Bioorthogonal layer-by-layer encapsulation of pancreatic islets via hyperbranched polymers

PubMed Central

Gattás-Asfura, Kerim M.; Stabler, Cherie L.

2013-01-01

The encapsulation of viable tissues via layer-by-layer polymer assembly provides a versatile platform for cell surface engineering, with nanoscale control over capsule properties. Herein, we report the development of a hyperbranched polymer-based, ultrathin capsule architecture expressing bioorthogonal functionality and tailored physiochemical properties. Random carbodiimide-based condensation of 3,5-dicarboxyphenyl glycineamide on alginate yielded a highly branched polysaccharide with multiple, spatially restricted, and readily functionalizable terminal carboxylate moieties. Poly(ethylene glycol) (PEG) was utilized to link azido end groups to the structured alginate. Together with phosphine functionalized poly(amido amine) (PAMAM) dendrimer, nanoscale layer-by-layer coatings, covalently stabilized via Staudinger ligation, were assembled onto solid surfaces and pancreatic islets. The effects of electrostatic and/or bioorthogonal covalent interlayer interactions on the resulting coating efficiency and stability, as well as pancreatic islet viability and function, were studied. These hyperbranched polymers provide a flexible platform for the formation of covalently stabilized ultrathin coatings on viable cells and tissues. In addition, the hyperbranched nature of the polymers presents a highly functionalized surface capable of bioorthogonal conjugation of additional bioactive or labeling motifs. PMID:24063764

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

Mishchenko, L; Khan, M; Aizenberg, J

Certain natural organisms use micro-patterned surface chemistry, or ice-nucleating species, to control water condensation and ice nucleation for survival under extreme conditions. As an analogy to these biological approaches, it is shown that functionalized, hydrophilic polymers and particles deposited on the tips of superhydrophobic posts induce precise topographical control over water condensation and freezing at the micrometer scale. A bottom-up deposition process is used to take advantage of the limited contact area of a non-wetting aqueous solution on a superhydrophobic surface. Hydrophilic polymer deposition on the tips of these geometrical structures allows spatial control over the nucleation, growth, and coalescencemore » of micrometer-scale water droplets. The hydrophilic tips nucleate water droplets with extremely uniform nucleation and growth rates, uniform sizes, an increased stability against coalescence, and asymmetric droplet morphologies. Control of freezing behavior is also demonstrated via deposition of ice-nucleating AgI nanoparticles on the tips of these structures. This combination of the hydrophilic polymer and AgI particles on the tips was used to achieve templating of ice nucleation at the micrometer scale. Preliminary results indicate that control over ice crystal size, spatial symmetry, and position might be possible with this method. This type of approach can serve as a platform for systematically analyzing micrometer-scale condensation and freezing phenomena, and as a model for natural systems.« less

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

Mishchenko, Lidiya; Khan, M.; Aizenberg, Joanna

Certain natural organisms use micro-patterned surface chemistry, or ice-nucleating species, to control water condensation and ice nucleation for survival under extreme conditions. As an analogy to these biological approaches, it is shown that functionalized, hydrophilic polymers and particles deposited on the tips of superhydrophobic posts induce precise topographical control over water condensation and freezing at the micrometer scale. A bottom-up deposition process is used to take advantage of the limited contact area of a non-wetting aqueous solution on a superhydrophobic surface. Hydrophilic polymer deposition on the tips of these geometrical structures allows spatial control over the nucleation, growth, and coalescencemore » of micrometer-scale water droplets. The hydrophilic tips nucleate water droplets with extremely uniform nucleation and growth rates, uniform sizes, an increased stability against coalescence, and asymmetric droplet morphologies. Furthermore, control of freezing behavior is also demonstrated via deposition of ice-nucleating AgI nanoparticles on the tips of these structures. The combination of the hydrophilic polymer and AgI particles on the tips was used to achieve templating of ice nucleation at the micrometer scale. Preliminary results indicate that control over ice crystal size, spatial symmetry, and position might be possible with this method. This type of approach can serve as a platform for systematically analyzing micrometer-scale condensation and freezing phenomena, and as a model for natural systems.« less

Structure-to-glass transition temperature relationships in high temperature stable condensation polyimides

NASA Technical Reports Server (NTRS)

Alston, W. B.; Gratz, R. F.

1985-01-01

The presence of a hexafluoroisopropylidene (6F) connecting group in aryl dianhydrides used to prepare aromatic condensation polyimides provides high glass transition temperature (T sub g) polyimides with excellent thermo-oxidative stability. The purpose of this study was to determine if a trifluorophenyl-ethylidene (3F) connecting group would have a similar effect on the T sub g of aromatic condensation polyimides. A new dianhydride containing the 3F connecting group was synthesized. This dianhydride and an aromatic diamine also containing the 3F connecting group were used together and in various combinations with known diamines or known dianhydrides, respectively, to prepare new 3F containing condensation polyimides. Known polyimides, including some with the 6F connecting linkage, were also prepared for comparison purposes. The new 3F containing polymers and the comparison polymers were prepared by condensation polymerization via the traditional amic-acid polymerization method in N,N-dimethylacetamide solvent. The solutions were characterized by determining their inherent viscosities and then were thermally converted into polyimide films under nitrogen atmosphere at 300 to 500 C, usually 350 C. The T sub g's of the films and resin discs were then determined by thermomechanical analysis and were correlated as a function of the final processing temperatures of the films and resin discs. The results showed that similarities existed in the T sub g's depending on the nature of the connecting linkage in the monomers used to prepare the condensation polyimides.

Ultrahigh Molecular Weight Aromatic Siloxane Polymers

NASA Technical Reports Server (NTRS)

Ludwick, L. M.

1983-01-01

Silphenylene-siloxane polymers can be prepared by a condensation reaction of a diol 1,4-bis(hydroxydimethylsilyl)benzene and a silane bis(dimethylamino)dimethylsilane. Using a stepwise condensation technique, a polymer (R=CH3) with a molecular weight in excess of 1.0 x 1 million has been produced. The polymer exhibits increased thermal stability, compared to a methyl siloxane polymer without the aromatic phenyl ring in the backbone. The use of bis(dimethylamino)methylvinylsilane should allow for ready crosslinking at the vinyl sites (R=-CH=CH2) introduced into the backbone. However, under the conditions of the reaction system a high molecular weight polymer was not obtained or the polymer underwent a crosslinking process during the synthesis.

Impact of condensed tannin size as individual and mixed polymers on bovine serum albumin precipitation.

PubMed

Harbertson, James F; Kilmister, Rachel L; Kelm, Mark A; Downey, Mark O

2014-10-01

Condensed tannins composed of epicatechin from monomer to octamer were isolated from cacao (Theobroma cacao, L.) seeds and added to bovine serum albumin (BSA) individually and combined as mixtures. When added to excess BSA the amount of tannin precipitated increased with tannin size. The amount of tannin required to precipitate BSA varied among the polymers with the trimer requiring the most to precipitate BSA (1000 μg) and octamer the least (50 μg). The efficacy of condensed tannins for protein precipitation increased with increased degree of polymerisation (or size) from trimers to octamers (monomers and dimers did not precipitate BSA), while mixtures of two sizes primarily had an additive effect. This study demonstrates that astringent perception is likely to increase with increasing polymer size. Further research to expand our understanding of astringent perception and its correlation with protein precipitation would benefit from sensory analysis of condensed tannins across a range of polymer sizes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of dialyzer with immobilized glycoconjugate polymers for removal of Shiga-toxin.

PubMed

Miyagawa, Atsushi; Watanabe, Miho; Igai, Katsura; Kasuya, Maria Carmelita Z; Natori, Yasuhiro; Nishikawa, Kiyotaka; Hatanaka, Kenichi

2006-06-01

The dialyzer for Shiga-toxin elimination was developed and its performance was established. The dialyzer was prepared by immobilization of multivalent ligands. Glycoconjugate polymers having oligosaccharides and amino groups were synthesized to function as Shiga-toxin adsorbents. The amino group was utilized to immobilize the polymer inside the cellulose hollow fiber of the dialyzer. Cellulose hollow fibers packed in the dialyzer were carboxymethylated under moderate conditions. The glycoconjugate polymers were bound covalently to the hollow fibers of the dialyzer by condensation reaction between the amino group of the polymer and the carboxyl group of the cellulose hollow fiber. Shiga-toxin eliminabilities of the prepared dialyzers were evaluated at various conditions. Even at high concentration of protein such as FCS, the dialyzer showed an excellent performance for Shiga-toxin adsorption.

Taming Self-Organization Dynamics to Dramatically Control Porous Architectures.

PubMed

Daly, Ronan; Sader, John E; Boland, John J

2016-03-22

We demonstrate templating of functional materials with unexpected and intricate micro- and nanostructures by controlling the condensation, packing, and evaporation of water droplets on a polymer solution. Spontaneous evaporation of a polymer solution induces cooling of the liquid surface and water microdroplet condensation from the ambient vapor. These droplets pack together and act as a template to imprint an entangled polymer film. This breath figure (BF) phenomenon is an example of self-organization that involves the long-range ordering of droplets. Equilibrium-based analysis provides many insights into contact angles and drop stability of individual drops, but the BF phenomenon remains poorly understood thus far, preventing translation to real applications. Here we investigate the dynamics of this phenomenon to separate out the competing influences and then introduce a modulation scheme to ultimately manipulate the water vapor-liquid equilibrium independently from the solvent evaporation. This approach to BF control provides insights into the mechanism, a rationale for microstructure design, and evidence for the benefits of dynamical control of self-organization systems. We finally present dramatically different porous architectures from this approach reminiscent of microscale Petri dishes, conical flasks, and test tubes.

