrared (FTIR) spectroscopy. The description of crystalline nature of the solid polymer electrolyte films has been confirmed by XRD analysis. The UV-Visible absorption spectra were analyzed in terms of absorption formula for non-crystalline materials. The fundamental optical parameters such as optical band gap energy, refractive index, optical conductivity, and dielectric constants have been investigated and showed a clear dependence on the KMnO4 concentration. The observed value of optical band gap energy for pure PVA is about 6.27 eV and decreases to a value 3.12 eV for the film sample formed with 4 wt% KMnO4 salt. The calculated values of refractive index and the dielectric constants of the polymer electrolyte films increase with increasing KMnO4 content.

Visibly transparent polymer solar cells produced by solution processing.

PubMed

Chen, Chun-Chao; Dou, Letian; Zhu, Rui; Chung, Choong-Heui; Song, Tze-Bin; Zheng, Yue Bing; Hawks, Steve; Li, Gang; Weiss, Paul S; Yang, Yang

2012-08-28

Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons. The top transparent electrode employs a highly transparent silver nanowire-metal oxide composite conducting film, which is coated through mild solution processes. With this combination, we have achieved 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells. The optimized devices have a maximum transparency of 66% at 550 nm.

Nanocellular foam with solid flame retardant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liang; Kelly-Rowley, Anne M.; Bunker, Shana P.

Prepare nanofoam by (a) providing an aqueous solution of a flame retardant dissolved in an aqueous solvent, wherein the flame retardant is a solid at 23.degree. C. and 101 kiloPascals pressure when in neat form; (b) providing a fluid polymer composition selected from a solution of polymer dissolved in a water-miscible solvent or a latex of polymer particles in a continuous aqueous phase; (c) mixing the aqueous solution of flame retardant with the fluid polymer composition to form a mixture; (d) removing water and, if present, solvent from the mixture to produce a polymeric composition having less than 74 weight-percentmore » flame retardant based on total polymeric composition weight; (e) compound the polymeric composition with a matrix polymer to form a matrix polymer composition; and (f) foam the matrix polymer composition into nanofoam having a porosity of at least 60 percent.« less

Ultrasound degradation of xanthan polymer in aqueous solution: Its scission mechanism and the effect of NaCl incorporation.

PubMed

Saleh, H M; Annuar, M S M; Simarani, K

2017-11-01

Degradation of xanthan polymer in aqueous solution by ultrasonic irradiation was investigated. The effects of selected variables i.e. sonication intensity, irradiation time, concentration of xanthan gum and molar concentration of NaCl in solution were studied. Combined approach of full factorial design and conventional one-factor-at-a-time was applied to obtain optimum degradation at sonication power intensity of 11.5Wcm -2 , irradiation time 120min and 0.1gL -1 xanthan in a salt-free solution. Molecular weight reduction of xanthan gum under sonication was described by an exponential decay function with higher rate constant for polymer degradation in the salt free solution. The limiting molecular weight where fragments no longer undergo scission was determined from the function. The incorporation of NaCl in xanthan solution resulted in a lower limiting molecular weight. The ultrasound-mediated degradation of aqueous xanthan polymer chain agreed with a random scission model. Side chain of xanthan polymer is proposed to be the primary site of scission action. Copyright © 2017 Elsevier B.V. All rights reserved.

Drag reducing properties of microalgal exopolymers.

PubMed

Ramus, J; Kenney, B E; Shaughnessy, E J

1989-01-25

Dilute aqueous solutions of polymers released by marine phytoplankton (microalgae) were shown to effectively reduce drag in capillary pipe flow. Tests were performed in a capillary turbulent flow viscometer which extruded small samples under high pressures. In all, 22 species were screened, and the products of one chlorophyte and four rhodophyte species proved especially effective. The viscoelastic polymers produced by these species delayed the transition from laminar to turbulent flow to significantly higher Re. In general, polymeric regime segments come off the maximum drag reduction asymptote at characteristic retro-onset points, and come to lie approximately parallel to, but displaced upwards from the Prandtl-von Karman line. The delay to transition was shown to be dependent on additive polymer concentration, capillary diameter, and temperature. Ionic concentration, ionic composition, or pH had little effect on drag reducing properties.

Stereoselectivity in ene reactions with 1O2: matrix effects in polymer supports, photo-oxygenation of organic salts and asymmetric synthesis.

PubMed

Griesbeck, Axel G; Bartoschek, Anna; Neudörfl, Jörg; Miara, Claus

2006-01-01

The ene reaction of chiral allylic alcohols is applied as a tool for the investigation of intrapolymer effects by means of the stereoselectivity of the singlet-oxygen addition. The diastereo selectivity strongly depends on the structure of the polymer, the substrate loading degree and also on the degree of conversion demonstrating additional supramolecular effects evolving during the reaction. The efficiency and the stability of polymer-bound sensitizers were evaluated by the ene reaction of singlet oxygen with citronellol. The ene reaction with chiral ammonium salts of tiglic acid was conducted under solution phase conditions or in polystyrene beads under chiral contact ion-pair conditions. The products thus obtained precipitate during the photoreaction as ammonium salts. Moderate asymmetric induction was observed for this procedure for the first time.

The impact of fullerenes on the ordering of polyacrylonitrile during nanocomposites formation

DOE PAGES

Imel, Adam E.; Dadmun, Mark D.

2015-08-18

The production of polymer nanocomposites from solution consists of the mixing of the polymer and nanoparticle in solution and subsequent evaporation of the solvent. Here, we examine the formation of polyacrylonitrile and C60 fullerene nanocomposites, with a focus on monitoring these two steps.This study indicates that the nanoparticles are individually dispersed with the polymer chains in solution prior to deposition and in the final film. As the solution becomes more concentrated, the nanoparticles are sequestered to the outer edges of the polymer crystals, altering the detected crystal structure. The self-assembled structure of the crystalline polymer is directed by the additionmore » of C 60 and manifests itself as a peak in small-angle X-ray scattering on a length scale of ~150 . Moreover, our results suggest that the non-covalent molecular interactions between C60 and polyacrylonitrile matrix are sufficiently strong to alter the self-assembled morphology of the polymer and the meso- and nanoscale structures in the nanocomposite.« less

Equilibrium water and solute uptake in silicone hydrogels.

PubMed

Liu, D E; Dursch, T J; Oh, Y; Bregante, D T; Chan, S Y; Radke, C J

2015-05-01

Equilibrium water content of and solute partitioning in silicone hydrogels (SiHys) are investigated using gravimetric analysis, fluorescence confocal laser-scanning microscopy (FCLSM), and back extraction with UV/Vis-absorption spectrophotometry. Synthesized silicone hydrogels consist of silicone monomer, hydrophilic monomer, cross-linking agent, and triblock-copolymer macromer used as an amphiphilic compatibilizer to prevent macrophase separation. In all cases, immiscibility of the silicone and hydrophilic polymers results in microphase-separated morphologies. To investigate solute uptake in each of the SiHy microphases, equilibrium partition coefficients are obtained for two hydrophilic solutes (i.e., theophylline and caffeine dissolved in aqueous phosphate-buffered saline) and two oleophilic solutes (i.e., Nile Red and Bodipy Green dissolved in silicone oil), respectively. Measured water contents and aqueous-solute partition coefficients increase linearly with increasing solvent-free hydrophilic-polymer volume fraction. Conversely, oleophilic-solute partition coefficients decrease linearly with rising solvent-free hydrophilic-polymer volume fraction (i.e., decreasing hydrophobic silicone-polymer fraction). We quantitatively predict equilibrium SiHy water and solute uptake assuming that water and aqueous solutes reside only in hydrophilic microdomains, whereas oleophilic solutes partition predominately into silicone microdomains. Predicted water contents and solute partition coefficients are in excellent agreement with experiment. Our new procedure permits a priori estimation of SiHy water contents and solute partition coefficients based solely on properties of silicone and hydrophilic homopolymer hydrogels, eliminating the need for further mixed-polymer-hydrogel experiments. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Low density microcellular foams

DOEpatents

Aubert, J.H.; Clough, R.L.; Curro, J.G.; Quintana, C.A.; Russick, E.M.; Shaw, M.T.

1985-10-02

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the reusltant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 ..mu..m and a volume such that the foams have a length greater than 1 cm are provided.

Effect of Processing Parameters on the Morphology of PVDF Electrospun Nanofiber

NASA Astrophysics Data System (ADS)

Zulfikar, M. A.; Afrianingsih, I.; Nasir, M.; Alni, A.

2018-03-01

Electrospinning is a process that produces continuous polymer fibers with diameters in the submicron range through the action of an external electric field imposed on a polymer solution or melt. Because of the tiny diameter in several hundreds of nanometers and the high porosity, electrospun membranes show potential applications in extensive areas such as filtration systems, biomedical tissue templates, drug delivery membranes, and so on. In the electrospinning process, some parameters such as polymer concentration, feeding rate of the polymer solution, additives, humidity, viscosity, surface tension, applied voltage, and nozzle-to ground collector distance will affect the fiber diameter and morphology. In this work, we have evaluated the effects of two processing parameters including the flow rate of the polymer solution and nozzle-to ground collector distance, on the morphology of the fibers formed. The solutions used in the electrospinning experiments were prepared using Poly(vinylidene fluoride) (PVDF). This material was dissolved in N,N-dimethylformamide (DMF) to make solutions with concentrations of 20 wt%. These solutions was electrospun using a 5 mL plastic syringe with an 8 gauge stainless needle at an applied voltage of 20.0 kV, a flow rate of 0.02-0.04 mL/min and nozzle-to ground collector distance of 12 and 15 cm. Electrospinning of PVDF polymer solution was performed in horizontal alignment having a grounded aluminum foil which serves as a collector. The nanofibers obtained were characterized by polarizing optical microscope. We find that the low flow rate of the polymer solution and nozzle-to ground collector distance are strongly correlated with the formation of bead defects in the fibers.

Mechanical transduction via a single soft polymer

NASA Astrophysics Data System (ADS)

Hou, Ruizheng; Wang, Nan; Bao, Weizhu; Wang, Zhisong

2018-04-01

Molecular machines from biology and nanotechnology often depend on soft structures to perform mechanical functions, but the underlying mechanisms and advantages or disadvantages over rigid structures are not fully understood. We report here a rigorous study of mechanical transduction along a single soft polymer based on exact solutions to the realistic three-dimensional wormlike-chain model and augmented with analytical relations derived from simpler polymer models. The results reveal surprisingly that a soft polymer with vanishingly small persistence length below a single chemical bond still transduces biased displacement and mechanical work up to practically significant amounts. This "soft" approach possesses unique advantages over the conventional wisdom of rigidity-based transduction, and potentially leads to a unified mechanism for effective allosterylike transduction and relay of mechanical actions, information, control, and molecules from one position to another in molecular devices and motors. This study also identifies an entropy limit unique to the soft transduction, and thereby suggests a possibility of detecting higher efficiency for kinesin motor and mutants in future experiments.

Diels-Alder Trapping of Photochemically Generated o-Quinodimethane Intermediates: An Alternative Route to Photocured Polymer Film Development

NASA Technical Reports Server (NTRS)

Tyson, Daniel S.; Ilhan, Faysal; Meador, Mary Ann B.; Smith, Dee Dee; Scheiman, Daniel A.; Meador, Michael A.

2004-01-01

Photolysis of o-methylphenyl ketones generates bis-o-quinodimethane intermediates that can be trapped in situ by dienophiles through Diels-Alder cycloadditions. This well-known photochemical process is applied to a series of six new photoreactive monomers containing bis-(o-methylphenyl ketone) functionalities combined with diacrylate and triacrylate ester monomers for the development of acrylic ester copolymer blends. Irradiation of cyclohexanone solutions of the bis-(o-methylphenyl ketone)s and acrylate esters produce thin polymer films. Solid state 13C NMR data indicated 47- 100% reaction of the bis-(o-methylphenyl ketone)s, depending on experimental conditions, to yield the desired products. DSC and TGA analyses were performed to determine the glass transition temperature, T,, and onset of decomposition, Td, of the resulting polymer films. A statistical Design of Experiments approach was used to obtain a systematic understanding of the effects of experimental variables on the extent of polymerization and the final polymer properties.

Conformations of low-molecular-weight lignin polymers in water

DOE PAGES

Petridis, Loukas; Smith, Jeremy C.

2016-01-13

Low-molecular-weight lignin binds to cellulose during the thermochemical pretreatment of biomass for biofuel production, which prevents the efficient hydrolysis of the cellulose to sugars. The binding properties of lignin are influenced strongly by the conformations it adopts. Here, we use molecular dynamics simulations in aqueous solution to investigate the dependence of the shape of lignin polymers on chain length and temperature. Lignin is found to adopt collapsed conformations in water at 300 and 500 K. However, at 300 K, a discontinuous transition is found in the shape of the polymer as a function of the chain length. Below a criticalmore » degree of polymerization, N c=15, the polymer adopts less spherical conformations than above N c. The transition disappears at high temperatures (500 K) at which only spherical shapes are adopted. As a result, an implication relevant to cellulosic biofuel production is that lignin will self-aggregate even at high pretreatment temperatures.« less

Conformations of Low-Molecular-Weight Lignin Polymers in Water.

PubMed

Petridis, Loukas; Smith, Jeremy C

2016-02-08

Low-molecular-weight lignin binds to cellulose during the thermochemical pretreatment of biomass for biofuel production, which prevents the efficient hydrolysis of the cellulose to sugars. The binding properties of lignin are influenced strongly by the conformations it adopts. Here, we use molecular dynamics simulations in aqueous solution to investigate the dependence of the shape of lignin polymers on chain length and temperature. Lignin is found to adopt collapsed conformations in water at 300 and 500 K. However, at 300 K, a discontinuous transition is found in the shape of the polymer as a function of the chain length. Below a critical degree of polymerization, Nc =15, the polymer adopts less spherical conformations than above Nc. The transition disappears at high temperatures (500 K) at which only spherical shapes are adopted. An implication relevant to cellulosic biofuel production is that lignin will self-aggregate even at high pretreatment temperatures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions.

PubMed

Berts, Ida; Fragneto, Giovanna; Hilborn, Jöns; Rennie, Adrian R

2013-07-01

The present paper investigates the structure and composition of grafted sodium hyaluronan at a solid-liquid interface using neutron reflection. The solvated polymer at the surface could be described with a density profile that decays exponentially towards the bulk solution. The density profile of the polymer varied depending on the deposition protocol. A single-stage deposition resulted in denser polymer layers, while layers created with a two-stage deposition process were more diffuse and had an overall lower density. Despite the diffuse density profile, two-stage deposition leads to a higher surface excess. Addition of calcium ions causes a strong collapse of the sodium hyaluronan chains, increasing the polymer density near the surface. This effect is more pronounced on the sample prepared by two-stage deposition due to the initial less dense profile. This study provides an understanding at a molecular level of how surface functionalization alters the structure and how surface layers respond to changes in calcium ions in the solvent.

FOR STIMULI-RESPONSIVE POLYMERS WITH ENHANCED EFFICIENCY IN RESERVOIR RECOVERY PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles McCormick; Roger Hester

To date, our synthetic research efforts have been focused on the development of stimuli-responsive water-soluble polymers designed for use in enhanced oil recovery (EOR) applications. These model systems are structurally tailored for potential application as viscosifiers and/or mobility control agents for secondary and tertiary EOR methods. The following report discloses the progress of our ongoing research of polyzwitterions, polymers derived from monomers bearing both positive and negative charges, that show the ability to sustain or increase their hydrodynamic volume (and thus, solution viscosity) in the presence of electrolytes. Such polymers appear to be well-suited for use under conditions similar tomore » those encountered in EOR operations. Additionally, we disclose the synthesis and characterization of a well-defined set of polyacrylamide (PAM) homopolymers that vary by MW. The MW of the PAM samples is controlled by addition of sodium formate to the polymerization medium as a conventional chain transfer agent. Data derived from polymer characterization is used to determine the kinetic parameter C{sub CT}, the chain transfer constant to sodium formate under the given polymerization conditions. The PAM homopolymer series will be employed in future set of experiments designed to test a simplified intrinsic viscosity equation. The flow resistance of a polymer solution through a porous medium is controlled by the polymer's hydrodynamic volume, which is strongly related to it's intrinsic viscosity. However, the hydrodynamic volume of a polymer molecule in an aqueous solution varies with fluid temperature, solvent composition, and polymer structure. This report on the theory of polymer solubility accentuates the importance of developing polymer solutions that increase in intrinsic viscosity when fluid temperatures are elevated above room conditions. The intrinsic viscosity response to temperature and molecular weight variations of three polymer solutions verified the modeling capability of a simplified intrinsic viscosity equation. These results imply that the simplified intrinsic viscosity equation is adequate in modeling polymer coil size response to solvent composition, temperature and polymer molecular weight. The equation can be used to direct efforts to produce superior polymers for mobility control during flooding of reservoirs at elevated temperatures.« less

Static and dynamic investigations of poly(aspartic acid) and Pluronic F127 complex prepared by self-assembling in aqueous solution

NASA Astrophysics Data System (ADS)

Nita, Loredana E.; Chiriac, Aurica P.; Bercea, Maria; Nistor, Manuela T.

2015-12-01

The present investigation is focused on evaluation of self-assembling ability in aqueous solutions of two water soluble polymers: poly(aspartic acid) (PAS) and Pluronic F127 (PL). The intermolecular complexes, realized between polyacid and neutral copolymer surfactant in different ratios, have been studied by combining various characterization techniques as rheology, DLS, spectroscopy, microscopy, chemical imaging, and zeta potential determination, measurements performed in static and/or dynamic conditions. In static conditions, when the equilibrium state between PAS/PL polymeric pair was reached, and depending on the polymers mixture composition, and of experimental rheological conditions, positive or negative deviations from the additive rule are registered. Conformational changes of the macromolecular chains and correspondingly physical interactions are generated between PL and PAS for self-assembly and the formation of interpolymer complex as suprastructure with micellar configuration. The phenomenon was better evidenced in case of 1/1 wt ratio between the two polymers. In dynamic conditions of determination, during ;in situ; evaluation of the hydrodynamic diameter, zeta potential and conductivity, when the equilibrium state is not reached and as result either the intermolecular bonds are not achieved, the self-assembling process is not so obvious evidenced.

Dynamics of micelle-nanoparticle systems undergoing shear. A coarse-grained molecular dynamics approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rolfe, Bryan A.; Chun, Jaehun; Joo, Yong L.

2013-09-05

Recent experimental work has shown that polymeric micelles can template nanoparticles via interstitial sites in shear-ordered micelle solutions. In the current study, we report simulation results based on a coarse-grained molecular dynamics (CGMD) model of a solvent/polymer/nanoparticle system. Our results demonstrate the importance of polymer concentration and the micelle corona length in 2D shear-ordering of neat block copolymer solutions. Although our results do not show strong 3D ordering during shear, we find that cessation of shear allows the system to relax into a 3D configuration of greater order than without shear. It is further shown that this post-shear relaxation ismore » strongly dependent on the length of the micelle corona. For the first time, we demonstrate the presence and importance of a flow disturbance surrounding micelles in simple shear flow at moderate Péclet numbers. This disturbance is similar to what is observed around simulated star polymers and ellipsoids. The extent of the flow disturbance increases as expected with a longer micelle corona length. It is further suggested that without proper consideration of these dynamics, a stable nanoparticle configuration would be difficult to obtain.« less

Unified force-level theory of multiscale transient localization and emergent elasticity in polymer solutions and melts

NASA Astrophysics Data System (ADS)

Dell, Zachary E.; Schweizer, Kenneth S.

A unified, microscopic, theoretical understanding of polymer dynamics in concentrated liquids from segmental to macromolecular scales remains an open problem. We have formulated a statistical mechanical theory for this problem that explicitly accounts for intra- and inter-molecular forces at the Kuhn segment level. The theory is self-consistently closed at the level of a matrix of dynamical second moments of a tagged chain. Two distinct regimes of isotropic transient localization are predicted. In semidilute solutions, weak localization is predicted on a mesoscopic length scale between segment and chain scales which is a power law function of the invariant packing length. This is consistent with the breakdown of Rouse dynamics and the emergence of entanglements. The chain structural correlations in the dynamically arrested state are also computed. In dense melts, strong localization is predicted on a scale much smaller than the segment size which is weakly dependent on chain connectivity and signals the onset of glassy dynamics. Predictions of the dynamic plateau shear modulus are consistent with the known features of emergent rubbery and glassy elasticity. Generalizations to treat the effects of chemical crosslinking and physical bond formation in polymer gels are possible.

Carbon Nanotube Dispersion in Solvents and Polymer Solutions: Mechanisms, Assembly, and Preferences.

PubMed

Pramanik, Chandrani; Gissinger, Jacob R; Kumar, Satish; Heinz, Hendrik

2017-12-26

Debundling and dispersion of carbon nanotubes (CNTs) in polymer solutions play a major role in the preparation of carbon nanofibers due to early effects on interfacial ordering and mechanical properties. A roadblock toward ultrastrong fibers is the difficulty to achieve homogeneous dispersions of CNTs in polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) precursor solutions in solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF). In this contribution, molecular dynamics simulations with accurate interatomic potentials for graphitic materials that include virtual π electrons are reported to analyze the interaction of pristine single wall CNTs with the solvents and polymer solutions at 25 °C. The results explain the barriers toward dispersion of SWCNTs and quantify CNT-solvent, polymer-solvent, as well as CNT-polymer interactions in atomic detail. Debundling of CNTs is overall endothermic and unfavorable with dispersion energies of +20 to +30 mJ/m 2 in the pure solvents, + 20 to +40 mJ/m 2 in PAN solutions, and +20 to +60 mJ/m 2 in PMMA solutions. Differences arise due to molecular geometry, polar, van der Waals, and CH-π interactions. Among the pure solvents, DMF restricts CNT dispersion less due to the planar geometry and stronger van der Waals interactions. PAN and PMMA interact favorably with the pure solvents with dissolution energies of -0.7 to -1.1 kcal per mole monomer and -1.5 to -2.2 kcal per mole monomer, respectively. Adsorption of PMMA onto CNTs is stronger than that of PAN in all solvents as the molecular geometry enables more van der Waals contacts between alkyl groups and the CNT surface. Polar side groups in both polymers prefer interactions with the polar solvents. Higher polymer concentrations in solution lead to polymer aggregation via alkyl groups and reduce adsorption onto CNTs. PAN and PMMA solutions in DMSO and dilute solutions in DMF support CNT dispersion more than other combinations whereby the polymers significantly adsorb onto CNTs in DMSO solution. The observations by molecular simulations are consistent with available experimental data and solubility parameters and aid in the design of carbon nanofibers. The methods can be applied to other multiphase graphitic materials.

USE OF POLYMERS TO RECOVER VISCOUS OIL FROM UNCONVENTIONAL RESERVOIRS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randall Seright

2011-09-30

This final technical progress report summarizes work performed the project, 'Use of Polymers to Recover Viscous Oil from Unconventional Reservoirs.' The objective of this three-year research project was to develop methods using water soluble polymers to recover viscous oil from unconventional reservoirs (i.e., on Alaska's North Slope). The project had three technical tasks. First, limits were re-examined and redefined for where polymer flooding technology can be applied with respect to unfavorable displacements. Second, we tested existing and new polymers for effective polymer flooding of viscous oil, and we tested newly proposed mechanisms for oil displacement by polymer solutions. Third, wemore » examined novel methods of using polymer gels to improve sweep efficiency during recovery of unconventional viscous oil. This report details work performed during the project. First, using fractional flow calculations, we examined the potential of polymer flooding for recovering viscous oils when the polymer is able to reduce the residual oil saturation to a value less than that of a waterflood. Second, we extensively investigated the rheology in porous media for a new hydrophobic associative polymer. Third, using simulation and analytical studies, we compared oil recovery efficiency for polymer flooding versus in-depth profile modification (i.e., 'Bright Water') as a function of (1) permeability contrast, (2) relative zone thickness, (3) oil viscosity, (4) polymer solution viscosity, (5) polymer or blocking-agent bank size, and (6) relative costs for polymer versus blocking agent. Fourth, we experimentally established how much polymer flooding can reduce the residual oil saturation in an oil-wet core that is saturated with viscous North Slope crude. Finally, an experimental study compared mechanical degradation of an associative polymer with that of a partially hydrolyzed polyacrylamide. Detailed results from the first two years of the project may be found in our first and second annual reports. Our latest research results, along with detailed documentation of our past work, can be found on our web site at http://baervan.nmt.edu/randy/. As an overall summary of important findings for the project, polymer flooding has tremendous potential for enhanced recovery of viscous oil. Fear of substantial injectivity reduction was a primary hurdle that limited application of polymer flooding. However, that concern is largely mitigated by (1) use of horizontal wells and (2) judicious injection above the formation parting pressure. Field cases now exist where 200-300-cp polymer solutions are injected without significant reductions in injectivity. Concern about costs associated with injection of viscous polymer solutions was a second major hurdle. However, that concern is reduced substantially by realization that polymer viscosity increases approximately with the square of polymer concentration. Viscosity can be doubled with only a 40% increase in polymer concentration. Up to a readily definable point, increases in viscosity of the injected polymer solution are directly related to increases in sweep efficiency and oil recovery. Previously published simulation results - suggesting that shear-thinning polymer solutions were detrimental to sweep efficiency - were shown to be unfounded (both theoretically and experimentally).« less

Sorption of Ochratoxin A from aqueous solutions using beta-cyclodextrin-polyurethane polymer

USDA-ARS?s Scientific Manuscript database

The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions, including wine, was examined by batch rebinding assays and equilibrium sorption isotherms. The results were fit to two parameter models. Freundlich analysis of the sorption isotherm indicates the polyme...

Semipermeable polymers and method for producing same

DOEpatents

Buschmann, Wayne E [Boulder, CO

2012-04-03

A polyamide membrane comprising reaction product of an anhydrous solution comprising an anhydrous solvent, at least one polyfunctional secondary amine and a pre-polymer deposition catalyst; and an anhydrous, organic solvent solution comprising a polyfunctional aromatic amine-reactive reactant comprising one ring. A composite semipermeable membrane comprising the polyamide membrane on a porous support. A method of making a composite semipermeable membrane by coating a porous support with an anhydrous solution comprising an anhydrous solvent, a polyfunctional secondary amine and a pre-polymer deposition catalyst, to form an activated pre-polymer layer on the porous support and contacting the activated pre-polymer layer with an anhydrous, organic solvent solution comprising a polyfunctional amine-reactive reactant to interfacially condense the amine-reactive reactant with the polyfunctional secondary amine, thereby forming a cross-linked, interfacial polyamide layer on the porous support. A method of impregnating a composite semipermeable membrane with nanoparticles selected from heavy metals and/or oxides of heavy metals.

Preparation of transition metal nanoparticles and surfaces modified with (CO)polymers synthesized by RAFT

DOEpatents

McCormick, III., Charles L.; Lowe, Andrew B.; Sumerlin, Brent S.

2006-11-21

A new, facile, general one-phase method of generating thio-functionalized transition metal nanoparticles and surfaces modified by (co)polymers synthesized by the RAFT method is described. The method includes the stops of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a colloidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as functionalization with a variety of different chemical groups, expanding their utility and application.

Preparation of transition metal nanoparticles and surfaces modified with (co)polymers synthesized by RAFT

DOEpatents

McCormick, III, Charles L.; Lowe, Andrew B [Hattiesburg, MS; Sumerlin, Brent S [Pittsburgh, PA

2011-12-27

A new, facile, general one-phase method of generating thiol-functionalized transition metal nanoparticles and surfaces modified by (co)polymers synthesized by the RAFT method is described. The method includes the steps of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a colloidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as functionalization with a variety of different chemical groups, expanding their utility and application.

Structural relaxation processes in polyethylene glycol/CCl4 solutions by Brillouin scattering.

PubMed

Pochylski, M; Aliotta, F; Błaszczak, Z; Gapiński, J

2005-03-10

We present results of a Brillouin scattering experiment on solutions of poly(ethylene glycol) of mean molecular mass 600 g/mol (PEG600) in CCl4. The relaxation process detected has been assigned to conformational rearrangements of the polymeric chains, triggered by reorientation of the side groups. The concentration dependencies of the hypersound velocity and normalized absorption are compared against the indications from several models proposed in the literature. The concentration evolution of the system is described in terms of two distinct regimes. At high polymer content, the system is dominated by the structure of the dense polymer, where polymer-polymer interactions, together with excluded volume effects, induce the existence of a preferred local arrangement resulting in a narrow distribution of the relaxation times, with the average value of the relaxation time following a simple Arrhenius temperature dependence. As the concentration decreases, the original structure of the hydrogen bonded polymer network is destroyed, and a number of different local configuration coexist, giving rise to a wider distribution of relaxation times or to a multiple relaxation. At low concentrations, the experimental data are well fitted assuming a Vogel-Fulker-Tammon behavior for the average relaxation time. In addition, the observed deviation from the ideal behavior for the refractive index and the density suggests that CCl4 does not behave as an inert solvent, and due to polarization effects, it can develop local hetero-associated structures via electrostatic interaction with the O-H end groups of the polymeric chains. The hypothesis has been successfully tested by fitting the concentration behavior of the hypersonic velocity to a recent three-component model, suitable to describe the concentration dependence of sound velocity in moderately interacting fluids. The indication of the model furnishes a very high value for the association constant of the PEG600, confirming the literature indication that, in polymeric systems capable of developing long liner aggregates via hydrogen bonding interaction, the Brillouin probe is insensitive to the true length of the polymeric chains. The Brillouin scattering experiment just sees an effective hydrogen bonded aggregate that is huge relative to the length of the single polymeric chain and becomes sensitive only to the density fluctuations of the local segmental motions.

Polymer Brushes under High Load

PubMed Central

Balko, Suzanne M.; Kreer, Torsten; Costanzo, Philip J.; Patten, Tim E.; Johner, Albert; Kuhl, Tonya L.; Marques, Carlos M.

2013-01-01

Polymer coatings are frequently used to provide repulsive forces between surfaces in solution. After 25 years of design and study, a quantitative model to explain and predict repulsion under strong compression is still lacking. Here, we combine experiments, simulations, and theory to study polymer coatings under high loads and demonstrate a validated model for the repulsive forces, proposing that this universal behavior can be predicted from the polymer solution properties. PMID:23516470

Enhancing performing characteristics of organic semiconducting films by improved solution processing

DOEpatents

Bazan, Guillermo C; Moses, Daniel; Peet, Jeffrey; Heeger, Alan J

2014-05-13

Improved processing methods for enhanced properties of conjugated polymer films are disclosed, as well as the enhanced conjugated polymer films produced thereby. Addition of low molecular weight alkyl-containing molecules to solutions used to form conjugated polymer films leads to improved photoconductivity and improvements in other electronic properties. The enhanced conjugated polymer films can be used in a variety of electronic devices, such as solar cells and photodiodes.

Miscibility of poly(lactic acid) and poly(ethylene oxide) solvent polymer blends and nanofibers made by solution blow spinning

USDA-ARS?s Scientific Manuscript database

The miscibility of blends of poly(lactic acid) (PLA) and poly(ethylene oxide) (PEO) was studied in polymer solutions by dilute solution viscometry and in solution blow spun nanofibers by microscopy (SEM, TEM) and by thermal and spectral analysis. Three blends of PLA and PEO were solution blended in...

The dynamics of solvation dictates the conformation of polyethylene oxide in aqueous, isobutyric acid and binary solutions.

PubMed

Dahal, Udaya R; Dormidontova, Elena E

2017-04-12

Polymers hydrogen-bonding with solvent represent an important broad class of polymers, properties of which depend on solvation. Using atomistic molecular dynamics simulations with the OPLS/AA force field we investigate the effect of hydrogen bonding on PEO conformation and chain mobility by comparing its behavior in isobutyric acid and aqueous solutions. In agreement with experimental data, we found that in isobutyric acid PEO forms a rather rigid extended helical structure, while in water it assumes a highly flexible coil conformation. We show that the difference in PEO conformation and flexibility is the result of the hydrogen bond stability and overall solvent dynamics near PEO. Isobutyric acid forms up to one hydrogen bond per repeat unit of PEO and interacts with PEO for a prolonged period of time, thereby stabilizing the helical structure of the polymer and reducing its segmental mobility. In contrast, water forms on average 1.2 hydrogen bonds per repeat unit of PEO (with 60% of water forming a single hydrogen bond and 40% of water forming two hydrogen bonds) and resides near PEO for a noticeably shorter time than isobutyric acid, leading to the well-documented high segmental mobility of PEO in water. We also analyze PEO conformation, hydrogen bonding and segmental mobility in binary water/isobutyric acid solutions and find that in the phase separated region PEO resides in the isobutyric-rich phase forming about 25% of its hydrogen bonds with isobutyric acid and 75% with water. We show that the dynamics of solvation affects the equilibrium properties of macromolecules, such as conformation, and by mixing of hydrogen bond-donating solvents one can significantly alter both polymer conformation and its local dynamics.

