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Sample records for adsorbed polymer chains

  1. Untangleing the effects of chain rigidity on the structure and dynamics of strongly adsorbed polymer melts

    DOE PAGES

    Carrillo, Jan-Michael Y.; Cheng, Shiwang; Kumar, Rajeev; ...

    2015-06-11

    Here, we present a detailed analysis of coarse-grained molecular dynamics simulations of semiflexible polymer melts in contact with a strongly adsorbing substrate. We have characterized the segments in the interfacial layer by counting the number of trains, loops, tails and unadsorbed segments. For more rigid chains, a tail and an adsorbed segment (a train) dominate while loops are more prevalent in more flexible chains. The tails exhibit a non-uniformly stretched conformation akin to the polydispersed pseudobrush envisioned by Guiselin. To probe the dynamics of the segments we computed the layer z-resolved intermediate coherent collective dynamics structure factor, S(q, t, z),more » mean-square displacement of segments, and the 2nd Legendre polynomial of the time-autocorrelation of unit bond vectors, 2[ni(t,z)•ni(0,z)]>. Our results show that segmental dynamics is slower for stiffer chains and there is a strong correlation between the structure and dynamics in the interfacial layer. There is no glassy layer, and the slowing down in dynamics of stiffer chains in the adsorbed region can be attributed to the densification and the more persistent layering of segments.« less

  2. Untangleing the effects of chain rigidity on the structure and dynamics of strongly adsorbed polymer melts

    SciTech Connect

    Carrillo, Jan-Michael Y.; Cheng, Shiwang; Kumar, Rajeev; Goswami, Monojoy; Sokolov, Alexei P; Sumpter, Bobby G.

    2015-06-11

    Here, we present a detailed analysis of coarse-grained molecular dynamics simulations of semiflexible polymer melts in contact with a strongly adsorbing substrate. We have characterized the segments in the interfacial layer by counting the number of trains, loops, tails and unadsorbed segments. For more rigid chains, a tail and an adsorbed segment (a train) dominate while loops are more prevalent in more flexible chains. The tails exhibit a non-uniformly stretched conformation akin to the polydispersed pseudobrush envisioned by Guiselin. To probe the dynamics of the segments we computed the layer z-resolved intermediate coherent collective dynamics structure factor, S(q, t, z), mean-square displacement of segments, and the 2nd Legendre polynomial of the time-autocorrelation of unit bond vectors, 2[ni(t,z)•ni(0,z)]>. Our results show that segmental dynamics is slower for stiffer chains and there is a strong correlation between the structure and dynamics in the interfacial layer. There is no glassy layer, and the slowing down in dynamics of stiffer chains in the adsorbed region can be attributed to the densification and the more persistent layering of segments.

  3. Concentration and saturation effects of tethered polymer chains on adsorbing surfaces

    NASA Astrophysics Data System (ADS)

    Descas, Radu; Sommer, Jens-Uwe; Blumen, Alexander

    2006-12-01

    We consider end-grafted chains at an adsorbing surface under good solvent conditions using Monte Carlo simulations and scaling arguments. Grafting of chains allows us to fix the surface concentration and to study a wide range of surface concentrations from the undersaturated state of the surface up to the brushlike regime. The average extension of single chains in the direction parallel and perpendicular to the surface is analyzed using scaling arguments for the two-dimensional semidilute surface state according to Bouchaud and Daoud [J. Phys. (Paris) 48, 1991 (1987)]. We find good agreement with the scaling predictions for the scaling in the direction parallel to the surface and for surface concentrations much below the saturation concentration (dense packing of adsorption blobs). Increasing the grafting density we study the saturation effects and the oversaturation of the adsorption layer. In order to account for the effect of excluded volume on the adsorption free energy we introduce a new scaling variable related with the saturation concentration of the adsorption layer (saturation scaling). We show that the decrease of the single chain order parameter (the fraction of adsorbed monomers on the surface) with increasing concentration, being constant in the ideal semidilute surface state, is properly described by saturation scaling only. Furthermore, the simulation results for the chains' extension from higher surface concentrations up to the oversaturated state support the new scaling approach. The oversaturated state can be understood using a geometrical model which assumes a brushlike layer on top of a saturated adsorption layer. We provide evidence that adsorbed polymer layers are very sensitive to saturation effects, which start to influence the semidilute surface scaling even much below the saturation threshold.

  4. Dynamics of adsorbed polymers on attractive homogeneous surfaces

    PubMed Central

    Yang, Qing-Hui; Luo, Meng-Bo

    2016-01-01

    Dynamic behaviors of polymer chains adsorbed on an attractive, homogeneous surface are studied by using dynamic Monte Carlo simulations. The translational diffusion coefficient Dxy parallel to the surface decreases as the intra-polymer attraction strength EPP or the polymer-surface attraction strength EPS increases. The rotational relaxation time τR increases with EPS, but the dependence of τR on EPP is dependent on the adsorption state of the polymer. We find that τR decreases with increasing EPP for a partially adsorbed polymer but it increases with EPP for a fully adsorbed polymer. Scaling relations Dxy ~ N−α and τR ~ Nβ are found for long polymers. The scaling exponent α is independent of EPS for long polymers but increases with EPP from α = 1.06 at EPP = 0. While β ≈ 2.7 is also roughly independent of EPS for the adsorbed polymer at EPP = 0, but β increases with EPS at EPP > 0. Moreover, we find that β always decreases with increasing EPP. Our results reveal different effects of the attractive surface on the diffusion and rotation of adsorbed polymers. PMID:27849002

  5. Structure and dynamics of highly adsorbed semiflexible polymer melts

    NASA Astrophysics Data System (ADS)

    Carrillo, Jan-Michael; Cheng, Shiwang; Kumar, Rajeev; Goswami, Monojoy; Sokolov, Alexie; Sumpter, Bobby

    2015-03-01

    We present a detailed analysis of coarse-grained molecular dynamics simulations of melts of semi-flexible polymer chains in the presence of an adsorbing substrate. For polymer chains located far from the substrate the chain conformations follow the worm-like chain model, in contrast to the reflected Gaussian conformation near the substrate. This is demonstrated in the chain center-of-mass distribution normal to the substrate and the probability of a polymer chain ends to be the closest to the substrate. Both quantities agree with Silberberg's derivation for an ideal chain in the presence of a reflecting wall. We characterized the adsorbed chains and counted the number of loops and tails. For stiff chains, a tail and an adsorbed segment dominate the chain conformation of the adsorbed layer. Also, the mean-square end-to-end distance normal to the substrate is proportional to the normal component of the mean-square end-to-end distance of the tails. The tails do not follow the worm-like chain model and exhibit a stretched conformation. This picture for the adsorbed layer is akin to the ``polydisperse pseudobrush'' envisioned by Guiselin. We probe the dynamics of the segments by calculating the layer (z-)resolved intermediate coherent collective dynamics structure factor, S(q,t,z), for q values equivalent to the bond length. The segment dynamics is slower for stiffer chains. In the adsorbed layer, dynamics is slowed down and can be described by two relaxation times. Department of Energy, Office of Science DE-AC05-00OR227.

  6. Monte Carlo lattice models for adsorbed polymer conformation

    NASA Technical Reports Server (NTRS)

    Good, B. S.

    1985-01-01

    The adhesion between a polymer film and a metal surface is of great technological interest. However, the prediction of adhesion and wear properties of polymer coated metals is quite difficult because a fundamental understanding of the polymer surface interaction does not yet exist. A computer model for the conformation of a polymer molecule adsorbed on a surface is discussed. The chain conformation is assumed to be described by a partially directed random walk on a three dimensional simple cubic lattice. An attractive surface potential is incorporated into the model through the use of a random walk step probability distribution that is anisotropic in the direction normal to the attractive surface. The effects of variations in potential characteristics are qualitatively included by varying both the degree of anisotropy of the step distribution and the range of the anisotropy. Polymer conformation is characterized by the average end to end distance, average radius of gyration, and average number of chain segments adsorbed on the surface.

  7. Molecular Weight Distribution Effects on the Structure of Strongly Adsorbed Polymers by Monte Carlo Simulation

    NASA Astrophysics Data System (ADS)

    Kuppa, Vikram

    2012-02-01

    Monte Carlo simulations are used to investigate the adsorption of polymers from solution onto strongly attractive, perfectly smooth substrates. Using a coarse-grained united atom model for freely rotating polymer chains, three systems with different polydispersities are studied. The structure of the adsorbed layers, exemplified by density profiles, bond orientation order parameters, radii of gyration, and distribution of the adsorbed chain fractions, is shown to be highly dependent on the molecular weight distribution of the polymer phase. The results for the more monodisperse polymer systems are qualitatively similar to experimental and theoretical investigations, but devolve from very different chain conformations and statistics. For the first time ever, equilibrium polymer adsorption on highly attractive surface is studied, with all molecules in the adsorbed layers demonstrated to be indistinguishable from each other. The ergodicity of states explored by the polymer chains is in contrast to the kinetically constrained viewpoint of irreversible adsorption, and the observed behavior is explained in the context of the competition between polymers to make contact with the surface.

  8. Molecular weight distribution effects on the structure of strongly adsorbed polymers by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Kuppa, Vikram K.

    2012-06-01

    Monte Carlo simulations are reported to study the structure of polymers adsorbed from solution onto strongly attractive, perfectly smooth substrates. Six systems spanning a range of molecular weight distributions are investigated with a coarse-grained united atom model for freely rotating chains. By employing a global replica exchange algorithm and topology altering Monte Carlo moves, a range of monomer-surface attraction from weak (0.27kT) to strong (4kT) is simultaneously explored. Thus for the first time ever, equilibrium polymer adsorption on highly attractive surfaces is studied, with all adsorbed molecules displaying similar properties and statistics. The architecture of the adsorbed layers, including density profiles, bond orientation order parameters, radii of gyration, and distribution of the adsorbed chain fractions, is shown to be highly dependent on the polydispersity of the polymer phase. The homology of polymer chains, and the ergodicity of states explored by the molecules is in contrast to the metastable, kinetically constrained paradigm of irreversible adsorption. The structure of more monodisperse systems is qualitatively similar to experimental results and theoretical predictions, but result from very different chain conformations and statistics. The polydispersity-dependent behavior is explained in the context of the competition between polymers to make contact with the surface.

  9. Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases

    PubMed Central

    Senses, Erkan; Faraone, Antonio; Akcora, Pinar

    2016-01-01

    Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites. PMID:27457056

  10. Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Faraone, Antonio; Akcora, Pinar

    2016-07-01

    Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites.

  11. Analytical phase diagrams for colloids and non-adsorbing polymer.

    PubMed

    Fleer, Gerard J; Tuinier, Remco

    2008-11-04

    We review the free-volume theory (FVT) of Lekkerkerker et al. [Europhys. Lett. 20 (1992) 559] for the phase behavior of colloids in the presence of non-adsorbing polymer and we extend this theory in several aspects: (i) We take the solvent into account as a separate component and show that the natural thermodynamic parameter for the polymer properties is the insertion work Pi(v), where Pi is the osmotic pressure of the (external) polymer solution and v the volume of a colloid particle. (ii) Curvature effects are included along the lines of Aarts et al. [J. Phys.: Condens. Matt. 14 (2002) 7551] but we find accurate simple power laws which simplify the mathematical procedure considerably. (iii) We find analytical forms for the first, second, and third derivatives of the grand potential, needed for the calculation of the colloid chemical potential, the pressure, gas-liquid critical points and the critical endpoint (cep), where the (stable) critical line ends and then coincides with the triple point. This cep determines the boundary condition for a stable liquid. We first apply these modifications to the so-called colloid limit, where the size ratio q(R)=R/a between the radius of gyration R of the polymer and the particle radius a is small. In this limit the binodal polymer concentrations are below overlap: the depletion thickness delta is nearly equal to R, and Pi can be approximated by the ideal (van't Hoff) law Pi=Pi(0)=phi/N, where phi is the polymer volume fraction and N the number of segments per chain. The results are close to those of the original Lekkerkerker theory. However, our analysis enables very simple analytical expressions for the polymer and colloid concentrations in the critical and triple points and along the binodals as a function of q(R). Also the position of the cep is found analytically. In order to make the model applicable to higher size ratio's q(R) (including the so-called protein limit where q(R)>1) further extensions are needed. We

  12. Removal of acutely hazardous pharmaceuticals from water using multi-template imprinted polymer adsorbent.

    PubMed

    Venkatesh, Avinash; Chopra, Nikita; Krupadam, Reddithota J

    2014-05-01

    Molecularly imprinted polymer adsorbent has been prepared to remove a group of recalcitrant and acutely hazardous (p-type) chemicals from water and wastewaters. The polymer adsorbent exhibited twofold higher adsorption capacity than the commercially used polystyrene divinylbenzene resin (XAD) and powdered activated carbon adsorbents. Higher adsorption capacity of the polymer adsorbent was explained on the basis of high specific surface area formed during molecular imprinting process. Freundlich isotherms drawn showed that the adsorption of p-type chemicals onto polymer adsorbent was kinetically faster than the other reference adsorbents. Matrix effect on adsorption of p-type chemicals was minimal, and also polymer adsorbent was amenable to regeneration by washing with water/methanol (3:1, v/v) solution. The polymer adsorbent was unaltered in its adsorption capacity up to 10 cycles of adsorption and desorption, which will be more desirable in cost reduction of treatment compared with single-time-use activated carbon.

  13. Natural material adsorbed onto a polymer to enhance immune function

    PubMed Central

    Reinaque, Ana Paula Barcelos; França, Eduardo Luzía; Scherer, Edson Fredulin; Côrtes, Mayra Aparecida; Souto, Francisco José Dutra; Honorio-França, Adenilda Cristina

    2012-01-01

    Background In this study, we produced poly(ethylene glycol) (PEG) microspheres of different sizes and adsorbing a medicinal plant mixture, and verified their effect in vitro on the viability, superoxide production, and bactericidal activity of phagocytes in the blood. Methods The medicinal plant mixture was adsorbed onto PEG microspheres and its effects were evaluated by flow cytometry and fluorescence microscopy. Results Adsorption of the herbal mixture onto the PEG microspheres was achieved and the particles were internalized by phagocytes. PEG microspheres bearing the adsorbed herbal mixture stimulated superoxide release, and activated scavenging and microbicidal activity in phagocytes. No differences in functional activity were observed when the phagocytes were not incubated with PEG microspheres bearing the adsorbed herbal mixture. Conclusion This system may be useful for the delivery of a variety of medicinal plants and can confer additional protection against infection. The data reported here suggest that a polymer adsorbed with a natural product is a treatment alternative for enhancing immune function. PMID:22956861

  14. The role of polymer nanolayer architecture on the separation performance of anion-exchange membrane adsorbers: I. Protein separations.

    PubMed

    Bhut, Bharat V; Weaver, Justin; Carter, Andrew R; Wickramasinghe, S Ranil; Husson, Scott M

    2011-11-01

    This contribution describes the preparation of strong anion-exchange membranes with higher protein binding capacities than the best commercial resins. Quaternary amine (Q-type) anion-exchange membranes were prepared by grafting polyelectrolyte nanolayers from the surfaces of macroporous membrane supports. A focus of this study was to better understand the role of polymer nanolayer architecture on protein binding. Membranes were prepared with different polymer chain graft densities using a newly developed surface-initiated polymerization protocol designed to provide uniform and variable chain spacing. Bovine serum albumin and immunoglobulin G were used to measure binding capacities of proteins with different size. Dynamic binding capacities of IgG were measured to evaluate the impact of polymer chain density on the accessibility of large size protein to binding sites within the polyelectrolyte nanolayer under flow conditions. The dynamic binding capacity of IgG increased nearly linearly with increasing polymer chain density, which suggests that the spacing between polymer chains is sufficient for IgG to access binding sites all along the grafted polymer chains. Furthermore, the high dynamic binding capacity of IgG (>130 mg/mL) was independent of linear flow velocity, which suggests that the mass transfer of IgG molecules to the binding sites occurs primarily via convection. Overall, this research provides clear evidence that the dynamic binding capacities of large biologics can be higher for well-designed macroporous membrane adsorbers than commercial membrane or resin ion-exchange products. Specifically, using controlled polymerization leads to anion-exchange membrane adsorbers with high binding capacities that are independent of flow rate, enabling high throughput. Results of this work should help to accelerate the broader implementation of membrane adsorbers in bioprocess purification steps.

  15. Novel Side-Chain Liquid Cyrstalline Polymers

    DTIC Science & Technology

    1989-01-01

    chloride was added, and the mixture was acidified with formic acid . The organic layer ..as separated, dried over anhydrous MgSO4, filtered and the...Polymers and Sequential Copolymers by Phase Transfer Catalysis , 29. Synthesis of Thermotropic Side-Chain Liquid Crystalline Polymers Containing a Poly(2,6...Western Reserve University) 00 6. C. Pugh and V. Percec Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis . 30.-Synthesis of

  16. Adsorbed polymers under flow. A stochastic dynamical system approach

    NASA Astrophysics Data System (ADS)

    Armstrong, Robert; Jhon, Myung S.

    1985-09-01

    Recent experiments have shown that porous filters preadsorbed with polymer molecules exhibit an anomalously high pressure drop at high rates of flow. We have modeled the adsorbed polymers as dynamical systems and have found that the introduction of hydrodynamic interaction between molecules destabilizes at a high applied shear. As a direct result this instability will cause the molecules to unravel and stretch far into the cross section of the pore, and thus by inference, cause the observed anomalously high pressure drop. Although much of this paper is devoted to the stability characteristics of the deterministic system, Brownian motion is also considered, and an account of the statistics of the Brownian system when the deterministic system becomes unstable is given. The examples revealed in this paper are not of sufficient complexity to calculate with any accuracy the magnitude of this anomalous pressure drop. We simply present a procedure by which a large variety of more complex models could be undertaken and their ultimate effect clearly understood.

  17. 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.

  18. Tightness of slip-linked polymer chains.

    PubMed

    Metzler, Ralf; Hanke, Andreas; Dommersnes, Paul G; Kantor, Yacov; Kardar, Mehran

    2002-06-01

    We study the interplay between entropy and topological constraints for a polymer chain in which sliding rings (slip links) enforce pair contacts between monomers. These slip links divide a closed ring polymer into a number of subloops which can exchange length among each other. In the ideal chain limit, we find the joint probability density function for the sizes of segments within such a slip-linked polymer chain (paraknot). A particular segment is tight (small in size) or loose (of the order of the overall size of the paraknot) depending on both the number of slip links it incorporates and its competition with other segments. When self-avoiding interactions are included, scaling arguments can be used to predict the statistics of segment sizes for certain paraknot configurations.

  19. Chain extension of a confined polymer in steady shear flow.

    PubMed

    Bhattacharyya, Pinaki; Cherayil, Binny J

    2012-11-21

    The growing importance of microfluidic and nanofluidic devices to the study of biological processes has highlighted the need to better understand how confinement affects the behavior of polymers in flow. In this paper we explore one aspect of this question by calculating the steady-state extension of a long polymer chain in a narrow capillary tube in the presence of simple shear. The calculation is carried out within the framework of the Rouse-Zimm approach to chain dynamics, using a variant of a nonlinear elastic model to enforce finite extensibility of the chain, and assuming that the only effect of the confining surface is to modify the pre-averaged hydrodynamic interaction. The results, along with results from the corresponding calculations of finitely extensible versions of both the Rouse and Rouse-Zimm models, are compared with data from experiments on the flow-induced stretching of λ-phage DNA near a non-adsorbing glass surface [L. Fang, H. Hu, and R. G. Larson, J. Rheol. 49, 127 (2005)]. The comparison suggests that close to a surface hydrodynamic screening is significant, and causes the chains to become effectively free-draining.

  20. Chain relaxation in thin polymer films: turning a dielectric type-B polymer into a type-A' one.

    PubMed

    Solar, Mathieu; Paul, Wolfgang

    2017-02-22

    A molecular dynamics simulation study of chain relaxation in a thin polymer film is presented, studying the dielectric response of a random copolymer of cis and trans 1,4-polybutadiene, a type B polymer without net chain dipole moment, confined between graphite walls. We stress the orientational effect of the attractive walls, inducing polarization in the vicinity of the walls, while the center of the film stays bulk-like. This polarization leads to a net dipole moment of the adsorbed chains, which is perpendicular to their end-to-end vector, which we termed as type A' behavior. In this situation, the dipole moment relaxes only upon desorption of the chains from the wall, a dynamic process which occurs on timescales much longer than the bulk relaxation time of the polymer.

  1. The effect of chain flexibility and chain mobility on radiation crosslinking of polymers

    NASA Astrophysics Data System (ADS)

    Jia Zhen, Sun

    2001-01-01

    Radiation crosslinking of polymers mainly depends on the structure of polymer chain. The flexibility and mobility of chain directly influence the possibility of the reactive radicals recombination. Flexible chain is easier to crosslink than rigid-chain polymer. The latter must be crosslinked at high temperature, as most polymers can only crosslink above their melting point. Structural effect also influences the mechanism of radiation crosslinking of polymers. We find from the results in literature and in our laboratory that, the flexibility chain polymer mainly crosslinked with H type, but the rigid chain polymer mainly crosslinked with Y type.

  2. The Packing of Granular Polymer Chains

    NASA Astrophysics Data System (ADS)

    Zou, Ling-Nan; Cheng, Xiang; Rivers, Mark L.; Jaeger, Heinrich M.; Nagel, Sidney R.

    2009-10-01

    Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here, we examine the disordered packing of chains constructed out of flexibly connected hard spheres. Using x-ray tomography, we find that long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally, we uncover close similarities between the packing of chains and the glass transition in polymers.

  3. Macromolecular recognition: Recognition of polymer side chains by cyclodextrin

    NASA Astrophysics Data System (ADS)

    Hashidzume, Akihito; Harada, Akira

    2015-12-01

    The interaction of cyclodextrins (CD) with water soluble polymers possessing guest residues has been investigated as model systems in biological molecular recognition. The selectivity of interaction of CD with polymer-carrying guest residues is controlled by polymer chains, i.e., the steric effect of polymer main chain, the conformational effect of polymer main chain, and multi-site interaction. Macroscopic assemblies have been also realized based on molecular recognition using polyacrylamide-based gels possessing CD and guest residues.

  4. Crosslinked polymer nanoparticles containing single conjugated polymer chains.

    PubMed

    Ponzio, Rodrigo A; Marcato, Yésica L; Gómez, María L; Waiman, Carolina V; Chesta, Carlos A; Palacios, Rodrigo E

    2017-03-29

    Conjugated polymer nanoparticles are widely used in fluorescent labeling and sensing, as they have mean radii between 5 and 100 nm, narrow size dispersion, high brightness, and are photochemically stable, allowing single particle detection with high spatial and temporal resolution. Highly crosslinked polymers formed by linking individual chains through covalent bonds yield high-strength rigid materials capable of withstanding dissolution by organic solvents. Hence, the combination of crosslinked polymers and conjugated polymers in a nanoparticulated material presents the possibility of interesting applications that require the combined properties of constituent polymers and nanosized dimension. In the present work, F8BT@pEGDMA nanoparticles composed of poly(ethylene glycol dimethacrylate) (pEGDMA; a crosslinked polymer) and containing the commercial conjugated polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) were synthesized and characterized. Microemulsion polymerization was applied to produce F8BT@pEDGMA particles with nanosized dimensions in a ∼25% yield. Photophysical and size distribution properties of F8BT@pEDGMA nanoparticles were evaluated by various methods, in particular single particle fluorescence microscopy techniques. The results demonstrate that the crosslinking/polymerization process imparts structural rigidity to the F8BT@pEDGMA particles by providing resistance against dissolution/disintegration in organic solvents. The synthesized fluorescent crosslinked nanoparticles contain (for the most part) single F8BT chains and can be detected at the single particle level, using fluorescence microscopy, which bodes well for their potential application as molecularly imprinted polymer fluorescent nanosensors with high spatial and temporal resolution.

  5. Slow dynamics in proteins and polymer chains

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2013-02-01

    How a biological system can maintain in a non-equilibrium state for a very long time and why proteins aggregate are still not well understood. In this paper, we first review critical slow down of the Ising model and slow relaxation of a spin-glass model at low temperatures. The data indicate that relaxation of the spin glass model at low temperatures can be slower than the critical slowing down of the Ising model. We then review recent molecular dynamics results for the slow relaxation of polymer chains and experimental data for the glassy behavior of collagen fibrils. The slow dynamics in polymer chains and collagen fibrils can provide clues for understanding why a biological system can maintain in a non-equilibrium state for a very long time, and how to slow down protein aggregation related to neurodegenerative diseases.

  6. Nanoparticle effect on polymer chain dynamics and entanglement network

    NASA Astrophysics Data System (ADS)

    Li, Ying; Kroger, Martin

    We investigated structure and dynamics of polymer nanocomposites through molecular modeling, by considering different molecular weights of polymers chains, and volume fractions of fillers. The dynamics of unentangled chains can be separated into two phases, a bulk polymer phase and a confined polymer phase between fillers. The dynamics of a confined polymer is slower than that of a bulk polymer, while still exhibiting high mobility. The amount of the bulk polymer phase is found to exponentially decay with increasing volume fraction of fillers. When highly entangled polymer chains are confined between fillers, their conformation and entanglement network are dramatically changed, in district with their unentangled counterparts. The entangled polymer chains are found to be significantly disentangled and flattened during increment of the volume fractions of spherical nonattractive fillers. A critical volume fraction is found to control the crossover from polymer chain entanglements to `nanoparticle entanglements', below which the polymer chain relaxation accelerates upon filling. These results provide a microscopic understanding of the dynamics of entangled polymer chains inside their composites, and offer an explanation for the unusual rheological properties of polymer composites. Supported by Department of Mechanical Engineering, University of Connecticut.

  7. Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters.

    PubMed

    Önnby, L; Pakade, V; Mattiasson, B; Kirsebom, H

    2012-09-01

    Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, <50 nm) incorporated in amine rich cryogels (Alu-cryo), (b) molecular imprinted polymers (<38 μm) in polyacrylamide cryogels (MIP-cryo) and (c) thiol functionalised cryogels (SH-cryo) were evaluated regarding material characteristics and arsenic removal in batch test and continuous mode. Results revealed that a composite design with particles incorporated in cryogels was a successful means for applying small particles (nano- and micro- scale) in water solutions with maintained adsorption capacity and kinetics. Low capacity was obtained from SH-cryo and this adsorbent was hence excluded from the study. The adsorption capacities for the composites were 20.3 ± 0.8 mg/g adsorbent (Alu-cryo) and 7.9 ± 0.7 mg/g adsorbent (MIP-cryo) respectively. From SEM images it was seen that particles were homogeneously distributed in Alu-cryo and heterogeneously distributed in MIP-cryo. The particle incorporation increased the mechanical stability and the polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity.

  8. Analytic liquid-state theory of the interactions between colloids mediated by reversibly adsorbed polymers

    NASA Astrophysics Data System (ADS)

    Chervanyov, A. I.

    2014-12-01

    We develop an analytic liquid-state theory of the effective interactions induced by reversibly adsorbing polymers, acting between colloids immersed in a polymer melt. This theory is based on the polymer reference interaction site model that has no restrictions with respect to the density of the polymer system and colloid-to-polymer size ratio. By making use of the developed theory, we calculate the potential of the polymer mediated interactions as a function of the colloid radius, strength and range of the adsorption potential, and the polymer density. In addition, we investigate the behavior of the second virial coefficient as a function of the polymer density in both the colloid and nano-particle limits. We found out that the presence of the adsorption interactions significantly changes the polymer mediated forces relative to the case of the pure entropic depletion interactions, showing most pronounced difference in the case of large polymer densities and small colloid-to-polymer size ratios. The significance of the above differences is determined by the relation between the range of the adsorption potential and polymer correlation length.

  9. Analytic liquid-state theory of the interactions between colloids mediated by reversibly adsorbed polymers.

    PubMed

    Chervanyov, A I

    2014-12-28

    We develop an analytic liquid-state theory of the effective interactions induced by reversibly adsorbing polymers, acting between colloids immersed in a polymer melt. This theory is based on the polymer reference interaction site model that has no restrictions with respect to the density of the polymer system and colloid-to-polymer size ratio. By making use of the developed theory, we calculate the potential of the polymer mediated interactions as a function of the colloid radius, strength and range of the adsorption potential, and the polymer density. In addition, we investigate the behavior of the second virial coefficient as a function of the polymer density in both the colloid and nano-particle limits. We found out that the presence of the adsorption interactions significantly changes the polymer mediated forces relative to the case of the pure entropic depletion interactions, showing most pronounced difference in the case of large polymer densities and small colloid-to-polymer size ratios. The significance of the above differences is determined by the relation between the range of the adsorption potential and polymer correlation length.

  10. Molecular Dynamics Simulations of Adsorption of Polymer Chains on the Surface of BmNn Graphyne-Like Monolayers

    NASA Astrophysics Data System (ADS)

    Rouhi, Saeed; Atfi, Amin

    2017-03-01

    Molecular dynamics simulations are used here to study the interactions between BmNn graphyne-like monolayers and four different polymer chains. BN, B1N9, and B2N8 graphyne-like monolayers are selected from the family of BmNn graphyne-like monolayers. It is observed that increasing the number of B atoms in the structure of BmNn graphyne-like monolayers results in larger interaction energies of nanosheet/polymer systems. It is also shown that the polymer chains with the linear adsorbed configurations on the nanosheets have larger interaction energies with the nanosheets. Investigating the effect of number of polymer repeat units on the polymer/nanosheet interaction energy, it is observed that increasing the number of repeat units of polymers leads to enhancing the polymer/nanosheet interaction energy.

  11. Application of radiation-graft material for metal adsorbent and crosslinked natural polymer for healthcare product

    NASA Astrophysics Data System (ADS)

    Tamada, Masao; Seko, Noriaki; Yoshii, Fumio

    2004-09-01

    Graft polymerization and crosslinking in radiation processing are attractive techniques for modification of the chemical and physical properties of conventional polymers. The graft polymerization and subsequent chemical treatment can introduce a chelate agent function into a conventional polymer such as polyethylene. The obtained amidoxime fibrous adsorbent was applied to the recovery of uranium from seawater. Soaking of 350 kg adsorbent 12 times in seawater led to the collection of 1 kg of uranium. Natural polymers such as derivatives of starch and cellulose were radiation-crosslinked to form hydrogels. Mats of crosslinked carboxylmethyl cellulose were evaluated by 68 patients after surgical operation. No bedsore was observed in almost of all patients after operation. This product was commercialized as "Non-bedsore" in Japan.

  12. Mechanism of dialkyl phthalates removal from aqueous solution using γ-cyclodextrin and starch based polyurethane polymer adsorbents.

    PubMed

    Okoli, Chukwunonso Peter; Adewuyi, Gregory Olufemi; Zhang, Qian; Diagboya, Paul N; Guo, Qingjun

    2014-12-19

    Phthalate esters have been known as potent endocrine disruptors and carcinogens; and their removal from water have been of considerable concern recently. In the present study, γ-cyclodextrin polyurethane polymer (GPP), γ-cyclodextrin/starch polyurethane copolymer (GSP), and starch polyurethane polymer (SPP) have been synthesized and characterized. Their adsorption efficiencies for the removal of dimethyl phthalate (DMP) and diethyl phthalate (DEP) from aqueous solutions were investigated. The characterization results showed the success of the synthesis. The isotherms were L-type, and both the Langmuir and Freundlich adsorption isotherm gave good fittings to the adsorption data. Adsorption mechanisms suggested that these adsorbents spontaneously adsorb phthalate molecules driven mainly by enthalpy change, and the adsorption process was attributed to multiple adsorbent-adsorbate interactions such as hydrogen bonding, π-π stacking, and pore filling. The results showed that starch and γ-cyclodextrin polyurethane polymer adsorbents have excellent potential as adsorbent materials for the removal of phthalates from the contaminated water.

  13. Preferential positioning of a nanoparticle bound to a polymer: Exact enumeration of a self-avoiding walk chain model

    NASA Astrophysics Data System (ADS)

    Khoo, Andy; Iwaki, Takafumi; Shew, Chwen-Yang; Yoshikawa, Kenichi

    2009-09-01

    A lattice chain model is extended to investigate the preferential position of a sticky sphere bound to a polymer chain, motivated by wrapping one nanosize core-histone with DNA to form a nucleosome structure. It was shown that the single bound histone is populated in DNA chain ends from the experiment by T. Sakaue et al. [Phys. Rev. Lett. 87, 078105 (2001)]. Here, the possible mechanisms are examined to elucidate such behavior. For neutral chains or ionic chains in high salt concentrations, spheres bound on the middle of chain may trigger conformational constraints to reduce conformational entropy. For ionic chains, the bound sphere can be driven to chain ends if its effective charge and the charge of chain monomers are of like charge. The two-dimensional chain is further studied to mimic the chromosome strongly adsorbed onto surfaces, of which behavior is similar to the three-dimensional case with minor difference due to surface confinement.

  14. Routes to Hydrogen Bonding Chain-End Functionalized Polymers.

    PubMed

    Bertrand, Arthur; Lortie, Frédéric; Bernard, Julien

    2012-12-21

    The contribution of supramolecular chemistry to polymer science opens new perspectives for the design of polymer materials exhibiting valuable properties and easier processability due to the dynamic nature of non-covalent interactions. Hydrogen bonding polymers can be used as supramolecular units for yielding larger assemblies that possess attractive features, arising from the combination of polymer properties and the responsiveness of hydrogen bonds. The post-polymerization modification of reactive end-groups is the most common procedure for generating such polymers. Examples of polymerizations mediated by hydrogen bonding-functionalized precursors have also recently been reported. This contribution reviews the current synthetic routes toward hydrogen bonding sticker chain-end functionalized polymers.

  15. Spin currents and filtering behavior in zigzag graphene nanoribbons with adsorbed molybdenum chains

    NASA Astrophysics Data System (ADS)

    García-Fuente, A.; Gallego, L. J.; Vega, A.

    2015-04-01

    By means of density-functional-theoretic calculations, we investigated the structural, electronic and transport properties of hydrogen-passivated zigzag graphene nanoribbons (ZGNRs) on which a one-atom-thick Mo chain was adsorbed (with or without one or two missing atoms), or in which the passivating hydrogen atoms were replaced by Mo atoms. Mo-passivated ZGNRs proved to be nonmagnetic. ZGNRs with an adsorbed defect-free Mo chain were most stable with the Mo atoms forming dimers above edge bay sites, which suppressed the magnetic moments of the C atoms in that half of the ribbon; around the Fermi level of these systems, each spin component had a transmission channel via the Mo spz band and one had an additional channel created by polarization of the ZGNR π* band, leading to a net spin current. The absence of an Mo dimer from an Mo chain adsorbed at the ZGNR edge made the system a perfect spin filter at low voltage bias by suppressing the Mo spz band channels. Thus this last kind of hybrid system is a potential spin valve.

  16. Variational collision integrator for polymer chains

    NASA Astrophysics Data System (ADS)

    Leyendecker, Sigrid; Hartmann, Carsten; Koch, Michael

    2012-05-01

    The numerical simulation of many-particle systems (e.g. in molecular dynamics) often involves constraints of various forms. We present a symplectic integrator for mechanical systems with holonomic (bilateral) and unilateral contact constraints, the latter being in the form of a non-penetration condition. The scheme is based on a discrete variant of Hamilton's principle in which both the discrete trajectory and the unknown collision time are varied (cf. [R. Fetecau, J. Marsden, M. Ortiz, M. West, Nonsmooth Lagrangian mechanics and variational collision integrators, SIAM J. Appl. Dyn. Syst. 2 (2003) 381-416]). As a consequence, the collision event enters the discrete equations of motion as an unknown that has to be computed on-the-fly whenever a collision is imminent. The additional bilateral constraints are efficiently dealt with employing a discrete null space reduction (including a projection and a local reparametrisation step) which considerably reduces the number of unknowns and improves the condition number during each time-step as compared to a standard treatment with Lagrange multipliers. We illustrate the numerical scheme with a simple example from polymer dynamics, a linear chain of beads, and test it against other standard numerical schemes for collision problems.

  17. Mass Distributions of Linear Chain Polymers

    PubMed Central

    Hubler, Shane L.; Craciun, Gheorghe

    2012-01-01

    Biochemistry has many examples of linear chain polymers, i.e., molecules formed from a sequence of units from a finite set of possibilities; examples include proteins, RNA, single-stranded DNA, and paired DNA. In the field of mass spectrometry, it is useful to consider the idea of weighted alphabets, with a word inheriting weight from its letters. We describe the distribution of the mass of these words in terms of a simple recurrence relation, the general solution to that relation, and a canonical form that explicitly describes both the exponential form of this distribution and its periodic features, thus explaining a wave pattern that has been observed in protein mass databases. Further, we show that a pure exponential term dominates the distribution and that there is exactly one such purely exponential term. Finally, we illustrate the use of this theorem by describing a formula for the integer mass distribution of peptides and we compare our theoretical results with mass distributions of human and yeast peptides. PMID:23024448

  18. Conformational effects on excitation transport along conjugated polymer chains.

    PubMed

    Van Averbeke, Bernard; Beljonne, David

    2009-03-26

    The dynamics of energy transport along rigid rod conjugated polymer--poly(p-phenylenebutadyine)--chains is modeled with a special emphasis on the role of conformational disorder. A simple random growth algorithm based on torsion potentials with increasing stiffness yields polymer chains with increasing degree of conjugation and narrower energetic distributions. Despite the fact that the average hopping rate between two subunits is reduced (because the decrease in electronic coupling overwhelms the increase in spectral overlap), a more efficient excitation motion along chains with longer conjugated segments is predicted, in good agreement with recent experiments. This points to the central role of conformational disorder on intrachain energy diffusion in conjugated polymers.

  19. Molecular Dynamics Approach to Relaxation and Aggregationof Polymer Chains

    NASA Astrophysics Data System (ADS)

    Hu, C.; Ma, W.

    We have used molecular dynamics to simulate various systems ofpolymer chains and Lennard-Jones molecules; the neighboring monomers along a polymer chain are connected by rigid bonds or spring of strength k_{spring}. We find that the velocity distributions of monomers in a wide range of simulation time can be well described by Tsallis q-statistics [C. Tsallis, J. Stat. Phys. 52 (1988), 479] (q ≥ 1) and a single scaling function; the value of q is related to the conformation constraining potential, the interactions with background fluid, the destruction of chain homogeneity or the value of k_{spring}; when q -> 1, the velocity distribution of monomers becomes Maxwell-Boltzmann distribution. We also find that the polymer chains tend to aggregate as neighboring monomers of a polymer chain have small or zero bending-angle and torsion-angle dependent potentials. The implication of our results for the aggregation of proteins is discussed.

  20. Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers.

    PubMed

    Xie, Fei; Turesson, Martin; Woodward, Clifford E; van Gruijthuijsen, Kitty; Stradner, Anna; Forsman, Jan

    2016-04-28

    We develop a theoretical model to describe structural effects on a specific system of charged colloidal polystyrene particles, upon the addition of non-adsorbing PEG polymers. This system has previously been investigated experimentally, by scattering methods, so we are able to quantitatively compare predicted structure factors with corresponding experimental data. Our aim is to construct a model that is coarse-grained enough to be computationally manageable, yet detailed enough to capture the important physics. To this end, we utilize classical polymer density functional theory, wherein all possible polymer configurations are accounted for, subject to a mean-field Boltzmann weight. We make efforts to counteract drawbacks with this mean-field approach, resulting in structural predictions that agree very well with computationally more demanding simulations. Electrostatic interactions are handled at the fully non-linear Poisson-Boltzmann level, and we demonstrate that a linearization leads to less accurate predictions. The particle charge is an experimentally unknown parameter. We define the surface charge such that the experimental and theoretical gel point at equal polymer concentration coincide. Assuming a fixed surface charge for a certain salt concentration, we find very good agreements between measured and predicted structure factors across a wide range of polymer concentrations. We also present predictions for other structural quantities, such as radial distribution functions, and cluster size distributions. Finally, we demonstrate that our model predicts the occurrence of equilibrium clusters at high polymer concentrations, but low particle volume fractions and salt levels.

  1. Adsorption of charged and neutral polymer chains on silica surfaces: The role of electrostatics, volume exclusion, and hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Spruijt, Evan; Biesheuvel, P. M.; de Vos, Wiebe M.

    2015-01-01

    We develop an off-lattice (continuum) model to describe the adsorption of neutral polymer chains and polyelectrolytes to surfaces. Our continuum description allows taking excluded volume interactions between polymer chains and ions directly into account. To implement those interactions, we use a modified hard-sphere equation of state, adapted for mixtures of connected beads. Our model is applicable to neutral, charged, and ionizable surfaces and polymer chains alike and accounts for polarizability effects of the adsorbed layer and chemical interactions between polymer chains and the surface. We compare our model predictions to data of a classical system for polymer adsorption: neutral poly(N -vinylpyrrolidone) (PVP) on silica surfaces. The model shows that PVP adsorption on silica is driven by surface hydrogen bonding with an effective maximum binding energy of about 1.3 kBT per PVP segment at low p H . As the p H increases, the Si-OH groups become increasingly dissociated, leading to a lower capacity for H bonding and simultaneous counterion accumulation and volume exclusion close to the surface. Together these effects result in a characteristic adsorption isotherm, with the adsorbed amount dropping sharply at a critical p H . Using this model for adsorption data on silica surfaces cleaned by either a piranha solution or an O2 plasma, we find that the former have a significantly higher density of silanol groups.

  2. Transitions of tethered polymer chains: a simulation study with the bond fluctuation lattice model.

    PubMed

    Luettmer-Strathmann, Jutta; Rampf, Federica; Paul, Wolfgang; Binder, Kurt

    2008-02-14

    A polymer chain tethered to a surface may be compact or extended, adsorbed or desorbed, depending on interactions with the surface and the surrounding solvent. This leads to a rich phase diagram with a variety of transitions. To investigate these transitions we have performed Monte Carlo simulations of a bond fluctuation model with Wang-Landau and umbrella sampling algorithms in a two-dimensional state space. The simulations' density-of-states results have been evaluated for interaction parameters spanning the range from good- to poor-solvent conditions and from repulsive to strongly attractive surfaces. In this work, we describe the simulation method and present results for the overall phase behavior and for some of the transitions. For adsorption in good solvent, we compare with Metropolis Monte Carlo data for the same model and find good agreement between the results. For the collapse transition, which occurs when the solvent quality changes from good to poor, we consider two situations corresponding to three-dimensional (hard surface) and two-dimensional (very attractive surface) chain conformations, respectively. For the hard surface, we compare tethered chains with free chains and find very similar behavior for both types of chains. For the very attractive surface, we find the two-dimensional chain collapse to be a two-step transition with the same sequence of transitions that is observed for three-dimensional chains: a coil-globule transition that changes the overall chain size is followed by a local rearrangement of chain segments.

  3. Stretching of Single Polymer Chains Using the Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Ortiz, C.; van der Vegte, E. W.; van Swieten, E.; Robillard, G. T.; Hadziioannou, G.

    1998-03-01

    A variety of macroscopic phenomenon involve "nanoscale" polymer deformation including rubber elasticity, shear yielding, strain hardening, stress relaxation, fracture, and flow. With the advent of new and improved experimental techniques, such as the atomic force microscope (AFM), the probing of physical properties of polymers has reached finer and finer scales. The development of mixed self-assembling monolayer techniques and the chemical functionalization of AFM probe tips has allowed for mechanical experiments on single polymer chains of molecular dimensions. In our experiments, mixed monolayers are prepared in which end-functionalized, flexible polymer chains of thiol-terminated poly(methacrylic acid) are covalently bonded, isolated, and randomly distributed on gold substrates. The coils are then imaged, tethered to a gold-coated AFM tip, and stretched between the tip and the substrate in a conventional force / distance experiment. An increase in the attractive force due to entropic, elastic resistance to stretching, as well as fracture of the polymer chain is observed. The effect of chain stiffness, topological constraints, strain rate, mechanical hysteresis, and stress relaxation were investigated. Force modulation techniques were also employed in order to image the viscoelastic character of the polymer chains. Parallel work includes similar studies of biological systems such as wheat gluten proteins and polypeptides.

  4. Kinetic Assembly of Near-IR Active Gold Nanoclusters using Weakly Adsorbing Polymers to Control Size

    PubMed Central

    Tam, Jasmine M.; Murthy, Avinash K.; Ingram, Davis R.; Nguyen, Robin; Sokolov, Konstantin V.; Johnston, Keith P.

    2013-01-01

    Clusters of metal nanoparticles with an overall size less than 100 nm and high metal loadings for strong optical functionality, are of interest in various fields including microelectronics, sensors, optoelectronics and biomedical imaging and therapeutics. Herein we assemble ~5 nm gold particles into clusters with controlled size, as small as 30 nm and up to 100 nm, which contain only small amounts of polymeric stabilizers. The assembly is kinetically controlled with weakly adsorbing polymers, PLA(2K)-b-PEG(10K)-b-PLA(2K) or PEG (MW = 3350), by manipulating electrostatic, van der Waals (VDW), steric, and depletion forces. The cluster size and optical properties are tuned as a function of particle volume fractions and polymer/gold ratios to modulate the interparticle interactions. The close spacing between the constituent gold nanoparticles and high gold loadings (80–85% w/w gold) produce a strong absorbance cross section of ~9×10−15 m2 in the NIR at 700 nm. This morphology results from VDW and depletion attractive interactions that exclude the weakly adsorbed polymeric stabilizer from the cluster interior. The generality of this kinetic assembly platform is demonstrated for gold nanoparticles with a range of surface charges from highly negative to neutral, with the two different polymers. PMID:20361735

  5. Keto-Functionalized Polymer Scaffolds As Versatile Precursors to Polymer Side Chain Conjugates.

    PubMed

    Liu, Jingquan; Li, Ronald C; Sand, Gregory J; Bulmus, Volga; Davis, Thomas P; Maynard, Heather D

    2013-01-01

    A new methacrylate monomer with a reactive ketone side-chain, 2-(4-oxo-pentanoate) ethyl methacrylate (PAEMA), was synthesized and subsequently polymerized by reversible addition-fragmentation chain transfer (RAFT) polymerization to give a polymer with a narrow molecular weight distribution (PDI = 1.25). The polymer was chain extended with poly(ethylene glycol methyl ether acrylate) (PEGMA) to yield a block copolymer. Aminooxy containing small molecules and oligoethylene glycol were conjugated to the ketone functionality of the side chain in high yields. Cytotoxicity of the oxime-linked tetra(ethylene glycol) polymer to mouse fibroblast cells was investigated; the polymer was found to be non-cytotoxic up to 1 mg/mL. The ease with which this polymer is functionalized, suggests that it may be useful in forming tailored polymeric medicines.

  6. Chains, Rings, and Dendrites of Active Colloidal Polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Granick, Steve

    2015-03-01

    In order to better understand active polymeric matter, colloidal polymers are imaged, in situ in real time, obtaining not only temporal and spatial information about each ``monomer'' in these living polymers but also about the time-dependent and orientation-dependent correlations between them. Our reversible colloidal polymer system is assembled from self-propelled monomeric Janus particles with dynamic ``plug and play'' self-assembly and programmed direction-specific interactions between the particles. Enabling this, AC voltage induces dipoles on the monomeric Janus particles that link them into chains while also generating active phoretic motility. Unique features of this system relative to conventional Brownian polymers are emphasized.

  7. Generalized conservation law for main-chain polymer nematics.

    PubMed

    Svenšek, Daniel; Podgornik, Rudolf

    2016-05-01

    We explore the implications of the conservation law(s) and the corresponding so-called continuity equation(s), resulting from the coupling between the positional and the orientational order in main-chain polymer nematics, by showing that the vectorial and tensorial forms of these equations are in general not equivalent and cannot be reduced to one another, but neither are they disjoint alternatives. We analyze the relation between them and elucidate the fundamental role that the chain backfolding plays in the determination of their relative strength and importance. Finally, we show that the correct penalty potential in the effective free energy, implementing these conservation laws, should actually connect both the tensorial and the vectorial constraints. We show that the consequences of the polymer chains' connectivity for their consistent mesoscopic description are thus not only highly nontrivial but that its proper implementation is absolutely crucial for a consistent coarse-grained description of the main-chain polymer nematics.

  8. Geometric somersaults of a polymer chain through cyclic twisting motions

    NASA Astrophysics Data System (ADS)

    Yanao, Tomohiro; Hino, Taiko

    2017-01-01

    This study explores the significance of geometric angle shifts, which we call geometric somersaults, arising from cyclic twisting motions of a polymer chain. A five-bead polymer chain serves as a concise and minimal model of a molecular shaft throughout this study. We first show that this polymer chain can change its orientation about its longitudinal axis largely, e.g., 120∘, under conditions of zero total angular momentum by changing the two dihedral angles in a cyclic manner. This phenomenon is an example of the so-called "falling cat" phenomenon, where a falling cat undergoes a geometric somersault by changing its body shape under conditions of zero total angular momentum. We then extend the geometric somersault of the polymer chain to a noisy and viscous environment, where the polymer chain is steered by external driving forces. This extension shows that the polymer chain can achieve an orientation change keeping its total angular momentum and total external torque fluctuating around zero in a noisy and viscous environment. As an application, we argue that the geometric somersault of the polymer chain by 120∘ may serve as a prototypical and coarse-grained model for the rotary motion of the central shaft of ATP synthase (FOF1 -ATPase). This geometric somersault is in clear contrast to the standard picture for the rotary motion of the central shaft as a rigid body, which generally incurs nonzero total angular momentum and nonzero total external torque. The power profile of the geometric somersault implies a preliminary mechanism for elastic power transmission. The results of this study may be of fundamental interest in twisting and rotary motions of biomolecules.

  9. Melt crystallization/dewetting of ultrathin PEO films via carbon dioxide annealing: the effects of polymer adsorbed layers.

    PubMed

    Asada, Mitsunori; Jiang, Naisheng; Sendogdular, Levent; Sokolov, Jonathan; Endoh, Maya K; Koga, Tadanori; Fukuto, Masafumi; Yang, Lin; Akgun, Bulent; Dimitriou, Michael; Satija, Sushil

    2014-09-14

    The effects of CO2 annealing on the melting and subsequent melt crystallization processes of spin-cast poly(ethylene oxide) (PEO) ultrathin films (20-100 nm in thickness) prepared on Si substrates were investigated. By using in situ neutron reflectivity, we found that all the PEO thin films show melting at a pressure as low as P = 2.9 MPa and at T = 48 °C which is below the bulk melting temperature (Tm). The films were then subjected to quick depressurization to atmospheric pressure, resulting in the non-equilibrium swollen state, and the melt crystallization (and/or dewetting) process was carried out in air via subsequent annealing at given temperatures below Tm. Detailed structural characterization using grazing incidence X-ray diffraction, atomic force microscopy, and polarized optical microscopy revealed two unique aspects of the CO2-treated PEO films: (i) a flat-on lamellar orientation, where the molecular chains stand normal to the film surface, is formed within the entire film regardless of the original film thickness and the annealing temperature; and (ii) the dewetting kinetics for the 20 nm thick film is much slower than that for the thicker films. The key to these phenomena is the formation of irreversibly adsorbed layers on the substrates during the CO2 annealing: the limited plasticization effect of CO2 at the polymer-substrate interface promotes polymer adsorption rather than melting. Here we explain the mechanisms of the melt crystallization and dewetting processes where the adsorbed layers play vital roles.

  10. Ozonolysis of surface adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2013-07-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (±0.8) × 10-7 and 2 (±1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ>300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(±1) but had no effect on ozonolysis of the alkene side-chain.

  11. Influence of polymer charge on the shear yield stress of silica aggregated with adsorbed cationic polymers.

    PubMed

    Zhou, Ying; Yu, Hai; Wanless, Erica J; Jameson, Graeme J; Franks, George V

    2009-08-15

    Flocs were produced by adding three cationic polymers (10% charge density, 3.0x10(5) g/mol molecular weight; 40% charge density, 1.1x10(5) g/mol molecular weight; and 100% charge density, 1.2x10(5) g/mol molecular weight) to 90 nm diameter silica particles. The shear yield stresses of the consolidated sediment beds from settled and centrifuged flocs were determined via the vane technique. The polymer charge density plays an important role in influencing the shear yield stresses of sediment beds. The shear yield stresses of sediment beds from flocs induced by the 10% charged polymer were observed to increase with an increase in polymer dose, initial solid concentration and background electrolyte concentration at all volume fractions. In comparison, polymer dose has a marginal effect on the shear yield stresses of sediment beds from flocs induced by the 40% and 100% charged polymers. The shear yield stresses of sediments from flocs induced by the 40% charged polymer are independent of salt concentration whereas the addition of salt decreases the shear yield stresses of sediments from flocs induced by the 100% charged polymer. When flocculated at the optimum dose for each polymer (12 mg/g silica for the 10% charged polymer at 0.03 M NaCl, 12 mg/g for 40% and 2 mg/g for 100%), shear yield stress increases as polymer charge increases. The effects observed are related to the flocculation mechanism (bridging, patch attraction or charge neutralisation) and the magnitude of the adhesive force. Comparison of shear and compressive yield stresses show that the network is only slightly weaker in shear than in compression. This is different than many other systems (mainly salt and pH coagulation) which have shear yield stress much less than compressive yield stress. The existing models relating the power law exponent of the volume fraction dependence of the shear yield stress to the network fractal structure are not satisfactory to predict all the experimental behaviour.

  12. Single chain stochastic polymer modeling at high strain rates.

    SciTech Connect

    Harstad, E. N.; Harlow, Francis Harvey,; Schreyer, H. L.

    2001-01-01

    Our goal is to develop constitutive relations for the behavior of a solid polymer during high-strain-rate deformations. In contrast to the classic thermodynamic techniques for deriving stress-strain response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDF. Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. To extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of nonuniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.

  13. Highly Ordered Single Conjugated Polymer Chain Rod Morphologies

    SciTech Connect

    Adachi, Takuji; Brazard, Johanna; Chokshi, Paresh; Ganesan, Venkat; Bolinger, Joshua; Barbara, Paul F.

    2010-10-15

    We have reexamined the fluorescence polarization anisotropy of single polymer chains of the prototypical conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) isolated in a poly(methyl methacrylate) (PMMA) matrix employing improved synthetic samples that contain a much smaller number of tetrahedral chemical defects per chain. The new measurements reveal a much larger fraction of highly anisotropic MEH-PPV chains, with >70% of the chains exhibiting polarization anisotropy values falling in the range of 0.6-0.9. High anisotropy is strong evidence for a rod-shaped conformation. A comparison of the experimental results with coarse grain, beads on a chain simulations reveals that simulations with the usual bead-bead pairwise additive potentials cannot reproduce the observed large fraction of high polarization values. Apparently, this type of potential lacks some yet to be identified molecular feature that is necessary to accurately simulate the experimental results.

  14. Equilibration of long chain polymer melts in computer simulations

    NASA Astrophysics Data System (ADS)

    Auhl, Rolf; Everaers, Ralf; Grest, Gary S.; Kremer, Kurt; Plimpton, Steven J.

    2003-12-01

    Several methods for preparing well equilibrated melts of long chains polymers are studied. We show that the standard method in which one starts with an ensemble of chains with the correct end-to-end distance arranged randomly in the simulation cell and introduces the excluded volume rapidly, leads to deformation on short length scales. This deformation is strongest for long chains and relaxes only after the chains have moved their own size. Two methods are shown to overcome this local deformation of the chains. One method is to first pre-pack the Gaussian chains, which reduces the density fluctuations in the system, followed by a gradual introduction of the excluded volume. The second method is a double-bridging algorithm in which new bonds are formed across a pair of chains, creating two new chains each substantially different from the original. We demonstrate the effectiveness of these methods for a linear bead spring polymer model with both zero and nonzero bending stiffness, however the methods are applicable to more complex architectures such as branched and star polymer.

  15. Nanostructured Membranes from Triblock Polymer Precursors as High Capacity Copper Adsorbents.

    PubMed

    Weidman, Jacob L; Mulvenna, Ryan A; Boudouris, Bryan W; Phillip, William A

    2015-10-13

    Membrane adsorbers are a proposed alternative to packed beds for chromatographic separations. To date, membrane adsorbers have suffered from low binding capacities and/or complex processing methodologies. In this work, a polyisoprene-b-polystyrene-b-poly(N,N-dimethylacrylamide) (PI-PS-PDMA) triblock polymer is cast into an asymmetric membrane that possesses a high density of nanopores (d ∼ 38 nm) at the upper surface of the membrane. Exposing the membrane to a 6 M aqueous hydrochloric acid solution converts the PDMA brushes that line the pore walls to poly(acrylic acid) (PAA) brushes, which are capable of binding metal ions (e.g., copper ions). Using mass transport tests and static binding experiments, the saturation capacity of the PI-PS-PAA membrane was determined to be 4.1 ± 0.3 mmol Cu(2+) g(-1). This experimental value is consistent with the theoretical binding capacity of the membranes, which is based on the initial PDMA content of the triblock polymer precursor and assumes a 1:1 stoichiometry for the binding interaction. The uniformly sized nanoscale pores provide a short diffusion length to the binding sites, resulting in a sharp breakthrough curve. Furthermore, the membrane is selective for copper ions over nickel ions, which permeate through the membrane over 10 times more rapidly than copper during the loading stage. This selectivity is present despite the fact that the sizes of these two ions are nearly identical and speaks to the chemical selectivity of the triblock polymer-based membrane. Furthermore, addition of a pH 1 solution releases the bound copper rapidly, allowing the membrane to be regenerated and reused with a negligible loss in binding capacity. Because of the high binding capacities, facile processing method implemented, and ability to tailor further the polymer brushes lining the pore walls using straightforward coupling reactions, these membrane adsorbers based on block polymer precursors have potential as a separation media that can

  16. Aminosilane-grafted polymer/silica hollow fiber adsorbents for CO₂ capture from flue gas.

    PubMed

    Rezaei, Fateme; Lively, Ryan P; Labreche, Ying; Chen, Grace; Fan, Yanfang; Koros, William J; Jones, Christopher W

    2013-05-01

    Amine/silica/polymer composite hollow fiber adsorbents are produced using a novel reactive post-spinning infusion technique, and the obtained fibers are shown to capture CO2 from simulated flue gas. The post-spinning infusion technique allows for functionalization of polymer/silica hollow fibers with different types of amines during the solvent exchange step after fiber spinning. The post-spinning infusion of 3-aminopropyltrimethoxysilane (APS) into mesoporous silica/cellulose acetate hollow fibers is demonstrated here, and the materials are compared with hollow fibers infused with poly(ethyleneimine) (PEI). This approach results in silica/polymer composite fibers with good amine distribution and accessibility, as well as adequate porosity retained within the fibers to facilitate rapid mass transfer and adsorption kinetics. The CO2 adsorption capacities for the APS-infused hollow fibers are shown to be comparable to those of amine powders with similar amine loadings. In contrast, fibers that are spun with presynthesized, amine-loaded mesoporous silica powders show negligible CO2 uptake and low amine loadings because of loss of amines from the silica materials during the fiber spinning process. Aminosilica powders are shown to be more hydrophilic than the corresponding amine containing composite hollow fibers, the bare polymer as well as silica support. Both the PEI-infused and APS-infused fibers demonstrate reduced CO2 adsorption upon elevating the temperature from 35 to 80 °C, in accordance with thermodynamics, whereas PEI-infused powders show increased CO2 uptake over that temperature range because of competing diffusional and thermodynamic effects. The CO2 adsorption kinetics as probed via TGA show that the APS-infused hollow fiber adsorbents have more rapid uptake kinetics than their aminosilica powder analogues. The adsorption performance of the functionalized hollow fibers is also assessed in CO2 breakthrough experiments. The breakthrough results show a

  17. Theoretical Studies of Relatively Rigid Polymer Chains.

    DTIC Science & Technology

    1982-12-01

    energies Chain packing Intermolecular interactions Polarizability Polybenzobisoxazoles Electrical conductivitj 20. ATTRACT (Continue an reverse side if...of these materials, the ordering of the chains, and the mechanical strength of the resulting films or fibers . The basic goals are thus a molecular...be used to prepare films and fibers having unusual strength and thermal stability. They are, however, very nearly intract- able unless some atoms or

  18. The formation of standing cylinders in block copolymer films by irreversibly adsorbed polymer layers on substrates

    NASA Astrophysics Data System (ADS)

    Shang, Jun; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori

    2013-03-01

    Block copolymers offer a simple and effective route to produce standing cylindrical nanostructures with regularity on the order of 10-100 nm, the length scale that is desirable for many advanced applications. However, these formations have been especially troublesome due to the fact that preferential interactions between one of the blocks and the surfaces will induce parallel alignment of the cylinders in order to minimize interfacial and surface energy. Here we introduce an alternative simple method utilizing an irreversibly adsorbed polymer layer (a ``Guiselin'' brush) as a neutral ``substrate'' formed on solid substrates for the arrangement of standing cylindrical nanostructures. The effect of polymer adsorbed layer on the long range ordering of asymmetric cylinder forming poly(styrene-block-ethylene/butylene-block-styrene) (SEBS) triblock copolymer thin films were investigated by using a combination of grazing incidence small angle x-ray scattering and atomic force microscopy techniques. We found that the SEBS, which forms cylinders lying parallel to the surface when prepared on silicon substrates, show standing cylindrical structures on selected Guiselin brush layers after prolong thermal annealing. The details will be discussed in the presentation. We acknowledges the financial support from NSF Grant No. CMMI-084626

  19. Thrombocyte adhesion and release of extracellular microvesicles correlate with surface morphology of adsorbent polymers for lipid apheresis.

    PubMed

    Weiss, René; Spittler, Andreas; Schmitz, Gerd; Fischer, Michael B; Weber, Viktoria

    2014-07-14

    Whole blood lipid apheresis is clinically applied to reduce low density lipoprotein cholesterol in patients with homozygous familial hypercholesterolemia. Here, we studied the correlation between physicochemical parameters, in particular, surface roughness and blood compatibility, of two polyacrylate-based and a dextran sulfate-based polymer for lipid apheresis. The adsorbent surface roughness was assessed by atomic force microscopy. Freshly isolated human thrombocytes were circulated over adsorbent columns downscaled equivalent to clinical use to study thrombocyte adhesion and microvesicle generation. Quantification of thrombocytes and microvesicles in the flow-through of the columns revealed that both thrombocyte adhesion and microvesicle generation increased with increasing adsorbent surface roughness. Activation of thrombocytes with thrombin receptor-activating peptide-6 favored their adhesion to the adsorbents, as demonstrated by preferential depletion of CD62(+) and PAC-1(+) thrombocytes. Taken together, enhanced polymer surface roughness fostered cell adhesion and microvesicle release, underscoring the role of extracellular microvesicles as markers of cellular activation and of blood compatibility.

  20. 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.

  1. Local Chain Segregation and Entanglements in a Confined Polymer Melt

    NASA Astrophysics Data System (ADS)

    Lee, Nam-Kyung; Diddens, Diddo; Meyer, Hendrik; Johner, Albert

    2017-02-01

    The reptation mechanism, introduced by de Gennes and Edwards, where a polymer diffuses along a fluffy tube, defined by the constraints imposed by its surroundings, convincingly describes the relaxation of long polymers in concentrated solutions and melts. We propose that the scale for the tube diameter is set by local chain segregation, which we study analytically. We show that the concept of local segregation is especially operational for confined geometries, where segregation extends over mesoscopic domains, drastically reducing binary contacts, and provide an estimate of the entanglement length. Our predictions are quantitatively supported by extensive molecular dynamics simulations on systems consisting of long, entangled chains.

  2. Analytic theory of the adsorption-desorption transition of Gaussian polymers interacting with a periodic lattice of adsorbing centers.