Controlled growth of Au nanoparticles in co-evaporated metal/polymer composite films and their optical and electrical properties

NASA Astrophysics Data System (ADS)

Takele, H.; Schürmann, U.; Greve, H.; Paretkar, D.; Zaporojtchenko, V.; Faupel, F.

2006-02-01

Nanocomposite films containing Au nanoparticles embedded in a polymer matrix were prepared by vapour phase co-deposition of Au and polymers (Teflon AF and Poly(α -methylstyrene)) in high vacuum. The microstructure of the composite materials as well as metal content strongly depend on the condensation coefficient of the Au atoms, the deposition rates of the components, the substrate temperature, and the type of polymer matrix. The condensation coefficient, which varies between 0.03 and 1, was determined from energy dispersive X-ray spectrometer (EDX) and surface profilometry. It is shown that the microstructure of nanocomposites (size, size distribution, and interparticle separation of metal clusters), which was determined by transmission electron microscopy, can be controlled by the deposition parameters and the choice of polymer matrix. The optical absorption in the visible region due to the particle plasmon resonance has a strong dependence on the metal filling factor. The correlation between the microstructure of nanocomposites and optical properties, studied using UV-Vis spectroscopy, was also established. Further more, the electrical properties of the composites were studied as a function of the metal volume fraction. It was observed that the nanocomposite films exhibit a percolation threshold at a metal volume fraction of 0.43 and 0.20 for gold nanoclusters in Teflon AF and Poly(α-methylstyrene), respectively.

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)

Low Cost Polymer heat Exchangers for Condensing Boilers

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

Butcher, Thomas; Trojanowski, Rebecca; Wei, George

2015-09-30

Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered tomore » be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.« less

An Assessment of Air Force Logistics Command’s Part Replication Program

DTIC Science & Technology

1987-09-01

ploycarabonates, ploysulfones, ployimides, and ploybenzimidazoles (Moseley, 1986:49). Thermoplastics derived from the condensation polymerization of...withstand a variety of harsh environments. Amoco’s Torlon is a ploymide-containing aromatic condensation polymer . It has such a high temperature...under conditions of both high temperature and high moisture (Moseley, 1986:51). Thermoplastics made out of polymer fibers have high strength

Directed deposition of inorganic oxide networks on patterned polymer templates

NASA Astrophysics Data System (ADS)

Ford, Thomas James Robert

Inspired by nature, we have successfully directed the deposition of inorganic oxide materials on polymer templates via a combination of top-down and bottom-up fabrication methods. We have functionally mimicked the hierarchical silica exoskeletons of diatoms, where specialized proteins chaperone the condensation of silicic acid into nanoscale silica networks confined by microscopic vesicle walls. We replaced the proteins with functionally analogous polyamines and vesicles with lithographically defined polymer templates. We grafted the polyamines either to the surface or throughout the template by changing the template chemistry and altering our grafting strategy. Exposure to an inorganic oxide precursor solution led to electrostatic aggregation at the polyamine chains, catalyzing hydrolysis and condensation to form long-range inorganic oxide nanoparticle networks. Grafted to epoxy surfaces, swelling effects and the hyperbranched brush morphology lead to the formation of nanofruit features that generated thin, conformal inorganic coatings. When the polyamines were grafted throughout hydrogel templates, we obtained composite networks that yielded faithful inorganic replicas of the original patterns. By varying the polyamine chain length and combustion parameters, we controlled the nanoparticle size, morphology, and crystalline phase. The polyamine morphology affected the resulting inorganic network in both fabrication schemes and we could control the depostion over multiple length scales. Because our methods were compatible with a variety of lithographic methods, we were able to generate inorganic replicas of 1D, 2D, and 3D polymer structures. These may be used for a wide range of applications, including sensing, catalysis, photonic, phononic, photovoltaic, and others that require well-defined inorganic structures.

Novel alkyd-type coating resins produced using cationic polymerization

DOE PAGES

Chisholm, Bret J.; Kalita, Harjyoti; Alam, Samim; ...

2015-05-06

Novel, partially bio-based poly(vinyl ether) copolymers derived from soybean oil and cyclohexyl vinyl ether (CHVE) were produced by cationic polymerization and investigated for application as alkyd-type surface coatings. Compared to conventional alkyd resins, which are produced by high temperature melt condensation polymerization, the poly(v9nyl ether)s provide several advantages. These advantages include milder, more energy efficient polymer synthesis, elimination of issues associated with gelation during polymer synthesis, production of polymers with well-defined composition and relatively narrow molecular weight distribution, and elimination of film formation and physical property issues associated with entrained monomers, dimers, trimers, etc. The results of the studied showedmore » that the thermal, mechanical, and physical properties of the coatings produced from these novel polymers varied considerably as a function of polymer composition and cure temperature. Overall, the results suggest a good potential for these novel copolymers to be used for coatings cured by autoxidation.« less

Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities

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

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.; WHEELER,DAVID R.

2000-07-14

Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety ofmore » applications such as scavenging of heavy metals.« less

Hierarchical nanoparticle assemblies formed by decorating breath figures.

PubMed

Böker, Alexander; Lin, Yao; Chiapperini, Kristen; Horowitz, Reina; Thompson, Mike; Carreon, Vincent; Xu, Ting; Abetz, Clarissa; Skaff, Habib; Dinsmore, A D; Emrick, Todd; Russell, Thomas P

2004-05-01

The combination of two self-assembly processes on different length scales leads to the formation of hierarchically structured nanoparticle arrays. Here, the formation of spherical cavities, or 'breath figures'-made by the condensation of micrometre-sized water droplets on the surface of a polymer solution-that self-assemble into a well-ordered hexagonal array, is combined with the self-assembly of CdSe nanoparticles at the polymer solution-water droplet interface. Complete evaporation of the solvent and water confines the particle assembly to an array of spherical cavities and allows for ex situ investigation. Fluorescence confocal, transmission electron and scanning electron microscope images show the preferential segregation of the CdSe nanoparticles to the polymer solution-water interface where they form a 5-7-nm-thick layer, thus functionalizing the walls of the holes. This process opens a new route to fabricating highly functionalized ordered microarrays of nanoparticles, potentially useful in sensory, separation membrane or catalytic applications.

Comparison between polymerized ionic liquids synthesized using chain-growth and step-growth mechanisms used as stationary phase in gas chromatography.

PubMed

Roeleveld, Kevin; David, Frank; Lynen, Frédéric

2016-06-17

In this study the merits of polymerized imidazolium based ionic liquid (PIL) stationary phases obtained via condensation and free radical polymerizations are compared as stationary phases in gas chromatography (GC). Poly(1-vinyl-3-butyl-imidazolium - bis(trifluoromethane)sulfonamide) (poly(ViC4Im(+) NTf2(-))) was obtained via a chain-growth mechanism while poly(propylimidazolium-NTf2) (poly(C3Im(+) NTf2(-))) was synthesized via a step-growth polymerization. The thermal stability of both polymers was assessed using thermal gravimetric analysis and compared with bleeding profiles obtained from the statically coated GC columns (30m×0.25mm×0.25μm). The performance was compared to what could be obtained on commercially available 1,5-di(2,3-dimethylimidazolium)pentane(2+) 2NTf2(-) (SLB-IL111) ionic liquid based columns. It was observed that the step-growth polymer was more thermally stable, up to 325°C, while the chain-growth polymer showed initial degradation at 250°C. Both polymers allowed reaching minimal plate heights of 0.400-0.500mm for retained solutes such as benzaldehyde, acetophenone, 1-methylnaphthalene and aniline. Assessment of the McReynolds constants illustrated that the polarity of the step-growth polymer was similar to the SLB-IL111 column, while displaying improved column stability. The PIL phases and particularly the so far little studied condensation based polymer shows particular retention and satisfactory column performance for polar moieties such as esters, amine and carbonyl functionalities. Copyright © 2016 Elsevier B.V. All rights reserved.

Review of oxidative degradations of certain heterocyclic polymers

NASA Technical Reports Server (NTRS)

Mayo, F. R.

1971-01-01

The curing and decompositions of polyphenylenes and several nitrogen-containing condensation polymers, particularly polybenzimidazoles and pyrones, are reviewed critically. It is concluded that the condensations are usually imperfect and incomplete and that in most of the published work the late stages of the condensation are complicated by the beginnings of the charring and carbonization processes. Most discussions of mechanisms in this range are highly speculative and of little value. The most promising fields for further research are at lower temperatures, where slow oxidation processes deserve study, and at higher temperatures, where it may be possible to influence carbonization processes to obtain better products.

Gravitationally Driven Wicking for Enhanced Condensation Heat Transfer.