Investigation of the required length for fully developed pipe flow with drag-reducing polymer solutions

NASA Astrophysics Data System (ADS)

Farsiani, Yasaman; Elbing, Brian

2015-11-01

Adding trace amounts of long chain polymers into a liquid flow is known to reduce skin friction drag by up to 80%. While polymer drag reduction (PDR) has been successfully implemented in internal flows, diffusion and degradation have limited its external flow applications. A weakness in many previous PDR studies is that there was no characterization of the polymer being injected into the turbulent boundary layer, which can be accomplished by testing a sample in a pressure-drop tube. An implicit assumption in polymer characterization is that the flow is fully developed at the differential pressure measurement. While available data in the literature shows that the entry length to achieve fully developed flow increases with polymeric solutions, it is unclear how long is required to achieve fully developed flow for non-Newtonian turbulent flows. In the present study, the pressure-drop is measured across a 1.05 meter length section of a 1.04 cm inner diameter pipe. Differential pressure is measured with a pressure transducer for different entry lengths, flow and polymer solution properties. This presentation will present preliminary data on the required entrance length as well as characterization of polymer solution an estimate of the mean molecular weight.

Synthesis, Characterisation, and Evaluation of a Cross-Linked Disulphide Amide-Anhydride-Containing Polymer Based on Cysteine for Colonic Drug Delivery

PubMed Central

Lim, Vuanghao; Peh, Kok Khiang; Sahudin, Shariza

2013-01-01

The use of disulphide polymers, a low redox potential responsive delivery, is one strategy for targeting drugs to the colon so that they are specifically released there. The objective of this study was to synthesise a new cross-linked disulphide-containing polymer based on the amino acid cysteine as a colon drug delivery system and to evaluate the efficiency of the polymers for colon targeted drug delivery under the condition of a low redox potential. The disulphide cross-linked polymers were synthesised via air oxidation of 1,2-ethanedithiol and 3-mercapto-N-2-(3-mercaptopropionamide)-3-mercapto propionic anhydride (trithiol monomers) using different ratio combinations. Four types of polymers were synthesised: P10, P11, P151, and P15. All compounds synthesised were characterised by NMR, IR, LC-MS, CHNS analysis, Raman spectrometry, SEM-EDX, and elemental mapping. The synthesised polymers were evaluated in chemical reduction studies that were performed in zinc/acetic acid solution. The suitability of each polymer for use in colon-targeted drug delivery was investigated in vitro using simulated conditions. Chemical reduction studies showed that all polymers were reduced after 0.5–1.0 h, but different polymers had different thiol concentrations. The bacterial degradation studies showed that the polymers were biodegraded in the anaerobic colonic bacterial medium. Degradation was most pronounced for polymer P15. This result complements the general consensus that biodegradability depends on the swellability of polymers in an aqueous environment. Overall, these results suggest that the cross-linked disulphide-containing polymers described herein could be used as coatings for drugs delivered to the colon. PMID:24351841

Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods

NASA Astrophysics Data System (ADS)

Yoon, Joonsung

The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and phthalic anhydride. A simple method to prepare composite surfaces that can change the wettability in response to the temperature change was proposed and evaluated. Composite surfaces prepared by nanoporous alumina templates filled with polymers showed surface morphology and wettability that depend on temperature. This effect is attributed to the significant difference in thermal conductivity and the thermal expansion coefficient between the alumina and the polymers. The reversibility in thermal response depends on the properties of the polymers.

Simulation of macromolecule self-assembly in solution: A multiscale approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavino, Alessio D., E-mail: alessiodomenico.lavino@studenti.polito.it; Barresi, Antonello A., E-mail: antonello.barresi@polito.it; Marchisio, Daniele L., E-mail: daniele.marchisio@polito.it

2015-12-17

One of the most common processes to produce polymer nanoparticles is to induce self-assembly by using the solvent-displacement method, in which the polymer is dissolved in a “good” solvent and the solution is then mixed with an “anti-solvent”. The polymer ability to self-assemble in solution is therefore determined by its structural and transport properties in solutions of the pure solvents and at the intermediate compositions. In this work, we focus on poly-ε-caprolactone (PCL) which is a biocompatible polymer that finds widespread application in the pharmaceutical and biomedical fields, performing simulation at three different scales using three different computational tools: fullmore » atomistic molecular dynamics (MD), population balance modeling (PBM) and computational fluid dynamics (CFD). Simulations consider PCL chains of different molecular weight in solution of pure acetone (good solvent), of pure water (anti-solvent) and their mixtures, and mixing at different rates and initial concentrations in a confined impinging jets mixer (CIJM). Our MD simulations reveal that the nano-structuring of one of the solvents in the mixture leads to an unexpected identical polymer structure irrespectively of the concentration of the two solvents. In particular, although in pure solvents the behavior of the polymer is, as expected, very different, at intermediate compositions, the PCL chain shows properties very similar to those found in pure acetone as a result of the clustering of the acetone molecules in the vicinity of the polymer chain. We derive an analytical expression to predict the polymer structural properties in solution at different solvent compositions and use it to formulate an aggregation kernel to describe the self-assembly in the CIJM via PBM and CFD. Simulations are eventually validated against experiments.« less

Low density microcellular foams

DOEpatents

Aubert, James H.; Clough, Roger L.; Curro, John G.; Quintana, Carlos A.; Russick, Edward M.; Shaw, Montgomery T.

1987-01-01

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the resultant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Means for subjecting such a solvent to one-dimensional cooling are also provided. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 .mu.m and a volume such that the foams have a length greater than 1 cm are provided.

Adsorption of surfactants and polymers at interfaces

NASA Astrophysics Data System (ADS)

Rojas, Orlando Jose

Surface tension and high-resolution laser light scattering experiments were used to investigate the adsorption of isomeric sugar-based surfactants at the air/liquid interface in terms of surfactant surface packing and rheology. Soluble monolayers of submicellar surfactant solutions exhibited a relatively viscous behavior. It was also proved that light scattering of high-frequency thermally-induced capillary waves can be utilized to study surfactant exchange between the surface and the bulk solution. Such analysis revealed the existence of a diffusional relaxation mechanism. A procedure based on XPS was developed for quantification, on an absolute basis, of polymer adsorption on mica and Langmuir-Blodgett cellulose films. The adsorption of cationic polyelectrolytes on negatively-charged solid surfaces was highly dependent on the polymer ionicity. It was found that the adsorption process is driven by electrostatic mechanisms. Charge overcompensation (or charge reversal) of mica occurred after adsorption of polyelectrolytes of ca. 50% charge density, or higher. It was demonstrated that low-charge-density polyelectrolytes adsorb on solid surfaces with an extended configuration dominated by loops and tails. In this case the extent of adsorption is limited by steric constraints. The conformation of the polyelectrolyte in the adsorbed layer is dramatically affected by the presence of salts or surfactants in aqueous solution. The phenomena which occur upon increasing the ionic strength are consistent with the screening of the electrostatic attraction between polyelectrolyte segments and solid surface. This situation leads to polyelectrolyte desorption accompanied by both an increase in the layer thickness and the range of the steric force. Adsorbed polyelectrolytes and oppositely charged surfactants readily associate at the solid/liquid interface. Such association induces polyelectrolyte desorption at a surfactant concentration which depends on the polyelectrolyte charge density. In practical systems the adsorption phenomena were found to be far more complex. Electrostatic and hydrogen bonding interactions play a major role in the adsorption of cationic polyelectrolytes on cellulosic substrates. Cationic and underivatized guar gum macromolecules form complexes with fines and dissolved and colloidal carbohydrates which are then retained on the cellulose fibers. The extent of the adsorption and association depends on the charge and nature of all the components present in pulp suspensions.

21 CFR 177.1660 - Poly (tetramethylene terephthalate).

Code of Federal Regulations, 2010 CFR

2010-04-01

... terephthalate). Poly(tetramethylene terephthalate) (poly (oxytetramethyleneoxyter-ephthaloyl)) [Chemical...) Specifications. (1) Inherent viscosity of a 0.50 percent solution of the polymer in phenol/tetrachloroethane (60... solution to that of the solvent and c=polymer concentration of the test solution in grams per 100...

The rheology and phase separation kinetics of mixed-matrix membrane dopes

NASA Astrophysics Data System (ADS)

Olanrewaju, Kayode Olaseni

Mixed-matrix hollow fiber membranes are being developed to offer more efficient gas separations applications than what the current technologies allow. Mixed-matrix membranes (MMMs) are membranes in which molecular sieves incorporated in a polymer matrix enhance separation of gas mixtures based on the molecular size difference and/or adsorption properties of the component gases in the molecular sieve. The major challenges encountered in the efficient development of MMMs are associated with some of the paradigm shifts involved in their processing, as compared to pure polymer membranes. For instance, mixed-matrix hollow fiber membranes are prepared by a dry-wet jet spinning method. Efficient large scale processing of hollow fibers by this method requires knowledge of two key process variables: the rheology and kinetics of phase separation of the MMM dopes. Predicting the rheological properties of MMM dopes is not trivial; the presence of particles significantly affects neat polymer membrane dopes. Therefore, the need exists to characterize and develop predictive capabilities for the rheology of MMM dopes. Furthermore, the kinetics of phase separation of polymer solutions is not well understood. In the case of MMM dopes, the kinetics of phase separation are further complicated by the presence of porous particles in a polymer solution. Thus, studies on the phase separation kinetics of polymer solutions and suspensions of zeolite particles in polymer solutions are essential. Therefore, this research thesis aims to study the rheology and phase separation kinetics of mixed-matrix membrane dopes. In our research efforts to develop predictive models for the shear rheology of suspensions of zeolite particles in polymer solutions, it was found that MFI zeolite suspensions have relative viscosities that dramatically exceed the Krieger-Dougherty predictions for hard sphere suspensions. Our investigations showed that the major origin of this discrepancy is the selective absorption of solvent molecules from the suspending polymer solution into the zeolite pores. Consequently, both the viscosity of the polymer solution and the particle contribution to the suspension viscosity are greatly increased. A predictive model for the viscosity of porous zeolite suspensions incorporating a solvent absorption parameter, alpha, into the Krieger-Dougherty model was developed. We experimentally determined the solvent absorption parameter and our results are in good agreement with the theoretical pore volume of MFI particles. In addition, fundamental studies were conducted with spherical nonporous silica suspensions to elucidate the role of colloidal and hydrodynamic forces on the rheology of mixed-matrix membrane dopes. Also in this thesis, details of a novel microfluidic device for measuring the phase separation kinetics of membrane dopes are presented. We have used this device to quantify the phase separation kinetics (PSK) of polymer solutions and MMM dopes upon contact with an array of relevant nonsolvent. For the polymer solution, we found that PSK is governed by the micro-rheological and thermodynamic properties of the polymer solution and nonsolvent. For the MMM dopes, we found that the PSK may increase with increase in particles surface area due to surface diffusion enhancement. In addition, it was found that the dispersed particles alter the thermodynamic properties of the dope based on the hydrophilicity and porosity of the particle.

Flagellated bacterial motility in polymer solutions

PubMed Central

Martinez, Vincent A.; Schwarz-Linek, Jana; Reufer, Mathias; Wilson, Laurence G.; Morozov, Alexander N.; Poon, Wilson C. K.

2014-01-01

It is widely believed that the swimming speed, v, of many flagellated bacteria is a nonmonotonic function of the concentration, c, of high-molecular-weight linear polymers in aqueous solution, showing peaked v(c) curves. Pores in the polymer solution were suggested as the explanation. Quantifying this picture led to a theory that predicted peaked v(c) curves. Using high-throughput methods for characterizing motility, we measured v and the angular frequency of cell body rotation, Ω, of motile Escherichia coli as a function of polymer concentration in polyvinylpyrrolidone (PVP) and Ficoll solutions of different molecular weights. We find that nonmonotonic v(c) curves are typically due to low-molecular-weight impurities. After purification by dialysis, the measured v(c) and Ω(c) relations for all but the highest-molecular-weight PVP can be described in detail by Newtonian hydrodynamics. There is clear evidence for non-Newtonian effects in the highest-molecular-weight PVP solution. Calculations suggest that this is due to the fast-rotating flagella seeing a lower viscosity than the cell body, so that flagella can be seen as nano-rheometers for probing the non-Newtonian behavior of high polymer solutions on a molecular scale. PMID:25468981

Structure and Dynamics of Interacting Nanoparticles in Semidilute Polymer Solutions

DOE PAGES

Pollng-Skutvik, Ryan; Mongcopa, Katrina Irene S.; Faraone, Antonio; ...

2016-08-17

We investigate the structure and dynamics of silica nanoparticles and polymer chains in semidilute solutions of high molecular weight polystyrene in 2-butanone to determine the effect of long-range interparticle interactions on the coupling between particle and polymer dynamics. Particles at concentrations of 1–10 wt % are well dispersed in the semidilute polymer solutions and exhibit long-range electrostatic repulsions between particles. Because the particles are comparably sized to the radius of gyration of the polymer, the particle dynamics is predicted to couple to that of the polymer. We verify that the polymer structure and dynamics are not significantly affected by themore » particles, indicating that the particle–polymer coupling does not change with increasing particle loading. We find that the coupling between the dynamics of comparably sized particles and polymer results in subdiffusive particle dynamics, as expected. Over the interparticle distance, however, the particle dynamics is hindered and not fully described by the relaxation of the surrounding polymer chains. Instead, the particle dynamics is inversely related to the structure factor, suggesting that physical particle–polymer coupling on short length scales and interparticle interactions on long length scales both present energetic barriers to particle motion that lead to subdiffusive dynamics and de Gennes narrowing, respectively.« less

Vitrification of polymer solutions as a function of solvent quality, analyzed via vapor pressures

NASA Astrophysics Data System (ADS)

Bercea, Maria; Wolf, Bernhard A.

2006-05-01

Vapor pressures (headspace sampling in combination with gas chromatography) and glass transition temperatures [differential scanning calorimetry (DSC)] have been measured for solutions of polystyrene (PS) in either toluene (TL) (10-70°C) or cyclohexane (CH) (32-60°C) from moderately concentrated solutions up to the pure polymer. As long as the mixtures are liquid, the vapor pressure of TL (good solvent) is considerably lower than that of CH (theta solvent) under other identical conditions. These differences vanish upon the vitrification of the solutions. For TL the isothermal liquid-solid transition induced by an increase of polymer concentration takes place within a finite composition interval at constant vapor pressure; with CH this phenomenon is either absent or too insignificant to be detected. For PS solutions in TL the DSC traces look as usual, whereas these curves may become bimodal for solutions in CH. The implications of the vitrification of the polymer solutions for the determination of Flory-Huggins interaction parameters from vapor pressure data are discussed. A comparison of the results for TL/PS with recently published data on the same system demonstrates that the experimental method employed for the determination of vapor pressures plays an important role at high polymer concentrations and low temperatures.

Nanotube/Quantum Dot-Polymer Solar Cells

NASA Technical Reports Server (NTRS)

Bailey, Sheila G.; Raffaelle, Ryne P.; Landi, Brian J.; Castro, Stephanie L.

2005-01-01

Single wall carbon nanotubes used or this study were synthesized using the pulse laser vaporization technique. The as-produced SWNTs were collected from the condensed region on the quartz tube outside the furnace and purified by modification of the previously reported procedure. Preparation of the SWNT-P3OT composite solutions was performed using a series of mixing and sonication steps as previously demonstrated for other SWNT-polymer systems. Device fabrication involved the use of commercially-obtained, high quality (i.e., less than 10 W/sq.) ITO-coated polyethylene terapthalate (PET) substrates. Initially, an intrinsic layer of pristine P3OT is spray deposited (approx. 1-2 mL of the 15 mg/mL solution) onto the masked, 1 sq in. active area of the substrate. This is followed with spray deposition of the SWNT-P3OT composite solutions at similar volumes. As seen completion of the solar cell occurs when aluminum contacts (typical thicknesses of l000A) are applied to the IT0 and SWNT-P3OT composite film layers. The homogeneous distribution of SWNTs in a polymer matrix is dependent upon the ability of the polymer chain to associate with the SWNT superstructure. Stable composite dispersions of 0.1 % and 1.0% w/w SWNTs in P3OT were produced and analyzed in this study. Optical spectroscopy was conducted to observe the SWNT doping level effects on the absorption properties and infer potential electronic interactions between dopant and polymer. Shown is an overlay of these spectra where the pristine P3OT shows strong optical absorption at energies less than 2 eV. As expected, variation in absorption properties for the SWNT-P3OT composites is observed as the doping level increases. Through modification of the SWNT doping level in the polymer, it is possible to alter the absorption pattern of these composite materials. In fact, at these relatively low doping levels, the P3OT shows a significant enhancement in absorption through the near-IR and visible regions. The gray curve for purified SWNTs is offset from the other three for clarity, but indicates the typical complex pattern observed for this spectral range.

Responsive Copolymers for Enhanced Petroleum Recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCormick, C.; Hester, R.

The objectives of this work was to: synthesize responsive copolymer systems; characterize molecular structure and solution behavior; measure rheological properties of aqueous fluids in fixed geometry flow profiles; and to tailor final polymer compositions for in situ rheology control under simulated conditions. This report focuses on the synthesis and characterization of novel stimuli responsive copolymers, the investigation of dilute polymer solutions in extensional flow and the design of a rheometer capable of measuring very dilute aqueous polymer solutions at low torque.

Structural modifications of polymethacrylates: impact on thermal behavior and release characteristics of glassy solid solutions.

PubMed

Claeys, Bart; De Coen, Ruben; De Geest, Bruno G; de la Rosa, Victor R; Hoogenboom, Richard; Carleer, Robert; Adriaensens, Peter; Remon, Jean Paul; Vervaet, Chris

2013-11-01

Polymethacrylates such as Eudragit® polymers are well established as drug delivery matrix. Here, we synthesize several Eudragit E PO (n-butyl-, dimethylaminoethyl-, methyl-methacrylate-terpolymer) analogues via free radical polymerization. These polymers are processed via hot melt extrusion, followed by injection molding and evaluated as carriers to produce immediate release solid solution tablets. Three chemical modifications increased the glass transition temperature of the polymer: (a) substitution of n-butyl by t-butyl groups, (b) reduction of the dimethylaminoethyl methacrylate (DMAEMA) content, and (c) incorporation of a bulky isobornyl repeating unit. These structural modifications revealed the possibility to increase the mechanical stability of the tablets via altering the polymer Tg without influencing the drug release characteristics and glassy solid solution forming properties. The presence of DMAEMA units proved to be crucial with respect to API/polymer interaction (essential in creating glassy solid solutions) and drug release characteristics. Moreover, these chemical modifications accentuate the need for a more rational design of (methacrylate) polymer matrix excipients for drug formulation via hot melt extrusion and injection molding. Copyright © 2013 Elsevier B.V. All rights reserved.

How the World Changes By Going from One- to Two-Dimensional Polymers in Solution.

PubMed

Schlüter, A Dieter; Payamyar, Payam; Öttinger, Hans Christian

2016-10-01

Scaling behavior of one-dimensional (1D) and two-dimensional (2D) polymers in dilute solution is discussed with the goal of stimulating experimental work by chemists, physicists, and material scientists in the emerging field of 2D polymers. The arguments are based on renormalization-group theory, which is explained for a general audience. Many ideas and methods successfully applied to 1D polymers are found not to work if one goes to 2D polymers. The role of the various states exhibiting universal behavior is turned upside down. It is expected that solubility will be a serious challenge for 2D polymers. Therefore, given the crucial importance of solutions in characterization and processing, synthetic concepts are proposed that allow the local bending rigidity and the molar mass to be tuned and the long-range interactions to be engineered, all with the goal of preventing the polymer from falling into flat or compact states. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The local phase transitions of the solvent in the neighborhood of a solvophobic polymer at high pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budkov, Yu. A., E-mail: urabudkov@rambler.ru; National Research University Higher School of Economics, Moscow; Department of Chemistry, Lomonosov Moscow State University, Moscow

2014-11-28

We investigate local phase transitions of the solvent in the neighborhood of a solvophobic polymer chain which is induced by a change of the polymer-solvent repulsion and the solvent pressure in the bulk solution. We describe the polymer in solution by the Edwards model, where the conditional partition function of the polymer chain at a fixed radius of gyration is described by a mean-field theory. The contributions of the polymer-solvent and the solvent-solvent interactions to the total free energy are described within the mean-field approximation. We obtain the total free energy of the solution as a function of the radiusmore » of gyration and the average solvent number density within the gyration volume. The resulting system of coupled equations is solved varying the polymer-solvent repulsion strength at high solvent pressure in the bulk. We show that the coil-globule (globule-coil) transition occurs accompanied by a local solvent evaporation (condensation) within the gyration volume.« less

Metallization of electronic insulators

DOEpatents

Gottesfeld, Shimshon; Uribe, Francisco A.

1994-01-01

An electroplated element is formed to include an insulating substrate, a conducting polymer polymerized in situ on the substrate, and a metal layer deposited on the conducting polymer. In one application a circuit board is formed by polymerizing pyrrole on an epoxy-fiberglass substrate in a single step process and then electrodepositing a metal over the resulting polypyrrole polymer. No chemical deposition of the metal is required prior to electroplating and the resulting layer of substrate-polymer-metal has excellent adhesion characteristics. The metal deposition is surprisingly smooth and uniform over the relatively high resistance film of polypyrrole. A continuous manufacturing process is obtained by filtering the solution between successive substrates to remove polymer formed in the solution, by maintaining the solution oxidizing potential within selected limits, and by adding a strong oxidant, such as KMnO.sub.4 at periodic intervals to maintain a low sheet resistivity in the resulting conducting polymer film.

Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer

NASA Technical Reports Server (NTRS)

Rembaum, A.; Wallace, C. J. (Inventor)

1978-01-01

An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

APPLICATION OF VARIOUS POLYMERS AND POLYMERS BASED TECHNIQUES USED TO IMPROVE SOLUBILITY OF POORLY WATER SOLUBLE DRUGS: A REVIEW.

PubMed

Muhammad Sarfraz, Rai; Bashir, Sajid; Mahmood, Asif; Ahsan, Haseeb; Riaz, Humayun; Raza, Hina; Rashid, Zermina; Atif Raza, Syed; Asad Abrar, Muhammad; Abbas, Khawar; Yasmeen, Tahira

2017-03-01

Solubility is concerned with solute and solvent to form a homogenous mixture. If solubility of a drug is low, then usually it is difficult to achieve desired therapeutic level of drug. Most of the newly developed entities have solubility problems and encounter difficulty in dissolution. Basic aim of solubility enhancement is to achieve desired therapeutic'level of drug to produce required pharmacological response. Different techniques are being used to enhance the solubility of water insoluble drugs. These techniques include particle size reduction, spray drying, kneading method, solvent evaporation method, salt formation, microemulsions, co-solven- cy, hydrosols, prodrug approach, supercritical fluid process, hydrogel micro particles etc. Selection of solubility improving method depends on drug properties, site of absorption, and required dosage form characteristics. Variety of polymers are also used to enhance solubility of these drugs like polyethylene glycol 300, polyvinyl pyrrolidone, chitosan, β-cyclodextrins etc.

Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

NASA Astrophysics Data System (ADS)

Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

2013-01-01

In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

PubMed

Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

2007-09-25

The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

Optical and Thermo-optical Properties of Polyimide-Single-Walled Carbon Nanotube Films: Experimental Results and Empirical Equations

NASA Technical Reports Server (NTRS)

Smith, Joseph G., Jr.; Connell, John W.; Watson, Kent A.; Danehy, Paul M.

2005-01-01

The incorporation of single-walled carbon nanotubes (SWNTs) into the bulk of space environmentally durable polymers at loading levels greater than or equal to 0.05 wt % has afforded thin films with surface and volume resistivities sufficient for electrostatic charge mitigation. However, the optical transparency at 500 nm decreased and the thermo-optical properties (solar absorptivity and thermal emissivity) increased with increaed SWNT loading. These properties were also dependent on film thickness. The absorbance characteristics of the films as a function of SWNT loading and film thickness were measured and determined to follow the classical Beer-Lambert law. Based on these results, an empirical relationship was derived and molar absorptivities determined for both the SWNTs and polymer matrix to provide a predictive approximation of these properties. The molar absorptivity determined for SWNTs dispersed in the polymer was comparable to reported solution determined values for HiPco SWNTs.

Engineering polyelectrolyte multilayer structure at the nanometer length scale by tuning polymer solution conformation.

NASA Astrophysics Data System (ADS)

Boddohi, Soheil; Killingsworth, Christopher; Kipper, Matt

2008-03-01

Chitosan (a weak polycation) and heparin (a strong polyanion) are used to make polyelectrolyte multilayers (PEM). PEM thickness and composition are determined as a function of solution pH (4.6 to 5.8) and ionic strength (0.1 to 0.5 M). Over this range, increasing pH increases the PEM thickness; however, the sensitivity to changes in pH is a strong function of ionic strength. The PEM thickness data are correlated to the polymer conformation in solution. Polyelectrolyte conformation in solution is characterized by gel permeation chromatography (GPC). The highest sensitivity of PEM structure to pH is obtained at intermediate ionic strength. Different interactions govern the conformation and adsorption phenomena at low and high ionic strength, leading to reduced sensitivity to solution pH at extreme ionic strengths. The correspondence between PEM thickness and polymer solution conformation offers opportunities to tune polymer thin film structure at the nanometer length scale by controlling simple, reproducible processing conditions.

Lowering the Percolation Threshold of Conductive Composites Using Particulate Polymer Microstructure

NASA Astrophysics Data System (ADS)

Grunlan, Jaime; Gerberich, William; Francis, Lorraine

2000-03-01

In an effort to lower the percolation threshold of carbon black-filled polymer composites, various polymer microstructures were examined. Composites were prepared using polyvinyl acetate (PVAc) latex, PVAc water-dispersible powder and polyvinylpyrrolidone (PVP) solution as the matrix starting material. Composites prepared using the particulate microstructures showed a significantly lowered percolation threshold relative to an equivalently prepared composite using the PVP solution. The PVAc latex-based composites has a percolation threshold of 3 volthe PVP solution-based composite yielded a percolation threshold near 15 voloccupied by polymer particles, the particulate matrix-based composites create a segregated CB network at low filler concentration.

Rheological behavior of FM-9 solutions and correlation with flammability test results and interpretations. [fuel thickening additive

NASA Technical Reports Server (NTRS)

Peng, S. T. J.; Landel, R. F.

1983-01-01

The rheological behavior of progressively shear thickening FM-9 solutions, a time-dependent shear thickening material with characteristics of threshold behavior, is investigated as part of a study of the rheological properties of antimisting jet fuel. Flammability test results and test configurations from various sources are evaluated. A correlation is obtained between the rheological behavior and the flammability tests such that, for a given system, such as a fixed solvent system and the FM-9 polymer system, the flammability criterion can be applied to a wide range of concentrations and temperatures.

On The Molecular Mechanism Of Positive Novolac Resists

NASA Astrophysics Data System (ADS)

Huang, Jian-Ping; Kwei, T. K.; Reiser, Arnost

1989-08-01

A molecular mechanism for the dissolution of novolac is proposed, based on the idea of a critical degree of deprotonation as being the condition for the transfer of polymer into solution. The rate at which the critical deprotonation condition is achieved is controlled by the supply of developer into a thin penetration zone, and depends in particular on the rate of diffusion of the base cations which are the developer component with the lowest mobility. The penetration zone contains phenolate ions and ion-bound water, but it retains the structure of a rigid polymer membrane, as evidenced by the diffusion coefficient of cations in the pene;tration zone which is several orders of magnitude slower than in an open gel of the same material. When the critical degree of deprotonation is reached, the membrane structure unravels and all subsequent events, chain rearrangement and transfer into solution, occur rapidly. The supralinear dependence of dissolution rate on base concentration and the effect of the size of the base cation are plausibly interpreted by the model. The diffusion of developer components is assumed to occur preferentially via hydrophilic sites in the polymer matrix. These sites define a diffusion path which acts like a hydrophilic diffusion channel. Suitably designed hydrophobic molecules can block some of the channels and in this way alter the dissolution rate. They reduce in effect the diffusion crossect ion of the material. Hydrophilic additives, on the other hand, introduce additional channels into the system and promote dissolution. The concept of diffusion channels appears to provide a unified interpretation for a number of common observations.

Investigation of in situ gelling alginate formulations as a sustained release vehicle for co-precipitates of dextromethrophan and Eudragit S 100.

PubMed

El Maghraby, Gamal Mohamed; Elzayat, Ehab Mostafa; Alanazi, Fars Kaed

2014-03-01

Alginate vehicles are capable of forming a gel matrix in situ when they come into contact with gastric medium in the presence of calcium ions. However, the gel structure is pH dependent and can break after gastric emptying, leading to dose dumping. The aim of this work was to develop modified in situ gelling alginate formulations capable of sustaining dextromethorphan release throughout the gastrointestinal tract. Alginate solution (2 %, m/m) was used as a vehicle for the tested formulations. Solid matrix of the drug and Eudragit S 100 was prepared by dissolving the drug and polymer in acetone. The organic solvent was then evaporated and the deposited solid matrix was micronized, sieved and dispersed in alginate solution to obtain candidate formulations. The release behavior of dextromethorphan was monitored and evaluated in a medium simulating the gastric and intestinal pH. Drug-polymer compatibility and possible solid-state interactions suggested physical interaction through hydrogen bonding between the drug and the polymer. A significant decrease in the rate and extent of dextromethorphan release was observed with increasing Eudragit S 100 concentration in the prepared particles. Most formulations showed sustained release profiles similar to that of a commercial sustained-release liquid based on ion exchange resin. The release pattern indicated strict control of drug release both under gastric and intestinal conditions, suggesting the potential advantage of using a solid dispersion of drug-Eudragit S 100 to overcome the problem of dose dumping after the rupture of the pH dependent alginate gels.

Unbinding transition from fluid membranes with associated polymers.

PubMed

Benhamou, M; Kaidi, H

2013-10-01

We consider two neighboring fluid membranes that are associated with long flexible polymers (proteins or other macromolecules). We are interested in two physical systems consisting of i) two adjacent membranes with end-grafted (or adsorbed) polymers (system I), or ii) two membranes confining a polymer solution (system II). In addition to the pure interactions between membranes, the presence of polymers gives rise to new induced mediated interactions, which are repulsive, for system I, and attractive, for system II. In fact, repulsive induced interactions are caused by the excluded-volume forces between grafted polymers, while attractive ones, by entropy loss, due to free motion of polymers between membranes. The main goal is a quantitative study of the unbinding transition thermodynamics that is drastically affected by the associated polymers. For system I, the repulsive polymer-mediated force delays this transition that can happen at low temperature. To investigate the unbinding phenomenon, we first present an exact mathematical analysis of the total potential that is the sum of the primitive and induced potentials. This mathematical study enables us to classify the total interaction potentials, in terms of all parameters of the problem. Second, use is made of the standard variational method to calculate the first moments of the membrane separation. Special attention is paid to the determination of the unbinding temperature. In particular, we discuss its dependence on the extra parameters related to the associated polymers, which are the surface coverage and the polymer layer thickness on each membrane (for system I) or the polymer density and the gyration radius of coils (for system II). Third, we compute the disjoining pressure upon membrane separation. Finally, we emphasize that the presence of polymers may be a mechanism to delay or to accentuate the appearance of the unbinding transition between fluid membranes.

Polymers in the gut compress the colonic mucus hydrogel

PubMed Central

Datta, Sujit S.; Preska Steinberg, Asher

2016-01-01

Colonic mucus is a key biological hydrogel that protects the gut from infection and physical damage and mediates host–microbe interactions and drug delivery. However, little is known about how its structure is influenced by materials it comes into contact with regularly. For example, the gut abounds in polymers such as dietary fibers or administered therapeutics, yet whether such polymers interact with the mucus hydrogel, and if so, how, remains unclear. Although several biological processes have been identified as potential regulators of mucus structure, the polymeric composition of the gut environment has been ignored. Here, we demonstrate that gut polymers do in fact regulate mucus hydrogel structure, and that polymer–mucus interactions can be described using a thermodynamic model based on Flory–Huggins solution theory. We found that both dietary and therapeutic polymers dramatically compressed murine colonic mucus ex vivo and in vivo. This behavior depended strongly on both polymer concentration and molecular weight, in agreement with the predictions of our thermodynamic model. Moreover, exposure to polymer-rich luminal fluid from germ-free mice strongly compressed the mucus hydrogel, whereas exposure to luminal fluid from specific-pathogen-free mice—whose microbiota degrade gut polymers—did not; this suggests that gut microbes modulate mucus structure by degrading polymers. These findings highlight the role of mucus as a responsive biomaterial, and reveal a mechanism of mucus restructuring that must be integrated into the design and interpretation of studies involving therapeutic polymers, dietary fibers, and fiber-degrading gut microbes. PMID:27303035

Post-exercise ingestion of a unique, high molecular weight glucose polymer solution improves performance during a subsequent bout of cycling exercise.

PubMed

Stephens, Francis B; Roig, Marc; Armstrong, Gerald; Greenhaff, Paul L

2008-01-15

The aim of the present study was to determine the effect of post-exercise ingestion of a unique, high molecular weight glucose polymer solution, known to augment gastric emptying and post-exercise muscle glycogen re-synthesis, on performance during a subsequent bout of intense exercise. On three randomized visits, eight healthy men cycled to exhaustion at 73.0% (s = 1.3) maximal oxygen uptake (90 min, s = 15). Immediately after this, participants consumed a one-litre solution containing sugar-free flavoured water (control), 100 g of a low molecular weight glucose polymer or 100 g of a very high molecular weight glucose polymer, and rested on a bed for 2 h. After recovery, a 15-min time-trial was performed on a cycle ergometer, during which work output was determined. Post-exercise ingestion of the very high molecular weight glucose polymer solution resulted in faster and greater increases in blood glucose (P < 0.001) and serum insulin (P < 0.01) concentrations than the low molecular weight glucose polymer solution, and greater work output during the 15-min time-trial (164.1 kJ, s = 21.1) than both the sugar-free flavoured water (137.5 kJ, s = 24.2; P < 0.05) and the low molecular weight glucose polymer (149.4 kJ, s = 21.8; P < 0.05) solutions. These findings could be of practical importance for athletes wishing to optimize performance by facilitating rapid re-synthesis of the muscle glycogen store during recovery following prolonged sub-maximal exercise.