    PubMed

    Chervanyov, A I; Heinrich, G

    2008-08-21

    Based on the obtained exact analytic solution, we calculate the adsorption-desorption diagram that describes the adsorption of Gaussian polymers onto a rigid surface that bears a periodic array of the adsorbing centers. It is shown that the polymer adsorption onto this substrate is fully governed by a delicate balance between the entropic depletion repulsion of polymers from the rigid surface and their attraction to the adsorbing centers. Magnitudes of these competitive effects are calculated in terms of the reduced overall affinity of the substrate eta(-1) and the reduced separation between the adsorbing centers d. The calculated exact adsorption-desorption diagram eta(d) that describes the equilibrium between the above depletion and adsorption interactions, is shown to obey the scaling law eta approximately d(-1.17).

  3. Exploring chain tension in cold drawing of polymer glasses

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Lin, Panpan; Tsige, Mesfin; Wang, Shi-Qing

    2014-03-01

    Ductile polymer glasses can undergo large tensile extension (cold draw) to double its original length either homogeneously or through necking. The corresponding tensile stress is typically much higher than the rubbery elastic modulus. Apart from the plastic component, there is also an energetic contribution to the mechanical stress. The origin of this elastic stress appears to arise from the existence of a chain network. The elastic yielding phenomenon indicates that significant chain tension builds up during the cold drawing. Atomistic molecular dynamics simulation is carried out to delineate the nature of the chain tension and explore the suggestion of bond distortion in deformation of polymeric glasses. In a simple model to mimic a polymer glass with sufficient chain networking, we found evidence for the bond distortion that grows with the degree of extension. This work is supported, in part, by NSF (CMMI-0926522 and DMR-1105135).

  4. Anomalous diffusion of a polymer chain in an unentangled melt

    NASA Astrophysics Data System (ADS)

    Farago, Jean; Meyer, Hendrik; Semenov, Alexander

    2012-02-01

    Contrary to common belief, the hydrodynamic interactions (HI) in polymer melts are not screened beyond the monomer length and are important in transient regimes. We show that the viscoelastic HI effects (VHI) lead to anomalous dynamics of a tagged chain in an unentangled melt at t < tN (tN, the Rouse time). The chain centre-of-mass (CM) mean-square displacement is enhanced (as compared to the Rouse diffusion) by a large factor increasing with chain length. We develop an analytical theory of VHI-controlled chain dynamics yielding negative CM velocity autocorrelation function which quantitatively agrees with our MD simulations without any fitting parameter. It is also shown that the Langevin friction force, when added in the model, strongly affects the short-t CM dynamics which, however, can remain strongly enhanced. The transient VHI effects thus provide the dominant contribution to the subdiffusive CM motion universally observed in simulations and experiments on polymer melts.

  5. New polymer systems: Chain extension by dianhydrides

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.; Ingham, J. D.

    1972-01-01

    The results are presented for a systematic investigation on the use of anhydrides to prepare stable elastomeric materials for space use, under mild reaction conditions. The three anhydrides investigated were found to provide effective chain extension of hydroxy-terminated poly(alkylene oxides) and poly(butadienes). These were tetrahydrofuran tetracarboxylic dianhydride, pyromellitic dianhydride, and benzophenone tetracarboxylic diahydride. The most effective catalyst investigated was ferric acetylacetonate, which resulted in chain extension at 333 K (60 C). One feature of these anhydride reactants is that they are difunctional as anhydrides, but tetrafunctional if conditions are selected that lead to reaction of all carboxyl groups. Therefore, chain extension can be effected and then followed by crosslinking via the residual carboxyl groups.

  6. Partial Crystallinity in Alkyl Side Chain Polymers.

    NASA Astrophysics Data System (ADS)

    Sahni, Vasav; Prasad, Shishir; Villate, Johanna; Jiang, Zhang; Sinha, Sunil; Dhinojwala, Ali

    2009-03-01

    Surface freezing is the formation of a crystalline monolayer at the free surface of a melt at a temperature Ts, a few degrees above the bulk freezing temperature, Tb. This effect, i.e. Ts> Tb, common to many chain molecules, is in marked contrast with the surface melting effect, i.e. Ts<=Tb, shown by almost all other materials. Various theoretical and experimental studies have been done to characterize the monolayer formed when the surface freezes before the bulk. We have studied the structure of a novel crystalline surface monolayer on top of a disordered melt of the same material (poly(n-alkyl acrylate)s) using grazing incidence x-ray diffraction. The grazing incidence x-ray diffraction, surface tension, and bulk latent heat results show that there is partial side-chain crystallinity. Also, the surface tension results explain the trend of the difference between the surface order-to-disorder transition temperature and the bulk melting temperature (δT) as a function of side chain length. The behavior of the crystal length, crystal spacing and tilt with varying alkyl chain length and temperature was also studied.

  7. New polymer systems: Chain extension by dianhydrides

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.; Ingham, J. D.

    1974-01-01

    Three anhydrides provide effective chain extension of hydroxy-terminated polyalkylene oxides and polybutadienes. Novel feature of these anhydride reactants is that they are difunctional as anhydrides, but they are tetrafunctional if conditions are selected that lead to total esterification or reaction of all carboxyl groups.

  8. Sieving polymer synthesis by reversible addition fragmentation chain transfer polymerization.

    PubMed

    Nai, Yi Heng; Jones, Roderick C; Breadmore, Michael C

    2013-12-01

    Replaceable sieving polymers are the fundamental component for high resolution nucleic acids separation in CE. The choice of polymer and its physical properties play significant roles in influencing separation performance. Recently, reversible addition fragmentation chain transfer (RAFT) polymerization has been shown to be a versatile polymerization technique capable of yielding well defined polymers previously unattainable by conventional free radical polymerization. In this study, a high molecular weight PDMA at 765 000 gmol-1 with a PDI of 1.55 was successfully synthesized with the use of chain transfer agent - 2-propionic acidyl butyl trithiocarbonate (PABTC) in a multi-step sequential RAFT polymerization approach. This study represents the first demonstration of RAFT polymerization for synthesizing polymers with the molecular weight range suitable for high resolution DNA separation in sieving electrophoresis. Adjustment of pH in the reaction was found to be crucial for the successful RAFT polymerization of high molecular weight polymer as the buffered condition minimizes the effect of hydrolysis and aminolysis commonly associated with trithiocarbonate chain transfer agents. The separation efficiency of PABTC-PDMA was found to have marginally superior separation performance compared to a commercial PDMA formulation, POP™-CAP, of similar molecular weight range.

  9. Rouse Mode Analysis of Chain Relaxation in Polymer Nanocomposites

    PubMed Central

    Kalathi, Jagannathan T.; Rubinstein, Michael; Grest, Gary S.

    2016-01-01

    Large-scale Molecular Dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect. PMID:25939276

  10. Structural characterization of irreversibly adsorbed polymer layers at the polymer/solid interface - In-situ grazing incidence angle x-ray scattering studies

    NASA Astrophysics Data System (ADS)

    Jiang, Naisheng; Chen, Fen; Chen, Xiameng; Han, Zexi; Liang, Chen; Gin, Peter; Asada, Mitsunori; Endoh, Maya; Koga, Tad

    2012-02-01

    In recent years, great attention has been paid to irreversibly adsorbed polymer layers formed on solid substrates since they can modify various properties of polymeric materials confined at the nanometer scale. In this talk, by the combined use of in-situ grazing incidence small angle x-ray scattering and x-ray reflectivity techniques, we aim to characterize the detailed structures of the adsorbed layers composed of different homopolymers (polystyrene, polybutadiene, poly (ethylene oxide), and poly (methyl methacrylate)) prepared on silicon substrates. We will highlight the generality/differences in the structures, leading to a better understanding of the formation process of the adsorbed layers at the impenetrable solid interfaces.

  11. Primitive chain network simulations for asymmetric star polymers

    NASA Astrophysics Data System (ADS)

    Masubuchi, Yuichi; Yaoita, Takatoshi; Matsumiya, Yumi; Watanabe, Hiroshi

    2011-05-01

    For branched polymers, the curvilinear motion of the branch point along the backbone is a significant relaxation source but details of this motion have not been well understood. This study conducts multi-chain sliplink simulations to examine effects of the spatial fluctuation and curvilinear hopping of the branch point on the viscoelastic relaxation. The simulation is based on the primitive chain network model that allows the spatial fluctuations of sliplink and branch point and the chain sliding along the backbone according to the subchain tension, chemical potential gradients, drag force against medium, and random force. The sliplinks are created and/or disrupted through the motion of chain ends. The curvilinear hopping of the branch point along the backbone is allowed to occur when all sliplinks on a branched arm are lost. The simulations considering the fluctuation and the hopping of the branch point described well the viscoelastic data for symmetric and asymmetric star polymers with a parameter set common to the linear polymer. On the other hand, the simulations without the branch point motion predicted unreasonably slow relaxation for asymmetric star polymers. For asymmetric star polymers, further tests with and without the branch point hopping revealed that the hopping is much less important compared to the branch point fluctuation when the lengths of the short and long backbone arms are not very different and the waiting time for the branch point hopping (time for removal of all sliplinks on the short arm) is larger than the backbone relaxation time. Although this waiting time changes with the hopping condition, the above results suggest a significance of the branch point fluctuation in the actual relaxation of branch polymers.

  12. Folding of Polymer Chains in Early Stage of Crystallization

    NASA Astrophysics Data System (ADS)

    Yuan, Shichen; Miyoshi, Toshikazu

    Understanding the structural formation of long polymer chains in the early stage of crystallization is one of the long-standing problems in polymer science. Using solid state NMR, we investigated chain trajectory of isotactic polypropylene in the mesomorphic nano-domains formed via rapid and deep quenching. Comparison of experimental and simulated 13C-13C Double Quantum (DQ) buildup curves demonstrated that instead of random re-entry models and solidification models, individual chains in the mesomorphic form iPP adopt adjacent reentry sequences with an average folding number of = 3-4 (assuming an adjacent re-entry fraction of of 100%) during mesomorphic formation process via nucleation and growth in the early stage. This work was financially supported by the National Science Foundation (Grant DMR-1105829 and 1408855) and startup funds from the UA.

  13. Dynamics of Polymer Chains Confined in Slit-Like Pores

    NASA Astrophysics Data System (ADS)

    Milchev, Andrey; Binder, Kurt

    1996-01-01

    Monte Carlo simulations of an off-lattice bead sping model of polymer chains are presented, confining the chains between two repulsive parallel planes a distance D apart. Varying the chain length N from N=16 to N=128, we show that under good solvent conditions the chains behave like two-dimensional self-avoiding walks, their mean square gyration radius scales as <~ngle R_g^2ranglepropto N^{2ν} with ν =3/4. The density profile across the slit is independent of N and maximal in the center of the slit. The dynamical properties of the chains are found to be in full agreement with the Rouse model with excluded volume in d=2 dimensions, the relaxation times vary like taupropto N^z with z=2ν+1=5/2, the diffusion constant still being given by D_Npropto 1/N. The dynamical behavior of various mean square displacements is analyzed in detail.

  14. Particle-Directed Assembly of Semiflexible Polymer Chains

    NASA Astrophysics Data System (ADS)

    McGovern, Michael; Dorfman, Kevin; Morse, David

    We use molecular dynamics simulations to investigate several models of semiflexible polymers that exhibit an attractive interaction with spherical particles. The organization of semiflexible polymer chains through attractive interactions with spherical particles occurs in several important processes in nature, such as the winding of DNA around histones and counter-ion condensation of charged polymers. The process is also of technological interest in the packaging of DNA for delivery to cells. In this presentation, we will present data on both the phase behavior and the kinetics of self-assembly as a function of the stiffness of the polymers, the attractive potential between the monomers and the particles, and the relative size of the monomers and particles. Our simulations suggest a transition between globular and rod-like aggregates that changes from a gradual to a sudden transition depending on particle size, and that rod formation is a slow, nucleation dependent process.

  15. Mixed brush of chemically and physically adsorbed polymers under shear: inverse transport of the physisorbed species.

    PubMed

    Pastorino, C; Müller, M

    2014-01-07

    We study mixed brushes under shear flow by molecular dynamics simulation with an explicit solvent. The primary brush is formed by chemically grafting polymers to a solid substrate, the secondary brush is comprised of shorter, physically end-adsorbed molecules that can laterally diffuse. By virtue of the immobility of the grafted end-points of the primary brush, its individual macromolecules perform a cyclic motion. If there is a well defined solvent-brush interface, this cyclic motion of the primary brush molecules will collectively result in the reversal of the flow inside of the primary brush. This backflow, linear in the shear rate, gives rise to the transport of the shorter, physically end-adsorbed molecules in the opposite direction of the solvent flow. We discuss which conditions are necessary to observe this counter-intuitive phenomenon. Comparing Poiseuille and Couette flow we demonstrate that the magnitude of the local shear rate at the brush-liquid interface dictates the cyclic motion and concomitant inversion of transport but that these universal effects are independent of the type of driving the flow.

  16. Molecular insights into the pH-dependent adsorption and removal of ionizable antibiotic oxytetracycline by adsorbent cyclodextrin polymers.

    PubMed

    Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

    2014-01-01

    Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2 (+), OTCH(±), OTC(-), and OTC(2-)) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH(±) commonly has high adsorption affinity, OTC(-) exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components.

  17. Self-Assembly of Emulsion Droplets into Polymer Chains

    NASA Astrophysics Data System (ADS)

    Bargteil, Dylan; McMullen, Angus; Brujic, Jasna

    We experimentally investigate `beads-on-a-string' models of polymers using the spontaneous assembly of emulsion droplets into linear chains. Droplets functionalized with surface-mobile DNA allow for programmable 'monomers' through which we can influence the three-dimensional structure of the assembled 'polymer'. Such model polymers can be used to study conformational changes of polypeptides and the principles governing protein folding. In our system, we find that droplets bind via complementary DNA strands that are recruited into adhesion patches. Recruitment is driven by the DNA hybridization energy, and is limited by the energy cost of surface deformation and the entropy loss of the mobile linkers, yielding adhesion patches of a characteristic size with a given number of linkers. By tuning the initial surface coverage of linkers, we control valency between the droplets to create linear or branched polymer chains. We additionally control the flexibility of the model polymers by varying the salt concentration and study their dynamics between extended and collapsed states. This system opens the possibility of programming stable three-dimensional structures, such as those found within folded proteins.

  18. Chain confinement drives the mechanical properties of nanoporous polymers

    NASA Astrophysics Data System (ADS)

    Tang, Shan; Greene, M. Steven; Peng, Xiang He; Liu, Wing Kam; Guo, Zao Yang

    2014-05-01

    Recent experiments using nanoindentation and buckling-based metrology (Stafford C. M. et al., Nat. Mater., 3 (2004) 545) have shown the elastic modulus of submicron-nano porous polymers to be lower than that predicted by classical homogenization or finite element simulations, especially at high porosities. This letter presents a model that captures the experimentally observed elastic modulus of nanoporous polymers by assuming that polymer chains are less confined in the interfacial layer close to the free surface of voids than in the bulk. The confinement assumption is incorporated into a recently proposed hyperelastic model, wherein low values of confinement parameters are needed to match the observed mechanical moduli of these materials. Evidence from molecular dynamics and physical experiments further supports the conclusion that variable chain confinement at material interfaces drives the mechanical behavior in nanoporous polymers due to the increasing importance of surface effects. The effect of confinement on instability under compression is also demonstrated since instability may be exploited to create porous polymers with tunable acoustic, electronic or optic properties.

  19. Rouse mode analysis of chain relaxation in polymer nanocomposites

    SciTech Connect

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. In this paper, we examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Finally, our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

  20. Rouse mode analysis of chain relaxation in polymer nanocomposites

    DOE PAGES

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; ...

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. In this paper, we examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in themore » polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Finally, our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.« less

  1. Rouse mode analysis of chain relaxation in polymer nanocomposites

    SciTech Connect

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

  2. Rouse mode analysis of chain relaxation in polymer nanocomposites

    DOE PAGES

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; ...

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, asmore » in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.« less

  3. Unconventional phase transitions in a constrained single polymer chain

    NASA Astrophysics Data System (ADS)

    Klushin, L. I.; Skvortsov, A. M.

    2011-11-01

    Phase transitions were recognized among the most fascinating phenomena in physics. Exactly solved models are especially important in the theory of phase transitions. A number of exactly solved models of phase transitions in a single polymer chain are discussed in this review. These are three models demonstrating the second order phase transitions with some unusual features: two-dimensional model of β-structure formation, the model of coil-globule transition and adsorption of a polymer chain grafted on the solid surface. We also discuss models with first order phase transitions in a single macromolecule which admit not only exact analytical solutions for the partition function with explicit finite-size effects but also the non-equilibrium free energy as a function of the order parameter (Landau function) in closed analytical form. One of them is a model of mechanical desorption of a macromolecule, which demonstrates an unusual first order phase transition with phase coexistence within a single chain. Features of first and second order transitions become mixed here due to phase coexistence which is not accompanied by additional interfacial free energy. Apart from that, there exist several single-chain models belonging to the same class (adsorption of a polymer chain tethered near the solid surface or liquid-liquid interface, and escape transition upon compressing a polymer between small pistons) that represent examples of a highly unconventional first order phase transition with several inter-related unusual features: no simultaneous phase coexistence, and hence no phase boundary, non-concave thermodynamic potential and non-equivalence of conjugate ensembles. An analysis of complex zeros of partition functions upon approaching the thermodynamic limit is presented for models with and without phase coexistence.

  4. Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles.

    PubMed

    Takajo, Yuichi; Matsuki, Hitoshi; Kaneshina, Shoji; Aratono, Makoto; Yamanaka, Michio

    2007-09-01

    The miscibility and interaction of 1-hexanol (C6OH) and 1-heptanol (C7OH) with 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in the adsorbed films and micelles were investigated by measuring the surface tension of aqueous C6OH-DHPC and aqueous C7OH-DHPC solutions. The surface density, the mean molecular area, the composition of the adsorbed film, and the excess Gibbs energy of adsorption g(H,E), were estimated. Further, the critical micelle concentration of the mixtures was determined from the surface tension versus molality curves; the micellar composition was calculated. The miscibility of the 1-alkanols and DHPC molecules in the adsorbed film and micelles was examined using the phase diagram of adsorption (PDA) and that of micellization (PDM). The PDA and the composition dependence of g(H,E) indicated the non-ideal mixing of the 1-alkanols and DHPC molecules due to the attractive interaction between the molecules in the adsorbed film, while the PDM indicated that the 1-alkanol molecules were not incorporated in the micelles within DHPC rich region. The dependence of the mean molecular area of the mixtures on the surface composition suggested that the packing property of the adsorbed film depends on the chain length of 1-alkanol: C6OH expands the DHPC adsorbed film more than C7OH.

  5. Organometallic NLO Polymers. Accordian Main-Chain NLO Polymers of Ferrocene

    DTIC Science & Technology

    1991-12-13

    suggest that the reaction conditions required to carry out the Lewis acid catalyzed transesterification polycondensation are having deleterious effects on...organometallic main-chain NLO polymers. Our research 1"n -U has continued to f--cus on ferrocene based NLO polymers . MFP because of the outstanding results...under rt-ad pressure. The crude product wargood functional group tolerance because of the mild base (i.e. dissolved in chloroform and precipitated in

  6. Complete Phase Diagram of a Single Polymer Chain

    NASA Astrophysics Data System (ADS)

    Taylor, Mark; Paul, Wolfgang; Binder, Kurt

    2011-10-01

    The phase behavior of a single homopolymer chain is analogous to that of simple liquid, exhibiting an expanded coil (gas-like) phase, a collapsed globule (liquid-like) phase, and a compact solid phase. Using Wang-Landau sampling with bond-rebridging Monte Carlo moves we have studied the complete phase behavior of a flexible interaction-site polymer chain comprised of up to 256 square-well-spheres [1]. Here we present a finite-size scaling analysis for the phase behavior of a SW chain in the long chain limit. For a sufficiently short interaction range, the chain undergoes a direct freezing transition from the expanded coil without an intervening collapse transition. These results confirm the recent lattice model prediction that a collapsed-globule state is unstable with respect to a solid phase for polymers with sufficiently short-range monomer-monomer interactions [2]. [4pt] [1] M.P. Taylor, W. Paul, and K. Binder, J. Chem. Phys. 131, 114907 (2009).[0pt] [2] W. Paul, T. Strauch, F. Rampf, and K. Binder, Phys. Rev. E 75, 060801(R) (2007).

  7. Adsorption-driven translocation of polymer chain into nanopores

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Neimark, Alexander V.

    2012-06-01

    The polymer translocation into nanopores is generally facilitated by external driving forces, such as electric or hydrodynamic fields, to compensate for entropic restrictions imposed by the confinement. We investigate the dynamics of translocation driven by polymer adsorption to the confining walls that is relevant to chromatographic separation of macromolecules. By using the self-consistent field theory, we study the passage of a chain trough a small opening from cis to trans compartments of spherical shape with adsorption potential applied in the trans compartment. The chain transfer is modeled as the Fokker-Plank diffusion along the free energy landscape of the translocation pass represented as a sum of the free energies of cis and trans parts of the chain tethered to the pore opening. We investigate how the chain length, the size of trans compartment, the magnitude of adsorption potential, and the extent of excluded volume interactions affect the translocation time and its distribution. Interplay of these factors brings about a variety of different translocation regimes. We show that excluded volume interactions within a certain range of adsorption potentials can cause a local minimum on the free energy landscape, which is absent for ideal chains. The adsorption potential always leads to the decrease of the free energy barrier, increasing the probability of successful translocation. However, the translocation time depends non-monotonically of the magnitude of adsorption potential. Our calculations predict the existence of the critical magnitude of adsorption potential, which separates favorable and unfavorable regimes of translocation.

  8. Nano-Sized Cyclodextrin-Based Molecularly Imprinted Polymer Adsorbents for Perfluorinated Compounds—A Mini-Review

    PubMed Central

    Karoyo, Abdalla H.; Wilson, Lee D.

    2015-01-01

    Recent efforts have been directed towards the design of efficient and contaminant selective remediation technology for the removal of perfluorinated compounds (PFCs) from soils, sediments, and aquatic environments. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal materials design of sorbents for selective uptake of PFCs. This article reviews the sorptive uptake of PFCs using cyclodextrin (CD)-based polymer adsorbents with nano- to micron-sized structural attributes. The relationship between synthesis of adsorbent materials and their structure relate to the overall sorption properties. Hence, the adsorptive uptake properties of CD-based molecularly imprinted polymers (CD-MIPs) are reviewed and compared with conventional MIPs. Further comparison is made with non-imprinted polymers (NIPs) that are based on cross-linking of pre-polymer units such as chitosan with epichlorohydrin in the absence of a molecular template. In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphology that may vary considerably. This mini-review provides a rationale for the design of unique polymer adsorbent materials that employ an intrinsic porogen via incorporation of a macrocyclic compound in the polymer framework to afford adsorbent materials with tunable physicochemical properties and unique nanostructure properties. PMID:28347047

  9. Exfoliated graphite oxide decorated by PDMAEMA chains and polymer particles.

    PubMed

    Yang, Yongfang; Wang, Jie; Zhang, Jian; Liu, Jinchuan; Yang, Xinglin; Zhao, Hanying

    2009-10-06

    Exfoliated graphite oxide (GO) sheets with hydroxyl groups and amine groups on the surface were prepared by modification of graphite. Atom transfer radical polymerization (ATRP) initiator molecules were grafted onto the GO sheets by reactions of 2-bromo-2-methylpropionyl bromide with hydroxyl groups and amine groups. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) chains on the surface of GO sheets were synthesized by in-situ ATRP. X-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM) results all demonstrated that polymer chains were successfully produced. After grafting of PDMAEMA, the dispersity of GO sheets in solvents was improved significantly. Poly(ethylene glycol dimethacrylate-co-methacrylic acid) particles were deposited on GO sheets via hydrogen bonding between MAA units on polymer particles and amine groups of PDMAEMA. TEM and scanning electron microscopy were used to characterize the structure of the nanocomposites.

  10. Communication: Polarizable polymer chain under external electric field in a dilute polymer solution

    SciTech Connect

    Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.

    2015-11-28

    We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such “field-induced” globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification.

  11. Local mobility of polymer chain grafted onto polyethylene monitored by fluorescence depolarization

    NASA Astrophysics Data System (ADS)

    Tsuneda, Satoshi; Endo, Toshihiro; Saito, Kyoichi; Sugita, Kazuyuki; Horie, Kazuyuki; Yamashita, Takashi; Sugo, Takanobu

    1997-08-01

    The fluorescence depolarization method was used for investigating the local mobility of polymer chains grafted onto a porous polyethylene membrane. The real value of the rotational diffusion coefficient of a dansyl probe attached to the grafted polymer chain was obtained by using a correction method which eliminated the effect of multiple scattering on fluorescence anisotropy. The rotational mobility of the dansyl probe attached to the grafted polymer chain was sensitive to both degree of grafting and solvent polarity, which indicated that the conformation of the grafted polymer chain and the pore size of the base membrane strongly governed the dynamic parameters of the grafted polymer chain.

  12. Strength of a weak bond connecting flexible polymer chains.

    PubMed Central

    Evans, E; Ritchie, K

    1999-01-01

    Bond dissociation under steadily rising force occurs most frequently at a time governed by the rate of loading (Evans and Ritchie, 1997 Biophys. J. 72:1541-1555). Multiplied by the loading rate, the breakage time specifies the force for most frequent failure (called bond strength) that obeys the same dependence on loading rate. The spectrum of bond strength versus log(loading rate) provides an image of the energy landscape traversed in the course of unbonding. However, when a weak bond is connected to very compliant elements like long polymers, the load applied to the bond does not rise steadily under constant pulling speed. Because of nonsteady loading, the most frequent breakage force can differ significantly from that of a bond loaded at constant rate through stiff linkages. Using generic models for wormlike and freely jointed chains, we have analyzed the kinetic process of failure for a bond loaded by pulling the polymer linkages at constant speed. We find that when linked by either type of polymer chain, a bond is likely to fail at lower force under steady separation than through stiff linkages. Quite unexpectedly, a discontinuous jump can occur in bond strength at slow separation speed in the case of long polymer linkages. We demonstrate that the predictions of strength versus log(loading rate) can rationalize conflicting results obtained recently for unfolding Ig domains along muscle titin with different force techniques. PMID:10233061

  13. Bottlebrush additives drive formation of vesicle chains in polymer blends

    NASA Astrophysics Data System (ADS)

    Mah, Hui Zhen; Afzali, Pantea; Verduzco, Rafeal; Stein, Gila

    2015-03-01

    The effects of bottlebrush polymer additive with poly (styrene-r-methyl methacrylate) side-chains on the thin film morphology of polystyrene (PS) and poly (methyl methacrylate) (PMMA) blends were studied. Results were compared to PS/PMMA blends with diblock copolymer PS-b-PMMA compatibilizer and without any additive. Thin films were spin casted from toluene onto a ``neutral'' silicon surface and then annealed at a fixed temperature of 150ºC for a range of times (up to 85 mins). The morphology of the films was characterized using optical microscopy and atomic force microscopy. In the absence of any additive, the PS/PMMA blend rapidly de-mixes to form macroscale domains, while high loadings of the PS-b-PMMA additive can compatibilize the blend and suppress phase separation. However, the bottlebrush polymer additive drives the formation of well-organized vesicle chains in the PS/PMMA blend films. This morphology is favored by entropic considerations as the bottlebrush polymers are more stable than linear chains at the PS/PMMA interface and the brush like surface attracts.

  14. 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.

  15. Anomalous Diffusion of a Polymer Chain in an Unentangled Melt

    NASA Astrophysics Data System (ADS)

    Farago, J.; Meyer, H.; Semenov, A. N.

    2011-10-01

    Contrary to common belief, hydrodynamic interactions in polymer melts are not screened beyond the monomer length and are important in transient regimes. We show that viscoelastic hydrodynamic interactions (VHIs) lead to anomalous dynamics of a tagged chain in an unentangled melt at tchain length. We develop a theory of VHI-controlled chain dynamics yielding a negative c.m. velocity autocorrelation function which agrees with our molecular dynamics simulations without any fitting parameter. It is also shown that Langevin friction strongly affects the short-t c.m. dynamics, also captured by our theory. The transient VHI effects thus provide the dominant contribution to the subdiffusive c.m. motion universally observed in simulations and experiments.

  16. Novel negatively charged hybrids. 3. Removal of Pb2+ from aqueous solution using zwitterionic hybrid polymers as adsorbent.

    PubMed

    Liu, Junsheng; Ma, Yue; Zhang, Yaping; Shao, Guoquan

    2010-01-15

    Using zwitterionic hybrid polymers as adsorbent, the adsorption kinetics and isotherm, thermodynamic parameters of Delta G, Delta H and DeltaS for the removal of Pb(2+) from aqueous solution were investigated. It is indicated that the adsorption of Pb(2+) ions on these zwitterionic hybrid polymers followed the Lagergren second-order kinetic model and Freundlich isotherm model, demonstrating that the adsorption process might be Langmuir monolayer adsorption. The negative values of Delta G and the positive values of Delta H evidence that Pb(2+) adsorption on these zwitterionic hybrid polymers is spontaneous and endothermic process in nature. Moreover, the zwitterionic hybrid polymers produced reveal relatively higher desorption efficiency in 2 mol dm(-3) aqueous HNO(3) solution, indicating that they can be recycled in industrial processes. These findings suggest that these zwitterionic hybrid polymers are the promising adsorbents for Pb(2+) removal and can be potentially applied in the separation and recovery of Pb(2+) ions from the waste chemicals and contaminated water of lead-acid rechargeable battery.

  17. Poly(ethylene oxide) Mushrooms Adsorbed at Silica-Ionic Liquid Interfaces Reduce Friction.

    PubMed

    Sweeney, James; Webber, Grant B; Atkin, Rob

    2016-03-01

    The adsorbed layer conformation and lubricity of 35, 100, and 300 kDa PEO adsorbed to ionic liquid (IL)-silica interfaces from 0.01 wt % solutions have been investigated using colloid probe atomic force microscopy. The ILs used were propylammonium nitrate (PAN) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), which are protic and aprotic ILs, respectively. Normal force curves reveal steric interactions consistent with adsorbed polymer layers which are best fit using the mushroom model. Friction measurements show that the adsorbed polymer layer markedly reduces friction compared to surfaces sliding in the pure ILs and that lubricity increases with polymer length. When polymer is adsorbed to the sliding surfaces, friction is controlled by the creation and disruption of intermolecular interactions between entangled chains and the dragging of polymer chains through the interpenetration region. These experiments show that added polymer can reduce friction while maintaining the useful properties of ILs as lubricants.

  18. Elution of uranium and transition metals from amidoxime-based polymer adsorbents for sequestering uranium from seawater

    DOE PAGES

    Pan, Horng-Bin; Kuo, Li-Jung; Miyamoto, Naomi; ...

    2015-11-30

    High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3 H2O2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. Themore » Na2CO3 H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorbent very effectively at pH around 7. The coordination between vanadium (V) and amidoxime is also discussed based on our 51V NMR data.« less

  19. Elution of uranium and transition metals from amidoxime-based polymer adsorbents for sequestering uranium from seawater

    SciTech Connect

    Pan, Horng-Bin; Kuo, Li-Jung; Miyamoto, Naomi; Wood, Jordana; Strivens, Jonathan E.; Gill, Gary; Janke, Christopher James; Wai, Chien

    2015-11-30

    High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3 H2O2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. The Na2CO3 H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorbent very effectively at pH around 7. The coordination between vanadium (V) and amidoxime is also discussed based on our 51V NMR data.

  20. Chain extension and inter-chain packing order in rigid-rod polymers as determined by WAXD

    SciTech Connect

    Song, H.H.; Dotrong, M.; Evers, R.C.

    1993-12-31

    Chain extension and inter-chain packing of poly(p-phenylene benzobisthiazole) (PBZT) and its derivatives having pendents such as 2,6-dimethylphenoxy (phenoxy-PBZT) and poly(etherketone) (PBZT-g-PEK) were examined by wide angle x-ray diffraction (WAXD), assuming the polymer chains in a complete nematic phase. Results suggested that the PBZT polymer chains form a ribbon-like conformation rather than of a fully extended rigid-rod. The extent of chain extension of the polymers was highly dependent on the processing history. Much larger chain extension was observed in the highly oriented fibers than in the powders or the bulks. Grafting pendents also reduced the chain extension of rigid-rod polymers, while heat-treatment hardly influenced the chain extension in contrast to the substantial effect noted in the inter-chain packing. The large difference observed in the chain extension between the fibers and the powders or the bulks implied that the individual polymer chains in the fiber might possess quite different physical properties from those of the powders or the bulks.

  1. Polymer Chain Dynamics in a Random Environment: Heterogeneous Mobilities

    SciTech Connect

    Niedzwiedz, K.; Wischnewski, A.; Monkenbusch, M.; Richter, D.; Strauch, M.; Straube, E.; Genix, A.-C.; Arbe, A.

    2007-04-20

    We present a neutron scattering investigation on a miscible blend of two polymers with greatly different glass-transition temperatures T{sub g}. Under such conditions, the nearly frozen high-T{sub g} component imposes a random environment on the mobile chain. The results demand the consideration of a distribution of heterogeneous mobilities in the material and demonstrate that the larger scale dynamics of the fast component is not determined by the average local environment alone. This distribution of mobilities can be mapped quantitatively on the spectrum of local relaxation rates measured at high momentum transfers.

  2. Dynamics of exciton transfer in coupled polymer chains

    NASA Astrophysics Data System (ADS)

    Zhang, Y. L.; Liu, X. J.; Sun, Z.; An, Z.

    2013-05-01

    The dynamics of singlet and triplet exciton transfer in coupled polymer chains are investigated within the Su-Schrieffer-Heeger+Pariser-Parr-Pople model including both electron-phonon (e-p) coupling and electron-electron (e-e) interactions, using a multi-configurational time-dependent Hartree-Fock dynamic method. In order to explain the processes involved, the effects of on-site and long-range e-e interactions on the locality of the singlet and triplet excitons are first investigated on an isolated chain. It is found that the locality of the singlet exciton decreases, while the locality of the triplet exciton increases with an increase in the on-site e-e interactions. On the other hand, an increase in the long-range e-e interaction results in a more localized singlet exciton and triplet exciton. In coupled polymer chains, we then quantitatively show the yields of singlet and triplet exciton transfer products under the same interchain coupling. It is found that the yield of singlet interchain excitons is much higher than that of triplet interchain excitons, that is to say, singlet exciton transfer is significantly easier than that for triplet excitons. This results from the fact that the singlet exciton is more delocalized than the triplet exciton. In addition, hopping of electrons with opposite spins between the coupled chains can facilitate the transfer of singlet excitons. The results are of great significance for understanding the photoelectric conversion process and developing high-power organic optoelectronic applications.

  3. Star/linear polymer topology transformation facilitated by mechanical linking of polymer chains.

    PubMed

    Aoki, Daisuke; Uchida, Satoshi; Takata, Toshikazu

    2015-06-01

    Topology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three-armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring-opening polymerization of δ-valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end-capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane-linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N-acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity.

  4. Partition function zeros and phase transitions of a polymer chain

    NASA Astrophysics Data System (ADS)

    Phyo Aung, Pyie; Taylor, Mark

    2011-10-01

    The zeros of the canonical partition functions for flexible square-well polymer chains have been computed for chains up to length 256 for a range of square-well diameters. We have previously shown that such chain molecules can undergo a coil-globule and globule-crystal transition as well as a direct coil-crystal transition [1]. Here we show that each of these transitions has a well-defined signature in the complex-plane map of the partition function zeros. The freezing transitions are characterized by nearly circular rings of uniformly spaced roots, indicative of a discontinuous transition. The collapse transition is signaled by the coalescence of roots onto an elliptical horse-shoe segment pinching down towards the positive real axis. For sufficiently small square-well diameter the elliptical collapse ring merges with the circular freezing ring yielding the direct coil-crystal transition. The root density of all rings increases with increasing chain length and the leading roots move towards the positive real axis, implying a divergence of the specific heat in the thermodynamic limit (as originally proposed by Yang and Lee). [4pt] [1] M.P. Taylor, W. Paul, and K. Binder, J. Chem. Phys. 131, 114907 (2009).

  5. Shielding effects in polymer-polymer reactions. V. Concentration dependence of contact formation between star-branched and linear chains.

    PubMed

    Nardai, Michael M; Zifferer, Gerhard

    2013-07-19

    By use of the Dissipative Particle Dynamics (DPD) simulation technique mixtures of star-branched (arm number F = 4) and linear chains in athermal (good) solvent are analyzed regarding probabilities for intermolecular contacts of various reactive sites within different polymer coils. The accompanying sterical hindrances are described in the framework of shielding factors in order to investigate reactions and side reactions in radical polymerization and other techniques that involve polymer-polymer coupling. The shielding factors are studied as a function of total concentration from high dilution up to the bulk for different chain lengths of star-shaped and linear chains. Results indicate that their concentration dependence can be described by a power law for systems above the overlap concentration, whereas the chain length dependence vanishes when extrapolating to infinite chain lengths in that concentration range. Also the influence of the ratio of star chains and linear chains is studied for various concentrations.

  6. Sorption of organic molecules on surfaces of a microporous polymer adsorbent modified with different quantities of uracil

    NASA Astrophysics Data System (ADS)

    Gus'kov, V. Yu.; Ganieva, A. G.; Kudasheva, F. Kh.

    2016-11-01

    The sorption of organic molecules on the surfaces of a number of adsorbents based on a microporous copolymer of styrene and divinylbenzene modified with different quantities of uracil is studied by means of inverse gas chromatography at infinite dilution. Samples containing 10-6, 10-5, 10-4, 10-3, 10-2, and 0.5 × 10‒1 weight parts of uracil (the pC of uracil ranges from 1.3 to 6) are studied. The contributions from different intermolecular interactions to the Helmholtz energy of sorption are calculated via the linear free energy relationship. It is found that as the concentration of uracil on the surface of the polymer adsorbent grows, the contributions from different intermolecular interactions and the conventional polarity of the surface have a bend at pC = 3, due probably to the formation of a supramolecular structure of uracil. Based on the obtained results, it is concluded that the formation of the supramolecular structure of uracil on the surface of the polymer adsorbent starts when pC < 3.

  7. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

    NASA Astrophysics Data System (ADS)

    Manzhelii, E. V.

    2017-04-01

    The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0, are obtained. It is shown that at r

  8. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

    NASA Astrophysics Data System (ADS)

    Manzhelii, E. V.

    2016-11-01

    The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0 , are obtained. It is shown that at r

  9. Elution of Uranium and Transition Metals from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

    SciTech Connect

    Pan, Horng-Bin; Kuo, Li-Jung; Wai, Chien M.; Miyamoto, Naomi; Joshi, Ruma; Wood, Jordana R.; Strivens, Jonathan E.; Janke, Christopher J.; Oyola, Yatsandra; Das, Sadananda; Mayes, Richard T.; Gill, Gary A.

    2015-11-30

    High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3-H2O2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. The Na2CO3-H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater.

  10. Diketopyrrolopyrrole-based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices.

    PubMed

    Chen, Xingxing; Zhang, Zijian; Ding, Zicheng; Liu, Jun; Wang, Lixiang

    2016-08-22

    Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness.

  11. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    NASA Astrophysics Data System (ADS)

    Cimino, R.; Rasmussen, C. J.; Neimark, A. V.

    2013-11-01

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of "infinite" chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy.

  12. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    SciTech Connect

    Cimino, R.; Neimark, A. V.; Rasmussen, C. J.

    2013-11-28

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of “infinite” chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy.

  13. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  14. Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2015-06-02

    Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  15. Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2014-01-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (± 0.8) × 10-7 and 2 (± 1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ > 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of the alkene side chain.

  16. Particle Restabilization in Silica/PEG/Ethanol Suspensions: How Strongly do Polymers Need To Adsorb To Stabilize Against Aggregation?

    SciTech Connect

    Kim, So Youn; Zukoski, Charles F.

    2014-09-24

    We study the effects of increasing the concentration of a low molecular weight polyethylene glycol on the stability of 44 nm diameter silica nanoparticles suspended in ethanol. Polymer concentration, c{sub p}, is increased from zero to that characterizing the polymer melt. Particle stability is accessed through measurement of the particle second-virial coefficient, B{sub -2}, performed by light scattering and ultrasmall angle X-ray scattering (USAXS). The results show that at low polymer concentration, c{sub p} < 3 wt %, B{sub -2} values are positive, indicating repulsive interactions between particles. B{sub -2} decreases at intermediate concentrations (3 wt % < c{sub p} < 50 wt %), and particles aggregates are formed. At high concentrations (50 wt % < c{sub p}) B{sub -2} increases and stabilizes at a value expected for hard spheres with a diameter near 44 nm, indicating the particles are thermodynamically stable. At intermediate polymer concentrations, rates of aggregation are determined by measuring time-dependent changes in the suspension turbidity, revealing that aggregation is slowed by the necessity of the particles diffusing over a repulsive barrier in the pair potential. The magnitude of the barrier passes through a minimum at c{sub p} {approx} 12 wt % where it has a value of {approx}12kT. These results are understood in terms of a reduction of electrostatic repulsion and van der Waals attractions with increasing c{sub p}. Depletion attractions are found to play a minor role in particle stability. A model is presented suggesting displacement of weakly adsorbed polymer leads to slow aggregation at intermediate concentration, and we conclude that a general model of depletion restabilization may involve increased strength of polymer adsorption with increasing polymer concentration.

  17. Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

    DOE PAGES

    Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; ...

    2016-01-11

    The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

  18. Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

    SciTech Connect

    Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2016-01-11

    The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were more polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.

  19. High-productivity membrane adsorbers: Polymer surface-modification studies for ion-exchange and affinity bioseparations

    NASA Astrophysics Data System (ADS)

    Chenette, Heather C. S.

    This dissertation centers on the surface-modification of macroporous membranes to make them selective adsorbers for different proteins, and the analysis of the performance of these membranes relative to existing technology. The common approach used in these studies, which is using membrane technology for chromatographic applications and using atom transfer radical polymerization (ATRP) as a surface modification technique, will be introduced and supported by a brief review in Chapter 1. The specific approaches to address the unique challenges and motivations of each study system are given in the introduction sections of the respective dissertation chapters. Chapter 2 describes my work to develop cation-exchange membranes. I discuss the polymer growth kinetics and characterization of the membrane surface. I also present an analysis of productivity, which measures the mass of protein that can bind to the stationary phase per volume of stationary phase adsorbing material per time. Surprisingly and despite its importance, this performance measure was not described in previous literature. Because of the significantly shorter residence time necessary for binding to occur, the productivity of these cation-exchange membrane adsorbers (300 mg/mL/min) is nearly two orders of magnitude higher than the productivity of a commercial resin product (4 mg/mL/min). My work studying membrane adsorbers for affinity separations was built on the productivity potential of this approach, as articulated in the conclusion of Chapter 2. Chapter 3 focuses on the chemical formulation work to incorporate glycoligands into the backbone of polymer tentacles grown from the surface of the same membrane stationary phase. Emphasis is given to characterizing and testing the working formulation for ligand incorporation, and details about how I arrived at this formulation are given in Appendix B. The plant protein, or lectin, Concanavalin A (conA) was used as the target protein. The carbohydrate affinity

  20. Relationship between the Amount of Bitter Substances Adsorbed onto Lipid/Polymer Membrane and the Electric Response of Taste Sensors

    PubMed Central

    Toko, Kiyoshi; Hara, Daichi; Tahara, Yusuke; Yasuura, Masato; Ikezaki, Hidekazu

    2014-01-01

    The bitterness of bitter substances can be measured by the change in the membrane electric potential caused by adsorption (CPA) using a taste sensor (electronic tongue). In this study, we examined the relationship between the CPA value due to an acidic bitter substance and the amount of the bitter substance adsorbed onto lipid/polymer membranes, which contain different lipid contents, used in the taste sensor. We used iso-α-acid which is an acidic bitter substance found in several foods and beverages. The amount of adsorbed iso-α-acid, which was determined by spectroscopy, showed a maximum at the lipid concentration 0.1 wt % of the membrane, and the same phenomenon was observed for the CPA value. At the higher lipid concentration, however, the amount adsorbed decreased and then remained constant, while the CPA value decreased monotonically to zero. This constant adsorption amount was observed when the membrane potential in the reference solution did not change with increasing lipid concentration. The decrease in CPA value in spite of the constant adsorption amount is caused by a decrease in the sensitivity of the membrane as the surface charge density increases. The reason why the peaks appeared in both the CPA value and adsorption amount is based on the contradictory adsorption properties of iso-α-acid. The increasing charged lipid concentration of the membrane causes an increasing electrostatic attractive interaction between iso-α-acid and the membrane, but simultaneously causes a decreasing hydrophobic interaction that results in decreasing adsorption of iso-α-acid, which also has hydrophobic properties, onto the membrane. Estimates of the amount of adsorption suggest that iso-α-acid molecules are adsorbed onto both the surface and interior of the membrane. PMID:25184491

  1. Configuration of a polymer chain in bulk and close to surfaces near the coil-to-globule transition

    NASA Astrophysics Data System (ADS)

    Rissanou, Anastassia N.; Bitsanis, Ioannis A.; Anastasiadis, Spiros H.

    2003-03-01

    The coil to globule transition of polymer chains in bulk solution or attached onto a surface is investigated using Monte Carlo simulations on a cubic lattice as a function of MW, solvent quality and interfacial energy. Monte Carlo results for an isolated chain in bulk solution show an anomalous dependence of RG on the MW as the solvent becomes poorer: it exhibits a N-independent regime for intermediate MWs where there is a qualitative change in the form of the density distribution in the inner part of the chain. The coil to globule transition is in accord with Khokhlov's theoretical predictions. The coupling between the coil to globule transition and the adsorption of the chain onto attractive surfaces is investigated as a function of the surface energy. The adsorbed chain in poor solvent tends to a pancake-like conformation for very attractive surfaces. The whole behavior is not controlled by the bulk Θ temperature but by a new temperature Θ^', which depends strongly on the surface energy and tends to the value of the Θ temperature in two-dimensions.

  2. Novel adhesive properties of poly(ethylene-oxide) adsorbed nanolayers

    NASA Astrophysics Data System (ADS)

    Zeng, Wenduo

    Solid-polymer interfaces play crucial roles in the multidisciplinary field of nanotechnology and are the confluence of physics, chemistry, biology, and engineering. There is now growing evidence that polymer chains irreversibly adsorb even onto weakly attractive solid surfaces, forming a nanometer-thick adsorbed polymer layer ("adsorbed polymer nanolayers"). It has also been reported that the adsorbed layers greatly impact on local structures and properties of supported polymer thin films. In this thesis, I aim to clarify adhesive and tribological properties of adsorbed poly(ethylene-oxide) (PEO) nanolayers onto silicon (Si) substrates, which remain unsolved so far. The adsorbed nanolayers were prepared by the established protocol: one has to equilibrate the melt or dense solution against a solid surface; the unadsorbed chains can be then removed by a good solvent, while the adsorbed chains are assumed to maintain the same conformation due to the irreversible freezing through many physical solid-segment contacts. I firstly characterized the formation process and the surface/film structures of the adsorbed nanolayers by using X-ray reflectivity, grazing incidence X-ray diffraction, and atomic force microscopy. Secondly, to compare the surface energy of the adsorbed layers with the bulk, static contact angle measurements with two liquids (water and glycerol) were carried out using a optical contact angle meter equipped with a video camera. Thirdly, I designed and constructed a custom-built adhesion-testing device to quantify the adhesive property. The experimental results provide new insight into the microscopic structure - macroscopic property relationship at the solid-polymer interface.

  3. Polymer chain alignment and transistor properties of nanochannel-templated poly(3-hexylthiophene) nanowires

    NASA Astrophysics Data System (ADS)

    Oh, Seungjun; Hayakawa, Ryoma; Pan, Chengjun; Sugiyasu, Kazunori; Wakayama, Yutaka

    2016-08-01

    Nanowires of semiconducting poly(3-hexylthiophene) (P3HT) were produced by a nanochannel-template technique. Polymer chain alignment in P3HT nanowires was investigated as a function of nanochannel widths (W) and polymer chain lengths (L). We found that the ratio between chain length and channel width (L/W) was a key parameter as regards promoting polymer chain alignment. Clear dichroism was observed in polarized ultraviolet-visible (UV-Vis) absorption spectra only at a ratio of approximately L/W = 2, indicating that the L/W ratio must be optimized to achieve uniaxial chain alignment in the nanochannel direction. We speculate that an appropriate L/W ratio is effective in confining the geometries and conformations of polymer chains. This discussion was supported by theoretical simulations based on molecular dynamics. That is, the geometry of the polymer chains, including the distance and tilting angles of the chains in relation to the nanochannel surface, was dominant in determining the longitudinal alignment along the nanochannels. Thus prepared highly aligned polymer nanowire is advantageous for electrical carrier transport and has great potential for improving the device performance of field-effect transistors. In fact, a one-order improvement in carrier mobility was observed in a P3HT nanowire transistor.

  4. Chain conformation-dependent thermal conductivity of amorphous polymer blends: the impact of inter- and intra-chain interactions.

    PubMed

    Wei, Xingfei; Zhang, Teng; Luo, Tengfei

    2016-11-30

    Polymers with high thermal conductivities are of great interest for both scientific research and industrial applications. In this study, model amorphous polymer blends are studied using molecular dynamics simulations. We have examined the effects of inter- and intra-chain interactions on the molecular-level conformations of the blends, which in turn impact their thermal conductivity. It is found that the thermal conductivity of polymer blends is strongly related to the molecular conformation, especially the spatial extent of the molecular chains indicated by their radius of gyration. Tuning the intra-chain van der Waals (vdW) interaction leads to different molecular structures of the minor component in the binary blend, but the thermal conductivity is not changed. However, increasing the inter-chain vdW interactions between the major and the minor components will increase the thermal conductivity of the blend, which is due to the conformation change in the major component that leads to enhanced thermal transport along the chain backbone through the intra-chain bonding interactions. The fundamental structure-property relationship from this study may provide useful guidance for designing and synthesizing polymer blends with desirable thermal conductivity.

  5. A flexible polymer chain in a critical solvent: Coil or globule?

    NASA Astrophysics Data System (ADS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Georgi, N.; Kiselev, M. G.

    2015-02-01

    We study the behavior of a flexible polymer chain in the presence of a low-molecular weight solvent in the vicinity of a liquid-gas critical point within the framework of a self-consistent field theory. The total free energy of the dilute polymer solution is expressed as a function of the radius of gyration of the polymer and the average solvent number density within the gyration volume at the level of the mean-field approximation. Varying the strength of attraction between polymer and solvent we show that two qualitatively different regimes occur at the liquid-gas critical point. In case of weak polymer-solvent interactions the polymer chain is in a globular state. On the contrary, in case of strong polymer-solvent interactions the polymer chain attains an expanded conformation. We discuss the influence of the critical solvent density fluctuations on the polymer conformation. The reported effect could be used to excert control on the polymer conformation by changing the thermodynamic state of the solvent. It could also be helpful to estimate the solvent density within the gyration volume of the polymer for drug delivery and molecular imprinting applications.

  6. Bioactivity of freeze-dried platelet-rich plasma in an adsorbed form on a biodegradable polymer material.

    PubMed

    Nakajima, Yu; Kawase, Tomoyuki; Kobayashi, Mito; Okuda, Kazuhiro; Wolff, Larry F; Yoshie, Hiromasa

    2012-01-01

    Owing to the necessity for the immediate preparation from patients' blood, autologous platelet-rich plasma (PRP) limits its clinical applicability. To address this concern and respond to emergency care and other unpredictable uses, we have developed a freeze-dried PRP in an adsorbed form on a biodegradable polymer material (Polyglactin 910). On the polymer filaments of PRP mesh, which was prepared by coating the polymer mesh with human fresh PRP and subsequent freeze-drying, platelets were incorporated, and related growth factors were preserved at high levels. This new PRP mesh preparation significantly and reproducibly stimulated the proliferation of human periodontal ligament cells in vitro and neovascularization in a chorioallantoic membrane assay. A full-thickness skin defect model in a diabetic mouse demonstrated the PRP mesh, although prepared from human blood, substantially facilitated angiogenesis, granulation tissue formation, and re-epithelialization without inducing severe inflammation in vivo. These data demonstrate that our new PRP mesh preparation functions as a bioactive material to facilitate tissue repair/regeneration. Therefore, we suggest that this bioactive material, composed of allogeneic PRP, could be clinically used as a promising alternative in emergency care or at times when autologous PRP is not prepared immediately before application.

  7. Physically adsorbed fullerene layer on positively charged sites on zinc oxide cathode affords efficiency enhancement in inverted polymer solar cell.

    PubMed

    Cheng, Yu-Shan; Liao, Sih-Hao; Li, Yi-Lun; Chen, Show-An

    2013-07-24

    We present a novel idea for overcoming the drawback of poor contact between the ZnO cathode and active layer interface in an inverted polymer solar cell (i-PSC), simply by incorporating an electron-acceptor self-assembled monolayer (SAM)--tetrafluoroterephthalic acid (TFTPA)--on the ZnO cathode surface to create an electron-poor surface of TFTPA on ZnO. The TFTPA molecules on ZnO are anchored on the ZnO surface by reacting its carboxyl groups with hydroxyl groups on the ZnO surface, such that the tetrafluoroterephthalate moieties lay on the surface with plane-on electron-poor benzene rings acting as positive charge centers. Upon coating a layer of fullerenes on top of it, the fullerene molecules can be physically adsorbed by Coulombic interaction and facilitate a promoted electron collection from the bulk. The active layer is composed of the mid bandgap polymer poly(3-hexylthiophene) (P3HT) or low bandgap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl

  8. Conjugated polymers containing diketopyrrolopyrrole units in the main chain

    PubMed Central

    Rabindranath, A Raman; Zhang, Kai; Zhu, Yu

    2010-01-01

    Summary Research activities in the field of diketopyrrolopyrrole (DPP)-based polymers are reviewed. Synthetic pathways to monomers and polymers, and the characteristic properties of the polymers are described. Potential applications in the field of organic electronic materials such as light emitting diodes, organic solar cells and organic field effect transistors are discussed. PMID:20978619

  9. Sulfonated poly(ether ether ketone)/polypyrrole core-shell nanofibers: a novel polymeric adsorbent/conducting polymer nanostructures for ultrasensitive gas sensors.

    PubMed

    Wang, Wei; Li, Zhenyu; Jiang, Tingting; Zhao, Zhiwei; Li, Ye; Wang, Zhaojie; Wang, Ce

    2012-11-01

    Conducting polymers-based gas sensors have attracted increasing research attention these years. The introduction of inorganic sensitizers (noble metals or inorganic semiconductors) within the conducting polymers-based gas sensors has been regarded as the generally effective route for further enhanced sensors. Here we demonstrate a novel route for highly-efficient conducting polymers-based gas sensors by introduction of polymeric sensitizers (polymeric adsorbent) within the conducting polymeric nanostructures to form one-dimensional polymeric adsorbent/conducting polymer core-shell nanocomposites, via electrospinning and solution-phase polymerization. The adsorption effect of the SPEEK toward NH₃ can facilitate the mass diffusion of NH₃ through the PPy layers, resulting in the enhanced sensing signals. On the basis of the SPEEK/PPy nanofibers, the sensors exhibit large gas responses, even when exposed to very low concentration of NH₃ (20 ppb) at room temperature.

  10. Activation energy of aggregation-disaggregation self-oscillation of polymer chain.

    PubMed

    Hara, Yusuke; Jahan, Rumana A

    2012-12-03

    In this paper, we investigated the activation energies of the aggregation−disaggregation self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction by utilizing the nonthermoresponsive polymer chain in a wide temperature range. This is because the conventional type self-oscillating polymer chain, with thermoresponsive poly(Nisopropylacrylamide) (poly(NIPAAm) main-chain covalently bonded to the ruthenium catalyst (Ru(bpy)(3)) of the BZ reaction, cannot evaluate the activation energy over the lower critical solution temperature (LCST). The nonthermoresponsive self-oscillating polymer chain is composed of a poly-vinylpyrrolidone (PVP) main-chain with the ruthenium catalyst (Ru(bpy)(3)). As a result, we clarified that the activation energy of the aggregation−disaggregation self-oscillation of the polymer chain is hardly affected by the concentrations of the BZ substrates. In addition, the activation energy of the nonthermoresponsive self-oscillating polymer chain was found to be almost the same value as normal BZ reaction, i.e., not including the self-oscillating polymer system with Ru moiety.

  11. Effects of nanostructure geometry on polymer chain alignment and device performance in nanoimprinted polymer solar cell

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Mielczarek, Kamil; Zakhidov, Anvar; Hu, Walter

    2013-03-01

    Among the various organic photovoltaic devices, the conjugated polymer/fullerene approach has drawn the most research interest. The performance of these types of solar cells is greatly determined by the nanoscale morphology of the two components (donor/acceptor) and the molecular orientation/crystallinity in the photoactive layer. This article demonstrates our recent studies on the nanostructure geometry effects on the nanoimprint induced poly(3 hexylthiophene-2,5-diyl) (P3HT) chain alignment and photovoltaic performance. Out-of-plane and in-plane grazing incident X-ray diffractions are employed to characterize the chain orientations in P3HT nanogratings with different widths and heights. It is found that nanoimprint procedure changes the initial edge-on alignment in non-imprinted P3HT thin film to a vertical orientation which favors the hole transport, with an organization height H≥ 170 nm and width in the range of 60 nm<= W< 210 nm. Samples with better aligned molecules lead to a larger crystallite sizes as well. Imprinted P3HT/[6,6]-penyl-C61-butyric-acid-methyl-ester (PCBM) solar cells show an increase in power conversion efficiency (PCE) with the decrease of nanostructure width, and with the increase of height and junction area. Devices with the highest PCE are made by the fully aligned and highest P3HT nanostructures (width w= 60 nm, height h= 170 nm), allowing for the most efficient charge separation, transport and light absorption. We believe this work will contribute to the optimal geometry design of nanoimprinted polymer solar cells.

  12. Measurement of Aerodynamic Shear Stress Using Side Chain Liquid Crystal Polymers

    DTIC Science & Technology

    1992-01-01

    A novel concept was proposed exploiting the optical property response of liquid crystalline materials to various external effects. This study determined the feasibility of using side chain liquid crystal polymers as aerodynamic shear sensors. A method was developed to

  13. Influence of backbone rigidness on single chain conformation of thiophene-based conjugated polymers.

    PubMed

    Hu, Zhongjian; Liu, Jianhua; Simón-Bower, Lauren; Zhai, Lei; Gesquiere, Andre J

    2013-04-25

    Structural order of conjugated polymers at different length scales directs the optoelectronic properties of the corresponding materials; thus it is of critical importance to understand and control conjugated polymer morphology for successful application of these materials in organic optoelectronics. Herein, with the aim of probing the dependence of single chain folding properties on the chemical structure and rigidness of the polymer backbones, single molecule fluorescence spectroscopy was applied to four thiophene-based conjugated polymers. These include regioregular poly(3-hexylthiophene) (RR-P3HT), poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-14), poly(2,5-bis(3-tetradecylthiophen-2-yl)thiophene-2-yl)thiophen-2-ylthiazolo[5,4-d]thiazole) (PTzQT-12), and poly(3,3-didodecylquaterthiophene)] (PQT-12). Our previous work has shown that RR-P3HT and PBTTT-14 polymer chains fold in their nanostructures, whereas PQT-12 and PTzQT-12 do not fold in their nanostructures. At the single molecule level, it was found that RR-P3HT single chains almost exclusively fold into loosely and strongly aggregated conformations, analogous to the folding properties in nanostructures. PQT-12 displays significant chain folding as well, but only into loosely aggregated conformations, showing an absence of strongly aggregated polymer chains. PBTTT-14 exhibits a significant fraction of rigid polymer chain. The findings made for single molecules of PQT-12 and PBTTT-14 are thus in contrast with the observations made in their corresponding nanostructures. PTzQT-12 appears to be the most rigid and planar conjugated polymer of these four polymers. However, although the presumably nonfolding polymers PQT-12 and PTzQT-12 exhibit less folding than RR-P3HT, there is still a significant occurrence of chain folding for these polymers at the single molecule level. These results suggest that the folding properties of conjugated polymers can be influenced by the architecture of the

  14. Surface functionalization of quantum dots with fine-structured pH-sensitive phospholipid polymer chains.

    PubMed

    Liu, Yihua; Inoue, Yuuki; Ishihara, Kazuhiko

    2015-11-01

    To add novel functionality to quantum dots (QDs), we synthesized water-soluble and pH-responsive block-type polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were composed of cytocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer segments, which contain a small fraction of active ester groups and can be used to conjugate biologically active compounds to the polymer, and pH-responsive poly(2-(N,N-diethylamino) ethyl methacrylate (DEAEMA)) segments. One terminal of the polymer chain had a hydrophobic alkyl group that originated from the RAFT initiator. This hydrophobic group can bind to the hydrophobic layer on the QD surface. A fluorescent dye was conjugated to the polymer chains via the active ester group. The block-type polymers have an amphiphilic nature in aqueous medium. The polymers were thus easily bound to the QD surface upon evaporation of the solvent from a solution containing the block-type polymer and QDs, yielding QD/fluorescence dye-conjugated polymer hybrid nanoparticles. Fluorescence resonance energy transfer (FRET) between the QDs (donors) and the fluorescent dye molecules (acceptors) was used to obtain information on the conformational dynamics of the immobilized polymers. Higher FRET efficiency of the QD/fluorescent dye-conjugated polymer hybrid nanoparticles was observed at pH 7.4 as compared to pH 5.0 due to a stretching-shrinking conformational motion of the poly(DEAEMA) segments in response to changes in pH. We concluded that the block-type MPC polymer-modified nanoparticles could be used to evaluate the pH of cells via FRET fluorescence based on the cytocompatibility of the MPC polymer.

  15. High-performance all-polymer solar cells via side-chain engineering of the polymer acceptor: the importance of the polymer packing structure and the nanoscale blend morphology.

    PubMed

    Lee, Changyeon; Kang, Hyunbum; Lee, Wonho; Kim, Taesu; Kim, Ki-Hyun; Woo, Han Young; Wang, Cheng; Kim, Bumjoon J

    2015-04-17

    The effectiveness of side-chain engineering is demonstrated to produce highly efficient all-polymer solar cells (efficiency of 5.96%) using a series of naphthalene diimide-based polymer acceptors with controlled side chains. The dramatic changes in the polymer packing, blend morphology, and electron mobility of all-polymer solar cells elucidate clear trends in the photovoltaic performances.

  16. Adsorption and flocculation by polymers and polymer mixtures.

    PubMed

    Gregory, John; Barany, Sandor

    2011-11-14

    Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'.

  17. Enhanced physical stabilization of fenofibrate nanosuspensions via wet co-milling with a superdisintegrant and an adsorbing polymer.

    PubMed

    Azad, Mohammad; Afolabi, Afolawemi; Bhakay, Anagha; Leonardi, Jonathan; Davé, Rajesh; Bilgili, Ecevit

    2015-08-01

    Drug nanoparticles in suspensions can form aggregates leading to physical instability, which is traditionally mitigated using soluble polymers and surfactants. The aim of this paper was to explore common superdisintegrants, i.e., sodium starch glycolate (SSG), croscarmellose sodium (CCS), and crospovidone (CP), as novel class of dispersants for enhanced stabilization of fenofibrate (FNB), a model BCS Class II drug, suspensions. FNB was wet-milled with superdisintegrants along with hydroxypropyl methylcellulose (HPMC), a soluble adsorbing polymer, in a stirred media mill. For comparison, FNB was also milled in the presence of HPMC and/or SDS (sodium dodecyl sulfate) without superdisintegrants. Laser diffraction, scanning electron microscopy, viscometry, differential scanning calorimetry, and powder X-ray diffraction were used to characterize the suspensions. The results show that 2% HPMC along with 1% SSG or 1% CCS mitigated the aggregation of FNB nanoparticles significantly similar to the use of either 5% HPMC or 1% HPMC-0.075% SDS, whereas CP was not effective due to its low swelling capacity. CCS/SSG enhanced steric-kinetic stabilization of the FNB suspensions owing to their high swelling capacity, viscosity enhancement, and physical barrier action. Overall, this study provides a mechanistic basis for a novel method of formulating surfactant-free drug nanosuspensions with co-milled superdisintegrants.