PubMed

Preston, Daniel J; Wilke, Kyle L; Lu, Zhengmao; Cruz, Samuel S; Zhao, Yajing; Becerra, Laura L; Wang, Evelyn N

2018-04-17

Vapor condensation is routinely used as an effective means of transferring heat or separating fluids. Filmwise condensation is prevalent in typical industrial-scale systems, where the condensed fluid forms a thin liquid film due to the high surface energy associated with many industrial materials. Conversely, dropwise condensation, where the condensate forms discrete liquid droplets which grow, coalesce, and shed, results in an improvement in heat transfer performance of an order of magnitude compared to filmwise condensation. However, current state-of-the-art dropwise technology relies on functional hydrophobic coatings, for example, long chain fatty acids or polymers, which are often not robust and therefore undesirable in industrial conditions. In addition, low surface tension fluid condensates, such as hydrocarbons, pose a unique challenge because common hydrophobic condenser coatings used to shed water (with a surface tension of 73 mN/m) often do not repel fluids with lower surface tensions (<25 mN/m). We demonstrate a method to enhance condensation heat transfer using gravitationally driven flow through a porous metal wick, which takes advantage of the condensate's affinity to wet the surface and also eliminates the need for condensate-phobic coatings. The condensate-filled wick has a lower thermal resistance than the fluid film observed during filmwise condensation, resulting in an improved heat transfer coefficient of up to an order of magnitude and comparable to that observed during dropwise condensation. The improved heat transfer realized by this design presents the opportunity for significant energy savings in natural gas processing, thermal management, heating and cooling, and power generation.

Condensation polyimides

NASA Technical Reports Server (NTRS)

Hergenrother, P. M.

1989-01-01

Polyimides belong to a class of polymers known as polyheterocyclics. Unlike most other high temperature polymers, polyimides can be prepared from a variety of inexpensive monomers by several synthetic routes. The glass transition and crystalline melt temperature, thermooxidative stability, toughness, dielectric constant, coefficient of thermal expansion, chemical stability, mechanical performance, etc. of polyimides can be controlled within certain boundaries. This versatility has permitted the development of various forms of polyimides. These include adhesives, composite matrices, coatings, films, moldings, fibers, foams and membranes. Polyimides are synthesized through both condensation (step-polymerization) and addition (chain growth polymerization) routes. The precursor materials used in addition polyimides or imide oligomers are prepared by condensation method. High molecular weight polyimide made via polycondensation or step-growth polymerization is studied. The various synthetic routes to condensation polyimides, structure/property relationships of condensation polyimides and composite properties of condensation polyimides are all studied. The focus is on the synthesis and chemical structure/property relationships of polyimides with particular emphasis on materials for composite application.

Self-doped molecular composite battery electrolytes

DOEpatents

Harrup, Mason K.; Wertsching, Alan K.; Stewart, Frederick F.

2003-04-08

This invention is in solid polymer-based electrolytes for battery applications. It uses molecular composite technology, coupled with unique preparation techniques to render a self-doped, stabilized electrolyte material suitable for inclusion in both primary and secondary batteries. In particular, a salt is incorporated in a nano-composite material formed by the in situ catalyzed condensation of a ceramic precursor in the presence of a solvated polymer material, utilizing a condensation agent comprised of at least one cation amenable to SPE applications. As such, the counterion in the condensation agent used in the formation of the molecular composite is already present as the electrolyte matrix develops. This procedure effectively decouples the cation loading levels required for maximum ionic conductivity from electrolyte physical properties associated with condensation agent loading levels by utilizing the inverse relationship discovered between condensation agent loading and the time domain of the aging step.

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.

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

1998-01-01

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

1997-01-01

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

Real-time x-ray scattering study of the initial growth of organic crystals on polymer brushes

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

An, Sung Yup; Ahn, Kwangseok; Kim, Doris Yangsoo

2014-04-21

We studied the early-stage growth structures of pentacene organic crystals grown on polymer brushes using real-time x-ray scattering techniques. In situ x-ray reflectivity and atomic force microscopy analyses revealed that at temperatures close to the glass transition temperature of polymer brush, the pentacene overlayer on a polymer brush film showed incomplete condensation and 3D island structures from the first monolayer. A growth model based on these observations was used to quantitatively analyze the real-time anti-Bragg x-ray scattering intensities measured during pentacene growth to obtain the time-dependent layer coverage of the individual pentacene monolayers. The extracted total coverage confirmed significant desorptionmore » and incomplete condensation in the pentacene films deposited on the polymer brushes. These effects are ascribed to the change in the surface viscoelasticity of the polymer brushes around the glass transition temperature.« less

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, W.P. Jr.; Apen, P.G.; Mitchell, M.A.

1998-01-20

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes. 1 fig.

Large-scale assembly of colloidal particles

NASA Astrophysics Data System (ADS)

Yang, Hongta

This study reports a simple, roll-to-roll compatible coating technology for producing three-dimensional highly ordered colloidal crystal-polymer composites, colloidal crystals, and macroporous polymer membranes. A vertically beveled doctor blade is utilized to shear align silica microsphere-monomer suspensions to form large-area composites in a single step. The polymer matrix and the silica microspheres can be selectively removed to create colloidal crystals and self-standing macroporous polymer membranes. The thickness of the shear-aligned crystal is correlated with the viscosity of the colloidal suspension and the coating speed, and the correlations can be qualitatively explained by adapting the mechanisms developed for conventional doctor blade coating. Five important research topics related to the application of large-scale three-dimensional highly ordered macroporous films by doctor blade coating are covered in this study. The first topic describes the invention in large area and low cost color reflective displays. This invention is inspired by the heat pipe technology. The self-standing macroporous polymer films exhibit brilliant colors which originate from the Bragg diffractive of visible light form the three-dimensional highly ordered air cavities. The colors can be easily changed by tuning the size of the air cavities to cover the whole visible spectrum. When the air cavities are filled with a solvent which has the same refractive index as that of the polymer, the macroporous polymer films become completely transparent due to the index matching. When the solvent trapped in the cavities is evaporated by in-situ heating, the sample color changes back to brilliant color. This process is highly reversible and reproducible for thousands of cycles. The second topic reports the achievement of rapid and reversible vapor detection by using 3-D macroporous photonic crystals. Capillary condensation of a condensable vapor in the interconnected macropores leads to the increase of the effective refractive index of the diffractive medium, resulting in the red-shift of the optical stop bands. The wavelength shift is linearly proportional to the vapor partial pressure for a spectrum of vapors. Optical simulation and theoretical prediction based on Kelvin equation suggest that a liquid film is formed on the walls of the macropores during vapor condensation. The third topic describes introducing doctor blade coating fabricated large area and low cost macroporous films for thermochromic smart windows, which are useful for energy control in glazed buildings. The fabricated macroporous polymer films exhibit brilliant colors and are capable of reflecting solar radiation when in-situ heated, and become transparent as cavities are filled with a solvent which has the same refractive index as that of the polymer when cooled to building temperature. The fourth topic reports the roll-to roll fabricated excellent water-repelling and self-cleaning macroporous polymer films. The size of the voids can be easily controlled by tuning the duration of an oxygen reactive-ion etching process prior to the removal of the templating silica spheres from silica colloidal-polymer composites. After surface functionalization with fluorosilane, superhydrophobic surface with large apparent water contact angle and small sliding angle can be obtained. The self-cleaning functionality can be achieved on superhydrophobic macroporous coatings by preventing bacterial contamination is further demonstrated. The fifth topic presented is that the template macroporous polymer films with interconnected voids and uniform interconnecting nanopores can be directly used as filtration membranes to achieve size-exclusive separation of particles. The results also demonstrate that more than 85% of small sized particles are recovered after filtration. The results also demonstrate that Escherichia coli can be filtrated by the from macroporous polymer films aqueous solution.

Osmotic Challenge Drives Rapid and Reversible Chromatin Condensation in Chondrocytes

PubMed Central

Irianto, Jerome; Swift, Joe; Martins, Rui P.; McPhail, Graham D.; Knight, Martin M.; Discher, Dennis E.; Lee, David A.

2013-01-01

Changes in extracellular osmolality have been shown to alter gene expression patterns and metabolic activity of various cell types, including chondrocytes. However, mechanisms by which physiological or pathological changes in osmolality impact chondrocyte function remain unclear. Here we use quantitative image analysis, electron microscopy, and a DNase I assay to show that hyperosmotic conditions (>400 mOsm/kg) induce chromatin condensation, while hypoosmotic conditions (100 mOsm/kg) cause decondensation. Large density changes (p < 0.001) occur over a very narrow range of physiological osmolalities, which suggests that chondrocytes likely experience chromatin condensation and decondensation during a daily loading cycle. The effect of changes in osmolality on nuclear morphology (p < 0.01) and chromatin condensation (p < 0.001) also differed between chondrocytes in monolayer culture and three-dimensional agarose, suggesting a role for cell adhesion. The relationship between condensation and osmolality was accurately modeled by a polymer gel model which, along with the rapid nature of the chromatin condensation (<20 s), reveals the basic physicochemical nature of the process. Alterations in chromatin structure are expected to influence gene expression and thereby regulate chondrocyte activity in response to osmotic changes. PMID:23442954

Quantum ring-polymer contraction method: Including nuclear quantum effects at no additional computational cost in comparison to ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

John, Christopher; Spura, Thomas; Habershon, Scott; Kühne, Thomas D.