Selection of new Kynar-based electrolytes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Christie, Alasdair M.; Christie, Lynn; Vincent, Colin A.

New electrolyte solution compositions have been identified for use in lithium-ion batteries after gelling with an appropriate quantity of Kynar polymer. Since the Li + conducting medium is largely the liquid electrolyte component, the assessment of these solutions as suitable lithium-ion cell candidates were investigated before adding the polymer. Selected electrolyte solutions were then used in the preparation of polymer gels. The specific conductivities of Kynar-based gels were determined as a function of salt concentration and polymer concentration. Optimised self-supporting polymer films, based on mixtures of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and lithium hexafluorophosphate (LiPF 6) or lithium tetrafluoroborate (LiBF 4), showed good high current density cycling performance when used as separators in coke and Li 1- xMn 2O 4 (spinel) half-cells.

40 CFR 63.11398 - What definitions apply to this subpart?

Code of Federal Regulations, 2013 CFR

2013-07-01

... acrylonitrile units: acrylic fiber or modacrylic fiber. Acrylonitrile solution polymerization means a process where acrylonitrile and comonomers are dissolved in a solvent to form a polymer solution (typically... resulting reactor polymer solution (spin dope) is filtered and pumped directly to the fiber spinning process...

40 CFR 63.11398 - What definitions apply to this subpart?

Code of Federal Regulations, 2014 CFR

2014-07-01

... acrylonitrile units: acrylic fiber or modacrylic fiber. Acrylonitrile solution polymerization means a process where acrylonitrile and comonomers are dissolved in a solvent to form a polymer solution (typically... resulting reactor polymer solution (spin dope) is filtered and pumped directly to the fiber spinning process...

Unfolding mechanism of lysozyme in various urea solutions: Insights from fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Bang; Zhang, Hongjia; Xi, Wenying; Zhao, Liqing; Liang, Li; Chen, Yantao

2014-11-01

Fluorescence spectroscopic technique is very popular in exploring the folding/unfolding process of proteins. In this paper, unfolding process of hen egg-white lysozyme was investigated in various denaturing solutions. Firstly, polymer solution theory was employed to comprehend the dependence of fluorescence quenching effect on protein concentration, and dynamic contact concentration was suggested as a critical value for related fluorescence experiment. Secondly, it was found that urea alone could not completely unfold lysozyme but did when together with DTT or HCl. Lysozyme was destabilized in concentrated urea solution, but still could maintain its spatial structure. Phase diagram of fluorescence intensities revealed that HCl could enhance the denaturing capacity of urea, resulting in the emergence of intermediate state in the thermodynamic unfolding process of lysozyme.

The Ultra-filtration of Macromolecules with Different Conformations and Configurations through Nanopores

NASA Astrophysics Data System (ADS)

Ge, Hui

This Ph. D. thesis presents our study on the ultrafiltration of polymers with different configurations and conformations; namly, theoretically, the passing of polymer chains through a nanopore under an elongational flow filed has been studied for years, but experimental studies are rare because of two following reasons: (1) lacks a precise method to investigate how individual single polymer chain pass through a nanopore; (2) it is difficult, if not impossible, to obtain a set of polymer samples with a narrow molar mass distribution and a uniform structures; except for linear chains. The central question in this study is to find the critical (minimum) flow rate (qc) for each kind of chains, at which the chains can pass through a given nanopore. A comparison of the measured and calculated qc leads to a better understanding how different chains are deformed, stretched and pulled through a nanopore. We have developed a novel method of combinating static and dynamic laser light scattering (LLS) to precisely measure the relative retention concentration ((C0 - C)/C0). Chapter 1 briefly introduces the theoretical background of how applications and lists some of resent research progresses in this area. Polymer with various configurations and conformations pass through nanopores; including polymer linear chains, stars polymer, branched polymers, polymer micelles are introduced. Among them, the de Gennes and Brochard-Wyart's predictions of polymer linear and star chains passing through nanopores are emphasized, in which they predicted that qc of linear chain is qc ≃ kBT/(3pieta), where kB, T and eta are the Boltzmann constant, the absolutely temperature, and the viscosity of solvent, respectively, independent of both the chain length and the pore size; and for star chains passing through nanopores, there exist a optimal entering arm numbers, namely, the star chains passing through nanopores. Chapter 2 details basic theory of static and dynamic laser light scattering (LLS), including its instrumentation and our ultrafiltration setup. Chapter 3 briefly introduces the sample preparation, including the history and mechanism of anionic living polymerization, as well as how we used a novel home-made set-up to prepare linear polystyrene with different chain lengths and star polystyrene with various arm numbers and lengths. Chapter 4 summarizes our measured critical flow rates (qc) of linear polymer chains with different lengths for nanopores with different sizes, since the flow rate is directly related to the hydrodynamic force, we have developed a sensitive method (down to tens fN) to directly assess how much the hydrodynamic force (Fh) is required to overcome the weak entropy elasticity and stretch individual coiled chains in solution. Our method is completely different from the using existing optical tweezers or AFM, because they measure the relatively stronger enthalpy elasticity. Our results confirm that qc is indeed independent of the chain length, but decreases as the pore size increases. The value of qc is ˜10--200 times smaller than kBT/(3pieta). Such a discrepancy has been attributed to the rough assumption made by de Gennes and his coworkers; namely, each chain segment "blob" confined inside the pore is not a hard sphere so that the effective length along the flow direction is much longer than the pore diameter. Finally, using the solution temperature, we varied the chain conformation, our result shows that q c has a minimum which is near, but not exactly located at the theta temperature, might leading to a better way to determine the true ideal state of a polymer solution, at which all viral coefficients, not only the second vanish. Chapter 5 uses polymer solutions made of different mixtures of linear and star chains, we have demonstrated that flushing these solution mixtures through a nanopore with a properly chosen flow rate can effectively and cleanly separate linear and star chains no matter whether linear chains are larger or smaller than star chains. Chapter 6 further investigates how star-like polystyrene pass through a given nanopore under the flow field. Star polystyrene chains with different arm lengths (LA) and numbers (f) passing through a nanopore (20 nm) under an elongational flow field was investigated in terms of the flow-rate dependent relative retention ((C0 - C)/C0), where C 0 and C are the polymer concentrations before and after the ultrafiltration. Our results reveal that for a given arm length (LA), the critical flow rate (qc,star), below which star chains are blocked, dramatically increases with the total arm numbers (f); but for a given f, is nearly independent on LA, contradictory to the previous prediction made by de Gennes and Brochard-Wyart. We have revised their theory in the region fin < fout and also accounted for the effective length of each blob, where fin and fout are the numbers of arms inside and outside the pore, respectively. In the revision, we show that qc,star is indeed independent of LA but related to f and f in in two different ways, depending on whether fin ≤ f/2 or ≥ f/2. A comparison of our experimental and calculated results reveals that most of star chains pass through the nanopores with fin ˜ f/2. Further study of the temperature dependent (C0 - C)/C 0 of polystyrene in cyclohexane reveals that there exists a minimum of qc,star at ˜38 °C, close to its theta temperature (-34.5 °C).

Thermoresponsive Polymers with Lower Critical Solution Temperature- or Upper Critical Solution Temperature-Type Phase Behaviour Do Not Induce Toxicity to Human Endothelial Cells.

PubMed

Ji, Yuejia; Zhu, Mengxiang; Gong, Yu; Tang, Haoyu; Li, Juan; Cao, Yi

2017-01-01

Thermoresponsive polymers have gained extensive attention as biomedical materials especially for targeted drug delivery systems. We have recently developed water-soluble polypeptide-based thermoresponsive polymers that exhibit lower critical solution temperature (LCST)- or upper critical solution temperature (UCST)-type phase behaviours. In this study, the toxicity of these polymers to human umbilical vein endothelial cells (HUVECs) was investigated to assess the safety and biocompatibility. Up to 100 μg/ml, thermoresponsive polymers did not induce cytotoxicity to HUVECs, showing as unaltered mitochondrial viability assessed as cell counting kit-8 (CCK-8) assay and membrane integrity assessed as lactate dehydrogenase (LDH) assay. Inflammatory response, assessed as the release of chemokine-soluble monocyte chemotactic protein 1 (sMCP-1) and interleukin-8 (IL-8) as well as cytokine IL-6, was not significantly affected by the polymers. In addition, 1 μM thapsigargin (TG), an endoplasmic reticulum (ER) stress inducer, significantly decreased mitochondrial viability, but did not affect membrane integrity or inflammatory response. The presence of thermoresponsive polymers with LCST-type phase behaviour did not further affect the effects of TG. In conclusion, the thermoresponsive polymers used in this study are not toxic to endothelial cells and therefore could be further considered as safe materials for biomedical applications. © 2016 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Liquid crystalline order in mucus

NASA Technical Reports Server (NTRS)

Viney, C.; Huber, A. E.; Verdugo, P.

1993-01-01

Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.

A three-dimensional transient mixed hybrid finite element model for superabsorbent polymers with strain-dependent permeability.

PubMed

Yu, Cong; Malakpoor, Kamyar; Huyghe, Jacques M

2018-05-16

A hydrogel is a cross-linked polymer network with water as solvent. Industrially widely used superabsorbent polymers (SAP) are partially neutralized sodium polyacrylate hydrogels. The extremely large degree of swelling is one of the most distinctive characteristics of such hydrogels, as the volume increase can be about 30 times its original volume when exposed to physiological solution. The large deformation resulting from the swelling demands careful numerical treatment. In this work, we present a biphasic continuum-level swelling model using the mixed hybrid finite element method (MHFEM) in three dimensions. The hydraulic permeability is highly dependent on the swelling ratio, resulting in values that are orders of magnitude apart from each other. The property of the local mass conservation of MHFEM contributes to a more accurate calculation of the deformation as the permeability across the swelling gel in a transient state is highly non-uniform. We show that the proposed model is able to simulate the free swelling of a random-shaped gel and the squeezing of fluid out of a swollen gel. Finally, we make use of the proposed numerical model to study the onset of surface instability in transient swelling.

Effects of anhydrous AlCl3 dopant on the structural, optical and electrical properties of PVA-PVP polymer composite films

NASA Astrophysics Data System (ADS)

Shanmugam, G.; Krishnakumar, V.

2018-05-01

Polymer composite films based on PVA-PVP with AlCl3 as the dopant at different concentrations were prepared using solution casting technique. XRD patterns reveal the increase in amorphousity of the films with AlCl3 doping. Optical absorption studies exhibit that the values of optical absorption coefficient, direct and indirect optical band gaps are found to decrease with increase in AlCl3 concentration. It confirms the charge transfer in complexes between the polymer and the dopant. The dielectric studies show the increase in dielectric constant at low frequency with increasing AlCl3 concentration and temperature. The ac conductivity and ionic conductivity increase with the AlCl3 content and the maximum value at room temperature is found to be 6.89 × 10-4 and 8.05 × 10-5 S/cm for higher AlCl3 doped PVA-PVP film. The estimated ionic conductivity value is three or four orders of magnitude greater than those obtained in the certain representative polymer-salt complexes as reported earlier. Electrical modulus plots confirm the removal of electrode polarization and the low conductivity relaxation time with Al doping. The activation energy estimated from the temperature dependent dc conductivity plot is agreed well with the migration energy calculated from the temperature dependent electric modulus plot.

Effect of pH and temperature upon self-assembling process between poly(aspartic acid) and Pluronic F127.

PubMed

Nita, Loredana E; Chiriac, Aurica P; Bercea, Maria

2014-07-01

The present investigation was made in order to evaluate the capability of self-assembling of the two water soluble polymers, respectively, poly(aspartic acid) and Pluronic F127 into well interpenetrated mixture, and to evidence the connection effects intervened during polymer complex formation to exhibit good stability once formed, as well to understand and correlate the binding strength and the interval between better association domains. The effect of pH and temperature on the interpolymeric complex formation between poly(aspartic acid) and Pluronic F127 was studied by combining rheology with light scattering technique. The solution mixtures between poly(aspartic acid) and Pluronic F127 are Newtonian fluids for all ratios among them. Depending on the polymeric mixture composition and experimental temperature, positive or negative deviations of the experimental values from the additive dependence appear. An interesting behavior was registered around 1/1 wt. ratio between the two polymers, when the hydrodynamic diameter of the interpenetrated polymeric particles decreased suddenly. This allows us to conclude the formation of core-shell micelle structure with poly(aspartic acid) core and Pluronic F127 as shell, performed through strong interactions between polymers. This behavior was sustained by the increase of absolute value of zeta potential owing to the decrease of functional groups number at the surface of micelles. Copyright © 2014 Elsevier B.V. All rights reserved.

Simulation of bipolar charge transport in nanocomposite polymer films

NASA Astrophysics Data System (ADS)

Lean, Meng H.; Chu, Wei-Ping L.

2015-03-01

This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

The effect of the antioxidant on the properties of thiolated poly(aspartic acid) polymers in aqueous ocular formulations.

PubMed

Budai-Szűcs, Mária; Horvát, Gabriella; Gyarmati, Benjámin; Szilágyi, Barnabás Áron; Szilágyi, András; Berkó, Szilvia; Ambrus, Rita; Szabó-Révész, Piroska; Sandri, Giuseppina; Bonferoni, Maria Cristina; Caramella, Carla; Csányi, Erzsébet

2017-04-01

Thiolated polymers are a promising new group of excipients, but their stability against atmospheric oxidation has not been investigated in detail, and only a few efforts have been made to improve their stability. The oxidation of the thiol groups in solutions of thiolated polymers may result in a decrease of mucoadhesion and unpredictable in situ gelation. The aims of our work were to study the stability of aqueous solutions of thiolated polymers and the effects of stabilizing agents. We investigated thiolated poly(aspartic acid) polymers stabilized with dithiothreitol, glutathione or acetylcysteine. The effects of these antioxidants on the gel structure, mucoadhesion and drug release were determined by means of scanning electron microscopy, swelling, rheology, adhesion and drug release tests. It was concluded that the stability of polymer solutions containing antioxidants is sufficient for one day. Polymers stabilized with dithiotreitol demonstrated fast swelling and drug release, but weaker mucoadhesion as compared with the other samples. Polymers stabilized with glutathione displayed the weakest cohesive properties, resulting in fast and uncontrolled drug release and moderate mucoadhesion. Acetylcysteine-stabilized polymers exhibited an optimum cross-linked structure, with free thiol groups ensuring polymer-mucin interactions, resulting in the best mucoadhesive properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of Polymers on the Crystal Growth Rate of Felodipine: Correlating Adsorbed Polymer Surface Coverage to Solution Crystal Growth Inhibition.

PubMed

Schram, Caitlin J; Taylor, Lynne S; Beaudoin, Stephen P

2015-10-20

The bioavailability of orally administered drugs that exhibit poor aqueous solubility can be enhanced with the use of supersaturating dosage forms. Stabilization of these forms by preventing or inhibiting crystallization in solution is an important area of study. Polymers can be used to stabilize supersaturated systems; however, the properties that impact their effectiveness as crystal growth rate inhibitors are not yet fully understood. In this study, the impact of various polymers on the crystal growth rate of felodipine and the conformation of these polymers adsorbed to crystalline felodipine was investigated in order to gain a mechanistic understanding of crystal growth inhibition. It was determined that polymer hydrophobicity impacted polymer adsorption as well as adsorbed polymer conformation. Polymer conformation impacts its surface coverage, which was shown to directly correlate to the polymer's effectiveness as a growth rate inhibitor. By modeling this correlation, it is possible to predict polymer effectiveness given the surface coverage of the polymer.

Processing Solvent Dependent Morphology of Diketopyrrolopyrrole (DPP) based Low Band Gap Polymer and PCBM Blends

NASA Astrophysics Data System (ADS)

Ferdous, Sunzida; Liu, Feng; Russell, Thomas

2013-03-01

Solution processing of polymer semiconductors is widely used for fabrication of low cost organic solar cells. Recently, mixed solvent systems or additive based systems for fabricating polymer solar cells have proven to be beneficial for obtaining high performance devices with multi-length scale morphologies. To control the morphology during the processing step, one needs to understand the effect of solvent as it evaporates to form the final thin film structure. In this study, we used diketopyrrolopyrrole (DPP) based low band gap polymer and phenyl-C71-butyric acid methyl ester (PCBM) blend in a series of mixed solvent systems consisting of a good solvent for both of the active material components, as well as different solvents that are good solvents for PCBM, but poor solvents for the polymer. Different evaporation times of the poor solvents during the drying process, and different solubility of the polymer in these poor solvents as well as their interaction with the substrate play an important role in the final morphology. In-situ GIWAXS studies were performed to observe the evolution of the structure as the solvent evaporates. The final morphologies of the thin film devices were also characterized by AFM, TEM, and various x-ray scattering techniques to correlate the morphology with the obtained device performances.

Monitoring the degrafting of polyelectrolyte brushes by using surface gradients

NASA Astrophysics Data System (ADS)

Ko, Yeongun; Genzer, Jan

Polymer brushes comprise densely grafted polymer chains on surfaces, which possess high stability and high concentration of reactive centers per unit area compared to physisorbed polymer film. Polymer brushes are employed in many applications, including anti-fouling surfaces, cell adhesive surfaces, responsive surfaces, low-friction surfaces, etc. Recently, researchers reported that charged (or chargeable) polymer brushes can be degrafted from substrate while incubated in buffer solutions. Based on previous experiments conducted in our group and by others, we assume that chain degrafting results from the hydrolysis of Si-O groups in head-group of the initiator and/or the ester groups in main body of the initiator. The kinetic of hydrolysis is affected by mechanical forces acting on the initiator. Those forces depend on the molecular weight and the grafting density of the brush, and the concentration and distribution of charges along the macromolecule (tuned by pH - for weak electrolytes - and concentration of external salt). In this work, we study the stability of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) brushes in two solvents (ethanol and water) at various pH values in water and under different levels of external salt concentration. National Science Foundation.

Diffusion of Sticky Nanoparticles in a Polymer Melt: Crossover from Suppressed to Enhanced Transport

DOE PAGES

Carroll, Bobby; Bocharova, Vera; Carrillo, Jan-Michael Y.; ...

2018-03-09

The self-diffusion of a single large particle in a fluid is usually described by the classic Stokes–Einstein (SE) hydrodynamic relation. However, there are many fluids where the SE prediction for nanoparticles diffusion fails. These systems include diffusion of nanoparticles in porous media, in entangled and unentangled polymer melts and solutions, and protein diffusion in biological environments. A fundamental understanding of the microscopic parameters that govern nanoparticle diffusion is relevant to a wide range of applications. Here in this work, we present experimental measurements of the tracer diffusion coefficient of small and large nanoparticles that experience strong attractions with unentangled andmore » entangled polymer melt matrices. For the small nanoparticle system, a crossover from suppressed to enhanced diffusion is observed with increasing polymer molecular weight. We interpret these observations based on our theoretical and simulation insights of the preceding article (paper 1) as a result of a crossover from an effective hydrodynamic core–shell to a nonhydrodynamic vehicle mechanism of transport, with the latter strongly dependent on polymer–nanoparticle desorption time. In conclusion, a general zeroth-order qualitative picture for small sticky nanoparticle diffusion in polymer melts is proposed.« less

Diffusion of Sticky Nanoparticles in a Polymer Melt: Crossover from Suppressed to Enhanced Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carroll, Bobby; Bocharova, Vera; Carrillo, Jan-Michael Y.

The self-diffusion of a single large particle in a fluid is usually described by the classic Stokes–Einstein (SE) hydrodynamic relation. However, there are many fluids where the SE prediction for nanoparticles diffusion fails. These systems include diffusion of nanoparticles in porous media, in entangled and unentangled polymer melts and solutions, and protein diffusion in biological environments. A fundamental understanding of the microscopic parameters that govern nanoparticle diffusion is relevant to a wide range of applications. Here in this work, we present experimental measurements of the tracer diffusion coefficient of small and large nanoparticles that experience strong attractions with unentangled andmore » entangled polymer melt matrices. For the small nanoparticle system, a crossover from suppressed to enhanced diffusion is observed with increasing polymer molecular weight. We interpret these observations based on our theoretical and simulation insights of the preceding article (paper 1) as a result of a crossover from an effective hydrodynamic core–shell to a nonhydrodynamic vehicle mechanism of transport, with the latter strongly dependent on polymer–nanoparticle desorption time. In conclusion, a general zeroth-order qualitative picture for small sticky nanoparticle diffusion in polymer melts is proposed.« less

Lower Critical Solution Temperature (LCST) and drug conjugation of polyacetal

NASA Astrophysics Data System (ADS)

de Silva, Chathuranga; Samanta, Sanjoy; Leophairatana, Porakrit; Koberstein, Jeffrey

There has been an increasing focus in polymer research for materials that can efficiently deliver therapeutics to a pre-identified solid tumor target. Due to their unique properties, stimuli responsive polymers (SRPs) have been of particular interest. One such novel SRP is a polyacetal-based copolymer (PAC). PAC shows a remarkable temperature response (LCST) that is linearly dependent on composition. Here, we discuss the fundamental physical origins of this LCST behavior, exhibited by this polymer. Our results indicate that the observed LCST scales linearly with the number of carbon and oxygen atoms in the polymer repeat units, allowing for precise control over the LCST. We design PAC to include cancer therapeutics in its polymer-backbone, utilizing strategies to modify step-growth polymerization to obtain, for the first time, temperature-responsive main-chain drug conjugates. The temperature response in these main-chain drug conjugates allow for effective delivery of therapeutics to the tumor site, followed by acid-hydrolysis in acidic local tumor environments, to release pristine therapeutics directly at the tumor site. Due to these reasons, we foresee PAC to be in the forefront of soft-matter SRP drug-delivery systems.

Reduction of the viscosity of solutions viscosified with xanthan gum polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bridges, K.L.; Kalinski, K.L.

1991-10-08

This patent describes a process for reducing the viscosity of a drilling fluid containing Xanthan gum polymer solution. It comprises: contacting the drilling fluid with hydrogen peroxide and adjusting the pH of the solution to a level of at least about between 8 and 10.

Mechanisms behind injecting the combination of nano-clay particles and polymer solution for enhanced oil recovery

NASA Astrophysics Data System (ADS)

Khalili Nezhad, Seyyed Shahram; Cheraghian, Goshtasp

2016-08-01

Laboratory investigations and field applications have proved injection of polymer solution to be an effective means to improve oil recovery for reservoirs of medium oil viscosity. The incremental oil produced in this case is the result of an increase in areal and vertical sweep efficiencies. Biopolymers and synthetic polymers are the major categories used in the petroleum industry for specific reasons. Biopolymers like xanthan are limited in their application as they are more susceptible to biodegradation. Synthetic polymers like Hydrolyzed PolyAcrylaMide (HPAM) have a much wider application as they are less susceptible to biodegradation. Furthermore, development of nanotechnology has successfully provided technical and economical viable alternatives for present materials. The objective of this study is to investigate the effect of combining clay nanoparticles with polymer solution on oil recovery. This paper includes a history match of both one-dimensional and two-dimensional polymer floods using a three-dimensional numerical model for fluid flow and mass transport. Results indicated that the amount of polymer adsorption decreased when clay nanoparticles were added to the PolyAcrylaMide solution; however, mobility ratio improvement is believed to be the main contributor for the proposed method in order to enhance much oil recovery compared to xanthan flood and HPAM flood.

Germanium films by polymer-assisted deposition

DOEpatents

Jia, Quanxi; Burrell, Anthony K.; Bauer, Eve; Ronning, Filip; McCleskey, Thomas Mark; Zou, Guifu

2013-01-15

Highly ordered Ge films are prepared directly on single crystal Si substrates by applying an aqueous coating solution having Ge-bound polymer onto the substrate and then heating in a hydrogen-containing atmosphere. A coating solution was prepared by mixing water, a germanium compound, ethylenediaminetetraacetic acid, and polyethyleneimine to form a first aqueous solution and then subjecting the first aqueous solution to ultrafiltration.

Electrospinning biopolymers from ionic liquids requires control of different solution properties than volatile organic solvents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zavgorodnya, Oleksandra; Shamshina, Julia L.; Bonner, Jonathan R.

Here, we report the correlation between key solution properties and spinability of chitin from the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C 2mim][OAc]), and the similarities and differences to electrospinning solutions of non-ionic polymers in volatile organic compounds (VOCs). We found that when electrospinning is conducted from ILs, conductivity and surface tension are not the key parameters regulating spinability, while solution viscosity and polymer concentration are. Contrarily, for electrospinning of polymers from VOCs, solution conductivity and viscosity have been reported to be among some of the most important factors controlling fiber formation. For chitin electrospun from [C 2mim][OAc], we found bothmore » a critical chitin concentration required for continuous fiber formation (> 0.20 wt%) and a required viscosity for the spinning solution (between ca. 450 – 1500 cP). The high viscosities of the biopolymer-IL solutions made it possible to electrospin solutions with low, less than 1 wt% of polymer concentration and produce thin fibers without the need to adjust the electrospinning parameters. These results suggest new prospects for the control of fiber architecture in non-woven mats, which is crucial for materials performance.« less

Electrospinning biopolymers from ionic liquids requires control of different solution properties than volatile organic solvents

DOE PAGES

Zavgorodnya, Oleksandra; Shamshina, Julia L.; Bonner, Jonathan R.; ...

2017-04-27

Here, we report the correlation between key solution properties and spinability of chitin from the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C 2mim][OAc]), and the similarities and differences to electrospinning solutions of non-ionic polymers in volatile organic compounds (VOCs). We found that when electrospinning is conducted from ILs, conductivity and surface tension are not the key parameters regulating spinability, while solution viscosity and polymer concentration are. Contrarily, for electrospinning of polymers from VOCs, solution conductivity and viscosity have been reported to be among some of the most important factors controlling fiber formation. For chitin electrospun from [C 2mim][OAc], we found bothmore » a critical chitin concentration required for continuous fiber formation (> 0.20 wt%) and a required viscosity for the spinning solution (between ca. 450 – 1500 cP). The high viscosities of the biopolymer-IL solutions made it possible to electrospin solutions with low, less than 1 wt% of polymer concentration and produce thin fibers without the need to adjust the electrospinning parameters. These results suggest new prospects for the control of fiber architecture in non-woven mats, which is crucial for materials performance.« less

Hydraulic permeability of bentonite-polymer composites for application in landfill technology

NASA Astrophysics Data System (ADS)

Dehn, Hanna; Haase, Hanna; Schanz, Tom

2015-04-01

Bentonites are often used as barrier materials in landfill technology to prevent infiltration of leachates to the natural environment. Since decades, geoenvironmental engineering aims at improving the hydro-mechanical performance of landfill liners. Various studies on the permeability performance of geosynthetic clay liners (GCLs) show effects of non-standard liquids on behaviour of Na+-bentonite regarding its sealing capacity. With increasing concentration of chemical aggressive solutions the sealing capacity decreases (Shackelford et al. 2000). An opportunity to improve the hydraulic permeability of the bentonites is the addition of polymers. The changes in hydraulic permeability performance of polymer treated and untreated bentonites while adding chemical aggressive solutions were studied by several authors. Results obtained by Scalia et al. (2014) illustrate that an increase in permeability can be prevented by adding polymer to Na+-bentonite. On the other hand, Ashmawy et al. (2002) presented results on the incapability of several commercial bentonite-polymer-products. The objective of this study is to characterize the influence of polymer addition on hydraulic performance of Na+-bentonite systematically. Therefore, the influence of 1% polymer addition of cationic and anionic polyacrylamide on the swelling pressure and hydraulic permeability of MX 80 bentonite was investigated. Preparation of bentonite-polymer composites was conducted (1) in dry conditions and (2) using solution-intercalation method. Experiments on hydraulic permeability were carried out using distilled water as well as CaCl2-solution. References Ashmawy, A. K., El-Hajji, D., Sotelo, N. & Muhammad, N. (2002), `Hydraulic Performance of Untreated and Polymer-treated Bentonite in Inorganic Landfill Leachates', Clays and Clay Minerals 50(5), 546-552. Scalia, J., Benson, C., Bohnhoff, G., Edil, T. & Shackelford, C. (2014), 'Long-Term Hydraulic Conductivity of a Bentonite-Polymer Composite Permeated with Aggressive Inorganic Solutions', Journal of Geotechnical and Geoenvironmental Engineering 140(3). Shackelford, C. D., Benson, C. H., Katsumi, T., Edil, T. B. & Lin, L. (2000), 'Evaluating the hydraulic conductivity of GCLs permeated with non-standard liquids', Geotextiles and Geomembranes 18, 133-161.

Method for making nanoporous hydrophobic coatings

DOEpatents

Fan, Hongyou; Sun, Zaicheng

2013-04-23

A simple coating method is used to form nanoporous hydrophobic films that can be used as optical coatings. The method uses evaporation-induced self-assembly of materials. The coating method starts with a homogeneous solution comprising a hydrophobic polymer and a surfactant polymer in a selective solvent. The solution is coated onto a substrate. The surfactant polymer forms micelles with the hydrophobic polymer residing in the particle core when the coating is dried. The surfactant polymer can be dissolved and selectively removed from the separated phases by washing with a polar solvent to form the nanoporous hydrophobic film.

Dynamics of polymers in elongational flow studied by the neutron spin-echo technique

NASA Astrophysics Data System (ADS)

Rheinstädter, Maikel C.; Sattler, Rainer; Häußler, Wolfgang; Wagner, Christian

2010-09-01

The nanoscale fluctuation dynamics of semidilute high molecular weight polymer solutions of polyethylenoxide (PEO) in D 2O under non-equilibrium flow conditions were studied by the neutron spin-echo technique. The sample cell was in contraction flow geometry and provided a pressure driven flow with a high elongational component that stretched the polymers most efficiently. Neutron scattering experiments in dilute polymer solutions are challenging because of the low polymer concentration and corresponding small quasi-elastic signals. A relaxation process with relaxation times of about 10 ps was observed, which shows anisotropic dynamics with applied flow.

Sorption of ochratoxin A from aqueous solutions using β-cyclodextrin-polyurethane polymer.

PubMed

Appell, Michael; Jackson, Michael A

2012-02-01

The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1-10 μg·L(-1). These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples.

Application of a novel 3-fluid nozzle spray drying process for the microencapsulation of therapeutic agents using incompatible drug-polymer solutions.

PubMed

Sunderland, Tara; Kelly, John G; Ramtoola, Zebunnissa

2015-04-01

The aim of this study was to evaluate a novel 3-fluid concentric nozzle (3-N) spray drying process for the microencapsulation of omeprazole sodium (OME) using Eudragit L100 (EL100). Feed solutions containing OME and/or EL100 in ethanol were assessed visually for OME stability. Addition of OME solution to EL100 solution resulted in precipitation of OME followed by degradation of OME reflected by a colour change from colourless to purple and brown. This was related to the low pH of 2.8 of the EL100 solution at which OME is unstable. Precipitation and progressive discoloration of the 2-fluid nozzle (2-N) feed solution was observed over the spray drying time course. In contrast, 3-N solutions of EL100 or OME in ethanol were stable over the spray drying period. Microparticles prepared using either nozzle showed similar characteristics and outer morphology however the internal morphology was different. DSC showed a homogenous matrix of drug and polymer for 2-N microparticles while 3-N microparticles had defined drug and polymer regions distributed as core and coat. The results of this study demonstrate that the novel 3-N spray drying process can allow the microencapsulation of a drug using an incompatible polymer and maintain the drug and polymer in separate regions of the microparticles.

In situ polymerization of monomers for polyphenylquinoxaline/graphite

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D.

1973-01-01

Methods currently used to prepare fiber reinforced, high temperature resistant polyphenylquinoxaline (PPQ) composites employ extremely viscous, low solids content solutions of high molecular weight PPQ polymers. An improved approach, described in this report, consists of impregnating the fiber with a solution of the appropriate monomers instead of a solution of previously synthesized high molecular weight polymer. Polymerization of the monomers occurs in situ on the fiber during the solvent removal and curing stages. The in situ polymerization approach greatly simplifies the fabrication of PPQ graphite fiber composites. The use of low viscosity monomeric type solutions facilitates fiber wetting, permits a high solids content, and eliminates the need for prior polymer synthesis.

Membrane separation of ionic liquid solutions

DOEpatents

Campos, Daniel; Feiring, Andrew Edward; Majumdar, Sudipto; Nemser, Stuart

2015-09-01

A membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid. Preferably the polymer is a polymer that includes polymerized perfluoro-2,2-dimethyl-1,3-dioxole (PDD). The process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution. This membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid, and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner.

"JCE" Classroom Activity #106. Sequestration of Divalent Metal Ion by Superabsorbent Polymer in Diapers

ERIC Educational Resources Information Center

Chen, Yueh-Huey; Lin, Jia-Ying; Lin, Li-Pin; Liang, Han; Yaung, Jing-Fun

2010-01-01

This activity explores an alternative use of a superabsorbent polymer known as a water absorbing material. A dilute solution of CuCl[subscript 2] is treated with a small piece of unused disposable diaper containing superabsorbent sodium polyacrylates. The polymer is used for the removal of Cu[superscript 2+] ions from the solution. The…

Preparation of prepreg graphite tape with insoluble polymer

NASA Technical Reports Server (NTRS)

Yates, C. I.