  18. Determination of ractopamine in pork using a magnetic molecularly imprinted polymer as adsorbent followed by HPLC.

    PubMed

    Tang, Yiwei; Gao, Jingwen; Liu, Xiuying; Lan, Jianxing; Gao, Xue; Ma, Yong; Li, Min; Li, Jianrong

    2016-06-15

    A new magnetic molecularly imprinted polymers (MMIPs) for separation and concentration of ractopamine (RAC) were prepared using surface molecular imprinting technique with methacryloyl chloride as functional monomer and RAC as template. The MMIPs were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The results of re-binding experiments indicated that the MMIPs had fast adsorption kinetics and could reach binding equilibrium within 20 min, and the adsorption capacity of the MMIPs was 2.87-fold higher than that of the corresponding non-imprinted polymer. The selectivity of the MMIPs was evaluated according to its recognition to RAC and its analogues. The synthesized MMIPs were successfully applied to extraction, followed by high performance liquid chromatography to determine RAC in real food samples. Spiked recoveries ranged from 73.60% to 94.5%, with relative standard deviations of <11.17%.

  19. The recognition of biomaterials: pattern recognition of medical polymers and their adsorbed biomolecules.

    PubMed

    Love, Ryan J; Jones, Kim S

    2013-09-01

    All biomedical materials are recognized as foreign entities by the host immune system despite the substantial range of different materials that have been developed by material scientists and engineers. Hydrophobic biomaterials, hydrogels, biomaterials with low protein binding surfaces, and those that readily adsorb a protein layer all seem to incite similar host responses in vivo that may differ in magnitude, but ultimately result in encapsulation by fibrotic tissue. The recognition of medical materials by the host is explained by the very intricate pattern recognition system made up of integrins, toll-like receptors, scavenger receptors, and other surface proteins that enable leukocytes to perceive almost any foreign body. In this review, we describe the various pattern recognition receptors and processes that occur on biomedical material surfaces that permit detection of a range of materials within the host.

  20. Direct Imaging of Deformation and Disorder in Extended-Chain Polymer Fibers

    DTIC Science & Technology

    1991-03-01

    Lenhert, T. J. Resch, and W. W. Adams, "Molecular Packing and Crystalline Order in Polybenzobisoxazole and Polybenzobisthiazole Fibers ", in...WL-TR-91-4011 AiAh 1A0 DIRECT IMAGING OF DEFORMATION AND DISORDER IN EXTENDED-CHAIN POLYMER FIBERS David C. Martin Department of Polymer Science and...Deformation and Disorder in Extended-Chain Polymer Fibers 12. PERSONAL AUTHOR(S) David C. Martin 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year

  1. Entropic stochastic resonance of a flexible polymer chain in a confined system

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Chen, Hanshuang; Hou, Zhonghuai

    2012-07-01

    We have studied the dynamics of a flexible polymer chain in constrained dumb-bell-shape geometry subject to a periodic force and external noise along the longitudinal direction. It is found that the system exhibits a feature of entropic stochastic resonance (ESR), i.e., the temporal coherence of the polymer motion can reach a maximum level for an optimal noise intensity. We demonstrate that the occurrence of ESR is robust to the change of chain length, while the bottleneck width should be properly chosen. A gravity force in the vertical direction is not necessary for the ESR here, however, the elastic coupling between polymer beads is crucial.

  2. Conformation of a flexible polymer in explicit solvent: Accurate solvation potentials for Lennard-Jones chains.

    PubMed

    Taylor, Mark P; Ye, Yuting; Adhikari, Shishir R

    2015-11-28

    The conformation of a polymer chain in solution is coupled to the local structure of the surrounding solvent and can undergo large changes in response to variations in solvent density and temperature. The many-body effects of solvent on the structure of an n-mer polymer chain can be formally mapped to an exact n-body solvation potential. Here, we use a pair decomposition of this n-body potential to construct a set of two-body potentials for a Lennard-Jones (LJ) polymer chain in explicit LJ solvent. The solvation potentials are built from numerically exact results for 5-mer chains in solvent combined with an approximate asymptotic expression for the solvation potential between sites that are distant along the chain backbone. These potentials map the many-body chain-in-solvent problem to a few-body single-chain problem and can be used to study a chain of arbitrary length, thereby dramatically reducing the computational complexity of the polymer chain-in-solvent problem. We have constructed solvation potentials at a large number of state points across the LJ solvent phase diagram including the vapor, liquid, and super-critical regions. We use these solvation potentials in single-chain Monte Carlo (MC) simulations with n ≤ 800 to determine the size, intramolecular structure, and scaling behavior of chains in solvent. To assess our results, we have carried out full chain-in-solvent MC simulations (with n ≤ 100) and find that our solvation potential approach is quantitatively accurate for a wide range of solvent conditions for these chain lengths.

  3. Phase transfer of citrate stabilized gold nanoparticles using nonspecifically adsorbed polymers.

    PubMed

    Alkilany, Alaaldin M; Caravana, Aidan C; Hamaly, Majd A; Lerner, Kevin T; Thompson, Lucas B

    2016-01-01

    Many synthetic approaches for gold nanoparticles rely on an aqueous media, resulting in water-soluble nanoparticles, which limits the ability to incorporate gold nanoparticles into other organic solvents or hydrophobic polymeric composites. Surface functionalization and phase transfer approaches using alkylthiols or alkylamines, which strongly bind the gold surface, are common routes to overcome this limitation, however they are typically challenging methods. In this paper we report an approach to transport citrate capped gold nanoparticles into a variety of solvents, including ones that are hydrophobic and not miscible with water without the need for phase transfer agents. We suspend gold nanoparticles in a water-miscible polar organic solvent that also is a solvent for a hydrophobic polymer. After drying, polymer-stabilized gold nanoparticles were found to be dispersible in various hydrophobic solvents with maintained colloidal stability. This work investigates two hydrophobic polymers, namely (polymethylmethacrylate and polyvinylacetate), which share common chemical motifs but have significantly different physiochemical properties. Interestingly, a significant difference in their ability to stabilize the transferred gold nanoparticles is observed and discussed.

  4. Prediction of Solution Properties of Flexible-Chain Polymers: A Computer Simulation Undergraduate Experiment

    ERIC Educational Resources Information Center

    de la Torre, Jose Garcia; Cifre, Jose G. Hernandez; Martinez, M. Carmen Lopez

    2008-01-01

    This paper describes a computational exercise at undergraduate level that demonstrates the employment of Monte Carlo simulation to study the conformational statistics of flexible polymer chains, and to predict solution properties. Three simple chain models, including excluded volume interactions, have been implemented in a public-domain computer…

  5. Translocation of polymer chain in post array induced by arrangement differ

    NASA Astrophysics Data System (ADS)

    Hou, Ji-Xuan; Zhang, Ye-Hui; Chen, Yao; Yu, Xu-Chen

    2017-02-01

    We demonstrate that the arrangement differs of posts have significant effect on the translocation of polymer chains which are embedded in the post arrays by using Monte Carlo algorithm. Due to the equivalent entropic force, polymers have a tendency to translocate to the disordered-arranged post array side other than the ordered-arranged side even though the post densities are equal on both sides. By changing the diameter of the posts, we find that the associated translocation times are strongly affected by the structure of the post array. Since the entropic force is almost identical for each monomer of the polymer chain and the free energy difference between two differently-arranged sides increases linearly with the polymer chain length, the directional preference strongly depends on the polymer chain length, and the ratio between the probabilities for a polymer to move either side obeys the Boltzmann distribution. Hence, a new microfabricated device which is used to separate deoxyribonucleic acid (DNA) by molecular weight can be designed using this idea. Moreover, this study can help us to develop a better understanding on the passages of polymers across membranes in nature.

  6. Translocation of a Polymer Chain across a Nanopore: A Brownian Dynamics Simulation Study

    NASA Technical Reports Server (NTRS)

    Tian, Pu; Smith, Grant D.

    2003-01-01

    We carried out Brownian dynamics simulation studies of the translocation of single polymer chains across a nanosized pore under the driving of an applied field (chemical potential gradient). The translocation process can be either dominated by the entropic barrier resulted from restricted motion of flexible polymer chains or by applied forces (or chemical gradient across the wall), we focused on the latter case in our studies. Calculation of radius of gyrations at the two opposite sides of the wall shows that the polymer chains are not in equilibrium during the translocation process. Despite this fact, our results show that the one-dimensional diffusion and the nucleation model provide an excellent description of the dependence of average translocation time on the chemical potential gradients, the polymer chain length and the solvent viscosity. In good agreement with experimental results and theoretical predictions, the translocation time distribution of our simple model shows strong non-Gaussian characteristics. It is observed that even for this simple tubelike pore geometry, more than one peak of translocation time distribution can be generated for proper pore diameter and applied field strengths. Both repulsive Weeks-Chandler-Anderson and attractive Lennard-Jones polymer-nanopore interaction were studied, attraction facilitates the translocation process by shortening the total translocation time and dramatically improve the capturing of polymer chain. The width of the translocation time distribution was found to decrease with increasing temperature, increasing field strength, and decreasing pore diameter.

  7. Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

    SciTech Connect

    Xu, Wen-Sheng; Freed, Karl F.

    2015-07-14

    The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.

  8. Stiffness dependence of critical exponents of semiflexible polymer chains situated on two-dimensional compact fractals.

    PubMed

    Zivić, Ivan; Elezović-Hadzić, Suncica; Milosević, Sava

    2009-12-01

    We present an exact and Monte Carlo renormalization group (MCRG) study of semiflexible polymer chains on an infinite family of the plane-filling (PF) fractals. The fractals are compact, that is, their fractal dimension df is equal to 2 for all members of the fractal family enumerated by the odd integer b(3chain, on the PF fractals (for 3polymer chain) and gamma (associated with the total number of different polymer chains). In addition, we calculate nu and gamma through the MCRG approach for b up to 201. Our results show that for each particular b, critical exponents are stiffness dependent functions, in such a way that the stiffer polymer chains (with smaller values of s) display enlarged values of nu, and diminished values of gamma. On the other hand, for any specific s, the critical exponent nu monotonically decreases, whereas the critical exponent gamma monotonically increases, with the scaling parameter b. We reflect on a possible relevance of the criticality of semiflexible polymer chains on the PF family of fractals to the same problem on the regular Euclidean lattices.

  9. Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

    NASA Astrophysics Data System (ADS)

    He, Xin; Barthel, Anthony J.; Kim, Seong H.

    2016-06-01

    The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

  10. Confinement and partitioning of a single polymer chain in a dense array of nanoposts.

    PubMed

    Joo, Heesun; Kim, Jun Soo

    2015-11-14

    We present a Brownian dynamics simulation study on the confinement and partitioning of a single, flexible polymer chain in a dense array of nanoposts with different sizes and separations, especially, when the volume of an interstitial space formed among four nanoposts is less than the volume of the polymer chain. As the interstitial volume decreases by either increasing the nanopost diameter or decreasing the separation between nanoposts, the chain conformation becomes elongated in the direction parallel to the nanoposts. Interestingly, however, the degree of chain elongation varies in a non-monotonic fashion as the interstitial volume decreases while keeping the passage width between two nanoposts constant at a small value. We calculate the free energy of chain partitioning over several interstitial spaces from the partitioning probability, and find that the non-monotonic dependence of the chain elongation results from an interplay between the confinement-driven chain elongation along the direction parallel to the nanoposts and the chain spreading perpendicular to the nanoposts by partitioning chain segments over several interstitial spaces. These results present the possibility of utilizing a dense array of nanoposts as a template to control polymer conformations.

  11. FTIR spectroscopy and thermodynamics of hydrogen adsorbed in a cross-linked polymer.

    PubMed

    Spoto, Giuseppe; Vitillo, Jenny G; Cocina, Donato; Damin, Alessandro; Bonino, Francesca; Zecchina, Adriano

    2007-09-28

    The adsorption of H(2) in a cross-linked poly(styrene-co-divinylbenzene) (St-DVB) microporous polymer (BET surface area 920 m(2) g(-1)) is studied by volumetric and gravimetric methods, FTIR spectroscopy at variable temperature (300-14 K) and ab initio calculations. At 77 K the polymer reversibly stores up to 1.3 mass% H(2) at a pressure of 1 bar and 1.8 mass% at 10 bar. The adsorption process involves the specific interaction of H(2) with the structural phenyl rings through weak dispersive forces. The interacting molecules become IR active and give rise to vibrational and rotational-vibrational manifestations which are affected by the temperature, the contact time and the H(2) equilibrium pressure. The spectra of the H(2)/St-DVB system reported here represent the first IR evidence of the adsorption of hydrogen on unsaturated molecules. The adsorption enthalpy is evaluated by the VTIR (variable temperature IR spectroscopy) method (C. Otero Areán et al., Phys. Chem. Chem. Phys., 2007, DOI: 10.1039/b615535a) and compared with the results of ab initio calculations for the H(2)/benzene interaction and with literature data.

  12. Chain conformation near the substrate interface in nanoparticle stabilized polymer thin films

    NASA Astrophysics Data System (ADS)

    Barkley, Deborah; Sen, Mani; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Yuan, Guangcui; Satija, Sushil; Zhang, Yugang; Gang, Oleg; Karim, Alamgir

    When nanoparticles (NPs) are added to polymer thin films, they often migrate to the film-substrate interface and form a ``diffused immobile interfacial layer'', which serves to screen the polymer-substrate interaction and suppress dewetting. The fundamental, but unsolved question is how the conformations of the polymer chains in the layer are affected by the NPs and how that impacts the enhancement of film stability. To address the question, we used dodecane thiol-functionalized gold NPs (2.4 nm diameter) and polystyrene (PS, Mw =30kDa). We found that the critical concentration of the Au NPs to induce complete dewetting suppression of 20 nm-thick PS/Au thin films on cleaned Si substrates is 5 wt% (wt of particle/wt of polymer). To investigate the interfacial structures at the polymer-solid interface, we rinsed the annealed PS/Au thin films with toluene and characterized the residual interfacial layers by using various x-ray and neutron scattering techniques. The results indicate that the conformation of the polymer chains closer to the substrate becomes less flattened with the addition of gold NPs, allowing chains at the substrate to entangle more effectively with free chains comprising the bulk film. The detailed mechanism will be discussed. T.K. acknowledges funding from NSF Grant (CMMI-1332499).

  13. Brownian Dynamics Simulations of Flow Induced Conformation of Single Polymer Chains

    NASA Astrophysics Data System (ADS)

    Oztekin, Alparslan; Webb, Edward; Zhang, Frank; Cheng, Xuanhong

    2012-11-01

    Coarse-grained molecular dynamics simulation of single polymer chains is conducted to examine flow induced conformational changes of single polymer chains in shear and extensional flows. Dynamic properties of polymeric molecules are described using bead-spring models; these models put coarse grain groups of atoms into single particles, connected to adjacent particles via spring like interactions. A common representation of the bonded interaction, or spring, is given by the Finitely Extensible Non-linear Elastic model. The constants used in the model are determined form single-molecule force spectroscopic experiments. Simulations and experiments will help to achieve a clear picture of how von Willebrand Factor, a blood clotting protein, model system for flow-induced activation, achieves flow sensing at the single protein/polymer level. The model includes bead-bead interactions, hydrodynamic interaction, the volume of the beads and spring-spring interaction for finitely extensible dumbbell and other spring models. The effects of walls on the dynamics of polymer chains are also presented. The results are presented for various chain lengths and flow conditions. Hydrodynamic interaction and the presence of wall have strong influences on the dynamics of the polymer chain.

  14. Parallelized event chain algorithm for dense hard sphere and polymer systems

    SciTech Connect

    Kampmann, Tobias A. Boltz, Horst-Holger; Kierfeld, Jan

    2015-01-15

    We combine parallelization and cluster Monte Carlo for hard sphere systems and present a parallelized event chain algorithm for the hard disk system in two dimensions. For parallelization we use a spatial partitioning approach into simulation cells. We find that it is crucial for correctness to ensure detailed balance on the level of Monte Carlo sweeps by drawing the starting sphere of event chains within each simulation cell with replacement. We analyze the performance gains for the parallelized event chain and find a criterion for an optimal degree of parallelization. Because of the cluster nature of event chain moves massive parallelization will not be optimal. Finally, we discuss first applications of the event chain algorithm to dense polymer systems, i.e., bundle-forming solutions of attractive semiflexible polymers.

  15. Effect of Polymer Side Chains on Charge Generation and Disorder in PBDTTPD Solar Cells.

    PubMed

    Constantinou, Iordania; Lai, Tzung-Han; Klump, Erik D; Goswami, Subhadip; Schanze, Kirk S; So, Franky

    2015-12-09

    The effect of polymer side chains on device performance was investigated for PBDT(EtHex)-TPD(Oct):PC70BM and PBDT(EtHex)-TPD(EtHex):PC70BM BHJ solar cells. Going from a linear side chain on the polymer's acceptor moiety to a branched side chain was determined to have a negative impact on the overall device efficiency, because of significantly reduced short-circuit current (J(sc)) and fill factor (FF) values. Sub-bandgap external quantum efficiency (EQE) and transient photoluminescence (PL) measurements showed more-efficient carrier generation for the polymer with linear side chains, because of a higher degree of charge-transfer (CT) state delocalization, leading to more-efficient exciton dissociation. Furthermore, the increase in π-π stacking distance and disorder for the bulkier ethylhexyl side chain were shown to result in a lower hole mobility, a higher bimolecular recombination, and a higher energetic disorder. The use of linear side chains on the polymer's acceptor moiety was shown to promote photogeneration, because of more-effective CT states and favorable carrier transport resulting in improved solar cell performance.

  16. Scattering function of semiflexible polymer chains under good solvent conditions

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping; Paul, Wolfgang; Binder, Kurt

    2012-11-01

    Using the pruned-enriched Rosenbluth Monte Carlo algorithm, the scattering functions of semiflexible macromolecules in dilute solution under good solvent conditions are estimated both in d = 2 and d = 3 dimensions, considering also the effect of stretching forces. Using self-avoiding walks of up to N = 25 600 steps on the square and simple cubic lattices, variable chain stiffness is modeled by introducing an energy penalty ɛb for chain bending; varying qb = exp (-ɛb/kBT) from qb = 1 (completely flexible chains) to qb = 0.005, the persistence length can be varied over two orders of magnitude. For unstretched semiflexible chains, we test the applicability of the Kratky-Porod worm-like chain model to describe the scattering function and discuss methods for extracting persistence length estimates from scattering. While in d = 2 the direct crossover from rod-like chains to self-avoiding walks invalidates the Kratky-Porod description, it holds in d = 3 for stiff chains if the number of Kuhn segments nK does not exceed a limiting value n^*_K (which depends on the persistence length). For stretched chains, the Pincus blob size enters as a further characteristic length scale. The anisotropy of the scattering is well described by the modified Debye function, if the actual observed chain extension ⟨X⟩ (end-to-end distance in the direction of the force) as well as the corresponding longitudinal and transverse linear dimensions ⟨X2⟩ - ⟨X⟩2, < R_{g,bot }^2 > are used.

  17. Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions.

    PubMed

    Severing, Kirsten; Stibal-Fischer, Elke; Hasenhindl, Alfred; Finkelmann, Heino; Saalwächter, Kay

    2006-08-17

    In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition.

  18. High basicity adsorbents from solid residue of cellulose and synthetic polymer co-pyrolysis for phenol removal: Kinetics and mechanism

    NASA Astrophysics Data System (ADS)

    Lorenc-Grabowska, Ewa; Rutkowski, Piotr

    2014-10-01

    The activated carbons (ACs) produced from solid residue of cellulose and synthetic polymer co-pyrolysis (CACs) and commercial activated carbon from coconut shell (GC) were used for phenol removal. The adsorption kinetics and mechanism were investigated. All studied activated carbons are predominantly microporous and are characterized by basic surface characteristics. Surface area SBET varies between 1235 and 1499 m2/g, whereas the pHPZC changes from 7.70 to 10.63. The bath adsorption of phenol (P) was carried out at ambient temperature. The equilibrium time and equilibrium sorption capacity were determined. It was found that the boundary layer effect is bigger in AC with high basic characteristics of the surface. The rate controlling step is the intraparticle diffusion in CACs only, whereas in ACs with higher amount of acidic functionalities the adsorbate-surface interaction influences the rate of kinetic as well. The equilibrium isotherms are L2 type for commercial AC and L4 for CACs. The CACs are characterized by very high adsorption capacity that vary between 312 and 417 mg/g. The main mechanism of phenol adsorption is micropore filling within pores smaller than 1.4 nm. In the absence of solvent effect further adsorption of phenol on CACs takes place. The enhanced adsorption is due to dispersive/repulsive interaction induced by oxygen functionalities.

  19. Capillary electrophoresis-mass spectrometry of basic proteins using a new physically adsorbed polymer coating. Some applications in food analysis.

    PubMed

    Simó, Carolina; Elvira, Carlos; González, Nieves; San Román, J; Barbas, Coral; Cifuentes, Alejandro

    2004-07-01

    A new physically adsorbed capillary coating for capillary electrophoresis-mass spectrometry (CE-MS) of basic proteins is presented, which is easily obtained by flushing the capillary with a polymer aqueous solution for two min. This coating significantly reduces the electrostatic adsorption of a group of basic proteins (i.e., cytochrome c, lysozyme, and ribonuclease A) onto the capillary wall allowing their analysis by CE-MS. The coating protocol is compatible with electrospray inonization (ESI)-MS via the reproducible separation of the standard basic proteins (%RSD values (n = 5) < 1% for analysis time reproducibility and < 5% for peak heights, measured from the total ion electropherograms (TIEs) within the same day). The LODs determined using cytochrome c with total ion current and extracted ion current defection were 24.5 and 2.9 fmol, respectively. Using this new coating lysozymes from chicken and turkey egg white could be easily distinguished by CE-MS, demonstrating the usefulness of this method to differentiate animal species. Even after sterilization at 120 degrees C for 30 min, lysozyme could be detected, as well as in wines at concentrations much lower than the limit marked by the EC Commission Regulation. Adulteration of minced meat with 5% of egg-white could also be analysed by our CE-MS protocol.

  20. Two-dimensional folded chain crystals of a synthetic polymer in a Langmuir-Blodgett film.

    PubMed

    Kumaki, Jiro; Kawauchi, Takehiro; Yashima, Eiji

    2005-04-27

    Isotactic poly(methyl methacrylate) monolayers deposited from a water surface onto mica at different surface pressures were studied by atomic force microscopy, and their structure formation from single chains to two-dimensional folded chain crystals was clearly observed. Furthermore, gentle crystallization of the monolayer by slow compression on the water surface enabled the observation of crystals at a molecular level, thus visualizing the chain foldings and tie-chains for the first time. The resulting molecular level information will provide an important clue toward the understanding of polymer crystals not only in two dimensions but also in three dimensions.

  1. High-order sampling schemes for path integrals and Gaussian chain simulations of polymers

    SciTech Connect

    Müser, Martin H.; Müller, Marcus

    2015-05-07

    In this work, we demonstrate that path-integral schemes, derived in the context of many-body quantum systems, benefit the simulation of Gaussian chains representing polymers. Specifically, we show how to decrease discretization corrections with little extra computation from the usual O(1/P{sup 2}) to O(1/P{sup 4}), where P is the number of beads representing the chains. As a consequence, high-order integrators necessitate much smaller P than those commonly used. Particular emphasis is placed on the questions of how to maintain this rate of convergence for open polymers and for polymers confined by a hard wall as well as how to ensure efficient sampling. The advantages of the high-order sampling schemes are illustrated by studying the surface tension of a polymer melt and the interface tension in a binary homopolymers blend.

  2. Synthesis, Development, and Testing of High-Surface-Area Polymer-Based Adsorbents for the Selective Recovery of Uranium from Seawater

    SciTech Connect

    Oyola, Yatsandra; Janke, Christopher J.; Dai, Sheng

    2016-02-29

    The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. For this study, we have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (<24 h), to optimize the process. These adsorbents are synthesized through radiation-induced grafting of acrylonitrile (AN) and methacrylic acid (MAA) onto PE fibers, followed by the conversion of nitriles to amidoximes and basic conditioning. In addition, the uranium adsorption capacity, measured in units of gU/kgads, is greatly increased by reducing the diameter of the PE fiber or changing its morphology. An increase in the surface area of the PE polymer fiber allows for more grafting sites that are positioned in more-accessible locations, thereby increasing access to grafted molecules that would normally be located in the interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies are able to adsorb beyond 1 order of magnitude more uranium from simulated seawater than current commercially available adsorbents. Finally, several high-surface-area fibers were tested in natural seawater and were able to extract 5–7 times more uranium than any adsorbent reported to date.

  3. Synthesis, Development, and Testing of High-Surface-Area Polymer-Based Adsorbents for the Selective Recovery of Uranium from Seawater

    DOE PAGES

    Oyola, Yatsandra; Janke, Christopher J.; Dai, Sheng

    2016-02-29

    The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. For this study, we have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (<24 h), to optimize the process. These adsorbents are synthesized through radiation-induced grafting of acrylonitrile (AN)more » and methacrylic acid (MAA) onto PE fibers, followed by the conversion of nitriles to amidoximes and basic conditioning. In addition, the uranium adsorption capacity, measured in units of gU/kgads, is greatly increased by reducing the diameter of the PE fiber or changing its morphology. An increase in the surface area of the PE polymer fiber allows for more grafting sites that are positioned in more-accessible locations, thereby increasing access to grafted molecules that would normally be located in the interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies are able to adsorb beyond 1 order of magnitude more uranium from simulated seawater than current commercially available adsorbents. Finally, several high-surface-area fibers were tested in natural seawater and were able to extract 5–7 times more uranium than any adsorbent reported to date.« less

  4. Molecular dynamics simulation aiming at interfacial characteristics of polymer chains on nanotubes with different layers

    NASA Astrophysics Data System (ADS)

    Li, Kun; Gu, Boqin; Zhu, Wanfu

    2017-03-01

    A molecular dynamics (MD) simulations study is performed on multiwalled carbon nanotubes (MWNTs)/acrylonitrile-butadiene rubber (NBR) composites. The physisorption and interfacial characteristics between the various MWNTs and polymer macromolecular chains are identified. The effects of nanotube layers on the nanotubes/polymer interactions are examined. Each of the situation result and surface features is characterized by binding energy (Eb). It is shown that the binding energy (Eb) increase with the number of layers.

  5. Primitive-path statistics of entangled polymers: mapping multi-chain simulations onto single-chain mean-field models

    NASA Astrophysics Data System (ADS)

    Steenbakkers, Rudi J. A.; Tzoumanekas, Christos; Li, Ying; Liu, Wing Kam; Kröger, Martin; Schieber, Jay D.

    2014-01-01

    We present a method to map the full equilibrium distribution of the primitive-path (PP) length, obtained from multi-chain simulations of polymer melts, onto a single-chain mean-field ‘target’ model. Most previous works used the Doi-Edwards tube model as a target. However, the average number of monomers per PP segment, obtained from multi-chain PP networks, has consistently shown a discrepancy of a factor of two with respect to tube-model estimates. Part of the problem is that the tube model neglects fluctuations in the lengths of PP segments, the number of entanglements per chain and the distribution of monomers among PP segments, while all these fluctuations are observed in multi-chain simulations. Here we use a recently proposed slip-link model, which includes fluctuations in all these variables as well as in the spatial positions of the entanglements. This turns out to be essential to obtain qualitative and quantitative agreement with the equilibrium PP-length distribution obtained from multi-chain simulations. By fitting this distribution, we are able to determine two of the three parameters of the model, which govern its equilibrium properties. This mapping is executed for four different linear polymers and for different molecular weights. The two parameters are found to depend on chemistry, but not on molecular weight. The model predicts a constant plateau modulus minus a correction inversely proportional to molecular weight. The value for well-entangled chains, with the parameters determined ab initio, lies in the range of experimental data for the materials investigated.

  6. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    PubMed Central

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-01-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents. PMID:27713563

  7. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification.

    PubMed

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-07

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  8. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    NASA Astrophysics Data System (ADS)

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  9. Autonomous Oscillation of Polymer Chains Induced by the Belousov–Zhabotinsky Reaction

    PubMed Central

    Hara, Yusuke; Takenaka, Yoshiko

    2014-01-01

    We investigated the self-oscillating behaviors of two types of polymer chains induced by the Belousov–Zhabotinsky (BZ) reaction. One consisted of N-isopropylacrylamide (NIPAAm) and the Ru catalyst of the BZ reaction, and the other consisted of NIPAAm, the Ru catalyst, and acrylamide-2-methylpropanesulfonic acid (AMPS) with a negatively charged domain as a solubility control site. A comparison of the two types of self-oscillation systems showed that the anionic AMPS portion of the polymer chain significantly affected the self-oscillating behavior under strongly acidic condition. The periods of self-oscillation for the two types of self-oscillating polymer chains were investigated by changing the initial concentrations of the three BZ substrates and the temperature. As a result, it was demonstrated that the period of self-oscillation could be controlled by the concentration of the BZ substrates and the temperature. Furthermore, the activation energies of the two types of the self-oscillating polymer chains gave similar values as normal BZ reactions, i.e., not including the self-oscillating polymer system with a Ru moiety. In addition, it was clarified the activation energy was hardly affected by the initial concentration of the three BZ substrates. PMID:24434841

  10. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers.

    PubMed

    El Labban, Abdulrahman; Warnan, Julien; Cabanetos, Clément; Ratel, Olivier; Tassone, Christopher; Toney, Michael F; Beaujuge, Pierre M

    2014-11-26

    Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b']dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

  11. Anionic surfactant with hydrophobic and hydrophilic chains for nanoparticle dispersion and shape memory polymer nanocomposites.

    PubMed

    Iijima, Motoyuki; Kobayakawa, Murino; Yamazaki, Miwa; Ohta, Yasuhiro; Kamiya, Hidehiro

    2009-11-18

    An anionic surfactant comprising a hydrophilic poly(ethylene glycol) (PEG) chain, hydrophobic alkyl chain, and polymerizable vinyl group was synthesized as a capping agent of nanoparticles. TiO(2) nanoparticles modified by this surfactant were completely dispersible in various organic solvents with a wide range of polarities, such as nitriles, alcohols, ketones, and acetates. Furthermore, these particles were found to be dispersible in various polymers with different properties, such as thermosetting epoxy resins and radical polymerized poly(methylmethacrylate) (PMMA). A polymer composite of surface-modified TiO(2) nanoparticles in epoxy resins prepared by using the developed surfactant also possessed temperature-induced shape memory properties.

  12. Spectral properties of carbazole-containing polymers with phosphore groups in the main chain

    NASA Astrophysics Data System (ADS)

    Bogdal, D.; Yashchuk, V.; Pielichowski, Jan; Kushnir, K.; Warzala, M.; Kudrya, Vladislav

    2002-12-01

    The absorption, fluorescence and phosphorescence of the carbazole-containg polymers with phosphore groups in the main chain of two types and without spacer were studied. It was shown that spectral properties of pf2-sep polymer are connected mainly with optical transitions in individual carbazole chromophores. The optical properties of pf2-conj polymer are rather different comparative to the pf2-sep. That is caused by perturbation carbazole groups electron system by phosphor-groups and influence carbazole groups each other. This perturbation takes place under special relative geometrical displacement of carbazole and phosphor groups.

  13. Recent advances in metathesis-derived polymers containing transition metals in the side chain

    PubMed Central

    Demonceau, Albert; Fischer, Helmut

    2015-01-01

    Summary This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  14. Gene analysis of multiple oral bacteria by the polymerase chain reaction coupled with capillary polymer electrophoresis.

    PubMed

    Liu, Chenchen; Yamaguchi, Yoshinori; Sekine, Shinichi; Ni, Yi; Li, Zhenqing; Zhu, Xifang; Dou, Xiaoming

    2016-03-01

    Capillary polymer electrophoresis is identified as a promising technology for the analysis of DNA from bacteria, virus and cell samples. In this paper, we propose an innovative capillary polymer electrophoresis protocol for the quantification of polymerase chain reaction products. The internal standard method was modified and applied to capillary polymer electrophoresis. The precision of our modified internal standard protocol was evaluated by measuring the relative standard deviation of intermediate capillary polymer electrophoresis experiments. Results showed that the relative standard deviation was reduced from 12.4-15.1 to 0.6-2.3%. Linear regression tests were also implemented to validate our protocol. The modified internal standard method showed good linearity and robust properties. Finally, the ease of our method was illustrated by analyzing a real clinical oral sample using a one-run capillary polymer electrophoresis experiment.

  15. Effects of disorder and chain stiffening on the elasticity of flexible polymer networks

    NASA Astrophysics Data System (ADS)

    Caroli, Christiane; Lemaître, Anaël

    2017-03-01

    We examine how the distribution of contour lengths and the high-stretch stiffening of individual chain segments affect the macroscopic shear modulus of flexible polymer gels, using a two-dimensional numerical model in which polymer segments form a triangular network and disorder is introduced by varying their contour lengths. We show that, in the relevant parameter range: (i) the nonaffine contribution to the shear modulus is negligible, i.e., the Born approximation is satisfactory, and (ii) the shear modulus is dominated by the contribution originating from equilibrium chain tensions. Moreover, mechanical equilibration at the nodes induces specific correlations between the end-to-end distances and contour lengths of chain segments, which must be properly accounted for to construct reasonable estimates of chain pressure and shear modulus.

  16. A strategy for tuning achiral main-chain polymers into helical assemblies and chiral memory systems.

    PubMed

    Yang, Dong; Zhao, Yin; Lv, Kai; Wang, Xiufeng; Zhang, Wei; Zhang, Li; Liu, Minghua

    2016-01-28

    A general strategy to tune the achiral main chain polymers into helical nanoassemblies was proposed based on the co-gelation approach. As an example, two achiral main chain polymers, PCz8 and PSi8, were selected, and their co-assembly with an amphiphilic l- or d-glutamide gelator was investigated. Although the polymers could not form gels individually, they could form co-gels with the gelator and the resultant gels exhibited macroscopic supramolecular chirality, which could be confirmed by CD spectra and SEM observations. Moreover, the supramolecular chirality can be memorized even after the gelator molecules were removed. Remarkably, either the gelator-containing or gelator-free chiral polymer assemblies showed circularly polarized luminescence (CPL), which is usually inherent to intrinsic chiral polymers. It was suggested that during the co-gelation, the chirality of the gelator was transferred to and memorized by the achiral polymers. The approach seems to be general and we provided the first example to tune the achiral polymers into helical assemblies through the co-gelation.

  17. Thermoplastic and thermoset main chain liquid crystal polymers prepared from biphenyl mesogen

    SciTech Connect

    Su, W.F.A.

    1993-12-31

    Main chain liquid crystal thermoplastic polyesters and thermosetting epoxy resins were prepared using biphenyl mesogen. The melting point of polyesters was effectively decreased by incorporating flexible methylene spacers into the polymer main chain. The liquid crystal epoxy resins exhibit high glass transition temperature, low thermal expansion coefficient, high dielectric strength and low dielectric loss. They are suitable for the preparation of self-reinforcing molecular composites.

  18. Thermodynamic and structure investigations of new side-chain liquid crystal polymer

    NASA Astrophysics Data System (ADS)

    Danch, A.; Laggner, Peter; Degovics, G.; Sek, D.; Stelzer, F.

    1998-01-01

    Bis [((omega) -(4'-cyanobiphenyl)-4-yl)oxy-n- alkyl]norborn-5-ene-2,3-dicarboxylate was polymerized via ring opening metathesis polymerization. Two distributed polynorbornene derivatives, both of cis configuration, with different length of side-chain were studied. The influence of thermal history on the smectic phase stabilization, position and shape of the glass transition with temperature and on the relaxation process is shown. Glass transition temperatures enthalpies of isotropization and average layer spacing were calculated. Although, the rather flexible spacer between the mesogenic group and the main chain seems to be sufficient to partially decouple the mobility of the main chain from that of the mesogenic group, the influence of a backbone chain structure is still significant for polymer properties, especially in bulk. The measured layer spacing doe not correspond to double length of the side chain which suggests that either the side chains are not fully extended or some overlapping of CN tails occurs.

  19. Chain Growth Cross Coupling Polymerizations Towards Chiral and Ladder Main Chain Polymers

    DTIC Science & Technology

    2014-11-20

    reactions with low catalyst loading (1 mol%). Rigid ladder polymers with benzocyclobutene backbone linkages can be synthesized from copolymerization of...reactions with low catalyst loading (1 mol%). Rigid ladder polymers with benzocyclobutene backbone linkages can be synthesized from copolymerization...reaction mixture. dPEPPSI-IPr Pd catalyst used. eReaction run for 24 h. fReaction run in THF for 24 h. Our initial attempt on a model reaction between

  20. Fluctuation-induced forces between rings threaded around a polymer chain under tension.

    PubMed

    Gilles, F M; Llubaroff, R; Pastorino, C

    2016-09-01

    We characterize the fluctuation properties of a polymer chain under external tension and the fluctuation-induced forces between two ring molecules threaded around the chain. The problem is relevant in the context of fluctuation-induced forces in soft-matter systems, features of liquid interfaces, and to describe the properties of polyrotaxanes and slide-ring materials. We perform molecular-dynamics simulations of the Kremer-Grest bead-spring model for the polymer and a simple ring-molecule model in the canonical ensemble. We study transverse fluctuations of the stretched chain as a function of chain stretching and in the presence of ring-shaped threaded molecules. The fluctuation spectra of the chains are analyzed in equilibrium at constant temperature, and the differences in the presence of two-ring molecules are compared. For the rings located at fixed distances, we find an attractive fluctuation-induced force between the rings, proportional to the temperature and decaying with the ring distance. We characterize this force as a function of ring distance, chain stretching, and ring radius, and we measure the differences between the free chain spectrum and the fluctuations of the chain constrained by the rings. We also compare the dependence and range of the force found in the simulations with theoretical models coming from different fields.

  1. Correlation functions of main-chain polymer nematics constrained by tensorial and vectorial conservation laws.

    PubMed

    Svenšek, Daniel; Podgornik, Rudolf

    2015-09-21

    We present and analyze correlation functions of a main-chain polymer nematic in a continuum worm-like chain description for two types of constraints formalized by the tensorial and vectorial conservation laws, both originating in the microscopic chain integrity, i.e., the connectivity of the polymer chains. In particular, our aim is to identify the features of the correlation functions that are most susceptible to the differences between the two constraints. Besides the density and director autocorrelations in both the tensorial and vectorial cases, we calculate also the density-director correlation functions, the latter being a direct signature of the presence of a specific constraint. Its amplitude is connected to the strength of the constraint and is zero if none of the constraints are present, i.e., for a standard non-polymeric nematic. Generally, the correlation functions with the constraints differ substantially from the correlation functions in the non-polymeric case, if the constraints are strong which in practice requires long chains. Moreover, for the tensorial conservation law to be well distinguishable from the vectorial one, the chain persistence length should be much smaller than the total length of the chain, so that hairpins (chain backfolding) are numerous and the polar order is small.

  2. On the thermodynamic and kinetic investigations of a [c2]daisy chain polymer

    SciTech Connect

    Hmadeh, Mohamad; Fang, Lei; Trabolsi, Ali; Elhabiri, Mourad; Albrecht-Gary, Anne-Marie; Stoddart, J. Fraser

    2010-01-01

    We report a variety of [c2]daisy chain molecules which undergo quantitative, efficient, and fully reversible molecular movements upon the addition of base/acid in organic solvents. Such externally triggered molecular movements can induce the contraction and extension of the [c2]daisy chain molecule as a whole. A linear polymer of such a bistable [c2]daisy chain exerts similar types of movements and can be looked upon as a candidate for the development of artificial muscles. The spectrophotometric investigations of both the monomeric and polymeric bistable [c2]daisy chains, as well as the corresponding model compounds, were performed in MeCN at room temperature, in order to obtain the thermodynamic parameters for these mechanically interlocked molecules. Based on their spectrophotometric and thermodynamic characteristics, kinetic analysis of the acid/base-induced contraction and extension of the [c2]daisy chain monomer and polymer were conducted by employing a stopped-flow technique. These kinetic data suggest that the rates of contraction and extension for these [c2]daisy chain molecules are determined by the thermodynamic stabilities of the corresponding kinetic intermediates. Faster switching rates for both the contraction and extension processes of the polymeric [c2]daisy chain were observed when compared to those of its monomeric counterpart. These kinetic and thermodynamic investigations on [c2]daisy chain-based muscle-like compounds provide important information for those seeking an understanding of the mechanisms of actuation in mechanically interlocked macromolecules.

  3. Translocation of a polymer chain driven by a dichotomous noise

    NASA Astrophysics Data System (ADS)

    Fiasconaro, Alessandro; José Mazo, Juan; Falo, Fernando

    2011-11-01

    We consider the translocation of a one-dimensional polymer through a pore channel helped by a motor driven by a dichotomous noise with time exponential correlation. We are interested in the study of the translocation time, mean velocity and stall force of the system as a function of the mean driving frequency. We find a monotonic translocation time, in contrast with the mean velocity which shows a pronounced maximum at a given frequency. Interestingly, the stall force shows a nonmonotonic behavior with the presence of a minimum. The influence of the spring elastic constant on the mean translocation times and velocities is also presented.

  4. Entropy-Driven Conformational Control of α,ω-Difunctional Bidentate-Dithiol Azo-Based Adsorbates Enables the Fabrication of Thermally Stable Surface-Grafted Polymer Films.

    PubMed

    Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

    2016-06-22

    Thermally stable radical initiator monolayers were prepared from uniquely designed α,ω-difunctional adsorbates with bidentate headgroups for the growth of nanoscale polymer films on metal surfaces. The length of the spacer separating the bidentate headgroups was varied to afford 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl)-4-cyanopentanamide) (B16), 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercapto-methyl)phenoxy)decyl)-4-cyanopentanamide) (B10), and 4,4'-(diazene-1,2-diyl)bis(N-(4-(3,5-bis(mercaptomethyl)phenoxy)butyl)-4-cyanopentanamide) (B4). The structural features of the self-assembled monolayers (SAMs) derived from B16, B10, and B4 were characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to those derived from an analogous α,ω-difunctional adsorbate with monodentate headgroups, 4,4'-(diazene-1,2-diyl)bis(4-cyano-N-(16-mercaptohexadecyl)pentanamide (M). These studies demonstrate that the conformation (i.e., hairpin vs standing up) of the bidentate initiator adsorbates on gold surfaces was easily controlled by adjusting the concentration of the adsorbates in solution. The results of solution-phase thermal desorption tests revealed that the radical initiator monolayers generated from B16, B10, and B4 exhibit an enhanced thermal stability when compared to those generated from M. Furthermore, a study of the growth of polymer films was performed to evaluate the utility of these new bidentate adsorbate SAMs as film-development platforms for new functional materials and devices. Specifically, surface-grafted polystyrene films were successfully generated from SAMs derived from B16. In contrast, attempts to grow polystyrene films from SAMs derived from M under a variety of analogous conditions were unsuccessful.

  5. Influence of alkyl chain length on the surface activity of antibacterial polymers derived from ROMP.

    PubMed

    Altay, Esra; Yapaöz, Melda Altıkatoğlu; Keskin, Bahadır; Yucesan, Gundoğ; Eren, Tarik

    2015-03-01

    The purpose of this study is to understand the antibacterial properties of cationic polymers on solid surfaces by investigating the structure-activity relationships. The polymer synthesis was carried via ring opening metathesis polymerization (ROMP) of oxanorbornene derivatives. Modulation of molecular weights and alkyl chain lengths of the polymers were studied to investigate the antibacterial properties on the glass surface. Fluorescein (Na salt) staining contact angle measurements were used to characterize the positive charge density and hydrophobicity on the polymer coated surfaces. Positive charge density for the surface coated polymers with molecular weights of 3000 and 10,000 g mol(-1) is observed to be in the range of 2.3-28.5 nmol cm(-2). The ROMP based cationic pyridinium polymer with hexyl unit exhibited the highest bactericidal efficiency against Escherichia coli on solid surface killing 99% of the bacteria in 5 min. However, phenyl and octyl functionalized quaternary pyridinium groups exhibited lower biocidal properties on the solid surfaces compared to their solution phase biocidal properties. Studying the effect of threshold polymer concentrations on the antibacterial properties indicated that changing the concentrations of polymer coatings on the solid surface dramatically influences antibacterial efficiency.

  6. Z-Group ketone chain transfer agents for RAFT polymer nanoparticle modification via hydrazone conjugation

    PubMed Central

    Bandyopadhyay, Saibal; Xia, Xin; Maiseiyeu, Andrei; Mihai, Georgeta; Rajagopalan, Sanjay

    2012-01-01

    A ketal-containing trithiocarbonyl compound has been synthesized and characterized as a chain transfer agent (CTA) in Reversible Addition Fragmentation Transfer (RAFT) polymerization. The ketal functionality does not interfere with RAFT polymerization of acrylate monomers, which proceeds as previously reported to yield macro-CTA polymers and block co-polymers. Post-polymerization ketal cleavage revealed ketone functionality at the polar terminus of an amphiphilic block co-polymer. Hydrazone-formation was facile in both organic solution as well as in aqueous buffer where polymer nanoparticle assemblies were formed, indicating a conjugation/end-functionalization yield of 40–50%. Conjugation was verified with fluorescein, biotin and Gd-DOTA derivatives, and though the trithiocarbonate linkage is hydrolytically labile, we observed stable conjugation for several days at pH 7.4. and 37°C. As expected, streptavidin binding to biotinylated polymer micelles was observed, and size-change based relaxivity increases were observed when Gd-DOTA hydrazide was conjugated to polymer micelles. Cell-uptake of fluorescently labeled polymer micelles was also readily tracked by FACS and fluorescence microscopy. These polymer derivatives demonstrate a range of potential theranostic/biotechnological applications for this conveniently accessible keto-CTA, which include ligand-based nanoparticle targeting and fluorescent/MR nanoparticle contrast agents. PMID:23148126

  7. Side-chain engineering of benzodithiophene-fluorinated quinoxaline low-band-gap co-polymers for high-performance polymer solar cells.

    PubMed

    Xu, Xiaopeng; Wu, Yulei; Fang, Junfeng; Li, Zuojia; Wang, Zhenguo; Li, Ying; Peng, Qiang

    2014-10-06

    A new series of donor-acceptor co-polymers based on benzodithiophene and quinoxaline with various side chains have been developed for polymer solar cells. The effect of the degree of branching and dimensionality of the side chains were systematically investigated on the thermal stability, optical absorption, energy levels, molecular packing, and photovoltaic performance of the resulting co-polymers. The results indicated that the linear and 2D conjugated side chains improved the thermal stabilities and optical absorptions. The introduction of alkylthienyl side chains could efficiently lower the energy levels compared with the alkoxyl-substituted analogues, and the branched alkoxyl side chains could deepen the HOMO levels relative to the linear alkoxyl chains. The branched alkoxyl groups induced better lamellar-like ordering, but poorer face-to-face packing behavior. The 2D conjugated side chains had a negative influence on the crystalline properties of the co-polymers. The performance of the devices indicated that the branched alkoxyl side chains improved the Voc, but decreased the Jsc and fill factor (FF). However, the 2D conjugated side chains would increase the Voc, Jsc, and FF simultaneously. For the first time, our work provides insight into molecular design strategies through side-chain engineering to achieve efficient polymer solar cells by considering both the degree of branching and dimensionality.

  8. Novel Fluorinated Polymers Containing Short Perfluorobutyl Side Chains and Their Super Wetting Performance on Diverse Substrates.

    PubMed

    Jiang, Jingxian; Zhang, Guangfa; Wang, Qiongyan; Zhang, Qinghua; Zhan, Xiaoli; Chen, Fengqiu

    2016-04-27

    Because the emission of perfluorooctanoic acid (PFOA) was completely prohibited in 2015, the widely used poly- and perfluoroalkyl substances with long perfluoroalkyl groups must be substituted by environmentally friendly alternatives. In this study, one kind of potential alternative (i.e., fluorinated polymers with short perfluorobutyl side chains) has been synthesized from the prepared monomers {i.e., (perfluorobutyl)ethyl acrylate (C4A), (perfluorobutyl)ethyl methacrylate (C4MA), 2-[[[[2-(perfluorobutyl)]sulfonyl]methyl]amino]ethyl acrylate (C4SA), and methacrylate (C4SMA)}, and the microstructure, super wetting performance, and applications of the synthesized fluorinated polymers were systematically investigated. The thermal and crystallization behaviors of the fluoropolymer films were characterized by differential scanning calorimetry and wide-angle X-ray diffraction analysis, respectively. Dynamic water-repellent models were constructed. The stable low surface energy and dynamic water- and oil-repellent properties of these synthesized fluorinated polymers with short perfluorobutyl side chains were attributed to the synergetic effect of amorphous fluorinated side chains in perfluoroalkyl acrylate and crystalline hydrocarbon pendant groups in stearyl acrylate. Outstanding water- and oil-repellent properties of fabrics and any other substrates could be achieved by a facile dip-coating treatment using a fluorinated copolymer dispersion. As a result, we believe that our prepared fluorinated copolymers are potential candidates to replace the fluoroalkylated polymers with long perfluorinated chains in nonstick and self-cleaning applications in our daily life.

  9. Novel effects of chain flexibility, external force, and background stochasticity on polymer translocation

    NASA Astrophysics Data System (ADS)

    Sung, Wokyung

    2011-03-01

    The polymer translocation through membranes and the polymer crossing over activation barriers in general, are ubiquitous in cell biology and biotechnological applications. Because they are interconnected flexible systems, polymers in translocation incur entropic barriers but can thermally surmount them with unusual sensitivity to background biases. In the presence of non-equilibrium noises characteristic of living environments, the translocation can speed up much when resonant activation occurs. As a related issue, I will also discuss the problem of polymer surmounting a potential barrier, where the chain flexibility enhances the crossing. Furthermore, when the chain flexibility leads to conformational changes, the crossing rate can be even more dramatically increased. This conformational flexibility and variability enhance the stochastic resonance, where the chain crossing dynamics at an optimal temperature and chain length is maximally coherent and resonant to a minute periodic force. Utilizing the self-organizing behaviors mentioned above, we may learn about bio-molecular machinery of living as well as clever means of manipulating it. Korea Research Foundation.

  10. Role of Chain Morphology and Stiffness in Thermal Conductivity of Amorphous Polymers.

    PubMed

    Zhang, Teng; Luo, Tengfei

    2016-02-04

    Designing thermally conductive polymer is of scientific interest and practical importance for applications like thermal interface materials, electronics packing, and plastic heat exchangers. In this work, we study the fundamental relationship between the molecular morphology and thermal conductivity in bulk amorphous polymers. We use polyethylene as a model system and performed systematic parametric study in molecular dynamics simulations. We find that the thermal conductivity is a strong function of the radius of gyration of the molecular chains, which is further correlated to persistence length, an intrinsic property of the molecule that characterizes molecular stiffness. Larger persistence length can lead to more extended chain morphology and thus higher thermal conductivity. Further thermal conductivity decomposition analysis shows that thermal transport through covalent bonds dominates the effective thermal conductivity over other contributions from nonbonded interactions (van der Waals) and translation of molecules disregarding the morphology. As a result, the more extended chains due to larger persistence length provide longer spatial paths for heat to transfer efficiently and thus lead to higher thermal conductivity. In addition, rigid rod-like polymers with very large persistence length tend to spontaneously crystallize and form orientated chains, leading to a thermal conductivity increase by more than 1 order of magnitude. Our results will provide important insights into the design of thermally conductive amorphous polymers.

  11. Fluorescence properties of a novel side-chain polymer based on polyamic acid

    NASA Astrophysics Data System (ADS)

    Lu, Jianmei; Yao, Shechun; Tang, Xiubo; Sun, Ming; Zhu, Xiulin

    2004-05-01

    The p-π conjugated polyamic acid (PAA) had been synthesized through 1,4-diaminoanthraquinone (DAAQ) and pyromellitic dianhydride (PMDA) under microwave irradiation. The graft PAAs were obtained by toluene-2,4-diisocyanate (TDI) derivatives having different straight-chain alkyl. The resulted graft polymers had good dissolution capabilities, film-forming capabilities and strong fluorescence. We investigated some factors influencing fluorescence performance on graft PAA and found that with increasing chain length of the straight-chain alkyl or increasing graft degree, the fluorescence intensity and quantum efficiency will be enhanced markedly.

  12. Photocurrent enhancement from diketopyrrolopyrrole polymer solar cells through alkyl-chain branching point manipulation.

    PubMed

    Meager, Iain; Ashraf, Raja Shahid; Mollinger, Sonya; Schroeder, Bob C; Bronstein, Hugo; Beatrup, Daniel; Vezie, Michelle S; Kirchartz, Thomas; Salleo, Alberto; Nelson, Jenny; McCulloch, Iain

    2013-08-07

    Systematically moving the alkyl-chain branching position away from the polymer backbone afforded two new thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTT-T) polymers. When used as donor materials in polymer:fullerene solar cells, efficiencies exceeding 7% were achieved without the use of processing additives. The effect of the position of the alkyl-chain branching point on the thin-film morphology was investigated using X-ray scattering techniques and the effects on the photovoltaic and charge-transport properties were also studied. For both solar cell and transistor devices, moving the branching point further from the backbone was beneficial. This is the first time that this effect has been shown to improve solar cell performance. Strong evidence is presented for changes in microstructure across the series, which is most likely the cause for the photocurrent enhancement.

  13. Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites.

    PubMed

    Varol, H Samet; Meng, Fanlong; Hosseinkhani, Babak; Malm, Christian; Bonn, Daniel; Bonn, Mischa; Zaccone, Alessio; Parekh, Sapun H

    2017-04-04

    Polymer nanocomposites-materials in which a polymer matrix is blended with nanoparticles (or fillers)-strengthen under sufficiently large strains. Such strain hardening is critical to their function, especially for materials that bear large cyclic loads such as car tires or bearing sealants. Although the reinforcement (i.e., the increase in the linear elasticity) by the addition of filler particles is phenomenologically understood, considerably less is known about strain hardening (the nonlinear elasticity). Here, we elucidate the molecular origin of strain hardening using uniaxial tensile loading, microspectroscopy of polymer chain alignment, and theory. The strain-hardening behavior and chain alignment are found to depend on the volume fraction, but not on the size of nanofillers. This contrasts with reinforcement, which depends on both volume fraction and size of nanofillers, potentially allowing linear and nonlinear elasticity of nanocomposites to be tuned independently.

  14. The effect of chain rigidity on the interfacial layer thickness and dynamics of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Carrillo, Jan-Michael Y.; Carroll, Bobby; Sumpter, Bobby G.; Sokolov, Alexei P.

    There are growing experimental evidences showing the existence of an interfacial layer that has a finite thickness with slowing down dynamics in polymer nanocomposites (PNCs). Moreover, it is believed that the interfacial layer plays a significant role on various macroscopic properties of PNCs. A thicker interfacial layer is found to have more pronounced effect on the macroscopic properties such as the mechanical enhancement. However, it is not clear what molecular parameter controls the interfacial layer thickness. Inspired by our recent computer simulations that showed the chain rigidity correlated well with the interfacial layer thickness, we performed systematic experimental studies on different polymer nanocomposites by varying the chain stiffness. Combining small-angle X-ray scattering, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry, we find a good correlation between the polymer Kuhn length and the thickness of the interfacial layer, confirming the earlier computer simulations results. Our findings provide a direct guidance for the design of new PNCs with desired properties.

  15. Main chain acid-degradable polymers for the delivery of bioactive materials

    DOEpatents

    Frechet, Jean M. J. [Oakland, CA; Standley, Stephany M [Evanston, IL; Jain, Rachna [Milpitas, CA; Lee, Cameron C [Cambridge, MA

    2012-03-20

    Novel main chain acid degradable polymer backbones and drug delivery systems comprised of materials capable of delivering bioactive materials to cells for use as vaccines or other therapeutic agents are described. The polymers are synthesized using monomers that contain acid-degradable linkages cleavable under mild acidic conditions. The main chain of the resulting polymers readily degrade into many small molecules at low pH, but remain relatively stable and intact at physiological pH. The new materials have the common characteristic of being able to degrade by acid hydrolysis under conditions commonly found within the endosomal or lysosomal compartments of cells thereby releasing their payload within the cell. The materials can also be used for the delivery of therapeutics to the acidic regions of tumors and other sites of inflammation.

  16. The effect of chain length on protein solubilization in polymer-based vesicles (polymersomes).

    PubMed

    Pata, Veena; Dan, Nily

    2003-10-01

    Using a mean-field analysis we derive a consistent model for the perturbation of a symmetric polymeric bilayer due to the incorporation of transmembrane proteins, as a function of the polymer molecular weight and the protein dimensions. We find that the mechanism for the inhibition of protein incorporation in polymeric bilayers differs from that of their inclusion in polymer-carrying lipid vesicles; in polymersomes, the equilibrium concentration of transmembrane proteins decreases as a function of the thickness mismatch between the protein and the bilayer core, whereas in liposomes the presence of polymer chains affects the protein adsorption kinetics. Despite the increased stiffness of polymer bilayers (when compared to lipid ones), their perturbation decay length and range of protein-protein interaction is found to be relatively long. The energetic penalty due to protein adsorption increases relatively slowly as a function of the polymer chain length due to the self-assembled nature of the polymer bilayer. As a result, we predict that transmembrane proteins may be incorporated in significant numbers even in bilayers where the thickness mismatch is large.

  17. Impact of systematic chain architecture changes on the glass transition and modulus of thin polymer films

    NASA Astrophysics Data System (ADS)

    Vogt, Bryan; Torres, Jessica; Stafford, Christopher; Register, Richard; Uhrig, David

    2012-02-01

    We will discuss two systems that significantly impact the thin film behavior with minor changes in chemistry and chain architecture. First, two polymers based on 5-(2-phenylethylnorbornene) are examined. Depending on the polymerization route chosen, the resulting polymer backbone is comprised of either bicyclic (norbornyl) units, which leads to a relatively rigid polymer with a high bulk Tg, or monocyclic (cyclopentyl) units, which leads to a more flexible structure with a lower bulk Tg. The modulus and Tg of the rigid bicyclic polymer is thickness independent down to <10 nm, whereas the modulus of the more flexible monocyclic polymer decreases with decreasing thickness. By hydrogenation of the pendant phenyl ring to the cyclohexyl counterpart, we illustrate that minor changes in the relative flexibility of the side chain do not impact the observed thin film behavior. Second, a series of polystyrene with controlled branching including linear, comb, 6-arm star and centipede. Based upon the molecular mass of the arms, the comb polymer has a significantly larger persistence length and interestingly exhibits only a modest decrease in Tg (9 K) at 5 nm, while the moduli is thickness independent.

  18. Comparison of the kinetics of chain aggregation and chain collapse in dilute polymer solutions.

    PubMed

    Maki, Yasuyuki; Dobashi, Toshiaki; Nakata, Mitsuo

    2008-10-01

    The rates of chain aggregation of poly(methyl methacrylate) (PMMA) in acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol%) were determined by static light scattering and compared with the rates of chain collapse [Maki, J. Chem. Phys. 126, 134901 (2007)]. Dilute solutions of PMMA with the molecular weight m{w}=6.4 x 10{6} and in the concentration range of (0.8-5)x10;{-4}gcm;{3} were quenched below the cloud point, and the weight-average molecular weight M{w} and z -average square radius of gyration S;{2}_{z} for clusters of PMMA chains were measured as a function of the time t after the quench and the concentration c . The measurement of chain aggregation was carried out up to the cluster size of M{w}m{w} approximately 30 , which required time periods of hours to several days depending on the concentration and solvent. The chain aggregation in AcN+water occurred much faster than that in AcN. The growth of clusters in both the solvents was represented by the exponential function as M{w} approximately e;{gct} and S;{2}_{z} approximately e{hct} , where g and h represent the intrinsic rate of chain aggregation. The ratio sigma of the intrinsic rate in AcN+water to that in AcN was estimated to be 9 by taking a rough average of the ratios 9.4 obtained from g and 8.8 from h . This value is comparable to the ratio 11 of the rate of chain collapse of PMMA in AcN+water (10 vol%) to that in AcN. This close value of the ratios indicates that the nature of solvent would affect the rates of chain collapse and chain aggregation through a similar mechanism.

  19. Ring polymer chains confined in a slit geometry of two parallel walls: the massive field theory approach

    NASA Astrophysics Data System (ADS)

    Usatenko, Z.; Halun, J.

    2017-01-01

    The investigation of a dilute solution of phantom ideal ring polymer chains confined in a slit geometry of two parallel repulsive walls, two inert walls, and for the mixed case of one inert and the other one repulsive wall, was performed. Taking into account the well known correspondence between the field theoretical {φ4} O(n)-vector model in the limit n\\to 0 and the behaviour of long-flexible polymer chains in a good solvent, the investigation of a dilute solution of long-flexible ring polymer chains with the excluded volume interaction (EVI) confined in a slit geometry of two parallel repulsive walls was performed in the framework of the massive field theory approach at fixed space dimensions d  =  3 up to one-loop order. For all the above mentioned cases, the correspondent depletion interaction potentials, the depletion forces and the forces which exert the phantom ideal ring polymers and the ring polymers with the EVI on the walls were calculated, respectively. The obtained results indicate that the phantom ideal ring polymer chains and the ring polymer chains with the EVI due to the complexity of chain topology and because of the entropical reason demonstrate completely different behaviour in confined geometries than linear polymer chains. For example, the phantom ideal ring polymers prefer to escape from the space not only between two repulsive walls but also in the case of two inert walls, which leads to the attractive depletion forces. The ring polymer chains with less complex knot types (with the bigger radius of gyration) in a ring topology in the wide slit region exert higher forces on the confining repulsive walls. The depletion force in the case of mixed boundary conditions becomes repulsive in contrast to the case of linear polymer chains.

  20. A Microscopic Model for Diffusion of a Polymer Chain in the Entangled Regime

    NASA Astrophysics Data System (ADS)

    Canpolat, Murat; Erzan, Ayþe; Pekcan, Önder

    1997-01-01

    In the entangled regime the reptation concept [1,2] is the most successful in describing the dynamical behavior of a single chain. Using scaling concepts some quantities such as translational diffussion coefficient for the polymer center of mass Dtr, and renewal time {t} [3] have been calculated in the reptation model. This model is used for representing the low-frequency motions of a polymer molecule in a fluid of entangled chains, neglecting rapid relaxation processes that are attributed to local conformal transitions of backbone. Helfand and collabrators have studied the kinetics of conformational transitions in chain molecules, and they find that single-bond rotations followed by the compensating rearrangement of neigboring units are predominantly responsible for local motions [4]. Such models have also been considered by Erman and co-workers [5]. The purpose of this study to understand reptation at a microscopic level. We consedir rapid relaxation processes, that are singlet- or double -bond rotations; motion along the contour of the chain is due to displacments caused by rearangements of the neighboring units. We recover the usual scaling behavior of the diffusion coefficients and relaxation times with the chain mass. Moreover, the effective activation energy that is found from the local jump model for translational motion of the chain center of mass compares favorably with experiment and is independent of the molecular weight for large enough chains [6]. We are also able to account for the apparent temperature of this "activation energy".

  1. Molecular dynamics simulations of end-grafted centipede-like polymers with stiff charged side chains.

    PubMed

    Cao, Q Q; Zuo, C C; Li, L J

    2010-05-01

    We use molecular dynamics simulations to investigate centipede-like polymers with stiff charged side chains, end-grafted to a planar wall. The effect of the grafting density and the Bjerrum length on the conformational behaviour of the brush is examined in detail. In addition, we make a comparison of centipede-like polyelectrolyte (CPE) brushes with neutral centipede-like polymer (NCP) and linear polyelectrolyte (LPE) brushes. At weak electrostatic interaction, the main chains of the CPE chains adopt a strongly stretched conformation, and the monomer density profiles of side chains exhibit a clear oscillatory behaviour. With increasing Bjerrum length, the CPE brush undergoes a collapse transition. Compared to the CPE brushes, the counterion condensation effect is stronger for the LPE brushes, regardless of whether the electrostatic interaction is weak or strong and of whether the grafting density is low or high. Additionally, it is shown that the architecture of the grafted chains makes a weak contribution to the counterion condensation at strong electrostatic interaction. We also find that the electrostatic repulsion between charged side chains can enhance the stiffness of the main chains and thus limit the range of movement of the free-end monomers.