2016-04-01

We present a simple and accurate computational method which facilitates ab initio path-integral molecular dynamics simulations, where the quantum-mechanical nature of the nuclei is explicitly taken into account, at essentially no additional computational cost in comparison to the corresponding calculation using classical nuclei. The predictive power of the proposed quantum ring-polymer contraction method is demonstrated by computing various static and dynamic properties of liquid water at ambient conditions using density functional theory. This development will enable routine inclusion of nuclear quantum effects in ab initio molecular dynamics simulations of condensed-phase systems.

Photolithography of Dithiocarbamate-Anchored Monolayers and Polymers on Gold

PubMed Central

Leonov, Alexei P.; Wei, Alexander

2011-01-01

Dithiocarbamate (DTC)-anchored monolayers and polymers were investigated as positive resists for UV photolithography on planar and roughened Au surfaces. DTCs were formed in situ by the condensation of CS2 with monovalent or polyvalent amines such as linear polyethyleneimine (PEI) under mildly basic aqueous conditions, just prior to surface passivation. The robust adsorption of the polyvalent PEI-DTC to Au surfaces supported high levels of resistance to photoablation, providing opportunities to generate thin films with gradient functionality. Treatment of photopatterned substrates with alkanethiols produced binary coatings, enabling a direct visual comparison of DTC- and thiol-passivated surfaces against chemically induced corrosion using confocal microscopy. PMID:21894240

Microwave promoted simple, efficient and regioselective synthesis of trisubstituted imidazo[1,2-a]benzimidazoles on soluble support.

PubMed

Chen, Li-Hsun; Hsiao, Ya-Shan; Yellol, Gorakh S; Sun, Chung-Ming

2011-03-14

An efficient microwave-assisted and soluble polymer-supported synthesis of medicinally important imidazole-fused benzimidazoles has been developed. The protocol involves the rapid condensation of polymer-bound amino benzimidazoles with various α-bromoketones and subsequent in situ intramolecular cyclization under microwave irradiation resulting in a one pot synthesis of imidazole interlacing benzimidazole polymer conjugates. The condensed product was obtained with excellent regioselectivity. The biologically interesting imidazo[1,2-a]benzimidazoles was released from polymer support at ambient temperature. Diversity in the triheterocyclic nucleus was achieved by the different substitutions at its 2, 3, and 9 positions. The new protocol has the advantages of short reaction time, easy workup process, excellent yields, reduced environmental impact, wide substrate scope and convenient procedure.

Development of Low Energy Gap and Fully Regioregular Polythienylenevinylene Derivative

DOE PAGES

David, Tanya M. S.; Zhang, Cheng; Sun, Sam-Shajing

2014-01-01

Low energy gap and fully regioregular conjugated polymers find its wide use in solar energy conversion applications. This paper will first briefly review this type of polymers and also report synthesis and characterization of a specific example new polymer, a low energy gap, fully regioregular, terminal functionalized, and processable conjugated polymer poly-(3-dodecyloxy-2,5-thienylene vinylene) or PDDTV. The polymer exhibited an optical energy gap of 1.46 eV based on the UV-vis-NIR absorption spectrum. The electrochemically measured highest occupied molecular orbital (HOMO) level is −4.79 eV, resulting in the lowest unoccupied molecular orbital (LUMO) level of −3.33 eV based on optical energy gap. The polymer wasmore » synthesized via Horner-Emmons condensation and is fairly soluble in common organic solvents such as tetrahydrofuran and chloroform with gentle heating. DSC showed two endothermic peaks at 67°C and 227°C that can be attributed to transitions between crystalline and liquid states. The polymer is thermally stable up to about 300°C. This polymer appears very promising for cost-effective solar cell applications.« less

Polymer flammability

DOT National Transportation Integrated Search

2005-05-01

This report provides an overview of polymer flammability from a material science perspective and describes currently accepted test methods to quantify burning behavior. Simplifying assumptions about the gas and condensed phase processes of flaming co...

Combustion of a polymer (PMMA) sphere in microgravity

NASA Technical Reports Server (NTRS)

Yang, Jiann C.; Hamins, Anthony

1995-01-01

Polymer combustion is a highly complicated process where chemical reactions may occur not only in the gas phase, but also in the condensed phase as well as at the solid-gas interphase. The chemistry depends strongly on the coupling between the condensed phase and gas phase phenomena. For some polymers, additional complications arise due to the formation of char layers. For others, the behavior of the condensed phase involves swelling, bubbling, melting, sputtering, and multi-stage combustion. Some of these features bear resemblance to the phenomena observed in coal particle combustion. In addition to its relevance to spacecraft fire safety, the combustion of polymeric materials is related to many applications including solid and hybrid rocket propulsion, and of recent interest, waste incineration . The burning rate is one of the most important parameters used to characterize the combustion of polymers. It has been used to rank the polymer flammability under the same experimental conditions and to evaluate various modes of inhibiting polymer flammability. The main objective of this work is to measure the burning rates of a polymeric material in low gravity. Because of inherent logistical difficulties involved in microgravity experiments, it is impossible to examine a wide spectrum of polymeric materials. It is desirable to investigate a polymer whose combustion is less complicated, and yet will lead to a better understanding of the burning characteristics of other more complicated materials. Therefore, a typical non-charring polymer is selected for use in this experimental study. PMMA (polymethylmethacrylate) has been chosen because its thermo-physical properties are well characterized. Although the combustion of PMMA has been extensively studied in 1G experiments, only a limited amount of work has been conducted in low gravity. A spherical sample geometry is chosen in this study because it is the simplest configuration in terms of the microgravity hardware design requirements. Furthermore, a burning PMMA sphere in microgravity represents a one-dimensional flame with overall combustion characteristics expected to be analogous to the combustion of a liquid fuel droplet, a field with many well-developed theories and models. However, differences can also be expected such as the flame-front standoff ratios and the condensed phase processes occurring during combustion.

Evidence for functional heterogeneity both between and within four sources of condensed tannin

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

Asquith, T.N.

1985-01-01

Condensed tannins are polymers of flavan-3-ols that are produced by many plants in a wide variety of tissues. The ability of these compounds to actively precipitate proteins has been linked to nutritional deficiencies in many animals. Four purified tannins (quebracho, wattle, pinto bean and sorghum) were compared to chemical assays and astringency towards (/sup 14/C)-BSA. Quebracho and wattle tannins were much less astringent and had longer chain lengths that sorghum or pinto bean tannins. Quebracho tannin had a very high affinity for salivary proline-rich glycoproteins (PRPs) and pinto bean tannin alone had a measurable affinity for soybean trypsin inhibitor. Thismore » suggests that tannin/protein interactions in vivo may be very specific. Protein bound carbohydrate enhanced the binding of PRPs to tanning and conferred specificity on the interactions. Carbohydrate also increases the solubility of protein/tanning complexes, which may aid the animal in eliminating the complexes. (/sup 125/I)-labeled condensed tannin was shown to retain the ability to discriminate between high and low affinity proteins. (/sup 125/I)-labeled phenols were isolated from livers and kidneys of rats fed (/sup 125/I)-labeled tannin. The techniques described in this thesis should be widely applicable to studying in vivo functions of condensed tannins.« less

Gas-separation process

DOEpatents

Toy, Lora G.; Pinnau, Ingo; Baker, Richard W.

1994-01-01

A process for separating condensable organic components from gas streams. The process makes use of a membrane made from a polymer material that is glassy and that has an unusually high free volume within the polymer material.

Organosiloxane-grafted natural polymer coatings

DOEpatents

Sugama, Toshifumi

1998-01-01

A new family of polysaccharide graft polymers are provided as corrosion resistant coatings having antimicrobial properties which are useful on light metals such as aluminum, magnesium, zinc, steel and their alloys. Methods of making the polysaccharide graft polymers are also included. The methods of making the polysaccharide graft polymers involve reacting a polysaccharide source with an antimicrobial agent under conditions of hydrolysis-condensation.

Organosiloxane-grafted natural polymer coatings

DOEpatents

Sugama, Toshifumi

1998-12-01

A new family of polysaccharide graft polymers are provided as corrosion resistant coatings having antimicrobial properties which are useful on light metals such as aluminum, magnesium, zinc, steel and their alloys. Methods of making the polysaccharide graft polymers are also included. The methods of making the polysaccharide graft polymers involve reacting a polysaccharide source with an antimicrobial agent under conditions of hydrolysis-condensation. 17 figs.

Condensed tannins: Quinone methide intermediates in procyanidin synthesis

Treesearch

Richard W. Hemingway; L. Y. Foo

1983-01-01

Proanthocyanidins (condensed tanruns) are widely distributed in plants and are found in sufficiently high concentration in some tree barks to encourage their industrial utilization. These polymers consist of flavanoid units linked through the C-4 of the pyran ring to the C-6 or C-8 carbons of the aromatic A-ring. Recent advances in the chemistry of condensed tannins...

Polyplex formation between four-arm poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate) and plasmid DNA in gene delivery.