1973-01-01

Powdered polymer is finely ground. Second polymer, soluble, is mixed with appropriate solvent. Milled polymer and graphite filaments are added to soluble polymer-solvent solution to create slurry. Slurry is dried, and when ready for processing, the soluble, binder-polymer is removed by heat during precure or cure cycle.

Method for polymer synthesis in a reaction well

DOEpatents

Brennan, Thomas M.

1998-01-01

A method of synthesis for building a polymer chain, oligonucleotides in particular, by sequentially adding monomer units to at least one solid support for growing and immobilizing a polymer chain thereon in a liquid reagent solution. The method includes the step of: A) depositing a liquid reagent in a reaction well (26) in contact with at least one solid support and at least one monomer unit of the polymer chain affixed to the solid support. The well (26) includes at least one orifice (74) extending into the well (26), and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well (26) to enable polymer chain growth on the solid support. The method further includes the step of B) expelling the reagent solution from the well (26), while retaining the polymer chain therein. This is accomplished by applying a first gas pressure to the reaction well such that a pressure differential between the first gas pressure and a second gas pressure exerted on an exit (80) of the orifice (74) exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well (26) through the orifice exit (80).

Method for polymer synthesis in a reaction well

DOEpatents

Brennan, T.M.

1998-09-29

A method of synthesis is described for building a polymer chain, oligonucleotides in particular, by sequentially adding monomer units to at least one solid support for growing and immobilizing a polymer chain thereon in a liquid reagent solution. The method includes the step of: (A) depositing a liquid reagent in a reaction well in contact with at least one solid support and at least one monomer unit of the polymer chain affixed to the solid support. The well includes at least one orifice extending into the well, and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well to enable polymer chain growth on the solid support. The method further includes the step of (B) expelling the reagent solution from the well, while retaining the polymer chain therein. This is accomplished by applying a first gas pressure to the reaction well such that a pressure differential between the first gas pressure and a second gas pressure exerted on an exit of the orifice exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well through the orifice exit. 9 figs.

Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

PubMed

Luo, Nan; Xu, Rongle; Yang, Min; Yuan, Xing; Zhong, Hui; Fan, Yaobo

2015-12-01

A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix. The formation mechanisms, permeation, and anti-fouling performance of the PGF composite membrane were measured with different amounts of AM in the doping solutions. The results showed that the grafting composite membrane improved the interfacial bonding strength and permeability, and the peeling strength was improved by 32.6% for PGF composite membranes with an AM concentration at 2wt.%. Copyright © 2015. Published by Elsevier B.V.

On the abnormal "forced hydration" behavior of P(MEA-co-OEGA) aqueous solutions during phase transition from infrared spectroscopic insights.

PubMed

Hou, Lei; Wu, Peiyi

2016-06-21

Turbidity, DLS and FTIR measurements in combination with the perturbation correlation moving window (PCMW) technique and 2D correlation spectroscopy (2Dcos) analysis have been utilized to investigate the LCST-type transition of a oligo ethylene glycol acrylate-based copolymer (POEGA) in aqueous solutions in this work. As demonstrated in turbidity and DLS curves, the macroscopic phase separation was sharp and slightly concentration dependent. Moreover, individual chemical groups along polymer chains also display abrupt changes in temperature-variable IR spectra. However, according to conventional IR analysis, the C-H groups present obvious dehydration, whereas C[double bond, length as m-dash]O and C-O-C groups exhibit anomalous "forced hydration" during the steep phase transition. From these analyses together with the PCMW and 2Dcos results, it has been confirmed that the hydrophobic interaction among polymer chains drove the chain collapse and dominated the phase transition. In addition, the unexpected enhanced hydration behavior of C[double bond, length as m-dash]O and C-O-C groups was induced by forced hydrogen bonding between polar groups along polymer chains and entrapped water molecules in the aggregates, which originated from the special chemical structure of POEGA.

Synthesis and characterization of novel polymers from non-petroleum sources for use in enhanced oil recovery. Final report, July 1, 1983-June 30, 1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogen-Esch, T.E.

1984-01-01

Accomplishments for the past year are discussed for grafting of acrylamide to: (1) starch and related polysaccharides; and (2) cellulose solutions. In grafting acrylamide to various polysaccharide substrates such as okra polysaccharide, yellow dextrin, waxy corn starch, potato amylose, gum arabic, the efficiency of Ce/sup 4 +/ as initiator was found to vary from 0.02 to 0.89, depending on reaction conditions. Okra polysaccharide was isolated, characterized, and evaluated for use in enhanced oil recovery. A series of experiments designed to increase the viscosifying power of certain polymers by chain extension techniques has also been conducted. Characterization of the polymers bymore » ultracentrifugation, size exclusion chromatography, membrane filtration, multi-cell equilibrium dialysis, and rheological studies has also been done. In grafting of acrylamide to cellulose solutions the following two courses were taken: (1) dissolution of cellulose in 70% aqueous zinc chloride, followed by Ce/sup 4 +/ initiated grafting of acrylamide, and (2) introduction of a 1,2-diol substituent onto the anhydroglucose units of the cellulose chain via dissolution of cellulose in concentrated aqueous NaOH, followed by treatment with glyceryl chlorohydrin. Considerable progress has been made via both approaches. 11 refs., 1 fig., 1 tab.« less

Synthesis and Examination of Nanocomposites Based on Poly(2-hydroxyethyl methacrylate) for Medicinal Use

NASA Astrophysics Data System (ADS)

Kukolevska, Olena S.; Gerashchenko, Igor I.; Borysenko, Mykola V.; Pakhlov, Evgenii M.; Machovsky, Michal; Yushchenko, Tetyana I.

2017-02-01

Preparation of poly(2-hydroxyethyl methacrylate) (PHEMA) based nanocomposites using different approaches such as synthesis with water as the porogen, filling of polymer matrix by silica and formation of interpenetrating polymer networks with polyurethane was demonstrated. Incorporation of various biologically active compounds (BAC) such as metronidazole, decamethoxin, zinc sulphate, silver nitrate or amino acids glycine and tryptophan into nanocomposites was achieved. BAC were introduced into the polymer matrix either (1) directly, or (2) with a solution of colloidal silica, or (3) through immobilization on silica (sol-densil). Morphology of prepared materials was investigated by laser scanning microscopy and low-vacuum scanning electron microscopy. In vacuum freeze-drying, prior imaging was proposed for improving visualization of the porous structure of composites. The interaction between PHEMA matrix and silica filler was investigated by IR spectroscopy. Adsorption of 2-hydroxyethyl methacrylate and BAC from aqueous solution on the silica surface was also examined. Phase composition and thermal stability of composites were studied by the differential thermogravimetry/differential thermal analysis. Release of BAC into water medium from prepared composites were shown to depend on the synthetic method and differed significantly. Obtained PHEMA-base materials which are characterized by controlled release of BAC have a strong potential for application in manufacturing of different surgical devices like implants, catheters and drainages.

The production of ultrathin polyimide films for the solar sail program and Large Space Structures Technology (LSST): A feasibility study

NASA Technical Reports Server (NTRS)

Forester, R. H.

1978-01-01

Polyimide membranes of a thickness range from under 0.01 micron m to greater than 1 micron m can be produced at an estimated cost of 50 cents per sq m (plus the cost of the polymer). The polymer of interest is dissolved in a solvent which is solube in water. The polymer or casting solution is allowed to flow down an inclined ramp onto a water surface where a pool of floating polymer develops. The solvent dissolves into the water lowering the surface tension of the water on equently, the contact angle of the polymer pool is very low and the edge of the pool is very thin. The solvent dissolves from this thin region too rapidly to be replenished from the bulk of the pool and a solid polymer film forms. Firm formation is rapid and spontaneous and the film spreads out unaided, many feet from the leading edge of the pool. The driving force for this process is the exothermic solution of the organic solvent from the polymer solution into the water.

Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

PubMed

Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

2015-09-15

Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format.

The in situ synthesis of PbS nanocrystals from lead(II) n-octylxanthate within a 1,3-diisopropenylbenzene–bisphenol A dimethacrylate sulfur copolymer

PubMed Central

Bear, J. C.; Mayes, A. G.; Parkin, I. P.; O'Brien, P.

2017-01-01

The synthesis of lead sulfide nanocrystals within a solution processable sulfur ‘inverse vulcanization’ polymer thin film matrix was achieved from the in situ thermal decomposition of lead(II) n-octylxanthate, [Pb(S2COOct)2]. The growth of nanocrystals within polymer thin films from single-source precursors offers a faster route to networks of nanocrystals within polymers when compared with ex situ routes. The ‘inverse vulcanization’ sulfur polymer described herein contains a hybrid linker system which demonstrates high solubility in organic solvents, allowing solution processing of the sulfur-based polymer, ideal for the formation of thin films. The process of nanocrystal synthesis within sulfur films was optimized by observing nanocrystal formation by X-ray photoelectron spectroscopy and X-ray diffraction. Examination of the film morphology by scanning electron microscopy showed that beyond a certain precursor concentration the nanocrystals formed were not only within the film but also on the surface suggesting a loading limit within the polymer. We envisage this material could be used as the basis of a new generation of materials where solution processed sulfur polymers act as an alternative to traditional polymers. PMID:28878986

Demonstrating the importance of polymer-conjugate conformation in solution on its therapeutic output: Diethylstilbestrol (DES)-polyacetals as prostate cancer treatment.

PubMed

Giménez, Vanessa; James, Craig; Armiñán, Ana; Schweins, Ralf; Paul, Alison; Vicent, María J

2012-04-30

The design of improved polymeric carriers to be used in the next generation of polymer therapeutics is an ongoing challenge. Biodegradable systems present potential advantages regarding safety benefit apart from the possibility to use higher molecular weight (Mw) carriers allowing PK optimization, by exploiting the enhanced permeability and retention (EPR)-mediated tumor targeting. Within this context, we previously designed pH-responsive polyacetalic systems, tert-polymers, where a drug with the adequate diol-functionality was incorporated within the polymer mainchain. The synthetic, non-steroidal estrogen, diethylstilboestrol (DES) clinically used for the treatment of advanced prostate cancer was chosen as drug. In order to improve the properties of this tert-polymer, novel polyacetalic systems as block-co-polymers, with more defined structure have been obtained. This second generation polyacetals allowed higher drug capacity than the tert-polymer, a biphasic DES release profile at acidic pH and due to its controlled amphiphilic character readily formed micelle-like structures in solution. These features result in an enhancement of conjugate therapeutic value in selected prostate cancer cell models. Exhaustive physico-chemical characterization focusing on nanoconjugate solution behavior and using advanced techniques, such as, pulsed-gradient spin-echo NMR (PGSE-NMR) and small-angle neutron scattering (SANS), has been carried out in order to demonstrate this hypothesis. Clear evidence of significantly different conformation in solution has been obtained for both polyacetals. These results demonstrate that an adequate control on molecular or supramolecular conformation in solution with polymer therapeutics is crucial in order to achieve the desired therapeutic output. Copyright © 2012 Elsevier B.V. All rights reserved.

Morphology and structure of polymer layers protecting dental enamel against erosion.

PubMed

Beyer, Markus; Reichert, Jörg; Sigusch, Bernd W; Watts, David C; Jandt, Klaus D

2012-10-01

Human dental erosion caused by acids is a major factor for tooth decay. Adding polymers to acidic soft drinks is one important approach to reduce human dental erosion caused by acids. The aim of this study was to investigate the thickness and the structure of polymer layers adsorbed in vitro on human dental enamel from polymer modified citric acid solutions. The polymers propylene glycol alginate (PGA), highly esterified pectin (HP) and gum arabic (GA) were used to prepare polymer modified citric acids solutions (PMCAS, pH 3.3). With these PMCAS, enamel samples were treated for 30, 60 and 120s respectively to deposit polymer layers on the enamel surface. Profilometer scratches on the enamel surface were used to estimate the thickness of the polymer layers via atomic force microscopy (AFM). The composition of the deposited polymer layers was investigated with X-ray photoelectron spectroscopy (XPS). In addition the polymer-enamel interaction was investigated with zeta-potential measurements and scanning electron microscopy (SEM). It has been shown that the profilometer scratch depth on the enamel with deposited polymers was in the range of 10nm (30s treatment time) up to 25nm (120s treatment time). Compared to this, the unmodified CAS-treated surface showed a greater scratch depth: from nearly 30nm (30s treatment time) up to 60nm (120s treatment time). Based on XPS measurements, scanning electron microscopy (SEM) and zeta-potential measurements, a model was hypothesized which describes the layer deposited on the enamel surface as consisting of two opposing gradients of polymer molecules and hydroxyapatite (HA) particles. In this study, the structure and composition of polymer layers deposited on in vitro dental enamel during treatment with polymer modified citric acid solutions were investigated. Observations are consistent with a layer consisting of two opposing gradients of hydroxyapatite particles and polymer molecules. This leads to reduced erosive effects of citric acid solutions on dental enamel surfaces. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Aggregation, adsorption, and surface properties of multiply end-functionalized polystyrenes.

PubMed

Ansari, Imtiyaz A; Clarke, Nigel; Hutchings, Lian R; Pillay-Narrainen, Amilcar; Terry, Ann E; Thompson, Richard L; Webster, John R P

2007-04-10

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C8F17 fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted FxdPSy, where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blended with unfunctionalized polystyrene, hPS. Nuclear reaction analysis experiments show that FxdPSy polymers adsorb spontaneously to solution and blend surfaces, resulting in a reduction in surface energy inferred from contact angle analysis. Aggregation of functionalized polymers in the bulk was found to be sensitive to FxdPSy structure and closely related to surface properties. At low concentrations, the functionalized polymers are freely dispersed in the hPS matrix, and in this range, the surface excess concentration grows sharply with increasing bulk concentration. At higher concentrations, surface excess concentrations and contact angles reach a plateau, small-angle neutron scattering data indicate small micellar aggregates of six to seven F2dPS10 polymer chains and much larger aggregates of F4dPS10. Whereas F2dPS10 aggregates are miscible with the hPS matrix, F4dPS10 forms a separate phase of multilamellar vesicles. Using neutron reflectometry (NR), we found that the extent of the adsorbed layer was approximately half the lamellar spacing of the multilamellar vesicles. NR data were fitted using an error function profile to describe the concentration profile of the adsorbed layer, and reasonable agreement was found with concentration profiles predicted by the SCFT model. The thermodynamic sticking energy of the fluorocarbon-functionalized polymer chains to the blend surface increases from 5.3kBT for x = 2 to 6.6kBT for x = 4 but appears to be somewhat dependent upon the blend concentration.

Current applications of foams formed from mixed surfactant-polymer solutions.

PubMed

Bureiko, Andrei; Trybala, Anna; Kovalchuk, Nina; Starov, Victor

2015-08-01

Foams cannot be generated without the use of special foaming agents, as pure liquids do not foam. The most common foaming agents are surfactants, however often for foam stability one active agent is not enough, it is necessary to add other component to increase foam lifetime. Foams on everyday use are mostly made from mixture of different components. Properly chosen combinations of two active ingredients lead to a faster foam formation and increased foam stability. During the last decade polymers (mainly polyelectrolytes and proteins) have become frequently used additives to foaming solutions. Mixtures of surfactants and polymers often demonstrate different foaming properties in comparison to surfactant only or polymer only solutions. The nature of surfactant-polymer interactions is complicated and prediction of resulting foaming properties of such formulations is not straightforward. Properties and foaming of surfactant-polymer mixtures are discussed as well as current applications of foams and foaming agents as foams are widely used in cosmetics, pharmaceutics, medicine and the food industry. Copyright © 2014 Elsevier B.V. All rights reserved.

Nonequilibrium thermodynamics of dilute polymer solutions in flow.

PubMed

Latinwo, Folarin; Hsiao, Kai-Wen; Schroeder, Charles M

2014-11-07

Modern materials processing applications and technologies often occur far from equilibrium. To this end, the processing of complex materials such as polymer melts and nanocomposites generally occurs under strong deformations and flows, conditions under which equilibrium thermodynamics does not apply. As a result, the ability to determine the nonequilibrium thermodynamic properties of polymeric materials from measurable quantities such as heat and work is a major challenge in the field. Here, we use work relations to show that nonequilibrium thermodynamic quantities such as free energy and entropy can be determined for dilute polymer solutions in flow. In this way, we determine the thermodynamic properties of DNA molecules in strong flows using a combination of simulations, kinetic theory, and single molecule experiments. We show that it is possible to calculate polymer relaxation timescales purely from polymer stretching dynamics in flow. We further observe a thermodynamic equivalence between nonequilibrium and equilibrium steady-states for polymeric systems. In this way, our results provide an improved understanding of the energetics of flowing polymer solutions.

Selective and Responsive Nanopore-Filled Membranes

DTIC Science & Technology

2011-03-14

Materials Science and Engineering Poster Competition 15. Chen, H.; Elabd, Y.A. Ionic Liquid Polymers: Electrospinning and Solution Properties. Fall...hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project include (1) synthesizing stimuli...on polymer-polymer nanocomposites of hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project

Stochastic entangled chain dynamics of dense polymer solutions.

PubMed

Kivotides, Demosthenes; Wilkin, S Louise; Theofanous, Theo G

2010-10-14

We propose an adjustable-parameter-free, entangled chain dynamics model of dense polymer solutions. The model includes the self-consistent dynamics of molecular chains and solvent by describing the former via coarse-grained polymer dynamics that incorporate hydrodynamic interaction effects, and the latter via the forced Stokes equation. Real chain elasticity is modeled via the inclusion of a Pincus regime in the polymer's force-extension curve. Excluded volume effects are taken into account via the combined action of coarse-grained intermolecular potentials and explicit geometric tracking of chain entanglements. We demonstrate that entanglements are responsible for a new (compared to phantom chain dynamics), slow relaxation mode whose characteristic time scale agrees very well with experiment. Similarly good agreement between theory and experiment is also obtained for the equilibrium chain size. We develop methods for the solution of the model in periodic flow domains and apply them to the computation of entangled polymer solutions in equilibrium. We show that the number of entanglements Π agrees well with the number of entanglements expected on the basis of tube theory, satisfactorily reproducing the latter's scaling of Π with the polymer volume fraction φ. Our model predicts diminishing chain size with concentration, thus vindicating Flory's suggestion of excluded volume effects screening in dense solutions. The predicted scaling of chain size with φ is consistent with the heuristic, Flory theory based value.

Role of Molecular Interactions for Synergistic Precipitation Inhibition of Poorly Soluble Drug in Supersaturated Drug-Polymer-Polymer Ternary Solution.

PubMed

Prasad, Dev; Chauhan, Harsh; Atef, Eman

2016-03-07

We are reporting a synergistic effect of combined Eudragit E100 and PVP K90 in precipitation inhibition of indomethacin (IND) in solutions at low polymer concentration, a phenomenon that has significant implications on the usefulness of developing novel ternary solid dispersion of poorly soluble drugs. The IND supersaturation was created by cosolvent technique, and the precipitation studies were performed in the absence and the presence of individual and combined PVP K90 and Eudragit E100. The studies were also done with PEG 8000 as a noninteracting control polymer. A continuous UV recording of the IND absorption was used to observe changes in the drug concentration over time. The polymorphic form and morphology of precipitated IND were characterized by Raman spectroscopy and scanning electron microscopy. The change in the chemical shift in solution (1)H NMR was used as novel approach to probe IND-polymer interactions. Molecular modeling was used for calculating binding energy between IND-polymer as another indication of IND-polymer interaction. Spontaneous IND precipitation was observed in the absence of polymers. Eudragit E100 showed significant inhibitory effect on nuclei formation due to stronger interaction as reflected in higher binding energy and greater change in chemical shift by NMR. PVP K90 led to significant crystal growth inhibition due to adsorption on growing IND crystals as confirmed by modified crystal habit of precipitate in the presence of PVP K90. Combination of polymers resulted in a synergistic precipitation inhibition and extended supersaturation. The NMR confirmed interaction between IND-Eudragit E100 and IND-PVP K90 in solution. The combination of polymers showed similar peak shift albeit using lower polymer concentration indicating stronger interactions. The results established the significant synergistic precipitation inhibition effect upon combining Eudragit E100 and PVP K90 due to drug-polymer interaction.

Capillary Viscometer for Fully Automated Measurement of the Concentration and Shear Dependence of the Viscosity of Macromolecular Solutions

PubMed Central

Grupi, Asaf; Minton, Allen P.

2014-01-01

The construction and operation of a novel viscometer/rheometer are described. The instrument is designed to measure the viscosity of a macromolecular solution while automatically varying both solute concentration and shear rate. Viscosity is calculated directly from Poiseuille's Law, given the measured difference in pressure between two ends of a capillary tube through which the solution is flowing at a known rate. The instrument requires as little as 0.75 ml of a solution to provide a full profile of viscosity as a function of concentration and shear rate, and can measure viscosities as high as 500 cP and as low as 1 cP, at shear rates between 10 and 2 × 103 s-1. The results of control experiments are presented to document the accuracy and precision of measurement at both low and high concentration of synthetic polymers and proteins. PMID:23130673

The effect of environmental and process parameters on flocculation treatment of high dry matter swine manure with polymers.

PubMed

Masse, Lucie; Massé, Daniel I

2010-08-01

This paper reports on the effects of environmental conditions and process parameters on flocculation of high dry matter (average DM of 7.3%) swine manure with cationic polymers with 10%, 35%, and 55% charge densities (CDs). Polymer solutions prepared with hard and distilled water allowed similar suspended solids (SS) reductions in the initial 24h. After 3-7 days at 20 degrees C, however, the efficiency of the hard water solutions started to decline, while the polymers made with distilled water maintained their performance for up to 10 days. The 10% CD polymer was considerably less affected than the 35% CD polymer by the age of the hard water solutions. During polymer injection, minimum velocity gradients (G) of 108 and 253 s(-1) were required to maximized efficiency of the 10% and 35% CD polymer, respectively. Flocculation mixing velocities up to 84 s(-1) and mixing times between 1 and 30 min had no effect on polymer efficiency. However, mixing at 22s(-1) for more than 30 min decreased SS reduction. Adding polymer in multiple injections did not improve the efficiency of medium and high CD polymers, and adversely affected that of the low CD polymer, maybe because of repeated rapid mixing cycles which ruptured the flocs. Polymer performance was not affected by operating temperature between 6 and 25 degrees C. These results were collected on a laboratory-scale apparatus and remain to be validated at larger scale. Crown Copyright 2010. Published by Elsevier Ltd. All rights reserved.

Intelligent fiber optic sensor for solution concentration examination

NASA Astrophysics Data System (ADS)

Borecki, Michal; Kruszewski, Jerzy

2003-09-01

This paper presents the working principles of intelligent fiber-optic intensity sensor used for solution concentration examination. The sensor head is the ending of the large core polymer optical fiber. The head works on the reflection intensity basis. The reflected signal level depends on Fresnel reflection and reflection on suspended matter when the head is submersed in solution. The sensor head is mounted on a lift. For detection purposes the signal includes head submerging, submersion, emerging and emergence is measured. This way the viscosity turbidity and refraction coefficient has an effect on measured signal. The signal forthcoming from head is processed electrically in opto-electronic interface. Then it is feed to neural network. The novelty of presented sensor is implementation of neural network that works in generalization mode. The sensor resolution depends on opto-electronic signal conversion precision and neural network learning accuracy. Therefore, the number and quality of points used for learning process is very important. The example sensor application for examination of liquid soap concentration in water is presented in the paper.

Flow-induced gelation of living (micellar) polymers

NASA Technical Reports Server (NTRS)

Bruinsma, Robijn; Gelbart, William M.; Ben-Shaul, Avinoam

1992-01-01

The effect of shear velocity gradients on the size (L) of rodlike micelles in dilute and semidilute solution is considered. A kinetic equation is introduced for the time-dependent concentration of aggregates of length L, consisting of 'bimolecular' combination processes L + L-prime yield (L + L-prime) and unimolecular fragmentations L yield L + (L - L-prime). The former are described by a generalization (from spheres to rods) of the Smoluchowski mechanism for shear-induced coalesence of emulsions, and the latter by incorporating the tension-deformation effects due to flow. Steady-state solutions to the kinetic equation are obtained, with the corresponding mean micellar size evaluated as a function of the Peclet number P (i.e., the dimensionless ratio of the flow rate and the rotational diffusion coefficient). For sufficiently dilute solutions, only a weak dependence of the micellar size on P is found. In the semidilute regime, however, an apparent divergence in the micellar size at P of about 1 suggests a flow-induced first-order gelation phenomenon.

Temperature Dependence of Field-Effect Mobility in Organic Thin-Film Transistors: Similarity to Inorganic Transistors.

PubMed

Okada, Jun; Nagase, Takashi; Kobayashi, Takashi; Naito, Hiroyoshi

2016-04-01

Carrier transport in solution-processed organic thin-film transistors (OTFTs) based on dioctylbenzothienobenzothiophene (C8-BTBT) has been investigated in a wide temperature range from 296 to 10 K. The field-effect mobility shows thermally activated behavior whose activation energy becomes smaller with decreasing temperature. The temperature dependence of field-effect mobility found in C8-BTBT is similar to that of others materials: organic semiconducting polymers, amorphous oxide semiconductors and hydrogenated amorphous silicon. These results indicate that hopping transport between isoenergetic localized states becomes dominated in a low temperature regime in these materials.

Drag reduction in the turbulent Kolmogorov flow.

PubMed

Boffetta, Guido; Celani, Antonio; Mazzino, Andrea

2005-03-01

We investigate the phenomenon of drag reduction in a viscoelastic fluid model of dilute polymer solutions. By means of direct numerical simulations of the three-dimensional turbulent Kolmogorov flow we show that drag reduction takes place above a critical Reynolds number Re(c). An explicit expression for the dependence of Re(c) on polymer elasticity and diffusivity is derived. The values of the drag coefficient obtained for different fluid parameters collapse onto a universal curve when plotted as a function of the rescaled Reynolds number Re/ Re(c). The analysis of the momentum budget allows us to gain some insight on the physics of drag reduction, and suggests the existence of a Re-independent value of the drag cofficient--lower than the Newtonian one--for large Reynolds numbers.

Shape-Controlled Fabrication of the Polymer-Based Micromotor Based on the Polydimethylsiloxane Template.

PubMed

Su, Miaoda; Liu, Mei; Liu, Limei; Sun, Yunyu; Li, Mingtong; Wang, Dalei; Zhang, Hui; Dong, Bin

2015-11-03

We report the utilization of the polydimethylsiloxane template to construct polymer-based autonomous micromotors with various structures. Solid or hollow micromotors, which consist of polycaprolactone and platinum nanoparticles, can be obtained with controllable sizes and shapes. The resulting micromotor can not only be self-propelled in solution based on the bubble propulsion mechanism in the presence of the hydrogen peroxide fuel, but also exhibit structure-dependent motion behavior. In addition, the micromotors can exhibit various functions, ranging from fluorescence, magnetic control to cargo transportation. Since the current method can be extended to a variety of organic and inorganic materials, we thus believe it may have great potential in the fabrication of different functional micromotors for diverse applications.

Effects of solvent density on retention in gas-liquid chromatography. I. Alkanes solutes in polyethylene glycol stationary phases.

PubMed

González, F R; Pérez-Parajón, J; García-Domínguez, J A

2002-04-12

Gas-liquid chromatographic columns were prepared coating silica capillaries with poly(oxyethylene) polymers of different molecular mass distributions, in the range of low number-average molar masses, where the density still varies significantly. A novel, high-temperature, rapid evaporation method was developed and applied to the static coating of the low-molecular-mass stationary phases. The analysis of alkanes retention data from these columns reveals that the dependence of the partition coefficient with the solvent macroscopic density is mainly due to a variation of entropy. Enthalpies of solute transfer contribute poorly to the observed variations of retention. Since the alkanes solubility diminishes with the increasing solvent density, and this variation is weakly dependent with temperature, it is concluded that the decrease of free-volume in the liquid is responsible for this behavior.

Sorption of Ochratoxin A from Aqueous Solutions Using β-Cyclodextrin-Polyurethane Polymer

PubMed Central

Appell, Michael; Jackson, Michael A.

2012-01-01

The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1–10 μg·L−1. These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples. PMID:22474569

Probe diffusion of labeled polymers inside polyacrylic acid solutions: A polyelectrolyte effect

NASA Astrophysics Data System (ADS)

Mishra, Banani; Mithra, K.; Khandai, Santripti; Jena, Sidhartha S.

2018-05-01

Probe diffusion of fluorescently labeled Dextran 40 inside polyelectrolyte solution of polyacrylic acid (PAA) was investigated using Fluorescence Recovery After Photobleaching technique. The crowding and interaction effects on probe diffusion were controlled by tuning background polymer and added external electrolyte concentration. For all the salt concentration, an overall decrease in diffusion coefficient is observed with rise in polymer concentration. The diffusion coefficient decreases with decrease in salt concentration whereas the solution viscosity increases, indicating a competition between viscous drag and electrostatic interaction. A large positive deviation from the ideal Stokes-Einstein relation is observed for high polymer and low salt concentration, which reduces markedly with addition of salt confirming polyelectrolyte effects, plays a major role in deciding the probe diffusion.

Charge-discharge characteristics of nickel/zinc battery with polymer hydrogel electrolyte

NASA Astrophysics Data System (ADS)

Iwakura, Chiaki; Murakami, Hiroki; Nohara, Shinji; Furukawa, Naoji; Inoue, Hiroshi

A new nickel/zinc (Ni/Zn) battery was assembled by using polymer hydrogel electrolyte prepared from cross-linked potassium poly(acrylate) and KOH aqueous solution, and its charge-discharge characteristics were investigated. The experimental Ni/Zn cell with the polymer hydrogel electrolyte exhibited well-defined charge-discharge curves and remarkably improved charge-discharge cycle performance, compared to that with a KOH aqueous solution. Moreover, it was found that dendritic growth hardly occurred on the zinc electrode surface during charge-discharge cycles in the polymer hydrogel electrolyte. These results indicate that the polymer hydrogel electrolyte can successfully be used in Ni/Zn batteries as an electrolyte with excellent performance.

Vacuum-integrated electrospray deposition for highly reliable polymer thin film.

PubMed

Park, Soohyung; Lee, Younjoo; Yi, Yeonjin

2012-10-01

Vacuum electrospray deposition (ESD) equipment was designed to prepare polymer thin films. The polymer solution can be injected directly into vacuum system through multi-stage pumping line, so that the solvent residues and ambient contaminants are highly reduced. To test the performance of ESD system, we fabricated organic photovoltaic cells (OPVCs) by injecting polymer solution directly onto the substrate inside a high vacuum chamber. The OPVC fabricated has the structure of Al∕P3HT:PCBM∕PEDOT:PSS∕ITO and was optimized by varying the speed of solution injection and concentration of the solution. The power conversion efficiency (PCE) of the optimized OPVC is 3.14% under AM 1.5G irradiation without any buffer layer at the cathode side. To test the advantages of the vacuum ESD, we exposed the device to atmosphere between the deposition steps of the active layer and cathode. This showed that the PCE of the vacuum processed device is 24% higher than that of the air exposed device and confirms the advantages of the vacuum prepared polymer film for high performance devices.

Enhanced photophysics of conjugated polymers

DOEpatents

Chen, Liaohai [Argonne, IL; Xu, Su [Santa Clara, CA; McBranch, Duncan [Santa Fe, NM; Whitten, David [Santa Fe, NM

2003-05-27

The addition of oppositely charged surfactant to fluorescent ionic conjugated polymer forms a polymer-surfactant complex that exhibits at least one improved photophysical property. The conjugated polymer is a fluorescent ionic polymer that typically has at least one ionic side chain or moiety that interacts with the specific surfactant selected. The photophysical property improvements may include increased fluorescence quantum efficiency, wavelength-independent emission and absorption spectra, and more stable fluorescence decay kinetics. The complexation typically occurs in a solution of a polar solvent in which the polymer and surfactant are soluble, but it may also occur in a mixture of solvents. The solution is commonly prepared with a surfactant molecule:monomer repeat unit of polymer ratio ranging from about 1:100 to about 1:1. A polymer-surfactant complex precipitate is formed as the ratio approaches 1:1. This precipitate is recoverable and usable in many forms.

Using in-situ polymerization of conductive polymers to enhance the electrical properties of solution-processed carbon nanotube films and fibers.

PubMed

Allen, Ranulfo; Pan, Lijia; Fuller, Gerald G; Bao, Zhenan

2014-07-09

Single-walled carbon nanotubes/polymer composites typically have limited conductivity due to a low concentration of nanotubes and the insulating nature of the polymers used. Here we combined a method to align carbon nanotubes with in-situ polymerization of conductive polymer to form composite films and fibers. Use of the conducting polymer raised the conductivity of the films by 2 orders of magnitude. On the other hand, CNT fiber formation was made possible with in-situ polymerization to provide more mechanical support to the CNTs from the formed conducting polymer. The carbon nanotube/conductive polymer composite films and fibers had conductivities of 3300 and 170 S/cm, respectively. The relatively high conductivities were attributed to the polymerization process, which doped both the SWNTs and the polymer. In-situ polymerization can be a promising solution-processable method to enhance the conductivity of carbon nanotube films and fibers.