  2. Phase transitions of a single polymer chain: A Wang-Landau simulation study.

    PubMed

    Taylor, Mark P; Paul, Wolfgang; Binder, Kurt

    2009-09-21

    A single flexible homopolymer chain can assume a variety of conformations which can be broadly classified as expanded coil, collapsed globule, and compact crystallite. Here we study transitions between these conformational states for an interaction-site polymer chain comprised of N=128 square-well-sphere monomers with hard-sphere diameter sigma and square-well diameter lambdasigma. Wang-Landau sampling with bond-rebridging Monte Carlo moves is used to compute the density of states for this chain and both canonical and microcanonical analyses are used to identify and characterize phase transitions in this finite size system. The temperature-interaction range (i.e., T-lambda) phase diagram is constructed for lambdaChains assume an expanded coil conformation at high temperatures and a crystallite structure at low temperatures. For lambda>1.06 these two states are separated by an intervening collapsed globule phase and thus, with decreasing temperature a chain undergoes a continuous coil-globule (collapse) transition followed by a discontinuous globule-crystal (freezing) transition. For well diameters lambda<1.06 the collapse transition is pre-empted by the freezing transition and thus there is a direct first-order coil-crystal phase transition. These results confirm the recent prediction, based on a lattice polymer model, that a collapsed globule state is unstable with respect to a solid phase for flexible polymers with sufficiently short-range monomer-monomer interactions.

  3. Entangled polymer chain melts: orientation and deformation dependent tube confinement and interchain entanglement elasticity.

    PubMed

    Sussman, Daniel M; Schweizer, Kenneth S

    2013-12-21

    The phenomenological reptation-tube model is based on a single chain perspective and was originally proposed to explain the remarkable viscoelastic properties of dense entangled polymer liquids. However, simulations over the last two decades have revealed a fundamental tension in the model: it assumes that bonded, single-chain backbone stresses are the sole polymer contribution to the slowly relaxing component of stress storage and elasticity, but mounting evidence suggests that at the local level of forces it is interchain contributions that dominate, as in simple liquids. Here we show that based on a chain model constructed at the level of self-consistently determined primitive paths, an explicit force-level treatment of the correlated intermolecular contributions to stress that arise from chain uncrossability can essentially quantitatively predict the entanglement plateau modulus associated with the soft rubbery response of polymer liquids. Analogies to transient localization and elasticity in glass-forming liquids are identified. Predictions for the effect of macroscopic deformation and anisotropic orientational order on the tube diameter are also made. Based on the interchain stress perspective the theory reproduces some aspects of the rheological response to shear and extensional deformations associated with the single chain tube model.

  4. Brownian dynamics simulations of a flexible polymer chain which includes continuous resistance and multibody hydrodynamic interactions.

    PubMed

    Butler, Jason E; Shaqfeh, Eric S G

    2005-01-01

    Using methods adapted from the simulation of suspension dynamics, we have developed a Brownian dynamics algorithm with multibody hydrodynamic interactions for simulating the dynamics of polymer molecules. The polymer molecule is modeled as a chain composed of a series of inextensible, rigid rods with constraints at each joint to ensure continuity of the chain. The linear and rotational velocities of each segment of the polymer chain are described by the slender-body theory of Batchelor [J. Fluid Mech. 44, 419 (1970)]. To include hydrodynamic interactions between the segments of the chain, the line distribution of forces on each segment is approximated by making a Legendre polynomial expansion of the disturbance velocity on the segment, where the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution is specified by a center of mass force, couple, and stresslet on each segment. This method for calculating the hydrodynamic interactions has been successfully used to simulate the dynamics of noncolloidal suspensions of rigid fibers [O. G. Harlen, R. R. Sundararajakumar, and D. L. Koch, J. Fluid Mech. 388, 355 (1999); J. E. Butler and E. S. G. Shaqfeh, J. Fluid Mech. 468, 204 (2002)]. The longest relaxation time and center of mass diffusivity are among the quantities calculated with the simulation technique. Comparisons are made for different levels of approximation of the hydrodynamic interactions, including multibody interactions, two-body interactions, and the "freely draining" case with no interactions. For the short polymer chains studied in this paper, the results indicate a difference in the apparent scaling of diffusivity with polymer length for the multibody versus two-body level of approximation for the hydrodynamic interactions.

  5. Brownian dynamics simulations of a flexible polymer chain which includes continuous resistance and multibody hydrodynamic interactions

    NASA Astrophysics Data System (ADS)

    Butler, Jason E.; Shaqfeh, Eric S. G.

    2005-01-01

    Using methods adapted from the simulation of suspension dynamics, we have developed a Brownian dynamics algorithm with multibody hydrodynamic interactions for simulating the dynamics of polymer molecules. The polymer molecule is modeled as a chain composed of a series of inextensible, rigid rods with constraints at each joint to ensure continuity of the chain. The linear and rotational velocities of each segment of the polymer chain are described by the slender-body theory of Batchelor [J. Fluid Mech. 44, 419 (1970)]. To include hydrodynamic interactions between the segments of the chain, the line distribution of forces on each segment is approximated by making a Legendre polynomial expansion of the disturbance velocity on the segment, where the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution is specified by a center of mass force, couple, and stresslet on each segment. This method for calculating the hydrodynamic interactions has been successfully used to simulate the dynamics of noncolloidal suspensions of rigid fibers [O. G. Harlen, R. R. Sundararajakumar, and D. L. Koch, J. Fluid Mech. 388, 355 (1999); J. E. Butler and E. S. G. Shaqfeh, J. Fluid Mech. 468, 204 (2002)]. The longest relaxation time and center of mass diffusivity are among the quantities calculated with the simulation technique. Comparisons are made for different levels of approximation of the hydrodynamic interactions, including multibody interactions, two-body interactions, and the "freely draining" case with no interactions. For the short polymer chains studied in this paper, the results indicate a difference in the apparent scaling of diffusivity with polymer length for the multibody versus two-body level of approximation for the hydrodynamic interactions.

  6. Thermochromism of a Poly(phenylene vinylene): Untangling the Roles of Polymer Aggregate and Chain Conformation

    SciTech Connect

    Cotlet, M.; Wang, C.-C.; Gao, Y.; Shreve, A.P.; Zhong, C.; Wang, L.; Mudalige, K.; Wang, H.-L.

    2009-12-17

    We report reversible thermochromism of a conjugated polymer, poly{l_brace}2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-1,4-phenylenevinylene{r_brace} (DAO-PPV), in diluted solutions of toluene and 1,2-dichlorobenzene. By means of temperature- and solvent-dependent steady-state spectroscopy, picosecond time-resolved photoluminescence spectroscopy, and dynamic light scattering, we provide new insights into the role of polymer aggregates in defining the thermochromic behavior of PPVs. We find DAO-PPV to exhibit a low temperature state with vibronically structured red visible absorption and emission spectra. Structurally, this low temperature state is a densely packed and disordered polymer aggregate, which contains a fraction of well-ordered, packed polymer chains. These ordered regions serve as low energy trap sites for the more disordered regions in the aggregate, thus regulating the final emission of the aggregate and imposing a vibronically resolved emission spectrum, which is usually associated with emission from one or a few chromophores. The high temperature state of DAO-PPV is a loose aggregate, with structureless absorption and emission spectra in the green visible range. Structurally, the loose aggregate is a well-solvated aggregate retaining the physical dimension of the dense aggregate but for which interchain interactions are diminished with the increase of temperature. As a result, the spectroscopic behavior of the loose aggregate is very similar if not identical to that of the single polymer chain. Increased solubility untangles polymer aggregates into single, dispersed, polymer chains, as we demonstrate here for DAO-PPV in 1,2-dichlorobenzene and at high temperature.

  7. Intrinsic electrical conductivity of nanostructured metal-organic polymer chains

    PubMed Central

    Hermosa, Cristina; Vicente Álvarez, Jose; Azani, Mohammad-Reza; Gómez-García, Carlos J.; Fritz, Michelle; Soler, Jose M.; Gómez-Herrero, Julio; Gómez-Navarro, Cristina; Zamora, Félix

    2013-01-01

    One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 104 S m−1, three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices. PMID:23591876

  8. Modular and dynamic approaches to the formation of single-chain polymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Tuten, Bryan Tyler

    The methodology towards the creation of nanoscale polymeric objects by way of the folding of single polymer chains has been enjoying success in the field of polymer chemistry and materials science. By synthesizing polymer chains with built in functionality either through functional side groups, or direct incorporation into the polymer backbone, polymer chemists are able to fold single polymer chains onto themselves through a broad range of covalent and non-covalent interactions in dilute solution. These compact, nano-sized objects can now be used in a wide arrange of functions and applications. The aim of this dissertation is to provide first, a comprehensive overview of the recent advances and success enjoyed by this field and second, to showcase some of the various routes towards the dynamic and modular creation of these single-chain polymer nanoparticles (SCNPs). Chapter 2 of this work discusses the use of dynamic covalent cross-linking chemistry via reversible disulfide bridges in the folding and unfolding of SCNPs. Through the use of triple detection size-exclusion chromatography (SEC) it was shown through changes in retention time, a phenomena indicative of hydrodynamic volume, a polymer was being folded into compact SCNPs and then unfolded and refolded via redox chemistry. Chapter 3 explores the design of polymers that had various different cross-linkable moieties incorporated into the monomer side units. By having cross-linkable moieties that can undergo different chemical cross-linking reactions (i.e thiol-yne click reactions, epoxide ring-opening reactions, activated esters), a modular approach towards the folding and subsequent functionalization of SCNPs is created. Looking to design a system with a greater degree of control over the modular functionality, chapter 4 investigates the use of norbornene imide monomers containing pentafluorophenyl activated esters with varying methylene spacer unites between the polymerizable olefin and the activated ester

  9. Bis(thienothiophenyl) diketopyrrolopyrrole-based conjugated polymers with various branched alkyl side chains and their applications in thin-film transistors and polymer solar cells.

    PubMed

    Shin, Jicheol; Park, Gi Eun; Lee, Dae Hee; Um, Hyun Ah; Lee, Tae Wan; Cho, Min Ju; Choi, Dong Hoon

    2015-02-11

    New thienothiophene-flanked diketopyrrolopyrrole and thiophene-containing π-extended conjugated polymers with various branched alkyl side-chains were successfully synthesized. 2-Octyldodecyl, 2-decyltetradecyl, 2-tetradecylhexadecyl, 2-hexadecyloctadecyl, and 2-octadecyldocosyl groups were selected as the side-chain moieties and were anchored to the N-positions of the thienothiophene-flanked diketopyrrolopyrrole unit. All five polymers were found to be soluble owing to the bulkiness of the side chains. The thin-film transistor based on the 2-tetradecylhexadecyl-substituted polymer showed the highest hole mobility of 1.92 cm2 V(-1) s(-1) due to it having the smallest π-π stacking distance between the polymer chains, which was determined by grazing incidence X-ray diffraction. Bulk heterojunction polymer solar cells incorporating [6,6]-phenyl-C71-butyric acid methyl ester as the n-type molecule and the additive 1,8-diiodooctane (1 vol %) were also constructed from the synthesized polymers without thermal annealing; the device containing the 2-octyldodecyl-substituted polymer exhibited the highest power conversion efficiency of 5.8%. Although all the polymers showed similar physical properties, their device performance was clearly influenced by the sizes of the branched alkyl side-chain groups.

  10. Critical Behavior of Two Interacting Linear Polymer Chains in a Good Solvent

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Singh, Yashwant

    1997-12-01

    A model of two interacting (chemically different) linear polymer chains is solved exactly using the real-space renormalization group transformation on a family of Sierpinski gasket type fractals and on a truncated 4-simplex lattice. The members of the family of the Sierpinski gasket-type fractals are characterized by an integer scale factor b which runs from 2 to ∞. The Hausdorff dimension d F of these fractals tends to 2 from below as b → ∞. We calculate the contact exponent y for the transition from the State of segregation to a State in which the two chains are entangled for b = 2-5. Using arguments based on the finite-size scaling theory, we show that for b→∞, y = 2 - v(b) d F, where v is the end-toend distance exponent of a chain. For a truncated 4-simplex lattice it is shown that the system of two chains either remains in a State in which these chains are intermingled in such a way that they cannot be told apart, in the sense that the chemical difference between the polymer chains completely drop out of the thermodynamics of the system, or in a State in which they are either zipped or entangled. We show the region of existence of these different phases separated by tricritical lines. The value of the contact exponent y is calculated at the tricritical points.

  11. Polymer translocation through a nanopore driven by binding particles: Influence of chain rigidity

    NASA Astrophysics Data System (ADS)

    Yu, Wancheng; Luo, Kaifu

    2014-10-01

    We investigate the influence of chain rigidity on the dynamics of polymer translocation in the presence of binding particles (BPs) through a nanopore using two-dimensional Langevin dynamics simulations. With increasing chain rigidity κ, the mean translocation time <τ> increases monotonically due to an increase in the radius of gyration and a decrease in the center of mass velocity. Particularly for weak binding, we further find that <τ> shows a power-law behavior with the persistence length lp. Analysis indicates a scaling relation between the average velocity of the center of mass of a chain and lp. As the chain becomes stiffer, the distribution of the translocation time τ approximates the Gaussian distribution and gets broader with the peak position being shifted towards longer translocation time. The corresponding translocation coordinate smax of the maximum waiting time gets smaller with increasing chain rigidity. Finally, under an extremely low BP concentration, <τ> shows a minimum for small κ, while it decreases monotonically for large κ with increasing binding energy. Our results suggest a nontrivial effect of the intrinsic property of chains on the dynamics of polymer translocation driven by BPs.

  12. Pruned-enriched Rosenbluth method: Simulations of {theta} polymers of chain length up to 1000000

    SciTech Connect

    Grassberger, P. |

    1997-09-01

    We present an algorithm for simulating flexible chain polymers. It combines the Rosenbluth-Rosenbluth method with recursive enrichment. Although it can be applied also in more general situations, it is most efficient for three-dimensional {theta} polymers on the simple-cubic lattice. There it allows high statistics simulations of chains of length up to N=10{sup 6}. For storage reasons, this is feasable only for polymers in a finite volume. For free {theta} polymers in infinite volume, we present very high statistics runs with N=10000. These simulations fully agree with previous simulations made by Hegger and Grassberger [J. Chem. Phys. {bold 102}, 6681 (1995)] with a similar but less efficient algorithm, showing that logarithmic corrections to mean field behavior are much stronger than predicted by field theory. But the finite volume simulations show that the density inside a collapsed globule scales with the distance from the {theta} point as predicted by mean field theory, in contrast to claims in the work mentioned above. In addition to the simple-cubic lattice, we also studied two versions of the bond fluctuation model, but with much shorter chains. Finally, we show that our method can be applied also to off-lattice models, and illustrate this with simulations of a model studied in detail by Freire {ital et al.} [Macromolecules {bold 19}, 452 (1986) and later work]. {copyright} {ital 1997} {ital The American Physical Society}

  13. Beads on a string: structure of bound aggregates of globular particles and long polymer chains.

    PubMed

    Souslov, Anton; Curtis, Jennifer E; Goldbart, Paul M

    2015-11-07

    Macroscopic properties of suspensions, such as those composed of globular particles (e.g., colloidal or macromolecular), can be tuned by controlling the equilibrium aggregation of the particles. We examine how aggregation - and, hence, macroscopic properties - can be controlled in a system composed of both globular particles and long, flexible polymer chains that reversibly bind to one another. We base this on a minimal statistical mechanical model of a single aggregate in which the polymer chain is treated either as ideal or self-avoiding, and, in addition, the globular particles are taken to interact with one another via excluded volume repulsion. Furthermore, each of the globular particles is taken to have one single site to which at most one polymer segment may bind. Within the context of this model, we examine the statistics of the equilibrium size of an aggregate and, thence, the structure of dilute and semidilute suspensions of these aggregates. We apply the model to biologically relevant aggregates, specifically those composed of macromolecular proteoglycan globules and long hyaluronan polymer chains. These aggregates are especially relevant to the materials properties of cartilage and the structure-function properties of perineuronal nets in brain tissue, as well as the pericellular coats of mammalian cells.

  14. Boosting the ambipolar performance of solution-processable polymer semiconductors via hybrid side-chain engineering.

    PubMed

    Lee, Junghoon; Han, A-Reum; Yu, Hojeong; Shin, Tae Joo; Yang, Changduk; Oh, Joon Hak

    2013-06-26

    Ambipolar polymer semiconductors are highly suited for use in flexible, printable, and large-area electronics as they exhibit both n-type (electron-transporting) and p-type (hole-transporting) operations within a single layer. This allows for cost-effective fabrication of complementary circuits with high noise immunity and operational stability. Currently, the performance of ambipolar polymer semiconductors lags behind that of their unipolar counterparts. Here, we report on the side-chain engineering of conjugated, alternating electron donor-acceptor (D-A) polymers using diketopyrrolopyrrole-selenophene copolymers with hybrid siloxane-solubilizing groups (PTDPPSe-Si) to enhance ambipolar performance. The alkyl spacer length of the hybrid side chains was systematically tuned to boost ambipolar performance. The optimized three-dimensional (3-D) charge transport of PTDPPSe-Si with pentyl spacers yielded unprecedentedly high hole and electron mobilities of 8.84 and 4.34 cm(2) V(-1) s(-1), respectively. These results provide guidelines for the molecular design of semiconducting polymers with hybrid side chains.

  15. Effect of bending stiffness and confinement on a polymer chain under tension

    NASA Astrophysics Data System (ADS)

    Poier, Peter; Likos, Christos N.; Matthews, Richard

    2014-03-01

    Type II topoisomerase are enzymes that (un)knot DNA. There is experimental evidence that a certain type II topoisomerase preferentially cleaves adenine (A) and thymine (T) rich regions of the DNA. It is believed that AT-rich sequences are more flexible than random ones. This raises the question of whether the flexibility of the preferred cleavage sites of topoisomerase II could play an important role in the regulation of knotting. With this motivation we study the effect of the bending stiffness and confinement on the free-energy cost of a knot in a polymer chain under tension. For the polymer chain we use a coarse-grained model. Via thermodynamic-integration we calculate the change of the free-energy cost of a knot due to modifications of the bending stiffness. The free-energy cost exhibits a minimum at a non-zero value for the bending stiffness. Our simulations suggest that this minimum is related to a suppression of the bending at the points where the strands of the polymer cross in the knotted region. We study how the minimum of the free-energy cost is affected by changing the knot type and introducing a two dimensional confinement for the polymer chain. The results of this work might be of importance for the localization of knots in DNA.

  16. Polymer chain length effects on fibroblast attachment on nylon-3-modified surfaces.

    PubMed

    Liu, Runhui; Masters, Kristyn S; Gellman, Samuel H

    2012-04-09

    Nylon-3 polymers have a polyamide backbone reminiscent of that found in proteins (β- vs α-amino acid residues, respectively), which makes these materials interesting for biological applications. Because of the versatility of the ring-opening polymerization process and the variety of β-lactam starting materials available, the structure of nylon-3 copolymers is highly amenable to alteration. A previous study showed that relatively subtle changes in the structure or ratio of hydrophobic and cationic subunits that comprise these polymers can result in significant changes in the ability of nylon-3-bearing surfaces to support cell adhesion and spreading. In the present study, we have exploited the highly tailorable nature of these polymers to synthesize new versions possessing a wide range of chain lengths, with the intent of optimizing these materials for use as cell-supportive substrates. We find that longer nylon-3 chains lead to better fibroblast attachment on modified surfaces and that at the optimal chain lengths less hydrophobic subunits are superior. The best polymers we identified are comparable to an RGD-containing peptide in supporting fibroblast attachment. The results described here will help to focus future efforts aimed at refining nylon-3 copolymer substrates for specific tissue engineering applications.

  17. Communication: Role of short chain branching in polymer structure and dynamics.

    PubMed

    Kim, Jun Mo; Baig, Chunggi

    2016-02-28

    A comprehensive understanding of chain-branching effects, essential for establishing general knowledge of the structure-property-phenomenon relationship in polymer science, has not yet been found, due to a critical lack of knowledge on the role of short-chain branches, the effects of which have mostly been neglected in favor of the standard entropic-based concepts of long polymers. Here, we show a significant effect of short-chain branching on the structural and dynamical properties of polymeric materials, and reveal the molecular origins behind the fundamental role of short branches, via atomistic nonequilibrium molecular dynamics and mesoscopic Brownian dynamics by systematically varying the strength of the mobility of short branches. We demonstrate that the fast random Brownian kinetics inherent to short branches plays a key role in governing the overall structure and dynamics of polymers, leading to a compact molecular structure and, under external fields, to a lesser degree of structural deformation of polymer, to a reduced shear-thinning behavior, and to a smaller elastic stress, compared with their linear analogues. Their fast dynamical nature being unaffected by practical flow fields owing to their very short characteristic time scale, short branches would substantially influence (i.e., facilitate) the overall relaxation behavior of polymeric materials under various flowing conditions.

  18. The Role of Chain Length in Nonergodicity Factor and Fragility of Polymers

    SciTech Connect

    Sokolov, Alexei P

    2010-01-01

    The mechanism that leads to different fragility values upon approaching the glass transition remains a topic of active discussion. Many researchers are trying to find an answer in the properties of the frozen glassy state. Following this approach, we focus here on a previously proposed relationship between the fragility of glass-formers and their nonergodicity factor, determined by inelastic X-ray scattering (IXS) in the glass. We extend this molecular liquid study to two model polymers; polystyrene (PS) and polyisobutylene (PIB);for which we change the molecular weight. Polymers offer the opportunity to change the fragility without altering the chemical structure, just by changing the chain length. Thus, we specifically chose PS and PIB because they exhibit opposite dependences of fragility with molecular weight. Our analysis for these two polymers reveals no unique correlation between the fragility and the nonergodicity parameter. Even after a recently suggested correction for a possible contribution of the relaxation, the correlation is not restored. We discuss possible causes for the failure of the fragility-nonergodicity factor correlation, emphasizing the features that are specific to polymers. We speculate that polymers might have specific contributions to fragility related to the chain connectivity that are absent in nonpolymeric systems.

  19. In situ study on the reorientation of polymer chains in operating polymer diodes

    NASA Astrophysics Data System (ADS)

    Guo, Tzung-Fang; Yang, Yang

    2002-01-01

    A reflection-absorption Fourier-transform infrared spectroscopy experiment has been designed to in situ monitor poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV)-based polymer light-emitting diodes under stress test. This method enables the in situ study of the co-relation between device performance and the conformational transformation of a conjugated polymer. The experimental results indicate that the plane of the conjugated π-electron cloud in MEH-PPV tends to align parallel to the substrate. This rearrangement enhances the π-π electron coupling and lowers the device operating voltage under high current densities.

  20. Lattice model of linear telechelic polymer melts. I. Inclusion of chain semiflexibility in the lattice cluster theory

    SciTech Connect

    Xu, Wen-Sheng; Freed, Karl F.

    2015-07-14

    The lattice cluster theory (LCT) for the thermodynamics of polymer systems has recently been reformulated to treat strongly interacting self-assembling polymers composed of fully flexible linear telechelic chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)]. Here, we further extend the LCT for linear telechelic polymer melts to include a description of chain semiflexibility, which is treated by introducing a bending energy penalty whenever a pair of consecutive bonds from a single chain lies along orthogonal directions. An analytical expression for the Helmholtz free energy is derived for the model of semiflexible linear telechelic polymer melts. The extension provides a theoretical tool for investigating the influence of chain stiffness on the thermodynamics of self-assembling telechelic polymers, and for further exploring the influence of self-assembly on glass formation in such systems.

  1. Determination of imidazole derivatives by micellar electrokinetic chromatography combined with solid-phase microextraction using activated carbon-polymer monolith as adsorbent.

    PubMed

    Shih, Yung-Han; Lirio, Stephen; Li, Chih-Keng; Liu, Wan-Ling; Huang, Hsi-Ya

    2016-01-08

    In this study, an effective method for the separation of imidazole derivatives 2-methylimidazole (2-MEI), 4- methylimidazole (4-MEI) and 2-acetyl-4-tetrahydroxybutylimidazole (THI) in caramel colors using cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-sweeping-MEKC) was developed. The limits of detection (LOD) and quantitation (LOQ) for the CSEI-sweeping-MEKC method were in the range of 4.3-80μgL(-1) and 14-270μgL(-1), respectively. Meanwhile, a rapid fabrication activated carbon-polymer (AC-polymer) monolithic column as adsorbent for solid-phase microextraction (SPME) of imidazole colors was developed. Under the optimized SPME condition, the extraction recoveries for intra-day, inter-day and column-to-column were in the range of 84.5-95.1% (<6.3% RSDs), 85.6-96.1% (<4.9% RSDs), and 81.3-96.1% (<7.1% RSDs), respectively. The LODs and LOQs of AC-polymer monolithic column combined with CSEI-sweeping-MEKC method were in the range of 33.4-60.4μgL(-1) and 111.7-201.2μgL(-1), respectively. The use of AC-polymer as SPME adsorbent demonstrated the reduction of matrix effect in food samples such as soft drink and alcoholic beverage thereby benefiting successful determination of trace-level caramel colors residues using CSEI-sweeping-MEKC method. The developed AC-polymer monolithic column can be reused for more than 30 times without any significant loss in the extraction recovery for imidazole derivatives.

  2. End-anchored polymers in good solvents from the single chain limit to high anchoring densities

    NASA Astrophysics Data System (ADS)

    Whitmore, Mark D.; Grest, Gary S.; Douglas, Jack F.; Kent, Michael S.; Suo, Tongchuan

    2016-11-01

    An increasing number of applications utilize grafted polymer layers to alter the interfacial properties of solid substrates, motivating refinement in our theoretical understanding of such layers. To assess existing theoretical models of them, we have investigated end-anchored polymer layers over a wide range of grafting densities, σ, ranging from a single chain to high anchoring density limits, chain lengths ranging over two orders of magnitude, for very good and marginally good solvent conditions. We compare Monte Carlo and molecular dynamics simulations, numerical self-consistent field calculations, and experimental measurements of the average layer thickness, h, with renormalization group theory, the Alexander-de Gennes mushroom theory, and the classical brush theory. Our simulations clearly indicate that appreciable inter-chain interactions exist at all simulated areal anchoring densities so that there is no mushroom regime in which the layer thickness is independent of σ. Moreover, we find that there is no high coverage regime in which h follows the predicted scaling, h ˜ Nσ1/3, for classical polymer brushes either. Given that no completely adequate analytic theory seems to exist that spans wide ranges of N and σ, we applied scaling arguments for h as a function of a suitably defined reduced anchoring density, defined in terms of the solution radius of gyration of the polymer chains and N. We find that such a scaling approach enables a smooth, unified description of h in very good solvents over the full range of anchoring density and chain lengths, although this type of data reduction does not apply to marginal solvent quality conditions.

  3. Influence of chain topology on polymer crystallization: poly(ethylene oxide) (PEO) rings vs. linear chains.

    PubMed

    Zardalidis, George; Mars, Julian; Allgaier, Jürgen; Mezger, Markus; Richter, Dieter; Floudas, George

    2016-10-04

    The absence of entanglements, the more compact structure and the faster diffusion in melts of cyclic poly(ethylene oxide) (PEO) chains have consequences on their crystallization behavior at the lamellar and spherulitic length scales. Rings with molecular weight below the entanglement molecular weight (M < Me), attain the equilibrium configuration composed from twice-folded chains with a lamellar periodicity that is half of the corresponding linear chains. Rings with M > Me undergo distinct step-like conformational changes to a crystalline lamellar with the equilibrium configuration. Rings melt from this configuration in the absence of crystal thickening in sharp contrast to linear chains. In general, rings more easily attain their extended equilibrium configuration due to strained segments and the absence of entanglements. In addition, rings have a higher equilibrium melting temperature. At the level of the spherulitic superstructure, growth rates are much faster for rings reflecting the faster diffusion and more compact structure. With respect to the segmental dynamics in their semi-crystalline state, ring PEOs with a steepness index of ∼34 form some of the "strongest" glasses.

  4. Oligomer-to-polymer transition in short ethylene glycol chains connected to mobile hydrophobic anchors.

    PubMed

    Tanaka, Motomu; Rehfeldt, Florian; Schneider, Matthias F; Gege, Christian; Schmidt, Richard R; Funari, Sérgio S

    2005-01-01

    We studied the structure of short ethylene glycol (EG) chains with N repeating units (EGN, N = 3, 6, 9, 12, and 15) connected to hydrophobic dihexadecyl chains by means of a combination of differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). These synthetic amphiphiles dispersed in water form planar lamellar stacks and hexagonal cylinders confining the EG chains to restricted geometries. Owing to the self-assembly of the anchoring points, the lateral density of EG chains in planar lamella can be quantitatively controlled. Furthermore, the chain-melting phase transition of the anchors enables us to "switch" the intermolecular distance reversibly. SAXS/WAXS results suggest that the shorter EG chains (N = 3, 6, and 9) assume a helical conformation in stacks of planar lamella. When the EG chains are further elongated (N = 12 and 15), the lamellar periodicities cannot be explained by a linear extrapolation of shorter oligomers, but can be interpreted well as polymer brushes following the scaling theorem. Such rich phase behaviors of EGN molecules can be used as a simple model of oligo/poly-saccharide chains on cell surfaces, which act not only as flexible repellers between neighboring cells but also as stable spacers for functional ligands.

  5. Interaction of Nano-Sized Materials With Polymer Chains in Polymer-Nanocomposite Thin Films-An AFM Perspective

    NASA Astrophysics Data System (ADS)

    Verma, Gaurav; Kaushik, Anupama; Ghosh, Anup K.

    2011-12-01

    Nanocomposite thin films were prepared with polyurethane as a matrix and organically modified clay as a filler. The interfacial interaction between the exfoliated clay nanoplatelets and the polymeric chains has been investigated by using Atomic Force Microscopy (AFM). The nanoclay platelets show a preferential association with the hard domains of polyurethane matrix on the surface of the thin films. The pendant hydroxyl group on the nanoplatelets attract the isocyanate of the polyisocyanate and a urethane group is formed. This leads to the `clouding' and `entwining' of the nanoplatelets by the hard segmental chains. This is the first visual evidence of nanomaterial filler and polymer matrix interaction and it could open up a spectrum of novel property achievements in nanocomposite thin films. Also the understanding of this interaction can lead to more controlled architecture of nanocomposites.

  6. Effect of cation type, alkyl chain length, adsorbate size on adsorption kinetics and isotherms of bromide ionic liquids from aqueous solutions onto microporous fabric and granulated activated carbons.

    PubMed

    Hassan, Safia; Duclaux, Laurent; Lévêque, Jean-Marc; Reinert, Laurence; Farooq, Amjad; Yasin, Tariq

    2014-11-01

    The adsorption from aqueous solution of imidazolium, pyrrolidinium and pyridinium based bromide ionic liquids (ILs) having different alkyl chain lengths was investigated on two types of microporous activated carbons: a fabric and a granulated one, well characterized in terms of surface chemistry by "Boehm" titrations and pH of point of zero charge measurements and of porosity by N2 adsorption at 77 K and CO2 adsorption at 273 K. The influence of cation type, alkyl chain length and adsorbate size on the adsorption properties was analyzed by studying kinetics and isotherms of eight different ILs using conductivity measurements. Equilibrium studies were carried out at different temperatures in the range [25-55 °C]. The incorporation of ILs on the AC porosity was studied by N2 adsorption-desorption measurements at 77 K. The experimental adsorption isotherms data showed a good correlation with the Langmuir model. Thermodynamic studies indicated that the adsorption of ILs onto activated carbons was an exothermic process, and that the removal efficiency increased with increase in alkyl chain length, due to the increase in hydrophobicity of long chain ILs cations determined with the evolution of the calculated octanol-water constant (Kow). The negative values of free energies indicated that adsorption of ILs with long chain lengths having hydrophobic cations was more spontaneous at the investigated temperatures.

  7. Stretching semiflexible polymer chains: Evidence for the importance of excluded volume effects from Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping; Binder, Kurt

    2012-01-01

    Semiflexible macromolecules in dilute solution under very good solvent conditions are modeled by self-avoiding walks on the simple cubic lattice (d = 3 dimensions) and square lattice (d = 2 dimensions), varying chain stiffness by an energy penalty ɛb for chain bending. In the absence of excluded volume interactions, the persistence length ℓp of the polymers would then simply be ℓ _p=ℓ _b(2d-2)^{-1}q_b^{-1} with qb = exp (-ɛb/kBT), the bond length ℓb being the lattice spacing, and kBT is the thermal energy. Using Monte Carlo simulations applying the pruned-enriched Rosenbluth method (PERM), both qb and the chain length N are varied over a wide range (0.005 ⩽ qb ⩽ 1, N ⩽ 50 000), and also a stretching force f is applied to one chain end (fixing the other end at the origin). In the absence of this force, in d = 2 a single crossover from rod-like behavior (for contour lengths less than ℓp) to swollen coils occurs, invalidating the Kratky-Porod model, while in d = 3 a double crossover occurs, from rods to Gaussian coils (as implied by the Kratky-Porod model) and then to coils that are swollen due to the excluded volume interaction. If the stretching force is applied, excluded volume interactions matter for the force versus extension relation irrespective of chain stiffness in d = 2, while theories based on the Kratky-Porod model are found to work in d = 3 for stiff chains in an intermediate regime of chain extensions. While for qb ≪ 1 in this model a persistence length can be estimated from the initial decay of bond-orientational correlations, it is argued that this is not possible for more complex wormlike chains (e.g., bottle-brush polymers). Consequences for the proper interpretation of experiments are briefly discussed.

  8. Consistent model reduction of polymer chains in solution in dissipative particle dynamics: Model description

    NASA Astrophysics Data System (ADS)

    Moreno, Nicolas; Nunes, Suzana P.; Calo, Victor M.

    2015-11-01

    We introduce a framework for model reduction of polymer chain models for dissipative particle dynamics (DPD) simulations, where the properties governing the phase equilibria such as the characteristic size of the chain, compressibility, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required in traditional DPD representations to model equilibrium properties of systems with complex molecules (e.g., linear polymers). Based on geometrical considerations we explicitly account for the correlation between beads in fine-grained DPD models and consistently represent the effect of these correlations in a reduced model, in a practical and simple fashion via power laws and the consistent scaling of the simulation parameters. In order to satisfy the geometrical constraints in the reduced model we introduce bond-angle potentials that account for the changes in the chain free energy after the model reduction. Following this coarse-graining process we represent high molecular weight DPD chains (i.e., ≥ 200 beads per chain) with a significant reduction in the number of particles required (i.e., ≥ 20 times the original system). We show that our methodology has potential applications modeling systems of high molecular weight molecules at large scales, such as diblock copolymer and DNA.

  9. Chain conformations dictate multiscale charge transport phenomena in disordered semiconducting polymers.

    PubMed

    Noriega, Rodrigo; Salleo, Alberto; Spakowitz, Andrew J

    2013-10-08

    Existing models for the electronic properties of conjugated polymers do not capture the spatial arrangement of the disordered macromolecular chains over which charge transport occurs. Here, we present an analytical and computational description in which the morphology of individual polymer chains is dictated by well-known statistical models and the electronic coupling between units is determined using Marcus theory. The multiscale transport of charges in these materials (high mobility at short length scales, low mobility at long length scales) is naturally described with our framework. Additionally, the dependence of mobility with electric field and temperature is explained in terms of conformational variability and spatial correlation. Our model offers a predictive approach to connecting processing conditions with transport behavior.

  10. Conformation and elasticity of a charged polymer chain bridging two nanoparticles

    SciTech Connect

    Nowicki, W. Nowicka, G.

    2013-12-07

    A complex composed of a charged flexible polymer chain irreversibly attached with its ends to surfaces of two nanoparticles was investigated using the Metropolis Monte Carlo method on a simple cubic lattice. The simulations were performed in the presence of explicit ions. The bridging chain and the nanoparticles bearing the same and the opposite sign charges were considered. Changes in the free energy of the complex upon its stretching or compression, together with the magnitude of the elastic force, were examined. The relative roles of energetic and entropic effects in determining the properties of the complex were identified. Also, the adsorption of charged monomers on the opposite-sign charged nanoparticles and its influence on the examined quantities was studied. Moreover, a simple semi-analytical approach to the thermodynamics of the polymer bridge was derived.

  11. Solvation Energy of Ions in Polymers: Effects of Chain Length and Connectivity on Saturated Dipoles near Ions.

    PubMed

    Liu, Lijun; Nakamura, Issei

    2017-04-03

    We illustrate the effects of chain connectivity on the solvation energy of ions immersed in polymer liquids by developing a new coarse-grained molecular dynamics simulation. Our theory accounts for the dielectric response of the polymers through the connection of dipolar, monomeric units with nonlinear springs. In stark contrast to the standard Born solvation energy of ions, our results depend substantially on the chain length of the polymers. We also demonstrate the marked difference in the solvation energies of the ions immersed in non-polymeric particle mixtures, single-component polymers, polymer blends, and block copolymers. Thus, we suggest that the chain architecture of polymers is a key factor in ion solvation, whereas this feature is often inadequately considered in main theory and simulation literature. Our results are consistent with those predicted by previous coarse-grained mean-field theories when the dipole moment of the polymer compositions is relatively small. However, we also demonstrate that the strong ion-dipole and dipole-dipole interactions cause the chain-like association of the monomeric units, resulting in a qualitative discrepancy between the mean-field theory and simulation. Such a strong electrostatic correlation may reverse the dependence of the chain length on the solvation energy of the ions in the polymers.

  12. Inducing Planar Orientation in Side‐Chain Liquid‐Crystalline Polymer Systems via Interfacial Control

    PubMed Central

    2016-01-01

    Abstract For efficient photoresponses of liquid‐crystal (LC) azobenzene (Az) polymer systems, planar LC orientation of the Az mesogenic group is required because the light irradiation process usually occurs with normal incidence to the film surface. However, LC molecules with a rodlike shape tend to orient perpendicularly to the film surface according to the excluded volume effect theory. This review introduces new approaches for inducing planar orientation in side‐chain LC Az polymer films via interface and surface molecular designs. The planar orientation offers efficient in‐plane photoalignment and photoswitching to hierarchical LC architectures from molecular LC mesogens and LC phases to mesoscopic microphase‐separated structures. These approaches are expected to provide new concepts and possibilities in new LC polymer devices. PMID:26775770

  13. Resolving the mystery of the chain friction mechanism in polymer liquids.

    PubMed

    Sokolov, Alexei P; Schweizer, Kenneth S

    2009-06-19

    We propose an explanation for the long-standing puzzles of the microscopic mechanism of chain friction and the failure of time-temperature superposition in polymer melts based on decoupling of macromolecular scale diffusion from local structural relaxation due to spatially heterogeneous dynamics. The proposed physical picture is also relevant for understanding some aspects of dynamic fluctuation and decoupling phenomena in nonpolymeric glass-forming liquids, crystal growth rates, and protein activity in viscous solvents.

  14. The effect of chain bending on the photophysical properties of conjugated polymers.

    PubMed

    Hestand, Nicholas J; Spano, Frank C

    2014-07-17

    The impact of chain bending on the photophysical properties of emissive conjugated polymers (CPs) is studied theoretically using Holstein-style Hamiltonians which treat vibronic coupling involving the ubiquitous vinyl/ring stretching mode nonadiabatically. The photophysical impact of chain bending is already evident at the level of an effective Frenkel Hamiltonian, where the positive exciton band curvature in CPs translates to negative excitonic coupling between monomeric units, as in J-aggregates. It is shown that the absorption and photoluminescence (PL) spectral line shapes respond very differently to chain bending. The misalignment of monomeric transition dipole moments with bending selectively attenuates the 0-0 PL peak intensity while leaving the 0-1 intensity practically unchanged, a property which is ultimately due to the uniquely coherent nature of the 0-0 peak. Hence, the 0-0/0-1 PL ratio, as well as the radiative decay rate, decrease with chain bending, effects that are more pronounced at lower temperatures where exciton coherence extends over a larger portion of the chain. Increasing temperature and/or static disorder reduces the exciton coherence number, Ncoh, thereby reducing the sensitivity to bending. In marked contrast, the absorption vibronic progression is far less sensitive to morphological changes, even at low temperatures, and is mainly responsive to the exciton bandwidth. The above results also hold when using a more accurate 1D semiconductor Hamiltonian which allows for electron-hole separation along the CP chain. The findings may suggest unique ways of controlling the radiative properties of conjugated polymer chains useful in applications such as organic light emitting diodes (OLEDs) and low-temperature sensors.

  15. Adsorbed poly(ethyleneoxide)-poly(propyleneoxide) copolymers on synthetic surfaces: spectroscopy and microscopy of polymer structures and effects on adhesion of skin-borne bacteria.

    PubMed

    Marsh, Lorraine H; Coke, Mark; Dettmar, Peter W; Ewen, Richard J; Havler, Michael; Nevell, Thomas G; Smart, John D; Smith, James R; Timmins, Barry; Tsibouklis, John; Alexander, Cameron

    2002-09-15

    Poly(ethyleneoxide)-copoly(propyleneoxide) (PEO-PPO) polymer coatings were evaluated for their resistance to the attachment of the marker organism Serratia marcescens and the skin-borne bacteria Staphylococcus epidermidis. The copolymers were adsorbed onto poly(styrene) films-chosen as simplified physicochemical models of skin surfaces-and their surface characteristics probed by contact angle goniometry, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). These functional surfaces were then presented to microbial cultures, bacterial attachment was assessed by fluorescence microscopy and AFM, and the structures of the polymer films examined again spectroscopically. Surface characterization data suggest that the adsorbed copolymer was partially retained at the surface and resisted bacterial attachment for 24 h. Quantitative evaluation of cell attachment was carried out by scintillation counting of (14)C-labeled microorganisms in conjunction with plate counts. The results show that a densely packed layer of PEO-PPO copolymer can reduce attachment of skin commensals by an order of magnitude, even when the coating is applied by a simple adsorptive process. The work supports the hypothesis that adhesion of microorganisms to biological substrates can be reduced if a pretreatment with an appropriate copolymer can be effected in vivo.

  16. Amino-functionalized alkaline clay with cationic star-shaped polymer as adsorbents for removal of Cr(VI) in aqueous solution

    NASA Astrophysics Data System (ADS)

    Pan, Yuanfeng; Cai, Pingxiong; Farmahini-Farahani, Madjid; Li, Yiduo; Hou, Xiaobang; Xiao, Huining

    2016-11-01

    Pentaerythritol (PER) was esterified with 2-bromoisobutyryl bromide to synthesize a four-arm initiator 4Br-PER for atom transfer radical polymerization (ATRP). Star-shaped copolymers (P(AM-co-DMAEMA)4, CSP) were prepared via ATRP using dimethyl aminoethyl methacrylate (DMAEMA) and acrylamide (AM) as comonomers, while Br-PER and CuBr/2,2‧-bipyridine (BPY) as the initiator and the catalyst, respectively. The resulting four-arm initiator and star-shaped polymer (CSP) were characterized with FT-IR, 1H NMR and Ubbelohde viscometry. Alkaline clay (AC) was immobilized with CSPs to yield amino groups, and the cationic star polymer-immobilized alkaline clay (CSP-AC) was applied to remove Cr(VI) from the aqueous solution in batch experiments. Various influencing factors, including pH, contact time and immobilization amount of CSP on adsorption capacity of CSP-AC for Cr(VI) were also investigated. The results demonstrated that Cr(VI) adsorption was highly pH dependent. The optimized pH value was 4.0. The adsorption isotherms of the adsorbent fit the Langmuir model well, with the maximum adsorption capacity of 137.9 mg/g at 30 °C. The material should be a promising adsorbent for Cr(VI) removal, with the advantages of high adsorption capacity.

  17. Folding mechanism of a polymer chain with short-range attractions

    NASA Astrophysics Data System (ADS)

    Leitold, Christian; Dellago, Christoph

    2014-10-01

    We investigate the crystallization of a single, flexible homopolymer chain using transition path sampling. The chain consists of N identical spherical monomers evolved according to Langevin dynamics. While neighboring monomers are coupled via harmonic springs, the non-neighboring monomers interact via a hard core and a short-ranged attractive potential. For a sufficiently small interaction range λ, the system undergoes a first-order freezing transition from an expanded, disordered phase to a compact crystalline state. Using a new shooting move tailored to polymers combined with a committor analysis, we study the transition state ensemble of an N = 128 chain and search for possible reaction coordinates based on likelihood maximization. We find that typical transition states consist of a crystalline nucleus with one or more chain fragments attached to it. Furthermore, we show that the number of particles in the crystalline core is not well suited as a reaction coordinate. We then present an improved reaction coordinate, which includes information from the potential energy and the overall crystallinity of the polymer.

  18. Combining Diffusion NMR and Small-Angle Neutron Scattering Enables Precise Measurements of Polymer Chain Compression in a Crowded Environment

    NASA Astrophysics Data System (ADS)

    Palit, Swomitra; He, Lilin; Hamilton, William A.; Yethiraj, Arun; Yethiraj, Anand

    2017-03-01

    The effect of particles on the behavior of polymers in solution is important in a number of important phenomena such as the effect of "crowding" proteins in cells, colloid-polymer mixtures, and nanoparticle "fillers" in polymer solutions and melts. In this Letter, we study the effect of spherical inert nanoparticles (which we refer to as "crowders") on the diffusion coefficient and radius of gyration of polymers in solution using pulsed-field-gradient NMR and small-angle neutron scattering (SANS), respectively. The diffusion coefficients exhibit a plateau below a characteristic polymer concentration, which we identify as the overlap threshold concentration c⋆. Above c⋆, in a crossover region between the dilute and semidilute regimes, the (long-time) self-diffusion coefficients are found, universally, to decrease exponentially with polymer concentration at all crowder packing fractions, consistent with a structural basis for the long-time dynamics. The radius of gyration obtained from SANS in the crossover regime changes linearly with an increase in polymer concentration, and must be extrapolated to c⋆ in order to obtain the radius of gyration of an individual polymer chain. When the polymer radius of gyration and crowder size are comparable, the polymer size is very weakly affected by the presence of crowders, consistent with recent computer simulations. There is significant chain compression, however, when the crowder size is much smaller than the polymer radius gyration.

  19. Combining Diffusion NMR and Small-Angle Neutron Scattering Enables Precise Measurements of Polymer Chain Compression in a Crowded Environment.

    PubMed

    Palit, Swomitra; He, Lilin; Hamilton, William A; Yethiraj, Arun; Yethiraj, Anand

    2017-03-03

    The effect of particles on the behavior of polymers in solution is important in a number of important phenomena such as the effect of "crowding" proteins in cells, colloid-polymer mixtures, and nanoparticle "fillers" in polymer solutions and melts. In this Letter, we study the effect of spherical inert nanoparticles (which we refer to as "crowders") on the diffusion coefficient and radius of gyration of polymers in solution using pulsed-field-gradient NMR and small-angle neutron scattering (SANS), respectively. The diffusion coefficients exhibit a plateau below a characteristic polymer concentration, which we identify as the overlap threshold concentration c^{⋆}. Above c^{⋆}, in a crossover region between the dilute and semidilute regimes, the (long-time) self-diffusion coefficients are found, universally, to decrease exponentially with polymer concentration at all crowder packing fractions, consistent with a structural basis for the long-time dynamics. The radius of gyration obtained from SANS in the crossover regime changes linearly with an increase in polymer concentration, and must be extrapolated to c^{⋆} in order to obtain the radius of gyration of an individual polymer chain. When the polymer radius of gyration and crowder size are comparable, the polymer size is very weakly affected by the presence of crowders, consistent with recent computer simulations. There is significant chain compression, however, when the crowder size is much smaller than the polymer radius gyration.

  20. Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

    PubMed Central

    Nakatani, Hisayuki; Kurniawan, Dodik; Taniike, Toshiaki; Terano, Minoru

    2008-01-01

    In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction. PMID:27877968

  1. Statistical model of a flexible inextensible polymer chain: The effect of kinetic energy

    NASA Astrophysics Data System (ADS)

    Pergamenshchik, V. M.; Vozniak, A. B.

    2017-01-01

    Because of the holonomic constraints, the kinetic energy contribution in the partition function of an inextensible polymer chain is difficult to find, and it has been systematically ignored. We present the first thermodynamic calculation incorporating the kinetic energy of an inextensible polymer chain with the bending energy. To explore the effect of the translation-rotation degrees of freedom, we propose and solve a statistical model of a fully flexible chain of N +1 linked beads which, in the limit of smooth bending, is equivalent to the well-known wormlike chain model. The partition function with the kinetic and bending energies and correlations between orientations of any pair of links and velocities of any pair of beads are found. This solution is precise in the limits of small and large rigidity-to-temperature ratio b /T . The last exact solution is essential as even very "harmless" approximation results in loss of the important effects when the chain is very rigid. For very high b /T , the orientations of different links become fully correlated. Nevertheless, the chain does not go over into a hard rod even in the limit b /T →∞ : While the velocity correlation length diverges, the correlations themselves remain weak and tend to the value ∝T /(N +1 ). The N dependence of the partition function is essentially determined by the kinetic energy contribution. We demonstrate that to obtain the correct energy and entropy in a constrained system, the T derivative of the partition function has to be applied before integration over the constraint-setting variable.

  2. Statistical model of a flexible inextensible polymer chain: The effect of kinetic energy.

    PubMed

    Pergamenshchik, V M; Vozniak, A B

    2017-01-01

    Because of the holonomic constraints, the kinetic energy contribution in the partition function of an inextensible polymer chain is difficult to find, and it has been systematically ignored. We present the first thermodynamic calculation incorporating the kinetic energy of an inextensible polymer chain with the bending energy. To explore the effect of the translation-rotation degrees of freedom, we propose and solve a statistical model of a fully flexible chain of N+1 linked beads which, in the limit of smooth bending, is equivalent to the well-known wormlike chain model. The partition function with the kinetic and bending energies and correlations between orientations of any pair of links and velocities of any pair of beads are found. This solution is precise in the limits of small and large rigidity-to-temperature ratio b/T. The last exact solution is essential as even very "harmless" approximation results in loss of the important effects when the chain is very rigid. For very high b/T, the orientations of different links become fully correlated. Nevertheless, the chain does not go over into a hard rod even in the limit b/T→∞: While the velocity correlation length diverges, the correlations themselves remain weak and tend to the value ∝T/(N+1). The N dependence of the partition function is essentially determined by the kinetic energy contribution. We demonstrate that to obtain the correct energy and entropy in a constrained system, the T derivative of the partition function has to be applied before integration over the constraint-setting variable.

  3. The chain sucker: Translocation dynamics of a polymer chain into a long narrow channel driven by longitudinal flow

    NASA Astrophysics Data System (ADS)

    Luo, Kaifu; Metzler, Ralf

    2011-04-01

    Using analytical techniques and Langevin dynamics simulations, we investigate the dynamics of polymer translocation into a narrow channel of width R embedded in two dimensions, driven by a force proportional to the number of monomers in the channel. Such a setup mimics typical experimental situations in nano/microfluidics. During the translocation process if the monomers in the channel can sufficiently quickly assume steady state motion, we observe the scaling τ ˜ N/F of the translocation time τ with the driving force F per bead and the number N of monomers per chain. With smaller channel width R, steady state motion cannot be achieved, effecting a nonuniversal dependence of τ on N and F. From the simulations we also deduce the waiting time distributions under various conditions for the single segment passage through the channel entrance. For different chain lengths but the same driving force, the curves of the waiting time as a function of the translocation coordinate s feature a maximum located at identical smax, while with increasing the driving force or the channel width the value of smax decreases.

  4. Memory effect in the chain-collapse process in a dilute polymer solution

    NASA Astrophysics Data System (ADS)

    Maki, Yasuyuki; Sasaki, Naoki; Nakata, Mitsuo

    2004-12-01

    The effect of temperature perturbation on a single-chain-collapse process was studied for poly(methyl methacrylate) with the molecular weight Mw=1.05×107 in the mixed solvent of tert-butyl alcohol+water (2.5 vol %). In the chain-collapse process after a quench from the θ temperature to a temperature T1, the temperature was changed from T1 to T2 at the time t1 after the quench and returned to T1 at the time t1+t2. In the three stages at T1, T2, and T1, measurements of the mean-square radius of gyration of polymer chains were carried out by static light scattering and the chain-collapse process was represented by the expansion factor as a function of time. An effect of chain aggregation on the measurements was negligibly small because of the very slow phase separation. For the negative temperature perturbation (T1>T2), the chain-collapse processes observed in the first and third stages were connected smoothly and agreed with the collapse process due to a single-stage quench to T1. A memory of the chain collapse in the first stage at T1 was found to persist into the third stage at the same temperature T1 without being affected by the temperature perturbation of T2 during t2. The memory effect was observed irrespective of the time period of t2. The positive temperature perturbation (T1chain-collapse process.

  5. Effect of polymer chain length on membrane perturbation activity of cationic phenylene ethynylene oligomers and polymers.

    PubMed

    Wang, Ying; Jones, Emmalee M; Tang, Yanli; Ji, Eunkyung; Lopez, Gabriel P; Chi, Eva Y; Schanze, Kirk S; Whitten, David G

    2011-09-06

    The interactions of poly(phenylene ethynylene)- (PPE-) based cationic conjugated polyelectrolytes (CPEs) and oligo(phenylene ethynylene)s (OPEs) with different model lipid membrane systems were investigated to gain insight into the relationship between molecular structure and membrane perturbation ability. The CPE and OPE compounds exhibit broad-spectrum antimicrobial activity, and cell walls and membranes are believed to be their main targets. To better understand how the size, in terms of the number of repeat units, of the CPEs and OPEs affects their membrane disruption activities, a series of PPE-based CPEs and OPEs were synthesized and studied. A number of photophysical techniques were used to investigate the interactions of CPEs and OPEs with model membranes, including unilamellar vesicles and lipid monolayers at the air/water interface. CPE- or OPE-induced dye leakage from vesicles reveals that the CPEs and OPEs selectively perturb model bacterial membranes and that their membrane perturbation abilities are highly dependent on molecular size. Consistent with dye-leakage assay results, the CPEs and OPEs also exhibit chain-length-dependent ability to insert into 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) monolayers. Our results suggest that, for PPE-based CPE and OPE antimicrobials, chain length can be tuned to optimize their membrane perturbation ability.

  6. Optical Nanofluidic Piston: Assay for Dynamic Force-Compression of Single Confined Polymer Chains

    NASA Astrophysics Data System (ADS)

    Khorshid, Ahmed; Zimny, Philip; Macos, Patrick; Massarelli, Geremia; Tétreault-La Roche, David; Reisner, Walter

    2014-03-01

    While single-molecule approaches now have a long-history in polymer physics, past methodology has a key limitation : it is not currently possible to apply well-defined forces to a precise number of chains in a well-defined volume. To this end,we have developed a nanofluidic assay for the study of DNA compression in vitro, the optical nanofluidic piston. The optical nanofluidic piston is a nanofluidic analog of a macroscopic piston-cylinder apparatus based on a nanosphere (``the piston'') optically trapped inside a 200-400nm nanochannel with embedded barrier (the ``cylinder''). The nanofluidic piston enables quantification of force required to compress single or multiple chains within a defined volume. We present combined fluorescence and force-measurements for the compression of T4 DNA under a variety of compression rates. Surprisingly, we find that compression occurs on a force-scale roughly 100x higher than that predicted by equilibrium theories, suggesting that the DNA is present in highly entangled states during the compression. Moreover, we observe that compression at high rates induces a ``shock-wave'' of high-polymer concentration near the bead, suggesting that our setup can quantitatively access novel non-equilibrium polymer phenomena.

  7. Comparative study of polymer chain dynamics in aqueous solutions by FPR and DLS

    NASA Astrophysics Data System (ADS)

    Streletzky, Kiril; McDonough, Ryan; Cueto, Rafael; Russo, Paul

    2012-02-01

    Self diffusion of tagged polymer chains in aqueous solutions of hydroxypropylcellulose (HPC) was measured by Fluorescence Photo-bleaching Recovery (FPR) and compared to mutual diffusion of scattering species in the same solutions measured by Dynamic Light Scattering (DLS). The effect of the dye presence on thermodynamic concentration fluctuations observed by DLS was also studied. The observed multimodal spectra in DLS and FPR were analyzed with CONTIN and stretched exponential fits. A set of consistent dissimilarities in the modal distributions of FPR and DLS spectra was found. This indicates a comparative limitation or sensitivity in range of detectable diffusive processes between FPR and DLS in this complex system. In addition, it was found that the fluorescent tag and/or tagging process seem to alter the mutual diffusion processes seen by DLS. In particular, a slower mode which is apparent in the non-tagged sample does not appear in the tagged sample. It seems likely that the dye chemically affects the polymer chains keeping them from clustering with each other, altering the solvent environment preventing formation of polymer clusters responsible for the slow mode usually seen in HPC.

  8. Fast convergence to equilibrium for long-chain polymer melts using a MD/continuum hybrid method.

    PubMed

    Senda, Yasuhiro; Fujio, Miyuki; Shimamura, Shuji; Blomqvist, Janne; Nieminen, Risto M

    2012-10-21

    Effective and fast convergence toward an equilibrium state for long-chain polymer melts is realized by a hybrid method coupling molecular dynamics and the elastic continuum. The required simulation time to achieve the equilibrium state is reduced compared with conventional equilibration methods. The polymers move on a wide range phase space due to large-scale fluctuation generated by the elastic continuum. A variety of chain structures is generated in the polymer melt which results in the fast convergence to the equilibrium state.

  9. Dynamics of particle chain formation in a liquid polymer under ac electric field: modeling and experiments

    NASA Astrophysics Data System (ADS)

    Belijar, G.; Valdez-Nava, Z.; Diaham, S.; Laudebat, L.; Jones, T. B.; Lebey, T.

    2017-01-01

    Polymer/ceramic composite materials are of great interest for their many potential applications because of their ability to combine at least two properties of the constitutive elements: particles and matrix. In most cases, such enhanced properties are required only in one direction. Orthotropic materials can be elaborated by applying an ac electric field to form particle chain structures in the direction of the electric field due to the dielectrophoretic interactions affecting the particles. However, there is still a lack in the understanding of the impact of the structures on the properties of the material. The aim of this study is to propose a predictive model for the evolution of the permittivity during the chain formation, by including micro- and macroscopic phenomena. The chaining model is based on dipole-dipole interactions and the dielectric permittivity is computed through a finite element method. In parallel, an experimental study is performed with online permittivity measurements of composites during chaining. The developed model is able to predict the experimental results from 1 vol% while taking into account parameters such as the resin viscosity and permittivity and the transient evolution of the applied electric field. The formation of particle chains inside a material has applications in many domains such as electrorheological fluids, anisotropic composites, self-recovery materials etc. Such a developed model is a valuable tool for the tailoring of materials.

  10. Effect of polymer rigidity on the phase behaviour of polymer adsorption on to planar surface

    PubMed Central

    Yang, Zhiyong; Chai, Aihua; Zhou, Peicong; Li, Ping; Yang, Yongfu

    2016-01-01

    We study the process of a semiflexible polymer chain adsorption on to planar surface by the dynamic Monte Carlo (DMC) method, based on the 3D off-lattice model. Both the strength of attractive monomer–surface interaction (εa) and bending energy (b) have pronounced effect on the adsorption and shape of semiflexible polymer chain. The semiflexible polymer can just fully adsorb on to the surface at certain εa, which is defined as critical εa. The essential features of the semiflexible polymer adsorption on to surface are that (i) the critical εa increases with increase in b; (ii) the shape of the fully adsorbed semiflexible polymer chain is film-like toroid, and the toroid becomes more and more perfect with increase in b. In addition, the size of toroid and the number of turns of toroid can be controlled by the b and εa. PMID:27756826

  11. Concentration fluctuations in miscible polymer blends: Influence of temperature and chain rigidity

    SciTech Connect

    Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.

    2014-05-21

    In contrast to binary mixtures of small molecule fluids, homogeneous polymer blends exhibit relatively large concentration fluctuations that can strongly affect the transport properties of these complex fluids over wide ranges of temperatures and compositions. The spatial scale and intensity of these compositional fluctuations are studied by applying Kirkwood-Buff theory to model blends of linear semiflexible polymer chains with upper critical solution temperatures. The requisite quantities for determining the Kirkwood-Buff integrals are generated from the lattice cluster theory for the thermodynamics of the blend and from the generalization of the random phase approximation to compressible polymer mixtures. We explore how the scale and intensity of composition fluctuations in binary blends vary with the reduced temperature τ ≡ (T − T{sub c})/T (where T{sub c} is the critical temperature) and with the asymmetry in the rigidities of the components. Knowledge of these variations is crucial for understanding the dynamics of materials fabricated from polymer blends, and evidence supporting these expectations is briefly discussed.

  12. Formation of Gd coordination polymer with 1D chains mediated by Bronsted acidic ionic liquids

    NASA Astrophysics Data System (ADS)

    Luo, Qianqian; Han, Ying; Lin, Hechun; Zhang, Yuanyuan; Duan, Chungang; Peng, Hui

    2017-03-01

    One dimensional coordination polymer Gd[(SO4)(NO3)(C2H6SO)2] (1) is prepared through the mediation of Bronsted acid ionic liquid, which crystallized in the monoclinic space of C2/c. In this polymer, adjacent Gd atoms are linked by two SO42- ions to generate a 1-D chain, and all oxygen atoms in SO42- groups are connected to three nearest Gd atoms in μ3:η1:η1:η2 fashion. Gd, S and N from SO42- and NO3- are precisely coplanar. The planar is coordinated by a pair of DMSO molecules, which is parallel and linked by hydrogen bonding to form a three-dimensional supramolecular network. Magnetic susceptibility measurement of 1 reveals weak antiferromagnetic interactions between the Gd (III) ions. It exhibits relatively large magneto-caloric effect with -ΔSm=28.8 J Kg-1 K-1 for ΔH=7 T.

  13. Polymer chain in a good solvent between attracting walls. A scaling approach

    NASA Astrophysics Data System (ADS)

    Allegra, Giuseppe; Colombo, Emanuele

    1996-09-01

    measurements of the force exerted by polymer chains on confining surfaces, obtained by Klein and co-workers, appear to be consistent with these theoretical results.

  14. Dehydrocoupling and Silazane Cleavage Routes to Organic-Inorganic Hybrid Polymers with NBN Units in the Main Chain.

    PubMed

    Lorenz, Thomas; Lik, Artur; Plamper, Felix A; Helten, Holger

    2016-06-13

    Despite the great potential of both π-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons in organic optoelectronics, our knowledge of conjugated polymers with B-N bonds in their main chain is currently scarce. Herein, the first examples of a new class of organic-inorganic hybrid polymers are presented, which consist of alternating NBN and para-phenylene units. Polycondensation with B-N bond formation provides facile access to soluble materials under mild conditions. The photophysical data for the polymer and molecular model systems of different chain lengths reveal a low extent of π-conjugation across the NBN units, which is supported by DFT calculations. The applicability of the new polymers as macromolecular polyligands is demonstrated by a cross-linking reaction with Zr(IV) .

  15. Impact of Fluorine Substituents on π-Conjugated Polymer Main-Chain Conformations, Packing, and Electronic Couplings.

    PubMed

    Do, Khanh; Saleem, Qasim; Ravva, Mahesh Kumar; Cruciani, Federico; Kan, Zhipeng; Wolf, Jannic; Hansen, Michael Ryan; Beaujuge, Pierre M; Brédas, Jean-Luc

    2016-10-01

    Taking the π-conjugated polymers PBDT[2X]T (X = H, F) as model systems, the effects of fluorine substitution on main-chain conformations, packing, and electronic couplings are examined. This combination of molecular dynamics simulations and solid-state NMR shows that a higher propensity for backbone planarity in PBDT[2F]T leads to more pronounced, yet staggered, chain stacking, which generally leads to higher electronic couplings and binding energy between neighboring chains.