PubMed

He, E; Yue, C Y; Simeon, F; Zhou, L H; Too, H P; Tam, K C

2009-12-01

Amphiphilic polyelectrolytes comprising cationic and uncharged hydrophilic segments condensed negatively charged DNA to form a core-shell structure stabilized by a layer of hydrophilic corona chains. At physiological pH, four-arm star-shaped poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate) (four-arm PEO-b-PDEAEMA) block copolymer possessed positively charged amine groups that interacted with negatively charged plasmid DNA to form polymer/DNA complexes. The mechanism and physicochemical properties of the complex formation were investigated at varying molar ratio of amine groups on polymer chains and phosphate group on plasmid DNA segments (N/P ratio). The capability of the star block copolymer to condense DNA was demonstrated through gel electrophoresis and ethidium bromide exclusion assay. In the absence of salt, the hydrodynamic radius of polyplexes was about 94 nm at low polymer/DNA ratio, and it decreased to about 34 nm at large N/P ratios, forming a compact spherical structure with a weighted average molecular weight of 4.39 +/- 0.22 x 10(6) g/mol. Approximately 15 polymeric chains were required to condense a plasmid DNA. The addition of monovalent salt to the polyplexes significantly altered the size of the complexes, which would have an impact on cell transfection. Because of the electrostatic interaction induced by the diffusion of small ions, the polyplex increased in size to about 53 nm with a less compact structure. In vitro cytotoxicty of polymer and polymer/pDNA complexes were evaluated, and the polyplexes exhibited low toxicity at low N/P ratios. At N/P ratio of 4.5, the four-arm PEO-b-PDEAEMA showed the highest level of transfection in Neuro-2A cells. These observations showed that the star-shaped multi-arm polymers offers interesting properties in self-association and condensation ability for plasmid DNA and can serve as a nonviral DNA delivery system. Copyright 2008 Wiley Periodicals, Inc.

Viscoelastic cationic polymers containing the urethane linkage

NASA Technical Reports Server (NTRS)

Rembaum, A. (Inventor)

1972-01-01

A method for the synthesis and manufacturing of elastomeric compositions and articles containing quaternary nitrogen centers and condensation residues along the polymeric backbone of the centers is presented. Linear and cross-linked straight chain and block polymers having a wide damping temperature range were synthesized. Formulae for the viscoelastic cationic polymers are presented.

Increased water retention in polymer electrolyte membranes at elevated temperatures assisted by capillary condensation.

PubMed

Park, Moon Jeong; Downing, Kenneth H; Jackson, Andrew; Gomez, Enrique D; Minor, Andrew M; Cookson, David; Weber, Adam Z; Balsara, Nitash P

2007-11-01

We establish a new systematic methodology for controlling the water retention of polymer electrolyte membranes. Block copolymer membranes comprising hydrophilic phases with widths ranging from 2 to 5 nm become wetter as the temperature of the surrounding air is increased at constant relative humidity. The widths of the moist hydrophilic phases were measured by cryogenic electron microscopy experiments performed on humid membranes. Simple calculations suggest that capillary condensation is important at these length scales. The correlation between moisture content and proton conductivity of the membranes is demonstrated.

Gas-separation process

DOEpatents

Toy, L.G.; Pinnau, I.; Baker, R.W.

1994-01-25

A process is described for separating condensable organic components from gas streams. The process makes use of a membrane made from a polymer material that is glassy and that has an unusually high free volume within the polymer material. 6 figures.

Salen- Zr(IV) complex grafted into amine-tagged MIL-101(Cr) as a robust multifunctional catalyst for biodiesel production and organic transformation reactions

NASA Astrophysics Data System (ADS)

Hassan, Hassan M. A.; Betiha, Mohamed A.; Mohamed, Shaimaa K.; El-Sharkawy, E. A.; Ahmed, Emad A.

2017-08-01

The synthesis of metal-organic frameworks (MOFs), porous coordination polymers with functional groups has received immense interest due to the functional groups can offer desirable properties and allow post-synthetic modification. Herein, for the first time, Zr(IV)-Sal Schiff base complex incorporated into amino-functionalized MIL-101(Cr) framework by salicylaldehyde condensing to amino group, and coordinating Zr(IV) ion have been successfully synthesized. The worthiness of the synthesized material as a catalyst has been examined for the esterification of oleic acid (free fatty acid) with methanol producing biodiesel (methyl oleate), Knoveonagel condensation reaction of aldehydes and Friedel-Crafts acylation of anisole. Our findings demonstrated that Salen-Zr(IV) grafted to framework of NH2-MIL-101(Cr) as a solid acid catalyst exhibited distinct catalytic performance for the production of biodiesel by esterification of oleic acid with methanol, Knoveonagel condensation and Friedel-Crafts acylation. These could be attributed to high surface area which allow high distribution of Zr(IV) species lead to a sufficient contact with the reactants species. Furthermore, the catalyst showed excellent recycling efficiency due to the strong interaction between the Zr(IV) ions and chelating groups in the NH2-MIL-101(Cr)-Sal.

Linking topology of tethered polymer rings with applications to chromosome segregation and estimation of the knotting length.

PubMed

Marko, John F

2009-05-01

The Gauss linking number (Ca) of two flexible polymer rings which are tethered to one another is investigated. For ideal random walks, mean linking-squared varies with the square root of polymer length while for self-avoiding walks, linking-squared increases logarithmically with polymer length. The free-energy cost of linking of polymer rings is therefore strongly dependent on degree of self-avoidance, i.e., on intersegment excluded volume. Scaling arguments and numerical data are used to determine the free-energy cost of fixed linking number in both the fluctuation and large-Ca regimes; for ideal random walks, for |Ca|>N;{1/4} , the free energy of catenation is found to grow proportional, variant|Ca/N;{1/4}|;{4/3} . When excluded volume interactions between segments are present, the free energy rapidly approaches a linear dependence on Gauss linking (dF/dCa approximately 3.7k_{B}T) , suggestive of a novel "catenation condensation" effect. These results are used to show that condensation of long entangled polymers along their length, so as to increase excluded volume while decreasing number of statistical segments, can drive disentanglement if a mechanism is present to permit topology change. For chromosomal DNA molecules, lengthwise condensation is therefore an effective means to bias topoisomerases to eliminate catenations between replicated chromatids. The results for mean-square catenation are also used to provide a simple approximate estimate for the "knotting length," or number of segments required to have a knot along a single circular polymer, explaining why the knotting length ranges from approximately 300 for an ideal random walk to 10;{6} for a self-avoiding walk.

Effective cytoplasmic release of siRNA from liposomal carriers by controlling the electrostatic interaction of siRNA with a charge-invertible peptide, in response to cytoplasmic pH

NASA Astrophysics Data System (ADS)

Itakura, Shoko; Hama, Susumu; Matsui, Ryo; Kogure, Kentaro

2016-05-01

Condensing siRNA with cationic polymers is a major strategy used in the development of siRNA carriers that can avoid degradation by nucleases and achieve effective delivery of siRNA into the cytoplasm. However, ineffective release of siRNA from such condensed forms into the cytoplasm is a limiting step for induction of RNAi effects, and can be attributed to tight condensation of siRNA with the cationic polymers, due to potent electrostatic interactions. Here, we report that siRNA condensed with a slightly acidic pH-sensitive peptide (SAPSP), whose total charge is inverted from positive to negative in response to cytoplasmic pH, is effectively released via electrostatic repulsion of siRNA with negatively charged SAPSP at cytoplasmic pH (7.4). The condensed complex of siRNA and positively-charged SAPSP at acidic pH (siRNA/SAPSP) was found to result in almost complete release of siRNA upon charge inversion of SAPSP at pH 7.4, with the resultant negatively-charged SAPSP having no undesirable interactions with endogenous mRNA. Moreover, liposomes encapsulating siRNA/SAPSP demonstrated knockdown efficiencies comparable to those of commercially available siRNA carriers. Taken together, SAPSP may be very useful as a siRNA condenser, as it facilitates effective cytoplasmic release of siRNA, and subsequent induction of specific RNAi effects.Condensing siRNA with cationic polymers is a major strategy used in the development of siRNA carriers that can avoid degradation by nucleases and achieve effective delivery of siRNA into the cytoplasm. However, ineffective release of siRNA from such condensed forms into the cytoplasm is a limiting step for induction of RNAi effects, and can be attributed to tight condensation of siRNA with the cationic polymers, due to potent electrostatic interactions. Here, we report that siRNA condensed with a slightly acidic pH-sensitive peptide (SAPSP), whose total charge is inverted from positive to negative in response to cytoplasmic pH, is effectively released via electrostatic repulsion of siRNA with negatively charged SAPSP at cytoplasmic pH (7.4). The condensed complex of siRNA and positively-charged SAPSP at acidic pH (siRNA/SAPSP) was found to result in almost complete release of siRNA upon charge inversion of SAPSP at pH 7.4, with the resultant negatively-charged SAPSP having no undesirable interactions with endogenous mRNA. Moreover, liposomes encapsulating siRNA/SAPSP demonstrated knockdown efficiencies comparable to those of commercially available siRNA carriers. Taken together, SAPSP may be very useful as a siRNA condenser, as it facilitates effective cytoplasmic release of siRNA, and subsequent induction of specific RNAi effects. Electronic supplementary information (ESI) available: De-condensation of siRNA cores by addition of heparin; time-lapse moving image of the siRNA release. See DOI: 10.1039/c5nr08365f

Electric field-induced reversible trapping of microtubules along metallic glass microwire electrodes

NASA Astrophysics Data System (ADS)

Kim, Kyongwan; Sikora, Aurélien; Nakayama, Koji S.; Umetsu, Mitsuo; Hwang, Wonmuk; Teizer, Winfried

2015-04-01

Microtubules are among bio-polymers providing vital functions in dynamic cellular processes. Artificial organization of these bio-polymers is a requirement for transferring their native functions into device applications. Using electrophoresis, we achieve an accumulation of microtubules along a metallic glass (Pd42.5Cu30Ni7.5P20) microwire in solution. According to an estimate based on migration velocities of microtubules approaching the wire, the electrophoretic mobility of microtubules is around 10-12 m2/Vs. This value is four orders of magnitude smaller than the typical mobility reported previously. Fluorescence microscopy at the individual-microtubule level shows microtubules aligning along the wire axis during the electric field-induced migration. Casein-treated electrodes are effective to reversibly release trapped microtubules upon removal of the external field. An additional result is the condensation of secondary filamentous structures from oriented microtubules.