Structure Formation in Solutions of Rigid Polymers Undergoing a Phase Transition

DTIC Science & Technology

1987-04-01

cyclohexene dioxide (ERL-4206) - 10 g. nonenyl succinic anhydride (NSA) - 26 g. dimethyl amino ethanol ( DMAE ) - 0.4 g. After infiltration, short segments...existence of a significant number of defects within the individual microfibril. The presence of defects in the lateral packing of PBT chains is also suggested...of the D- and L- enantiomers yields a nematic phase. The ordered phases exhi- bit complex textures due to defects (disclinations) which depend on

Conductivity of gel polymer electrolytes doped with solutions of phosphonic acid or protic ionic liquids

NASA Astrophysics Data System (ADS)

Shmukler, Liudmila E.; Fadeeva, Yuliya A.; Glushenkova, Ekaterina V.; Nguyen, Van Thuc; Safonova, Liubov P.

2018-04-01

The proton-conducting gel electrolytes (PCGEs) based on PMMA, PVdF or PVdF-HFP doped with solutions of phosphonic acid or ammonium based protic ionic liquids (PILs) in DMF have been synthesized. Rather high values of the conductivity (10-4-10-3 S cm-1) have been reached at low dopant concentrations (up to 1 mol l-1). The influence of the nature of both polymeric matrix and dopant as well as dopant concentration on the conductivity values was discussed. It was established that the dependence of conductivity on the nature of dopant, but not the polymeric matrix, was more pronounced.

Hydrophilization and hydrophobic recovery in polymers obtained by casting of polymer solutions on water surface.

PubMed

Bormashenko, Edward; Chaniel, Gilad; Gendelman, Oleg

2014-12-01

We demonstrate the possibility of hydrophilization of polymer films in situ under the process of their preparation. The polymer surface is hydrophilized when the polymer solution is spread on the water surface and the solvent is evaporated. Essential hydrophilization of the polymer surface is achieved under this process. We relate the observed hydrophilization of polymer films to the dipole-dipole interaction of the polar moieties of polymer chains with highly polar water molecules. The dipole-dipole interaction between water molecules and polar groups of polymer chains, orienting the polar groups of a polymer, may prevail over the London dispersion forces. The process, reported in the paper, allows to manufacture the films in which the hydrophilic moieties of the polymer molecule are oriented toward the polymer/air interface. It is demonstrated that even such traditionally extremely hydrophobic polymers as polydimethylsiloxane can be markedly hydrophilized. This hydrophilization, however, does not persist forever. After removal from the water surface, hydrophobic recovery was observed, i.e. polymer films restored their hydrophobicity with time. The characteristic time of the hydrophobic recovery is on the order of magnitude of hours. Copyright © 2014 Elsevier Inc. All rights reserved.

Comparison of solution-mixed and sequentially processed P3HT: F4TCNQ films: effect of doping-induced aggregation on film morphology

DOE PAGES

Jacobs, Ian E.; Aasen, Erik W.; Oliveira, Julia L.; ...

2016-03-23

Doping polymeric semiconductors often drastically reduces the solubility of the polymer, leading to difficulties in processing doped films. Here, we compare optical, electrical, and morphological properties of P3HT films doped with F4TCNQ, both from mixed solutions and using sequential solution processing with orthogonal solvents. We demonstrate that sequential doping occurs rapidly (<1 s), and that the film doping level can be precisely controlled by varying the concentration of the doping solution. Furthermore, the choice of sequential doping solvent controls whether dopant anions are included or excluded from polymer crystallites. Atomic force microscopy (AFM) reveals that sequential doping produces significantly moremore » uniform films on the nanoscale than the mixed-solution method. In addition, we show that mixed-solution doping induces the formation of aggregates even at low doping levels, resulting in drastic changes to film morphology. Sequentially coated films show 3–15 times higher conductivities at a given doping level than solution-doped films, with sequentially doped films processed to exclude dopant anions from polymer crystallites showing the highest conductivities. In conclusion, we propose a mechanism for doping induced aggregation in which the shift of the polymer HOMO level upon aggregation couples ionization and solvation energies. To show that the methodology is widely applicable, we demonstrate that several different polymer:dopant systems can be prepared by sequential doping.« less

Comparison of solution-mixed and sequentially processed P3HT: F4TCNQ films: effect of doping-induced aggregation on film morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Ian E.; Aasen, Erik W.; Oliveira, Julia L.

Doping polymeric semiconductors often drastically reduces the solubility of the polymer, leading to difficulties in processing doped films. Here, we compare optical, electrical, and morphological properties of P3HT films doped with F4TCNQ, both from mixed solutions and using sequential solution processing with orthogonal solvents. We demonstrate that sequential doping occurs rapidly (<1 s), and that the film doping level can be precisely controlled by varying the concentration of the doping solution. Furthermore, the choice of sequential doping solvent controls whether dopant anions are included or excluded from polymer crystallites. Atomic force microscopy (AFM) reveals that sequential doping produces significantly moremore » uniform films on the nanoscale than the mixed-solution method. In addition, we show that mixed-solution doping induces the formation of aggregates even at low doping levels, resulting in drastic changes to film morphology. Sequentially coated films show 3–15 times higher conductivities at a given doping level than solution-doped films, with sequentially doped films processed to exclude dopant anions from polymer crystallites showing the highest conductivities. In conclusion, we propose a mechanism for doping induced aggregation in which the shift of the polymer HOMO level upon aggregation couples ionization and solvation energies. To show that the methodology is widely applicable, we demonstrate that several different polymer:dopant systems can be prepared by sequential doping.« less

In situ polymerization of monomers for polyphenylquinoxaline/graphite fiber composites

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D.

1974-01-01

Methods currently used to prepare fiber reinforced, high temperature resistant polyphenylquinoxaline (PPQ) composites employ extremely viscous, low solids content solutions of high molecular weight PPQ polymers. An improved approach, described in this report, consists of impregnating the fiber with a solution of the appropriate monomers instead of a solution of previously synthesized high molecular weight polymer. Polymerization of the monomers occurs in situ on the fiber during the solvent removal and curing stages. The in situ polymerization approach greatly simplifies the fabrication of PPQ graphite fiber composites. The use of low viscosity monomeric type solutions facilitates fiber wetting, permits a high solids content, and eliminates the need for prior polymer synthesis.

Making molecular balloons in laser-induced explosive boiling of polymer solutions.

PubMed

Leveugle, Elodie; Sellinger, Aaron; Fitz-Gerald, James M; Zhigilei, Leonid V

2007-05-25

The effect of the dynamic molecular rearrangements leading to compositional segregation is revealed in coarse-grained molecular dynamics simulations of short pulse laser interaction with a polymer solution in a volatile matrix. An internal release of matrix vapor at the onset of the explosive boiling of the overheated liquid is capable of pushing polymer molecules to the outskirts of a transient bubble, forming a polymer-rich surface layer enclosing the volatile matrix material. The results explain unexpected "deflated balloon" structures observed in films deposited by the matrix-assisted pulsed laser evaporation technique.

A Polymer "Pollution Solution" Classroom Activity.

ERIC Educational Resources Information Center

Helser, Terry L.

1996-01-01

Explains an approach to presenting polymer chemistry to nonmajors that employs polystyrene foam, foam peanuts made from water soluble starch, and water soluble plastic bags. Students are presented with a pollution scenario and are guided to the discovery of solutions. (DDR)

Solution of magnetohydrodynamic flow and heat transfer of radiative viscoelastic fluid with temperature dependent viscosity in wire coating analysis

PubMed Central

Khan, Muhammad Altaf; Siddiqui, Nasir; Ullah, Murad; Shah, Qayyum

2018-01-01

Wire coating process is a continuous extrusion process for primary insulation of conducting wires with molten polymers for mechanical strength and protection in aggressive environments. In the present study, radiative melt polymer satisfying third grade fluid model is used for wire coating process. The effect of magnetic parameter, thermal radiation parameter and temperature dependent viscosity on wire coating analysis has been investigated. Reynolds model and Vogel’s models have been incorporated for variable viscosity. The governing equations characterizing the flow and heat transfer phenomena are solved analytically by utilizing homotopy analysis method (HAM). The computed results are also verified by ND-Solve method (Numerical technique) and Adomian Decomposition Method (ADM). The effect of pertinent parameters is shown graphically. In addition, the instability of the flow in the flows of the wall of the extrusion die is well marked in the case of the Vogel model as pointed by Nhan-Phan-Thien. PMID:29596448

Lysozyme adsorption in pH-responsive hydrogel thin-films: the non-trivial role of acid-base equilibrium.

PubMed

Narambuena, Claudio F; Longo, Gabriel S; Szleifer, Igal

2015-09-07

We develop and apply a molecular theory to study the adsorption of lysozyme on weak polyacid hydrogel films. The theory explicitly accounts for the conformation of the network, the structure of the proteins, the size and shape of all the molecular species, their interactions as well as the chemical equilibrium of each titratable unit of both the protein and the polymer network. The driving forces for adsorption are the electrostatic attractions between the negatively charged network and the positively charged protein. The adsorption is a non-monotonic function of the solution pH, with a maximum in the region between pH 8 and 9 depending on the salt concentration of the solution. The non-monotonic adsorption is the result of increasing negative charge of the network with pH, while the positive charge of the protein decreases. At low pH the network is roughly electroneutral, while at sufficiently high pH the protein is negatively charged. Upon adsorption, the acid-base equilibrium of the different amino acids of the protein shifts in a nontrivial fashion that depends critically on the particular kind of residue and solution composition. Thus, the proteins regulate their charge and enhance adsorption under a wide range of conditions. In particular, adsorption is predicted above the protein isoelectric point where both the solution lysozyme and the polymer network are negatively charged. This behavior occurs because the pH in the interior of the gel is significantly lower than that in the bulk solution and it is also regulated by the adsorption of the protein in order to optimize protein-gel interactions. Under high pH conditions we predict that the protein changes its charge from negative in the solution to positive within the gel. The change occurs within a few nanometers at the interface of the hydrogel film. Our predictions show the non-trivial interplay between acid-base equilibrium, physical interactions and molecular organization under nanoconfined conditions, which leads to non-trivial adsorption behavior that is qualitatively different from what would be predicted from the state of the proteins in the bulk solution.

Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

2000-01-01

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Modeling and simulations of carbon nanotube (CNT) dispersion in water/surfactant/polymer systems

NASA Astrophysics Data System (ADS)

Uddin, Nasir Mohammad

An innovative multiscale (atomistic to mesoscale) model capable of predicting carbon nanotube (CNT) interactions and dispersion in water/surfactant/polymer systems was developed. The model was verified qualitatively with available experimental data in the literature. It can be used to computationally screen potential surfactants, solvents, polymers, and CNT with appropriate diameter and length to obtain improved CNT dispersion in aqueous medium. Thus the model would facilitate the reduction of time and cost required to produce CNT dispersed homogeneous solutions and CNT reinforced materials. CNT dispersion in any water/surfactant/polymer system depends on interactions between CNTs and surrounding molecules. Central to the study was the atomistic scale model which used the atomic structure of the surfactant, solvent, polymer, and CNT. The model was capable of predicting the CNT interactions in terms of potential of mean force (PMF) between CNTs under the influence of surrounding molecules in an aqueous solution. On the atomistic scale, molecular dynamics method was used to compute the PMF as a function of CNT separation and CNT alignment. An adaptive biasing force (ABF) method was used to speed up the calculations. Correlations were developed to determine the effective interactions between CNTs as a function of their any inter-atomic distance and orientation angle in water as well as in water/surfactant by fitting the calculated PMF data. On the mesoscale, the fitted PMF correlations were used as input in the Monte Carlo simulations to determine the degree of dispersion of CNTs in water and water/surfactant system. The distribution of CNT cluster size was determined for the CNTs dispersed in water with and without surfactant addition. The entropie and enthalpie contributions to the CNT interactions in water were determined to understand the dispersion mechanism of CNTs in water. The effects of CNT orientation, length, diameter, chirality and surfactant concentrations and structures on CNT interactions in water were investigated at room conditions. CNT interactions in polymer solution were also investigated with polyethylene oxide (PEO) polymer and water as a solvent. In all cases, the atomic arrangement of molecules was discussed in detailed. Simulations revealed that CNT orientation, length, diameter, and addition of surfactant and its structures can significantly affect CNT interactions (i.e., PMFs varied significantly) and in-turn the degree of CNT dispersion in aqueous solution. For all simulation cases, a uniform sampling was achieved by using the ABF method to calculate the governing PMF between CNTs indicating the effectiveness and convergence of the adaptive sampling scheme. The surfactant molecules were shown to adsorb at the CNT surface and contribute to weaker interactions between CNTs which resulted less CNT aggregate size at the mesoscale. Surfactant consisting with a benzene ring contributed much weaker interactions between CNTs as compared with that of without benzene ring. The increase in CNT length contributed the stronger CNT interactions where the increase in CNT diameter caused weaker CNT interactions in water. The interfacial characteristics between the CNT, surfactant and the polymer were also predicted and discussed. The model can be expanded for more solvents, surfactants, and polymers.

Polymer flexibility and turbulent drag reduction.

PubMed

Gillissen, J J J

2008-10-01

Polymer-induced drag reduction is the phenomenon by which the friction factor of a turbulent flow is reduced by the addition of small amounts of high-molecular-weight linear polymers, which conformation in solution at rest can vary between randomly coiled and rodlike. It is well known that drag reduction is positively correlated to viscous stresses, which are generated by extended polymers. Rodlike polymers always assume this favorable conformation, while randomly coiling chains need to be unraveled by fluid strain rate in order to become effective. The coiling and stretching of flexible polymers in turbulent flow produce an additional elastic component in the polymer stress. The effect of the elastic stresses on drag reduction is unclear. To study this issue, we compare direct numerical simulations of turbulent drag reduction in channel flow using constitutive equations describing solutions of rigid and flexible polymers. When compared at constant phi r2, both simulations predict the same amount of drag reduction. Here phi is the polymer volume fraction and r is the polymer aspect ratio, which for flexible polymers is based on average polymer extension at the channel wall. This demonstrates that polymer elasticity plays a marginal role in the mechanism for drag reduction.

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results inmore » highly aligned, highly crystalline donor-acceptor polymer thin films over large area (41cm 2) and promoted charge transport along both the polymer backbone and the π-π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment.« less

Effects of Alkylthio and Alkoxy Side Chains in Polymer Donor Materials for Organic Solar Cells.

PubMed

Cui, Chaohua; Wong, Wai-Yeung

2016-02-01

Side chains play a considerable role not only in improving the solubility of polymers for solution-processed device fabrication, but also in affecting the molecular packing, electron affinity and thus the device performance. In particular, electron-donating side chains show unique properties when employed to tune the electronic character of conjugated polymers in many cases. Therefore, rational electron-donating side chain engineering can improve the photovoltaic properties of the resulting polymer donors to some extent. Here, a survey of some representative examples which use electron-donating alkylthio and alkoxy side chains in conjugated organic polymers for polymer solar cell applications will be presented. It is envisioned that an analysis of the effect of such electron-donating side chains in polymer donors would contribute to a better understanding of this kind of side chain behavior in solution-processed conjugated organic polymers for polymer solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

PubMed Central

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei; Qu, Ge; Zhang, Fengjiao; Zhao, Xikang; Mei, Jianguo; Zuo, Jian-Min; Shukla, Diwakar; Diao, Ying

2017-01-01

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results in highly aligned, highly crystalline donor–acceptor polymer thin films over large area (>1 cm2) and promoted charge transport along both the polymer backbone and the π–π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment. PMID:28703136

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

DOE PAGES

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei; ...

2017-07-13

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results inmore » highly aligned, highly crystalline donor-acceptor polymer thin films over large area (41cm 2) and promoted charge transport along both the polymer backbone and the π-π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment.« less

Packaging of Polyelectrolytes in Viral Capsids: The Interplay Between Polymer Length and Capsid Size

NASA Astrophysics Data System (ADS)

Knobler, Charles

2008-03-01

Each particle of the Cowpea Chlorotic Mottle Virus (CCMV) has a very small ``parts list,'' consisting of two components: a molecule of single-stranded RNA and a 190-residue protein that makes up the 28-nm diameter icosahedral capsid. When purified viral RNA and capsid protein are mixed in solution at an appropriate pH and ionic strength, infectious wild-type viruses form spontaneously. Virus-like particles (VLPs) are formed when the protein self assembles around other anionic polymers such as poly(styrene sulfonate) (PSS). Under different pH and ionic strength conditions the capsid protein can assemble by itself into empty capsids, multishell structures, tubes and sheets. To explore the effect on virion size of the competition between the preferred curvature of the protein and the size of the packaged cargo we have examined the formation of VLPs around PSS polymers with molecular weights ranging from 400 kDa to 3.4 MDa. Two distinct sizes are observed -- 22 nm for the lower molecular weights, jumping to 27 nm at 2 MDa. While under given conditions the size of PSS in solution is directly determined by its molecular weight, the self-complementarity of RNA makes its solution structure dependent on the nucleotide sequence as well. We have therefore employed Small-Angle X-ray Scattering and Fluorescence Correlation Spectroscopy to examine the sizes of viral and non-viral RNAs of identical lengths. A model for the assembly that includes both the self-interactions of the polyelectrolyte and the capsid proteins and the interactions between them provides insight into the experimental results.

Liquid filament instability due to stretch-induced phase separation in polymer solutions

NASA Astrophysics Data System (ADS)

Arinstein, Arkadii; Kulichikhin, Valery; Malkin, Alexander; Technion-Israel Institute of Technology Collaboration; Institute of Petrochemical Synthesis, Russian Academy of Sciences Team

2015-03-01

The instability in a jet of a viscoelastic semi-dilute entangled polymer solution under high stretching is discussed. Initially, the variation in osmotic pressure can compensate for decrease in the capillary force, and the jet is stable. The further evolution of the polymer solution along the jet results in formation of a filament in the jet center and of a near-surface solvent layer. Such a redistribution of polymer seems like a ``phase separation'', but it is related to stretching of the jet. The viscous liquid shell demonstrates Raleigh-type instability resulting in the formation of individual droplets on the oriented filament. Experimental observations showed that this separation is starting during few first seconds, and continues of about 10 -15 seconds. The modeling shows that a jet stretching results in a radial gradient in the polymer distribution: the polymer is concentrated in the jet center, whereas the solvent is remaining near the surface. The key point of this model is that a large longitudinal stretching of a polymer network results in its lateral contraction, so a solvent is pressed out of this polymer network because of the decrease in its volume. V.K. and A.M. acknowledge the financial support of the Russian Scientific Foundation (Grant 4-23-00003).

Significant Enhancement in the Thermoelectric Properties of PEDOT:PSS Films through a Treatment with Organic Solutions of Inorganic Salts.

PubMed

Fan, Zeng; Du, Donghe; Yu, Zhimeng; Li, Pengcheng; Xia, Yijie; Ouyang, Jianyong

2016-09-07

Conducting polymers have promising thermoelectric application because they have many advantages including abundant elements, mechanical flexibility, and nontoxicity. The thermoelectric properties of conducting polymers strongly depend on their chemical structure and microstructure. Here, we report a novel and facile method to significantly enhance the thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) films through a treatment with organic solutions of inorganic salts. N,N-Dimethylformamide (DMF) and a common inorganic salt like zinc chloride (ZnCl2) are used as the solvent and solute of the solutions, respectively. The treatments can significantly increase both the Seebeck coefficient and electrical conductivity of the PSS films. The thermoelectric properties of the PSS films are sensitive to the experimental conditions, such as the salt concentration, treatment temperature, and the cation of the salts. After treatment at the optimal experimental conditions, the PSS films can exhibit a Seebeck coefficient of 26.1 μV/K and an electrical conductivity of over 1400 S/cm at room temperature. The corresponding power factor is 98.2 μW/(m·K(2)). The mechanism for the enhancement in the thermoelectric properties is attributed to the segregation of some PSSH chains from PSS and the conformation change of PEDOT chains as a result of the synergetic effects of inorganic salts and DMF.

STIMULI-RESPONSIVE POLYMERS WITH ENHANCED EFFICIENCY IN RESERVOIR RECOVERY PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles McCormick; Roger Hester

This sixth and final progress report for DOE Award Number DE-FC26-01BC15317 describes research during the period March 01, 2004 through August 31, 2004 performed at the University of Southern Mississippi on ''Stimuli Responsive Polymers with Enhanced Efficiency in Reservoir Recovery'' processes. Significantly, terpolymers that are responsive to changes in pH and ionic strength have been synthesized, characterized, and their solution properties have been extensively examined. Terpolymers composed of acrylamide, a carboxylated acrylamido monomer (AMBA), and a quaternary ammonium monomer (AMBATAC) with balanced compositions of the latter two, exhibit increases in aqueous solution viscosity as NaCl concentration is increased. This increasemore » in polymer coil size can be expected upon injection of this type of polymer into oil reservoirs of moderate-to-high salinity, leading to better mobility control. The opposite effect (loss of viscosity) is observed for conventional polymer systems. Additionally polymer mobility characteristics have been conducted for a number of hydrophilic copolymers utilizing an extensional flow apparatus and size exclusion chromatography. This study reveled that oil recovery enhancement through use of polymers in a water flood is due to the polymer's resistance to deformation as it flows through the reservoir. Individual polymers when in aqueous solution form coils. The larger the polymer's coil size, the greater the polymer's resistance to extensional flow and the more effective the polymer is in enhancing oil recovery. Large coil sizes are obtained by increasing the polymer molecular weight and having macromolecular structures that favor greater swelling of the coil by the aqueous solvent conditions (temperature, pH and electrolyte concentration) existing in the reservoir.« less

High-Reynolds-number turbulent-boundary-layer wall-pressure fluctuations with dilute polymer solutions

NASA Astrophysics Data System (ADS)

Elbing, Brian R.; Winkel, Eric S.; Ceccio, Steven L.; Perlin, Marc; Dowling, David R.

2010-08-01

Wall-pressure fluctuations were investigated within a high-Reynolds-number turbulent boundary layer (TBL) modified by the addition of dilute friction-drag-reducing polymer solutions. The experiment was conducted at the U.S. Navy's Large Cavitation Channel on a 12.9 m long flat-plate test model with the surface hydraulically smooth (k+<0.2) and achieving downstream-distance-based Reynolds numbers to 220×106. The polymer (polyethylene oxide) solution was injected into the TBL through a slot in the surface. The primary flow diagnostics were skin-friction drag balances and an array of flush-mounted dynamic pressure transducers 9.8 m from the model leading edge. Parameters varied included the free-stream speed (6.7, 13.4, and 20.2 m s-1) and the injection condition (polymer molecular weight, injection concentration, and volumetric injection flux). The behavior of the pressure spectra, convection velocity, and coherence, regardless of the injection condition, were determined primarily based on the level of drag reduction. Results were divided into two regimes dependent on the level of polymer drag reduction (PDR), nominally separated at a PDR of 40%. The low-PDR regime is characterized by decreasing mean-square pressure fluctuations and increasing convection velocity with increasing drag reduction. This shows that the decrease in the pressure spectra with increasing drag reduction is due in part to the moving of the turbulent structures from the wall. Conversely, with further increases in drag reduction, the high-PDR regime has negligible variation in the mean-squared pressure fluctuations and convection velocity. The convection velocity remains constant at approximately 10% above the baseline-flow convection velocity, which suggests that the turbulent structures no longer move farther from the wall with increasing drag reduction. In light of recent numerical work, the coherence results indicate that in the low-PDR regime, the turbulent structures are being elongated in the streamwise direction and occurring at decreasing frequency. In the high-PDR regime, the rate of occurrence continues to decrease until large-scale coherent turbulent structures are potentially no longer present.

Preparation of polymer-blended quinine nanocomposite particles by spray drying and assessment of their instrumental bitterness-masking effect using a taste sensor.

PubMed

Taki, Moeko; Tagami, Tatsuaki; Ozeki, Tetsuya

2017-05-01

The development of taste-masking technologies for foods and drugs is essential because it would enable people to consume and receive healthy and therapeutic effect without distress. In the current study, in order to develop a novel method to prepare nanocomposite particles (microparticles containing bitter nanoparticles) in only one step, by using spray drying, a two-solution mixing nozzle-equipped spray dryer that we previously reported was used. The nanocomposite particles with or without poorly water-soluble polymers prepared using our spray-drying technique were characterized. (1) The organic solution containing quinine, a model of bitter compound and poorly water-soluble polymers and (2) sugar alcohol (mannitol) aqueous solution were separately flown in tubes and two solutions were spray dried through two-solution type spray nozzle to prepare polymer-blended quinine nanocomposite particles. Mean diameters of nanoparticles, taste-masking effect and dissolution rate of quinine were evaluated. The results of taste masking by taste sensor suggested that the polymer (Eudragit EPO, Eudragit S100 or Ethyl cellulose)-blended quinine nanocomposite particles exhibited marked masking of instrumental quinine bitterness compared with the quinine nanocomposite particles alone. Quinine nanocomposite formulations altered the quinine dissolution rate, indicating that they can control intestinal absorption of quinine. These results suggest that polymer-blended quinine composite particles prepared using our spray-drying technique are useful for masking bitter tastes in the field of food and pharmaceutical industry.

Synthesis and characterization of a molecularly imprinted polymer for the isolation of the 16 US-EPA priority polycyclic aromatic hydrocarbons (PAHs) in solution.

PubMed

Ncube, Somandla; Kunene, Phumlile; Tavengwa, Nikita T; Tutu, Hlanganani; Richards, Heidi; Cukrowska, Ewa; Chimuka, Luke

2017-09-01

A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted polymers mixed at 1:1 (w/w) was successfully screened from several cavity-tuning experiments and used in the isolation of polycyclic aromatic hydrocarbons from spiked solution. The polymer mixture showed high cross selectivity and affinity towards all the 16 US-EPA priority polycyclic aromatic hydrocarbons. The average extraction efficiency from a cyclohexane solution was 65 ± 13.3% (n = 16, SD). Batch adsorption and kinetic studies confirmed that the binding of polycyclic aromatic hydrocarbons onto the polymer particles resulted in formation of a monolayer and that the binding process was the rate limiting step. The imprinted polymer performance studies confirmed that the synthesized polymer had an imprinting efficiency of 103.9 ± 3.91% (n = 3, SD). A comparison of the theoretical number of cavities and the experimental binding capacity showed that the overall extent of occupation of the imprinted cavities in the presence of excess polycyclic aromatic hydrocarbons was 128 ± 6.45% (n = 3, SD). The loss of selectivity was estimated at 2.9% with every elution cycle indicating that the polymer can be re-used several times with limited loss of selectivity and sensitivity. The polymer combination has shown to be an effective adsorbent that can be used to isolate all the 16 US-EPA priority polycyclic aromatic hydrocarbons in solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Controlling morphology and chain aggregation in semiconducting conjugated polymers: the role of solvent on optical gain in MEH-PPV.

PubMed

Lampert, Zach E; Reynolds, C Lewis; Papanikolas, John M; Aboelfotoh, M Osama

2012-10-25

We report the results of a detailed investigation that addresses the influence of polymer morphology and chain aggregation, as controlled by the chemical nature of the solvent, on the optical gain properties of the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV). Using the variable stripe length technique in the picosecond regime, we have extensively studied the optical gain performance of asymmetric planar waveguides formed with thin MEH-PPV films spin-cast from concentrated chlorobenzene (CB) and tetrahydrofuran (THF) solutions onto thermally oxidized silicon substrates. CB and THF solvents were chosen based on their known ability to promote and effectively limit aggregate formation, respectively. Very large net gain coefficients are demonstrated, reaching values of 330 and 365 cm(-1), respectively, when optically pumping the waveguides with a maximum energy density of 85 μJ/cm(2). Our results clearly demonstrate that polymer morphology, and hence, the chain conformation dependence of the degree of aggregation in the films as controlled by the solvent, has minimal impact on the net gain. Moreover, the waveguides exhibit low loss coefficients of 10-20 cm(-1) at the ASE wavelength. These results question the importance of polymer morphology and aggregate formation in polymer-based optical devices operating at high excitation densities in the stimulated emission regime as would be characteristic of lasers and optical amplifiers.

Features of microbiological behavior and biocide properties of electrosynthesized polymethylolacrylamide films

NASA Astrophysics Data System (ADS)

Kolzunova, Lidia G.

2016-05-01

The biocide properties of an electrosynthesized of acrylamide, N,N'-methylene-bis-acrylamide and formaldehyde copolymer films against the Staphylococcus aureus and bacterial association extracted from seawater (marine biological organisms) were investigated. Copolymer films were stable in organic solvents, acids and alkali and insoluble in water, though capable to swelling ability. Besides, the polymer is thermally stable up to 237°C. It was established that the anti-bacterial effect of the films started to be expressed after two days and was maintained from 2 up to 45 days. It was established that the degree of polymer films toxicity depended on the polymer synthesis conditions, pre-treatment method and duration of the biological object exposure to the effect. It was shown that antiseptic properties of the polymer material under study were imparted by formaldehyde both as sorbed by the polymer and as included into the copolymer composition. The toxicological effect of the polymethylolacrylamide films under study on microorganisms can be applied as in medicine (antiseptic materials and implants) as for equipment protection from bio-fouling and bio-corrosion. Microbiological stability and sterilizing effect of electrosynthesized polymethylolacrylamide ultrafiltration membranes enables one not only to prolong the operation time of film membranes, but also to provide partial sterilization of organic solutions to be filtered. It was established that polymer waste can be utilized by means of microbial destruction. It was found that the washed out polymer induced a specific bacteria behavior consisting of a complex of reactions directed to search, capture and consume nutrients.

Impact of solvents and supercritical CO2 drying on the morphology and structure of polymer-based biofilms

NASA Astrophysics Data System (ADS)

Causa, Andrea; Salerno, Aurelio; Domingo, Concepción; Acierno, Domenico; Filippone, Giovanni

2014-05-01

In the present work, two-dimensional systems based on biodegradable polymers such as poly(ɛ-caprolactone) (PCL), poly(ethylene oxide) (PEO) and polylactic acid (PLA) are fabricated by means of a sustainable approach which consists in inducing phase separation in solutions of such polymers and "green" solvents, namely ethyl lactate (EL) and ethyl acetate (EA). The extraction of the solvent is promoted by a controlled drying process, which is performed in either air or supercritical CO2. The latter can indeed act as both an antisolvent, which favors the deposition of the polymer by forming a mixture with EL and EA, and a plasticizing agent, whose solvation and transport properties may considerably affect the microstructure and crystallinity of the polymer films. The morphological, topographical and crystalline properties of the films are tailored through a judicial selection of the materials and the processing conditions and assessed by means of thermal analyses, polarized optical microscopy, scanning electron microscopy and confocal interferometric microscopy. The results show that the morphological and crystalline properties of the films are strongly dependent on the choice of both the polymer/solvent system and the operating conditions during the drying step. In particular, the morphological, topographical and thermal properties of films prepared starting from highly crystalline polymers, namely PCL and PEO, are greatly affected by the crystallization of the material. Conversely, the less crystalline PLA forms almost completely amorphous films.

Flexible transparent displays based on core/shell upconversion nanophosphor-incorporated polymer waveguides

PubMed Central

Park, Bong Je; Hong, A-Ra; Park, Suntak; Kyung, Ki-Uk; Lee, Kwangyeol; Seong Jang, Ho

2017-01-01

Core/shell (C/S)-structured upconversion nanophosphor (UCNP)-incorporated polymer waveguide-based flexible transparent displays are demonstrated. Bright green- and blue-emitting Li(Gd,Y)F4:Yb,Er and Li(Gd,Y)F4:Yb,Tm UCNPs are synthesized via solution chemical route. Their upconversion luminescence (UCL) intensities are enhanced by the formation of C/S structure with LiYF4 shell. The Li(Gd,Y)F4:Yb,Er/LiYF4 and Li(Gd,Y)F4:Yb,Tm/LiYF4 C/S UCNPs exhibit 3.3 and 2.0 times higher UCL intensities than core counterparts, respectively. In addition, NaGdF4:Yb,Tm/NaGdF4:Eu C/S UCNPs are synthesized and they show red emission via energy transfer and migration of Yb3+ → Tm3+ → Gd3+ → Eu3+. The C/S UCNPs are incorporated into bisphenol A ethoxylate diacrylate which is used as a core material of polymer waveguides. The fabricated stripe-type polymer waveguides are highly flexible and transparent (transmittance > 90% in spectral range of 443–900 nm). The polymer waveguides exhibit bright blue, green, and red luminescence, depending on the incorporated UCNPs into the polymer core, under coupling with a near infrared (NIR) laser. Moreover, patterned polymer waveguide-based display devices are fabricated by reactive ion etching process and they realize bright blue-, green-, and red-colored characters under coupling with an NIR laser. PMID:28368021

Switching from Controlled Ring-Opening Polymerization (cROP) to Controlled Ring-Closing Depolymerization (cRCDP) by Adjusting the Reaction Parameters That Determine the Ceiling Temperature

PubMed Central

2016-01-01

Full control over the ceiling temperature (Tc) enables a selective transition between the monomeric and polymeric state. This is exemplified by the conversion of the monomer 2-allyloxymethyl-2-ethyl-trimethylene carbonate (AOMEC) to poly(AOMEC) and back to AOMEC within 10 h by controlling the reaction from conditions that favor ring-opening polymerization (Tc > T0) (where T0 is the reaction temperature) to conditions that favor ring-closing depolymerization (Tc < T0). The ring-closing depolymerization (RCDP) mirrors the polymerization behavior with a clear relation between the monomer concentration and the molecular weight of the polymer, indicating that RCDP occurs at the chain end. The Tc of the polymerization system is highly dependent on the nature of the solvent, for example, in toluene, the Tc of AOMEC is 234 °C and in acetonitrile Tc = 142 °C at the same initial monomer concentration of 2 M. The control over the monomer to polymer equilibrium sets new standards for the selective degradation of polymers, the controlled release of active components, monomer synthesis and material recycling. In particular, the knowledge of the monomer to polymer equilibrium of polymers in solution under selected environmental conditions is of paramount importance for in vivo applications, where the polymer chain is subjected to both high dilution and a high polarity medium in the presence of catalysts, that is, very different conditions from which the polymer was formed. PMID:27783494

Flexible transparent displays based on core/shell upconversion nanophosphor-incorporated polymer waveguides

NASA Astrophysics Data System (ADS)

Park, Bong Je; Hong, A.-Ra; Park, Suntak; Kyung, Ki-Uk; Lee, Kwangyeol; Seong Jang, Ho

2017-04-01

Core/shell (C/S)-structured upconversion nanophosphor (UCNP)-incorporated polymer waveguide-based flexible transparent displays are demonstrated. Bright green- and blue-emitting Li(Gd,Y)F4:Yb,Er and Li(Gd,Y)F4:Yb,Tm UCNPs are synthesized via solution chemical route. Their upconversion luminescence (UCL) intensities are enhanced by the formation of C/S structure with LiYF4 shell. The Li(Gd,Y)F4:Yb,Er/LiYF4 and Li(Gd,Y)F4:Yb,Tm/LiYF4 C/S UCNPs exhibit 3.3 and 2.0 times higher UCL intensities than core counterparts, respectively. In addition, NaGdF4:Yb,Tm/NaGdF4:Eu C/S UCNPs are synthesized and they show red emission via energy transfer and migration of Yb3+ → Tm3+ → Gd3+ → Eu3+. The C/S UCNPs are incorporated into bisphenol A ethoxylate diacrylate which is used as a core material of polymer waveguides. The fabricated stripe-type polymer waveguides are highly flexible and transparent (transmittance > 90% in spectral range of 443-900 nm). The polymer waveguides exhibit bright blue, green, and red luminescence, depending on the incorporated UCNPs into the polymer core, under coupling with a near infrared (NIR) laser. Moreover, patterned polymer waveguide-based display devices are fabricated by reactive ion etching process and they realize bright blue-, green-, and red-colored characters under coupling with an NIR laser.