  16. Two unprecedented 1D coordination polymer chains based on tetranuclear copper(II) building blocks

    SciTech Connect

    Li Gaijuan; Xing Yan Song Shuyan; Xu Ning; Liu Xianchun; Su Zhongmin

    2008-09-15

    The reaction of copper(II) sulfate with pyridine in DMF or methanol yield two unprecedented Cu(II) coordination polymers {l_brace}[Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}][{mu}-Cu(py)(DMF){sub 2}]{r_brace}{sub n}(1) and {l_brace}[Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}][{mu}-Cu(py){sub 4}]{r_brace}{sub n}(2), respectively. Single-crystal X-ray diffraction indicated that compound 1 crystallizes in the monoclinic system, space group p2(1)/n, a=14.542(5) A, b=16.359(5) A, c=18.951(5) A, {beta}=92.047(5){sup o}, V=4505(2) A{sup 3}, Z=4 while 2 is monoclinic C2/c, a=23.078(5) A, b=10.214(5) A, c=23.142(5) A, {beta}=115.471(5){sup o}, V=4925(3) A{sup 3}, Z=4. Both of the two compounds consist of tetrahedral tetranuclear [Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}] clusters that are bridged by pentacoordinated Cu atom for 1 or hexacoordinated Cu atoms for 2 through the sulfate oxygen to form the infinite one-dimensional polymer chains. - Graphical abstract: Two unprecedented Cu(II) coordination polymers have been prepared by using solvothermal method; they consist of tetrahedral tetranuclear clusters that are bridged by unique Cu(II) atom through the sulfate oxygen to form the infinite one-dimensional polymer chains (a) for complex 1 and (b) for complex 2.

  17. An atomic finite element model for biodegradable polymers. Part 2. A model for change in Young's modulus due to polymer chain scission.

    PubMed

    Gleadall, Andrew; Pan, Jingzhe; Kruft, Marc-Anton

    2015-11-01

    Atomic simulations were undertaken to analyse the effect of polymer chain scission on amorphous poly(lactide) during degradation. Many experimental studies have analysed mechanical properties degradation but relatively few computation studies have been conducted. Such studies are valuable for supporting the design of bioresorbable medical devices. Hence in this paper, an Effective Cavity Theory for the degradation of Young's modulus was developed. Atomic simulations indicated that a volume of reduced-stiffness polymer may exist around chain scissions. In the Effective Cavity Theory, each chain scission is considered to instantiate an effective cavity. Finite Element Analysis simulations were conducted to model the effect of the cavities on Young's modulus. Since polymer crystallinity affects mechanical properties, the effect of increases in crystallinity during degradation on Young's modulus is also considered. To demonstrate the ability of the Effective Cavity Theory, it was fitted to several sets of experimental data for Young's modulus in the literature.

  18. An all-optical poling investigation of low absorbing azobenzene side-chain polymer films

    NASA Astrophysics Data System (ADS)

    Jia, Yajie; Wang, Gongming; Guo, Bin; Su, Wei; Zhang, Qijin

    2004-09-01

    All optical poling (AOP) processes of both the typical AOP material disperse red 1 (DR1) copolymer and a low absorbing side-chain poly(2-[4-(4-cyanophenylazo)phenoxy] hexyl methacrylate), called PCN6, were examined and compared. The trade-off between the optical seeding efficiency and the transparency of the nonlinear polymer was considered. Quasi-phase matched (QPM) second harmonic generation (SHG) in PCN6 films was demonstrated. A relaxation retardation effect of the photo-induced khgr(2) was also observed in thick PCN6 films.

  19. Real polymer size from the ideal chain molecules model in a diffusive Minkowskian spacetime.

    PubMed

    Mezzasalma, Stefano A

    2006-07-15

    The universal exponent (nu(r)) of the real polymer size (i.e., the excluded volume chain) is derived from constraining the ideal coil model (nu(i) = 12) to a Minkowski-type diffusive spacetime. The square end-to-end distance was expanded in wavenumber power series, whence the leading contribution is extracted according to previously proposed Lorentz transforms acting in Brownian media. In the end, it turns out nu(i) approximately equal to nu(r) sin 1, in good agreement with predictions of the phase transition theory for critical phenomena.

  20. Design and synthesis of self-degradable antibacterial polymers by simultaneous chain- and step-growth radical copolymerization.

    PubMed

    Mizutani, Masato; Palermo, Edmund F; Thoma, Laura M; Satoh, Kotaro; Kamigaito, Masami; Kuroda, Kenichi

    2012-05-14

    Self-degradable antimicrobial copolymers bearing cationic side chains and main-chain ester linkages were synthesized using the simultaneous chain- and step-growth radical polymerization of t-butyl acrylate and 3-butenyl 2-chloropropionate, followed by the transformation of t-butyl groups into primary ammonium salts. We prepared a series of copolymers with different structural features in terms of molecular weight, monomer composition, amine functionality, and side chain structures to examine the effect of polymer properties on their antimicrobial and hemolytic activities. The acrylate copolymers containing primary amine side chains displayed moderate antimicrobial activity against E. coli but were relatively hemolytic. The acrylate copolymer with quaternary ammonium groups and the acrylamide copolymers showed low or no antimicrobial and hemolytic activities. An acrylate copolymer with primary amine side chains degraded to lower molecular weight oligomers with lower antimicrobial activity in aqueous solution. This degradation was due to amidation of the ester groups of the polymer chains by the nucleophilic addition of primary amine groups in the side chains resulting in cleavage of the polymer main chain. The degradation mechanism was studied in detail by model reactions between amine compounds and precursor copolymers.

  1. Specific Interactions of Neutral Side Chains of an Adsorbed Protein with the Surface of α-Quartz and Silica Gel.

    PubMed

    Odinokov, Alexey V; Bagaturyants, Alexander A

    2015-07-16

    Many key features of the protein adsorption on the silica surfaces still remain unraveled. One of the open questions is the interaction of nonpolar side chains with siloxane cavities. Here, we use nonequilibrium molecular dynamics simulations for the detailed investigation of the binding of several hydrophobic and amphiphilic protein side chains with silica surface. These interactions were found to be a possible driving force for protein adsorption. The free energy gain was larger for the disordered surface of amorphous silica gel as compared to α-quartz, but the impact depended on the type of amino acid. The dependence was analyzed from the structural point of view. For every amino acid an enthalpy-entropy compensation behavior was observed. These results confirm a hypothesis of an essential role of hydrophobic interactions in protein unfolding and irreversible adsorption on the silica surface.

  2. Revealing the Supramolecular Nature of Side-Chain Terpyridine-Functionalized Polymer Networks

    PubMed Central

    Brassinne, Jérémy; Jochum, Florian D.; Fustin, Charles-André; Gohy, Jean-François

    2015-01-01

    Nowadays, finely controlling the mechanical properties of polymeric materials is possible by incorporating supramolecular motifs into their architecture. In this context, the synthesis of a side-chain terpyridine-functionalized poly(2-(dimethylamino)ethyl methacrylate) is reported via reversible addition-fragmentation chain transfer polymerization. By addition of transition metal ions, concentrated aqueous solutions of this polymer turn into metallo-supramolecular hydrogels whose dynamic mechanical properties are investigated by rotational rheometry. Hence, the possibility for the material to relax mechanical constrains via dissociation of transient cross-links is brought into light. In addition, the complex phenomena occurring under large oscillatory shear are interpreted in the context of transient networks. PMID:25569082

  3. A novel coordination polymer containing both interdigitated 1D chains and interpenetrated 2D grids.

    PubMed

    Ayyappan, Ponnaiyan; Evans, Owen R; Lin, Wenbin

    2002-07-01

    A hydro(solvo)thermal reaction between zinc perchlorate and ethyl ester of a new pyridinecarboxylate bridging ligand of approximately 17.6 A in length yields a unique coordination polymer which contains both interdigitated infinite 1D chains and interpenetrated 2D rhombohedral grids [Zn(2.5)(L)(4)(mu(3)-OH)] x (H(2)O)(5), 1, where L is 3-[[4-(4-pyridylethenyl)phenyl]ethenyl]benzoate. The 1D chains contain mu(3)-bridged hydroxy groups and have a [Zn(4)(mu(3)-OH)(2)(L)(6)] stoichiometry, while the 2D grids have a Zn(L)(2) formula and diagonal distances of 31.7 and 25.2 A. Crystal data for 1: monoclinic space group P2/c, a = 15.686(2) A, b = 12.6103(16) A, c = 38.999(5) A, beta = 98.397(2) degrees, and Z = 4.

  4. Phthalocyaninato complexes with peripheral alkylthio chains: disk-like adsorbate species for the vertical anchoring of ligands on gold surfaces

    PubMed Central

    Siemeling, Ulrich; Schirrmacher, Christian; Glebe, Ulrich; Bruhn, Clemens; Baio, Joe E.; Árnadóttir, Líney; Castner, David G.; Weidner, Tobias

    2011-01-01

    Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalised phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, β-positioned, alkylthio substituents SR (1a: R = n-C8H17, 1b: R = n-C12H25), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterised by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether–gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII. PMID:21857743

  5. New theoretical considerations in polymer rheology: Elastic breakdown of chain entanglement network

    NASA Astrophysics Data System (ADS)

    Wang, Shi-Qing; Ravindranath, Sham; Wang, Yangyang; Boukany, Pouyan

    2007-08-01

    Recent experimental evidence has motivated us to present a set of new theoretical considerations and to provide a rationale for interpreting the intriguing flow phenomena observed in entangled polymer solutions and melts [P. Tapadia and S. Q. Wang, Phys. Rev. Lett. 96, 016001 (2006); 96, 196001 (2006); S. Q. Wang et al., ibid. 97, 187801 (2006)]. Three forces have been recognized to play important roles in controlling the response of a strained entanglement network. During flow, an intermolecular locking force fiml arises and causes conformational deformation in each load-bearing strand between entanglements. The chain deformation builds up a retractive force fretract within each strand. Chain entanglement prevails in quiescence because a given chain prefers to stay interpenetrating into other chains within its pervaded volume so as to enjoy maximum conformational entropy. Since each strand of length lent has entropy equal to kBT, the disentanglement criterion is given by fretract>fent~kBT/lent in the case of interrupted deformation. This condition identifies fent as a cohesive force. Imbalance among these forces causes elastic breakdown of the entanglement network. For example, an entangled polymer yields during continuous deformation when the declining fiml cannot sustain the elevated fretract. This opposite trend of the two forces is at the core of the physics governing a ``cohesive'' breakdown at the yield point (i.e., the stress overshoot) in startup flow. Identifying the yield point as the point of force imbalance, we can also rationalize the recently observed striking scaling behavior associated with the yield point in continuous deformation of both shear and extension.

  6. The role of polymer nanolayer architecture on the separation performance of anion-exchange membrane adsorbers: part II. DNA and virus separations.

    PubMed

    Bhut, Bharat V; Weaver, Justin; Carter, Andrew R; Wickramasinghe, S Ranil; Husson, Scott M

    2011-11-01

    The surface-initiated polymerization protocol developed in part I was used to prepare strong anion-exchange membranes with variable polymer chain graft densities and degrees of polymerization for DNA and virus particle separations. A focus of part II was to evaluate the role of polymer nanolayer architecture on DNA and virus binding. Salmon sperm-DNA (SS-DNA) was used as model nucleic acid to measure the dynamic-binding capacities at 10% breakthrough. The dynamic-binding capacity increases linearly with increasing poly ([2-(methacryloyloxy)ethyl]trimethylammonium chloride) chain density up to the highest chain density used in this study. The new membranes yielded threefold higher SS-DNA-binding capacity (30 mg/mL) than a leading commercial membrane with the same functional group chemistry. Elution of bound DNA yielded a sharp peak, and resulted in a 13-fold increase relative to the feed concentration. This concentration effect further demonstrates the highly favorable transport properties of the newly designed Q-type membranes. However, unlike findings in part I on protein binding, SS-DNA binding was not fully reversible. Minute virus of mice (MVM) was used as model virus to evaluate the virus clearance performance of newly designed Q-type membranes. Log reduction of virus (LRV) of MVM increased with increasing polymer chain density. Membranes exhibited >4.5 LRV for the given MVM impurity load and may be capable of higher LRV values, as the MVM concentration in the flow-through fraction of these samples was below the limit of detection of the assay.

  7. Generalized Statistical Mechanics and Scaling Behavior for Non-equilibrium Polymer Chains: II. Monomers Connected by Springs

    NASA Astrophysics Data System (ADS)

    Ma, Wen-Jong; Hu, Chin-Kun

    2010-02-01

    We use molecular dynamics simulations to study the relaxation process in a system of spatially well-mixed polymer chains and Lennard-Jones molecules, in which each polymer chain consists of monomers connected by springs of strength kspring and governed by bending and torsion angle potentials. The monomers are fluid-repelling, except for a small number of randomly chosen fluid-attractive “linker-sites”. The instantaneous temperatures of the monomers in polymer chains, T*P, and the fluid, T*F, are initially different, but they vary in time and their ratios Γ* = T*P/T*F approach a constant during the relaxation process. The velocity distributions of monomers in the relaxation process follow q-statistics with q ≥ 1. We find that the value of q and the limiting ratio of Γ* depend on kspring; in the strong strength limit, they approach those for the system, in which each polymer chain consists of monomers connected by rigid bonds; in the weak strength limit, Γ* and q approach 1 corresponding to Maxwell-Boltzmann distribution. The thermal contact between polymer chains and the fluid in our simulated systems provides a good basis for further study on the concept of temperature and the effective number of degrees of freedom in heterogeneous soft-matter systems.

  8. Polymer-grafted lignin surfactants prepared via reversible addition-fragmentation chain-transfer polymerization.

    PubMed

    Gupta, Chetali; Washburn, Newell R

    2014-08-12

    Kraft lignin grafted with hydrophilic polymers has been prepared using reversible addition-fragmentation chain-transfer (RAFT) polymerization and investigated for use as a surfactant. In this preliminary study, polyacrylamide and poly(acrylic acid) were grafted from a lignin RAFT macroinitiator at average initiator site densities estimated to be 2 per particle and 17 per particle. The target degrees of polymerization were 50 and 100, but analysis of cleaved polyacrylamide was consistent with a higher average molecular weight, suggesting not all sites were able to participate in the polymerization. All materials were readily soluble in water, and dynamic light scattering data indicate polymer-grafted lignin coexisted in isolated and aggregated forms in aqueous media. The characteristic size was 15-20 nm at low concentrations, and aggregation appeared to be a stronger function of degree of polymerization than graft density. These species were surface active, reducing the surface tension to as low as 60 dyn/cm at 1 mg/mL, and a greater decrease was observed than for polymer-grafted silica nanoparticles, suggesting that the lignin core was also surface active. While these lignin surfactants were soluble in water, they were not soluble in hexanes. Thus, it was unexpected that water-in-oil emulsions formed in all surfactant compositions and solvent ratios tested, with average droplet sizes of 10-20 μm. However, although polymer-grafted lignin has structural features similar to nanoparticles used in Pickering emulsions, its interfacial behavior was qualitatively different. While at air-water interfaces, the hydrophilic grafts promote effective reductions in surface tension, we hypothesize that the low grafting density in these lignin surfactants favors partitioning into the hexanes side of the oil-water interface because collapsed conformations of the polymer grafts improve interfacial coverage and reduce water-hexanes interactions. We propose that polymer-grafted lignin

  9. Polymers at AN Interface: a Simplified View

    NASA Astrophysics Data System (ADS)

    de Gennes, P. G.

    An elementary description of polymers adsorbed, or terminally attached, at an interface is given. Discussion is restricted to linear, flexible, neutral chains in good solvents. Terminally attached systems, in the "brush" regime, have weak fluctuations and are thus amenable to a simple mean field description. On the other hand, the adsorbed, diffuse layers have large fluctuations and cannot be described in mean field terms. Adsorbed layers have a certain self-similar structure which allows for a compact interpretation of most fundamental data (ellipsometry, hydrodynamic thickness). Self-similarity has been proven most explicitly by recent neutron experiments of Auvray and Cotton which were made on long chains with variable contrast techniques. Recent advances on the kinetics of exchange between adsorbed and free polymer are also briefly described.

  10. Computer simulation of the static and dynamic properties of a polymer chain

    SciTech Connect

    Ceperley, David; Kalos, M. H.; Lebowitz, Joel L.

    1981-09-01

    We have carried out computer simulations of the statics and dynamics of an isolated model polymer chain with excluded volume in a solvent acting as a heat bath. We find that the disbribution function for the separation of a pair of beads scales as the number of beads N to the power {nu} and that edge effects are small. The dynamical correlation functions, such as that of the end-to-end vector, scale as N{sup 2{nu}+1} with {nu} ~ 0.6. The results of a dynamical lattice polymer model are shown to be consistent with the present results if one adjusts the time scales in such a way that the center of mass diffuses at the same rate in the two models. The relaxation of the stress tensor, is shown to be quite similar to that of the Rouse model. Finally, it is shown that edge effects are much more pronounced in the diffusive motion of the individual beads, there being a skin comprising about 30% of the total polymer, where bead motion is relatively quicker.

  11. Anisotropic Conjugated Polymer Chain Conformation Tailors the Energy Migration in Nanofibers

    PubMed Central

    2016-01-01

    Conjugated polymers are complex multichromophore systems, with emission properties strongly dependent on the electronic energy transfer through active subunits. Although the packing of the conjugated chains in the solid state is known to be a key factor to tailor the electronic energy transfer and the resulting optical properties, most of the current solution-based processing methods do not allow for effectively controlling the molecular order, thus making the full unveiling of energy transfer mechanisms very complex. Here we report on conjugated polymer fibers with tailored internal molecular order, leading to a significant enhancement of the emission quantum yield. Steady state and femtosecond time-resolved polarized spectroscopies evidence that excitation is directed toward those chromophores oriented along the fiber axis, on a typical time scale of picoseconds. These aligned and more extended chromophores, resulting from the high stretching rate and electric field applied during the fiber spinning process, lead to improved emission properties. Conjugated polymer fibers are relevant to develop optoelectronic plastic devices with enhanced and anisotropic properties. PMID:27933935

  12. Anisotropic Conjugated Polymer Chain Conformation Tailors the Energy Migration in Nanofibers.

    PubMed

    Camposeo, Andrea; Pensack, Ryan D; Moffa, Maria; Fasano, Vito; Altamura, Davide; Giannini, Cinzia; Pisignano, Dario; Scholes, Gregory D

    2016-11-30

    Conjugated polymers are complex multichromophore systems, with emission properties strongly dependent on the electronic energy transfer through active subunits. Although the packing of the conjugated chains in the solid state is known to be a key factor to tailor the electronic energy transfer and the resulting optical properties, most of the current solution-based processing methods do not allow for effectively controlling the molecular order, thus making the full unveiling of energy transfer mechanisms very complex. Here we report on conjugated polymer fibers with tailored internal molecular order, leading to a significant enhancement of the emission quantum yield. Steady state and femtosecond time-resolved polarized spectroscopies evidence that excitation is directed toward those chromophores oriented along the fiber axis, on a typical time scale of picoseconds. These aligned and more extended chromophores, resulting from the high stretching rate and electric field applied during the fiber spinning process, lead to improved emission properties. Conjugated polymer fibers are relevant to develop optoelectronic plastic devices with enhanced and anisotropic properties.

  13. Effect of confinement on the collapsing mechanism of a flexible polymer chain.

    PubMed

    Das, Siddhartha; Chakraborty, Suman

    2010-11-07

    In this paper, Brownian dynamics simulation (BDS) studies are executed to demonstrate the distinctive influences of the extent of confinement on the collapsing mechanism and kinetics of a flexible hydrophobic polymer chain in a poor solvent. The collapsing behavior is quantified by the time of collapse, which below a critical dimension of the confinement (h(c)), encounters a drastic reduction with a further strengthening in the degree of confinement. For dimensions greater than this critical one, the collapse occurs through the well-known hydrodynamic interaction (HI) controlled multiple-globule-mediated mechanisms. However, for channel dimensions less than this critical one, the collapse mechanism is drastically altered. Under such circumstances, the collapse gets predominantly controlled by the confinement effects (with negligible contribution of the HIs) and occurs via the formation of a single central globule. This central globule rapidly engulfs the noncondensed polymer segments, and in the process largely hastens up the collapsing event. Under such circumstances, the collapse time is found to decrease linearly with decrements in the channel height. On the contrary, for channel heights greater than h(c), the multiple-globule-mediated collapse is characterized by a collapse time that shows an exponential dependence on the channel height, rapidly attaining a state in which the confinement effect becomes inconsequential and HIs dictate the entire collapsing behavior. We further propose detailed arguments based on physical reasoning as well as free energy estimations to conclusively support the qualitative and quantitative nature of influences of the confinement on the polymer collapse.

  14. Exploring the effects of electrospinning processing protocols on fiber surface morphology and polymer chain conformation

    NASA Astrophysics Data System (ADS)

    Stephens, Jean S.

    Electrospinning is a fiber formation technique that uses electrostatic forces to create continuous, nanometer diameter fibers. The work presented here focuses on the continuing efforts to build a stronger fundamental understanding of electrospinning by exploring structure/property/process relationships by investigating the effects of process protocols on fiber surface morphology and polymer chain conformation. By varying the processing parameters it has been possible to produce fibers with unique surface features, microtextured/nanoporous fibers and nanowebs. In the microtextured/nanoporous fiber studies, changing the solution concentration, solvent volatility, and relative humidity was found to alter the size, shape, and distribution of pores on the fiber surface. The mechanisms that can explain the pore formation and texturing on the surface of the fibers are phase separation (aggregation into polymer rich and polymer lean regions) and breath figures (evaporative cooling and vapor condensation). Through a judicious choice of the electrospinning processing parameters we have also been able to create "web" like structures of nanofibers (5--25 nm) from collagen, dragline silk analog, nylon, and denatured collagen. Electrostatic repulsion and thin film dewetting are thought to be responsible for the formation of the nanowebs. These unique structures were characterized using FESEM, TEM, OM, and AFM. Raman spectroscopy, initially developed as a "real time" characterization technique to study electrospun fiber formation, has also been used to investigate the effect of electrospinning on the chain conformation of bioinspired polymers. Comparing the spectrum of the bulk material to that of the electrospun material identified conformational changes in nylon 6 and dragline silk analog. The conformational change in nylon 6 (alpha-form to gamma-form) results from the stresses induced on the electrospinning jet during fiber formation, whereas the conformational change in the

  15. Detachment of semiflexible polymer chains from a substrate: A molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Paturej, J.; Erbas, A.; Milchev, A.; Rostiashvili, V. G.

    2014-12-01

    Using Molecular Dynamics simulations, we study the force-induced detachment of a coarse-grained model polymer chain from an adhesive substrate. One of the chain ends is thereby pulled at constant speed off the attractive substrate and the resulting saw-tooth profile of the measured mean force ⟨f⟩ vs height D of the end-segment over the plane is analyzed for a broad variety of parameters. It is shown that the observed characteristic oscillations in the ⟨f⟩-D profile depend on the bending and not on the torsional stiffness of the detached chains. Allowing for the presence of hydrodynamic interactions (HI) in a setup with explicit solvent and dissipative particle dynamics-thermostat, rather than the case of Langevin thermostat, one finds that HI have little effect on the ⟨f⟩-D profile. Also the change of substrate affinity with respect to the solvent from solvophilic to solvophobic is found to play negligible role in the desorption process. In contrast, a changing ratio ɛ _s^B / ɛ _s^A of the binding energies of A- and B-segments in the detachment of an AB-copolymer from adhesive surface strongly changes the ⟨f⟩-D profile whereby the B-spikes vanish when ɛ _s^B / ɛ _s^A < 0.15. Eventually, performing an atomistic simulation of (bio)-polymers, we demonstrate that the simulation results, derived from our coarse-grained model, comply favorably with those from the all-atom simulation.

  16. Detachment of semiflexible polymer chains from a substrate: A molecular dynamics investigation

    SciTech Connect

    Paturej, J.; Erbas, A.; Milchev, A.; Rostiashvili, V. G.

    2014-12-07

    Using Molecular Dynamics simulations, we study the force-induced detachment of a coarse-grained model polymer chain from an adhesive substrate. One of the chain ends is thereby pulled at constant speed off the attractive substrate and the resulting saw-tooth profile of the measured mean force 〈f〉 vs height D of the end-segment over the plane is analyzed for a broad variety of parameters. It is shown that the observed characteristic oscillations in the 〈f〉-D profile depend on the bending and not on the torsional stiffness of the detached chains. Allowing for the presence of hydrodynamic interactions (HI) in a setup with explicit solvent and dissipative particle dynamics-thermostat, rather than the case of Langevin thermostat, one finds that HI have little effect on the 〈f〉-D profile. Also the change of substrate affinity with respect to the solvent from solvophilic to solvophobic is found to play negligible role in the desorption process. In contrast, a changing ratio ε{sub s}{sup B}/ε{sub s}{sup A} of the binding energies of A- and B-segments in the detachment of an AB-copolymer from adhesive surface strongly changes the 〈f〉-D profile whereby the B-spikes vanish when ε{sub s}{sup B}/ε{sub s}{sup A}<0.15. Eventually, performing an atomistic simulation of (bio)-polymers, we demonstrate that the simulation results, derived from our coarse-grained model, comply favorably with those from the all-atom simulation.

  17. Single chain structure in thin polymer films: corrections to Flory's and Silberberg's hypotheses

    NASA Astrophysics Data System (ADS)

    Cavallo, A.; Müller, M.; Wittmer, J. P.; Johner, A.; Binder, K.

    2005-05-01

    Conformational properties of polymer melts confined between two hard structureless walls are investigated by Monte Carlo simulation of the bond fluctuation model. Parallel and perpendicular components of chain extension, bond-bond correlation function and structure factor are computed and compared with recent theoretical approaches attempting to go beyond Flory's and Silberberg's hypotheses. We demonstrate that for ultrathin films where the thickness, H, is smaller than the excluded volume screening length (blob size), ξ, the chain size parallel to the walls diverges logarithmically, R2/2Napb2+clog(N) with c~1/H. The corresponding bond-bond correlation function decreases like a power law, C(s) = d/sω with s being the curvilinear distance between bonds and ω = 1. Upon increasing the film thickness, H, we find—in contrast to Flory's hypothesis—the bulk exponent ω = 3/2 and, more importantly, a decreasing d(H) that gives direct evidence for an enhanced self-interaction of chain segments reflected at the walls. Systematic deviations from the Kratky plateau as a function of H are found for the single chain form factor parallel to the walls in agreement with the non-monotonic behaviour predicted by theory. This structure in the Kratky plateau might give rise to an erroneous estimation of the chain extension from scattering experiments. For large H the deviations are linear with the wavevector, q, but are very weak. In contrast, for ultrathin films, H<ξ, very strong corrections (albeit logarithmic in q) are found suggesting a possible experimental verification of our results.

  18. Negative compressibility and nonequivalence of two statistical ensembles in the escape transition of a polymer chain.

    PubMed

    Skvortsov, A M; Klushin, L I; Leermakers, F A M

    2007-01-14

    An end-tethered polymer chain compressed between two pistons undergoes an abrupt transition from a confined coil state to an inhomogeneous flowerlike conformation partially escaped from the gap. This phase transition is first order in the thermodynamic limit of infinitely long chains. A rigorous analytical theory is presented for a Gaussian chain in two ensembles: (a) the H-ensemble, in which the distance H between the pistons plays the role of the independent control parameter, and (b) the conjugate f-ensemble, in which the external compression force f is the independent parameter. Details about the metastable chain configurations are analyzed by introducing the Landau free energy as a function of the chain stretching order parameter. The binodal and spinodal lines, as well as the barrier heights between the stable and metastable states in the free energy landscape, are presented in both ensembles. In the loop region for the average force with dependence on the distance H (i.e., in the H-ensemble) a negative compressibility exists, whereas in the f-ensemble the average distance as a function of the force is strictly monotonic. The average fraction of imprisoned segments and the lateral force, taken as functions of the distance H or the average H, respectively, have different behaviors in the two ensembles. These results demonstrate a clear counterexample of a main principle of statistical mechanics, stating that all ensembles are equivalent in the thermodynamic limit. The authors show that the negative compressibility in the escape transition is a purely equilibrium result and analyze in detail the origin of the nonequivalence of the ensembles. It is argued that it should be possible to employ the escape transition and its anomalous behavior in macroscopically homogeneous, but microscopically inhomogeneous, materials.

  19. Polymer gels with associating side chains and their interaction with surfactants

    NASA Astrophysics Data System (ADS)

    Gordievskaya, Yulia D.; Rumyantsev, Artem M.; Kramarenko, Elena Yu.

    2016-05-01

    Conformational behaviour of hydrophobically modified (HM) polymer gels in solutions of nonionic surfactants is studied theoretically. A HM gel contains hydrophobic side chains (stickers) grafted to its subchains. Hydrophobic stickers are capable to aggregate into joint micelles with surfactant molecules. Micelles containing more than one sticker serve as additional physical cross-links of the network, and their formation causes gel shrinking. In the proposed theoretical model, the interior of the gel/surfactant complex is treated as an array of densely packed spherical polymer brushes consisting of gel subchains tethered to the surface of the spherical sticker/surfactant micelles. Effect of stickers length and grafting density, surfactant concentration and hydrophobicity on gel swelling as well as on hydrophobic association inside it is analyzed. It is shown that increasing surfactant concentration can result in a gel collapse, which is caused by surfactant-induced hydrophobic aggregation of stickers, and a successive gel reswelling. The latter should be attributed to a growing fraction of surfactants in joint aggregates and, hence, increasing number of micelles containing only one sticker and not participating in gel physical cross-linking. In polyelectrolyte (PE) gels hydrophobic aggregation is opposed by osmotic pressure of mobile counterions, so that at some critical ionization degree hydrophobic association is completely suppressed. Hydrophobic modification of polymers is shown to open new ways for controlling gel responsiveness. In particular, it is discussed that incorporation of photosensitive groups into gel subchains and/or surfactant tail could give a possibility to vary the gel volume by light. Since hydrophobic aggregation regularities in gels and solutions are common, we hope our findings will be useful for design of polymer based self-healing materials as well.

  20. IgG adsorption on a new protein A adsorbent based on macroporous hydrophilic polymers. I. Adsorption equilibrium and kinetics.

    PubMed

    Perez-Almodovar, Ernie X; Carta, Giorgio

    2009-11-20

    Experimental determination and modeling of IgG binding on a new protein A adsorbent based on a macroporous resin were performed. The new adsorbent consists of polymeric beads based on hydrophilic acrylamido and vinyl monomers with a pore structure optimized to allow favorable interactions of IgG with recombinant protein A coupled to the resin. The particles have average diameter of 57 microm and a narrow particle size distribution. The IgG adsorption equilibrium capacity is 46 mg/cm(3) and the effective pore diffusivity determined from pulse response experiments for non-binding conditions is 8.0 x 10(-8) cm(2)/s. The IgG adsorption kinetics can be described with the same effective diffusivity by taking into account a heterogeneous binding mechanism with fast binding sites, for which adsorption is completely diffusion controlled, and slow binding sites for which adsorption is controlled by the binding kinetics. As a result of this mechanism, the breakthrough curve exhibits a tailing behavior, which appears to be associated with the slow binding sites. A detailed rate model taking into account intraparticle diffusion and binding kinetics is developed and is found capable of predicting both batch adsorption and breakthrough behavior over an ample range of experimental conditions. The corresponding effective diffusivity is independent of protein concentration in solution over the range 0.2-2 mg/cm(3) and of protein binding as a result of the large pore size of the support matrix. Overall, the small particle size and low diffusional hindrance allow capture of IgG with short residence times while attaining substantial dynamic binding capacities.

  1. Development of molecularly imprinted polymer-based field effect transistor for sugar chain sensing

    NASA Astrophysics Data System (ADS)

    Nishitani, Shoichi; Kajisa, Taira; Sakata, Toshiya

    2017-04-01

    In this study, we developed a molecularly imprinted polymer-based field-effect transistor (MIP-gate FET) for selectively detecting sugar chains in aqueous media, focusing on 3‧-sialyllactose (3SLac) and 6‧-sialyllactose (6SLac). The FET biosensor enables the detection of small molecules as long as they have intrinsic charges. Additionally, the MIP gels include the template for the target molecule, which is selectively trapped without requiring enzyme-target molecule reaction. The MIP gels were synthesized on the gate surface of the FET device, including phenylboronic acid (PBA), which enables binding to sugar chains. Firstly, the 3SLac-MIP-gate FET quantitatively detected 3SLac at µM levels. This is because the FET device recognized the change in molecular charges on the basis of PBA-3SLac binding in the MIP gel. Moreover, 3SLac was selectively detected using the 3SLac- and 6SLac-MIP-gate FETs to some extent, where the detecting signal from the competent was suppressed by 40% at maximum. Therefore, a platform based on the MIP-coupled FET biosensor is suitable for a selective biosensing system in an enzyme-free manner, which can be applied widely in medical fields. However, we need to further improve the selectivity of MIP-gate FETs to discriminate more clearly between similar structures of sugar chains such as 3SLac and 6SLac.

  2. Organization of polymer chains onto long, single-wall carbon nano-tubes: effect of tube diameter and cooling method.

    PubMed

    Kumar, Sunil; Pattanayek, Sudip K; Pereira, Gerald G

    2014-01-14

    We use molecular dynamics simulations to investigate the arrangement of polymer chains when absorbed onto a long, single-wall carbon nano-tube (SWCNT). We study the conformation and organization of the polymer chains on the SWCNT and their dependence on the tube's diameter and the rate of cooling. We use two types of cooling processes: direct quenching and gradual cooling. The radial density distribution function and bond orientational order parameter are used to characterize the polymer chain structure near the surface. In the direct cooling process, the beads of the polymer chain organize in lamella-like patterns on the surface of the SWCNT with the long axis of the lamella parallel to the axis of the SWCNT. In a stepwise, gradual cooling process, the polymer beads form a helical pattern on the surface of a relatively thick SWCNT, but form a lamella-like pattern on the surface of a very thin SWCNT. We develop a theoretical (free energy) model to explain this difference in pattern structures for the gradual cooling process and also provide a qualitative explanation for the pattern that forms from the direct cooling process.

  3. Effect of chain stiffness and temperature on the dynamics and microstructure of crystallizable bead-spring polymer melts

    NASA Astrophysics Data System (ADS)

    Nguyen, Hong T.; Hoy, Robert S.

    2016-11-01

    We contrast the dynamics in model unentangled polymer melts of chains of three different stiffnesses: flexible, intermediate, and rodlike. Flexible and rodlike chains, which readily solidify into close-packed crystals (respectively, with randomly oriented and nematically aligned chains), display simple melt dynamics with Arrhenius temperature dependence and a discontinuous change upon solidification. Intermediate-stiffness chains, however, are fragile glass-formers displaying Vogel-Fulcher dynamical arrest, despite the fact that they also possess a nematic-close-packed crystalline ground state. To connect this difference in dynamics to the differing microstructure of the melts, we examine how various measures of structure, including cluster-level metrics recently introduced in studies of colloidal systems, vary with chain stiffness and temperature. No clear static-structural cause of the dynamical arrest is found. However, we find that the intermediate-stiffness chains display qualitatively different dynamical heterogeneity. Specifically, their stringlike motion (cooperative rearrangement) is correlated along chain backbones in a way not found for either flexible or rodlike chains. This activated "crawling" motion is clearly associated with the dynamical arrest observed in these systems, and illustrates one way in which factors controlling the crystallization versus glass formation competition in polymers can depend nonmonotonically on chain stiffness.

  4. Molecular structure of an alkyl-side-chain polymer-water interface: origins of contact angle hysteresis.

    PubMed

    Rangwalla, Hasnain; Schwab, Alexander D; Yurdumakan, Betül; Yablon, Dalia G; Yeganeh, Mohsen S; Dhinojwala, Ali

    2004-09-28

    A new and direct approach to verify surface heterogeneity as the microscopic origin of contact-angle hysteresis is demonstrated. IR-visible sum-frequency-generation spectroscopy (SFG) was used to selectively probe the molecules at the interface of an alkyl-side-chain polymer [poly(vinyl n-octadecyl carbamate-co-vinyl acetate)] with water. The spectra indicate that in contact with water, the polymer surface is heterogeneous (having areas of differing surface energies). This evidence of surface heterogeneity supports the hysteresis observed in the advancing and receding contact angles of the polymer surface with water. The same measurements made for the chemically and structurally similar surface of an octadecyltrichlorosilane self-assembled monolayer indicates a homogeneous surface at the water interface. In this case, contact-angle hysteresis measurements implicate surface roughness as the cause of hysteresis. Atomic force microscopy measurements of roughness for these surfaces further support our conclusions. The polymer-water interface was probed using SFG at above-ambient temperatures, and an order-to-disorder transition (ODT) of alkyl side chains at the interface was observed, which closely follows the melting of crystalline side chains in the bulk. This transition explains the increased wettability of the polymer, by water, when the temperature is raised above the bulk melting temperature. Furthermore, the irreversibility of this ODT suggests that the disordered polymer-water interface is the thermodynamic equilibrium state, whereas the before-heating structure of this interface is a kinetically hindered metastable state.

  5. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-09-06

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  6. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra

    2014-05-13

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  7. Density-functional theory for polymer-carbon dioxide mixtures: A perturbed-chain SAFT approach

    NASA Astrophysics Data System (ADS)

    Xu, Xiaofei; Cristancho, Diego E.; Costeux, Stéphane; Wang, Zhen-Gang

    2012-08-01

    We propose a density-functional theory (DFT) describing inhomogeneous polymer-carbon dioxide mixtures based on a perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS). The weight density functions from fundamental measure theory are used to extend the bulk excess Helmholtz free energy to the inhomogeneous case. The additional long-range dispersion contributions are included using a mean-field approach. We apply our DFT to the interfacial properties of polystyrene-CO2 and poly(methyl methacrylate) CO2 systems. Calculated values for both solubility and interfacial tension are in good agreement with experimental data. In comparison with our earlier DFT based on the Peng-Robinson-SAFT EOS, the current DFT produces quantitatively superior agreement with experimental data and is free of the unphysical behavior at high pressures (>35 MPa) in the earlier theory.

  8. Shape-Selectivity with Liquid Crystal and Side-Chain Liquid Crystalline Polymer SAW Sensor Interfaces

    SciTech Connect

    FRYE-MASON,GREGORY CHARLES; OBORNY,MICHAEL C.; PUGH,COLEEN; RICCO,ANTONIO; THOMAS,ROSS C.; ZELLERS,EDWARD T.; ZHANG,GUO-ZHENG

    1999-09-23

    A liquid crystal (LC) and a side-chain liquid crystalline polymer (SCLCP) were tested as surface acoustic wave (SAW) vapor sensor coatings for discriminating between pairs of isomeric organic vapors. Both exhibit room temperature smectic mesophases. Temperature, electric-field, and pretreatment with self-assembled monolayers comprising either a methyl-terminated or carboxylic acid-terminated alkane thiol anchored to a gold layer in the delay path of the sensor were explored as means of affecting the alignment and selectivity of the LC and SCLCP films. Results for the LC were mixed, while those for the SCLCP showed a consistent preference for the more rod-like isomer of each isomer pair examined.

  9. Spatially confined polymer chains: implications of chromatin fibre flexibility and peripheral anchoring on telomere telomere interaction

    NASA Astrophysics Data System (ADS)

    Gehlen, L. R.; Rosa, A.; Klenin, K.; Langowski, J.; Gasser, S. M.; Bystricky, K.

    2006-04-01

    We simulate the extension of spatially confined chromatin fibres modelled as polymer chains and examine the effect of the flexibility of the fibre and its degree of freedom. The developed formalism was used to analyse experimental data of telomere-telomere distances in living yeast cells in the absence of confining factors as identified by the proteins Sir4 and yKu70. Our analysis indicates that intrinsic properties of the chromatin fibre, in particular its elastic properties and flexibility, can influence the juxtaposition of the telomeric ends of chromosomes. However, measurements in intact yeast cells showed that the telomeres of chromosomes 3 and 6 come even closer together than the parameters of constraint imposed on the simulations would predict. This juxtaposition was specific to telomeres on one contiguous chromosome and overrode a tendency for separation that is imposed by anchoring.

  10. Statistical geometry of lattice chain polymers with voids of defined shapes: sampling with strong constraints.

    PubMed

    Lin, Ming; Chen, Rong; Liang, Jie

    2008-02-28

    Proteins contain many voids, which are unfilled spaces enclosed in the interior. A few of them have shapes compatible to ligands and substrates and are important for protein functions. An important general question is how the need for maintaining functional voids is influenced by, and affects other aspects of proteins structures and properties (e.g., protein folding stability, kinetic accessibility, and evolution selection pressure). In this paper, we examine in detail the effects of maintaining voids of different shapes and sizes using two-dimensional lattice models. We study the propensity for conformations to form a void of specific shape, which is related to the entropic cost of void maintenance. We also study the location that voids of a specific shape and size tend to form, and the influence of compactness on the formation of such voids. As enumeration is infeasible for long chain polymer, a key development in this work is the design of a novel sequential Monte Carlo strategy for generating large number of sample conformations under very constraining restrictions. Our method is validated by comparing results obtained from sampling and from enumeration for short polymer chains. We succeeded in accurate estimation of entropic cost of void maintenance, with and without an increasing number of restrictive conditions, such as loops forming the wall of void with fixed length, with additionally fixed starting position in the sequence. Additionally, we have identified the key structural properties of voids that are important in determining the entropic cost of void formation. We have further developed a parametric model to predict quantitatively void entropy. Our model is highly effective, and these results indicate that voids representing functional sites can be used as an improved model for studying the evolution of protein functions and how protein function relates to protein stability.

  11. Statistical geometry of lattice chain polymers with voids of defined shapes: Sampling with strong constraints

    NASA Astrophysics Data System (ADS)

    Lin, Ming; Chen, Rong; Liang, Jie

    2008-02-01

    Proteins contain many voids, which are unfilled spaces enclosed in the interior. A few of them have shapes compatible to ligands and substrates and are important for protein functions. An important general question is how the need for maintaining functional voids is influenced by, and affects other aspects of proteins structures and properties (e.g., protein folding stability, kinetic accessibility, and evolution selection pressure). In this paper, we examine in detail the effects of maintaining voids of different shapes and sizes using two-dimensional lattice models. We study the propensity for conformations to form a void of specific shape, which is related to the entropic cost of void maintenance. We also study the location that voids of a specific shape and size tend to form, and the influence of compactness on the formation of such voids. As enumeration is infeasible for long chain polymer, a key development in this work is the design of a novel sequential Monte Carlo strategy for generating large number of sample conformations under very constraining restrictions. Our method is validated by comparing results obtained from sampling and from enumeration for short polymer chains. We succeeded in accurate estimation of entropic cost of void maintenance, with and without an increasing number of restrictive conditions, such as loops forming the wall of void with fixed length, with additionally fixed starting position in the sequence. Additionally, we have identified the key structural properties of voids that are important in determining the entropic cost of void formation. We have further developed a parametric model to predict quantitatively void entropy. Our model is highly effective, and these results indicate that voids representing functional sites can be used as an improved model for studying the evolution of protein functions and how protein function relates to protein stability.

  12. Hierarchical supramolecular ordering with biaxial orientation of a combined main-chain/side-chain liquid-crystalline polymer obtained from radical polymerization of 2-vinylterephthalate.

    PubMed

    Xie, He-Lou; Jie, Chang-Kai; Yu, Zhen-Qiang; Liu, Xuan-Bo; Zhang, Hai-Liang; Shen, Zhihao; Chen, Er-Qiang; Zhou, Qi-Feng

    2010-06-16

    The liquid-crystalline (LC) phase structures and transitions of a combined main-chain/side-chain LC polymer (MCSCLCP) 1 obtained from radical polymerization of a 2-vinylterephthalate, poly(2,5-bis{[6-(4-butoxy-4'-oxybiphenyl) hexyl]oxycarbonyl}styrene), were studied using differential scanning calorimetry, one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD), and polarized light microscopy. We have found that 1 with sufficiently high molecular weight can self-assemble into a hierarchical structure with double orderings on the nanometer and subnanometer scales at low temperatures. The main chains of 1, which are rodlike as a result of the "jacketing" effect generated by the central rigid portion of the side chains laterally attached to every second carbon atom along the polyethylene backbone, form a 2D centered rectangular scaffold. The biphenyl-containing side chains fill the space between the main chains, forming a smectic E (SmE)-like structure with the side-chain axis perpendicular to that of the main chain. This biaxial orientation of 1 was confirmed by our 2D WAXD experiments through three orthogonal directions. The main-chain scaffold remains when the SmE-like packing is melted at elevated temperatures. Further heating leads to a normal smectic A (SmA) structure followed by the isotropic state. We found that when an external electric field was applied, the main-chain scaffold greatly inhibited the motion of the biphenyls. While the main chains gain a sufficiently high mobility in the SmA phase, macroscopic orientation of 1 can be achieved using a rather weak electric field, implying that the main and side chains with orthogonal directions can move cooperatively. Our work demonstrates that when two separate components, one offering the "jacketing" effect to the normally flexible backbone and the other with mesogens that form surrounding LC phases, are introduced simultaneously into the side chains, the polymer obtained can be described as an

  13. Biogenesis and the growth of DNA-like polymer chains: A computer simulation

    NASA Astrophysics Data System (ADS)

    Herrmann, Hans J.; Tsallis, Constantino

    1988-11-01

    We study, through computer simulation, a crucial step of biogenesis, namely the growth of self-replicating codified DNA-like polymers starting from a mixture of oligomers. We have adopted the growth scheme that has been recently proposed by Ferreira and Tsallis which incorporates usual ideas of autocatalysis through complementary pairs and within which a central role is played by the hydrogen-like links (characterized by the probabilities pAT and PCG of chemical bonding of the A-T and C-G pairs respectively) between the two chains of the growing polymer. We find that the average equilibrium polymeric length ξ diverges, for any fixed ratio (1 - pAT)/(1 - pCG), as ξ ∝ 1/√1 - pAT. Selection of patterns may happen at all stages and in particular at chemical equilibrium. Selection occurs via two different mechanisms: (i) away from the critical point pAT = pCG = 1 if PAT ≠ PCG; (ii) both on and away from the critical point if the initial concentrations of nucleotides (A, T, C and G or their precursors) are different.

  14. Microscopic observation of the segmental orientation autocorrelation function for entangled and constrained polymer chains

    NASA Astrophysics Data System (ADS)

    Mordvinkin, Anton; Saalwächter, Kay

    2017-03-01

    Previous work on probing the dynamics of reptating polymer chains in terms of the segmental orientation autocorrelation function (OACF) by multiple-quantum (MQ) NMR relied on the time-temperature superposition (TTS) principle as applied to normalized double-quantum (DQ) build-up curves. Alternatively, an initial-rise analysis of the latter is also possible. These approaches are subject to uncertainties related to the relevant segmental shift factor or parasitic signals and inhomogeneities distorting the build-up at short times, respectively. Here, we present a simple analytical fitting approach based upon a power-law model of the OACF, by the way of which an effective power-law time scaling exponent and the amplitude of the OACF can be estimated from MQ NMR data at any given temperature. This obviates the use of TTS and provides a robust and independent probe of the shape of the OACF. The approach is validated by application to polymer melts of variable molecular weight as well as elastomers. We anticipate a wide range of applications, including the study of physical networks with labile junctions.

  15. Probing the conformation and 2D-distribution of pyrene-terminated redox-labeled poly(ethylene glycol) chains end-adsorbed on HOPG using cyclic voltammetry and atomic force electrochemical microscopy.

    PubMed

    Anne, Agnès; Bahri, Mohamed Ali; Chovin, Arnaud; Demaille, Christophe; Taofifenua, Cécilia

    2014-03-14

    The present paper aims at illustrating how end-attachment of water-soluble flexible chains bearing a terminal functional group onto graphene-like surfaces has to be carefully tuned to ensure the proper positioning of the functional moiety with respect to the anchoring surface. The model experimental system considered here consists of a layer of poly(ethylene glycol) (PEG) chains, bearing an adsorbing pyrene foot and a ferrocene (Fc) redox functional head, self-assembled onto highly oriented pyrolytic graphite (HOPG). Cyclic voltammetry is used to accurately measure the chain coverage and gain insights into the microenvironment experienced by the Fc heads. Molecule-touching atomic force electrochemical microscopy (Mt/AFM-SECM) is used to simultaneously probe the chain conformation and the position of the Fc heads within the layer, and also to map the 2D-distribution of the chains over the surface. This multiscale electrochemical approach allows us to show that whereas Fc-PEG-pyrene readily self-assembles to form extremely homogeneous layers, the strongly hydrophobic nature of graphite planes results in a complex coverage-dependent structure of the PEG layer due to the interaction of the ferrocene label with the HOPG surface. It is shown that, even though pyrene is known to adsorb particularly strongly onto HOPG, the more weakly adsorbing terminal ferrocene can also act as the chain anchoring moiety especially at low coverage. However we show that beyond a critical coverage value the Fc-PEG-pyrene chains adopt an ideal "foot-on" end-attached conformation allowing the Fc head to explore a volume away from the surface solely limited by the PEG chain elasticity.

  16. In situ growth of side-chain PEG polymers from functionalized human growth hormone-a new technique for preparation of enhanced protein-polymer conjugates.

    PubMed

    Magnusson, Johannes Pall; Bersani, Sara; Salmaso, Stefano; Alexander, Cameron; Caliceti, Paolo

    2010-04-21

    The application of atom transfer radical polymerization (ATRP) for preparation of a novel class of protein-polymer bioconjugates is described, exemplified by the synthesis of a recombinant human growth hormone (rh-GH) poly(ethylene glycol) methyl ether methacrylate (PEGMA) hybrid. The rh-GH protein was activated via a bromo-ester functionalized linker and used as a macroinitiator to polymerize the hydrophilic monomer PEGMA under solely aqueous conditions at 4 degrees C. ATRP conditions resulted in controlled polymer growth from rh-GH with low-polydispersity polyPEGMA chains. The rh-GH PEGMA product exhibited properties consistent with the presence of attached hydrophilic polymer chains, namely, high stability to denaturation and proteolysis. The polymerization conditions and conjugation proceeded with retention of the biological activity of the hormone. The rh-GH PEGMA was administered subcutaneously to rats and the activity compared to native rh-GH. The rh-GH PEGMA exhibited similar activity as the native rh-GH in vivo when a daily dose of 40 microg was administered. However, when a higher dose of 120 microg was administered with 3 days between injections the bioavailability of the rh-GH PEGMA was significantly better than that of the native. The results therefore demonstrate that ATRP can be successfully used as a general alternative approach to direct polymer conjugation, namely, PEGylation, to produce PEG-like protein conjugates. This technique can be exploited to design and synthesize protein-polymer derivatives with tailored therapeutic properties.

  17. Adsorption of peptides and small proteins with control access polymer permeation to affinity binding sites. Part II: Polymer permeation-ion exchange separation adsorbents with polyethylene glycol and strong anion exchange groups.

    PubMed

    González-Ortega, Omar; Porath, Jerker; Guzmán, Roberto

    2012-03-02

    In chromatographic separations, the most general problem in small biomolecule isolation and purification is that such biomolecules are usually found in extremely low concentrations together with high concentrations of large molecular weight proteins. In the first part of this work, adsorption and size exclusion chromatography (AdSEC) controlled access media, using polyethylene glycol (PEG) as a semi-permeable barrier on a polysaccharide Immobilized Metal Affinity Chromatography (IMAC) matrix was synthesized and used to develop chromatographic adsorbents that preferentially adsorb and separate low molecular weight biomolecules while rejecting large molecular weight proteins. In this second part, we expand the concept of controlled access polymer permeation adsorption (CAPPA) media by grafting polyethylene glycol (PEG) on a high capacity polysaccharide ion exchange (IEX) chromatographic resin where PEG acts as a semi-permeable barrier that preferentially allows the permeation of small molecules while rejecting large ones. The IEX resin bearing quaternary ammonium groups binds permeated biomolecules according to their ion exchange affinity while excluding large biomolecules by the PEG barrier and thus cannot compete for the binding sites. This new AdSEC media was used to study the retention of peptides and proteins covering a wide range of molecular weights from 1 to 150 kDa. The effect of protein molecular weight towards retention by ion exchange was performed using pure protein solutions. Recovery of insulin from insulin-spiked human serum and insulin-spiked human urine was evaluated under polymer controlled permeation conditions. The CAPPA media consisted of agarose beads modified with amino-PEG-methoxy and with trimethyl ammonium groups, having chloride capacities between 20 and 40 μeq/mL and were effective in rejecting high molecular weight proteins while allowing the preferential adsorption of small proteins and peptides.

  18. Protein-resistant polymer coatings based on surface-adsorbed poly(aminoethyl methacrylate)/poly(ethylene glycol) copolymers.

    PubMed

    Ionov, Leonid; Synytska, Alla; Kaul, Elisabeth; Diez, Stefan

    2010-01-11

    We report on the protein-resistant properties of glass substrates coated with novel copolymers of 2-aminoethyl methacrylate hydrochloride and poly(ethylene glycol) methyl ether methacrylate (AEM-PEG). In comparison to currently available protein-blocking polymer systems, such as poly-l-lysine-poly(ethylene glycol), silane-based poly(ethylene glycol), and poly(ethylene glycol) brushes prepared by surface-initiated polymerization, the proposed AEM-PEG offers the combined advantages of low cost, simplicity of use, and applicability in aqueous solutions. We demonstrate the capability of AEM-PEG to block the surface binding of globular proteins (tubulin), their assemblies (microtubules), and functional motor proteins (kinesin-1). Moreover, we demonstrate the applicability of AEM-PEG for surface patterning of proteins in microfluidic devices.

  19. Large-scale simulations of a polymer melt/brush interface: Adhesion enhancement due to surface-tethered chains

    NASA Astrophysics Data System (ADS)

    Sides, Scott; Grest, Gary; Stevens, Mark

    2000-03-01

    Many important adhesives consist of polymeric materials, that are used to bind together flat, hard surfaces. Experiments like the JKR pull test are able to measure the work needed to separate a polymer melt in contact with a flat substrate. Ignoring macroscopic dissipation mechanisms due to viscoelastic effects within the polymer melt, the work of adhesion is related to van der Waals forces between the substrate and melt. Recent experiments have shown that polymer chains tethered to the substrate enhance adhesion due to entanglements with the polymer melt. (L. Léger, E. Raphaël and H. Hervet, in Advances In Polymer Science), edited by S. Granick (Springer, Berlin, 1999), v. 138, p. 185. This increase in the work of adhesion (W_A) is a non-monotonic function of both the length (N) and surface density (σ) of the tethered chains. Using molecular dynamics (MD) simulations we study the dependence of WA on N, σ and the pulling rate. In our simulations, we also observe the various microscopic dissipation mechanisms such as pull-out and scission of the end-tethered chains, which is difficult to observe directly in an experiment. These large simulations are made possible by using a massively-parallel MD code run on Sandia's teraflop machine.

  20. Heat conduction in chain polymer liquids: molecular dynamics study on the contributions of inter- and intramolecular energy transfer.

    PubMed

    Ohara, Taku; Yuan, Tan Chia; Torii, Daichi; Kikugawa, Gota; Kosugi, Naohiro

    2011-07-21

    In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7T(c)), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors' previous study [J. Chem. Phys. 128, 044504 (2008)], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water.

  1. Intricacies of Polymer Dewetting: Nanoscaled Architectures for the Tailored Control of Polystyrene Thin Film Stability

    NASA Astrophysics Data System (ADS)

    Cheung, Justin; Sen, Mani; Chen, Zhizhao; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Satija, Sushil

    Recently, structural properties of polymer thin films have garnered attention for their relevance in the fields of organic photovoltaics and biosensors. The dewetting of polymer films poses an obstacle in the face of widespread implementation. For this study, we show that adsorbed polymer chains on a substrate surface play crucial roles in film stability. Polystyrene (PS) thin films (20 nm in thickness) with different molecular weights (Mw) on silicon (Si) substrates were used as a model. The PS films were annealed at high temperatures for several days, and Mw dependence on film stability was evidenced. At the same time, the annealed PS films were leached with a good solvent and the residue films (i.e., irreversibly adsorbed layers) were characterized by x-ray reflectivity (XR). We reveal strong correlation between film stability and two different interfacial structures of the adsorbed polymer chains: their opposing wettability against chemically identical free polymer chains results in a wetting-dewetting transition at the adsorbed polymer-free polymer interface. This is a unique aspect of polymer thin film stability and may be generalizable to other polymer systems regardless of the magnitude of solid-polymer attractive interactions. We acknowledge the financial support of NSF Grant (CMMI-1332499).

  2. Triazine-Based Sequence-Defined Polymers with Side-Chain Diversity and Backbone-Backbone Interaction Motifs.

    PubMed

    Grate, Jay W; Mo, Kai-For; Daily, Michael D

    2016-03-14

    Sequence control in polymers, well-known in nature, encodes structure and functionality. Here we introduce a new architecture, based on the nucleophilic aromatic substitution chemistry of cyanuric chloride, that creates a new class of sequence-defined polymers dubbed TZPs. Proof of concept is demonstrated with two synthesized hexamers, having neutral and ionizable side chains. Molecular dynamics simulations show backbone-backbone interactions, including H-bonding motifs and pi-pi interactions. This architecture is arguably biomimetic while differing from sequence-defined polymers having peptide bonds. The synthetic methodology supports the structural diversity of side chains known in peptides, as well as backbone-backbone hydrogen-bonding motifs, and will thus enable new macromolecules and materials with useful functions.

  3. In situ Fourier transform-infrared internal reflection spectroscopic analysis of hydrocarbon chain ordering of surfactants adsorbed at mineral oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cross, William Murray

    The adsorption of surfactants at mineral oxide surfaces was investigated by in situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS), and contact angle goniometry. FT-IR/IRS was used to determine both adsorption isotherms and the enthalpy of adsorption. Furthermore, the conformation and orientation of the hydrocarbon chain of SDS adsorbed at a sapphire internal reflection element (IRE) were determined. Contact angle goniometry was used to measure the effect of the surface phase of the surfactant on the hydrophobic character of sapphire surfaces in aqueous solutions. For SDS adsorbed by sapphire, in situ FT-IR/IRS experiments indicate that a surface phase transition occurs at an adsorption density of 2 to 3 x 10-10 mol/cm2 for both pD 2.9 and 6.9. This transition is characterized by a two to four wavenumber shift in the position of the asymmetric -CH2 stretching band. Based on solution spectroscopy studies, the surface phase was found to be similar to solution phase micelles and liquid crystals for adsorption densities less than the adsorption density of the surface phase transition. Whereas for adsorption densities in excess of the adsorption density of the surface phase transition, the surface phase resembled a solution phase coagel species. It was also found that the contact angle of an air bubble at the sapphire surface exhibited a sharp decrease at the adsorption density corresponding to the surface phase transition The effect of temperature on adsorption and phase behavior of SDS at the sapphire IRE surface was also determined. It was shown that a surface phase transition similar to that discussed occurred at approximately 298 K. The adsorption reaction was found to be exothermic, with a heat of adsorption of --1.3 kcal/mole for adsorption densities less than the adsorption density of the surface phase transition at 298 K and --4.1 kcal/mole for adsorption densities greater than the adsorption density of the surface phase transition

  4. Monte Carlo simulations of a polymer chain conformation. The effectiveness of local moves algorithms and estimation of entropy.

    PubMed

    Mańka, Agnieszka; Nowicki, Waldemar; Nowicka, Grażyna

    2013-09-01

    A linear chain on a simple cubic lattice was simulated by the Metropolis Monte Carlo method using a combination of local and non-local chain modifications. Kink-jump, crankshaft, reptation and end-segment moves were used for local changes of the chain conformation, while for non-local chain rearrangements the "cut-and-paste" algorithm was employed. The statistics of local micromodifications was examined. An approximate method for estimating the conformational entropy of a polymer chain, based on the efficiency of the kink-jump motion respecting chain continuity and excluded volume constraints, was proposed. The method was tested by calculating the conformational entropy of the undisturbed chain, the chain under tension and in different solvent conditions (athermal, theta and poor) and also of the chain confined in a slit. The results of these test calculations are qualitatively consistent with expectations. Moreover, the obtained values of the conformational entropy of self avoiding chain with ends fixed over different separations, agree very well with the available literature data.

  5. Crystal structures and thermodynamics/kinetics of Zn(II) coordination polymers with helical chains

    NASA Astrophysics Data System (ADS)

    He, Tian; Yue, Ke-Fen; Zhao, Yi-xing; Chen, San-Ping; Zhou, Chun-sheng; Yan, Ni

    2016-07-01

    Solvothermal reactions of Zn(II) acetates and four V-shaped carboxylates ligands in the presence of 1,4-Bis(2-methyl-imidazol-1-yl)butane afforded four interesting Zn(II) coordination polymers with helical chains, namely, {[Zn(bib)(atibdc)]·2H2O}n (1), {[Zn(bib)(atbip)]·H2O}n (2), [Zn(bib)(2,2‧-tda)]}n (3) and {[Zn(bib)(5-tbipa)]·EtOH}n (4), (H2atibdc=5-amino-2,4,6-triiodoisophthalic acid, H2atbip=5-amino-2,4,6-tribromoisophthalic acid, 2,2‧-H2tad=2,2‧-thiodiacetic acid, 5-H2tbipa=5-tert-butyl-isophthalic acid). 1 reveals a 3D chiral framework with three kinds of helical chains along a, b and c axis. 2 shows a 2D step-type chiral framework with right-handed helical chains. 3 displays a wavelike 2D layer network possessing alternate left- and right-handed helical chains. 4 presents a four-connected 3D framework with zigzag and meso-helical chains. The different spacers and substituent group of carboxylic acid ligands may lead to the diverse network structures of 1-4. The fluorescent properties of complexes 1-4 were studied. In addition, the thermal decompositions properties of 1-4 were investigated by simultaneous TG/DTG-DSC technique. The apparent activation energy E and the pre-exponential factor (A) of skeleton collapse for the complexes 1-4 are calculated by the integral Kissinger's method and Ozawa-Doyle's method. The activation energy E (E1=209.658 kJ·mol-1, E2=250.037 kJ mol-1, E3=225.300 kJ mol-1, E4=186.529 kJ·mol-1) demonstrates that the reaction rate of the melting decomposition is slow. The thermodynamic parameters (ΔH‡, ΔG‡ and ΔS‡) at the peak temperatures of the DTG curves were also calculated. ΔG‡>0 indicates that the skeleton collapse is not spontaneous. ΔHd>0 suggests that the skeleton collapse is endothermic, corresponding to the intense endothermic peak of the DSC curve. The structural stability could be illustrated from the point of thermodynamics and kinetics.

  6. Effect of chain stiffness on the competition between crystallization and glass-formation in model unentangled polymers

    NASA Astrophysics Data System (ADS)

    Nguyen, Hong T.; Smith, Tyler B.; Hoy, Robert S.; Karayiannis, Nikos Ch.

    2015-10-01

    We map out the solid-state morphologies formed by model soft-pearl-necklace polymers as a function of chain stiffness, spanning the range from fully flexible to rodlike chains. The ratio of Kuhn length to bead diameter (lK/r0) increases monotonically with increasing bending stiffness kb and yields a one-parameter model that relates chain shape to bulk morphology. In the flexible limit, monomers occupy the sites of close-packed crystallites while chains retain random-walk-like order. In the rodlike limit, nematic chain ordering typical of lamellar precursors coexists with close-packing. At intermediate values of bending stiffness, the competition between random-walk-like and nematic chain ordering produces glass-formation; the range of kb over which this occurs increases with the thermal cooling rate | T ˙ | implemented in our molecular dynamics simulations. Finally, values of kb between the glass-forming and rodlike ranges produce complex ordered phases such as close-packed spirals. Our results should provide a useful initial step in a coarse-grained modeling approach to systematically determining the effect of chain stiffness on the crystallization-vs-glass-formation competition in both synthetic and colloidal polymers.