Synthesis of hydrogel via click chemistry for DNA electrophoresis.

PubMed

Finetti, Chiara; Sola, Laura; Elliott, Jim; Chiari, Marcella

2017-09-01

This work introduces a novel sieving gel for DNA electrophoresis using a classical click chemistry reaction, the copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC), to cross-link functional polymer chains. The efficiency of this reaction provides, under mild conditions, hydrogels with near-ideal network connectivity and improved physical properties. Hydrogel formation via click chemistry condensation of functional polymers does not involve the use of toxic monomers and UV initiation. The performance of the new hydrogel in the separation of double stranded DNA fragments was evaluated in the 2200 TapeStation system, an analytical platform, recently introduced by Agilent that combines the advantages of CE in terms of miniaturization and automation with the simplicity of use of slab gel electrophoresis. The click gel enables addition of florescent dyes prior to electrophoresis with considerable improvement of resolution and separation efficiency over conventional cross-linked polyacrylamide gels. Copyright © 2017 Elsevier B.V. All rights reserved.

Thiazolothiazole-linked porous organic polymers

DOE PAGES

Zhu, Xiang; Tian, Chengcheng; Jin, Tian; ...

2014-10-07

In this study, thiazolothiazole-linked porous organic polymers have been synthesized from a facile catalyst-free condensation reaction between aldehydes and dithiooxamide under solvothermal conditions. The resultant porous frameworks exhibit a highly selective uptake of CO 2 over N 2 under ambient conditions.

The properties of syringyl, guaiacyl and p-hydroxyphenyl artificial lignins

PubMed Central

Bland, D. E.; Logan, A. F.

1965-01-01

1. Artificial lignins have been produced on potato parenchyma. 2. The methoxyl-free lignin and 4-hydroxy-3-methoxy (guaiacyl) lignins could be estimated by the sulphuric acid method but the 4-hydroxy-3,5-dimethoxy (syringyl) lignins could not. 3. Permanganate oxidation of isolated p-coumaric lignin gave 4-hydroxybenzoic acid, 4-hydroxyisophthalic acid and small amounts of hydroxytrimesic acid and 4-hydroxyphthalic acid. Ferulic lignin gave vanillic acid and 5-carboxyvanillic acid and also small amounts of 4-hydroxybenzoic acid and dehydrodivanillic acid. The sinapic lignin gave traces of syringic acid and of 4-hydroxybenzoic acid. 4. The p-coumaric lignin is a highly condensed polymer. The ferulic lignin is partly uncondensed and partly condensed through the 5-position like gymnosperm lignin. The sinapic lignin shows no evidence of condensation and is probably an ether-linked polymer. PMID:14340102

Ferroelectric hybrid fibers to develop flexible sensors for shape sensing of smart textiles and soft condensed matter bodies

NASA Astrophysics Data System (ADS)

Sebastian, Tutu; Lusiola, Tony; Clemens, Frank

2017-04-01

Piezoelectric fibers are widely used in composites for actuator and sensor applications due to its ability to convert electrical pulses into mechanical vibrations and transform the returned mechanical vibrations back into electrical signal. They are beneficial for the fabrication of composites especially 1-3 composites, active fiber composites (unidirectional axially aligned PZT fibers sandwiched between interdigitated electrodes and embedded in a polymer matrix) etc, with potential applications in medical imaging, structural health monitoring, energy harvesting, vibration and noise control. However, due to the brittle nature of PZT fibers, maximum strain is limited to 0.2% and cannot be integrated into flexible sensor applications. In this contribution, a new approach to develop flexible ferroelectric hybrid fibers for soft body shape sensing is investigated. Piezoelectric particles incorporated in a polymer matrix and extruded as fiber, 0-3 composite in fibrous form is studied. Commercially obtained calcined PZT and calcined BaTiO3 powders were used in the unsintered form to obtain flexible soft condensed matter ferroelectric hybrid fibers. The extruded fibers were subjected to investigation for their electromechanical behavior as a function of electric field. The hybrid fibers reached 10% of the maximum polarization of their sintered counterpart.

New hyperthermal thermosetting heterocyclic polymers

NASA Technical Reports Server (NTRS)

Bilow, N.; Landis, A. L.; Miller, L. J.

1970-01-01

Polyimidazopyrrolone polymers, formed by the condensation of aromatic dianhydrides with aromatic tetraamines in various solvents, form moldings that resist degradation in air and retain great strength at 400 to 700 degrees F. The resins have good insulating properties, are easy to mold, and make good protective coatings.

Computational screening of oxetane monomers for novel hydroxy terminated polyethers.

PubMed

Sarangapani, Radhakrishnan; Ghule, Vikas D; Sikder, Arun K

2014-06-01

Energetic hydroxy terminated polyether prepolymers find paramount importance in search of energetic binders for propellant applications. In the present study, density functional theory (DFT) has been employed to screen the various novel energetic oxetane derivatives, which usually construct the backbone for these energetic polymers. Molecular structures were investigated at the B3LYP/6-31G* level, and isodesmic reactions were designed for calculating the gas phase heats of formation. The condensed phase heats of formation for designed compounds were calculated by the Politzer approach using heats of sublimation. Among the designed oxetane derivatives, T4 and T5 possess condensed phase heat of formation above 210 kJ mol(-1). The crystal packing density of the designed oxetane derivatives varied from 1.2 to 1.6 g/cm(3). The detonation velocities and pressures were evaluated using the Kamlet-Jacobs equations, utilizing the predicted densities and HOFCond. It was found that most of the designed oxetane derivatives have detonation performance comparable to the monomers of benchmark energetic polymers viz., NIMMO, AMMO, and BAMO. The strain energy (SE) for the oxetane derivatives were calculated using homodesmotic reactions, while intramolecular group interactions were predicted through the disproportionation energies. The concept of chemical hardness is used to analyze the susceptibility of designed compounds to reactivity and chemical transformations. The heats of formation, density, and predicted performance imply that the designed molecules are expected to be candidates for polymer synthesis and potential molecules for energetic binders.

Synthesis of improved moisture resistant polymers

NASA Technical Reports Server (NTRS)

Orell, M. K.

1979-01-01

The use of difluoromaleimide-capped prepolymers to provide improved moisture resistant polymers was investigated. Six different prepolymer formulations were prepared by two different methods. One method utilized the PMR approach to polyimides and the second method employed the normal condensation route to provide fully imidized prepolymers. Polymer specimens cured at 450 F exhibited adequate long-term stability in air at 400 F. Moisture absorption studies were conducted on one polymer formulation. Neat Polymer specimens exhibited weight gains of up to 2% (w/w) after exposure to 100% relative humidity at 344K (160 F) for 400 hours.

Nuclear alkylated pyridine aldehyde polymers and conductive compositions thereof

NASA Technical Reports Server (NTRS)

Rembaum, A.; Singer, S. (Inventor)

1970-01-01

A thermally stable, relatively conductive polymer was disclosed. The polymer was synthesized by condensing in the presence of catalyst a 2, 4, or 6 nuclear alklylated 2, 3, or 4 pyridine aldehyde or quaternary derivatives thereof to form a polymer. The pyridine groups were liked by olefinic groups between 2-4, 2-6, 2-3, 3-4, 3-6 or 4-6 positions. Conductive compositions were prepared by dissolving the quaternary polymer and an organic charge transfer complexing agent such as TCNQ in a mutual solvent such as methanol.

Photo-oxidation degradation mechanisms in P3HT for organic solar cells: Insights from first-principles simulations

NASA Astrophysics Data System (ADS)

Leung, Kevin; Sai, Na; Zador, Judit; Henkelman, Graeme

2014-03-01

Photo-oxidation is one of the leading chemical degradation mechanisms in polymer solar cells. In this work, using hybrid density functional theory and periodic boundary condition, we investigate reaction pathways that may lead to the sulfur oxidation in poly(3-hexylthiophene)(P3HT) as a step toward breaking the macromolecule backbone. We calculate energy barriers for reactions of P3HT backbone with oxidizing radicals suggested by infrared spectroscopy (IR) and XPS studies. Our results strongly suggest that an attack of hydroxyl radical on sulfur as proposed in the literature is unlikely to be thermodynamically favored. On the other hand, a reaction between the alkylperoxyl radical and the polymer backbone may provide low barrier reaction pathways to photo-oxidation of conjugated polymers with side chains. Our work paves way for future studies using ab-initio calculations in a condensed phase setting to model complex chemical reactions relevant to photochemical stability of novel polymers. Supported by the Energy Frontier Research Center funded by the U.S. DOE Office of Basic Energy Sciences under Award #DE-SC0001091.