Adjustable flow rate controller for polymer solutions

DOEpatents

Jackson, Kenneth M.

1981-01-01

An adjustable device for controlling the flow rate of polymer solutions which results in only little shearing of the polymer molecules, said device comprising an inlet manifold, an outlet manifold, a plurality of tubes capable of providing communication between said inlet and outlet manifolds, said tubes each having an internal diameter that is smaller than that of the inlet manifold and large enough to insure that viscosity of the polymer solution passing through each said tube will not be reduced more than about 25 percent, and a valve associated with each tube, said valve being capable of opening or closing communication in that tube between the inlet and outlet manifolds, each said valve when fully open having a diameter that is substantially at least as great as that of the tube with which it is associated.

Piling-to-buckling transition in the drying process of polymer solution drop on substrate having a large contact angle.

PubMed

Kajiya, Tadashi; Nishitani, Eisuke; Yamaue, Tatsuya; Doi, Masao

2006-01-01

We studied the drying process of polymer solution drops placed on a substrate having a large contact angle with the drop. The drying process takes place in three stages. First, the droplet evaporates keeping the contact line fixed. Second, the droplet shrinks uniformly with receding contact line. Finally the contact line is pinned again, and the droplet starts to be deformed. The shape of the final polymer deposit changes from concave dot, to flat dot, and then to concave dot again with the increase of the initial polymer concentration. This shape change is caused by the gradual transition from the solute piling mechanism proposed by Deegan to the crust buckling mechanism proposed by de Gennes and Pauchard.

Nonlinear dynamics that appears in the dynamical model of drying process of a polymer solution coated on a flat substrate

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2007-01-01

We have proposed and modified the dynamical model of drying process of polymer solution coated on a flat substrate for flat polymer film fabrication and have presented the fruits through some meetings and so on. Though basic equations of the dynamical model have characteristic nonlinearity, character of the nonlinearity has not been studied enough yet. In this paper, at first, we derive nonlinear equations from the dynamical model of drying process of polymer solution. Then we introduce results of numerical simulations of the nonlinear equations and consider roles of various parameters. Some of them are indirectly concerned in strength of non-equilibriumity. Through this study, we approach essential qualities of nonlinearity in non-equilibrium process of drying process.

Method of cross-linking polyvinyl alcohol and other water soluble resins

NASA Technical Reports Server (NTRS)

Phillipp, W. H.; May, C. E.; Hsu, L. C.; Sheibley, D. W. (Inventor)

1980-01-01

A self supporting sheet structure comprising a water soluble, noncrosslinked polymer such as polyvinyl alcohol which is capable of being crosslinked by reaction with hydrogen atom radicals and hydroxyl molecule radicals is contacted with an aqueous solution having a pH of less than 8 and containing a dissolved salt in an amount sufficient to prevent substantial dissolution of the noncrosslinked polymer in the aqueous solution. The aqueous solution is then irradiated with ionizing radiation to form hydrogen atom radicals and hydroxyl molecule radicals and the irradiation is continued for a time sufficient to effect crosslinking of the water soluble polymer to produce a water insoluble polymer sheet structure. The method has particular application in the production of battery separators and electrode envelopes for alkaline batteries.

Inorganic-polymer-derived dielectric films

DOEpatents

Brinker, C. Jeffrey; Keefer, Keith D.; Lenahan, Patrick M.

1987-01-01

A method of coating a substrate with a thin film of a polymer of predetermined porosity comprises depositing the thin film on the substrate from a non-gelled solution comprising at least one hydrolyzable metal alkoxide of a polymeric network forming cation, water, an alcohol compatible with the hydrolysis and the polymerization of the metal alkoxide, and an acid or a base, prior to depositing the film, controlling the structure of the polymer for a given composition of the solution exclusive of the acid or base component and the water component, (a) by adjusting each of the water content, the pH, and the temperature to obtain the desired concentration of alkoxide, and then adjusting the time of standing of the solution prior to lowering the temperature of the solution, and (b) lowering the temperature of the solution after the time of standing to about 15 degrees C. or lower to trap the solution in a state in which, after the depositing step, a coating of the desired porosity will be obtained, and curing the deposited film at a temperature effective for curing whereby there is obtained a thin film of a polymer of a predetermined porosity and corresponding pore size on the substrate.

Influence of polymer additives on turbulence in von Karman swirling flow between two disks. II

NASA Astrophysics Data System (ADS)

Burnishev, Yuri; Steinberg, Victor

2016-03-01

We present the experimental studies of the influence of polymer additives on the statistical and scaling properties of the fully developed turbulent regime in a von Karman swirling flow driven either by the smooth or bladed disks using only the global measurements of torque Γ and pressure p fluctuations in water- and water-sugar-based solutions of different viscosities, or elasticity El, and different polymer concentrations ϕ as a function of Re in the same apparatus. There are three highlights achieved and reported in the paper: (i) An observation of turbulent drag reduction (TDR) at both the inertial and viscous flow forcing, in a contradiction to a currently accepted opinion that only the viscous forcing leads to TDR, and the unexpected drastic difference in the transition to the fully developed turbulent and TDR regimes in von Karman swirling flow of water-based polymer solutions depending on the way of the forcing; (ii) a continuous transition to TDR in both the normalized torque drop and the rms pressure fluctuations drop and universality in scaling behavior of Cf in an agreement with theoretical predictions; and (iii) the dramatic differences in the appearance of the frequency power spectra of Γ and in particular p due to the different ways of the forcing are also observed. We discuss and summarize further the results in accordance with these three main achievements. The main message of these studies is that both the inertial forcing and viscous forcing of von Karman swirling flow between two counter-rotating disks lead to TDR in the sharp contrast to the currently accepted opinion [O. Cadot et al., "Turbulent drag reduction in a closed flow system: Boundary layer versus bulk effects," Phys. Fluids 10, 426 (1998); D. Bonn et al., "From scale scales to large scales in three-dimensional turbulence: The effect of diluted polymers," Phys. Rev. E 47, R28 (1993); and D. Bonn et al., "Turbulent drag reduction by polymers," J. Phys.: Condens. Matter 17, S1195 (2005)] that TDR can be observed only at the viscous driving. In this observation, Cadot et al. and Bonn et al., relate to exclusively boundary effect, whereas the existence of TDR in both ways of the flow forcing suggests that both boundary and bulk effects are responsible for TDR. The unexpected result of the striking difference in the transition to the fully developed turbulent and TDR regimes and in their properties in von Karman swirling flow of water-based polymer solutions for the viscous and inertial forcing is reported. For the viscous forcing, just the single turbulent regime is found with the transition values R ec turb = R ec T D R ≃ ( 4 . 8 ± 0 . 2 ) × 1 0 5 independent of polymer concentration ϕ, while for the inertial forcing two turbulent regimes are revealed: fully developed turbulence and the TDR regime with the transition values R ec turb < R ec T D R and both depending on ϕ. Thus in the case of the viscous forcing, the onset to turbulence is not altered by the addition of polymers in the contrast to the inertial forcing, where early turbulence is found. Both regimes differ by the scaling exponents of the fundamental turbulent characteristics, by the dependence of skewness and flatness of probability density functions of p on Re, and by the drastically different frequency power spectra of Γ and p with the different dependencies of their frequency peaks on ϕ. It is also demonstrated that the transition to the TDR state is a continuous one for both Γ ¯ and prms in accord with theoretical arguments and simulations presented in the work of Boffetta et al. ["Drag reduction in the turbulent Kolmogorov flow," Phys. Rev. E 71, 036307 (2005)]. Indeed, Cf presented as a function of R e / R ec T D R for different El show impressive collapse of the data and universal behavior above Rc T D R with the functional dependencies in a full agreement with the prediction from the numerical simulations (Boffetta et al.). Moreover, the crucial issue for the existence of TDR followed from the analysis of stresses in the TDR model is also satisfied in the experiment (Boffetta et al.). As pointed out in the work of Boffetta et al., understanding the reasons of this inequality meaning that the larger effectiveness of the momentum transfer to velocity fluctuations than to elastic stress would reveal the TDR physical mechanism. The power spectra of both Γ and p in the case of the inertial forcing are characterized by the emerging pronounced peaks and their higher harmonics in parallel with up to two orders of magnitude reduction of low frequency fluctuation amplitudes in both the water- and water-sugar-based polymer solutions compared with the power spectra for the Newtonian solvents. The peaks appear at R e ≥ R ec T D R and their normalized peak frequency fp/frot = 0.43 ± 0.02 is independent of El, ϕ, and Re. These observations agree with the numerical results, where the enhancement of the main flow compared to the Newtonian case and the strong reduction of turbulent fluctuations were also observed and quantified. On the other hand, in the case of the viscous forcing, polymers do not alter the appearance of the power spectra of p compared with water, though the scaled peak frequencies fp/frot vary with Re for all ϕ from unity at smaller Re to fp/frot = 0.6 ± 0.02 independent of ϕ and Re in the turbulent regime. Thus the inertial forcing turns out to be much more effective in the pumping energy from turbulent fluctuations into the main vortex due to stronger polymer stretching in the TDR regime that also reveals in more pronounced TDR. We suggest an explanation of the observed effects.

Turbulence of polymer solutions.

PubMed

Balkovsky, E; Fouxon, A; Lebedev, V

2001-11-01

We investigate high-Reynolds-number turbulence in dilute polymer solutions. We show the existence of a critical value of the Reynolds number, which separates two different regimes. In the first regime, below the transition, the influence of the polymer molecules on the flow is negligible, so they can be regarded as passively embedded in the flow. This case admits a detailed investigation of the statistics of the polymer elongations. The second state is realized when the Reynolds number is larger than the critical value. This regime is characterized by the strong back reaction of polymers on the flow. We establish some properties of the statistics of the stress and velocity in this regime and discuss its relation to the drag reduction phenomenon.

Phase equilibria in polymer-blend thin films

NASA Astrophysics Data System (ADS)

Clarke, Nigel; Souche, Mireille

2010-03-01

To describe equilibrium concentration profiles in thin films of polymer mixtures, we propose a Hamiltonian formulation of the Flory-Huggins-de Gennes theory describing a polymer blend thin film. We first focus on the case of 50:50 polymer blends confined between anti-symmetric walls. The different phases of the system and the transitions between them, including finite size effects, are systematically studied through their relation with the geometry of the Hamiltonian flow in phase space. This method provides an easy and efficient way, with strong graphical insight, to infer the qualitative physical behavior of polymer blend thin films. The addition of a further degree of freedom in the system, namely a solvent, may result in a chaotic behavior of the system, characterized by the existence of solutions with exponential sensitivity to initial conditions. Such solutions and there subsequent contribution to the out-of-equilibrium dynamics of the system are well described in Hamiltonian formalism. A fully consistent treatment of the Flory-Huggins-de Gennes theory of thin film polymer blend solutions, in the spirit of the Hamiltonian approach will be presented. 1. M. Souche and N. Clarke, J. Chem. Phys., submitted.

Anisotropic membranes for gas separation

DOEpatents

Gollan, A.Z.

1987-07-21

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7--25 C and then air dried at ambient temperature, typically 10--30 C. 2 figs.

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge.

PubMed

Jung, Hee Joon; Huh, June; Park, Cheolmin

2012-10-21

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm(-1)). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge

NASA Astrophysics Data System (ADS)

Jung, Hee Joon; Huh, June; Park, Cheolmin

2012-09-01

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm-1). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

Frictional properties of the end-grafted polymer layer in presence of salt solution

NASA Astrophysics Data System (ADS)

Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

2012-02-01

We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). These brushes had constant grafting density (1.18 nm2), and of a thickness of ˜66 nm, as measured by ellipsometry. We show that single asperity contact mechanics (Johnson-Kendall-Roberts (JKR) and Derjaguin-M"uller-Toporov (DMT) models) as well as a linear (Amontons) relation between applied load and frictional load all apply to these systems depending on the concentration of salt and the nature of the FFM probe. Measurements were made using gold-coating and polymer functionalized silicon nitride triangular probes. Polymer functionalized probe included growth the PDMAEMA with same method on tips. The frictional behaviour are investigated between PDMAEMA and gold coated and PDMAEMA tips immersed in different concentrations of KCl, KBr and KI.

Polymer thin film as coating layer to prevent corrosion of metal/metal oxide film

NASA Astrophysics Data System (ADS)

Sarkar, Suman; Kundu, Sarathi

2018-04-01

Thin film of polymer is used as coating layer and the corrosion of metal/metal oxide layer is studied with the variation of the thickness of the coating layer. The thin layer of polystyrene is fabricated using spin coating method on copper oxide (CuO) film which is deposited on glass substrate using DC magnetron sputtering technique. Thickness of the polystyrene and the CuO layers are determined using X-ray reflectivity (XRR) technique. CuO thin films coated with the polystyrene layer are exposed to acetic acid (2.5 v/v% aqueous CH3COOH solution) environments and are subsequently analyzed using UV-Vis spectroscopy and atomic force microscopy (AFM). Surface morphology of the film before and after interaction with the acidic environment is determined using AFM. Results obtained from the XRR and UV-Vis spectroscopy confirm that the thin film of polystyrene acts as an anticorrosion coating layer and the strength of the coating depends upon the polymer layer thickness at a constant acid concentration.

Mapping Viscoelastic and Plastic Properties of Polymers and Polymer-Nanotube Composites using Instrumented Indentation

PubMed Central

Gayle, Andrew J.; Cook, Robert F.

2016-01-01

An instrumented indentation method is developed for generating maps of time-dependent viscoelastic and time-independent plastic properties of polymeric materials. The method is based on a pyramidal indentation model consisting of two quadratic viscoelastic Kelvin-like elements and a quadratic plastic element in series. Closed-form solutions for indentation displacement under constant load and constant loading-rate are developed and used to determine and validate material properties. Model parameters are determined by point measurements on common monolithic polymers. Mapping is demonstrated on an epoxy-ceramic interface and on two composite materials consisting of epoxy matrices containing multi-wall carbon nanotubes. A fast viscoelastic deformation process in the epoxy was unaffected by the inclusion of the nanotubes, whereas a slow viscoelastic process was significantly impeded, as was the plastic deformation. Mapping revealed considerable spatial heterogeneity in the slow viscoelastic and plastic responses in the composites, particularly in the material with a greater fraction of nanotubes. PMID:27563168

Dynamic mechanical thermal analysis of hypromellose 2910 free films.

PubMed

Cespi, Marco; Bonacucina, Giulia; Mencarelli, Giovanna; Casettari, Luca; Palmieri, Giovanni Filippo

2011-10-01

It is common practice to coat oral solid dosage forms with polymeric materials for controlled release purposes or for practical and aesthetic reasons. Good knowledge of thermo-mechanical film properties or their variation as a function of polymer grade, type and amount of additives or preparation method is of prime importance in developing solid dosage forms. This work focused on the dynamic mechanical thermal characteristics of free films of hypromellose 2910 (also known as HPMC), prepared using three grades of this polymer from two different manufacturers, in order to assess whether polymer chain length or origin affects the mechanical or thermo-mechanical properties of the final films. Hypromellose free films were obtained by casting their aqueous solutions prepared at a specific concentrations in order to obtain the same viscosity for each. The films were stored at room temperature until dried and then examined using a dynamic mechanical analyser. The results of the frequency scans showed no significant differences in the mechanical moduli E' and E″ of the different samples when analysed at room temperature; however, the grade of the polymer affected material transitions during the heating process. Glass transition temperature, apparent activation energy and fragility parameters depended on polymer chain length, while the material brand showed little impact on film performance. Copyright © 2011 Elsevier B.V. All rights reserved.

Extensional Rheology Experiment Developed to Investigate the Rheology of Dilute Polymer Solutions in Microgravity

NASA Technical Reports Server (NTRS)

Logsdon, Kirk A.

2001-01-01

A fundamental characteristic of fluid is viscosity; that is, the fluid resists forces that cause it to flow. This characteristic, or parameter, is used by manufacturers and end-users to describe the physical properties of a specific material so that they know what to expect when a material, such as a polymer, is processed through an extruder, a film blower, or a fiber-spinning apparatus. Normally, researchers will report a shear viscosity that depends on the rate of an imposed shearing flow. Although this type of characterization is sufficient for some processes, simple shearing experiments do not provide a complete picture of what a processor may expect for all materials. Extensional stretching flows are common in many polymer-processing operations such as extrusion, blow molding, and fiber spinning. Therefore, knowledge of the complete rheological (ability to flow and be deformed) properties of the polymeric fluid being processed is required to accurately predict and account for the flow behavior. In addition, if numerical simulations are ever able to serve as a priori design tools for optimizing polymer processing operations such as those described above, an accurate knowledge of the extensional viscosity of a polymer system and its variation with temperature, concentration, molecular weight, and strain rate is critical.

Single step synthesis and organization of gold colloids assisted by copolymer templates

NASA Astrophysics Data System (ADS)

Sarrazin, Aurélien; Gontier, Arthur; Plaud, Alexandre; Béal, Jérémie; Yockell-Lelièvre, Hélène; Bijeon, Jean-Louis; Plain, Jérôme; Adam, Pierre-Michel; Maurer, Thomas

2014-06-01

We report here an original single-step process for the synthesis and self-organization of gold colloids by simply incorporating gold salts into a solution prepared using polystyrene (PS)-polymethylmethacrylate copolymer and thiolated PS with propylene glycol methyl ether acetate as a solvent. The spin-coating and annealing of this solution then allows the formation of PS domains. Depending on the polymer concentration of the as-prepared solution, there can be either one or several gold nanoparticles (Au NPs) per PS domain. For high concentrations of Au NPs in PS domains, the coupling between plasmonic NPs leads to the observation of a second peak in the optical extinction spectrum. Such a collective effect could be relevant for the development of optical strain sensors in the near future.

Nanoparticle solutions as adhesives for gels and biological tissues

NASA Astrophysics Data System (ADS)

Rose, Séverine; Prevoteau, Alexandre; Elzière, Paul; Hourdet, Dominique; Marcellan, Alba; Leibler, Ludwik

2014-01-01

Adhesives are made of polymers because, unlike other materials, polymers ensure good contact between surfaces by covering asperities, and retard the fracture of adhesive joints by dissipating energy under stress. But using polymers to `glue' together polymer gels is difficult, requiring chemical reactions, heating, pH changes, ultraviolet irradiation or an electric field. Here we show that strong, rapid adhesion between two hydrogels can be achieved at room temperature by spreading a droplet of a nanoparticle solution on one gel's surface and then bringing the other gel into contact with it. The method relies on the nanoparticles' ability to adsorb onto polymer gels and to act as connectors between polymer chains, and on the ability of polymer chains to reorganize and dissipate energy under stress when adsorbed onto nanoparticles. We demonstrate this approach by pressing together pieces of hydrogels, for approximately 30 seconds, that have the same or different chemical properties or rigidities, using various solutions of silica nanoparticles, to achieve a strong bond. Furthermore, we show that carbon nanotubes and cellulose nanocrystals that do not bond hydrogels together become adhesive when their surface chemistry is modified. To illustrate the promise of the method for biological tissues, we also glued together two cut pieces of calf's liver using a solution of silica nanoparticles. As a rapid, simple and efficient way to assemble gels or tissues, this method is desirable for many emerging technological and medical applications such as microfluidics, actuation, tissue engineering and surgery.

Carbon nanotube-polymer composite actuators

DOEpatents

Gennett, Thomas [Denver, CO; Raffaelle, Ryne P [Honeoye Falls, NY; Landi, Brian J [Rochester, NY; Heben, Michael J [Denver, CO

2008-04-22

The present invention discloses a carbon nanotube (SWNT)-polymer composite actuator and method to make such actuator. A series of uniform composites was prepared by dispersing purified single wall nanotubes with varying weight percents into a polymer matrix, followed by solution casting. The resulting nanotube-polymer composite was then successfully used to form a nanotube polymer actuator.

Electroless metal plating of plastics

DOEpatents

Krause, Lawrence J.

1986-01-01

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Electroless metal plating of plastics

DOEpatents

Krause, L.J.

1982-09-20

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Electroless metal plating of plastics

DOEpatents

Krause, Lawrence J.

1984-01-01

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Diverse 2D structures obtained by adsorption of charged ABA triblock copolymer on different surfaces

NASA Astrophysics Data System (ADS)

Kontturi, Katri S.; Vesterinen, Arja-Helena; Seppälä, Jukka; Laine, Janne

2012-11-01

In the larger context of 2D polymeric structures, the morphologies obtained by adsorption and subsequent drying of charged, ABA type amphiphilic triblock copolymer of poly[2-(dimethylamino)ethyl metacrylate] (PDMAEMA) and poly(propylene oxide) (PPO) were investigated with atomic force microscopy and X-ray photoelectron spectroscopy as well as in situ adsorption analysis with quartz crystal microbalance with dissipation monitoring. Hydrophilic silica and hydrophobic polystyrene (PS) were used as substrates for adsorption. The structures emerging from the self-assembly of adsorbing polymer were profoundly influenced by composition of the aqueous solution and the choice of substrate. When adsorbed from dilute polymer solution where the concentration is so low that the polymer does not yet show surface-active behavior, the triblock copolymer unimers associated on hydrophilic silica surface forming large, irregular clustered aggregates, with sizes increasing with electrolyte concentration of the solution. On a hydrophobic PS substrate, on the other hand, unimers spread much more evenly, forming clear surface patterns. The roughness of these patterned structures was tuned with the electrolyte concentration of the solution. Adsorption from a more concentrated polymer solution, where the surface-activity of the polymer is perceptible, resulted in the formation of a smooth film with complete coverage over the hydrophilic silica substrate when the electrolyte concentration was high. On PS, on the other hand, nucleation of evenly scattered globular, disk-like micelles was induced. Besides the dry film morphology, the even distribution of the irreversibly adsorbed polymer over the PS surface was likely to serve as an optimal platform for the build-up of reversible hydrophobically bound multilayers at high electrolyte concentration. The multilayer formation was reversible because a decrease in the electrolyte concentration of the solution re-introduces strong electrostatic repulsion between the multilayered polymer coils which results in breakdown of the layer.

Ultrafast Transient Absorption Spectroscopy Investigation of Photoinduced Dynamics in POLY(3-HEXYLTHIOPHENE)-BLOCK-OLIGO(ANTHRACENE-9,10-DIYL)

NASA Astrophysics Data System (ADS)

Strain, Jacob; Rathnayake, Hemali; Liu, Jinjun

2017-06-01

Semiconducting polymer nanostructures featuring bulk heterojunction (BHJ) architecture are promising light harvesters in photovoltaic (PV) devices because they allow control of individual domain sizes, internal structure and ordering, as well as well-defined contact between the electron donor and acceptor. Power conversion efficiency (PCE) of PV devices strongly depends on photoinduced dynamics. Understanding and optimizing photoinduced charge transfer processes in BHJ's hence help improve the performance of PV devices and increase their PCE in particular. We have investigated the photoinduced dynamics of a block polymer containing moieties of poly-3-hexylthiophene (P3HT) and polyanthracene (PANT) in solution and in solid state with femtosecond transient absorption (TA) spectroscopy. The dynamics of the polymer PANT alone are also studied as a control. The TA spectra of PANT includes a strong excited state absorption centered at 610 (nm) along with a stimulated emission signal stretching past the detection limit into the UV region which is absent in the monomer's spectra in the detection window. The block polymer's TA spectra strongly resembles that of P3HT but a noticeable positive pull on P3HT's stimulated emission signal residing at 575-620 (nm) is indicative of the excited state absorption of PANT in the adjacent spectral region. The doubling of the lifetime exciton delocalization on the block polymer versus P3HT alone have alluded that the lifetime of P3HT is extended by the covalent addition of PANT. The current spectroscopic investigation represents an interesting example of photoinduced processes in systems with complex energy level structure. Studies of dependence of change generation and separation on composition, dimension, and morphology of the heterojunctions are in process.

A Helical Flow, Circular Microreactor For Separating and Enriching “Smart” Polymer-Antibody Capture Reagents

PubMed Central

Hoffman, John M.; Ebara, Mitsuhiro; Lai, James J.; Hoffman, Allan S.; Folch, Albert

2011-01-01

We report a mechanistic study of how flow and recirculation in a microreactor can be used to optimize the capture and release of stimuli-responsive polymer-protein reagents on stimuli-responsive polymer-grafted channel surfaces. Poly(N-isopropylacrylamide) (PNIPAAm) was grafted to poly(dimethyl)siloxane (PDMS) channel walls, creating switchable surfaces where PNIPAAm-protein conjugates would adhere at temperatures above the lower critical solution temperature (LCST) and released below the LCST. A PNIPAAm-streptavidin conjugate that can capture biotinylated antibody-antigen targets was first characterized. The conjugate’s immobilization and release were limited by mass transport to and from the functionalized PNIPAAm surface. Transport and adsorption efficiencies were dependent on the aggregate size of the PNIPAAm-streptavidin conjugate above the LCST and also was dependent on whether the conjugates were heated in the presence of the stimuli-responsive surface or pre-aggregated and then flowed across the surface. As conjugate size increased, through the addition of non-conjugated PNIPAAm, recirculation and mixing were shown to markedly improve conjugate immobilization compared to diffusion alone. Under optimized conditions of flow and reagent concentrations, approximately 60% of a streptavidin conjugate bolus could be captured at the surface and subsequently successfully released. The kinetic release profile sharpness was also strongly improved with recirculation and helical mixing. Finally, the concentration of protein-polymer conjugates could be achieved by continuous conjugate flow into the heated recirculator, allowing nearly linear enrichment of the conjugate reagent from larger volumes. This capability was shown with anti-p24 HIV monoclonal antibody reagents that were enriched over 5-fold using this protocol. These studies provide insight into the mechanism of smart polymer-protein conjugate capture and release in grafted channels and show the potential of this purification and enrichment module for processing diagnostic samples. PMID:20882219

SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirosawa, Kazu; Fujii, Kenta; Ueki, Takeshi

Here, we utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d 8-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d 8-[C 2mIm +][TFSA -]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at T c. We also evaluated the enthalpic and entropic contributions to the effective interaction parameter χ eff of PPhEtMA in [C 2mIm +][TFSA -] and compared them with thosemore » of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χ eff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. Finally, it was found out that the strong dependence of T c on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χ eff.« less

SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

DOE PAGES

Hirosawa, Kazu; Fujii, Kenta; Ueki, Takeshi; ...

2016-06-17

Here, we utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d 8-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d 8-[C 2mIm +][TFSA -]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at T c. We also evaluated the enthalpic and entropic contributions to the effective interaction parameter χ eff of PPhEtMA in [C 2mIm +][TFSA -] and compared them with thosemore » of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χ eff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. Finally, it was found out that the strong dependence of T c on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χ eff.« less

Method for preparing polyaniline fibers

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

2000-01-01

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Kinetic aspects of the coil-stretch transition of polymer chains in dilute solution under extensional flow

NASA Astrophysics Data System (ADS)

Hernández Cifre, J. G.; García de la Torre, J.

2001-11-01

When linear polymer chains in dilute solution are subject to extensional flow, each chain in the sample experiences the coil-stretch transition at a different time. Using Brownian dynamics simulation, we have studied the distribution of transition times in terms of the extensional rate and the length of the chains. If instead of time one characterizes the effect of the flow by the accumulated strain, then the distribution and its moments seem to take general forms, independent of molecular weight and flow rate, containing some numerical, universal constants that have been evaluated from the dynamical simulation. The kinetics of the transition, expressed by the time-dependence of the fraction of remaining coils, has also been simulated, and the results for the kinetic rate constant has been rationalized in a manner similar to that used for the transition time. The molecular individualism, characterized in this work by the distribution of transition times, is related to the excess of the applied extensional rate over its critical value, which will determine the transition time and other features of the coil-stretch transition.

Influence of entanglements on glass transition temperature of polystyrene

NASA Astrophysics Data System (ADS)

Ougizawa, Toshiaki; Kinugasa, Yoshinori

2013-03-01

Chain entanglement is essential behavior of polymeric molecules and it seems to affect many physical properties such as not only viscosity of melt state but also glass transition temperature (Tg). But we have not attained the quantitative estimation because the entanglement density is considered as an intrinsic value of the polymer at melt state depending on the chemical structure. Freeze-drying method is known as one of the few ways to make different entanglement density sample from dilute solution. In this study, the influence of entanglements on Tg of polystyrene obtained by the freeze-dried method was estimated quantitatively. The freeze-dried samples showed Tg depression with decreasing the concentration of precursor solution due to the lower entanglement density and their depressed Tg would be saturated when the almost no intermolecular entanglement was formed. The molecular weight dependence of the maximum value of Tg depression was discussed.

Synthesis and Evaluation of Cyclodextrin-based Polymers for Patulin Extraction from Aqueous Solutions

USDA-ARS?s Scientific Manuscript database

Patulin is a mycotoxin produced by fungi that contaminate fruits, juices, and other agricultural commodities. Sorption properties of polyurethane-beta-cyclodextrin polymers were evaluated for the ability to remove patulin from solutions, including apple juice. Freundlich isotherm analysis determin...

Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2016-05-01

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

Dynamics of associative polymer solutions: Capillary break-up, jetting and rheology

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Serdy, James G.; Threfall-Holmes, Phil; McKinley, Gareth H.

2011-11-01

Associative polymer solutions are used in extensively in the formulations for water-borne paints, food, inks, cosmetics, etc to control the rheology and processing behavior of multi-component dispersions. These complex dispersions are processed and used over a broad range of shear and extensional rates. Furthermore, the commercially relevant formulations use dilute solutions of associative polymers, which have low viscosity and short relaxation times, and hence their non-Newtonian response is not apparent in a conventional rheometer. In this talk, we explore several methods for systematically exploring the linear and nonlinear solution rheology of associative polymer dispersions, including: fractional model description of physical gelation, high frequency oscillatory tests at frequencies up to 10 kHz, microfluidic shear rheometry at deformation rates up to 1000000 /s and the influence of transient extensional rheology in the jet breakup. We show that high deformation rates can be obtained in jetting flows, and the growth and evolution of instability during jetting and break-up of these viscoelastic fluids shows the influence of both elasticity and extensibility.

Dynamics of associative polymer solutions: Capillary break-up, jetting and rheology

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Serdy, James G.; Threfall-Holmes, Phil; McKinley, Gareth H.

2010-03-01

Associative polymer solutions are used in extensively in the formulations for water-borne paints, food, inks, cosmetics, etc to control the rheology and processing behavior of multi-component dispersions. The commercially relevant formulations use dilute solutions of associative polymers, which have low viscosity and short relaxation times, and hence their non-Newtonian response is not apparent in a conventional rheometer. In this talk, we explore several methods for systematically exploring the linear and nonlinear solution rheology of associative polymer dispersions, including: high frequency oscillatory tests at frequencies up to 10 kHz, microfluidic shear rheometry at deformation rates up to 10^6 s-1 and the influence of transientextensional rheology in the jet breakup. The presence of inertial, elastic and viscous effects typically leads to complex dynamics in a necking fluid thread. We show that by carefully controlling the excitation frequency, it is possible to drive the break-up in a particularly simple and symmetric mode, which can be used to extract extensional viscosity information using capillary thinning analysis.

Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight

PubMed Central

Zhang, Yanjie; Furyk, Steven; Sagle, Laura B.; Cho, Younhee; Bergbreiter, David E.; Cremer, Paul S.