  7. Stretching and imaging of single DNA chains on a hydrophobic polymer surface made of amphiphilic alternating comb-copolymer.

    PubMed

    Liu, Rongrong; Wong, Sheau Tyug; Lau, Peggy Pei Zhi; Tomczak, Nikodem

    2014-02-26

    Functionalization of amine derivatized glass slides with a poly(maleic anhydride)-based comb-copolymer to facilitate stretching, aligning, and imaging of individual dsDNA chains is presented. The polymer-coated surface is hydrophobic due to the presence of the long alkyl side chains along the polymer backbone. The surface is also characterized by low roughness and a globular morphology. Stretched and aligned bacteriophage λ-DNA chains were obtained using a robust method based on stretching by a receding water meniscus at pH 7.8 without the need for small droplet volumes or precoating the surface with additional layers of (bio)molecules. Although the dye to DNA base pairs ratio did not influence substantially the stretching length distributions, a clear peak at stretching lengths close to the contour length of the dsDNA is visible at larger staining ratios.

  8. Adsorbent phosphates

    NASA Technical Reports Server (NTRS)

    Watanabe, S.

    1983-01-01

    An adsorbent which uses as its primary ingredient phosphoric acid salts of zirconium or titanium is presented. Production methods are discussed and several examples are detailed. Measurements of separating characteristics of some gases using the salts are given.

  9. Pruned-enriched Rosenbluth method: Simulations of θ polymers of chain length up to 1 000 000

    NASA Astrophysics Data System (ADS)

    Grassberger, Peter

    1997-09-01

    We present an algorithm for simulating flexible chain polymers. It combines the Rosenbluth-Rosenbluth method with recursive enrichment. Although it can be applied also in more general situations, it is most efficient for three-dimensional θ polymers on the simple-cubic lattice. There it allows high statistics simulations of chains of length up to N=106. For storage reasons, this is feasable only for polymers in a finite volume. For free θ polymers in infinite volume, we present very high statistics runs with N=10 000. These simulations fully agree with previous simulations made by Hegger and Grassberger [J. Chem. Phys. 102, 6681 (1995)] with a similar but less efficient algorithm, showing that logarithmic corrections to mean field behavior are much stronger than predicted by field theory. But the finite volume simulations show that the density inside a collapsed globule scales with the distance from the θ point as predicted by mean field theory, in contrast to claims in the work mentioned above. In addition to the simple-cubic lattice, we also studied two versions of the bond fluctuation model, but with much shorter chains. Finally, we show that our method can be applied also to off-lattice models, and illustrate this with simulations of a model studied in detail by Freire et al. [Macromolecules 19, 452 (1986) and later work].

  10. Dissipative particle dynamics study of translational diffusion of rigid-chain rodlike polymer in nematic phase

    NASA Astrophysics Data System (ADS)

    Zhao, Tongyang; Wang, Xiaogong

    2013-09-01

    In this study, dissipative particle dynamics (DPD) method was employed to investigate the translational diffusion of rodlike polymer in its nematic phase. The polymer chain was modeled by a rigid rod composed of consecutive DPD particles and solvent was represented by independent DPD particles. To fully understand the translational motion of the rods in the anisotropic phase, four diffusion coefficients, D_{||}u, D_ bot u, D_{||}n, D_ bot n were obtained from the DPD simulation. By definition, D_{||}n and D_ bot n denote the diffusion coefficients parallel and perpendicular to the nematic director, while D_{||}u and D_ bot u denote the diffusion coefficients parallel and perpendicular to the long axis of a rigid rod u. In the simulation, the velocity auto-correlation functions were used to calculate the corresponding diffusion coefficients from the simulated velocity of the rods. Simulation results show that the variation of orientational order caused by concentration and temperature changes has substantial influences on D_{||}u and D_ bot u. In the nematic phase, the changes of concentration and temperature will result in a change of local environment of rods, which directly influence D_{||}u and D_ bot u. Both D_{||}n and D_ bot n can be represented as averages of D_{||}u and D_ bot u, and the weighted factors are functions of the orientational order parameter S2. The effect of concentration and temperature on D_{||}n and D_ bot n demonstrated by the DPD simulation can be rationally interpreted by considering their influences on D_{||}u, D_ bot u and the order parameter S2.

  11. Synthesis and Photophysical Properties of Soluble Low-Bandgap Thienothiophene Polymers with Various Alkyl Side-Chain Lengths

    SciTech Connect

    Bae, W. J.; Scilla, C.; Duzhko, V. V.; Jo, Jang; Coughlin, E. B.

    2011-05-27

    We report the facile synthesis and characterization of a class of thienothiophene polymers with various lengths of alkyl side chains. A series of 2-alkylthieno[3,4-b]thiophene monomers (Ttx) have been synthesized in a two-step protocol in an overall yield of 28–37%. Poly(2-alkylthieno[3,4-b]thiophenes) (PTtx, alkyl: pentyl, hexyl, heptyl, octyl, and tridecyl) were synthesized by oxidative polymerization with FeCl₃ or via Grignard metathesis (GRIM) polymerization methods. The polymers are readily soluble in common organic solvents. The polymers synthesized by GRIM polymerization method (PTtx-G) have narrower molecular weight distribution (Ð) with lower molecular weight (Mn) than those synthesized by oxidative polymerization (PTtx-O). The band structures of the polymers with various lengths of alkyl side chains were investigated by UV–vis spectroscopy, cyclic voltammetry, and ultraviolet photoelectron spectroscopy. These low-bandgap polymers are good candidates for organic transistors, organic light-emitting diodes, and organic photovoltaic cells.

  12. Structure control for fine tuning fluorescence emission from side-chain azobenzene polymers.

    PubMed

    Smitha, P; Asha, S K

    2007-06-14

    New fluorescent azobenzene dyes and side-chain polymers have been synthesized and characterized and their photophysical properties studied. A series of azobenzene dyes having different fluorophores such as phenol (S1), phenylphenol (S2) and naphthol (S3) incorporated in them were synthesized. S2 had unusually high fluorescence with a quantum yield of phi f = 0.2 recorded in dichloromethane (DCM), whereas S1 and S3 were found to be weakly fluorescent. The azobenzene dyes were converted into methacrylate monomers having short ethyleneoxy spacers and then free radically polymerized. Phenylphenol-based azobenzene polymer (P2) continued to show fluorescence, whereas fluorescence was completely quenched in the case of phenol (P1)- and naphthol (P3)-based polymers. Phenylphenol, though twisted in the ground state is known to have a more planar geometry in the excited state--a factor that enables it to retain its fluorescence behavior even when it is incorporated as part of an azobenzene unit. In contrast, naphthol, which is a better fluorophore compared to phenylphenol, loses much of its emissive behavior upon coupling to the azobenzene unit. The extent of trans to cis photoisomerization in solution was very low (approximately 17%) for P2 after 30 min of continuous irradiation using 365 nm light, in contrast to approximately 40% for P1 under identical conditions. This is attributed to the steric repulsion brought about by the bulky phenylphenol units that restrict rotation. A 2-fold enhancement in fluorescence emission was observed for P2 upon irradiation by UV light at 360 nm, which relaxed to the original intensity in about 7 day's time. The higher emission of the cis azobenzenes is generally attributed to an inhibition of photoinduced electron transfer (PET) mechanism. The emission of P2 showed a concentration dependence which increased initially and then decreased in intensity with the formation of a new red-shifted peak at higher concentration due to aggregation

  13. Solution‐crystallization and related phenomena in 9,9‐dialkyl‐fluorene polymers. II. Influence of side‐chain structure

    PubMed Central

    Perevedentsev, Aleksandr; Stavrinou, Paul N.; Smith, Paul

    2015-01-01

    ABSTRACT Solution‐crystallization is studied for two polyfluorene polymers possessing different side‐chain structures. Thermal analysis and temperature‐dependent optical spectroscopy are used to clarify the nature of the crystallization process, while X‐ray diffraction and scanning electron microscopy reveal important differences in the resulting microstructures. It is shown that the planar‐zigzag chain conformation termed the β‐phase, which is observed for certain linear‐side‐chain polyfluorenes, is necessary for the formation of so‐called polymer‐solvent compounds for these polymers. Introduction of alternating fluorene repeat units with branched side‐chains prevents formation of the β‐phase conformation and results in non‐solvated, i.e. melt‐crystallization‐type, polymer crystals. Unlike non‐solvated polymer crystals, for which the chain conformation is stabilized by its incorporation into a crystalline lattice, the β‐phase conformation is stabilized by complexation with solvent molecules and, therefore, its formation does not require specific inter‐chain interactions. The presented results clarify the fundamental differences between the β‐phase and other conformational/crystalline forms of polyfluorenes. © 2015 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1492–1506 PMID:27546983

  14. Structure-property optimizations in donor polymers via electronics, substituents, and side chains toward high efficiency solar cells.

    PubMed

    Uy, Rycel L; Price, Samuel C; You, Wei

    2012-07-26

    Many advances in organic photovoltaic efficiency are not yet fully understood and new insight into structure-property relationships is required to push this technology into broad commercial use. The aim of this article is not to comprehensively review recent work, but to provide commentary on recent successes and forecast where researchers should look to enhance the efficiency of photovoltaics. By lowering the LUMO level, utilizing electron-withdrawing substituents advantageously, and employing appropriate side chains on donor polymers, researchers can elucidate further aspects of polymer-PCBM interactions while ultimately developing materials that will push past 10% efficiency.

  15. Structure and defects of a linear chain polymer film; GeO phthalocyanine epitaxially grown on KC1

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takashi; Uyeda, Natsu

    1987-10-01

    Epitaxial film of GeO phthalocyanine polymer grown on KC1 has been investigated by direct observation of molecular images and electron diffraction. The film is composed of many crystallites oriented in two directions. The mechanism of the epitaxial growth of an organic crystal has been related to the determination of a staggering angle of the molecules stacked in polymer chains. Prominent diffuse scatterings have been observed and their origin has been revealed to be the existence of stacking faults in the crystal. The molecular orientation at the fault is discussed.

  16. Quantifying chain reptation in entangled polymer melts: topological and dynamical mapping of atomistic simulation results onto the tube model.

    PubMed

    Stephanou, Pavlos S; Baig, Chunggi; Tsolou, Georgia; Mavrantzas, Vlasis G; Kröger, Martin

    2010-03-28

    The topological state of entangled polymers has been analyzed recently in terms of primitive paths which allowed obtaining reliable predictions of the static (statistical) properties of the underlying entanglement network for a number of polymer melts. Through a systematic methodology that first maps atomistic molecular dynamics (MD) trajectories onto time trajectories of primitive chains and then documents primitive chain motion in terms of a curvilinear diffusion in a tubelike region around the coarse-grained chain contour, we are extending these static approaches here even further by computing the most fundamental function of the reptation theory, namely, the probability psi(s,t) that a segment s of the primitive chain remains inside the initial tube after time t, accounting directly for contour length fluctuations and constraint release. The effective diameter of the tube is independently evaluated by observing tube constraints either on atomistic displacements or on the displacement of primitive chain segments orthogonal to the initial primitive path. Having computed the tube diameter, the tube itself around each primitive path is constructed by visiting each entanglement strand along the primitive path one after the other and approximating it by the space of a small cylinder having the same axis as the entanglement strand itself and a diameter equal to the estimated effective tube diameter. Reptation of the primitive chain longitudinally inside the effective constraining tube as well as local transverse fluctuations of the chain driven mainly from constraint release and regeneration mechanisms are evident in the simulation results; the latter causes parts of the chains to venture outside their average tube surface for certain periods of time. The computed psi(s,t) curves account directly for both of these phenomena, as well as for contour length fluctuations, since all of them are automatically captured in the atomistic simulations. Linear viscoelastic

  17. Conformational change in an isolated single synthetic polymer chain on a mica surface observed by atomic force microscopy.

    PubMed

    Kumaki, Jiro; Hashimoto, Takeji

    2003-04-23

    The random coil conformation of an isolated conventional synthetic polymer chain was clearly imaged by atomic force microscopy (AFM). The sample used was a poly(styrene)-block-poly(methyl methacrylate) diblock copolymer. A very dilute solution of the copolymer with benzene was spread on a water surface. The structure thus formed on water was subsequently transferred and deposited onto mica at various surface pressures and observed under AFM. The AFM images obtained with films deposited at a low surface pressure (<0.1 mN/m) showed a single polystyrene (PS) block chain aggregated into a single PS particle with a single poly(methyl methacrylate) (PMMA) block chain emanating from the particle. Immediately after the deposition, the single PMMA block chain aggregated to form a condensed monolayer around the polystyrene particles. However, after exposing the deposited film to highly humid air for 1 day, the PMMA chains spread out so that the single PMMA block chain could be identified as a random coil on the substrate. The thin water layer formed on the mica substrate in humid air may enable the PMMA block chain to be mobilized on the substrate, leading to the conformational rearrangement from the condensed monolayer conformation to an expanded and elongated coil. The elongation of the PMMA chain was highly sensitive to the humidity; the maximum elongation was obtained at 79% relative humidity. The elongation was a slow process and took about 20 h.

  18. Theoretical investigation of polymer chain stability in the metal coordinated azorubine and cyclam complex

    NASA Astrophysics Data System (ADS)

    Vlassa, Mihaela; Bende, Attila

    2015-08-01

    Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) coordination between azorubine and 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes using the conventional DFT and the DFT-based tight binding (DFTB) methods. Two different geometries (short and long) and spin states (singlet and triplet) of the model system built by two mesylate groups and the cyclam ring together with Ni(II) and Zn(II) ions were energetically characterized. For the Ni(II) coordination complex the triplet geometry is preferred, but one could not exclude also the presence of the singlet spin configuration due to the huge energy barrier defined by the intersystem crossing. The intersystem crossing geometry of the singlet-triplet transition was studied in details and the corresponding spin-orbit couplings were discussed. For the Zn(II) coordination complex only the singlet state was found. Polymer chain build up from four unit systems presents irregular forms with strong coordination bonds between units.

  19. Expedited Phonon Transfer in Interfacially Constrained Polymer Chain along Self-Organized Amino Acid Crystals.

    PubMed

    Mu, Liwen; Li, Yifan; Mehra, Nitin; Ji, Tuo; Zhu, Jiahua

    2017-04-05

    In this work, poly(vinyl alcohol) (PVA)/amino acid (AA) composites were prepared by a self-organized crystallization process. Five different AAs (cysteine, aspartic acid, glutamic acid, ornithine, and lysine) were selected based on their similar functional groups but different molecular structures. The different PVA-AA interactions in the five PVA/AA composites lead to two crystal patterns, i.e., continuous network (cysteine and lysine) and discrete particles (glutamic acid, ornithine, and aspartic acid). Scanning thermal microscopy is then applied to map the distribution of thermal conduction in these composites. It is found that the interface surrounding the crystals plays a dominating role in phonon transport where the polymer chains are greatly restrained by the interfacial confinement effect. Continuous crystal network builds up a continuous interface that facilitates phonon transfer while phonon scattering occurs in discrete crystalline structures. Significantly improved thermal conductivity of ∼0.7 W/m·K is observed in PVA/cysteine composite with AA loading of 8.4 wt %, which corresponds to a 170% enhancement as compared to pure PVA. The strong PVA-AA molecular interaction and self-organized crystal structure are considered the major reasons for the unique interface property and superior thermal conductivity.

  20. Antibacterial Low Molecular Weight Cationic Polymers: Dissecting the Contribution of Hydrophobicity, Chain Length and Charge to Activity.

    PubMed

    Grace, James L; Huang, Johnny X; Cheah, Soon-Ee; Truong, Nghia P; Cooper, Matthew A; Li, Jian; Davis, Thomas P; Quinn, John F; Velkov, Tony; Whittaker, Michael R

    2016-01-01

    The balance of cationicity and hydrophobicity can profoundly affect the performance of antimicrobial polymers. To this end a library of 24 cationic polymers with uniquely low degrees of polymerization was synthesized via Cu(0)-mediated polymerization, using three different cationic monomers and two initiators: providing two different hydrocarbon chain tail lengths (C2 and C12). The polymers exhibited structure-dependent antibacterial activity when tested against a selection of bacteria, viz, Staphylococcus aureus ATCC 29213, Klebsiella pneumoniae ATCC 13883, Acinetobacter baumannii ATCC 19606, and Pseudomonas aeruginosa ATCC 27853 as a representative palette of Gram-positive and Gram-negative ESKAPE pathogens. The five best-performing polymers were identified for additional testing against the polymyxin-resistant A. baumannii ATCC 19606R strain. Polymers having the lowest DP and a C12 hydrophobic tail were shown to provide the broadest antimicrobial activity against the bacteria panel studied as evidenced by lower minimum inhibitory concentrations (MICs). An optimal polymer composition was identified, and its mechanism of action investigated via membrane permeability testing against Escherichia coli. Membrane disruption was identified as the most probable mechanism for bacteria cell killing.

  1. Interphase and particle dispersion correlations in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan

    Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories

  2. Development of environmentally friendly coatings and paints using medium-chain-length poly(3-hydroxyalkanoates) as the polymer binder.

    PubMed

    van der Walle, G A; Buisman, G J; Weusthuis, R A; Eggink, G

    1999-01-01

    Unsaturated medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHAs) produced by Pseudomonas putida from linseed oil fatty acids (LOFA) and tall oil fatty acids (TOFA), were used as the polymer binder in the formulation of high solid alkyd-like paints. The relatively high concentration of unsaturated alkyl side chains incorporated into the PHA resins resulted in oxidative drying PHA paints having excellent coating properties. The homogeneously pigmented PHA coatings yielded high-gloss, smooth and strong films upon curing and showed an excellent flexibility, a good adhesion to different substrates, cohesive film properties and resistance to chipping.

  3. Crystal structures and thermodynamics/kinetics of Zn(II) coordination polymers with helical chains

    SciTech Connect

    He, Tian; Yue, Ke-Fen; Zhao, Yi-xing; Chen, San-Ping; Zhou, Chun-sheng; Yan, Ni

    2016-07-15

    Solvothermal reactions of Zn(II) acetates and four V-shaped carboxylates ligands in the presence of 1,4-Bis(2-methyl-imidazol-1-yl)butane afforded four interesting Zn(II) coordination polymers with helical chains, namely, {[Zn(bib)(atibdc)]·2H_2O}{sub n} (1), {[Zn(bib)(atbip)]·H_2O}{sub n} (2), {[Zn(bib)(2,2′-tda)]}{sub n} (3) and {[Zn(bib)(5-tbipa)]·EtOH}{sub n} (4), (H{sub 2}atibdc=5-amino-2,4,6-triiodoisophthalic acid, H{sub 2}atbip=5-amino-2,4,6-tribromoisophthalic acid, 2,2′-H{sub 2}tad=2,2′-thiodiacetic acid, 5-H{sub 2}tbipa=5-tert-butyl-isophthalic acid). 1 reveals a 3D chiral framework with three kinds of helical chains along a, b and c axis. 2 shows a 2D step-type chiral framework with right-handed helical chains. 3 displays a wavelike 2D layer network possessing alternate left- and right-handed helical chains. 4 presents a four-connected 3D framework with zigzag and meso-helical chains. The different spacers and substituent group of carboxylic acid ligands may lead to the diverse network structures of 1–4. The fluorescent properties of complexes 1−4 were studied. In addition, the thermal decompositions properties of 1–4 were investigated by simultaneous TG/DTG–DSC technique. The apparent activation energy E and the pre-exponential factor (A) of skeleton collapse for the complexes 1–4 are calculated by the integral Kissinger's method and Ozawa–Doyle's method. The activation energy E (E{sub 1}=209.658 kJ·mol{sup −1}, E{sub 2}=250.037 kJ mol{sup −1}, E{sub 3}=225.300 kJ mol{sup −1}, E{sub 4}=186.529 kJ·mol{sup −1}) demonstrates that the reaction rate of the melting decomposition is slow. The thermodynamic parameters (ΔH{sup ‡}, ΔG{sup ‡} and ΔS{sup ‡}) at the peak temperatures of the DTG curves were also calculated. ΔG{sup ‡}>0 indicates that the skeleton collapse is not spontaneous. ΔH{sub d}>0 suggests that the skeleton collapse is endothermic, corresponding to the intense endothermic peak of the DSC curve. The

  4. Dielectric properties of liquid-crystal azomethine polymer with a side alkyl-substituted chain, doped with fullerene C60

    NASA Astrophysics Data System (ADS)

    Kovalev, D. S.; Kostromin, S. V.; Musteaţa, V.; Cozan, V.; Bronnikov, S. V.

    2016-04-01

    We studied the actual and imaginary components of the dielectric constant of liquid-crystal azomethine polymer with a side chain, doped with 0.5 wt % of fullerene C60, over a wide range of temperatures and frequencies; measurements were made by means of dielectric spectroscopy. By analyzing the frequency dependence of the dielectric constant, we detected the relaxation processes (α, β1, and β2) in the nanocomposite, corresponding to certain modes of molecular motion and described them by the Arrhenius equations (β1- and β2-processes) and the Vogel-Fulcher-Tamman equation (α-process). An antiplasticization effect is discovered after doping the polymer with fullerene C60, which manifests itself in increasing the glass transition temperature of the nanocomposite compared to this parameter typical of pure polymer.

  5. Polarized optical spectroscopy applied to investigate two poly(phenylene-vinylene) polymers with different side chain structures

    NASA Astrophysics Data System (ADS)

    Pâlsson, Lars-Olof; Vaughan, Helen L.; Monkman, Andrew P.

    2006-10-01

    Two related poly(phenylene-vinylene) (PPV) light-emitting polymers have been investigated by means of polarized optical spectroscopy. The purpose of the investigation was to investigate the nature of the interactions in thin films and to examine what impact the difference in side chain structure and molecular weight in poly(2'-methoxy-5-2-ethyl-hexoxy)-1,4-phenylene vinylene (MEH-PPV) and poly(2-(3',7'-dimethyloctyloxy)-5-methoxy-1,4-phenylene-vinylene) (OC1C10-PPV) has on the electronic and optical properties of the two polymers. Aligning the polymers by dispersing them in anisotropic solvents and stretched films shows that the side chains have an impact on the relative orientations of the transition dipole moments. In anisotropic solvents the linear dichroism is larger for MEH-PPV than for the related polymer OC1C10-PPV, while in stretched films the opposite situation prevails. A lower polarization of the luminescence from OC1C10-PPV, relative to MEH-PPV, was also obtained independent of alignment medium used. The data therefore suggest that while mechanical stretching may align the OC1C10-PPV to a greater degree, the emitting species is distinct from the absorbing species. The circular dichroism (CD) spectra of both polymers undergo dramatic changes when the liquid phase and the solid state (film) are compared. The solution CD spectra shows no evidence of interchain interactions; instead the spectra of both systems indicate a helical conformation of the polymers. The CD spectra of films are dramatically different with the strong Cotton effect being observed. This points to the formation of an aggregate in the film, with an associated ground state interaction, an interchain species such as a physical dimer, or a more complex higher aggregate.

  6. Amide side chain amphiphilic polymers disrupt surface established bacterial bio-films and protect mice from chronic Acinetobacter baumannii infection.

    PubMed

    Uppu, Divakara S S M; Samaddar, Sandip; Ghosh, Chandradhish; Paramanandham, Krishnamoorthy; Shome, Bibek R; Haldar, Jayanta

    2016-01-01

    Bacterial biofilms represent the root-cause of chronic or persistent infections in humans. Gram-negative bacterial infections due to nosocomial and opportunistic pathogens such as Acinetobacter baumannii are more difficult to treat because of their inherent and rapidly acquiring resistance to antibiotics. Due to biofilm formation, A. baumannii has been noted for its apparent ability to survive on artificial surfaces for an extended period of time, therefore allowing it to persist in the hospital environment. Here we report, maleic anhydride based novel cationic polymers appended with amide side chains that disrupt surface established multi-drug resistant A. baumannii biofilms. More importantly, these polymers significantly (p < 0.0001) decrease the bacterial burden in mice with chronic A. baumannii burn wound infection. The polymers also show potent antibacterial efficacy against methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococci (VRE) and multi-drug resistant clinical isolates of A. baumannii with minimal toxicity to mammalian cells. We observe that optimal hydrophobicity dependent on the side chain chemical structure of these polymers dictate the selective toxicity to bacteria. Polymers interact with the bacterial cell membranes by causing membrane depolarization, permeabilization and energy depletion. Bacteria develop rapid resistance to erythromycin and colistin whereas no detectable development of resistance occurs against these polymers even after several passages. These results suggest the potential use of these polymeric biomaterials in disinfecting biomedical device surfaces after the infection has become established and also for the topical treatment of chronic bacterial infections.

  7. Biomedical applications of polymers derived by reversible addition - fragmentation chain-transfer (RAFT).

    PubMed

    Fairbanks, Benjamin D; Gunatillake, Pathiraja A; Meagher, Laurence

    2015-08-30

    RAFT- mediated polymerization, providing control over polymer length and architecture as well as facilitating post polymerization modification of end groups, has been applied to virtually every facet of biomedical materials research. RAFT polymers have seen particularly extensive use in drug delivery research. Facile generation of functional and telechelic polymers permits straightforward conjugation to many therapeutic compounds while synthesis of amphiphilic block copolymers via RAFT allows for the generation of self-assembled structures capable of carrying therapeutic payloads. With the large and growing body of literature employing RAFT polymers as drug delivery aids and vehicles, concern over the potential toxicity of RAFT derived polymers has been raised. While literature exploring this complication is relatively limited, the emerging consensus may be summed up in three parts: toxicity of polymers generated with dithiobenzoate RAFT agents is observed at high concentrations but not with polymers generated with trithiocarbonate RAFT agents; even for polymers generated with dithiobenzoate RAFT agents, most reported applications call for concentrations well below the toxicity threshold; and RAFT end-groups may be easily removed via any of a variety of techniques that leave the polymer with no intrinsic toxicity attributable to the mechanism of polymerization. The low toxicity of RAFT-derived polymers and the ability to remove end groups via straightforward and scalable processes make RAFT technology a valuable tool for practically any application in which a polymer of defined molecular weight and architecture is desired.

  8. Enhancing the specificity of polymerase chain reaction by graphene oxide through surface modification: zwitterionic polymer is superior to other polymers with different charges.

    PubMed

    Zhong, Yong; Huang, Lihong; Zhang, Zhisen; Xiong, Yunjing; Sun, Liping; Weng, Jian

    Graphene oxides (GOs) with different surface characteristics, such as size, reduction degree and charge, are prepared, and their effects on the specificity of polymerase chain reaction (PCR) are investigated. In this study, we demonstrate that GO with a large size and high reduction degree is superior to small and nonreduced GO in enhancing the specificity of PCR. Negatively charged polyacrylic acid (PAA), positively charged polyacrylamide (PAM), neutral polyethylene glycol (PEG) and zwitterionic polymer poly(sulfobetaine) (pSB) are used to modify GO. The PCR specificity-enhancing ability increases in the following order: GO-PAA < GO-PAM < GO-PEG < GO-pSB. Thus, zwitterionic polymer-modified GO is superior to other GO derivatives with different charges in enhancing the specificity of PCR. GO derivatives are also successfully used to enhance the specificity of PCR for the amplification of human mitochondrial DNA using blood genomic DNA as template. Molecular dynamics simulations and molecular docking are performed to elucidate the interaction between the polymers and Pfu DNA polymerase. Our data demonstrate that the size, reduction degree and surface charge of GO affect the specificity of PCR. Based on our results, zwitterionic polymer-modified GO may be used as an efficient additive for enhancing the specificity of PCR.

  9. Enhancing the specificity of polymerase chain reaction by graphene oxide through surface modification: zwitterionic polymer is superior to other polymers with different charges

    PubMed Central

    Zhong, Yong; Huang, Lihong; Zhang, Zhisen; Xiong, Yunjing; Sun, Liping; Weng, Jian

    2016-01-01

    Graphene oxides (GOs) with different surface characteristics, such as size, reduction degree and charge, are prepared, and their effects on the specificity of polymerase chain reaction (PCR) are investigated. In this study, we demonstrate that GO with a large size and high reduction degree is superior to small and nonreduced GO in enhancing the specificity of PCR. Negatively charged polyacrylic acid (PAA), positively charged polyacrylamide (PAM), neutral polyethylene glycol (PEG) and zwitterionic polymer poly(sulfobetaine) (pSB) are used to modify GO. The PCR specificity-enhancing ability increases in the following order: GO-PAA < GO-PAM < GO-PEG < GO-pSB. Thus, zwitterionic polymer-modified GO is superior to other GO derivatives with different charges in enhancing the specificity of PCR. GO derivatives are also successfully used to enhance the specificity of PCR for the amplification of human mitochondrial DNA using blood genomic DNA as template. Molecular dynamics simulations and molecular docking are performed to elucidate the interaction between the polymers and Pfu DNA polymerase. Our data demonstrate that the size, reduction degree and surface charge of GO affect the specificity of PCR. Based on our results, zwitterionic polymer-modified GO may be used as an efficient additive for enhancing the specificity of PCR. PMID:27956830

  10. Phase separation of a Lennard-Jones fluid interacting with a long, condensed polymer chain: implications for the nuclear body formation near chromosomes.

    PubMed

    Oh, Inrok; Choi, Saehyun; Jung, YounJoon; Kim, Jun Soo

    2015-08-28

    Phase separation in a biological cell nucleus occurs in a heterogeneous environment filled with a high density of chromatins and thus it is inevitably influenced by interactions with chromatins. As a model system of nuclear body formation in a cell nucleus filled with chromatins, we simulate the phase separation of a low-density Lennard-Jones (LJ) fluid interacting with a long, condensed polymer chain. The influence of the density variation of LJ particles above and below the phase boundary and the role of attractive interactions between LJ particles and polymer segments are investigated at a fixed value of strong self-interaction between LJ particles. For a density of LJ particles above the phase boundary, phase separation occurs and a dense domain of LJ particles forms irrespective of interactions with the condensed polymer chain whereas its localization relative to the polymer chain is determined by the LJ-polymer attraction strength. Especially, in the case of moderately weak attractions, the domain forms separately from the polymer chain and subsequently associates with the polymer chain. When the density is below the phase boundary, however, the formation of a dense domain is possible only when the LJ-polymer attraction is strong enough, for which the domain grows in direct contact with the interacting polymer chain. In this work, different growth behaviors of LJ particles result from the differences in the density of LJ particles and in the LJ-polymer interaction, and this work suggests that the distinct formation of activity-dependent and activity-independent nuclear bodies (NBs) in a cell nucleus may originate from the differences in the concentrations of body-specific NB components and in their interaction with chromatins.

  11. Oligo(ethylene glycol)-incorporated hybrid linear alkyl side chains for n-channel polymer semiconductors and their effect on the thin-film crystalline structure.

    PubMed

    Kim, Ran; Kang, Boseok; Sin, Dong Hun; Choi, Hyun Ho; Kwon, Soon-Ki; Kim, Yun-Hi; Cho, Kilwon

    2015-01-28

    Oligo(ethylene glycol)-incorporated hybrid linear alkyl side chains, serving as solubilizing groups, are designed and introduced into naphthalene-diimide-based n-channel copolymers. The synthesized polymers exhibit unipolar n-type operation with an electron mobility of up to 1.64 cm(2) V(-1) s(-1), which demonstrates the usefulness of the hybrid side chains in polymer electronics applications.

  12. Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase

    SciTech Connect

    Walba,D.; Yang, H.; Shoemaker, R.; Keller, P.; Shao, r.; Coleman, D.; Jones, C.; Nakata, M.; Clark, N.

    2006-01-01

    The synthesis and characterization of a main-chain smectic liquid-crystalline polymer system designed for development into electromechanical actuators is described. The chemical structure is chosen to provide a large electroclinic effect in the SmA* phase, with large concomitant layer shrinkage (a rare combination). The polymers are prepared by acyclic diene metathesis polymerization (ADMET) of liquid-crystalline ,-dienes. Oligomers with a degree of polymerization of {approx}10-30 are obtained using Grubbs first-generation catalyst, while oligomers with a degree of polymerization of {approx}200 are obtained using Grubbs second-generation catalyst. All polymer samples show the following phase sequence: I - SmA* - SmC* - Glass. X-ray analysis of polymer powder samples demonstrates the desired layer shrinkage at the SmA* - SmC* transition. The polymers form well-aligned fibers by pulling from the isotropic melt, and X-ray analysis of fibers in the SmA* phase shows that in the bulk of the fiber the layers are oriented perpendicular to the fiber axis, while at the surfaces there appears to be a thin sheath where the layers are parallel to the fiber/air interface. The desired layer shrinkage with tilt at the SmA* - SmC* transition in these fibers is seen as well, and in the SmC* phase the fibers exhibit an interesting conical chevron layer structure. Electro-optic investigation of aligned thin films of the polymer, prepared from quenched fiber glasses using a novel technique, exhibit a large electroclinic effect, with substantial degradation of alignment quality upon field-induced tilt. This degradation in alignment quality, coupled with the layer shrinkage at the SmA* - SmC* transition demonstrated by X-ray scattering, strongly suggests the desired layer shrinkage with electroclinic tilt is in fact occurring in the polymer films.

  13. Side-Chain Fluorination: An Effective Approach to Achieving High-Performance All-Polymer Solar Cells with Efficiency Exceeding 7.

    PubMed

    Oh, Jiho; Kranthiraja, Kakaraparthi; Lee, Changyeon; Gunasekar, Kumarasamy; Kim, Seonha; Ma, Biwu; Kim, Bumjoon J; Jin, Sung-Ho

    2016-12-01

    Side-chain fluorination of polymers is demonstrated as a highly effective strategy to improve the efficiency of all-polymer solar cells from 2.93% (nonfluorinated P1) to 7.13% (fluorinated P2). This significant enhancement is achieved by synergistic improvements in open-circuit voltage, charge generation, and charge transport, as fluorination of the donor polymer optimizes the band alignment and the film morphology.

  14. Large Optoelectronic Enhancement of Light-Harvesting Polymers by Chain Confinement and Charge Percolation for LEDs and Photocells Based on Ultrathin Films and CNT Nanocomposites

    DTIC Science & Technology

    2010-09-30

    methanol and dried in a vacuum. Polymer solar cells using ITO ( Indium tin oxide) as an anode and LiF/Al as a cathode were prepared according to the...TERMS Conductive Polymers, nano photonics, Solar Cells 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF...chains, polymer molecules are intrinsically much softer than the inorganic crystalline counterparts, such as silicon and gallium oxide. Hence self

  15. Effect of cationic side-chains on intracellular delivery and cytotoxicity of pH sensitive polymer-doxorubicin nanocarriers

    NASA Astrophysics Data System (ADS)

    Fang, Chen; Kievit, Forrest M.; Cho, Yong-Chan; Mok, Hyejung; Press, Oliver W.; Zhang, Miqin

    2012-10-01

    Fine-tuning the design of polymer-doxorubicin conjugates permits optimization of an efficient nanocarrier to greatly increase intracellular uptake and cytotoxicity. Here, we report synthesis of a family of self-assembled polymer-doxorubicin nanoparticles and an evaluation of the effects of various types of side-chains on intracellular uptake and cytotoxicity of the nanocarriers for lymphoma cells. Monomers with three different cationic side-chains (CA) and pKa's, i.e., a guanidinium group (Ag), an imidazole group (Im), and a tertiary amine group (Dm), were comparatively investigated. The cationic monomer, poly(ethylene glycol) (PEG), and doxorubicin (Dox) were reacted with 1,4-(butanediol) diacrylate (BUDA) to prepare a poly(β-amino ester) (PBAE) polymer via Michael addition. All three polymer-Dox conjugates spontaneously formed nanoparticles (NP) through hydrophobic interactions between doxorubicin in aqueous solution, resulting in NP-Im/Dox, NP-Ag/Dox, and NP-Dm/Dox, with hydrodynamic sizes below 80 nm. Doxorubicin was linked to all 3 types of NPs with a hydrazone bond to assure selective release of doxorubicin only at acidic pH, as it occurs in the tumor microenvironment. Both NP-Im/Dox and NP-Ag/Dox exhibited much higher intracellular uptake by Ramos cells (Burkitt's lymphoma) than NP-Dm/Dox, suggesting that the type of side chain in the NPs determines the extent of intracellular uptake. As a result, NP-Im/Dox and NP-Ag/Dox showed cytotoxicity that was comparable to free Dox in vitro. Our findings suggest that the nature of surface cationic group on nanocarriers may profoundly influence their intracellular trafficking and resulting therapeutic efficacy. Thus, it is a crucial factor to be considered in the design of novel carriers for intracellular drug delivery.

  16. Identification of polymer surface adsorbed proteins implicated in pluripotent human embryonic stem cell expansion† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6bm00214e Click here for additional data file.

    PubMed Central

    Hammad, Moamen; Rao, Wei; Smith, James G. W.; Anderson, Daniel G.; Langer, Robert; Young, Lorraine E.; Barrett, David A.; Davies, Martyn C.; Denning, Chris

    2016-01-01

    Improved biomaterials are required for application in regenerative medicine, biosensing, and as medical devices. The response of cells to the chemistry of polymers cultured in media is generally regarded as being dominated by proteins adsorbed to the surface. Here we use mass spectrometry to identify proteins adsorbed from a complex mouse embryonic fibroblast (MEF) conditioned medium found to support pluripotent human embryonic stem cell (hESC) expansion on a plasma etched tissue culture polystyrene surface. A total of 71 proteins were identified, of which 14 uniquely correlated with the surface on which pluripotent stem cell expansion was achieved. We have developed a microarray combinatorial protein spotting approach to test the potential of these 14 proteins to support expansion of a hESC cell line (HUES-7) and a human induced pluripotent stem cell line (ReBl-PAT) on a novel polymer (N-(4-Hydroxyphenyl) methacrylamide). These proteins were spotted to form a primary array yielding several protein mixture ‘hits’ that enhanced cell attachment to the polymer. A second array was generated to test the function of a refined set of protein mixtures. We found that a combination of heat shock protein 90 and heat shock protein-1 encourage elevated adherence of pluripotent stem cells at a level comparable to fibronectin pre-treatment. PMID:27466628

  17. Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization in Undergraduate Polymer Science Lab

    ERIC Educational Resources Information Center

    Nguyen, T. L. U.; Bennet, Francesca; Stenzel, Martina H.; Barner-Kowollik, Christopher

    2008-01-01

    This 8-hour experiment (spread over two 4-hour sessions) is designed to equip students with essential skills in polymer synthesis, particularly in synthesizing polymers of well-defined molecular weight. The experiment involves the synthesis and characterization of poly(vinyl neodecanoate) via living free radical polymerization, specifically the…

  18. Driven polymer translocation through a cylindrical nanochannel: interplay between the channel length and the chain length

    NASA Astrophysics Data System (ADS)

    Yong, Huaisong; Wang, Yilin; Yuan, Shichen; Xu, Bi; Luo, Kaifu

    Using analytical techniques and Langevin dynamics simulations, we investigate the dynamics of polymer translocation through a nanochannel embedded in two dimensions under an applied external field. We examine the translocation time for various ratio of the channel length $L$ to the polymer length $N$. For short channels $L\\ll N$, the translocation time $\\tau \\sim N^{1+\

  19. Surface segregation of fluorinated moieties on random copolymer films controlled by random-coil conformation of polymer chains in solution.

    PubMed

    Xue, Dongwu; Wang, Xinping; Ni, Huagang; Zhang, Wei; Xue, Gi

    2009-02-17

    The relationship between solution properties, film-forming methods, and the solid surface structures of random copolymers composed of butyl methacrylate and dodecafluorheptyl methylacrylate (DFHMA) was investigated by contact angle measurements, X-ray photoelectron spectroscopy, sum frequency generation vibrational spectroscopy, and surface tension measurements. The results, based on thermodynamic considerations, demonstrated that the random copolymer chain conformation at the solution/air interface greatly affected the surface structure of the resulting film, thereby determining the surface segregation of fluorinated moieties on films obtained by various film-forming techniques. When the fluorinated monomer content of the copolymer solution was low, entropic forces dominated the interfacial structure, with the perfluoroalkyl groups unable to migrate to the solution/air interface and thus becoming buried in a random-coil chain conformation. When employing this copolymer solution for film preparation by spin-coating, the copolymer chains in solution were likely extended due to centrifugal forces, thereby weakening the entropy effect of the polymer chains. Consequently, this resulted in the segregation of the fluorinated moieties on the film surface. For the films prepared by casting, the perfluoroalkyl groups were, similar to those in solution, incapable of segregating at the film surface and were thus buried in the random-coil chains. When the copolymers contained a high content of DFHMA, the migration of perfluoroalkyl groups at the solution/air interface was controlled by enthalpic forces, and the perfluoroalkyl groups segregated at the surface of the film regardless of the film-forming technique. The aim of the present work was to obtain an enhanced understanding of the formation mechanism of the chemical structure on the surface of the polymer film, while demonstrating that film-forming methods may be used in practice to promote the segregation of fluorinated

  20. Solvent Polarity Effect on Chain Conformation, Film Morphology, and Optical Properties of a Water-Soluble Conjugated Polymer

    SciTech Connect

    Xu, Zhihua; Tsai, Hsinhan; Wang, Hsing-Lin; Cotlet, Mircea

    2010-09-16

    The solvent polarity effect on chain conformation, film morphology, and photophysical properties of a nonionic water-soluble conjugated polymer (WSCP), poly[2,5-bis(diethylaminetetraethylene glycol)phenylene vinylene] (DEATG-PPV) is investigated in detail. The combination of stationary absorption and photoluminescence (PL) spectroscopy, time-resolved PL spectroscopy, and fluorescence correlation spectroscopy methods enables us to probe the chain conformation of DEATG-PPV, down to the level of a single chain when working with extremely diluted solutions. The use of correlated atomic force microscopy and confocal fluorescence lifetime imaging microscopy measurements of drop-casted DEATG-PPV films reveals the intrinsic relationship between chain conformation, film morphology, and optical properties. Depending on solvent polarity, DEATG-PPV presents extended, coiled, and collapsed chain conformations in solutions, which lead to distinct morphology and optical properties in solid films. Our work presents a pathway to control and characterize the film morphologies of WSCPs toward the optimal performance of various optoelectronic devices.

  1. XLPE based Al2O3-clay binary and ternary hybrid nanocomposites: self-assembly of nanoscale hybrid fillers, polymer chain confinement and transport characteristics.

    PubMed

    Jose, Josmin P; Thomas, Sabu

    2014-10-07

    Transport properties of hybrid nanoparticle based cross-linked polyethylene (XLPE)-Al2O3-clay binary and ternary nanocomposites have been investigated with special significance to the hybrid effect and synergism of hybrid nanofillers. Compiling the temperature and filler effects demonstrates the self-assembly of hybrid nanofillers in confining the polymer chain dynamics. Studies on transport mechanisms, transport coefficients, and swelling parameters confirm the superior solvent resistant properties of hybrid filler reinforced nanocomposites. Experiments confirmed the extra stability of the ternary hybrid nanocomposites against the process of solvent penetration. Thermodynamic and kinetic investigations reveal that the nanofillers are competent to alter the thermodynamic feasibility and rate constant parameters. Theoretical predictions by the Peppas-Sahlin model suggest that the diffusion process is well thought-out to be a combination of diffusion into the swollen polymer and the polymer chain relaxation process. The morphology and the network density estimation confirm the presence of filler networks and the trapped polymer chains inside them, in ternary systems, which elucidate the microstructure assisted solvent resistant properties of the ternary hybrid nanocomposites. The amount of polymer chains immobilized by the filler surface was computed from dynamic mechanical analysis and a nice correlation was established between transport characteristics and the polymer chain confinement.

  2. A multi-chain polymer slip-spring model with fluctuating number of entanglements: Density fluctuations, confinement, and phase separation.

    PubMed

    Ramírez-Hernández, Abelardo; Peters, Brandon L; Schneider, Ludwig; Andreev, Marat; Schieber, Jay D; Müller, Marcus; de Pablo, Juan J

    2017-01-07

    Coarse grained simulation approaches provide powerful tools for the prediction of the equilibrium properties of polymeric systems. Recent efforts have sought to develop coarse-graining strategies capable of predicting the non-equilibrium behavior of entangled polymeric materials. Slip-link and slip-spring models, in particular, have been shown to be capable of reproducing several key aspects of the linear response and rheology of polymer melts. In this work, we extend a previously proposed multi-chain slip-spring model in a way that correctly incorporates the effects of the fluctuating environment in which polymer segments are immersed. The model is used to obtain the equation of state associated with the slip-springs, and the results are compared to those of related numerical approaches and an approximate analytical expression. The model is also used to examine a polymer melt confined into a thin film, where an inhomogeneous distribution of polymer segments is observed, and the corresponding inhomogeneities associated with density fluctuations are reflected on the spatial slip-spring distribution.

  3. Functionalization at the central position of vinyl polymer chains: highly associable multipoint hydrogen bonds for complementary self-assemblies.

    PubMed

    Lee, Sang-Ho; Ouchi, Makoto; Sawamoto, Mitsuo

    2014-02-01

    This paper deals with the precision introduction of a multiple hydrogen-bonding site of a high association constant at the central position of a vinyl polymer chain for complementary self-assemblies. The interactive site consists of an array of hydrogen donors (D) and acceptors (A) to induce a multiple and highly associable interaction with a complementary counterpart. A bifunctional initiator (Cl-DADDAD-Cl) for metal-catalyzed living radical polymerization is thus designed and synthesized to embed a "Hamilton receptor" (DADDAD) between two terminal chlorides (Cl). In the presence of a ruthenium complex, the dichloride gives controlled polymers (Cl∼∼∼DADDAD∼∼∼Cl, ∼ ∼ ∼: polymer backbone) of narrow molecular weight distributions (Mw/Mn < 1.2) from common monomers such as styrene and methyl methacrylate (MMA). The receptor-decorated polystyrene recognizes complementary associable molecules and polymers carrying an ADADA unit (ADADA-Anthracene and ADADA-PMMA) to form self-assemblies where the association constant is as high as K(ass) ≈ 8000 m(-1).

  4. Thermodynamics of polymer nematics described with a worm-like chain model: particle-based simulations and SCF theory calculations

    NASA Astrophysics Data System (ADS)

    Greco, Cristina; Yiang, Ying; Kremer, Kurt; Chen, Jeff; Daoulas, Kostas

    Polymer liquid crystals, apart from traditional applications as high strength materials, are important for new technologies, e.g. Organic Electronics. Their studies often invoke mesoscale models, parameterized to reproduce thermodynamic properties of the real material. Such top-down strategies require advanced simulation techniques, predicting accurately the thermodynamics of mesoscale models as a function of characteristic features and parameters. Here a recently developed model describing nematic polymers as worm-like chains interacting with soft directional potentials is considered. We present a special thermodynamic integration scheme delivering free energies in particle-based Monte Carlo simulations of this model, avoiding thermodynamic singularities. Conformational and structural properties, as well as Helmholtz free energies are reported as a function of interaction strength. They are compared with state-of-art SCF calculations invoking a continuum analog of the same model, demonstrating the role of liquid-packing and fluctuations.

  5. A Comprehensive study of the Effects of Chain Morphology on the Transport Properties of Amorphous Polymer Films

    NASA Astrophysics Data System (ADS)

    Mendels, Dan; Tessler, Nir

    2016-07-01

    Organic semiconductors constitute one of the main components underlying present-day paradigm shifting optoelectronic applications. Among them, polymer based semiconductors are deemed particularly favorable due to their natural compatibility with low-cost device fabrication techniques. In light of recent advances in the syntheses of these classes of materials, yielding systems exhibiting charge mobilities comparable with those found in organic crystals, a comprehensive study of their charge transport properties is presented. Among a plethora of effects arising from these systems morphological and non morphological attributes, it is shown that a favorable presence of several of these attributes, including that of rapid on-chain carrier propagation and the presence of elongated conjugation segments, can lead to an enhancement of the system’s mobility by more than 5 orders of magnitude with respect to ‘standard’ amorphous organic semiconductors. New insight for the formulation of new engineering strategies for next generation polymer based semiconductors is thus gathered.

  6. A Comprehensive study of the Effects of Chain Morphology on the Transport Properties of Amorphous Polymer Films

    PubMed Central

    Mendels, Dan; Tessler, Nir

    2016-01-01

    Organic semiconductors constitute one of the main components underlying present-day paradigm shifting optoelectronic applications. Among them, polymer based semiconductors are deemed particularly favorable due to their natural compatibility with low-cost device fabrication techniques. In light of recent advances in the syntheses of these classes of materials, yielding systems exhibiting charge mobilities comparable with those found in organic crystals, a comprehensive study of their charge transport properties is presented. Among a plethora of effects arising from these systems morphological and non morphological attributes, it is shown that a favorable presence of several of these attributes, including that of rapid on-chain carrier propagation and the presence of elongated conjugation segments, can lead to an enhancement of the system’s mobility by more than 5 orders of magnitude with respect to ‘standard’ amorphous organic semiconductors. New insight for the formulation of new engineering strategies for next generation polymer based semiconductors is thus gathered. PMID:27405103

  7. Adhesive ability of a heat-resistant double-chain polymer and the strength of CFRP based on it

    NASA Astrophysics Data System (ADS)

    Gorbatkina, Yu. A.; Ivanova-Mumjieva, V. G.; Kuperman, A. M.; Ponomarev, I. I.; Sidorenko, V. I.

    2008-07-01

    The adhesive ability of a heat-resistant polyiminoquinazolindione (PIQD) binder, based on a double-chain polymer, and the physicomechanical characteristics of unidirectional CFRPs made with it are investigated. It is shown that, at room temperature, the strength of model adhesive joints (PIQD-steel wire) and of the CFRPs in shear and bending is rather low — about half of that of similar specimens based on an epoxy binder. At the same time, all their mechanical characteristics, to a large measure (50%), are retained at temperatures up to 450°C, which considerably exceeds the heat resistance of all polymer matrices used at the present time. The elastic modulus of the CFRPs in bending practically remains the same up to 450°C.

  8. Highly efficient stabilisation of meta-ethynylpyridine polymers with amide side chains in water by coordination of rare-earth metals.

    PubMed

    Makida, Hiroki; Abe, Hajime; Inouye, Masahiko

    2015-02-14

    An amphiphilic meta-ethynylpyridine polymer with chiral amide side chains was developed. The polymer was prepared by sequential Sonogashira reactions, and the product was soluble in polar and apolar solvents. The additive effects of metal salts on the polymer were examined in water and aqueous EtOH on the basis of UV-vis and CD spectra. The enhancement of the positive Cotton effect and hypochromism around 360 nm occurred by the addition of various metal salts, indicating the coordination of the cations to the amide side chains of the polymer to stabilise the helical structure. Among them, rare-earth metal salts, especially Sc(OTf)3 showed more efficient additive effects probably because of its strong coordination ability even in water. Positive cooperativity was observed for the coordination of Sc(OTf)3 to the polymer in aqueous EtOH.

  9. Determination of oligomeric chain length distributions at surfaces using ToF-SIMS: segregation effects and polymer properties

    NASA Astrophysics Data System (ADS)

    Gardella, Joseph A.; Mahoney, Christine M.

    2004-06-01

    While many XPS and SIMS studies of polymers have detected and quantified segregation of low surface energy blocks or components in copolymers and polymer blends [D. Briggs, in: D.R. Clarke, S. Suresh, I.M. Ward (Eds.), Surface Analysis of Polymers by XPS and Static SIMS, Cambridge University Press, Cambridge, 1998 (Chapter 5).], this paper reports ToF-SIMS studies of direct measurement of the segment length distribution at the surface of siloxane copolymers. These data allow insight into the segregation of particular portions of the oligomeric distribution; specifically, in this study, longer PDMS oligomers segregated at the expense of shorter PDMS chains. We have reported XPS analysis of competitive segregation effects for short PDMS chains [Macromolecules 35 (13) (2002) 5256]. In this study, a series of poly(ureaurethane)-poly(dimethylsiloxane) (PUU-PDMS) copolymers have been synthesized containing varying ratios of G-3 and G-9 (G- X describes the average segment length of the PDMS added), while maintaining a constant overall siloxane weight percentage (10, 30, and 60%). These copolymers were utilized as model systems to study the preferential segregation of certain siloxane segment lengths to the surface over others. ToF-SIMS analysis of PUU-PDMS copolymers has yielded high-mass range copolymer fragmentation patterns containing intact PDMS segments. For the first time, this information is utilized to determine PDMS segment length distributions at the copolymer surface as compared to the bulk. The results show that longer siloxane segment lengths are preferentially segregating to the surface over shorter chain lengths. These results also show the importance of ToF-SIMS and mass spectrometry in the development of new materials containing low molecular weight amino-propyl-terminated siloxanes.

  10. Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

    NASA Astrophysics Data System (ADS)

    Streltsov, S. V.; Petrova, M. V.; Morozov, V. A.; Romanenko, G. V.; Anisimov, V. I.; Lukzen, N. N.

    2013-01-01

    The chain-polymer Cu(II) “breathing crystals” C21H19CuF12N4O6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T=146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.

  11. Mechanically durable and highly conductive elastomeric composites from long single-walled carbon nanotubes mimicking the chain structure of polymers.

    PubMed

    Ata, Seisuke; Kobashi, Kazufumi; Yumura, Motoo; Hata, Kenji

    2012-06-13

    By using long single-walled carbon nanotubes (SWNTs) as a filler possessing the highest aspect ratio and small diameter, we mimicked the chain structure of polymers in the matrix and realized a highly conductive elastomeric composite (30 S/cm) with an excellent mechanical durability (4500 strain cycles until failure), far superior to any other reported conductive elastomers. This exceptional mechanical durability was explained by the ability of long and traversing SWNTs to deform in concert with the elastomer with minimum stress concentration at their interfaces. The conductivity was sufficient to operate many active electronics components, and thus this material would be useful for practical stretchable electronic devices.

  12. Reversible Thermal Stiffening in Polymer Nanocomposites.

    PubMed

    Senses, Erkan; Isherwood, Andrew; Akcora, Pinar

    2015-07-15

    Miscible polymer blends with different glass transition temperatures (Tg) are known to create confined interphases between glassy and mobile chains. Here, we show that nanoparticles adsorbed with a high-Tg polymer, poly(methyl methacrylate), and dispersed in a low-Tg matrix polymer, poly(ethylene oxide), exhibit a liquid-to-solid transition at temperatures above Tg's of both polymers. The mechanical adaptivity of nanocomposites to temperature underlies the existence of dynamically asymmetric bound layers on nanoparticles and more importantly reveals their impact on macroscopic mechanical response of composites. The unusual reversible stiffening behavior sets these materials apart from conventional polymer composites that soften upon heating. The presented stiffening mechanism in polymer nanocomposites can be used in applications for flexible electronics or mechanically induced actuators responding to environmental changes like temperature or magnetic fields.

  13. Novel non-conjugated main-chain hole-transporting polymers for organic electronics application.

    PubMed

    Schelter, Jürgen; Mielke, Georg Felix; Köhnen, Anne; Wies, Jenna; Köber, Sebastian; Nuyken, Oskar; Meerholz, Klaus

    2010-09-01

    A new class of hole-transporting polymers for use in organic electronic devices such as organic light-emitting diodes (OLEDs) or photorefractive holographic storage devices has been synthesized. The polymers contain tetraarylbenzidines or tetraarylphenylenediamines as charge-transporting units in the polymer backbone and are connected by non-conjugating fluorene bridges. For use in OLEDs the novel polymers were functionalized with oxetane groups that can be cross-linked via a cationic ring opening polymerization to yield insoluble networks. Such insoluble films are necessary for the fabrication of multilayer devices by wet deposition techniques. The novel materials feature improved film-formation properties as demonstrated in green-emitting double-layer OLEDs.

  14. Effects of shear flow on reactive coupling of polymer chains at melt interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbin; Lodge, Timothy; Macosko, Christopher

    2006-03-01

    The coupling reaction of functional polymers at static polymer-polymer interfaces is typically much slower than that at interfaces formed during mixing (see, for example, Reference 1). We have demonstrated that the imposed simple shear can accelerate coupling reactions at flat interfaces. For amine-terminal polystyrene (PS-NH2)/anhydride terminal poly(methyl methacrylate) (PMMA-anh), the PMMA-anh conversion under dynamic oscillation even at strain amplitude as small as 1% is seven times that under static conditions. Reaction time and temperature and the total interfacial area were maintained the same. Similar behavior was found for both bilayer and multilayer samples. Under steady simple shear, the reaction conversion and the rate of interfacial area generation are comparable to that of batch mixing. *Macosko, C. W.; Jeon. H. K.; Hoye, T. R. Prog. Polym. Sci. 2005, 30, 939.

  15. Study of Transport Properties and Structure of Extended-Chain Polymers.

    DTIC Science & Technology

    1985-09-01

    almost unavoidable consequences of the synthesis methods and processing conditions. Clearly a will be influenced by such variables. For example, the...and vapor diffusion D of polymers has been done on thin films of extruded or r molded thermoplastics and elastomers . Although some stu- dies have...polymeric systems and concluded that electronic conductions exist in s-me polymers such as polyacrylonitrile and polyamides . However, a very large

  16. Photoinduced changes of surface order in coumarin side-chain polymer films used for liquid crystal photoalignment

    SciTech Connect

    Bergmann, G.; Jackson, P.O.; Hogg, J.H.C.; Stirner, T.; O'Neill, M.; Duffy, W.L.; Kelly, S.M.; Clark, G.F.

    2005-08-08

    Specular x-ray reflectivity probes morphological changes in a crosslinkable coumarin photoalignment polymer film resulting from ultraviolet irradiation. An ordered surface layer with density oscillations compatible with planar side-chain alignment is obtained before irradiation. The ordering is enhanced in the early stages of crosslinking. This is attributed to the photoinduced increase of mobility of the side-chains resulting from the creation of free volume by the crosslinking process. The expansion of the thin film confirms that free volume is created. The surface ordering decreases with prolonged ultraviolet irradiation because of increased material viscosity resulting from a high crosslinked density. The implications of surface ordering on liquid crystal photoalignment are discussed.

  17. A two-dimensional iron(II) carboxylate linear chain polymer that exhibits a metamagnetic spin-canted antiferromagnetic to single-chain magnetic transition.

    PubMed

    Zheng, Yan-Zhen; Xue, Wei; Tong, Ming-Liang; Chen, Xiao-Ming; Grandjean, Fernande; Long, Gary J

    2008-05-19

    A two-dimensional iron(II) carboxylate coordination polymer, [Fe(pyoa)2]infinity, where pyoa is 2-(pyridin-3-yloxy)acetate, has been prepared by hydrothermal synthesis. Its crystal structure reveals a single iron(II) site with an elongated octahedral coordination environment containing four equatorial carboxylate oxygens and two axial pyridyl nitrogens; the iron(II) sites are linked by syn-anti micro-carboxylates to form chains along the b axis that have an Fe...Fe separation of 4.910 A. The shortest interchain and interlayer Fe...Fe distances are 6.453 and 11.125 A, respectively. The 4.2-295 K Mössbauer spectra of [Fe(pyoa) 2] infinity consist of a single paramagnetic high-spin iron(II) quadrupole doublet. The axial Fe-N bond direction defines the Jahn-Teller axis at an iron(II) site and, consequently, the orientation of the single-ion magnetic anisotropy. Thus, along the b axis in a given chain, the spins are collinear and parallel to the Jahn-Teller axis. The Jahn-Teller axes of adjacent intralayer chains have different orientations with an angle of 79.2 degrees between the axes in adjacent chains in a bc layer. [Fe(pyoa)2]infinity exhibits field-induced metamagnetic behavior such that, in an applied field smaller than the critical field, the iron(II) spin-canted moments experience intrachain ferromagnetic interactions and weak interchain antiferromagnetic interactions; the spin canting yields weak ferromagnetism. In an applied field larger than the critical field, the weak antiferromagnetic interchain interactions are overwhelmed to yield superparamagnetic-like slow-magnetic relaxation with an energy barrier of 23(3) K. Single-crystal magnetic studies reveal a quasi-uniaxial magnetic anisotropy with the a axis as the easy-magnetic axis and the b axis as the hard-magnetic axis; the susceptibility measured along the easy a axis may be fit with the Glauber model to yield an effective intrachain exchange coupling constant of 2.06(8) K. A dynamic analysis of the

  18. Co-assembly of Zn(SPh){sub 2} and organic linkers into helical and zig-zag polymer chains

    SciTech Connect

    Liu Yi; Yu Lingmin; Loo, Say Chye Joachim; Blair, Richard G.; Zhang Qichun

    2012-07-15

    Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (EG=ethylene glycol) (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized under solvothermal conditions at 150 Degree-Sign C or room temperature by the co-assembly of Zn(SPh){sub 2} and organic linkers such as 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPyTA) and 1,3-bis(trans-4-pyridylvinyl)benzene (BPyVB). X-ray crystallography study reveals that both polymers 1 and 2 crystallize in space group P2{sub 1}/c of the monoclinic system. The solid-state UV-vis absorption spectra show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. - Graphical abstract: Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized. Solid-state UV-vis absorptions show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Two novel one-dimensional coordination polymers have been synthesized. Black-Right-Pointing-Pointer TPyTA results in helical structures in 1 while BPyVB leads to zig-zag chains in 2. Black-Right-Pointing-Pointer Solid-state UV-vis absorption spectra and TGA analysis of the title polymers were studied.

  19. BET, thermal degradation, and FTIR spectras of triazine polyamine polymers.

    PubMed

    Can, Mustafa

    2017-04-01

    Here we show effect of the polyamine polymer chain length to BET isotherms. According to IUPAC classification [1], all three polymers are fitting type 1 physical adsorption isotherm with H3 hysteresis (except for EDA having H2 hysteresis). Moreover, TG and TGA analysis of polymers triazine-ethylenediamine (EDA) and triazine-triethylenetetramine (TETA) are provided. Due to the similarities of the structure, main decomposition temperatures are close to each other (between 593 K and 873 K). In order to understand change of FTIR spectra with adsorption and stripping Au(III), fresh, Au(III) adsorbed and recycled spectras of polymers measured. For further discussions about the effect of chain length to adsorption of Au(III) onto triazine polyamine polymer particles "Au (III) Uptake by Triazine Polyamine Polymers: Mechanism, Kinetic and Equilibrium Studies" Can et al. [2] (article in press).

  20. Solid Polymer Electrolytes with Excellent High-Temperature Properties Based on Brush Block Copolymers Having Rigid Side Chains.

    PubMed

    Ping, Jing; Pan, Hongbing; Hou, Ping Ping; Zhang, Meng-Yao; Wang, Xing; Wang, Chao; Chen, Jitao; Wu, Decheng; Shen, Zhihao; Fan, Xing-He

    2017-02-22

    A series of brush block copolymers (BBCPs) with polynorbornene backbones containing poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS, which is a rigid chain) and poly(ethylene oxide) (PEO) side chains were synthesized by tandem ring-opening metathesis polymerizations. The weight fractions of PEO in BBCPs are similar, and the degrees of polymerization (DPs) of PEO side chains are the same while the DPs of PMPCS are different. The bulk self-assembling behaviors were studied by small-angle X-ray scattering (SAXS). The neat BBCPs cannot form ordered nanostructures. However, after the doping of lithium salt, the BBCPs self-assemble into lamellar (LAM) structures. When the DPs of the PEO and PMPCS side chains are similar, the LAM structure is more ordered, which is attributed to the more flat interface between PMPCS and PEO phases. The ionic conductivity (σ) values of the BBCP/lithium salt complex with the most ordered LAM structure at different temperatures were measured. The σ value increases with increasing temperature in the range of 40-200 °C, and the relationship between σ and T fits the Vogel-Tamman-Fulcher (VTF) equation. The σ value at 200 °C is 1.58 × 10(-3) S/cm, which is one of the highest values for PEO-based polymer electrolytes. These materials with high σ values at high temperatures may be used in high-temperature lithium ion batteries.