New rapid-curing, stable polyimide polymers with high-temperature strength and thermal stability

NASA Technical Reports Server (NTRS)

Burns, E. A.; Jones, J. F.; Kendrick, W. R.; Lubowitz, H. R.; Thorpe, R. S.; Wilson, E. R.

1969-01-01

Additive-type polymerization reaction forms thermally stable polyimide polymers, thereby eliminating the volatile matter attendant with the condensation reaction. It is based on the utilization of reactive alicyclic rings positioned on the ends of polyimide prepolymers having relatively low molecular weights.

Coupling of wet chemistry methods and spectroscopic data for elucidating composition and structure of purified condensed tannins

USDA-ARS?s Scientific Manuscript database

Condensed tannins (CTs) consist of oligomers and polymers of flavan-3-ol subunits varying in hydroxylation patterns, cis- and trans-configuration of C-ring substituents, interflavan bond connections, mean degree of polymerization (mDP), and extent of esterification. Robust analytical methods to dete...

Dynamic wetting on a thin film of soluble polymer: effects of nonlinearities in the sorption isotherm.

PubMed

Dupas, Julien; Verneuil, Emilie; Ramaioli, Marco; Forny, Laurent; Talini, Laurence; Lequeux, Francois

2013-10-08

The wetting dynamics of a solvent on a soluble substrate interestingly results from the rates of the solvent transfers into the substrate. When a supported film of a hydrosoluble polymer with thickness e is wet by a spreading droplet of water with instantaneous velocity U, the contact angle is measured to be inversely proportionate to the product of thickness and velocity, eU, over two decades. As for many hydrosoluble polymers, the polymer we used (a polysaccharide) has a strongly nonlinear sorption isotherm φ(a(w)), where φ is the volume fraction of water in the polymer and aw is the activity of water. For the first time, this nonlinearity is accounted for in the dynamics of water uptake by the substrate. Indeed, by measuring the water content in the polymer around the droplet φ at distances as small as 5 μm, we find that the hydration profile exhibits (i) a strongly distorted shape that results directly from the nonlinearities of the sorption isotherm and (ii) a cutoff length ξ below which the water content in the substrate varies very slowly. The nonlinearities in the sorption isotherm and the hydration at small distances from the line were not accounted for by Tay et al., Soft Matter 2011, 7, 6953. Here, we develop a comprehensive description of the hydration of the substrate ahead of the contact line that encompasses the two water transfers at stake: (i) the evaporation-condensation process by which water transfers into the substrate through the atmosphere by the condensation of the vapor phase, which is fed by the evaporation from the droplet itself, and (ii) the diffusion of liquid water along the polymer film. We find that the eU rescaling of the contact angle arises from the evaporation-condensation process at small distances. We demonstrate why it is not modified by the second process.

Wettability, water sorption and water solubility of seven silicone elastomers used for maxillofacial prostheses.

PubMed

Hulterström, Anna Karin; Berglund, Anders; Ruyter, I Eystein

2008-01-01

The wettability, water sorption and solubility of silicone elastomers used for maxillofacial prostheses were studied. The hypothesis was, that a material that has absorbed water would show an increase in the wettability and thus also the surface free energy of the material. Seven silicone elastomers, both addition- and condensation type polymers, were included. Five specimens of each material were subjected to treatment according to ISO standards 1567:1999 and 10477: 2004 for water sorption and solubility. The volumes of the specimens were measured according to Archimedes principle. The contact angle was measured with a contact angle goniometer at various stages of the sorption/solubility test. Wettability changed over the test period, but not according to theory. The addition type silicones showed little or no sorption and solubility, but two of the condensation type polymers tested had a significant sorption and solubility. This study showed that condensation type polymers may show too large volumetric changes when exposed to fluids, and therefore should no longer be used in prosthetic devices. The results of this study also suggests that it might be of interest to test sorption and solubility of materials that are to be implanted, since most of the materials had some solubility.

Degradation of trans-polyisoprene after root filling with thermoplasticized techniques.

PubMed

Maniglia-Ferreira, C; Bönecker, G; Silva, J B A; de Paula, R C M; Feitosa, J P A; Souza-Filho, F J

2008-04-01

To evaluate ex vivo degradation of gutta-percha following six thermoplastic obturation techniques. Ninety human-extracted mandibular premolars were selected and divided randomly into nine groups for filling. Group 1: thermomechanical compaction for 3 s with Konne gutta-percha points (Konne Ind. e Com. de Mat. Odontol., Belo Horizonte, MG, Brazil); Group 2: thermomechanical compaction for 3 s with Dentsply TP gutta-percha points (Dentsply Indústria e Comércio Ltda, Petrópolis, R.J. Brazil); Group 3: thermomechanical compaction for 10 s with Konne; Group 4: thermomechanical compaction for 10 s with Dentsply TP; Group 5: warm vertical condensation using System B (EIE/Analytic, Richmond, WA, USA) with Konne; Group 6: warm vertical condensation using System B with Dentsply TP; Group 7: vertical condensation with Konne; Group 8: vertical condensation with Dentsply TP; Group 9: Microseal cone (Analytic Endodontics, Glendora, CA, USA). A further four groups were assessed without using teeth, Group 10: Microseal microflow (Analytic Endodontics); Group 11: Obtura (Obtura Corporation, Penton, MO, USA); Group 12: Obtura flow (Obtura Corporation); Group 13: Thermafil (Dentsply Maillefer, Tulsa, OK, USA). The filling material was removed from the root canal and trans-1,4-polyisoprene isolated by solubilization of the root filling remnants in chloroform followed by filtration and centrifugation. By gel permeation chromatography and infrared spectroscopy, the occurrence and degree of degradation were assessed. The results were analysed statistically using the Kruskal-Wallis test. With differential scanning calorimetry, the thermal behaviour of the gutta-percha was determined. A significant decrease in polymer molar mass and the production of carboxyl and hydroxyl groups in the polymer were observed with thermomechanical compaction used for 10 s and vertical condensation filling techniques (P = 0.0001 and P = 0.0005, respectively). Other techniques caused no polymer degradation. Polyisoprene degrades with high temperature. Thermomechanical compaction for 10 s and vertical condensation were associated with the greatest degradative process.

Polymer blend lithography: A versatile method to fabricate nanopatterned self-assembled monolayers.

PubMed

Huang, Cheng; Moosmann, Markus; Jin, Jiehong; Heiler, Tobias; Walheim, Stefan; Schimmel, Thomas

2012-01-01

A rapid and cost-effective lithographic method, polymer blend lithography (PBL), is reported to produce patterned self-assembled monolayers (SAM) on solid substrates featuring two or three different chemical functionalities. For the pattern generation we use the phase separation of two immiscible polymers in a blend solution during a spin-coating process. By controlling the spin-coating parameters and conditions, including the ambient atmosphere (humidity), the molar mass of the polystyrene (PS) and poly(methyl methacrylate) (PMMA), and the mass ratio between the two polymers in the blend solution, the formation of a purely lateral morphology (PS islands standing on the substrate while isolated in the PMMA matrix) can be reproducibly induced. Either of the formed phases (PS or PMMA) can be selectively dissolved afterwards, and the remaining phase can be used as a lift-off mask for the formation of a nanopatterned functional silane monolayer. This "monolayer copy" of the polymer phase morphology has a topographic contrast of about 1.3 nm. A demonstration of tuning of the PS island diameter is given by changing the molar mass of PS. Moreover, polymer blend lithography can provide the possibility of fabricating a surface with three different chemical components: This is demonstrated by inducing breath figures (evaporated condensed entity) at higher humidity during the spin-coating process. Here we demonstrate the formation of a lateral pattern consisting of regions covered with 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) and (3-aminopropyl)triethoxysilane (APTES), and at the same time featuring regions of bare SiO(x). The patterning process could be applied even on meter-sized substrates with various functional SAM molecules, making this process suitable for the rapid preparation of quasi two-dimensional nanopatterned functional substrates, e.g., for the template-controlled growth of ZnO nanostructures [1].

Applications of positron annihilation spectroscopy in materials research

NASA Technical Reports Server (NTRS)

Singh, Jag J.

1988-01-01

Positron Annihilation Spectroscopy (PAS) has emerged as a powerful technique for research in condensed matter. It has been used extensively in the study of metals, ionic crystals, glasses and polymers. The present review concentrates on applications of positron lifetime measurements for elucidation of the physicochemical structure of polymers.

Experimental study of the effect of electromagnetic microwave radiation on parts made of high-energy polymer materials

NASA Astrophysics Data System (ADS)

Khimenko, L. L.; Rybakov, A. P.; Rybakov, N. A.; Kozlov, A. N.

2014-07-01

Results of experimental measurements of Young's modulus, burning rate, and specific heat of condensed high-energy polymer compositions (solid propellants) subjected to microwave radiation are reported. Experimental equipment and arrangement of experiments are described; the results obtained are analyzed.