2008-01-01

The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two step transition was found to be sensitive to the polymer’s molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer’s molecular weight or solution concentration. PMID:18820735

Laboratory study of polymer solutions used for mobility control during in situ NAPL recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martel, K.E.; Martel, R.; Lefebvre, R.

1998-12-31

The use of surfactant solutions for the in situ recovery of residual NAPL in aquifers is increasingly considered as a viable remediation technique. The injection of a few pore volumes of high-concentration surfactant solutions can mobilize or solubilize most of the residual NAPL contacted by the solutions. However, the washing solutions` physico-chemical properties (low density and high viscosity), combined with the natural porous media heterogeneity, can prevent a good sweep of the entire contaminated volume. The objective of this laboratory study is first to select and characterize polymers that would be suitable for aquifer restoration. Their experiments showed that amongmore » several polymers, xanthan gum is the most suitable for aquifer remediation. An evaluation of xanthan gum solution rheology was made in order to predict shear rates, xanthan gum concentrations, salinity, and temperature effects on solution viscosity. The second set of experiments were made with a sand box which was designed to reproduce a simple heterogeneous media consisting of layers of sand with different permeability. These tests illustrate the xanthan gum solution`s ability to increase surfactant solution`s sweep efficiency and limit viscous fingering.« less

Synthesis, Characterization and Conductivity Study of Poly(vinyl 4-HYDROXY-3-METHOXY Benzal) and its Sodio Salt in Solid State

NASA Astrophysics Data System (ADS)

Borah, P.; Hussain, S.; Dutta, A.

Among the various ion-conducting materials, polymer salt complexes are of current interest due to their possible application as solid electrolyte as well as their physical nature in advanced high-energy electrochemical devices such as batteries, fuel cells, electrochromic display devices, photo electro-chemical solar cells52-55 etc. The main advantages of polymeric electrolytes are their mechanical properties, ease of fabrication of thin films of desired sizes and their ability to form proper electrode-electrolyte contact. Polymer electrolyte usually consists of a polymer and a salt and is considered to be solid solutions in which the polymer functions as solvent. In the present paper the synthesis, characterization and the conductivity study of the polymer poly (vinyl 4-hydroxy-3-methoxy benzal) (PV-HMB) and its sodio salt (PV-HMB-Na) have been reported. The polymer was prepared by carrying out homogenous acetalization between the prepolymer poly vinylalcohol (PVA) and 4-hydroxy-3-methoxy benzaldehyde (vanilline). PVA was dissolved in dimethyl formamide (DMF) and lithium chloride (LiCl) system i.e., in non-aqueous medium. The sodio salt was prepared by alkalization. The polymer and its salt were characterized by IR, 1H NMR and DSC. Frequency and temperature dependence of ac conductivity has been studied to learn about the electrical conduction behaviour in this material. The electrical conductivity of the new polymeric salt was found to be in the range 10-4 to 10-6 Scm-1. There is about 103 to 104 fold increase in the conductivity of the new polymer salt. Apparent activation energy of the polymer and its salt were found to be 0.139 and 0.08998 ev respectively.

Inertial and viscoelastic forces on rigid colloids in microfluidic channels.

PubMed

Howard, Michael P; Panagiotopoulos, Athanassios Z; Nikoubashman, Arash

2015-06-14

We perform hybrid molecular dynamics simulations to study the flow behavior of rigid colloids dispersed in a dilute polymer solution. The underlying Newtonian solvent and the ensuing hydrodynamic interactions are incorporated through multiparticle collision dynamics, while the constituent polymers are modeled as bead-spring chains, maintaining a description consistent with the colloidal nature of our system. We study the cross-stream migration of the solute particles in slit-like channels for various polymer lengths and colloid sizes and find a distinct focusing onto the channel center under specific solvent and flow conditions. To better understand this phenomenon, we systematically measure the effective forces exerted on the colloids. We find that the migration originates from a competition between viscoelastic forces from the polymer solution and hydrodynamically induced inertial forces. Our simulations reveal a significantly stronger fluctuation of the lateral colloid position than expected from thermal motion alone, which originates from the complex interplay between the colloid and polymer chains.

Durability Studies on Confined Concrete using Fiber Reinforced Polymer

NASA Astrophysics Data System (ADS)

Ponmalar, V.; Gettu, R.

2014-06-01

In this study, 24 concrete cylinders with a notch at the centre were prepared. Among them six cylinders were wrapped using single and double layers of fiber reinforced polymer; six cylinders were coated with epoxy resin; the remaining cylinders were used as a control. The cylinders were exposed to wet and dry cycling and acid (3 % H2SO4) solution for the period of 120 days. Two different concrete strengths M30 and M50 were considered for the study. It is found that the strength, ductility and failure mode of wrapped cylinders depend on number of layers and the nature of exposure conditions. It was noticed that the damage due to wet and dry cycling and acid attack was severe in control specimen than the epoxy coated and wrapped cylinders.

Nonlinear-optical studies of organic liquids and polymer optical fibers

NASA Astrophysics Data System (ADS)

Vigil, Steven Richard

We present the results of non-resonant optical Kerr effect measurements of the neat organic liquids nitrobenzene, carbon disulfide, carbon tetrachloride, and methyl-methacrylate. We also present the results of one- photon resonant optical Kerr effect measurements of solutions of the organic dyes indole squarylium and silicon-phthalocyanine:methylmethacrylate (separately) in carbon tetrachloride. Fits of the molecular third-order susceptibility theory to the one-photon resonant data indicate the presence of high-lying two-photon states for each of the dye molecules studied. We also present results concerning light coupling in dye- doped dual-core polymer optical fibers. Measurements of the coupling length at low intensity are in agreement with linear coupling length calculations. Intensity- dependent coupling is observed as the intensity launched into the fiber is increased.

Fabrication of multilayered thin films via spin-assembly

DOEpatents

Chiarelli, Peter A.; Robinson, Jeanne M.; Casson, Joanna L.; Johal, Malkiat S.; Wang, Hsing-Lin

2007-02-20

An process of forming multilayer thin film heterostructures is disclosed and includes applying a solution including a first water-soluble polymer from the group of polyanionic species, polycationic species and uncharged polymer species onto a substrate to form a first coating layer on the substrate, drying the first coating layer on the substrate, applying a solution including a second water-soluble polymer from the group of polyanionic species, polycationic species and uncharged polymer species onto the substrate having the first coating layer to form a second coating layer on the first coating layer wherein the second water-soluble polymer is of a different material than the first water-soluble polymer, and drying the second coating layer on the first coating layer so as to form a bilayer structure on the substrate. Optionally, one or more additional applying and drying sequences can be repeated with a water-soluble polymer from the group of polyanionic species, polycationic species and uncharged polymer species, so that a predetermined plurality of layers are built up upon the substrate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winstead, Cherese; Katagumpola, Pushpika

The degrees of substitution of chitosan derivatives were varied and the viscoelastic behavior of these biopolymer solutions was studied using rheology. Chitosan is a cationic copolymer of glucosamine and N-acetylglucosamine obtained by alkaline deacetylation of chitin. Due to its inherent non-toxicity, biocompatibility, and biodegradability, chitosan has gained much interest. However, the poor solubility of the biopolymer in water and most common organic solvents limits its applications. Therefore, the focus of this work is the chemical modification of chitosan via carboxymethylation as well as studying the viscoelastic behavior of these polymer solutions. Varying degrees of substitution (DS) of carboxymethyl chitosan derivativesmore » were synthesized by treating chitosan with monochloroacetic acid under alkylated medium varying the reaction time and temperature. The effect of degree of substitution on the rheology of these polymer solutions was studied as a function of concentration. The viscosity of chitosan derivatives sharply increased with increase in degree of substitution. G' and G' dependence on strain and angular frequency were studied and were found to exhibit predominantly viscous behavior. Additional characterization of the derivatized products were further studied using Fourier transform infrared (FT-IR), {sup 1}H Nuclear Magnetic Resonance ({sup 1}H NMR) spectroscopy, X-ray diffraction (XRD), and thermal gravimetric analysis as well as differential scanning calorimetry (DSC). Degree of substitution (DS) was calculated by titrimetric method.« less

Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

1999-11-09

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (between 15% and 30% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Method for producing a selectively permeable separation module

DOEpatents

Stone, Mark L.; Orme, Christopher J.; Peterson, Eric S.

2000-03-14

A method and apparatus is provided for casting a polymeric membrane on the inside surface of porous tubes to provide a permeate filter system capable of withstanding hostile operating conditions and having excellent selectivity capabilities. Any polymer in solution, by either solvent means or melt processing means, is capable of being used in the present invention to form a thin polymer membrane having uniform thickness on the inside surface of a porous tube. Multiple tubes configured as a tubular module can also be coated with the polymer solution. By positioning the longitudinal axis of the tubes in a substantially horizontal position and rotating the tube about the longitudinal axis, the polymer solution coats the inside surface of the porous tubes without substantially infiltrating the pores of the porous tubes, thereby providing a permeate filter system having enhanced separation capabilities.

Strong size-dependent stress relaxation in electrospun polymer nanofibers

NASA Astrophysics Data System (ADS)

Wingert, Matthew C.; Jiang, Zhang; Chen, Renkun; Cai, Shengqiang

2017-01-01

Electrospun polymer nanofibers have garnered significant interest due to their strong size-dependent material properties, such as tensile moduli, strength, toughness, and glass transition temperatures. These properties are closely correlated with polymer chain dynamics. In most applications, polymers usually exhibit viscoelastic behaviors such as stress relaxation and creep, which are also determined by the motion of polymer chains. However, the size-dependent viscoelasticity has not been studied previously in polymer nanofibers. Here, we report the first experimental evidence of significant size-dependent stress relaxation in electrospun Nylon-11 nanofibers as well as size-dependent viscosity of the confined amorphous regions. In conjunction with the dramatically increasing stiffness of nano-scaled fibers, this strong relaxation enables size-tunable properties which break the traditional damping-stiffness tradeoff, qualifying electrospun nanofibers as a promising set of size-tunable materials with an unusual and highly desirable combination of simultaneously high stiffness and large mechanical energy dissipation.

Strong size-dependent stress relaxation in electrospun polymer nanofibers

DOE PAGES

Wingert, Matthew C.; Jiang, Zhang; Chen, Renkun; ...

2017-01-04

Here, electrospun polymer nanofibers have garnered significant interest due to their strong size-dependent material properties, such as tensile moduli, strength, toughness, and glass transition temperatures. These properties are closely correlated with polymer chain dynamics. In most applications, polymers usually exhibit viscoelastic behaviors such as stress relaxation and creep, which are also determined by the motion of polymer chains. However, the size-dependent viscoelasticity has not been studied previously in polymer nanofibers. Here, we report the first experimental evidence of significant size-dependent stress relaxation in electrospun Nylon-11 nanofibers as well as size-dependent viscosity of the confined amorphous regions. In conjunction with themore » dramatically increasing stiffness of nano-scaled fibers, this strong relaxation enables size-tunable properties which break the traditional damping-stiffness tradeoff, qualifying electrospun nanofibers as a promising set of size-tunable materials with an unusual and highly desirable combination of simultaneously high stiffness and large mechanical energy dissipation.« less

Apparatus for and method of producing monodisperse submicron polymer powders from solution

DOEpatents

Noid, Donald W.; Otaigbe, Joshua U.; Barnes, Michael D.; Sumpter, Bobby G.; Kung, Chung-Yi

2002-01-01

This invention describes a method of producing polymer powders from solution in a compatible solvent using a new device referred to as a microdroplets on demand generator (MODG). The embodiment of this invention is the MODG apparatus and its relevance as a method to extensive application in materials science and technology. Proof of concept is demonstrated using poly(ethylene) glycol polymer microparticles generated with the MODG and captured in a microparticle levitation device.

Formation of biodegradated polymers as components of future composite materials on the basis of shape memory alloy of medical appointment

NASA Astrophysics Data System (ADS)

Nasakina, E. O.; Baikin, A. S.; Sergiyenko, K. V.; Kaplan, M. A.; Konushkin, S. V.; Yakubov, A. D.; Izvin, A. V.; Sudarchikova, M. A.; Sevost’yanov, M. A.; Kolmakov, A. G.

2018-04-01

The processes of formation of polymer polylactide or polyglycylidactide films for the subsequent creation of a layered composite with a biodegradable layer on the basis of a nickel-free shape memory alloy TiNbTaZr are studied. The structure of the samples was determined using an SEM. The correspondence of morphology of surfaces of and the substrate itself is noted. High adhesion of the polymer to the future basis of the developed composite material is supposed. The formed films is homogeneous and amorphous throughout the polymer volume. By varying the volume of solutions, it is possible to obtain films of a given thickness for any type of polymer, its molecular weight, and the solution concentration of the polymer in chloroform. Poly (glycolide-lactide) should be more plastic than polylactide.

Polymer formulations for gettering hydrogen

DOEpatents

Shepodd, Timothy J.; Even, Jr., William R.

2000-01-01

A novel method for preparing a hydrogenation composition comprising organic polymer molecules having carbon--carbon double bonds, for removing hydrogen from the atmosphere within enclosed spaces and particularly from atmospheres within enclosed spaces that contain air, water vapor, oxygen, carbon dioxide or ammonia. The organic polymers molecules containing carbon--carbon double bonds throughout their structures, preferably polybutadiene, polyisoprene and derivatives thereof, intimately mixed with an insoluble noble metal catalyst composition. High molecular weight polymers may be added to the organic polymer/catalyst mixture in order to improve their high temperature performance. The hydrogenation composition is prepared by dispersing the polymers in a suitable solvent, forming thereby a solution suspension, flash-freezing droplets of the solution in a liquid cryogen, freeze-drying the frozen droplets to remove frozen solvent incorporated in the droplets, and recovering the dried powder thus formed.

THERMAL DEGRADATION OF POLY (ALPHA-METHYLSTYRENE) IN SOLUTION

EPA Science Inventory

The thermal degradation of poly(alpha-methylstyrene) in solution was investigated at various temperatures (150-225 C) and polymer concentrations (2.00-20-0 g/l) at 6.8 MPa (1000 psig). The molecular weight distributions (MWDs) of the reacted polymer at these conditions were exami...

A remote query magnetoelastic pH sensor.

PubMed

Cai, Q Y; Grimes, C A

2000-11-15

A remote query magnetoelastic pH sensor comprised of a magnetoelastic thick-film coated with a mass-changing pH-responsive polymer is described. In response to a magnetic query field the magnetoelastic sensor mechanically vibrates at a characteristic frequency that is inversely dependent upon the mass of the attached polymer layer. As the magnetoelastic sensor is magnetostrictive the mechanical vibrations of the sensor launch magnetic flux that can be detected remotely from the sensor using a pickup coil. The pH responsive copolymer is synthesized from 20 mol% of acrylic acid and 80 mol% of iso-octyl acrylate and then deposited onto a magnetoelastic film by dip-coating. For a 1 micrometer polymer coating upon a 30 micrometer thick Metglas [The Metglas alloys are a registered trademark of Honeywell Corporation. For product information see: http://www.electronicmaterials.com:80/businesses/sem/amorph/page5_1_2.htm.] alloy 2826MB magnetoelastic film between pH 5 and 9 the change in resonant frequency is linear, approximately 285 Hz/pH or 0.6%/pH. The addition of 10 mmol/l of KCl to the test solution decreases the sensitivity of the polymer approximately 4%. c2000 Elsevier Science B.V. All rights reserved.

Versatile wettability gradients prepared by chemical modification of polymer brushes on polymer foils.

PubMed

Neuhaus, Sonja; Padeste, Celestino; Spencer, Nicholas D

2011-06-07

A method to create a wettability gradient by variation of the chemical functionality in a polymer brush is presented. A poly(N-methyl-vinylpyridinium) (QP4VP) brush was created on a poly(ethylene-alt-tetrafluoroethylene) (ETFE) foil by the grafting of 4-vinylpyridine and subsequent quaternization. The instability of QP4VP, a strong polyelectrolyte, in alkaline media was exploited to transform it to the neutral poly(vinyl(N-methyl-2-pyridone)) (PVMP), as confirmed with ATR-IR spectroscopy. The slow transformation resulted in a substantial, time-dependent decrease in wettability. A nearly linear gradient in water contact angle (CA) was created by immersion of a QP4VP brush modified sample into a sodium hydroxide solution, resulting in CAs ranging from 10° to 60°. The concurrent decrease in the number of charged functional groups along the gradient was characterized by loading an anionic dye into the polymer brush and measuring the UV transmittance of the sample. The versatility of the wettability gradient was demonstrated by exchanging the counterions of the N-methyl-vinylpyridinium groups, whereby a reversal of gradient direction was reproducibly achieved.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites.

PubMed

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D; Hill, Curtis W; Brewer, Jeffrey C; Tucker, Dennis S; Cheng, Z-Y

2016-10-21

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu 3 Ti 4 O 12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10 -1 ). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-10-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10-1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Stability of self-assembled polymer films investigated by optical laser reflectometry.

PubMed

Dejeu, Jérôme; Diziain, Séverine; Dange, Catherine; Membrey, François; Charraut, Daniel; Foissy, Alain

2008-04-01

We studied the influence of post-treatment rinsing after the formation of self-assembled polyelectrolyte films made with the weak base poly(allylamine hydrochloride) (PAH) and the strong acid poly(styrene sulfonate) (PSS). The stability of the film was studied using optical fixed-angle laser reflectometry to measure the release of polymeric material and AFM experiments to reveal the change of morphology and thickness. We found that the polymer films were stable upon rinsing when the pH was the same in the solution as that used in the buildup (pH 9). The films released most of the polymeric material when rinsed at higher pH values, but a layer remained that corresponded to a PAH monolayer directly bound with the silica surface. Films containing at least four bilayers were stable upon rinsing at lower pH values, but the stability of thinner films depended on the type of the last polymer deposited. They were stable in the case of PSS as an outermost deposit, but they released a large part of their material in the case of PAH. The stability results were determined using a simple model of the step-by-step assembly of the polymer film described formerly.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

PubMed Central

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-01-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing. PMID:27767184

Visible-light active conducting polymer nanostructures with superior photocatalytic activity

NASA Astrophysics Data System (ADS)

Ghosh, Srabanti; Kouame, Natalie Amoin; Remita, Samy; Ramos, Laurence; Goubard, Fabrice; Aubert, Pierre-Henri; Dazzi, Alexandre; Deniset-Besseau, Ariane; Remita, Hynd

2015-12-01

The development of visible-light responsive photocatalysts would permit more efficient use of solar energy, and thus would bring sustainable solutions to many environmental issues. Conductive polymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a wide range of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidative polymerization demonstrate unprecedented photocatalytic activities for water treatment without the assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2 as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and are characterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOT-based photocatalysts are very stable with cycling and can be reused without appreciable loss of activity. Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts as compared to nanometric spindles suggesting size and shape dependent photocatalytic properties. The visible-light active photocatalytic properties of the polymer nanostructures present promising applications in solar light harvesting and broader fields.

Electrospinning of nanofibers from non-polymeric systems: polymer-free nanofibers from cyclodextrin derivatives

NASA Astrophysics Data System (ADS)

Celebioglu, Asli; Uyar, Tamer

2012-01-01

High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.

The Alginate Demonstration: Polymers, Food Science, and Ion Exchange

NASA Astrophysics Data System (ADS)

Waldman, Amy Sue; Schechinger, Linda; Govindarajoo, Geeta; Nowick, James S.; Pignolet, Louis H.

1998-11-01

We have recently devised a polymer demonstration involving the crosslinking and decrosslinking of alginate, a polysaccharide isolated from seaweed. The polymer is composed of D-mannuronic acid and L-guluronic acid subunits and is a component of cell walls. It is commonly used as a thickener in foods such as ice cream and fruit-filled snacks. For the demonstration, a 2% solution of sodium alginate is poured into a 1% solution of calcium chloride. Nontoxic calcium alginate "worms" form due to crosslinking of the polymer. Alternatively, the commercially available antacid Gaviscon can be used as a source of sodium alginate. The crosslinks can then be broken by shaking the worms in brine. The demonstration is a fine addition to any chemical educator's repertoire of polymer experiments.

Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

PubMed

Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

2015-01-01

Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

Capillary electrophoresis investigation on equilibrium between polymer-related and surfactant-related species in aqueous polymer-surfactant solutions.

PubMed

Wu, Yefan; Chen, Miaomiao; Fang, Yun; Zhu, Meng

2017-03-17

It was inferred from aqueous solution behavior of nonionic polymers and anionic surfactants that the formation of charged polymer-bound surfactant micelle above critical aggregation concentration (cac) and the formation of free surfactant micelle beyond polymer saturation point (psp), but there was still a lack of direct experimental evidence for the considered equilibrium chemical species. Three modes of capillary electrophoresis are applied in this paper to study the complexation between nonionic polymers, polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate (SDBS) by successfully distinguishing the imaginary charged polymer-bound SDBS micelle from nonionic polymer and SDBS molecule. Perhaps even more important, it is the action of SDBS as both a main surfactant and a UV probe that makes the free surfactant micelle emerged in electropherogram beyond psp, and thus makes it possible for the first time to provide the equilibrium relationship of the polymer-related and the surfactant-related species in the concentration regions divided into by cac and psp. Copyright © 2017 Elsevier B.V. All rights reserved.

Morphological control of inter-penetrating polymer networks

NASA Technical Reports Server (NTRS)

Hansen, Marion

1989-01-01

Synthetic organic polymer chemistry has been successful in producing composition of matter with thermal oxidation stability and progressively higher glass transition temperatures. In part, this was done by increasing the steric-hindrance of moieties in the chain of a macromolecule. The resulting polymers are usually quite insoluble and produce molten polymers of very high viscosities. These types of polymers are not easily processed into graphite fiber prepregs by melt or solution impregnation methods. Hence, a technological need exists to produce new knowledge of how to produce polymer-fiber composites from this class of polymers. The concept of freeze drying amic-acid prepolymers with reactive thermoplastic was proposed as a research topic for the ASEE/NASA Summer Faculty Program of 1989 as a means of producing polymer-fiber composites. This process scheme has the thermodynamic attribute that the magnitude of phase separation due to differences in solubility of two organic constituents in solution will be greatly reduced by removing a solvent not by evaporation but by sublimation. Progress to date on evaluating this polymer processing concept is briefly outlined.

Recovery of metals from simulant spent lithium-ion battery as organophosphonate coordination polymers in aqueous media.

PubMed

Perez, Emilie; Andre, Marie-Laure; Navarro Amador, Ricardo; Hyvrard, François; Borrini, Julien; Carboni, Michaël; Meyer, Daniel

2016-11-05

An innovative approach is proposed for the recycling of metals from a simulant lithium-ion battery (LIBs) waste aqueous solution. Phosphonate organic linkers are introduced as precipitating agents to selectively react with the metals to form coordination polymers from an aqueous solution containing Ni, Mn and Co in a hydrothermal process. The supernatant is analyzed by ICP-AES to quantify the efficiency and the selectivity of the precipitation and the materials are characterized by Scanning Electron Microscopy (SEM), Powder X-Ray Diffraction (PXRD), Thermogravimetric Analyses (TGA) and nitrogen gas sorption (BET). Conditions have been achieved to selectively precipitate Manganese or Manganese/Cobalt from this solution with a high efficiency. This work describes a novel method to obtain potentially valuable coordination polymers from a waste metal solution that can be generalized on any waste solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental Polymer Mechanochemistry and its Interpretational Frameworks.

PubMed

Akbulatov, Sergey; Boulatov, Roman

2017-06-02

Polymer mechanochemistry is an emerging field at the interface of chemistry, materials science, physics and engineering. It aims at understanding and exploiting unique reactivities of polymer chains confined to highly non-equilibrium stretched geometries by interactions with their surroundings. Macromolecular chains or their segments become stretched in bulk polymers under mechanical loads or when polymer solutions are sonicated or flow rapidly through abrupt contractions. An increasing amount of empirical data suggests that mechanochemical phenomena are widespread wherever polymers are used. In the past decade, empirical mechanochemistry has progressed enormously, from studying fragmentations of commodity polymers by simple backbone homolysis to demonstrations of self-strengthening and stress-reporting materials and mechanochemical cascades using purposefully designed monomers. This progress has not yet been matched by the development of conceptual frameworks within which to rationalize, systematize and generalize empirical mechanochemical observations. As a result, mechanistic and/or quantitative understanding of mechanochemical phenomena remains, with few exceptions, tentative. In this review we aim at systematizing reported macroscopic manifestations of polymer mechanochemistry, and critically assessing the interpretational framework that underlies their molecular rationalizations from a physical chemist's perspective. We propose a hierarchy of mechanochemical phenomena which may guide the development of multiscale models of mechanochemical reactivity to match the breadth and utility of the Eyring equation of chemical kinetics. We discuss the limitations of the approaches to quantifying and validating mechanochemical reactivity, with particular focus on sonicated polymer solutions, in order to identify outstanding questions that need to be solved for polymer mechanochemistry to become a rigorous, quantitative field. We conclude by proposing 7 problems whose solution may have a disproportionate impact on the development of polymer mechanochemistry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the simulation and theory of polymer dynamics in sieving media: Friction, molecular pulleys, Brownian ratchets and polymer scission

NASA Astrophysics Data System (ADS)

Kenward, Martin

The study of single polymer dynamics has, in the past few years, undergone a resurgence. This has been spurred on by the emergence of the fields of micro- and nanofluidics and their associated applications, especially by their ability to promise revolutionary techniques to, for example: rapidly sequence DNA, analyze proteins, carry out large-scale laboratory techniques in centimeter sized devices (lab-on-a-chip) and test and verify fundamental concepts related to the statistical physics of single molecules in fluids. In particular, the study of (typically single, isolated) polymers and the development of theoretical methods and computational tools to examine these polymers in microfluidic environments is a key challenge. In this thesis, we examine several different phenomena related to the dynamics of polymers in either microfluidic environments or related applications to DNA sequencing or separation. A recurrent theme throughout this work is the use of Molecular Dynamics (MD) simulations with an explicit solvent. Explicit solvent is an important aspect of our simulations and contrasts much work in the current literature which either artificially includes solvent or neglects it all together. This explicit inclusion of solvent allows us to explore phenomena (related to hydrodynamics) that is not observable with, for example, Brownian (or Langevin) Dynamics or Monte Carlo simulations. Chapter 2 contains a primarily computational examination of the friction coefficients of uncharged polymers. We explore the effects of deforming polymer chains on their friction coefficients along with examining several fundamental concepts of polymer friction (including hydrodynamic permeability). A key result is a verification of the hydrodynamic coupling of polymer chains resulting from a net reduction in the friction of polymer chains in hairpin (or folded) conformations. We also show that polymers undergo frictional transitions as they are stretched by an external force applied to the middle of the molecules. In chapter 3 we use some of the concepts and results from chapters 1 and 2 to explore the problem of a polymer chain migrating under the influence of an external force (or fluid flow) through a molecular obstacle course. These polymers collide with either fixed obstacles (or other polymers) and can be trapped in meta-stable long-lived, pulley-like conformations. This method can be used to separate polymers by molecular weight. We use both MD simulations and a general classical theory for the collisions to explore several different collision regimes. We also show that a classic experimental result, the formation of so-called V-shaped states, can occur in single polymer collision events, contrary to the popular assumption that it was necessary for a polymer to collide with multiple polymers. In chapter 4 we build on the results and ideas from the first three chapters and examine another phenomenon related to polymer transport, that of (Brownian) ratchets. A ratchet is essentially a method to rectify the thermal noise in a system in order to perform work, for example, to generate net transport. We use our MD simulations to examine the behaviour of polymers in the presence of an asymmetric saw tooth ratchet potential. We also show that existing ratchet models, where the ratchet widths are on the order of a polymer gyration radius, neglect an important effect of chain relaxation and thus underestimate optimal operating parameters. We propose and derive equations illustrating a new operational mode for a ratchet which inherently uses the deformation of polymer chains induced by the application of a ratcheting potential. We present a simple mathematical expression to incorporate time-dependent diffusion coefficients D (t) into ratchets. The final chapter presents work done in collaboration with Annelise Barron's group at Northwestern University and examines the breaking of polymer chains in extensional flow fields as a method to systematically and predictably reduce the polydispersity (PDI) of polymer solutions. The experimental investigation, carried out by the Barron group illustrated that a dilute polymer solution, when passed through a narrow constriction at high pressure can systematically reduce the PDI of the polymer solution. My contribution to this work was to develop a statistical model which calculates polymer molecular weight distributions and which can predict the resulting degraded polymer distribution. Two key things resulted from this investigation, the first is that polymers can break multiple times during a single scission event (i.e., one pass through the experimental system). Secondly we showed that it is possible to predictably reproduce polymer distributions after multiple scission events.

Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration

NASA Astrophysics Data System (ADS)

Ren, Liyun; Pandit, Vaibhav; Elkin, Joshua; Denman, Tyler; Cooper, James A.; Kotha, Shiva P.

2013-02-01

PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33423f

Organic-inorganic nano-composite films for photonic applications made by multi-beam multi-target pulsed laser deposition with remote control of the plume directions

NASA Astrophysics Data System (ADS)

Darwish, Abdalla M.; Moore, Shaelynn; Mohammed, Aziz; Alexander, Deonte'; Bastian, Tyler; Dorlus, Wydglif; Sarkisov, Sergey S.; Patel, Darayas N.; Mele, Paolo; Koplitz, Brent

2016-09-01

There has been an explosive interest in the technique of laser assisted deposition of polymer nano-composite films exploiting the matrix assisted pulsed laser evaporation (MAPLE) with regard to the polymer host as can be judged form recent publications.1-4 In MAPLE, a frozen solution of a polymer in a relatively volatile solvent is used as a laser target. The solvent and concentration are selected so that first, the polymer of interest can dissolve to form a dilute, particulate free solution, second, the majority of the laser energy is initially absorbed by the solvent molecules and not by the solute molecules, and third, there is no photochemical reaction between the solvent and the solute. The light-material interaction in MAPLE can be described as a photothermal process. The photon energy absorbed by the solvent is converted to thermal energy that causes the polymer to be heated but the solvent to vaporize. As the surface solvent molecules are evaporated into the gas phase, polymer molecules are exposed at the gas-target matrix interface. The polymer molecules attain sufficient kinetic energy through collective collisions with the evaporating solvent molecules, to be transferred into the gas phase. By careful optimization of the MAPLE deposition conditions (laser wavelength, repetition rate, solvent type, concentration, temperature, and background gas and gas pressure), this process can occur without any significant polymer decomposition. The MAPLE process proceeds layer-by-layer, depleting the target of solvent and polymer in the same concentration as the starting matrix. When a substrate is positioned directly in the path of the plume, a coating starts to form from the evaporated polymer molecules, while the volatile solvent molecules are evacuated by the pump from the deposition chamber. In case of fabrication of polymer nanocomposites, MAPLE targets are usually prepared as nano-colloids of the additives of interest in the initial polymer solutions. Mixing the components of different nature, organic polymers and inorganic dopants, in the same target at a certain proportion and exposing them to the same laser beam not necessarily brings good quality nano-composite films. The laser pulse energy and wavelength cannot be optimized for each component individually. Also, the mixing proportion in the composite film is dictated by the initial proportion of the target and thus cannot be changed in the process. These limitations were removed in the recently proposed method of multi-beam and multi-target deposition (in its doublebeam/ dual-target variation) using a MAPLE polymer target and one inorganic target, each being concurrently exposed to laser beams of different wavelengths.5-14 Using the method, nano-composite films of polymer poly(methyl methacrylate) known as PMMA doped with a rare earth (RE) inorganic upconversion phosphor compounds were prepared. Also, a nano-composite film of thermoelectric film of inorganic aluminum-doped ZnO known as AZO was impregnated with PMMA nano-fillers with the purpose of improving electrical conductivity and thermoelectric performance.10, 14 The polymer target was a frozen (to a temperature of liquid nitrogen) PMMA solution in chlorobenzene exposed to a 1064- nm laser beam from a Q-switched Nd:YAG pulsed laser. The inorganic targets were the pellets made of the compressed micro-powders of highly efficient RE-doped NaYF4 or the sintered powder of AZO concurrently ablated with the

Fabricating and Characterizing Physical Properties of Electrospun Polypeptide-based Nanofibers

NASA Astrophysics Data System (ADS)

Khadka, Dhan Bahadur

This dissertation has aimed to fabricate polypeptide based biomaterial and characterize physical properties. Electrospinning is used as a tool for the sample fabrication. Project focused on determining the feasibility of electrospinning of certain synthetic polypeptides and certain elastin-like peptides from aqueous feedstocks and to characterize physical properties of polymer aqueous solution, cast film and spun fibers and fiber mats. The research involves peptide design, polymer electrospinning, fibers crosslinking, determining the extent of crosslinking, fibers protease degradation study, fibers stability and self-organization analysis, structure and composition determination by various spectroscopy and microscopy techniques and characterization of mechanical properties of individual suspended fibers. Fiber mats of a synthetic cationic polypeptide poly(L-ornithine) (PLO) and an anionic co-polypeptide of L-glutamic acid and L-tyrosine (PLEY) of defined composition have been produced by electrospinning. Fibers were obtained from polymer aqueous solution at concentrations of 20-45% (w/v) in PLO and at concentrations of 20-60% (w/v) in PLEY. Applied voltage and spinneret-collector distance were also found to influence polymer spinnability and fibers morphology. Oriented fibers were obtained by parallel electrodes geometry. Fiber diameter and morphology was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). PLO fibers exposed on glutaraldehyde (GTA) vapor rendered fiber mats water-insoluble. A common chemical reagent, carbodiimide was used to crosslink PLEY fibers. Fiber solubility in aqueous solution varied as a function of crosslinking time and crosslinker concentration. Crosslink density has been quantified by a visible-wavelength dye-based method. Degradation of crosslinked fibers by different proteases has been demonstrated. Investigation of crosslinked PLEY fibers has provided insight into the mechanisms of stability at different pH values. Variations in fiber morphology, elemental composition and stability have been studied by microscopy and energy-dispersive X-ray spectroscopy (EDX), following the treatment of samples at different pH values in the 2-12 range. Fiber stability has been interpreted with reference to the pH dependence of the UV absorbance and fluorescence of PLEY chains in solution. The data show that fiber stability is crucially dependent on the extent of side chain ionization, even after crosslinking. Self-organization kinetics of electrospun PLO and PLEY fibers during solvent annealing has been studied. After being crosslinked in situ , fibers were annealed in water at 22 °C. Analysis by Fourier transform infrared spectroscopy (FTIR) has revealed that annealing involved fiber restructuring with an overall time constant of 29 min for PLO and 63 min for PLEY, and that changes in the distribution of polymer conformations occurred during the first 13 min of annealing. There was a substantial decrease in the amount of Na+ bound to PLEY fibers during annealing. Kinetic modeling has indicated that two parallel pathways better account for the annealing trajectory than a single pathway with multiple transition states. Taken together, the results will advance the rational design of polypeptides for peptide-based materials, especially materials prepared by electrospinning. It is believed that this research will increase basic knowledge of polymer electrospinning and advance the development of electrospun materials, especially in medicine and biotechnology. The study has yielded two advances on previous work in the area: avoidance of an animal source of peptides and avoidance of inorganic solvent. The present results thus advance the growing field of peptide-based materials. Non-woven electrospun fiber mats made of polypeptides are increasingly considered attractive for basic research and technology development in biotechnology, medicine and other areas. (Abstract shortened by UMI.)