  1. Role of polar side chains in Li(+) coordination and transport properties of polyoxetane-based polymer electrolytes.

    PubMed

    Sai, Ryansu; Ueno, Kazuhide; Fujii, Kenta; Nakano, Yohei; Shigaki, Naho; Tsutsumi, Hiromori

    2017-02-15

    Lithium ion conducting polymer electrolytes (PEs) have been the subject of intense research for lithium metal battery applications. Here, we investigate the effects of polar side chains on Li(+) coordination and ionic transport properties to gain insights for improving the insufficient conductivity of traditional ether-based solid PEs. Poly(trimethyleneoxide)-based (or polyoxetane-based) polymers with ether or nitrile groups were synthesized by ring-opening polymerization. The thermal, ionic transport, and electrochemical properties and the local structure of Li(+) coordination were studied in the presence of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA). The glass transition temperature (Tg) of the PEs with ether side chains increased with increasing LiTFSA content, whereas the PEs with the nitrile functionality showed the opposite trend at higher salt concentrations. In addition to the unique trend for the Tg values of the PEs in the presence of LiTFSA, the nitrile groups played pivotal roles as coordination sites for Li(+) ions in the first coordination shell and as a polar medium to increase the permittivity of the PEs. These characteristics of the nitrile groups can endow PEs with improved ionic transport properties.

  2. Influence of Belousov-Zhabotinsky substrate concentrations on autonomous oscillation of polymer chains with Fe(bpy)3 catalyst.

    PubMed

    Hara, Yusuke; Mayama, Hiroyuki; Fujimoto, Kenji

    2014-06-19

    We studied the effect of initial substrate concentrations in the Belousov-Zhabotinsky (BZ) reaction on the optical transmittance self-oscillation behavior of a polymer chain consisting of N-isopropylacrylamide (NIPAAm) and a Fe catalyst ([Fe(bpy)3]). The driving force of this transmittance self-oscillation was the solubility difference between the reduced and oxidized states of the [Fe(bpy)3] moiety in the polymer chain. The amplitude of the soluble-insoluble self-oscillation of poly(NIPAAm-co-[Fe(bpy)3]) was significantly smaller than that of poly(NIPAAm-co-[Ru(bpy)3]). Theoretical simulation results attributed this behavior to the small difference in the solvent qualities, C*, of the reduced and oxidized states. Furthermore, we clarified that poly(NIPAAm-co-[Fe(bpy)3]) required a narrower concentration range of HNO3 to exhibit self-oscillation than poly(NIPAAm-co-[Ru(bpy)3]), since transmittance self-oscillation occurred only for [HNO3] = 0.3 M. The period of self-oscillation of poly(NIPAAm-co-[Fe(bpy)3]) in solution was controlled mainly by NaBrO3 concentration and was hardly influenced by the initial concentration of malonic acid.

  3. Exploiting Supramolecular Interactions for the Intramolecular Folding of Side-Chain Functionalized Polymers and Assembly of Anisotropic Colloids

    NASA Astrophysics Data System (ADS)

    Romulus, Joy

    The overarching goal presented in this thesis is the self-assembly of synthetic systems into higher ordered structures utilizing supramolecular chemistry. Noncovalent interactions including charge-transfer and hydrogen bonding as well as DNA hybridization are exploited to induce the assembly of polymers and colloids into well-defined architectures. This strategy provides a tunable handle on materials bulk properties that can be adjusted by simply changing variables such as temperature and solvent. A brief overview of design principles for the supramolecular assembly of side-chain functionalized polymers is presented. The polymerization technique selected was living ring-opening metathesis polymerization (ROMP), thus affording control over molecular weight and molecular weight distributions. ROMP also allowed for the incorporation of functional groups that were used to assemble the polymers into ordered structures. Charge-transfer motifs were exploited and shown to drive the assembly of random and alternating copolymers via intramolecular side-chain interactions. Incorporation of complementary hydrogen bonding motifs was shown to guide the single-chain folding of a multifunctional triblock copolymer into sheet-like structures. Precision over the size, shape, and monomer sequence were identified as key elements for efficient self-assembly. The self-assembly of colloids using DNA hybridization was also investigated. Previously, the majority of colloid-based research relied upon the self-assembly of spherical isotropic particles into closed-packed arrangements. In contrast, anisotropic particles may allow for the realization of open structures. By expanding upon a method to permanently cross-link DNA strands incubated on a colloidal surface, a new strategy to engineer patchy particles is described. These functional DNA-coated patches are demonstrated to direct particle assembly. The self-assembly of polymer and colloidal systems utilizing noncovalent interactions

  4. Controllable conversion of quasi-freestanding polymer chains to graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Ma, Chuanxu; Xiao, Zhongcan; Zhang, Honghai; Liang, Liangbo; Huang, Jingsong; Lu, Wenchang; Sumpter, Bobby G.; Hong, Kunlun; Bernholc, J.; Li, An-Ping

    2017-03-01

    In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections from a scanning tunnelling microscope (STM) tip. While catalytic cyclodehydrogenations typically occur in a domino-like conversion process during the thermal annealing, the hole-injection-assisted reactions happen at selective molecular sites controlled by the STM tip. The charge injections lower the cyclodehydrogenation barrier in the catalyst-free formation of graphitic lattices, and the orbital symmetry conservation rules favour hole rather than electron injections for the GNR formation. The created polymer-GNR intraribbon heterostructures have a type-I energy level alignment and strongly localized interfacial states. This finding points to a new route towards controllable synthesis of freestanding graphitic layers, facilitating the design of on-surface reactions for GNR-based structures.

  5. Two Zn coordination polymers with meso-helical chains based on mononuclear or dinuclear cluster units

    SciTech Connect

    Qin, Ling; Qiao, Wen-Cheng; Zuo, Wei-Juan; Zeng, Si-Ying; Mei, Cao; Liu, Chang-Jiang

    2016-07-15

    Two zinc coordination polymers {[Zn_2(TPPBDA)(oba)_2]·DMF·1.5H_2O}{sub n} (1), {[Zn(TPPBDA)_1_/_2(tpdc)]·DMF}{sub n} (2) have been synthesized by zinc metal salt, nanosized tetradentate pyridine ligand with flexible or rigid V-shaped carboxylate co-ligands. These complexes were characterized by elemental analyses and X-ray single-crystal diffraction analyses. Compound 1 is a 2-fold interpenetrated 3D framework with [Zn{sub 2}(CO{sub 2}){sub 4}] clusters. Compound 2 can be defined as a five folded interpenetrating bbf topology with mononuclear Zn{sup 2+}. These mononuclear or dinuclear cluster units are linked by mix-ligands, resulting in various degrees of interpenetration. In addition, the photoluminescent properties for TPPBDA ligand under different state and coordination polymers have been investigated in detail. - Graphical abstract: Two zinc coordination polymers have been synthesized by zinc metal salt, nanosized tetradentate pyridine ligand with flexible or rigid V-shaped carboxylate co-ligands. Compound 1 is a 2-fold interpenetrated 3D framework with [Zn{sub 2}(CO{sub 2}){sub 4}] clusters. Compound 2 can be defined as a five folded interpenetrating bbf topology with mononuclear Zn{sup 2+}. In addition, the photoluminescent properties for TPPBDA ligand under different status and coordination polymers have been investigated in detail. Display Omitted - Highlights: • Two Zn coordination polymers based on mononuclear or dinuclear cluster units have been synthesized. • Compound 1 is a 2-fold interpenetrated 3D framework with [Zn{sub 2}(CO{sub 2}){sub 4}] clusters. • Compound 2 is a five folded interpenetrating bbf topology with mononuclear Zn{sup 2+}. • The photoluminescent properties for TPPBDA with different state and two coordination polymers have been investigated.

  6. Structural transformations, composition anomalies and a dramatic collapse of linear polymer chains in dilute ethanol-water mixtures.

    PubMed

    Banerjee, Saikat; Ghosh, Rikhia; Bagchi, Biman

    2012-03-29

    Water-ethanol mixtures exhibit many interesting anomalies, such as negative excess partial molar volume of ethanol, excess sound absorption coefficient at low concentrations, and positive deviation from Raoult's law for vapor pressure, to mention a few. These anomalies have been attributed to different, often contradictory origins, but a quantitative understanding is still lacking. We show by computer simulation and theoretical analyses that these anomalies arise from the sudden emergence of a bicontinuous phase that occurs at a relatively low ethanol concentration of x(eth) ≈ 0.06-0.10 (that amounts to a volume fraction of 0.17-0.26, which is a significant range!). The bicontinuous phase is formed by aggregation of ethanol molecules, resulting in a weak phase transition whose nature is elucidated. We find that the microheterogeneous structure of the mixture gives rise to a pronounced nonmonotonic composition dependence of local compressibility and nonmonotonic dependence in the peak value of the radial distribution function of ethyl groups. A multidimensional free energy surface of pair association is shown to provide a molecular explanation of the known negative excess partial volume of ethanol in terms of parallel orientation and hence better packing of the ethyl groups in the mixture due to hydrophobic interactions. The energy distribution of the ethanol molecules indicates additional energy decay channels that explain the excess sound attenuation coefficient in aqueous alcohol mixtures. We studied the dependence of the solvation of a linear polymer chain on the composition of the water-ethanol solvent. We find that there is a sudden collapse of the polymer at x(eth) ≈ 0.05-a phenomenon which we attribute to the formation of the microheterogeneous structures in the binary mixture at low ethanol concentrations. Together with recent single molecule pulling experiments, these results provide new insight into the behavior of polymer chain and foreign solutes

  7. Influence of alkyl chain length on charge transport in symmetrically substituted poly(2,5-dialkoxy- p -phenylenevinylene) polymers

    NASA Astrophysics Data System (ADS)

    Tuladhar, Sachetan M.; Sims, Marc; Kirkpatrick, James; Maher, Robert C.; Chatten, Amanda J.; Bradley, Donal D. C.; Nelson, Jenny; Etchegoin, Pablo G.; Nielsen, Christian B.; Massiot, Philippe; George, Wayne N.; Steinke, Joachim H. G.

    2009-01-01

    We report on the hole transport characteristics, as measured by time of flight, of a family of symmetrically substituted dialkoxy poly( p -phenylenevinylene) polymers with different side-chain length. As side-chain length is decreased, the magnitude of the hole mobility μh increases while the field dependence of μh becomes more positive and the temperature dependence of μh becomes stronger. For the shortest side-chain derivative studied, μh exceeds 10-4cm2V-1s-1 at electric fields greater than 105Vcm-1 . The trend in magnitude of μh with side-chain length is consistent with the expected increase in electronic wave-function overlap as interchain separation decreases, while the trends in electric-field and temperature dependences of μh are consistent with increasing site energy disorder. We show that the electrostatic contribution to the site energy difference for pairs of oligomers follows the observed trend as a function of interchain separation, although the pairwise contribution is too small to explain the data quantitatively. Nonresonant Raman spectroscopy is used to characterize the microstructure of our films. We construct spatial maps of the Raman ratio I1280/I1581 and confirm an expected decrease in average film density with side-chain extension. The structural heterogeneity in the maps is analyzed but no clear correlation is observed with transport properties, suggesting that the structural variations relevant for charge transport occur on a length scale finer than the resolution of ˜1μm .

  8. Introduction to Polymer Chemistry.

    ERIC Educational Resources Information Center

    Harris, Frank W.

    1981-01-01

    Reviews the physical and chemical properties of polymers and the two major methods of polymer synthesis: addition (chain, chain-growth, or chain-reaction), and condensation (step-growth or step-reaction) polymerization. (JN)

  9. Étude thermodynamique du polymère super absorbant X10 vis à vis de l'eau vapeur

    NASA Astrophysics Data System (ADS)

    Bakass, M.; Bellat, J. P.; Mokhlisse, A.; Bertrand, G.

    2004-12-01

    The organic polymers super absorbents present values of specific surface lower than 2m2/g. The isobars of adsorption of water vapor on studied polymer are of type III at ambient temperature with the hysterisis phenomena. For temperatures lower than ambient, the isobars become deformed because of an effect of chains. This type of polymer is characterized by a multi-layer adsorption which occurs before the full-course one is complete. During reactions of adsorption, the polymer undergoes rearrangement polymeric network which results from a co-operative diffusion of the water molecules and from a spacing of chain followed by an expansion of the polymeric network. Three types of water molecules adsorbed on polymer were identified: strongly dependent water, adsorbed water and the water only trapped between the macromolecular chains.

  10. Construction and Self-Assembly of Single-Chain Polymer Nanoparticles via Coordination Association and Electrostatic Repulsion in Water.

    PubMed

    Zhu, Zhengguang; Xu, Na; Yu, Qiuping; Guo, Lei; Cao, Hui; Lu, Xinhua; Cai, Yuanli

    2015-08-01

    Simultaneous coordination-association and electrostatic-repulsion interactions play critical roles in the construction and stabilization of enzymatic function metal centers in water media. These interactions are promising for construction and self-assembly of artificial aqueous polymer single-chain nanoparticles (SCNPs). Herein, the construction and self-assembly of dative-bonded aqueous SCNPs are reported via simultaneous coordination-association and electrostatic-repulsion interactions within single chains of histamine-based hydrophilic block copolymer. The electrostatic-repulsion interactions are tunable through adjusting the imidazolium/imidazole ratio in response to pH, and in situ Cu(II)-coordination leads to the intramolecular association and single-chain collapse in acidic water. SCNPs are stabilized by the electrostatic repulsion of dative-bonded block and steric shielding of nonionic water-soluble block, and have a huge specific surface area of function metal centers accessible to substrates in acidic water. Moreover, SCNPs can assemble into micelles, networks, and large particles programmably in response to the solution pH. These unique media-sensitive phase-transformation behaviors provide a general, facile, and versatile platform for the fabrication of enzyme-inspired smart aqueous catalysts.

  11. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  12. A force-level theory of the rheology of entangled rod and chain polymer liquids. I. Tube deformation, microscopic yielding, and the nonlinear elastic limit

    NASA Astrophysics Data System (ADS)

    Schweizer, Kenneth S.; Sussman, Daniel M.

    2016-12-01

    We employ a first-principles-based, force-level approach to construct the anharmonic tube confinement field for entangled fluids of rigid needles, and also for chains described at the primitive-path (PP) level in two limiting situations where chain stretch is assumed to either be completely equilibrated or unrelaxed. The influence of shear and extensional deformation and polymer orientation is determined in a nonlinear elastic limit where dissipative relaxation processes are intentionally neglected. For needles and PP-level chains, a self-consistent analysis of transverse polymer harmonic dynamical fluctuations predicts that deformation-induced orientation leads to tube weakening or widening. In contrast, for deformed polymers in which chain stretch does not relax, we find tube strengthening or compression. For all three systems, a finite maximum transverse entanglement force localizing the polymers in effective tubes is predicted. The conditions when this entanglement force can be overcome by an externally applied force associated with macroscopic deformation can be crisply defined in the nonlinear elastic limit, and the possibility of a "microscopic absolute yielding" event destroying the tube confinement can be analyzed. For needles and contour-relaxed PP chains, this force imbalance occurs at a stress of order the equilibrium shear modulus and a strain of order unity, corresponding to a mechanically fragile entanglement tube field. However, for unrelaxed stretched chains, tube compression stabilizes transverse polymer confinement, and there appears to be no force imbalance. These results collectively suggest that the crossover from elastic to irreversible viscous response requires chain retraction to initiate disentanglement. We qualitatively discuss comparisons with existing phenomenological models for nonlinear startup shear, step strain, and creep rheology experiments.

  13. Kinetics of chain collapse in dilute polymer solutions: molecular weight and solvent dependences.

    PubMed

    Maki, Yasuyuki; Dobashi, Toshiaki; Nakata, Mitsuo

    2007-04-07

    The molecular weight and solvent dependences of the characteristic time of chain collapse were studied for poly(methyl methacrylate) (PMMA) of the molecular weight Mw=6.4x10(6) and 1.14x10(7) in pure acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol %). The size of PMMA chains was measured as a function of the time after the quench by static light scattering and the chain collapse processes were expressed by the plot of the expansion factor alpha2 vs ln t. The chain collapse in the mixed solvent AcN+water (10 vol %) was found to occur much faster than that in pure AcN, though the measurement of the former collapse process required several hours. In order to make a comparison between the rates of chain collapses, the fast chain collapse process was superposed on the slow one by scaling the time of the fast process as gammat. The scale factor gamma was determined by comparing the chain collapse processes of nearly the same equilibrium expansion factor with each other. Accordingly, the superposition of the collapse for Mw=6.4x10(6) on that for Mw=1.14x10(7) yielded gammam=4.0+/-0.6 for the process in AcN+water and 5.5+/-0.6 in AcN. The superposition of the chain collapse process in AcN+water on that in AcN yielded gammas=9.5+/-1.4 for Mw=6.4x10(6) and 12.0+/-1.8 for Mw=1.14x10(7). This analysis suggests that gammam and gammas are constant independent of each other. Thus, by assuming the molecular weight dependence of gammam approximately Mz, the characteristic time tauexp of chain collapse was conjectured as tauexp approximately kappaMz, where kappa reflects the nature of solvent species. The ratio of kappa for PMMA in AcN to that in AcN+water is given by gammas. The exponent was estimated to be z=2.4+/-0.7 for AcN+water and 3.0+/-0.7 for AcN. These values are compatible with the theoretical prediction z=3 based on a phenomenological model, though the observed characteristic times are longer by several orders of magnitude than those of the theoretical

  14. Neutron reflectivity as a tool to study the interdigitation of grafted polymer chains and its dynamics

    NASA Astrophysics Data System (ADS)

    Leger, Liliane; Restagno, Frédéric; Cousin, Fabrice; Boue, François; Chenneviere, Alexis

    Three series of experiments aimed at characterizing the interdigitation between a brush and a melt, and based on neutron reflectivity, are presented and discussed. The density profile of brush chains has been analysed for series of annealing times, on h-PS brushes in contact with d-PS melts, as a function of molecular weights and grafting densities. We show that the relaxation dynamics of the brush chains can be modelled taking into account the long relaxation time of end tethered chains along with the reptation of the melt chains which accelerates the arm retraction process. Using a non-grafted layer with a thickness smaller than the equilibrium size of the brush when immersed into a thick melt allows one to apply chosen degrees of confinement to the brush. We show that the interdigitation dynamics is affected by such confinements, in a way reminiscent of the change of the glass transition temperature in nanometric PS films. Finally, when the upper d-PS layer is sheared above Tg, flow with large slip at the wall has been observed and interpreted in terms of stretching and expulsion of the grafted chains from the melt. We show how neutron reflectivity directly evidence this expulsion.

  15. Untying a nanoscale knotted polymer structure to linear chains for efficient gene delivery in vitro and to the brain

    NASA Astrophysics Data System (ADS)

    Newland, B.; Aied, A.; Pinoncely, A. V.; Zheng, Y.; Zhao, T.; Zhang, H.; Niemeier, R.; Dowd, E.; Pandit, A.; Wang, W.

    2014-06-01

    The purpose of this study was to develop a platform transfection technology, for applications in the brain, which could transfect astrocytes without requiring cell specific functionalization and without the common cause of toxicity through high charge density. Here we show that a simple and scalable preparation technique can be used to produce a ``knot'' structured cationic polymer, where single growing chains can crosslink together via disulphide intramolecular crosslinks (internal cyclizations). This well-defined knot structure can thus ``untie'' under reducing conditions, showing a more favorable transfection profile for astrocytes compared to 25 kDa-PEI (48-fold), SuperFect® (39-fold) and Lipofectamine®2000 (18-fold) whilst maintaining neural cell viability at over 80% after four days of culture. The high transfection/lack of toxicity of this knot structured polymer in vitro, combined with its ability to mediate luciferase transgene expression in the adult rat brain, demonstrates its use as a platform transfection technology which should be investigated further for neurodegenerative disease therapies.The purpose of this study was to develop a platform transfection technology, for applications in the brain, which could transfect astrocytes without requiring cell specific functionalization and without the common cause of toxicity through high charge density. Here we show that a simple and scalable preparation technique can be used to produce a ``knot'' structured cationic polymer, where single growing chains can crosslink together via disulphide intramolecular crosslinks (internal cyclizations). This well-defined knot structure can thus ``untie'' under reducing conditions, showing a more favorable transfection profile for astrocytes compared to 25 kDa-PEI (48-fold), SuperFect® (39-fold) and Lipofectamine®2000 (18-fold) whilst maintaining neural cell viability at over 80% after four days of culture. The high transfection/lack of toxicity of this knot

  16. Synthesis of metronidazole-imprinted molecularly imprinted polymers by distillation precipitation polymerization and their use as a solid-phase adsorbent and chromatographic filler.

    PubMed

    Liu, Jiang; Zhang, Lu; Li Han Song, Le; Liu, Yuan; Tang, Hui; Li, Yingchun

    2015-04-01

    Metronidazole-imprinted polymers with superior recognition properties were prepared by a novel strategy called distillation-precipitation polymerization. The as-obtained polymers were characterized by Fourier-transform infrared spectroscopy, laser particle size determination and scanning electron microscopy, and their binding performances were evaluated in detail by static, kinetic and dynamic rebinding tests, and Scatchard analysis. The results showed that when the fraction of the monomers was 5 vol% in the whole reaction system, the prepared polymers afforded good morphology, monodispersity, and high adsorption capacity and excellent selectivity to the target molecule, metronidazole. The optimal binding performance is 12.41 mg/g for metronidazole just before leakage occurred and 38.51 mg/g at saturation in dynamic rebinding tests. Metronidazole-imprinted polymers were further applied as packing agents in solid-phase extraction and as chromatographic filler, both of which served for the detection of metronidazole in fish tissue. The results illustrated the recoveries of spiked samples ranged from 82.97 to 87.83% by using molecularly imprinted solid-phase extraction combined with a C18 commercial column and 93.7 to 101.2% by directly using the polymer-packed chromatographic column. The relative standard deviation of both methods was less than 6%.

  17. Protein resistant surfaces: comparison of acrylate graft polymers bearing oligo-ethylene oxide and phosphorylcholine side chains.

    PubMed

    Feng, Wei; Zhu, Shiping; Ishihara, Kazuhiko; Brash, John L

    2006-03-01

    The objective of this work was to compare poly(ethylene glycol) (PEG) and phosphorylcholine (PC) moieties as surface modifiers with respect to their ability to inhibit protein adsorption. Surfaces were prepared by graft polymerization of the methacrylate monomers oligo(ethylene glycol) methyl ether methacrylate (OEGMA, MW 300, PEG side chains of length n=4.5) and 2-methacryloyloxyethyl phosphorylcholine (MPC, MW 295). The grafted polymers thus contained short PEG chains and PC, respectively, as side groups. Grafting on silicon was carried out using surface-initiated atom transfer radical polymerization (ATRP). Graft density was controlled via the surface density of the ATRP initiator, and chain length of the grafts was controlled via the ratio of monomer to sacrificial initiator. The grafted surfaces were characterized by water contact angle, x-ray photoelectron spectroscopy, and atomic force microscopy. The effect of graft density and chain length on fibrinogen adsorption from buffer was investigated using radio labeling methods. Adsorption to both MPC- and OEGMA-grafted surfaces was found to decrease with increasing graft density and chain length. Adsorption on the MPC and OEGMA surfaces for a given chain length and density was essentially the same. Very low adsorption levels of the order of 7 ngcm(2) were seen on the most resistant surfaces. The effect of protein size on resistance to adsorption was studied using binary solutions of lysozyme (MW 14 600) and fibrinogen (MW 340 000). Adsorption levels in these experiments were also greatly reduced on the grafted surfaces compared to the control surfaces. It was concluded that at the lowest graft density, both proteins had unrestricted access to the substrate, and the relative affinities of the proteins for the substrate (higher affinity of fibrinogen) determined the composition of the layer. At the highest graft density also, where the adsorption of both proteins was very low, no preference for one or the other

  18. Charge carrier transport properties in polymer liquid crystals containing oxadiazole and amine moieties in the same side chain.

    PubMed

    Kawamoto, Masuki; Mochizuki, Hiroyuki; Ikeda, Tomiki; Iino, Hiroaki; Hanna, Jun-ichi

    2005-05-19

    Steady-state and transient photocurrent measurements were carried out to study the charge carrier transport properties of polymer liquid crystal (LC) containing oxadiazole (OXD) and amine moieties in the same side chain. The steady-state photocurrent measurement with asymmetric electrodes of ITO and Al and a short penetration depth of the illumination light indicated that both electrons and holes can be transported in this film. The transient hole photocurrent observed by time-of-flight (TOF) experiments was dispersive at room temperature. The hole drift mobility significantly depended on temperature and electric field and was determined to be 6.1 x 10(-8) cm2/Vs at a field of 9.1 x 10(5) V/cm. According to the disorder formalism, the Gaussian width of the density of states was determined to be 170 meV for holes. Despite the indication of possible electron transport in this film, we could not determine the electron mobility by TOF experiments due to strong dispersive photocurrent. We discuss the present charge transport properties of the film in relation to a large dipole attributed to an electrical push-pull structure of p-dimethylaminophenyl-substitited OXD moiety in polymer LC and its electroluminescent properties.

  19. Peptide immobilized monolith containing tentacle-type functionalized polymer chains for high-capacity binding of immunoglobulin G.

    PubMed

    Du, Kaifeng

    2014-12-29

    A peptide immobilized tentacle-type monolith is developed here for high-performance IgG purification. In this work, the glucose-anchored GMA molecules serve as monomers to be grafted into the tentacle-type chains on highly porous monolith by a series of chemical reactions. While maintaining high column permeability, the tentacle grafting endows the monolith with lots of reactive handles to anchor more peptides. With that, the grafted monolith shows high peptide density of about 155μmolmL(-1), up to approximately 4.7 times higher over the ungrafted one (33μmolmL(-1)). As a result, the static adsorbing capacity and dynamic adsorption capacity at 50% breakthrough point reach 101.8 and 83.3mgmL(-1) for IgG adsorption, respectively. Regeneration, recycle and reuse of grafted monolith are highly successful for 25 runs without obvious capacity loss. By taking these advantages of high capacity and excellent structure stability, the affinity grafted monolith is evaluated by using cleared human blood supernatant. And the result shows the peptide immobilized tentacle type monolith displays excellent specificity and high effectiveness for IgG purification.

  20. Polymer-Induced Depletion Interaction and Its Effect on Colloidal Sedimentation in Colloid-Polymer Mixtures

    NASA Technical Reports Server (NTRS)

    Tong, Penger

    1996-01-01

    In this paper we focus on the polymer-induced depletion attraction and its effect on colloidal sedimentation in colloid-polymer mixtures. We first report a small angle neutron scattering (SANS) study of the depletion effect in a mixture of hard-sphere-like colloid and non-adsorbing polymer. Then we present results of our recent sedimentation measurements in the same colloid-polymer mixture. A key parameter in controlling the sedimentation of heavy colloidal particles is the interparticle potential U(tau), which is the work required to bring two colloidal particles from infinity to a distance tau under a give solvent condition. This potential is known to affect the average settling velocity of the particles and experimentally one needs to have a way to continuously vary U(tau) in order to test the theory. The interaction potential U(tau) can be altered by adding polymer molecules into the colloidal suspension. In a mixture of colloid and non-adsorbing polymer, the potential U(tau) can develop an attractive well because of the depletion effect, in that the polymer chains are expelled from the region between two colloidal particles when their surface separation becomes smaller than the size of the polymer chains. The exclusion of polymer molecules from the space between the colloidal particles leads to an unbalanced osmotic pressure difference pushing the colloidal particles together, which results in an effective attraction between the two colloidal particles. The polymer-induced depletion attraction controls the phase stability of many colloid-polymer mixtures, which are directly of interest to industry.

  1. Chain length dependence of the thermodynamic properties of linear and cyclic alkanes and polymers.

    PubMed

    Huang, Dinghai; Simon, Sindee L; McKenna, Gregory B

    2005-02-22

    The specific heat capacity was measured with step-scan differential scanning calorimetry for linear alkanes from pentane (C(5)H(12)) to nonadecane (C(19)H(40)), for several cyclic alkanes, for linear and cyclic polyethylenes, and for a linear and a cyclic polystyrene. For the linear alkanes, the specific heat capacity in the equilibrium liquid state decreases as chain length increases; above a carbon number N of 10 (decane) the specific heat asymptotes to a constant value. For the cyclic alkanes, the heat capacity in the equilibrium liquid state is lower than that of the corresponding linear chains and increases with increasing chain length. At high enough molecular weights, the heat capacities of cyclic and linear molecules are expected to be equal, and this is found to be the case for the polyethylenes and polystyrenes studied. In addition, the thermal properties of the solid-liquid and the solid-solid transitions are examined for the linear and cyclic alkanes; solid-solid transitions are observed only in the odd-numbered alkanes. The thermal expansion coefficients and the specific volumes of the linear and cyclic alkanes are also calculated from literature data and compared with the trends in the specific heats.

  2. Treatment of disordered and ordered systems of polymer chains by lattice methods

    PubMed Central

    Flory, Paul J.

    1982-01-01

    Classical lattice theories of systems of long-chain molecules provide estimates of the number Z of random configurations to the exclusion of ordered ones. The decrease of Z thus estimated to values [unk]1 with decrease in chain flexibility at high densities is genuine, but it does not take account of eligible ordered configurations; the latter are not a subset of the configurations whose numbers are estimated by classical lattice methods. Failure to recognize this fact and the fundamental distinction between disordered and ordered states has engendered misinterpretations and has cast doubt on the validity of lattice-statistical methods. In a system at equilibrium, the decline of Z (disordered) with decrease in chain flexibility must be arrested by a first order transition to an ordered state. The inference that approach of Z (disordered) to values <1 presages a thermodynamic transition of second order is tenable only if the array of ordered configurations, not comprehended by theories in which the mean field of unoccupied lattice sites is random, can be ignored. PMID:16593214

  3. Effects of variation in chain length on ternary polymer electrolyte - Ionic liquid mixture - A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Raju, S. G.; Hariharan, Krishnan S.; Park, Da-Hye; Kang, HyoRang; Kolake, Subramanya Mayya

    2015-10-01

    Molecular dynamics (MD) simulations of ternary polymer electrolyte - ionic liquid mixtures are conducted using an all-atom model. N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([CnMPy][TFSI], n = 1, 3, 6, 9) and polyethylene oxide (PEO) are used. Microscopic structure, energetics and dynamics of ionic liquid (IL) in these ternary mixtures are studied. Properties of these four pure IL are also calculated and compared to that in ternary mixtures. Interaction between pyrrolidinium cation and TFSI is stronger and there is larger propensity of ion-pair formation in ternary mixtures. Unlike the case in imidazolium IL, near neighbor structural correlation between TFSI reduces with increase in chain length on cation in both pure IL and ternary mixtures. Using spatial density maps, regions where PEO and TFSI interact with pyrrolidinium cation are identified. Oxygens of PEO are above and below the pyrrolidinium ring and away from the bulky alkyl groups whereas TFSI is present close to nitrogen atom of CnMPy. In pure IL, diffusion coefficient (D) of C3MPy is larger than of TFSI but D of C9MPy and C6MPy are larger than that of TFSI. The reasons for alkyl chain dependent phenomena are explored.

  4. Optimal Reactivity and Improved Self-Healing Capability of Structurally Dynamic Polymers Grafted on Janus Nanoparticles Governed by Chain Stiffness and Spatial Organization.

    PubMed

    Xu, Guoxi; Huang, Zihan; Chen, Pengyu; Cui, Tianqi; Zhang, Xinghua; Miao, Bing; Yan, Li-Tang

    2017-01-16

    Structurally dynamic polymers are recognized as a key potential to revolutionize technologies ranging from design of self-healing materials to numerous biomedical applications. Despite intense research in this area, optimizing reactivity and thereby improving self-healing ability at the most fundamental level pose urgent issue for wider applications of such emerging materials. Here, the authors report the first mechanistic investigation of the fundamental principle for the dependence of reactivity and self-healing capabilities on the properties inherent to dynamic polymers by combining large-scale computer simulation, theoretical analysis, and experimental discussion. The results allow to reveal how chain stiffness and spatial organization regulate reactivity of dynamic polymers grafted on Janus nanoparticles and mechanically mediated reaction in their reverse chemistry, and, particularly, identify that semiflexible dynamic polymers possess the optimal reactivity and self-healing ability. The authors also develop an analytical model of blob theory of polymer chains to complement the simulation results and reveal essential scaling laws for optimal reactivity. The findings offer new insights into the physical mechanism in various systems involving reverse/dynamic chemistry. These studies highlight molecular engineering of polymer architecture and intrinsic property as a versatile strategy in control over the structural responses and functionalities of emerging materials with optimized self-healing capabilities.

  5. Molecularly Imprinted Filtering Adsorbents for Odor Sensing

    PubMed Central

    Shinohara, Sho; Chiyomaru, You; Sassa, Fumihiro; Liu, Chuanjun; Hayashi, Kenshi

    2016-01-01

    Versatile odor sensors that can discriminate among huge numbers of environmental odorants are desired in many fields, including robotics, environmental monitoring, and food production. However, odor sensors comparable to an animal’s nose have not yet been developed. An animal’s olfactory system recognizes odor clusters with specific molecular properties and uses this combinatorial information in odor discrimination. This suggests that measurement and clustering of odor molecular properties (e.g., polarity, size) using an artificial sensor is a promising approach to odor sensing. Here, adsorbents composed of composite materials with molecular recognition properties were developed for odor sensing. The selectivity of the sensor depends on the adsorbent materials, so specific polymeric materials with particular solubility parameters were chosen to adsorb odorants with various properties. The adsorption properties of the adsorbents could be modified by mixing adsorbent materials. Moreover, a novel molecularly imprinted filtering adsorbent (MIFA), composed of an adsorbent substrate covered with a molecularly imprinted polymer (MIP) layer, was developed to improve the odor molecular recognition ability. The combination of the adsorbent and MIP layer provided a higher specificity toward target molecules. The MIFA thus provides a useful technique for the design and control of adsorbents with adsorption properties specific to particular odor molecules. PMID:27886070

  6. Precise Side-Chain Engineering of Thienylenevinylene-Benzotriazole-Based Conjugated Polymers with Coplanar Backbone for Organic Field Effect Transistors and CMOS-like Inverters.

    PubMed

    Lee, Min-Hye; Kim, Juhwan; Kang, Minji; Kim, Jihong; Kang, Boseok; Hwang, Hansu; Cho, Kilwon; Kim, Dong-Yu

    2017-01-25

    Two donor-acceptor (D-A) alternating conjugated polymers based on thienylenevinylene-benzotriazole (TV-BTz), PTV6B with a linear side chain and PTVEhB with a branched side chain, were synthesized and characterized for organic field effect transistors (OFETs) and complementary metal-oxide-semiconductor (CMOS)-like inverters. According to density functional theory (DFT), polymers based on TV-BTz exhibit a coplanar and rigid structure with no significant twists, which could cause to an increase in charge-carrier mobility in OFETs. Alternating alkyl side chains of the polymers impacted neither the band gap nor the energy level. However, it significantly affected the morphology and crystallinity when the polymer films were thermally annealed. To investigate the effect of thermal annealing on the morphology and crystallinity, we characterized the polymer films using atomic force microscopy (AFM) and 2D-grazing incidence X-ray diffraction (2D-GIWAXD). Fibrillary morphologies with larger domains and increased crystallinity were observed in the polymer films after thermal annealing. These polymers exhibited improved charge-carrier mobilities in annealed films at 200 °C and demonstrated optimal OFET device performance with p-type transport characteristics with charge-carrier mobilities of 1.51 cm(2)/(V s) (PTV6B) and 2.58 cm(2)/(V s) (PTVEhB). Furthermore, CMOS-like inorganic (ZnO)-organic (PTVEhB) hybrid bilayer inverter showed that the inverting voltage (Vinv) was positioned near the ideal switching point at half (1/2) of supplied voltage (VDD) due to fairly balanced p- and n-channels.

  7. Investigation of the effects of short chain processing additives on polymers

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Stclair, T. L.; Pratt, J. R.

    1986-01-01

    The effects of low level concentrations of several short chain processing additives on the properties of the 4,4'-bis(3,4-dicarboxyphenoxy) diphenylsulfide dianhydride (BDSDA)/4,4'-diaminodiphenyl ether (ODA)/1,3'-diaminobenzene (m-phenylene diamine) (MPA) (422) copolyimide were investigated. It was noted that 5 percent MPD/phthalic anhydride (PA) is more effective than 5 percent ODA/PA and BDSDA/aniline (AN) in strengthening the host material. However, the introduction of 10 percent BDSDA/AN produces disproportionately high effects on free volume and free electron density in the host copolyimide.

  8. Large and Reversible Plasmon Tuning using Ultrathin Responsive Polymer film

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Nergiz, Saide

    2011-03-01

    We demonstrate reversible linear and branched aggregation of gold nanoparticles adsorbed on an ultrathin responsive polymer ((poly(4-vinyl pyridine), P4VP) film. P4VP is a weak cationic polymer, which exhibits a reversible coil to globule transition with change in external pH. Atomic force microscopy revealed that in the coiled state (below the isoelectric point of the polymer) of the polymer chains, gold nanoparticles adsorbed on the polymer layer existed as primarily individual nanoparticles. On the other hand, lowering the pH caused the polymer chains to transition from coil to globule state, resulting in aggregation of the nanoparticles into linear and branched chains. Reversible aggregation of the nanoparticles results in a dramatic change in the optical properties of the metal nanostructures. Apart from the large redistribution of the intensity between the individual (530 nm) and coupled (650 nm) plasmon bands, the coupled plasmon band exhibits a shift of nearly 60 nm with change in external pH. The pH triggered aggregation of the nanoparticles and the dramatic change in the optical properties associated with the same can form an excellent platform for colorimetric sensing. The work reported here is supported by the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.

  9. The Role of Morphology and Electronic Chain Aggregation on the Optical Gain Properties of Semiconducting Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Lampert, Zachary Evan

    Conjugated polymers (CPs) are a novel class of materials that exhibit the optical and electrical properties of semiconductors while still retaining the durability and processability of plastics. CPs are also intrinsically 4-level systems with high luminescence quantum efficiencies making them particularly attractive as organic gain media for solid-state laser applications. However, before CPs can emerge as a commercially available laser technology, a more comprehensive understanding of the morphological dependence of the photophysics is required. In this thesis, the morphology and chain conformation dependence of amplified spontaneous emission (ASE) and optical gain in thin films of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) was investigated. By changing the chemical nature of the solvent from which films were cast, as well as the temperature at which films were annealed, CP films with different morphologies, and hence different degrees of interchain interactions were achieved. Contrary to the common perception that polymer morphology plays a decisive role in determining the ASE behavior of thin CP films, we found that chromophore aggregation and degree of conformational order have minimal impact on optical gain. In fact, experimental results indicated that an extremely large fraction of interchain aggregate species and/or exciton dissociating defects are required to significantly alter the optical properties and suppress stimulated emission. These results are pertinent to the fabrication and optimization of an electrically pumped laser device, as improvements in charge carrier mobility through controlled increases in chain aggregation may provide a viable means of optimizing injection efficiency without significantly degrading optical gain. To offset charge-induced absorption losses under electrical pumping, and to enable the use of more compact and economical sources under optical pumping, conjugated polymers exhibiting low lasing

  10. Behavior of cationic surfactants and short-chain alcohols in mixed surface layers at water-air and polymer-water interfaces with regard to polymer wettability II. Wettability of polymers.

    PubMed

    Zdziennicka, Anna; Jańczuk, Bronisław

    2010-10-15

    The wettability of polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) by aqueous solutions of cetyltrimethylammonium bromide (CTAB) mixtures with short-chain alcohols such as methanol, ethanol, and propanol, as well as for 1-hexadecylpyridinium bromide (CPyB) with the same alcohols, was studied on the basis of advancing contact-angle measurements by the sessile drop method over a wide range of alcohol and cationic surfactant concentrations where they can be present in solution in monomeric or aggregated form. It should be noted that the contact angles for aqueous solution mixtures of cationic surfactants with propanol on PTFE surfaces were measured earlier and presented in our previous paper. From the obtained contact-angle values the relationships between cos theta and surface tension of the solutions (gamma(LV)) and that between adhesion tension and gamma(LV) were considered. The relationship between the cos theta and the reciprocal of gamma(LV) was also discussed. From these relationships the critical surface tension of PTFE and PMMA wetting and the correlation between the adsorption of cationic surfactant and alcohol mixtures at water-air and polymer-water interfaces were deduced. On the basis of the contact angles and components and parameters of the surface tension of surfactants, alcohols, and polymers also the Gibbs and Guggenheim-Adam isotherm of adsorption and the effective concentration of alcohols and surfactants at polymer-water interfaces were calculated. Next, the work of adhesion of solution to polymer surface with regard to the surface monolayer composition was discussed. The analysis of the contact angles with regard to adsorption of surfactants and alcohols at polymer-water and water-air interfaces allowed us to conclude that the PTFE wetting depends only on the contribution of the acid-base interactions to the surface tension of aqueous solutions of cationic surfactant and alcohol mixtures, and the adhesion work of solution to its

  11. Chain-growth click polymerization of AB2 monomers for the formation of hyperbranched polymers with low polydispersities in a one-pot process.

    PubMed

    Shi, Yi; Graff, Robert W; Cao, Xiaosong; Wang, Xiaofeng; Gao, Haifeng

    2015-06-22

    Hyperbranched polymers are important soft nanomaterials but robust synthetic methods with which the polymer structures can be easily controlled have rarely been reported. For the first time, we present a one-pot one-batch synthesis of polytriazole-based hyperbranched polymers with both low polydispersity and a high degree of branching (DB) using a copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization. The use of a trifunctional AB2 monomer that contains one alkyne and two azide groups ensures that all Cu catalysts are bound to polytriazole polymers at low monomer conversion. Subsequent CuAAC polymerization displayed the features of a "living" chain-growth mechanism with a linear increase in molecular weight with conversion and clean chain extension for repeated monomer additions. Furthermore, the triazole group in a linear (L) monomer unit complexed Cu(I) , which catalyzed a faster reaction of the second azide group to quickly convert the L unit into a dendritic unit, producing hyperbranched polymers with DB=0.83.

  12. Synthetic high-charge organomica: effect of the layer charge and alkyl chain length on the structure of the adsorbed surfactants.

    PubMed

    Pazos, M Carolina; Castro, Miguel A; Orta, M Mar; Pavón, Esperanza; Valencia Rios, Jesús S; Alba, María D

    2012-05-15

    A family of organomicas was synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg(6)F(4)O(20)·XH(2)O, where n = 2, 3, and 4) exchanged with dodecylammonium and octadecylammonium cations. The molecular arrangement of the surfactant was elucidated on the basis on XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas was investigated by (13)C, (27)Al, and (29)Si MAS NMR. The arrangement of alkylammonium ions in these high-charge synthetic micas depends on the combined effects of the layer charge of the mica and the chain length of the cation. In the organomicas with dodecylammonium, a transition from a parallel layer to a bilayer-paraffin arrangement is observed when the layer charge of the mica increases. However, when octadecylammonium is the interlayer cation, the molecular arrangement of the surfactant was found to follow the bilayer-paraffin model for all values of layer charge. The amount of ordered conformation all-trans is directly proportional of layer charge.

  13. Nucleic acid chemistry in the organic phase: from functionalized oligonucleotides to DNA side chain polymers.

    PubMed

    Liu, Kai; Zheng, Lifei; Liu, Qing; de Vries, Jan Willem; Gerasimov, Jennifer Y; Herrmann, Andreas

    2014-10-08

    DNA-incorporating hydrophobic moieties can be synthesized by either solid-phase or solution-phase coupling. On a solid support the DNA is protected, and hydrophobic units are usually attached employing phosphoramidite chemistry involving a DNA synthesizer. On the other hand, solution coupling in aqueous medium results in low yields due to the solvent incompatibility of DNA and hydrophobic compounds. Hence, the development of a general coupling method for producing amphiphilic DNA conjugates with high yield in solution remains a major challenge. Here, we report an organic-phase coupling strategy for nucleic acid modification and polymerization by introducing a hydrophobic DNA-surfactant complex as a reactive scaffold. A remarkable range of amphiphile-DNA structures (DNA-pyrene, DNA-triphenylphosphine, DNA-hydrocarbon, and DNA block copolymers) and a series of new brush-type DNA side-chain homopolymers with high DNA grafting density are produced efficiently. We believe that this method is an important breakthrough in developing a generalized approach to synthesizing functional DNA molecules for self-assembly and related technological applications.

  14. Effects of molecular structure on microscopic heat transport in chain polymer liquids

    SciTech Connect

    Matsubara, Hiroki Kikugawa, Gota; Ohara, Taku; Bessho, Takeshi; Yamashita, Seiji

    2015-04-28

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7T{sub c}) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs.

  15. Liquid film/polymer interfaces

    SciTech Connect

    Allara, David L.

    2003-06-12

    The objectives were: (1) Through experimental studies, advance the fundamental understanding of the principles that govern adsorption and wetting phenomena at polymer and organic surfaces. (2) Establish a firm scientific basis for improving the design of coatings for metal fin cooling surfaces used to control the wetting of water condensate for optimum energy efficiency. Several important findings were: (1) water adsorbed at hydrophobic surfaces has a liquid-like structure, in contrast to the generally held view of an ordered structure; (2) Correlations of large amounts of contact angle wetting data of grafted alkyl chain compounds showed a distinct link between the contact angle and the conformational ordering of the chains; (3) water adsorption at long chain alkysiloxane films showed a strong pH dependence on the film stability, which can be attributed to interfacial chemical effects on the siloxane network.

  16. Molecular packing of high-mobility diketo pyrrolo-pyrrole polymer semiconductors with branched alkyl side chains.

    PubMed

    Zhang, Xinran; Richter, Lee J; DeLongchamp, Dean M; Kline, R Joseph; Hammond, Matthew R; McCulloch, Iain; Heeney, Martin; Ashraf, Raja S; Smith, Jeremy N; Anthopoulos, Thomas D; Schroeder, Bob; Geerts, Yves H; Fischer, Daniel A; Toney, Michael F

    2011-09-28

    We describe a series of highly soluble diketo pyrrolo-pyrrole (DPP)-bithiophene copolymers exhibiting field effect hole mobilities up to 0.74 cm(2) V(-1) s(-1), with a common synthetic motif of bulky 2-octyldodecyl side groups on the conjugated backbone. Spectroscopy, diffraction, and microscopy measurements reveal a transition in molecular packing behavior from a preferentially edge-on orientation of the conjugated plane to a preferentially face-on orientation as the attachment density of the side chains increases. Thermal annealing generally reduces both the face-on population and the misoriented edge-on domains. The highest hole mobilities of this series were obtained from edge-on molecular packing and in-plane liquid-crystalline texture, but films with a bimodal orientation distribution and no discernible in-plane texture exhibited surprisingly comparable mobilities. The high hole mobility may therefore arise from the molecular packing feature common to the entire polymer series: backbones that are strictly oriented parallel to the substrate plane and coplanar with other backbones in the same layer.

  17. Performance comparison of long and short-side chain perfluorosulfonic membranes for high temperature polymer electrolyte membrane fuel cell operation

    NASA Astrophysics Data System (ADS)

    Stassi, A.; Gatto, I.; Passalacqua, E.; Antonucci, V.; Arico, A. S.; Merlo, L.; Oldani, C.; Pagano, E.

    A new Aquivion™ E79-03S short-side chain perfluorosulfonic membrane with a thickness of 30 μm (dry form) and an equivalent weight (EW) of 790 g/equiv recently developed by Solvay-Solexis for high-temperature operation was tested in a pressurised (3 bar abs.) polymer electrolyte membrane (PEM) single cell at a temperature of 130 °C. For comparison, a standard Nafion™ membrane (EW 1100 g/equiv) of similar thickness (50 μm) was investigated under similar operating conditions. Both membranes were tested for high temperature operation in conjunction with an in-house prepared carbon supported Pt electrocatalyst. The electrocatalyst consisted of nanosized Pt particles (particle size ∼2 nm) dispersed on a high surface area carbon black. The electrochemical tests showed better performance for the Aquivion™ membrane as compared to Nafion™ with promising properties for high temperature PEM fuel cell applications. Beside the higher open circuit voltage and lower ohmic constraints, a higher electrocatalytic activity was observed at high temperature for the electrocatalyst-Aquivion™ ionomer interface indicating a better catalyst utilization.

  18. Phase behavior of hyperbranched polymer systems: experiments and application of the perturbed-chain polar SAFT equation of state.

    PubMed

    Kozłowska, Marta K; Jürgens, Bas F; Schacht, Christian S; Gross, Joachim; de Loos, Theo W

    2009-01-29

    Vapor-liquid equilibrium data for systems of hyperbranched polymer (HBP) and carbon dioxide are reported for temperatures of 285-455 K and pressures up to 13 MPa. The bubble-point pressures of (CO2 + hyperbranched polyester) and of (CO2 + hyperbranched polyglycerol + CH3OH) samples with fixed compositions were measured using a Cailletet apparatus. The system (CO2 + polyglycerol + CH3OH) also exhibits a liquid-liquid phase split characterized by lower critical solution temperatures. For this system cloud point curves and vapor-liquid-liquid bubble-point curves were also measured. Moreover, a thermodynamic model has been developed for HBP mixtures in the framework of the perturbed-chain polar statistical association fluid theory (PCP-SAFT) equation of state accounting for branching effects. There is no additional binary interaction parameter introduced along with the branching contributions to the model. Although the miscibility gap in the system (CO2 + polyglycerol + CH3OH) is not predicted by the model, PCP-SAFT including branching effects gives a good representation of the bubble-point curves of this system at temperatures lower than the lower solution temperature (LST).

  19. A 1D anionic lanthanide coordination polymer as an adsorbent material for the selective uptake of cationic dyes from aqueous solutions.

    PubMed

    Du, Pei-Yao; Li, Hui; Fu, Xin; Gu, Wen; Liu, Xin

    2015-08-14

    A 1D anionic lanthanide coordination polymer {[(CH(3))(2)NH(2)] [(H(2)abtc)(2)Ho(H(2)O)]}n () (H(4)abtc = 3,3',5,5'-azobenzene-tetracarboxylic acid) has been synthesized under hydrothermal reaction conditions. The protonated [(CH(3))(2)NH(2)](+) is generated from decomposed DMA during the reaction, and balances the negative charge of the framework. The as-obtained samples were characterized using single-crystal and powder X-ray diffraction and TGA. Interestingly, 1 can selectively capture cationic dye molecules from mixtures of dye molecules containing different charges in aqueous solutions. Furthermore, 1 exhibits a different adsorption efficiency toward different cationic dyes (crystal violet, rhodamine B, safranine T and methylene blue). Among the studied dyes, methylene blue has a higher adsorption efficiency in comparison to the others. Thus, complex 1 could serve as a good candidate material for the selective removal of cationic dyes during the treatment of wastewater.

  20. Low half-wave voltage Y-branch electro-optic polymer modulator based on side-chain polyurethane-imide

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Wang, Long-De; Li, Ruo-Zhou; Zhang, Qiang; Zhang, Tong

    2016-06-01

    A Y-branch electro-optic (EO) polymer modulator has been designed and fabricated. High performance side-chain polyurethane-imide (PUI) with a high EO coefficient of larger than 50 pm/V and a moderate glass-transition temperature (Tg) of 206∘C is used as EO polymer core layer of the modulator. The fabricated phase modulator exhibits a low half-wave voltage of 1.94 V at 1550 nm in single arm modulation with 1 cm EO interaction length and 2 cm total length. The results show that the modulator fabricated by side-chain PUI EO materials possesses potential applications in low driving voltage and low cost optical systems.

  1. Cathode including a non fluorinated linear chain polymer as the binder, method of making the cathode, and lithium electrochemical cell containing the cathode

    NASA Astrophysics Data System (ADS)

    Plichta, Edward J.; Salomon, Mark

    1986-08-01

    A cathode suitable for use in a lithium electrochemical cell is made from a mixture of active cathode material, carbon, and non fluorinated linear chain polymer by a method including the following steps: (1) dissolving the non fluorinated linear polymer in a non polar solvent at a temperature near the melting point of the polymer; (2) adding the active cathode material and carbon and evaporating the solvent; and (3) grinding the dried mixture into a fine powder and making it into a cathode by pressing the powdered mixture onto both sides of an expanded metal screen and then cutting to the desired dimensions. The cathode can be combined with lithium as the anode and a solution of 0.8 mol/cu dm LiAlCl4 in a mixed organic solvent of 24 mass percent 4-butyrolactone in 1, 2 dimethoxyethane as the electrolyte to provide a mechanically stable, relatively inexpensive lithium electrochemical cell having good cell performance.

  2. Colloidal stability dependence on polymer adsorption through disjoining pressure isotherms.

    PubMed

    Goicochea, A Gama; Nahmad-Achar, E; Pérez, E

    2009-04-09

    The disjoining pressure of polymers confined by colloidal walls was computed using dissipative particle dynamics simulations at constant chemical potential, volume, and temperature. The polymers are able to adsorb on the surfaces according to two models. In the so-called surface-modifying polymers, all monomers composing the chains have the same affinity for the substrate, whereas for the end-grafted polymer only the monomer at one of the ends of the polymer molecule adsorbs on the colloidal surface, resembling the behavior of dispersing agents. We find that these adsorption models yield markedly different disjoining pressure isotherms, which in turn predict different stability conditions for the colloidal dispersion. Our results show that for end-grafted polymers, a larger degree of polymerization at the same monomer concentration leads to better stability than for the surface-modifying ones. But also the unbound monomers of the surface-modifying type dominate over both kinds of polymers at large surface distances. The origin of these differences when the chemical nature of monomers is the same, and molecular weight and polymer concentration are used to characterize colloidal stability, is found to be mainly entropic.

  3. Cadmium and zinc chain and cluster-based layered coordination polymers prepared from flexible-arm aromatic ortho-dicarboxylic acids and 4-pyridylnicotinamide

    NASA Astrophysics Data System (ADS)

    Kraft, Peter E.; Uebler, Jacob W.; LaDuca, Robert L.

    2013-04-01

    Hydrothermal reaction of a d10-metal nitrate salt, a flexible-arm aromatic ortho-dicarboxylic acid, and 4-pyridylnicotinamide (4-pna) afforded four new crystalline coordination polymers, which were characterized by single-crystal X-ray diffraction. [Cd(Hhmph)(nic)(H2O)2]n (1, hmph = homophthalate, nic = nicotinate) is a 1-D coordination polymer chain compound whose nic ligands were generated in situ via 4-pna hydrolysis. Addition of base and a shorter reaction duration afforded [Cd(hmph)(4-pna)]n (2), which has dinuclear [Cd2(hmph)2] dimers linked into a 1-D ladder polymer via 4-pna ligands. A similar chain structure, albeit with a different hmph binding mode, is seen in [Zn(hmph)(4-pna)]n (3). {[Zn2(phda)2(4-pna)2(H2O)]ṡH2O}n (4, phda = 1,2-phenylenediacetate) has both anti-syn bridged [Zn2(OCO)2] ring dimers and [Zn2(OCO)4] paddlewheel dimers, linked into a layered coordination polymer by dipodal 4-pna ligands. Luminescent properties of these new materials are also presented.

  4. Exact solution of the thermodynamics and size parameters of a polymer confined to a lattice of finite size: Large chain limit

    SciTech Connect

    Snyder, Chad R. Guttman, Charles M.; Di Marzio, Edmund A.

    2014-01-21

    We extend the exact solutions of the Di Marzio-Rubin matrix method for the thermodynamic properties, including chain density, of a linear polymer molecule confined to walk on a lattice of finite size. Our extensions enable (a) the use of higher dimensions (explicit 2D and 3D lattices), (b) lattice boundaries of arbitrary shape, and (c) the flexibility to allow each monomer to have its own energy of attraction for each lattice site. In the case of the large chain limit, we demonstrate how periodic boundary conditions can also be employed to reduce computation time. Advantages to this method include easy definition of chemical and physical structure (or surface roughness) of the lattice and site-specific monomer-specific energetics, and straightforward relatively fast computations. We show the usefulness and ease of implementation of this extension by examining the effect of energy variation along the lattice walls of an infinite rectangular cylinder with the idea of studying the changes in properties caused by chemical inhomogeneities on the surface of the box. Herein, we look particularly at the polymer density profile as a function of temperature in the confined region for very long polymers. One particularly striking result is the shift in the critical condition for adsorption due to surface energy inhomogeneities and the length scale of the inhomogeneities; an observation that could have important implications for polymer chromatography. Our method should have applications to both copolymers and biopolymers of arbitrary molar mass.

  5. Structure, scattering patterns and phase behavior of polymer nanocomposites with nonspherical fillers

    SciTech Connect

    Hall, Lisa M; Schweizer, Kenneth S

    2010-01-01

    Polymer nanocomposites made with carbon nanotubes, clay platelets, laponite disks and other novel nonspherical fillers have been the focus of many recent experiments. However, the effects of nanoparticle shape on statistical structure, polymer-mediated effective interactions, scattering patterns, and phase diagrams are not well understood. We extend and apply the polymer reference interaction site model liquid state theory to study the equilibrium properties of pseudo one-, two- and threedimensional particles (rod, disk, cube) of modest steric anisotropy and fixed space-filling volume in a dense adsorbing homopolymer melt up to relatively high volume fractions. The second virial coefficient, nanoparticle potential-of-mean force, osmotic compressibilities, and isotropic spinodal demixing boundaries have been determined. The entropic depletion attraction between nanoparticles is dominant for weakly adsorbing polymer, while strongly adsorbing chains induce a bridging attraction. Intermediate interfacial cohesion results in the formation of a steric stabilizing adsorbed polymer layer around each nanoparticle, which can partially damp inter-filler collective order on various length scales and increase order on an averaged length scale. The details of depletion, stabilization, or bridging behavior are shape-dependent and often, but not always, trends are monotonic with increasing filler dimensionality. Distinctive nanoparticle shape-dependent low angle features are predicted for the collective polymer structure factor associated with competing macrophase fluctuations and microphase-like ordering. The influence of nonzero mixture compressibility on the scattering profiles is established.

  6. Film morphology and orientation of amino silicone adsorbed onto cellulose substrate

    NASA Astrophysics Data System (ADS)

    Xu, Yingjun; Yin, Hong; Yuan, Shenfeng; Chen, Zhirong

    2009-07-01

    A series of amino silicones with different amino values were synthesized and adsorbed onto surfaces of cotton fibers and cellulose substrates. The film morphology, hydrophobic properties and surface composition of the silicones are investigated and characterized by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), contact angle measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared (ATR-IR). The results of the experiments indicate that the amino silicone can form a hydrophobic film on both cotton fibers and cellulose substrates and reduce the surface roughness significantly. Furthermore, the roughness becomes smaller with an increase in the amino value. All these results suggest that the orientation of amino silicone molecule is with the amino functional groups of amino silicone molecule adsorbed onto the cellulose interface while the main polymer chains and the hydrophobic Si-CH 3 groups extend toward the air.

  7. Facile Isolation of Adsorbent-Free Long and Highly-Pure Chirality-Selected Semiconducting Single-Walled Carbon Nanotubes Using A Hydrogen-bonding Supramolecular Polymer

    NASA Astrophysics Data System (ADS)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2015-12-01

    The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only the chiral- or chemically-purity while sacrificing the sem-SWNT intrinsic structural identities by applying strong ultra-sonication and/or chemical modifications. Toward the ultimate purification of the sem-SWNTs, here we report a mild-conditioned extraction of the sem-SWNTs using removable supramolecular hydrogen-bonding polymers (HBPs) that are composed of dicarboxylic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selective extraction. Replacing conventional strong sonication techniques by a simple shaking using HPBs was found to provide long sem-SWNTs (>2.0 μm) with a very high D/G ratio, which was determined by atomic force microscopy observations. The HBPs were readily removed from the nanotube surfaces by an outer stimulus, such as a change in the solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to propose possible structures for the HBP-wrapped sem-SWNTs, furthermore, the mechanism of the chiral selectivity for the sorted sem-SWNTs is well explained by the relationship between the molecular surface area and mass of the HBP/SWNT composites.

  8. Multiple dynamic regimes in colloid-polymer dispersions: New insight using X-ray photon correlation spectroscopy

    SciTech Connect

    Srivastava, Sunita; Kishore, Suhasini; Narayanan, Suresh; Sandy, Alec R.; Bhatia, Surita R.

    2015-12-01

    We present an X-ray photon correlation spectros- copy (XPCS) study of dynamic transitions in an anisotropic colloid-polymer dispersion with multiple arrested states. The results provide insight into the mechanism for formation of repulsive glasses, attractive glasses, and networked gels of col- loids with weakly adsorbing polymer chains. In the presence of adsorbing polymer chains, we observe three distinct regimes: a state with slow dynamics consisting of finite particles and clusters, for which interparticle interactions are predominantly repulsive; a second dynamic regime occurring above the satu- ration concentration of added polymer, in which small clusters of nanoparticles form via a short-range depletion attraction; and a third regime above the overlap concentration in which dynamics of clusters are independent of polymer chain length. The observed complex dynamic state diagram is primarily gov- erned by the structural reorganization of a nanoparticle cluster and polymer chains at the nanoparticle-polymer surface and in the concentrated medium, which in turn controls the dynamics of the dispersion

  9. Effect of the polymer chain length of poly(N-isopropylacrylamide) on the temperature-responsive phase transition behavior of its conjugates with [60]fullerene.

    PubMed

    Uchida, Katsumi; Tamura, Atsushi; Yajima, Hirofumi

    2010-03-01

    In order to develop biomedical materials with specific functionalities, thermoresponsive conjugates [poly(N-isopropylacrylamide)-C(60) (PIPAAm-C(60)) ]of [60]fullerene (C(60)) and PIPAAm with two different polymer chain lengths (4 and 20 kDa) were synthesized by atom transfer radical polymerization. The effects of the polymer chain length on the temperature-responsive phase transition behavior of the synthetic PIPAAm-C(60) conjugates were probed by means of various physicochemical techniques. The coexistence of unimers and molecular assemblies of PIPAAm-C(60) was observed by gel permeation chromatography and dynamic light scattering studies in two PIPAAm-C(60) aqueous solutions below their lower critical solution temperatures (LCSTs). Additionally, below their LCSTs, differences in PIPAAm chain length gave rise to changes in the composition of the unimers and molecular assemblies. In response to temperature, the absorbance of the PIPAAm-C(60) aqueous solution changed according to a two-step behavior profile. Increasing temperature during the primary stage, where a change in the absorbance of the PIPAAm-C(60) aqueous solution took place, did not change the transition temperature, regardless of the solution concentration of PIPAAm-C(60). This absorbance change was associated with the phase transition of the molecular assemblies of PIPAAm-C(60). However, at the second stage, the transition temperature shifted to a higher value with the decrease in the concentration of PIPAAm-C(60), in the same manner as free PIPAAm chains. The second change was associated with the phase transition of the unimeric PIPAAm-C(60). Differences in PIPAAm chain length gave rise to the change in the phase transition behavior of PIPAAm-C(60) aqueous solution. Therefore, the chain length of PIPAAm was found to be a predominant factor involved in the solution characteristics of PIPAAm-C(60). Consequently, the PIPAAm-C(60) is expected to be an intelligent biomaterial possessing heat

  10. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  11. Dispersion of carbon nanotubes in organic solvent by commercial polymers with ethylene chains: Experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Shigeta, Masahiro; Kamiya, Katsumasa; Uejima, Mitsugu; Okada, Susumu

    2015-03-01

    We demonstrate the possible candidate dispersion agents that can uniformly disperse carbon nanotubes (CNTs) into organic solvent, from among commercially available polymers. We find that CNTs were well dispersed into dimethylacetamide with the use of polystyrene, poly(vinyl chloride), and poly(vinyl pyrrolidone) as dispersion agents. Theoretical calculations revealed that the dispersibility of these polymers arises from the moderate strength and preferential directionality of the interactions between the CNTs and the polymers.

  12. Synthesis and characterization of the core-shell magnetic molecularly imprinted polymers (Fe₃O₄@MIPs) adsorbents for effective extraction and determination of sulfonamides in the poultry feed.

    PubMed

    Kong, Xuan; Gao, Ruixia; He, Xiwen; Chen, Langxing; Zhang, Yukui

    2012-07-06

    In this study, we present a general method to prepare the core-shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe₃O₄@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe²⁺ and Fe³⁺ in an ammonia solution first. Silica was then coated on the Fe₃O₄ NPs using a sol-gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe₃O₄ surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe₃O₄@SiO₂ by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe₃O₄@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe₃O₄@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe₃O₄@MIPs to SMZ was 344.8 μg g⁻¹. The selectivity of the obtained Fe₃O₄@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe₃O₄@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD

  13. Effects of topology on the adsorption of singly tethered ring polymers to attractive surfaces.

    PubMed

    Li, Bing; Sun, Zhao-Yan; An, Li-Jia

    2015-07-14

    We investigate the effect of topology on the equilibrium behavior of singly tethered ring polymers adsorbed on an attractive surface. We focus on the change of square radius of gyration Rg(2), the perpendicular component Rg⊥(2) and the parallel component Rg‖(2) to the adsorbing surface, the mean contacting number of monomers with the surface , and the monomer distribution along z-direction during transition from desorption to adsorption. We find that both of the critical point of adsorption εc and the crossover exponent ϕ depend on the knot type when the chain length of ring ranges from 48 to 400. The behaviors of Rg(2), Rg⊥(2), and Rg‖(2) are found to be dependent on the topology and the monomer-surface attractive strength. At weak adsorption, the polymer chains with more complex topology are more adsorbable than those with simple topology. However, at strong adsorption, the polymer chains with complex topology are less adsorbable. By analyzing the distribution of monomer along z-direction, we give a possible mechanism for the effect of topology on the adsorption behavior.

  14. Low-band-gap conjugated polymers of dithieno[2,3-b:7,6-b]carbazole and diketopyrrolopyrrole: effect of the alkyl side chain on photovoltaic properties.

    PubMed

    Deng, Yunfeng; Chen, Yagang; Liu, Jian; Liu, Lihui; Tian, Hongkun; Xie, Zhiyuan; Geng, Yanhou; Wang, Fosong

    2013-06-26

    Four donor–acceptor (D–A) conjugated polymers of dithieno[2,3-b;7,6-b]carbazole (DTC) and diketopyrrolopyrrole, which have different alkyls on the nitrogen atom in the DTC unit and are named as P-C8C8, P-C5C5, P-C12, and P-C10, respectively, have been synthesized for studying the effect of the alkyl side chains on the optoelectronic properties of the polymers. All polymers are soluble in various organic solvents and exhibit identical optical band gaps (E(g)(opt)) of ~1.3 eV and highest occupied molecular orbital energy levels of ~−5.1 eV. Organic thin-film transistors and bulk heterojunction polymer solar cells (BHJ PSCs) with phenyl-C(71)-butyric acid methyl ester (PC(71)BM) as the electron-accepting material were fabricated via solution spin-casting. Compared to the polymers substituted by branched alkyl chains, the polymers with straight alkyl chains show higher hole mobility. Of these polymers, P-C10 exhibits the highest field effect mobility up to 0.011 cm(2)/V·s. The alkyl chain on the DTC unit has a strong impact on the film morphology of polymer:PC(71)BM blends. Severe phase separation was found for polymers containing branched alkyl chains, and those with straight alkyl chains formed uniform films featuring fine phase separation. An open-circuit voltage (V(oc)) of 0.72 V, a short-circuit current density (J(sc)) of 13.4 mA/cm(2), a fill factor (FF) of 62%, and a power conversion efficiency (PCE) of 5.9% were demonstrated for BHJ PSCs based on the P-C10:PC(71)BM [1:3 (w/w)] blend film.

  15. Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 4. Synthesis of Amorphous and Side Chain Liquid Crystal AB Block Copolymers

    DTIC Science & Technology

    1992-05-01

    Metathesis Polymerization. 4. Synthesis of C N00014-89-JI542 Amorphous and Side Chain Liquid Crystal AB Block Copolym rs 6. AUTHOR(S) Zen Komiya, Coleen ...Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pugh: and Richard R. Schrock* Submitted to Macromolecules F r fCarnegie Mellon University...Amorphous and Side Chain Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pught, and Richard R. Schrock* Contribution from Department of Chemistry 6

  16. The Dependence of Strength in Plastics upon Polymer Chain Length and Chain Orientation: An Experiment Emphasizing the Statistical Handling and Evaluation of Data.

    ERIC Educational Resources Information Center

    Spencer, R. Donald

    1984-01-01

    Describes an experiment (using plastic bags) designed to give students practical understanding on using statistics to evaluate data and how statistical treatment of experimental results can enhance their value in solving scientific problems. Students also gain insight into the orientation and structure of polymers by examining the plastic bags.…

  17. High performance polymer electrolytes based on main and side chain pyridine aromatic polyethers for high and medium temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Geormezi, M.; Chochos, C. L.; Gourdoupi, N.; Neophytides, S. G.; Kallitsis, J. K.

    Novel aromatic polyether type copolymers bearing side chain polar pyridine rings as well as combination of main and side chain pyridine units have been evaluated as potential polymer electrolytes for proton exchange membrane fuel cells (PEMFCs). The advanced chemical and physicochemical properties of these new polymers with their high oxidative stability, mechanical integrity and high glass transition temperatures (T g's up to 270 °C) and decomposition temperatures (T d's up to 480 °C) make them promising candidates for high and medium temperature proton exchange membranes in fuel cells. These copolymers exhibit adequate proton conductivities up to 0.08 S cm -1 even at moderate phosphoric acid doping levels. An optimized terpolymer chemical structure has been developed, which has been effectively tested as high temperature phosphoric acid imbibed polymer electrolyte. MEA prepared out of the novel terpolymer chemical structure is approaching state of the art fuel cell operating performance (135 mW cm -2 with electrical efficiency 45%) at high temperatures (150-180 °C) despite the low phosphoric acid content (<200 wt%) and the low platinum loading (ca. 0.7 mg cm -2). Durability tests were performed affording stable performance for more than 1000 h.

  18. Logic-Controlled Radical Polymerization with Heat and Light: Multiple-Stimuli Switching of Polymer Chain Growth via a Recyclable, Thermally Responsive Gel Photoredox Catalyst.

    PubMed

    Chen, Mao; Deng, Shihong; Gu, Yuwei; Lin, Jun; MacLeod, Michelle J; Johnson, Jeremiah A

    2017-02-15

    Strategies for switching polymerizations between "ON" and "OFF" states offer new possibilities for materials design and fabrication. While switching of controlled radical polymerization has been achieve using light, applied voltage, allosteric effects, chemical reagents, pH, and mechanical force, it is still challenging to introduce multiple external switches using the same catalyst to achieve logic gating of controlled polymerization reactions. Herein, we report an easy-to-synthesize thermally responsive organo-/hydro-gel that features covalently bound 10-phenylphenothiazine (PTH). With this "Gel-PTH", we demonstrate switching of controlled radical polymerization reactions using temperature "LOW"/"HIGH", light "ON"/"OFF", and catalyst presence "IN"/"OUT". Various iniferters/initiators and a wide range of monomers including acrylates, methacrylates, acrylamides, vinyl esters, and vinyl amides were polymerized by RAFT/iniferter and ATRP methods using Gel-PTH and a readily available compact fluorescent light (CFL) source. In all cases, polymer molar masses increased linearly with conversion, and narrow molar mass distributions were obtained. To further highlight the utility of Gel-PTH, we achieved "AND" gating of controlled radical polymerization wherein various combinations of three stimuli were required to induce polymer chain growth. Finally, block copolymer synthesis and catalyst recycling were demonstrated. Logic-controlled polymerization with Gel-PTH offers a straightforward approach to achieve multiplexed external switching of polymer chain growth using a single catalyst without the need for addition of exogenous reagents.

  19. Phase and orientational ordering of low molecular weight rod molecules in a quenched liquid crystalline polymer matrix with mobile side chains

    NASA Astrophysics Data System (ADS)

    Gutman, Lorin; Cao, Jianshu; Swager, Tim M.

    2004-06-01

    We study the phase diagram and orientational ordering of guest liquid crystalline (LC) rods immersed in a quenched host made of a liquid crystalline polymer (LCP) matrix with mobile side chains. The LCP matrix lies below the glass transition of the polymer backbone. The side chains are mobile and can align to the guest rod molecules in a plane normal to the local LCP chain contour. A field theoretic formulation for this system is proposed and the effects of the LCP matrix on LC ordering are determined numerically. We obtain simple analytical equations for the nematic/isotropic phase diagram boundaries. Our calculation show a nematic-nematic (N/N) first order transition from a guest stabilized to a guest-host stabilized region and the possibility of a reentrant transition from a guest stabilized nematic region to a host only stabilized regime separated by an isotropic phase. A detailed study of thermodynamic variables and interactions on orientational ordering and phases is carried out and the relevance of our predictions to experiments and computer simulations is presented.

  20. Organometallic Polymers.

    ERIC Educational Resources Information Center

    Carraher, Charles E., Jr.

    1981-01-01

    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  1. Biomimetic polymers responsive to a biological signaling molecule: nitric oxide triggered reversible self-assembly of single macromolecular chains into nanoparticles.

    PubMed

    Hu, Jinming; Whittaker, Michael R; Duong, Hien; Li, Yang; Boyer, Cyrille; Davis, Thomas P

    2014-07-21

    Novel nitric oxide (NO) responsive monomers (NAPMA and APUEMA) containing o-phenylenediamine functional groups have been polymerized to form NO-responsive macromolecular chains as truly biomimetic polymers. Upon exposure to NO--a ubiquitous cellular signaling molecule--the NAPMA- and APUEMA-labeled thermoresponsive copolymers exhibited substantial changes in solubility, clearly characterized by tuneable LCST behavior, thereby inducing self-assembly into nanoparticulate structures. Moreover, the NO-triggered self-assembly process in combination with environmentally sensitive fluorescence dyes could be employed to detect and image endogenous NO.

  2. Enantioselective cyclopolymerization of 1,5-hexadiene catalyzed by chiral zirconocenes: A novel strategy for the synthesis of optically active polymers with chirality in the main chain

    SciTech Connect

    Coates, G.W.; Waymouth, R.M. )

    1993-01-13

    Enantioselective cyclopolymerization represents a novel strategy for the synthesis of optically active main-chain chiral polymers. Cyclopolymerization of 1,5-hexadiene using the optically active catalyst precursor, (R,R)-(EBTHI)ZrBINOL ((R,R)-1) [EBTHI = ethylene-1,2-bis([eta][sup 5]-4,5,6,7-tetrahydro-1-indenyl); BINOL = 1,1[prime]-bi-2-naphtholate], yields optically active poly(methylene-1,3-cyclopentane) (PMCP) with a molar optical rotation of [[Phi

  3. Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 1. Influence of Molecular Weight, Polydispersity, and Flexible Spacer Length (n=2-8) on the Thermotropic behavior of the Resulting Polymers

    DTIC Science & Technology

    1992-03-31

    Budget. Paperwork peduc t ~O l~oect(0104. 01111). Wasnhinqtol Dic 20oi 4- TITLE AND SUBTITLE Ap.i FUNIN N92_UMBcncaRpotS1 Synthesis of Side Chain...metathesis polymerization of 5-carbo(n-[(4’-methoxy-4- biphenylyl)oxy]alkyl)bicyclo[2.2.1]hept-2-ene (1-n, n=2-8) by Mo(CH- t -Bu)(NAr) (0- t -Bu)2(Ar=2,6...C6H3- t -Pr 2) is described. Polymers with degrees of polymeri- zation from 5 to 100 and narrow molecular weight distributions (Mw/Mnz1.05-1.24) were

  4. Polymeric adsorbent for removing toxic proteins from blood of patients with kidney failure.

    PubMed

    Davankov, V; Pavlova, L; Tsyurupa, M; Brady, J; Balsamo, M; Yousha, E

    2000-02-28

    A hypercrosslinked styrenic polymer with an enhanced proportion of mesopores in the range 2-20 nm has been developed. The principle of the synthesis consists of the suspension polymerization of divinylbenzene (or copolymerization of styrene with divinylbenzene) in the presence of a porogen that is a theta-solvent for polystyrene. On the scale of thermodynamic affinity, theta-solvents occupy a border position between good solvents and precipitating media for the growing polymer chains. In this case, microphase separation takes place during the final stages of the polymerization process. The polymer was shown to adsorb 93-98% of beta2-microglobulin from the blood or plasma of patients with chronic kidney failure. At the same time, large essential proteins, like albumin, are not removed to a significant extent, obviously, due to the size-exclusion effect and the difference in the hydrophobicity of the proteins. By replacing surface exposed pendant vinyl groups of the polymer with hydrophilic functional groups, the material was made hemocompatible, according to the standard battery of biocompatibility tests required by ISO 10993 guidelines. No adverse effects such as fever or hypotension were noted in dogs in direct hemoperfusion experiments with the polymer.

  5. Membrane Perturbation Induced by Interfacially Adsorbed Peptides

    PubMed Central

    Zemel, Assaf; Ben-Shaul, Avinoam; May, Sylvio

    2004-01-01

    The structural and energetic characteristics of the interaction between interfacially adsorbed (partially inserted) α-helical, amphipathic peptides and the lipid bilayer substrate are studied using a molecular level theory of lipid chain packing in membranes. The peptides are modeled as “amphipathic cylinders” characterized by a well-defined polar angle. Assuming two-dimensional nematic order of the adsorbed peptides, the membrane perturbation free energy is evaluated using a cell-like model; the peptide axes are parallel to the membrane plane. The elastic and interfacial contributions to the perturbation free energy of the “peptide-dressed” membrane are evaluated as a function of: the peptide penetration depth into the bilayer's hydrophobic core, the membrane thickness, the polar angle, and the lipid/peptide ratio. The structural properties calculated include the shape and extent of the distorted (stretched and bent) lipid chains surrounding the adsorbed peptide, and their orientational (C-H) bond order parameter profiles. The changes in bond order parameters attendant upon peptide adsorption are in good agreement with magnetic resonance measurements. Also consistent with experiment, our model predicts that peptide adsorption results in membrane thinning. Our calculations reveal pronounced, membrane-mediated, attractive interactions between the adsorbed peptides, suggesting a possible mechanism for lateral aggregation of membrane-bound peptides. As a special case of interest, we have also investigated completely hydrophobic peptides, for which we find a strong energetic preference for the transmembrane (inserted) orientation over the horizontal (adsorbed) orientation. PMID:15189858

  6. Brownian dynamics simulations of flowing isolated polymer molecules in solution near surfaces

    NASA Astrophysics Data System (ADS)

    Chopra, Manish

    Brownian dynamics simulations have been shown to give accurate predictions of the molecular conformations and rheology of polymers (DNA in particular) in extensional and shear flow. We extend these Brownian dynamics methods to include the interactions of polymers with non- adsorbing and irreversibly adsorbing solid surfaces during flow. We develop mathematical tools and statistical analyses and apply them to the case of a simple steady shear flow (plane Couette) inside a confined geometry and to the time-dependent axisymmetric flow created by the action of a drying droplet. Under shearing flow (plane Couette) there is a depletion layer near the wall whose thickness decreases with increasing shear rate, because of the compression of the chain in the shear gradient direction. Relative to the bulk, the molecular stretch in the direction of the flow is reduced near the wall, despite the increase in molecular alignment. We also demonstrate that the wall interferes with the molecular tumbling in shear flow. In the case of a perfectly adsorbing wall, in the process of adsorbing, the molecule becomes more stretched than in the bulk flow at the same shear rate. We also report a propensity for the polymer to affix to the surface sequentially starting at one end, due to the tendency in a random-walk polymer for a free end to lie at the periphery. The more highly stretched molecules tend to be those that adsorbed more perfectly in sequence. In the drying droplet flow field, the degree of stretch obtainable is substantially less than can be obtained by deposition from a simple uniform shearing flow. Statistical analysis reveals that the inefficiency of stretching in the drying droplet results from the presence of a velocity component normal to the surface, which reduces the time available for the chain to unravel sequentially as it adsorbs onto the surface.

  7. Mapping of continuum and lattice models for describing the adsorption of an ideal chain anchored to a planar surface

    NASA Astrophysics Data System (ADS)

    Gorbunov, A. A.; Skvortsov, A. M.; van Male, J.; Fleer, G. J.

    2001-03-01

    An ideal polymer chain anchored to a planar surface is considered by using both lattice and continuum model approaches. A general equation relating the lattice and continuum model adsorption interaction parameters is derived in a consistent way by substituting the exact continuum solution for the free chain end distribution function into the lattice model boundary condition. This equation is not mathematically exact but provides excellent results. With the use of this relation the quantitative equivalence between lattice and continuum results was demonstrated for chains of both infinite and finite length and for all three regimes corresponding to attractive, repulsive and adsorption-threshold energy of polymer-surface interaction. The obtained equations are used to discuss the distribution functions describing the tail of an anchored macromolecule and its adsorbed parts. For the tail-related properties the results are independent of the microscopic details of the polymer chain and the adsorbing surface. One interesting result obtained in the vicinity of adsorption threshold point is a bimodal tail length distribution function, which manifests chain populations with either tail or loop dominance. The properties related to the number of surface contacts contain, apart from universal scaling terms, also a nonuniversal factor depending on microscopic details of polymer-surface interaction. We derived an equation for calculating this nonuniversal factor for different lattice models and demonstrated excellent agreement between the lattice results and the continuum model.

  8. A roundabout approach to control morphological orientation and solar-cell performance by modulating side-chain branching position in benzodithiophene-based polymers.

    PubMed

    Lee, Kyu Cheol; Song, Seyeong; Lee, Junghoon; Kim, Dong Suk; Kim, Jin Young; Yang, Changduk

    2015-04-27

    To be meaningful to guide the rational design of novel high-performance conjugated semiconductors, we prepared three benzo[1,2-b:4,5-b']dithiophene (BDT)-based polymers by systematically moving the branching point of the alkyl chain. The effect of side-chain engineering was thoroughly investigated by a range of techniques. We demonstrate that a subtle change in the branching position in the BDT core can have a critical impact on polymer packing and preferential backbone orientation in thin films; copolymers made from BDT and thieno[3,4-c]pyrrole-4,6-dione units (TPD) adopt more of a face-on orientation as the branching point is shifted closer to the backbone, which can be correlated with a dramatic difference in solar-cells performance. The high short-circuit current density (11.6 mA cm(-2) ) for the copolymer with one carbon atom between the alkoxylated oxygen atom and the branching point results from its predominantly face-on orientation and smoother surface in thin films, which results in power conversion efficiencies as high as 4.56 %.

  9. A hybrid method for predicting the microstructure of polymers with complex architecture: combination of single-chain simulation with density functional theory.

    PubMed

    Cao, Dapeng; Jiang, Tao; Wu, Jianzhong

    2006-04-28

    A hybrid method is proposed to investigate the microstructure of various polymeric fluids confined between two parallel surfaces. The hybrid method combines a single-chain Monte Carlo (MC) simulation for the ideal-gas part of the Helmholtz energy and a density functional theory (DFT) for the excess part that arises from nonbonded intersegment interactions. The latter consists of a modified fundamental measure theory for excluded-volume effect, the first-order thermodynamics perturbation theory for chain connectivity, and a mean-field approximation for the van der Waals attraction. In comparison with a conventional DFT, the hybrid method avoids calculation of the time-consuming recursive functions and is directly applicable to polymers with arbitrary molecular architecture. Its numerical performance has been validated by extensive comparisons with MC data for the density distributions of totally flexible, semiflexible, or rigid polymers and those with starlike architecture. Special attention is also given to the formation of a nematic monolayer by rigid molecules laying perpendicular to a planar surface. The hybrid method predicts the surface pressure versus surface coverage in good agreement with experiment.

  10. Main-chain supramolecular polymers based on orthogonal benzo-21-crown-7/secondary ammonium salt and terpyridine/metal ion recognition motifs.

    PubMed

    Tian, Yu-Kui; Wang, Feng

    2014-02-01

    Orthogonal self-assembly of multiple components represents an efficient strategy to afford hierarchical and multifunctional assemblies. Here, we demonstrate the orthogonal recognition behaviors between benzo-21-crown-7/secondary ammonium salt and terpyridine/metal ions (Fe(2+) or Zn(2+) ) recognition motifs. Main-chain supramolecular polymers are subsequently achieved via "one-pot" mixing of the three monomers together (heteroditopic monomer 1, homoditopic secondary ammonium salt monomer 2, and Fe(BF4 )2 •6H2 O or Zn(OTf)2 ), which are confirmed by (1) H NMR, UV-Vis, DOSY, and viscosity measurements. Moreover, different metal ions (Fe(2+) or Zn(2+) ) exert considerable effects on the size of the resulting supramolecular polymers. Integration of two different types of non-covalent interactions renders dynamic and responsive properties for the resulting supramolecular polymers, as triggered by a variety of external stimuli such as temperature, potassium cation, as well as stronger chelating ligands. Therefore, the current work is a prerequisite for the future application of such orthogonal assemblies as intelligent supramolecular materials.

  11. Photoinduced dichroism and optical anisotropy in a liquid-crystalline azobenzene side chain polymer caused by anisotropic angular distribution of trans and cis isomers

    NASA Astrophysics Data System (ADS)

    Blinov, Lev M.; Kozlovsky, Mikhail V.; Ozaki, Masanori; Skarp, Kent; Yoshino, Katsumi

    1998-10-01

    Photochromism has been studied for two comb-like liquid-crystalline copolymers (I) and (II) containing azobenzene chromophores in their side chains. In a smectic glass phase of both copolymers, upon short-time irradiation by UV light, long-living cis isomers are observed. Both copolymers manifest the photoinduced anisotropy, the physical mechanisms of which seem to be quite different. In spin-coated films of polymer (II), the origin of the anisotropy is a strong stable dichroism, which is due to an enrichment and depletion of the chosen angular direction, correspondingly, with trans and cis isomers of the azobenzene chromophores. Polymer (I) manifests no dichroism at all, and its induced optical anisotropy may be accounted for by a rather slow chromophore reorientation. In copolymer (II) a considerable reorientation of the mesogenic groups also occurs as a secondary phenomenon at the stage of the cis isomer formation only. This observation shed more light on the general process of the light-induced molecular reorientation in polymers, liquid crystals, and Langmuir-Blodgett films, which is of great importance for holographic information recording.

  12. Sedimentation of Colloidal Particles through a Polymer Solution

    NASA Astrophysics Data System (ADS)

    Tong, Penger; Ye, Xi; Ackerson, Bruce J.

    1997-03-01

    We report recent sedimentation measurements of colloidal particles through a polymer solution. The colloidal particles used were sterically stabilized CaCO3 suspended in decane and the polymer was hydrogenated polyisoprene. Our previous light and neutron scattering measurements have shown that the polymer chains do not adsorb onto the colloidal surfaces. Using a commercial ultracentrifuge, we measured the sedimentation rate of the colloidal particles, from which the microscopic viscosity experienced by the particles was obtained at different polymer concentration C_p. The experiment reveals that at low colloid concentration φ_c, the particles feel the single-chain viscosity when their size Rh is smaller than the correlation length ξ of the polymer solution. The particles experience the macroscopic viscosity of the polymer solution when Rh >> ξ. The transition for the particles to feel the macroscopic viscosity is well described by a switch function f_c(C_p)=exp[-(C_0/C_p)^α], which can be written as a function of R_h/ξ. It is found that f_c(C_p) is independent of the polymer molecular weight. As φc increases, the colloidal particles feel more and more depletion attraction and their settling velocity increases with increasing C_p.

  13. Side-Chain Isomerization on an n-type Organic Semiconductor ITIC Acceptor Makes 11.77% High Efficiency Polymer Solar Cells.

    PubMed

    Yang, Yankang; Zhang, Zhi-Guo; Bin, Haijun; Chen, Shanshan; Gao, Liang; Xue, Lingwei; Yang, Changduk; Li, Yongfang

    2016-11-16

    Low bandgap n-type organic semiconductor (n-OS) ITIC has attracted great attention for the application as an acceptor with medium bandgap p-type conjugated polymer as donor in nonfullerene polymer solar cells (PSCs) because of its attractive photovoltaic performance. Here we report a modification on the molecular structure of ITIC by side-chain isomerization with meta-alkyl-phenyl substitution, m-ITIC, to further improve its photovoltaic performance. In a comparison with its isomeric counterpart ITIC with para-alkyl-phenyl substitution, m-ITIC shows a higher film absorption coefficient, a larger crystalline coherence, and higher electron mobility. These inherent advantages of m-ITIC resulted in a higher power conversion efficiency (PCE) of 11.77% for the nonfullerene PSCs with m-ITIC as acceptor and a medium bandgap polymer J61 as donor, which is significantly improved over that (10.57%) of the corresponding devices with ITIC as acceptor. To the best of our knowledge, the PCE of 11.77% is one of the highest values reported in the literature to date for nonfullerene PSCs. More importantly, the m-ITIC-based device shows less thickness-dependent photovoltaic behavior than ITIC-based devices in the active-layer thickness range of 80-360 nm, which is beneficial for large area device fabrication. These results indicate that m-ITIC is a promising low bandgap n-OS for the application as an acceptor in PSCs, and the side-chain isomerization could be an easy and convenient way to further improve the photovoltaic performance of the donor and acceptor materials for high efficiency PSCs.

  14. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  15. Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

    2011-01-01

    A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

  16. Decades-Scale Degradation of Commercial, Side-Chain, Fluorotelomer-Based Polymers in Soils and Water

    EPA Science Inventory

    Fluorotelomer-based polymers (FTPs) are a primary product of the jluorotelomer industry, yet the role of commercial FTPs in degrading to form perjluorocarboxylic acids (P FCAs), including perjluorooctanoic acid, and P FCA precursors, remains ill-defined. Here we report on a 376-d...

  17. Quantitative evaluation of interaction force between functional groups in protein and polymer brush surfaces.

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2014-03-18

    To understand interactions between polymer surfaces and different functional groups in proteins, interaction forces were quantitatively evaluated by force-versus-distance curve measurements using atomic force microscopy with a functional-group-functionalized cantilever. Various polymer brush surfaces were systematically prepared by surface-initiated atom transfer radical polymerization as well-defined model surfaces to understand protein adsorption behavior. The polymer brush layers consisted of phosphorylcholine groups (zwitterionic/hydrophilic), trimethylammonium groups (cationic/hydrophilic), sulfonate groups (anionic/hydrophilic), hydroxyl groups (nonionic/hydrophilic), and n-butyl groups (nonionic/hydrophobic) in their side chains. The interaction forces between these polymer brush surfaces and different functional groups (carboxyl groups, amino groups, and methyl groups, which are typical functional groups existing in proteins) were quantitatively evaluated by force-versus-distance curve measurements using atomic force microscopy with a functional-group-functionalized cantilever. Furthermore, the amount of adsorbed protein on the polymer brush surfaces was quantified by surface plasmon resonance using albumin with a negative net charge and lysozyme with a positive net charge under physiological conditions. The amount of proteins adsorbed on the polymer brush surfaces corresponded to the interaction forces generated between the functional groups on the cantilever and the polymer brush surfaces. The weakest interaction force and least amount of protein adsorbed were observed in the case of the polymer brush surface with phosphorylcholine groups in the side chain. On the other hand, positive and negative surfaces generated strong forces against the oppositely charged functional groups. In addition, they showed significant adsorption with albumin and lysozyme, respectively. These results indicated that the interaction force at the functional group level might be

  18. Significant Improvement of Semiconducting Performance of the Diketopyrrolopyrrole-Quaterthiophene Conjugated Polymer through Side-Chain Engineering via Hydrogen-Bonding.

    PubMed

    Yao, Jingjing; Yu, Chenmin; Liu, Zitong; Luo, Hewei; Yang, Yang; Zhang, Guanxin; Zhang, Deqing

    2016-01-13

    Three diketopyrrolopyrrole (DPP)-quaterthiophene conjugated polymers, pDPP4T-1, pDPP4T-2, and pDPP4T-3, in which the molar ratios of the urea-containing alkyl chains vs branching alkyl chains are 1:30, 1:20, and 1:10, respectively, were prepared and investigated. In comparison with pDPP4T without urea groups in the alkyl side chains and pDPP4T-A, pDPP4T-B, and pDPP4T-C containing both linear and branched alkyl chains, thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 exhibit higher hole mobilities; thin-film mobility increases in the order pDPP4T-1 < pDPP4T-2 < pDPP4T-3, and hole mobility of a thin film of pDPP4T-3 can reach 13.1 cm(2) V(-1) s(-1) after thermal annealing at just 100 °C. The incorporation of urea groups in the alkyl side chains also has an interesting effect on the photovoltaic performances of DPP-quaterthiophene conjugated polymers after blending with PC71BM. Blended thin films of pDPP4T-1:PC71BM, pDPP4T-2:PC71BM, and pDPP4T-3:PC71BM exhibit higher power conversion efficiencies (PCEs) than pDPP4T:PC71BM, pDPP4T-A:PC71BM, pDPP4T-B:PC71BM, and pDPP4T-C:PC71BM. The PCE of pDPP4T-1:PC71BM reaches 6.8%. Thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 and corresponding thin films with PC71BM were characterized with AFM, GIXRD, and STEM. The results reveal that the lamellar packing order of the alkyl chains is obviously enhanced for thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3; after thermal annealing, slight inter-chain π-π stacking emerges for pDPP4T-2 and pDPP4T-3. Blends of pDPP4T-1, pDPP4T-2, and pDPP4T-3 with PC71BM show a more pronounced micro-phase separation. These observations suggest that the presence of urea groups may further facilitate the assemblies of these conjugated polymers into nanofibers and ordered aggregation of PC71BM.

  19. Playing with Polymers.

    ERIC Educational Resources Information Center

    Chemecology, 1997

    1997-01-01

    Presents an activity that enables students to gain a better understanding of the importance of polymers. Students perform an experiment in which polymer chains of polyvinyl acetate form crosslinks. Includes background information and discussion questions. (DDR)

  20. Synthesis, surface characterization, and biointeraction studies of low-surface energy side-chain polyetherurethanes

    NASA Astrophysics Data System (ADS)

    Porter, Stephen Christopher

    1999-10-01

    New segmented polyetherurethanes (PEUs) with low surface energy hydrocarbon and fluorocarbon side-chains attached to the polymer hard segments were synthesized. The surface chemistry of solvent cast polymer films was studied using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and dynamic contact angle (DCA) measurements. Increases in the overall density and length of the alkyl side-chains within the PEUs resulted in greater side-chain concentrations at the polymer surface. PEUs bearing long alkyl (> C10 ) and perfluorocarbon side-chains were found to posses surfaces with highly enriched side-chain concentrations relative to the bulk polymer. In PEUs with significant side-chain surface enrichment, the relatively polar hard segment blocks were shown to reside in high concentrations just below the side-chain enriched surface layer. Furthermore, DCA measurements demonstrated that the surface of the alkyl side-chain PEUs did not undergo significant rearrangement when placed into an aqueous environment, whereas the surface of a hard segment model polymer bearing C18 sidechains (PEU-C18-HS) did. Hydrogen bonding within the PEUs was examined using FTIR and was shown to be disrupted by the addition of side-chains; an effect dependent on the density but not on the length of the side-chains. Heteropolymer blends comprised of mixtures of high side-chain density and side-chain free PEUs were compared with homopolymers having the same overall side-chain concentration as the blends. Significantly more surface enrichment of side-chains was found in the heteropolymer blends whereas hydrogen bonding nearly the same as in the homopolymers. Adsorption of native and delipidized human serum albumin (HSA) from pure solution and blood plasma; the elutabilty of adsorbed HSA; and static platelet adhesion to plasma preadsorbed surfaces, were all examined on alkyl side-chain PEUs. Several polymers with high C18 side-chain densities displayed increased

  1. [Verification of a decrease in the rigidity of the phage lambda DNA polymeric chain in low ionic strength aqueous solutions by testing the polymer-polymer interlink interactions].

    PubMed

    Arutiunian, A V; Ivanova, M A; Kurliand, D I; Kapshin, Iu S; Landa, S B; Poshekhonov, S T; Drobchenko, E A; Shevelev, I V

    2011-01-01

    Changes in the rigidity of the polymetric chain of phage lambda double-strand DNA have been studied by laser correlation spectroscopy. It was shown that, as the ionic strength increases, the effect of the screening of the hydrodynamic interaction of the links of the polymeric chain specific for polymeric coils arises in a DNA solution. It is assumed that the screening occurs when the threshold of the overlapping of DNA coils is achieved. The overlapping of coils is the result of a previously observed significant rise of DNA coil size from abnormally small DNA coils in low ionic strength buffers (about 10(-2) M Na+ or less) to maximum possible large coils in the 5SSC and 5SSC-like buffers. Further analysis of the far interlink interactions in linear lambda phage DNA coils in similar buffers at pH 7 and 4 confirms the earlier proposal about the role of H+ ions in the appearance of abnormally small DNA coils. The abnormal decrease in the DNA coil size in low ionic strength buffers is not a specific feature of lambda phage DNA only.

  2. RADIOLYSIS OF ORGANIC COMPOUNDS IN THE ADSORBED STATE

    DOEpatents

    Sutherland, J.W.; Allen, A.O.

    1961-10-01

    >A method of forming branch chained hydrocarbons by means of energetic penetrating radiation is described. A solid zeolite substrate is admixed with a cobalt ion and is irradiated with a hydrocarbon adsorbed therein. Upon irradiation with gamma rays, there is an increased yield of branched and lower molecular straight chain compounds. (AEC)

  3. Hydrothermal synthesis, crystal structure and properties of a novel chain coordination polymer constructed by tetrafunctional phosphonate anions and cobalt ions

    SciTech Connect

    Guan, Lei; Wang, Ying

    2015-08-15

    A novel cobalt phosphonate, [Co(HL)(H{sub 2}O){sub 3}]{sub n} (1) (L=N(CH{sub 2}PO{sub 3}H){sub 3}{sup 3−}) has been synthesized by hydrothermal reaction at 150 °C and structurally characterized by X-ray diffraction, infrared spectroscopy, elemental and thermogravimetric analysis. Complex 1 features a 1D chain structure with double-channel built from CoO{sub 6} octahedra bridged together by the phosphonate groups. Each cobalt ion is octahedrally coordinated by three phosphonate oxygen atoms and three water molecules. The coordinated water molecules can form the hydrogen bonds with the phosphonate oxygen atoms to link the 1D chains, building a 2D layered structure, further resulting in a 3D network. The luminescence spectrum indicates an emission maximum at 435 nm. The magnetic susceptibility curve exhibits a dominant antiferromagnetic behavior with a weakly ferromagnetic component at low temperatures. - Graphical abstract: The connectivity between cobalt ions and the ligands results in a chain structure with a 1D double-channel structure, which is constructed by A-type subrings and B-type subrings. - Highlights: • The tetrafunctional phosphonate ligand was used as the ligand. • A novel chain structure can be formed by A-type rings and B-type rings. • Two types of rings can form a 1D double-channel structure, along the c-axis.

  4. A temperature control method for shortening thermal cycling time to achieve rapid polymerase chain reaction (PCR) in a disposable polymer microfluidic device

    NASA Astrophysics Data System (ADS)

    Bu, Minqiang; Perch-Nielsen, Ivan R.; Sørensen, Karen S.; Skov, Julia; Sun, Yi; Duong Bang, Dang; Pedersen, Michael E.; Hansen, Mikkel F.; Wolff, Anders

    2013-07-01

    We present a temperature control method capable of effectively shortening the thermal cycling time of polymerase chain reaction (PCR) in a disposable polymer microfluidic device with an external heater and a temperature sensor. The method employs optimized temperature overshooting and undershooting steps to achieve a rapid ramping between the temperature steps for DNA denaturation, annealing and extension. The temperature dynamics within the microfluidic PCR chamber was characterized and the overshooting and undershooting parameters were optimized using the temperature-dependent fluorescence signal from Rhodamine B. The method was validated with the PCR amplification of mecA gene (162 bp) from methicillin-resistant Staphylococcus aureus bacterium (MRSA), where the time for 30 cycles was reduced from 50 min (without over- and undershooting) to 20 min.

  5. Regenerative adsorbent heat pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  6. Functionalization of boron diiminates with unique optical properties: multicolor tuning of crystallization-induced emission and introduction into the main chain of conjugated polymers.

    PubMed

    Yoshii, Ryousuke; Hirose, Amane; Tanaka, Kazuo; Chujo, Yoshiki

    2014-12-31

    In this article, we report the unique optical characteristics of boron diiminates in the solid states. We synthesized the boron diiminates exhibiting aggregation-induced emission (AIE). From the series of optical measurements, it was revealed that the optical properties in the solid state should be originated from the suppression of the molecular motions of the boron diiminate units. The emission colors were modulated by the substitution effects (λ(PL,crystal) = 448-602 nm, λ(PL,amorphous) = 478-645 nm). Strong phosphorescence was observed from some boron diiminates deriving from the effects of two imine groups. Notably, we found some of boron diiminates showed crystallization-induced emission (CIE) properties derived from the packing differences from crystalline to amorphous states. The 15-fold emission enhancement was observed by the crystallization (Φ(PL,crystal) = 0.59, Φ(PL,amorphous) = 0.04). Next, we conjugated boron diiminates with fluorene. The synthesized polymers showed good solubility in the common solvents, film formability, and thermal stability. In addition, because of the expansion of main-chain conjugation, the peak shifts to longer wavelength regions were observed in the absorption/emission spectra of the polymers comparing to those of the corresponding boron diiminate monomers (λ(abs) = 374-407 nm, λ(PL) = 509-628 nm). Furthermore, the absorption and the emission intensities were enhanced via the light-harvesting effect by the conjugation with fluorene. Finally, we also demonstrated the dynamic reversible alterations of the optical properties of the polymer thin films by exposing to acidic or basic vapors.

  7. Site-specific conjugation of chain-terminal chelating polymers to Fab' fragments of anti-CEA mAb: effect of linkage type and polymer size on conjugate biodistribution in nude mice bearing human colorectal carcinoma.

    PubMed

    Slinkin, M A; Curtet, C; Sai-Maurel, C; Gestin, J F; Torchilin, V P; Chatal, J F

    1992-01-01

    Polylysine-based chelating polymers were used for site-specific modification of anti-CEA mAb Fab' fragments via their SH group distal to the antigen-binding site of the antibody molecule. Conjugation was performed using chain-terminal (pyridyldithio)propionate or 4-(p-maleimidophenyl)butyrate moieties to form reducible (S-S) or stable (S-C) bonds between a polymer and Fab' molecule, respectively. One S-S conjugate (S-S9) and two different S-C conjugates (S-C3 and S-C9) were prepared using 3- and 9-kDa molecular weight polymers. No significant loss of immunoreactivity was observed in solid-phase immunoassay, 90-95% of 111In-labeled conjugates being bound to CEA-coated Sepharose beads. After labeling with 111In, the conjugates had a specific radioactivity of 90-120 microCi/micrograms. Injected in nude mice bearing LS 174T carcinoma, the conjugates produced different biodistribution patterns. S-S9 was practically unable to accumulate in tumor and produced very rapid blood clearance of radioactivity and high uptake of radioactivity in liver, spleen, and especially kidneys (225% ID/g 24 h postinjection). S-C3 and S-C9 produced practically the same blood clearances (much slower than that of S-S9) and significant tumor uptake (9-10% ID/g at 24 h). S-C3 gave significantly lower radioactivity in spleen, skin, and bones, and cleared more rapidly from liver and kidneys. Renal uptake for S-C3 and S-C9 was rather high (45% ID/g at 24 h), but much lower than for S-S9.

  8. Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization

    DOE PAGES

    Hu, Qiao -Sheng; Hong, Kunlun; Zhang, Hong -Hai

    2015-08-12

    In this study, a general strategy toward the synthesis of well-defined conjugated polymers with controlled heterobisfunctional chain ends via combination of controlled Pd(0)/t-Bu3P Suzuki cross-coupling polymerization with the post-polymerization modification of the triflate (OTf) group was disclosed.

  9. Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization

    SciTech Connect

    Hu, Qiao -Sheng; Hong, Kunlun; Zhang, Hong -Hai

    2015-08-12

    In this study, a general strategy toward the synthesis of well-defined conjugated polymers with controlled heterobisfunctional chain ends via combination of controlled Pd(0)/t-Bu3P Suzuki cross-coupling polymerization with the post-polymerization modification of the triflate (OTf) group was disclosed.

  10. Adsorbent and adsorbent bed for materials capture and separation processes

    DOEpatents

    Liu, Wei

    2011-01-25

    A method device and material for performing adsorption wherein a fluid mixture is passed through a channel in a structured adsorbent bed having a solid adsorbent comprised of adsorbent particles having a general diameter less than 100 um, loaded in a porous support matrix defining at least one straight flow channel. The adsorbent bed is configured to allow passage of a fluid through said channel and diffusion of a target material into said adsorbent under a pressure gradient driving force. The targeted molecular species in the fluid mixture diffuses across the porous support retaining layer, contacts the adsorbent, and adsorbs on the adsorbent, while the remaining species in the fluid mixture flows out of the channel.

  11. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  12. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Madathingal, Rajesh Raman

    The research investigated in this dissertation has focused on understanding the structure-property-function relationships of polymer nanocomposites. The properties of composite systems are dictated by the properties of their components, typically fillers in a polymer matrix. In nanocomposites, the polymer near an interface has significantly different properties compared with the bulk polymer, and the contribution of the adsorbed polymer to composite properties becomes increasingly important as the filler size decreases. Despite many reports of highly favorable properties, the behavior of polymer nanocomposites is not generally predictable, and thus requires a better understanding of the interfacial region. The ability to tailor the filler/matrix interaction and an understanding of the impact of the interface on macroscopic properties are keys in the design of nanocomposite properties. In this original work the surface of silica nanoparticles was tailored by: (a) Changing the number of sites for polymer attachment by varying the surface silanols and, (b) By varying the size/curvature of nanoparticles. The effect of surface tailoring on the dynamic properties after the adsorption of two model polymers, amorphous polymethyl methacrylate (PMMA) and semicrystalline polyethylene oxide (PEO) was observed. The interphase layer of polymers adsorbed to silica surfaces is affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. The non-equilibrium adsorption of PMMA onto individual colloidal Stober silica (SiO2) particles, where Rparticle (100nm) > RPMMA (˜6.5nm) was compared with the adsorption onto fumed silica, where Rparticle (7nm) ˜ RPMMA (6.5nm) < Raggregate (˜1000nm), both as a function of silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas

  13. Preparation of Main-Chain Polymers Based on Novel Monomers with D-π-A Structure for Application in Organic Second-Order Nonlinear Optical Materials with Good Long-Term Stability.

    PubMed

    Ouyang, Canbin; Liu, Jialei; Liu, Qi; Li, Yuan; Yan, Dongdong; Wang, Qiuxia; Guo, Meixia; Cao, Aocheng

    2017-03-29

    Main-chain nonlinear optical polymers based on novel chromophores with special structures presented good solubility in most of the organic solvents. Polymers PE-1 and PE-2 attained the thermal decomposition temperatures of 305 and 223 °C and glass transition temperatures of 113 and 108 °C, and exhibited only negligible decay in the SHG signal baked at 85 °C over hundreds of hours, respectively. The SHG coefficients of poled films from polymers PE-1 and PE-2 were 26.3 and 35.8 pm/V, respectively. These results indicated that this class of polymers can be used in the preparation of organic electro-optic devices.

  14. Star Polymers.

    PubMed

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  15. Transitions of tethered chain molecules under tension.

    PubMed

    Luettmer-Strathmann, Jutta; Binder, Kurt

    2014-09-21

    An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. For tethered chains in poor solvent, we observe the predicted two-phase coexistence at transitions from the globule to stretched conformations and also discover direct transitions from crystalline to stretched conformations. A phase portrait for finite chains constructed by evaluating the density of states for a broad range of solvent conditions and tensions shows how increasing tension leads to a disappearance of the globular phase. For chains in good solvents tethered to hard and attractive surfaces we find the predicted scaling with the chain length in the low-force regime and show that our results are well described by an analytical, independent-bond approximation for the bond-fluctuation model for the highest tensions. Finally, for a hard or slightly attractive surface the stretching of a tethered chain is a conformational change that does not correspond to a phase transition. However, when the surface attraction is sufficient to adsorb a chain it will undergo a desorption transition at a critical value of the applied force. Our results for force-induced desorption show the transition to be discontinuous with partially desorbed conformations in the coexistence region.

  16. Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction▿ †

    PubMed Central

    Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.

    2010-01-01

    Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact. PMID:20660682

  17. Silver coordination polymers for prevention of implant infection: thiol interaction, impact on respiratory chain enzymes, and hydroxyl radical induction.

    PubMed

    Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S; Villaruz, Amer E; Sturdevant, Daniel E; Otto, Michael; Landmann, Regine; Fromm, Katharina M

    2010-10-01

    Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact.

  18. Decades-scale degradation of commercial, side-chain, fluorotelomer-based polymers in soils and water.

    PubMed

    Washington, John W; Jenkins, Thomas M; Rankin, Keegan; Naile, Jonathan E

    2015-01-20

    Fluorotelomer-based polymers (FTPs) are the primary product of the fluorotelomer industry. Here we report on a 376-day study of the degradability of two commercial acrylate-linked FTPs in four saturated soils and in water. Using an exhaustive serial extraction, we report GC/MS and LC/MS/MS results for 50 species including fluorotelomer alcohols and acids, and perfluorocarboxylates. Modeling of seven sampling rounds, each consisting of ≥5 replicate microcosm treatments, for one commercial FTP in one soil yielded half-life estimates of 65–112 years and, when the other commercial FTP and soils were evaluated, the estimated half-lives ranged from 33 to 112 years. Experimental controls, consisting of commercial FTP in water, degraded roughly at the same rate as in soil. A follow-up experiment, with commercial FTP in pH 10 water, degraded roughly 10-fold faster than the circum-neutral control suggesting that commercial FTPs can undergo OH–-mediated hydrolysis. 8:2Fluorotelomer alcohol generated from FTP degradation in soil was more stable than without FTP present suggesting a clathrate guest–host association with the FTP. To our knowledge, these are the only degradability-test results for commercial FTPs that have been generated using exhaustive extraction procedures. They unambiguously show that commercial FTPs, the primary product of the fluorotelomer industry, are a source of fluorotelomer and perfluorinated compounds to the environment.

  19. The effect of elastomer chain flexibility on protein adsorption.

    PubMed

    Vyner, Moira C; Liu, Lina; Sheardown, Heather D; Amsden, Brian G

    2013-12-01

    Cells are known to respond differently when grown on materials of varying stiffness. However, the mechanism by which a cell senses substrate stiffness is unknown. Lower crosslink density elastomers formed from acrylated star-poly(d,l lactide-co-ϵ-caprolactone) have previously been shown to support higher smooth muscle cell proliferation in in vitro culture. This difference in growth was hypothesized to be due to differences in protein adsorption that resulted from differences in polymer chain mobility at the surface. Therefore, layer mass and viscoelastic properties were measured for HSA, IgG, fibronectin, vitronectin, and serum supplemented media adsorbed to elastomers of two crosslink densities. Significantly more fibronectin adsorbed to the lower crosslink density surface while significantly more IgG adsorbed to the higher crosslink density surface. Furthermore, differences in fibronectin and IgG layer shear moduli were observed, suggesting that there was a difference in the conformation of the adsorbed protein. ATR-FTIR analysis showed that the lower crosslink density elastomer absorbed more surface water. The increased amount of water may cause greater entropic gains upon protein adsorption to the lower crosslink density surface, which increases total protein adsorption from serum and may cause differences in protein conformation and thus cell behavior.

  20. Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

    PubMed

    Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

    2014-12-10

    In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

  1. Existence of global weak solutions to compressible isentropic finitely extensible nonlinear bead-spring chain models for dilute polymers: The two-dimensional case

    NASA Astrophysics Data System (ADS)

    Barrett, John W.; Süli, Endre

    2016-07-01

    We prove the existence of global-in-time weak solutions to a general class of models that arise from the kinetic theory of dilute solutions of nonhomogeneous polymeric liquids, where the polymer molecules are idealized as bead-spring chains with finitely extensible nonlinear elastic (FENE) type spring potentials. The class of models under consideration involves the unsteady, compressible, isentropic, isothermal Navier-Stokes system in a bounded domain Ω in Rd, d = 2, for the density ρ, the velocity u ˜ and the pressure p of the fluid, with an equation of state of the form p (ρ) =cpργ, where cp is a positive constant and γ > 1. The right-hand side of the Navier-Stokes momentum equation includes an elastic extra-stress tensor, which is the classical Kramers expression. The elastic extra-stress tensor stems from the random movement of the polymer chains and is defined through the associated probability density function that satisfies a Fokker-Planck-type parabolic equation, a crucial feature of which is the presence of a centre-of-mass diffusion term. This extends the result in our paper J.W. Barrett and E. Süli (2016) [9], which established the existence of global-in-time weak solutions to the system for d ∈ { 2 , 3 } and γ >3/2, but the elastic extra-stress tensor required there the addition of a quadratic interaction term to the classical Kramers expression to complete the compactness argument on which the proof was based. We show here that in the case of d = 2 and γ > 1 the existence of global-in-time weak solutions can be proved in the absence of the quadratic interaction term. Our results require no structural assumptions on the drag term in the Fokker-Planck equation; in particular, the drag term need not be corotational. With a nonnegative initial density ρ0 ∈L∞ (Ω) for the continuity equation; a square-integrable initial velocity datum u˜0 for the Navier-Stokes momentum equation; and a nonnegative initial probability density function ψ0

  2. Random registry shifts in quasi-one-dimensional adsorbate systems

    NASA Astrophysics Data System (ADS)

    Schäfer, J.; Erwin, S. C.; Hansmann, M.; Song, Z.; Rotenberg, E.; Kevan, S. D.; Hellberg, C. S.; Horn, K.

    2003-02-01

    The apparent contradiction of one-dimensional adsorbate chains on Si(111) having a 3×2 unit cell and yet a 3×1 diffraction pattern is resolved for the example of Ba/Si(111)-(3×2). Random registry shifts between adsorbate chains are observed in tunneling microscopy, with very short interchain correlation lengths. Fourier analysis provides a natural explanation for a pseudo-(3×1) diffraction pattern. Within density-functional theory such registry shifts can occur with essentially negligible energy cost, leading to entropy-driven, virtually perfect disorder. Substrate states of high symmetry and one-dimensional character are inferred to promote this phenomenon.

  3. Random registry shifts in quasi-one-dimensional adsorbate systems

    SciTech Connect

    Schafer, J.; Erwin, S.C.; Hansmann, M.; Song, Z.; Rotenberg, E.; Kevan, S.D.; Hellberg, C.S.; Horn, K.

    2003-02-18

    The apparent contradiction of one-dimensional adsorbate chains on Si(111) having a 3x2 unit cell and yet a 3x1 diffraction pattern is resolved for the example of Ba/Si(111)-(3x2). Random registry shifts between adsorbate chains are observed in tunneling microscopy, with very short interchain correlation lengths. Fourier analysis provides a natural explanation for a pseudo-(3x1) diffraction pattern. Within density-functional theory such registry shifts can occur with essentially negligible energy cost, leading to entropy-driven, virtually perfect disorder. Substrate states of high symmetry and one-dimensional character are inferred to promote this phenomenon.

  4. Antimocrobial Polymer

    DOEpatents

    McDonald, William F.; Huang, Zhi-Heng; Wright, Stacy C.

    2005-09-06

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

  5. Antimicrobial Polymer

    DOEpatents

    McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

    2004-09-28

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

  6. Membrane made from a multi-block polymer comprising an oxazolidone prepolymer chain extended with a compatible second prepolymer and its use in separations

    SciTech Connect

    Schucker, R.C.

    1991-08-13

    This patent describes a method for separating aromatic hydrocarbons from feed streams. It comprises mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons, the method comprising contacting the feed stream with one side of a membrane made from a multi-block polymer material comprising a first prepolymer comprising an oxazolidone made by combining (A) an epoxy with (B) a diisocyanate in an A/B or B/A mole ratio ranging from about 2.0 to 1.05, chain extended with a second, compatible prepolymer selected from the group of prepolymers consisting of an (A) diisocyanate combined with a monomer selected from (B) polyester, diamine, and dianhydride or its corresponding tetraacid or diacid-diester, in an A/B mole ratio ranging from about 2.0 to 1.05, an (A) dianhydride or its corresponding tetraacid or diacid-diester combined with a monomer selected from (B) epoxy, diisocyanate, polyester, and diamine, in an A/B mole ratio ranging from about 2.0 to 1.05, and an (A) diamine combined with a monomer selected from (B) epoxy, diisocyanate, and dianhydride or its corresponding tetraacid or diacid-diester, in an A/B mole ratio ranging from about 2.0 to 1.05, and mixtures thereof, the separation being conducted under pervaporation or perstraction conditions, whereby the aromatic hydrocarbon component of the feed stream selectively permeates through the membrane.

  7. o-, m-, and p-Pyridyl isomer effects on construction of 1D loop-and-chains: Silver(I) coordination polymers with Y-type tridentate ligands

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Gyun; Cho, Yoonjung; Lee, Haeri; Lee, Young-A.; Jung, Ok-Sang

    2016-10-01

    Self-assembly of silver(I) hexafluorophosphate with unique Y-type tridentate ligands (2,6-bis[(2-picolinoyloxy-5-methylphenyl)methyl]-p-tolylpicolinate (o-L), 2-nicotinoyloxy- (m-L), and 2-isonicotinoyloxy- (p-L)) produces single crystals consisting of 1D loop-and-chain coordination polymers of [Ag(o-L)](PF6)·Me2CO·CHCl3, [Ag(m-L)](PF6)·Me2CO, and [Ag3(p-L)2](PF6)3·2H2O·2C2H5OH·4CH2Cl2 with quite different trigonal prismatic, trigonal, and linear silver(I) coordination geometry, respectively. Coordinating ability of the three ligands for AgPF6 is in the order of p-L > o-L > m-L. The solvate molecules of [Ag(o-L)](PF6)·Me2CO·CHCl3 can be removed, and be replaced reversibly in the order of acetone ≫ chloroform ≈ dichloromethane ≫ benzene, without destruction of its skeleton.

  8. Self-assembly of silver(I) coordination polymers from aminopyrimidyl derivatives and malonate acid: From 1D chain to 2D layer

    NASA Astrophysics Data System (ADS)

    Sun, Di; Zhang, Na; Xu, Qin-Juan; Luo, Geng-Geng; Huang, Rong-Bin; Zheng, Lan-Sun

    2010-04-01

    Two new silver(I) coordination polymers (CPs) of the formula [Ag 2(dmapym) 4(mal)·H 2O] n ( 1) and [Ag 3(apym) 3(mal)NO 3] n ( 2) (dmapym = 2-amino-4,6-dimethylprimidine, apym = 2-aminopyrimidine, H 2mal = malonate) have been synthesized by reactions of AgNO 3 and 2-aminopyrimidyl ligands with malonate under the ammoniacal condition. Both complexes have been characterized by element analysis, IR and single-crystal X-ray diffraction. The monodentate dmapym and tridentate mal ligands link Ag(I) ions to give complex 1 a one-dimensional (1D) H-shaped chain structure. The complex 2 is a two-dimensional (2D) double sheet structure constructed by (4, 4) single sheet. Additionally, the hydrogen-bonding and C-H⋯π interactions also direct the self-assembly of supramolecular architectures. The photoluminescence properties of the 1 and 2 were investigated in the solid state at room temperature.

  9. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  10. Electron transporting polymers for light emitting diodes

    SciTech Connect

    Li, Xiao-Chang; Giles, M.; Holmes, A.B.

    1995-12-01

    New oxadiazole-derived side chain polymers have been prepared by radical induced polymerization of the methacrylate precursors. The synthesis and characterization of the polymers as well as their application in enhancing emission in polymer LEDs will be reported.

  11. Polymer-phyllosilicate nanocomposites and their preparation

    DOEpatents

    Chaiko, David J.

    2007-01-09

    Polymer-phyllosilicate nanocomposites that exhibit superior properties compared to the polymer alone, and methods-for producing these polymer-phyllosilicate nanocomposites, are provided. Polymeric surfactant compatabilizers are adsorbed onto the surface of hydrophilic or natural phyllosilicates to facilitate the dispersal and exfoliation of the phyllosilicate in a polymer matrix. Utilizing polymeric glycol based surfactants, polymeric dicarboxylic acids, polymeric diammonium surfactants, and polymeric diamine surfactants as compatabilizers facilitates natural phyllosilicate and hydrophilic organoclay dispersal in a polymer matrix to produce nanocomposites.

  12. Protein, cell and bacterial fouling resistance of polypeptoid-modified surfaces: effect of side-chain chemistry†

    PubMed Central

    Statz, Andrea R.; Barron, Annelise E.; Messersmith, Phillip B.

    2011-01-01

    Peptidomimetic polymers consisting of poly-N-substituted glycine oligomers (polypeptoids) conjugated to biomimetic adhesive polypeptides were investigated as antifouling surface coatings. The polymers were immobilized onto TiO2 surfaces via an anchoring peptide consisting of alternating residues of 3,4-dihydroxyphenylalanine (DOPA) and lysine. Three polypeptoid side-chain compositions were investigated for antifouling performance and stability toward enzymatic degradation. Ellipsometry and XPS analysis confirmed that purified polymers adsorbed strongly to TiO2 surfaces, and the immobilized polymers were resistant to enzymatic degradation as demonstrated by mass spectrometry. All polypeptoid-modified surfaces exhibited significant reductions in adsorption of lysozyme, fibrinogen and serum proteins, and were resistant to 3T3 fibroblast cell attachment for up to seven days. Long-term in vitro cell attachment studies conducted for six weeks revealed the importance of polypeptoid side-chain composition, with a methoxyethyl side chain providing superior long-term fouling resistance compared to hydroxyethyl and hydroxypropyl side chains. Finally, attachment of both gram-positive and gram-negative bacteria for up to four days under continuous-flow conditions was significantly reduced on the polypeptoid-modified surfaces compared to unmodified TiO2 surfaces. The results reveal the influence of polypeptoid side-chain chemistry on short-term and long-term protein, cell and bacterial fouling resistance. PMID:21472038

  13. Electronic transport in a model tetraphenylbenzidine main-chain polymer: Direct comparison of time-of-flight hole drift mobility and electrochemical determinations of hole diffusion

    NASA Astrophysics Data System (ADS)

    Abkowitz, M. A.; Facci, J. S.; Limburg, W. W.; Yanus, J. F.

    1992-09-01

    Electronic transport behavior is analyzed in a model polytetraphenylbenzidine (PTPB) hole transport polymer in which electroactive tetraphenylbenzidine sites are covalently bonded within the polymer main chain. Time-of-flight (TOF) techniques are used to measure the hole drift mobility as a function of electric field and temperature. The TOF data are parametrized using the phenomenological model originally proposed by Gill. For comparative purposes, the disorder model developed by the Marburg group is also used to analyze the data. Transport of holes in PTPB is demonstrated to occur via hopping among the TPB functional units. A pattern of convoluted field and temperature-dependent features, now known to be shared by a broad class of disordered molecular materials, is revealed by the TOF data. Thin solid film electrochemical techniques are applied in parallel with the TOF technique to independently obtain hole diffusion coefficients (Dh) in thin films of PTPB. As a unique consequence of this comparison, it is established that mobilities, computed from solid-state hole diffusion data using the Einstein relation, converge with zero-field extrapolated TOF mobilities over a wide temperature range when the extrapolation is computed from log μ vs E1/2 plots. Therefore, the functional dependence of the logarithm of the drift mobility on the square root of field, a much discussed general feature of electronic transport in disordered molecular materials, is demonstrated to persist through the critical low-field limit. At the same time it is demonstrated that the contribution of thermally driven diffusive broadening, which can now be calculated directly from the independently determined electrochemical hole diffusion coefficients, makes an insignificant contribution to the experimentally observed width of the time-of-flight transit pulse. A comparison of the PTPB data with analogous TOF data on solid solutions of TPD (the functional unit in PTPB) dispersed in polycarbonate

  14. Elution by Le Chatelier's principle for maximum recyclability of adsorbents: applied to polyacrylamidoxime adsorbents for extraction of uranium from seawater.

    PubMed

    Oyola, Yatsandra; Vukovic, Sinisa; Dai, Sheng

    2016-05-28

    Amidoxime-based polymer adsorbents have attracted interest within the last decade due to their high adsorption capacities for uranium and other rare earth metals from seawater. The ocean contains an approximated 4-5 billion tons of uranium and even though amidoxime-based adsorbents have demonstrated the highest uranium adsorption capacities to date, they are still economically impractical because of their limited recyclability. Typically, the adsorbed metals are eluted with a dilute acid solution that not only damages the amidoxime groups (metal adsorption sites), but is also not strong enough to remove the strongly bound vanadium, which decreases the adsorption capacity with each cycle. We resolved this challenge by incorporating Le Chatelier's principle to recycle adsorbents indefinitely. We used a solution with a high concentration of amidoxime-like chelating agents, such as hydroxylamine, to desorb nearly a 100% of adsorbed metals, including vanadium, without damaging the metal adsorption sites and preserving the high adsorption capacity. The method takes advantage of knowing the binding mode between the amidoxime ligand and the metal and mimics it with chelating agents that then in a Le Chatelier's manner removes metals by shifting to a new chemical equilibrium. For this reason the method is applicable to any ligand-metal adsorbent and it will make an impact on other extraction technologies.

  15. Studying Polymer Transport on Soft and Hard Surfaces

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2007-03-01

    We have employed experiments and simulations to understand the factors controlling the transport of polymers on surfaces. From an experimental viewpoint we have focused on the transport of DNA (single stranded) on lipid bilayers. We show that this behavior is slaved to the mobility of the lipids. More surprisingly, it appears that the transport of molecules adsorbed on surfaces follows the same dependence on lipid mobility as for molecules incorporated into the lipid layer. The ability to control this surface diffusion through the introduction of posts or varying the strength of adsorption (by the use of an AC field normal to the surfaces) will also be studied. Theoretically we have used molecular dynamics simulations of a polymer chain of length N dissolved in explicit solvent and adsorbed as a pancake at the solid-liquid interface to discriminate between respective influences on surface diffusion of hydrodynamics and adsorption energetics. Only for analytically-smooth surfaces do we observe a strong influence of hydrodynamics; the polymer lateral diffusion constant, D, scales as D 1/N^3/4, more weakly than for implicit solvent. For atomistic surface corrugation with uniform surface chemical makeup, D 1/N instead. This suggests that while we can understand the results for diffusion on lipid surfaces, more recent experimental observations of stronger N dependence for diffusion on hard solid surfaces originate not in hydrodynamic interactions but in spatially patchy energetic interactions.

  16. Lipid monolayers and adsorbed polyelectrolytes with different degrees of polymerization.

    PubMed

    Ortmann, Thomas; Ahrens, Heiko; Lawrenz, Frank; Gröning, Andreas; Nestler, Peter; Günther, Jens-Uwe; Helm, Christiane A

    2014-06-17

    Polystyrene sulfonate (PSS) of different molecular weight M(w) is adsorbed to oppositely charged DODAB monolayers from dilute solutions (0.01 mmol/L). PSS adsorbs flatly in a lamellar manner, as is shown by X-ray reflectivity and grazing incidence diffraction (exception: PSS with M(w) below 7 kDa adsorbs flatly disordered to the liquid expanded phase). The surface coverage and the separation of the PSS chains are independent of PSS M(w). On monolayer compression, the surface charge density increases by a factor of 2, and the separation of the PSS chains decreases by the same factor. Isotherms show that on increase of PSS M(w) the transition pressure of the LE/LC (liquid expanded/liquid condensed) phase transition decreases. When the contour length exceeds the persistence length (21 nm), the transition pressure is low and constant. For low-M(w) PSS (<7 kDa) the LE/LC transition of the lipids and the disordered/ordered transition of adsorbed PSS occur simultaneously, leading to a maximum in the contour length dependence of the transition enthalpy. These findings show that lipid monolayers at the air/water interface are a suitable mode