Thermally Activated Delayed Fluorescence in Polymers: A New Route toward Highly Efficient Solution Processable OLEDs.

PubMed

Nikolaenko, Andrey E; Cass, Michael; Bourcet, Florence; Mohamad, David; Roberts, Matthew

2015-11-25

Efficient intermonomer thermally activated delayed fluorescence is demonstrated for the first time, opening a new route to achieving high-efficiency solution processable polymer light-emitting device materials. External quantum efficiency (EQE) of up to 10% is achieved in a simple fully solution-processed device structure, and routes for further EQE improvement identified. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

21 CFR 175.270 - Poly(vinyl fluoride) resins.

Code of Federal Regulations, 2013 CFR

2013-04-01

... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b) of...

21 CFR 175.270 - Poly(vinyl fluoride) resins.

Code of Federal Regulations, 2012 CFR

2012-04-01

... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b) of...

Hydrodynamically Coupled Brownian Dynamics: A coarse-grain particle-based Brownian dynamics technique with hydrodynamic interactions for modeling self-developing flow of polymer solutions

NASA Astrophysics Data System (ADS)

Ahuja, V. R.; van der Gucht, J.; Briels, W. J.

2018-01-01

We present a novel coarse-grain particle-based simulation technique for modeling self-developing flow of dilute and semi-dilute polymer solutions. The central idea in this paper is the two-way coupling between a mesoscopic polymer model and a phenomenological fluid model. As our polymer model, we choose Responsive Particle Dynamics (RaPiD), a Brownian dynamics method, which formulates the so-called "conservative" and "transient" pair-potentials through which the polymers interact besides experiencing random forces in accordance with the fluctuation dissipation theorem. In addition to these interactions, our polymer blobs are also influenced by the background solvent velocity field, which we calculate by solving the Navier-Stokes equation discretized on a moving grid of fluid blobs using the Smoothed Particle Hydrodynamics (SPH) technique. While the polymers experience this frictional force opposing their motion relative to the background flow field, our fluid blobs also in turn are influenced by the motion of the polymers through an interaction term. This makes our technique a two-way coupling algorithm. We have constructed this interaction term in such a way that momentum is conserved locally, thereby preserving long range hydrodynamics. Furthermore, we have derived pairwise fluctuation terms for the velocities of the fluid blobs using the Fokker-Planck equation, which have been alternatively derived using the General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC) approach in Smoothed Dissipative Particle Dynamics (SDPD) literature. These velocity fluctuations for the fluid may be incorporated into the velocity updates for our fluid blobs to obtain a thermodynamically consistent distribution of velocities. In cases where these fluctuations are insignificant, however, these additional terms may well be dropped out as they are in a standard SPH simulation. We have applied our technique to study the rheology of two different concentrations of our model linear polymer solutions. The results show that the polymers and the fluid are coupled very well with each other, showing no lag between their velocities. Furthermore, our results show non-Newtonian shear thinning and the characteristic flattening of the Poiseuille flow profile typically observed for polymer solutions.

Hydrodynamically Coupled Brownian Dynamics: A coarse-grain particle-based Brownian dynamics technique with hydrodynamic interactions for modeling self-developing flow of polymer solutions.

PubMed

Ahuja, V R; van der Gucht, J; Briels, W J

2018-01-21

We present a novel coarse-grain particle-based simulation technique for modeling self-developing flow of dilute and semi-dilute polymer solutions. The central idea in this paper is the two-way coupling between a mesoscopic polymer model and a phenomenological fluid model. As our polymer model, we choose Responsive Particle Dynamics (RaPiD), a Brownian dynamics method, which formulates the so-called "conservative" and "transient" pair-potentials through which the polymers interact besides experiencing random forces in accordance with the fluctuation dissipation theorem. In addition to these interactions, our polymer blobs are also influenced by the background solvent velocity field, which we calculate by solving the Navier-Stokes equation discretized on a moving grid of fluid blobs using the Smoothed Particle Hydrodynamics (SPH) technique. While the polymers experience this frictional force opposing their motion relative to the background flow field, our fluid blobs also in turn are influenced by the motion of the polymers through an interaction term. This makes our technique a two-way coupling algorithm. We have constructed this interaction term in such a way that momentum is conserved locally, thereby preserving long range hydrodynamics. Furthermore, we have derived pairwise fluctuation terms for the velocities of the fluid blobs using the Fokker-Planck equation, which have been alternatively derived using the General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC) approach in Smoothed Dissipative Particle Dynamics (SDPD) literature. These velocity fluctuations for the fluid may be incorporated into the velocity updates for our fluid blobs to obtain a thermodynamically consistent distribution of velocities. In cases where these fluctuations are insignificant, however, these additional terms may well be dropped out as they are in a standard SPH simulation. We have applied our technique to study the rheology of two different concentrations of our model linear polymer solutions. The results show that the polymers and the fluid are coupled very well with each other, showing no lag between their velocities. Furthermore, our results show non-Newtonian shear thinning and the characteristic flattening of the Poiseuille flow profile typically observed for polymer solutions.

Coloring a Superabsorbent Polymer with Metal Ions: An Undergraduate Chemistry Experiment

ERIC Educational Resources Information Center

Yaung, Jing-Fun; Chen, Yueh-Huey

2009-01-01

A novel undergraduate chemistry experiment involving superabsorbent polymers commonly used in diapers and other personal care products is described. Students observe the removal of divalent transition-metal ions from aqueous solutions by the polymers. With the procedures provided, students are able to color the superabsorbent polymers with metal…

Inorganic nanostructure-organic polymer heterostructures useful for thermoelectric devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

See, Kevin C.; Urban, Jeffrey J.; Segalman, Rachel A.

The present invention provides for an inorganic nanostructure-organic polymer heterostructure, useful as a thermoelectric composite material, comprising (a) an inorganic nanostructure, and (b) an electrically conductive organic polymer disposed on the inorganic nanostructure. Both the inorganic nanostructure and the electrically conductive organic polymer are solution-processable.

21 CFR 177.2210 - Ethylene polymer, chloro-sulfonated.

Code of Federal Regulations, 2011 CFR

2011-04-01

...) Ethylene polymer, chloro-sulfonated is produced by chloro-sulfonation of a carbon tetrachloride solution of... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene polymer, chloro-sulfonated. 177.2210... as Components of Articles Intended for Repeated Use § 177.2210 Ethylene polymer, chloro-sulfonated...

Electrophoretic mobilities of counterions and a polymer in cylindrical pores

PubMed Central

Singh, Sunil P.; Muthukumar, M.

2014-01-01

We have simulated the transport properties of a uniformly charged flexible polymer chain and its counterions confined inside cylindrical nanopores under an external electric field. The hydrodynamic interaction is treated by describing the solvent molecules explicitly with the multiparticle collision dynamics method. The chain consisting of charged monomers and the counterions interact electrostatically with themselves and with the external electric field. We find rich behavior of the counterions around the polymer under confinement in the presence of the external electric field. The mobility of the counterions is heterogeneous depending on their location relative to the polymer. The adsorption isotherm of the counterions on the polymer depends nonlinearly on the electric field. As a result, the effective charge of the polymer exhibits a sigmoidal dependence on the electric field. This in turn leads to a nascent nonlinearity in the chain stretching and electrophoretic mobility of the polymer in terms of their dependence on the electric field. The product of the electric field and the effective polymer charge is found to be the key variable to unify our simulation data for various polymer lengths. Chain extension and the electrophoretic mobility show sigmoidal dependence on the electric field, with crossovers from the linear response regime to the nonlinear regime and then to the saturation regime. The mobility of adsorbed counterions is nonmonotonic with the electric field. For weaker and moderate fields, the adsorbed counterions move with the polymer and at higher fields they move opposite to the polymer's direction. We find that the effective charge and the mobility of the polymer decrease with a decrease in the pore radius. PMID:25240366

Development of PVA/gelatin nanofibrous scaffolds for Tissue Engineering via electrospinning

NASA Astrophysics Data System (ADS)

Perez-Puyana, V.; Jiménez-Rosado, M.; Romero, A.; Guerrero, A.

2018-03-01

The electrospinning process is an emerging and relatively easy technique to prepare three-dimensional matrices with micro- and nanofibers. To achieve it, aqueous polymer solutions from synthetic or natural polymers are used. PVA was selected as polymer and gelatin because of its biocompatibility and biodegradability. A complete characterization of the polymeric solutions (density, surface tension, etc) was previously performed. Subsequently, a standard electrospinning process (15 kV, 0.4 ml h-1 and 10 cm) was carried out to obtain scaffolds. The influence of the polymer concentration and the protein addition was observed by performing FTIR analyses and studied by analyzing the water contact angle and SEM images.

Action of polysaccharides of similar average mass but differing molecular volume and charge on fluid drainage through synovial interstitium in rabbit knees

PubMed Central

Scott, D; Coleman, P J; Mason, R M; Levick, J R

2000-01-01

Hyaluronan (HA), an anionic polysaccharide of synovial fluid, attenuates fluid loss from joints as joint pressure is raised (‘outflow buffering’). The buffering is thought to depend on the expanded molecular domain of the polymer, which causes reflection by synovial extracellular matrix, leading to flow-dependent concentration polarization. We therefore assessed the effects of polysaccharides of differing average molecular volume and charge. Trans-synovial fluid drainage(Q̇s) was measured at controlled joint fluid pressure (Pj) in knees of anaesthetized rabbits. The joints were infused with polydisperse HA of weight-average mass 2100 kDa (4 mg ml−1, n = 17), with polydisperse neutral dextran of similar average mass (2000 kDa; n = 7) or with Ringer solution vehicle (n = 2). The role of polymer charge was assessed by infusions of neutral or sulphated dextran of average molecular mass 500 kDa (n = 6). When HA was present, Q̇s increased little with pressure, forming a virtual plateau of ∼4 μl min−1 from 10 to 25 cmH2O. Neutral dextran 2000 failed to replicate this effect. Instead, Q̇s increased steeply with Pj, reaching eight times the HA value by 20 cmH2O (P = 0.0001, ANOVA). Dextran 2000 reduced flows in comparison with Ringer solution. Analysis of the aspirated joint fluid showed that 31 ± 0.07 % (s.e.m.) of dextran 2000 in the filtrand was reflected by synovium, compared with ≥ 79 % for HA. The viscometric molecular radius of the dextran, ∼31 nm, was smaller than that of HA (101–181 nm), as was its osmotic pressure. Anionic dextran 500 failed to buffer fluid drainage, but it reduced fluid escape and synovial conductance dQ̇s/dPj more than neutral dextran 500 (P < 0.0001, ANOVA). The anionic charge increased the molecular volume and viscosity of dextran 500. The results support the hypothesis that polymer molecular volume influences its reflection by interstitial matrix and outflow buffering. Polymer charge influences flow through an effect on viscosity and possibly electrostatic interactions with negatively charged interstitial matrix. PMID:11060134

Thermal method for cleaning polymer quenching media

NASA Astrophysics Data System (ADS)

Sverdlin, A. V.; Blackwood, R.; Totten, G. E.

1996-06-01

Aqueous solutions of polymers are used for heat treatment, mainly for quenching steels. The most popular and universally used are quenching liquids of the UCON A, E, XT types based on various polyalkylene glycols. In the course of operation these liquids are contaminated by salts retained on the surface of the parts after their heating in salt baths, by ions of heavy metals present in the solution, etc. The paper is devoted to the most popular method for cleaning polymer quenching media, namely, the method of thermal separation.

Lower Critical Solubility Temperature Behavior in Membranes Formed from a 2-(2-Methoxyethoxy)ethoxy-Containing Polyphosphazene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, F.F.; Lash, R.P.

A phosphazene polymer with three pendant groups was synthesized and characterized as a membrane material. Substitution of the phosphazene with 64% 2-(2-methoxyethoxy)ethanol (MEE), 27% 4-methoxyphenol, and 9% 2-allyphenol yielded a hydrophilic elastomer with considerable flow at room temperature. Solution behavior showed significant aging effects where, using fresh solutions, membranes could not cast on porous ceramic supports (0.2-micron pore size) without significant polymer penetration into the pores. Solutions aged for two weeks were found to readily penetrate into the pores of the ceramic support. Analysis of fresh and aged solutions by laser light scattering showed significant loss in molecular weight withmore » time. Pervaporation of water-dye solutions using dimensionally stabilized membranes revealed in inverse correlation between flux and temperature, suggesting thermally induced morphological changes within the polymer. This polymer was found to exhibit, in the bulk state, lower critical solubility temperature (LCST) behavior where the material becomes less hydrophilic with increasing temperature. LCST behavior was probed thermally and gravimetrically and has been attributed to the anomalous pervaporation results. The degree to which LCST effects membrane transport was influenced by changes in the crosslink density and permeate side pressure.« less

Anisotropic membranes for gas separation

DOEpatents

Gollan, Arye Z.

1987-01-01

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7.degree.-25.degree. C. and then air dried at ambient temperature, typically 10.degree.-30.degree. C.

An accurate coarse-grained model for chitosan polysaccharides in aqueous solution.

PubMed

Tsereteli, Levan; Grafmüller, Andrea

2017-01-01

Computational models can provide detailed information about molecular conformations and interactions in solution, which is currently inaccessible by other means in many cases. Here we describe an efficient and precise coarse-grained model for long polysaccharides in aqueous solution at different physico-chemical conditions such as pH and ionic strength. The Model is carefully constructed based on all-atom simulations of small saccharides and metadynamics sampling of the dihedral angles in the glycosidic links, which represent the most flexible degrees of freedom of the polysaccharides. The model is validated against experimental data for Chitosan molecules in solution with various degree of deacetylation, and is shown to closely reproduce the available experimental data. For long polymers, subtle differences of the free energy maps of the glycosidic links are found to significantly affect the measurable polymer properties. Therefore, for titratable monomers the free energy maps of the corresponding links are updated according to the current charge of the monomers. We then characterize the microscopic and mesoscopic structural properties of large chitosan polysaccharides in solution for a wide range of solvent pH and ionic strength, and investigate the effect of polymer length and degree and pattern of deacetylation on the polymer properties.

An accurate coarse-grained model for chitosan polysaccharides in aqueous solution

PubMed Central

Tsereteli, Levan

2017-01-01

Computational models can provide detailed information about molecular conformations and interactions in solution, which is currently inaccessible by other means in many cases. Here we describe an efficient and precise coarse-grained model for long polysaccharides in aqueous solution at different physico-chemical conditions such as pH and ionic strength. The Model is carefully constructed based on all-atom simulations of small saccharides and metadynamics sampling of the dihedral angles in the glycosidic links, which represent the most flexible degrees of freedom of the polysaccharides. The model is validated against experimental data for Chitosan molecules in solution with various degree of deacetylation, and is shown to closely reproduce the available experimental data. For long polymers, subtle differences of the free energy maps of the glycosidic links are found to significantly affect the measurable polymer properties. Therefore, for titratable monomers the free energy maps of the corresponding links are updated according to the current charge of the monomers. We then characterize the microscopic and mesoscopic structural properties of large chitosan polysaccharides in solution for a wide range of solvent pH and ionic strength, and investigate the effect of polymer length and degree and pattern of deacetylation on the polymer properties. PMID:28732036

Flory-type theories of polymer chains under different external stimuli

NASA Astrophysics Data System (ADS)

Budkov, Yu A.; Kiselev, M. G.

2018-01-01

In this Review, we present a critical analysis of various applications of the Flory-type theories to a theoretical description of the conformational behavior of single polymer chains in dilute polymer solutions under a few external stimuli. Different theoretical models of flexible polymer chains in the supercritical fluid are discussed and analysed. Different points of view on the conformational behavior of the polymer chain near the liquid-gas transition critical point of the solvent are presented. A theoretical description of the co-solvent-induced coil-globule transitions within the implicit-solvent-explicit-co-solvent models is discussed. Several explicit-solvent-explicit-co-solvent theoretical models of the coil-to-globule-to-coil transition of the polymer chain in a mixture of good solvents (co-nonsolvency) are analysed and compared with each other. Finally, a new theoretical model of the conformational behavior of the dielectric polymer chain under the external constant electric field in the dilute polymer solution with an explicit account for the many-body dipole correlations is discussed. The polymer chain collapse induced by many-body dipole correlations of monomers in the context of statistical thermodynamics of dielectric polymers is analysed.

Dielectric dispersion of short single-stranded DNA in aqueous solutions with and without added salt.

PubMed

Katsumoto, Yoichi; Omori, Shinji; Yamamoto, Daisuke; Yasuda, Akio; Asami, Koji

2007-01-01

Dielectric spectroscopy measurements were performed for aqueous solutions of short single-stranded DNA with 30 to 120 bases of thymine over a frequency range of 10;{5} to 10;{8}Hz . Dielectric dispersion was found to include two relaxation processes in the ranges from 10;{5} to 10;{6} and from 10;{6} to 10;{8}Hz , respectively, with the latter mainly discussed in this study. The dielectric increment and the relaxation time of the high-frequency relaxation of DNA in solutions without added salt exhibited concentration and polymer-length dependences eventually identical to those for dilute polyion solutions described in previous studies. For solutions with added salt, on the other hand, those dielectric parameters were independent of salt concentration up to a certain critical value and started to decrease with further increasing salt concentration. This critical behavior is well explained by our newly extended cell model that takes into account the spatial distribution of loosely bound counterions around DNA molecules as a function of salt concentration.

Synthesis and supramolecular assembly of biomimetic polymers

NASA Astrophysics Data System (ADS)

Marciel, Amanda Brittany

A grand challenge in materials chemistry is the synthesis of macromolecules and polymers with precise shapes and architectures. Polymer microstructure and architecture strongly affect the resulting functionality of advanced materials, yet understanding the static and dynamic properties of these complex macromolecules in bulk has been difficult due to their inherit polydispersity. Single molecule studies have provided a wealth of information on linear flexible and semi-flexible polymers in dilute solutions. However, few investigations have focused on industrially relevant complex topologies (e.g., star, comb, hyperbranched polymers) in industrially relevant solution conditions (e.g., semi-dilute, concentrated). Therefore, from this perspective there is a strong need to synthesize precision complex architectures for bulk studies as well as complex architectures compatible with current single molecule techniques to study static and dynamic polymer properties. In this way, we developed a hybrid synthetic strategy to produce branched polymer architectures based on chemically modified DNA. Overall, this approach enables control of backbone length and flexibility, as well as branch grafting density and chemical identity. We utilized a two-step scheme based on enzymatic incorporation of non-natural nucleotides containing bioorthogonal dibenzocyclooctyne (DBCO) functional groups along the main polymer backbone, followed by copper-free "click" chemistry to graft synthetic polymer branches or oligonucleotide branches to the DNA backbone, thereby allowing for the synthesis of a variety of polymer architectures, including three-arm stars, H-polymers, graft block copolymers, and comb polymers for materials assembly and single molecule studies. Bulk materials properties are also affected by industrial processing conditions that alter polymer morphology. Therefore, in an alternative strategy we developed a microfluidic-based approach to assemble highly aligned synthetic oligopeptides nanostructures using microscale extensional flows. This strategy enabled reproducible, reliable fabrication of aligned hierarchical constructs that do not form spontaneously in solution. In this way, fluidic-directed assembly of supramolecular structures allows for unprecedented manipulation at the nano- and mesoscale, which has the potential to provide rapid and efficient control of functional materials properties.

Development of injectable thermogelling chitosan-inorganic phosphate solutions for biomedical applications.

PubMed

Nair, Lakshmi S; Starnes, Trevor; Ko, Jia-Wei Kevin; Laurencin, Cato T

2007-12-01

Thermosetting polymers are attractive candidates for biomedical applications as noninvasive therapeutic delivery vehicles. In the present study, the feasibility of developing a neutral physiological temperature setting injectable formulation based on chitosan and an inorganic phosphate salt have been demonstrated. The in situ gelling system was developed by adding different concentrations of ammonium hydrogen phosphate (AHP) to chitosan solution. The resulting solutions have pH in the range of approximately 7-7.2. The gelling time of the chitosan-AHP solution was determined by incubating the solutions at 37 degrees C. Depending on the concentrations of AHP added, the gelling time varied from 5 min to 30 h at 37 degrees C. Addition of various diluents to chitosan-AHP solution did not significantly change the gelling time of the solutions. The gels were found to be cytocompatible as evidenced from in vitro cytocompatibility evaluation using MC3T3-E1 mouse osteoblast like cells. The feasibility of using the gels as a stem cell carrier vehicle as well as a macromolecular delivery vehicle has been demonstrated.

A study of diazonium couplings with aromatic nucleophiles both in solution and on a polymer surface

NASA Astrophysics Data System (ADS)

Chng, Shuyun; Parker, Emily M.; Griffiths, Jon-Paul; Moloney, Mark G.; Wu, Linda Y. L.

2017-04-01

Diazonium coupling is a technique finding wider application to materials and biological science, for hybridization and linking processes, and for the construction of responsive surface functionality. For this reason, detailed examination of solution and surface processes was warranted, and results of such a study are reported here. The modification of polystyrene surfaces was examined as a model, and the process compared to a solution mimic using N,N-dimethylaniline. It was confirmed that solution and solid surface reactions proceed in a similar manner in terms of the chemical functionality generated, but with lower chemical efficiency and reaction times slower for the latter, in a reaction which was pH dependent. The solution process was shown to give only the trans-azo para- coupled products. Whilst there are clear similarities between the solution and surface chemistry, the efficiency of coupling at a surface is not necessarily replicated in the chemical yield of the mimicking solution processes, but nonetheless provides an alternative to other Click-type surface modifications. It should not be assumed that such couplings occur with quantitative efficiency at the surface.

Derivatizing weak polyelectrolytes--solution properties, self-aggregation, and association with anionic surfaces of hydrophobically modified poly(ethylene imine).

PubMed

Griffiths, Peter C; Paul, Alison; Fallis, Ian A; Wellappili, Champa; Murphy, Damien M; Jenkins, Robert; Waters, Sarah J; Nilmini, Renuka; Heenan, Richard K; King, Stephen M

2007-10-15

The physical properties of weak polyelectrolytes may be tailored via hydrophobic modification to exhibit useful properties under appropriate pH and ionic strength conditions as a consequence of the often inherently competing effects of electrostatics and hydrophobicity. Pulsed-gradient spin-echo NMR (PGSE-NMR), electron paramagnetic resonance (EPR), small-angle neutron scattering (SANS) surface tension, fluorescence, and pH titration have been used to examine the solution conformation and aggregation behavior of a series of hydrophobically modified hyperbranched poly(ethylene imine) (PEI) polymers in aqueous solution, and their interaction with sodium dodecylsulfate (SDS). PGSE-NMR gave a particularly insightful picture of the apparent molecular weight distribution. The presence of the hydrophobes led to a lower effective charge on the polymer at any given pH, compared to the (parent) nonmodified samples. Analysis of the SANS data showed that the propensity to form highly elliptical or rod-like aggregates at higher pHs, reflecting both the changes in protonation behavior induced by the hydrophobic modification and an hydrophobic interaction, but that these structures were disrupted with decreasing pH (increasing charge). The parent samples were not surface active yet the hydrophobically modified samples show pronounced surface activity and the presence of small hydrophobic domains. The surface activity increased with an increase in the degree of modification. On addition of SDS, the onset of the formation of polymer/surfactant complexes was insensitive to the degree of modification with the resultant PEI/SDS complexes resembling the size and shape of simple SDS micelles. Indeed, the presence of the SDS effectively nullifies the effects of the hydrophobe. Hydrophobic modification is therefore a viable option to tailor pH dependent properties, whose effects may be removed by the presence of surfactant.

Ethylcellulose film coating of guaifenesin-loaded pellets: A comprehensive evaluation of the manufacturing process to prevent drug migration.

PubMed

Melegari, Cecilia; Bertoni, Serena; Genovesi, Alberto; Hughes, Kevin; Rajabi-Siahboomi, Ali R; Passerini, Nadia; Albertini, Beatrice

2016-03-01

The aim of the research was to investigate the complete process of pellet production in a Wurster fluidized bed coater in order to determine the main factors affecting the migration phenomenon of a soluble API through the ethycellulose film coating (Surelease®) and hence the long-term stability of the controlled release pellets. Guaifenesin (GFN), as BCS class I model drug, was layered on sugar spheres using a binder-polymer solution containing the dissolved GFN. The drug loaded pellets were then coated with Surelease®. The influence of drug loading (4.5-20.0% w/w), curing conditions (40-60°C and dynamic-static equipment), coating level (12-20% theoretical weight gain) and composition of the binder-layering solution (hypromellose versus Na alginate) on process efficiency (RSDW%), GFN content uniformity (RSDC%), GFN solid state (DSC and XRD) and pellet release profiles was evaluated. The effectiveness of the Surelease film was strongly affected by the ability of GFN to cross the coating layer and to recrystallize on the pellet surface. Results indicated that this behaviour was dependent on the polymer used in the binder-layering solution. Using hypromellose as polymer, GFN recrystallized on the coated pellet surface at both drug loadings. The curing step was necessary to stabilize the film effectiveness at the higher drug loading. Increasing the coating level delayed but did not prevent the GFN diffusion. Replacing hypromellose with Na alginate, reduced the migration of GFN through the film to a negligible amount even after six months of storage and the curing step was not necessary to achieve stable controlled release profiles over storage. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies on the formation of polymeric nano-emulsions obtained via low-energy emulsification and their use as templates for drug delivery nanoparticle dispersions.

PubMed

Calderó, G; Montes, R; Llinàs, M; García-Celma, M J; Porras, M; Solans, C

2016-09-01

Ethylcellulose nanoparticles have been obtained from O/W nano-emulsions of the water/polyoxyethylene 10 oleyl ether/[ethyl acetate+4wt% ethylcellulose] system by low energy-energy emulsification at 25°C. Nano-emulsions with droplet sizes below 200nm and high kinetic stability were chosen for solubilising dexamethasone (DXM). Phase behaviour, conductivity and optical analysis studies of the system have evidenced for the first time that both, the polymer and the drug play a role on the structure of the aggregates formed along the emulsification path. Nano-emulsion formation may take place by both, phase inversion and self-emulsification. Spherical polymeric nanoparticles containing surfactant, showing sizes below 160nm have been obtained from the nano-emulsions by organic solvent evaporation. DXM loading in the nanoparticles was high (>90%). The release kinetics of nanoparticle dispersions with similar particle size and encapsulated DXM but different polymer to surfactant ratio were studied and compared to an aqueous DXM solution. Drug release from the nanoparticle dispersions was slower than from the aqueous solution. While the DXM solution showed a Fickian release pattern, the release behaviour from the nanoparticle dispersions was faster than that expected from a pure Fickian release. A coupled diffusion/relaxation model fitted the results very well, suggesting that polymer chains undergo conformational changes enhancing drug release. The contribution of diffusion and relaxation to drug transport in the nanoparticle dispersions depended on their composition and release time. Surfactant micelles present in the nanoparticle dispersion may exert a mild reservoir effect. The small particle size and the prolonged DXM release provided by the ethylcellulose nanoparticle dispersions make them suitable vehicles for controlled drug delivery applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Soft interactions and volume exclusion by polymeric crowders can stabilize or destabilize transient structure in disordered proteins depending on polymer concentration.

PubMed

Rusinga, Farai I; Weis, David D

2017-08-01

The effects of macromolecular crowding on the transient structure of intrinsically disordered proteins is not well-understood. Crowding by biological molecules inside cells could modulate transient structure and alter IDP function. Volume exclusion theory and observations of structured proteins suggest that IDP transient structure would be stabilized by macromolecular crowding. Amide hydrogen exchange (HX) of IDPs in highly concentrated polymer solutions would provide valuable insights into IDP transient structure under crowded conditions. Here, we have used mass spectrometry to measure HX by a transiently helical random coil domain of the activator of thyroid and retinoid receptor (ACTR) in solutions containing 300 g L -1 and 400 g L -1 of Ficoll, a synthetic polysaccharide, using a recently-developed strong cation exchange-based cleanup method [Rusinga, et al., Anal Chem 2017;89:1275-1282]. Transiently helical regions of ACTR exchanged faster in 300 g L -1 Ficoll than in dilute buffer. In contrast, one transient helix exchanged more slowly in 400 g L -1 Ficoll. Nonspecific interactions destabilize ACTR helicity in 300 g L -1 Ficoll because ACTR engages with the Ficoll polymer mesh. In contrast, 400 g L -1 Ficoll is a semi-dilute solution where ACTR cannot engage the Ficoll mesh. At this higher concentration, volume exclusion stabilizes ACTR helicity because ACTR is compacted in interstitial spaces between Ficoll molecules. Our results suggest that the interplay between nonspecific interactions and volume exclusion in different cellular compartments could modulate IDP function by altering the stability of IDP transient structures. Proteins 2017; 85:1468-1479. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Cell separations and the demixing of aqueous two phase polymer solutions in microgravity

NASA Technical Reports Server (NTRS)

Brooks, Donald E.; Bamberger, Stephan; Harris, J. M.; Van Alstine, James M.

1991-01-01

Partition in phase separated aqueous polymer solutions is a cell separation procedure thought to be adversely influenced by gravity. In preparation for performing cell partitioning experiments in space, and to provide general information concerning the demixing of immiscible liquids in low gravity, a series of phase separated aqueous polymer solutions have been flown on two shuttle flights. Fluorocarbon oil and water emulsions were also flown on the second flight. The aqueous polymer emulsions, which in one g demix largely by sedimentation and convection due to the density differences between the phases, demixed more slowly than on the ground and the final disposition of the phases was determined by the wetting of the container wall by the phases. The demixing behavior and kinetics were influenced by the phase volume ratio, physical properties of the systems and chamber wall interaction. The average domain size increased linearly with time as the systems demixed.

Xanthan Gum-a lyotropic, liquid crystalline polymer and its properties as a suspending agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salamone, J.C.; Clough, S.B.; Jamison, D.E.

1982-08-01

Studies a variety of xanthan solutions of various polymer concentrations in the presence and absence of various salts under a polarized light microscope (100X) in order to test xanthan gum for liquid crystalline order. Xanthan gum, a polysaccharide used in drilling fluids and in tertiary recovery, has relatively stable viscosity properties as a function of salt concentration, pH, temperature, and shear degradation. With solutions from 2 to 10% (wt/vol) xanthan gum in distilled water at room temperature, birefringent, ordered domains were observed at 10% concentration, with a decrease in birefringence as the polymer concentration decreased. When the xanthan solution ismore » sheared between a glass slide and a cover slip, the optic axis (chain direction) aligns using the shear direction (as determined by the colors displayed using a first-order red plate). Examines liquid crystalline behavior of other naturally occurring polymers.« less

Flow-enhanced solution printing of all-polymer solar cells

DOE PAGES

Diao, Ying; Zhou, Yan; Kurosawa, Tadanori; ...

2015-08-12

Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a similar to 90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhancedmore » all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. However, we expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.« less

Flow-enhanced solution printing of all-polymer solar cells

PubMed Central

Diao, Ying; Zhou, Yan; Kurosawa, Tadanori; Shaw, Leo; Wang, Cheng; Park, Steve; Guo, Yikun; Reinspach, Julia A.; Gu, Kevin; Gu, Xiaodan; Tee, Benjamin C. K.; Pang, Changhyun; Yan, Hongping; Zhao, Dahui; Toney, Michael F.; Mannsfeld, Stefan C. B.; Bao, Zhenan

2015-01-01

Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility. PMID:26264528

Coated foams, preparation, uses and articles

DOEpatents

Duchane, D.V.; Barthell, B.L.

1982-10-21

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tension of the polymer solution used to coat are all very important to the coating.