International Symposium on Polymer Electrolytes (1st)

DTIC Science & Technology

1987-06-01

second order transitions, and chemical stability, e.g. dehydration or chemical decomposition . This is a powerful technique which can be used...References (M.Watanabe et. al) 1) Polym.J., 15, 65, 175 (1983). 2) Polym.J., 16, 711 (1984); 17, 549 (1985). 3) Macromolecules, 18, 1945 (1985). 4) Nippon...material is an organically modified silicate which gives, alter hydrolysis and condensation, an organic-inorganic glass. The silica network gives good

Development of a Targeted anti-HER2 scFv Chimeric Peptide for Gene Delivery into HER2-Positive Breast Cancer Cells.

PubMed

Cheraghi, Roya; Nazari, Mahboobeh; Alipour, Mohsen; Majidi, Asia; Hosseinkhani, Saman

2016-12-30

Chimeric polymers are known as suitable carriers for gene delivery. Certain properties are critical for a polymer to be used as a gene delivery vector. A new polymer was designed for the targeted delivery of genes into breast cancer cell lines, based on MPG peptide. It is composed of different functional domains, including HIV gp41, nuclear localization sequence of SV40 T-antigen, two C-terminus repeats of histone H1, and the scFv of anti-HER2 antibody. The results demonstrated that the vector can effectively condense plasmid DNA into nanoparticles with an average size of 250nm. Moreover, fusion of the scFv portion to the carrier brought about the specific recognition of HER2. Overall, the transfection efficiency of the vector demonstrated that it could deliver the desired gene into BT-474 HER2-positive breast cancer cells. Copyright © 2016 Elsevier B.V. All rights reserved.

[Characteristics of cationic polymers PEI-CyD, PEI-PHPA, PEE-PHPA and PEI25kD in vitro and in vivo].

PubMed

Yao, Qi; Jin, Xue; Hu, Tian-nan; Wang, Qi-wen; Wang, Xun-shi; Hu, Qi-da; Xu, Sang; Zhou, Jun; Tang, Gu-ping

2012-11-01

To study the characteristics of cationic polymers polyethylenimine-β-cyclodextrin (PEI-CyD), polyethylenimine-poly-(3-hydroxypropyl)-aspartamide (PEI-PHPA), N,N-Dimethyldipropylenetriamine-Bis(3-aminopropyl)amine-aspartamide (PEE-PHPA) in vitro and in vivo. PEI-PHPA, PEI-CyD and PEE-PHPA were synthesized and the chemistry structure of PEI-PHPA, PEI-CyD and PEE-PHPA was confirmed by (1)H-NMR. The particle size and zeta potential of these polymers were measured, and capacity of plasmid DNA condensation was tested. The inhibition of COS-7, A549, HEK293 and C6 cells was measured by MTT assay. The transfection efficiency was determined in HEK293 cell lines. The toxicity, tissue distribution and transfection efficiency of cationic polymers were tested in vivo. When the N/P of polymers/DNA at 30, the particle sizes were close 250 nm and the zeta-potential were near 35 mv. They were able to condense DNA at N/P ratio < 5. The MTT assay showed that the IC(50) of PEE-PHPA was 21.5, 20.2, 7.30 and 37.1 μg/ml, and that of PEI25kD was 15.8, 18.3, 11.4 and 36.7 μg/ml in C6, COS-7, A549 and HEK293cell lines, respectively. The cell viability of PEI-CyD and PEI-PHPA in above cell lines was over 60%. They had high transfection efficiency in HEK293 cell lines. The LD(50) of PEI25Kd, PEI-CyD, PEI-PHPA and PEE-PHPA in vivo was 19.50, 100.4, 521.2 and 630.0, respectively by intraperitoneal (ip) injection. The contractions of these polymers were higher in kidney than in other organs and tissues.PEE-PHPA had slight effect on kidney and liver function. PEE and PEI25kD have higher transfection efficiency and higher toxicity; while PC and PHPA-PEI have lower toxicity and higher transfection efficiency to be used as non-viral gene vector.

Biocatalytic Synthesis of Epoxy Resins from Fatty Acids as a Versatile Route for the Formation of Polymer Thermosets with Tunable Properties.

PubMed

Torron, Susana; Semlitsch, Stefan; Martinelle, Mats; Johansson, Mats

2016-12-12

The work herein presented describes the synthesis and polymerization of series of bio-based epoxy resins prepared through lipase catalyzed transesterification. The epoxy-functional polyester resins with various architectures (linear, tri-branched, and tetra-branched) were synthesized through condensation of fatty acids derived from epoxidized soybean oil and linseed oil with three different hydroxyl cores under bulk conditions. The selectivity of the lipases toward esterification/transesterification reactions allowed the formation of macromers with up to 12 epoxides in the backbone. The high degree of functionality of the resins resulted in polymer thermosets with T g values ranging from -25 to over 100 °C prepared through cationic polymerization. The determining parameters of the synthesis and the mechanism for the formation of the species were determined through kinetic studies by 1 H NMR, SEC, and molecular modeling studies. The correlation between macromer structure and thermoset properties was studied through real-time FTIR measurements, DSC, and DMA.

A comparison of plasmid DNA delivery efficiency and cytotoxicity of two cationic diblock polyoxazoline copolymers

NASA Astrophysics Data System (ADS)

Lehner, Roman; Liu, Kegang; Wang, Xueya; Wolf, Marc; Hunziker, Patrick

2017-04-01

Cationic polymers as non-viral gene delivery carriers are widely used because of their strong condensing properties and long-term safety, but acute cytotoxicity is a persistent challenge. In this study, two types of polyplexes were prepared by co-formulating plasmid DNA and two cationic diblock copolymers PABOXA5-b-PMOXA33-PA (primary amine) and PABOXA5-b-PMOXA33-TA (tertiary amine) to check their transfection efficacies in HeLa cells and HEK293T cells, respectively. The plasmid DNA/PABOXA5-b-PMOXA33-PA polyplex showed higher transfection efficacy compared to the plasmid DNA/PABOXA5-b-PMOXA33-TA polyplex under an N/P ratio of 40. Both polymers exhibited low toxicity, attributed to the shielding effect of a hydrophilic, noncharged block. Mechanistic insight into differential transfection efficiencies of the polymers were gained by visualization and comparison of the condensates via transmission electron and atomic force microscopy. The results provide information suited for further structure optimization of polymers that are aimed for targeted gene delivery.

Physics through the 1990s: Condensed-matter physics

NASA Technical Reports Server (NTRS)

1986-01-01

The volume presents the current status of condensed-matter physics from developments since the 1970s to opportunities in the 1990s. Topics include electronic structure, vibrational properties, critical phenomena and phase transitions, magnetism, semiconductors, defects and diffusion, surfaces and interfaces, low-temperature physics, liquid-state physics, polymers, nonlinear dynamics, instabilities, and chaos. Appendices cover the connections between condensed-matter physics and applications of national interest, new experimental techniques and materials, laser spectroscopy, and national facilities for condensed-matter physics research. The needs of the research community regarding support for individual researchers and for national facilities are presented, as are recommendations for improved government-academic-industrial relations.

Method for making block siloxane copolymers

DOEpatents

Butler, N.L.; Jessop, E.S.; Kolb, J.R.

1981-02-25

A method for synthesizing block polysiloxane copolymers is disclosed. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

Method for making block siloxane copolymers

DOEpatents

Butler, Nora; Jessop, Edward S.; Kolb, John R.

1982-01-01

A method for synthesizing block polysiloxane copolymers. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

Endurance and Heat-Transfer Performance of Polymer Coatings for the Promotion of Dropwise Condensation of Steam.

DTIC Science & Technology

1984-12-01

34Relation of Egailibrium Contact Angle to Liquid and Solid Constitution," Advances in Chemislrj Series, v.43, 1964. 10. Hannemann R.J._, and Mikic B.B... Hannemann , R.J. "Condensing Surface Thickness Effects in Dropwise Conhensation" I . eat Mass Transfer, v.21, 1o.1, January, 1976. 15. Naas P. Straub

Scaling of Linking and Writhing Numbers for Spherically Confined and Topologically Equilibrated Flexible Polymers

PubMed Central

Marko, John F.

2011-01-01

Scaling laws for Gauss linking number Ca and writhing number Wr for spherically confined flexible polymers with thermally fluctuating topology are analyzed. For ideal (phantom) polymers each of N segments of length unity confined to a spherical pore of radius R there are two scaling regimes: for sufficiently weak confinement (R ⪢ N1/3) each chain has |Wr| ≈ N1/2, and each pair of chains has average |Ca| ≈ N/R3/2; alternately for sufficiently tight confinement (N1/3 ⪢ R), |Wr| ≈ |CA| ≈ N/R3/2. Adding segment-segment avoidance modifies this result: for n chains with excluded volume interactions |Ca| ≈ (N/n)1/2f(ϕ) where f is a scaling function that depends approximately linearly on the segment concentration ϕ = nN/R3. Scaling results for writhe are used to estimate the maximum writhe of a polymer; this is demonstrated to be realizable through a writhing instability that occurs for a polymer which is able to change knotting topology and which is subject to an applied torque. Finally, scaling results for linking are used to estimate bounds on the entanglement complexity of long chromosomal DNA molecules inside cells, and to show how “lengthwise” chromosome condensation can suppress DNA entanglement. PMID:21686050

Thermally resistant polymers for fuel tank sealants

NASA Technical Reports Server (NTRS)

Webster, J. A.

1973-01-01

Imide-linked perfluoroalkylene ether polymers, that were developed for the high temperature fuel tank sealant application, are discussed. Modifications of polymer structure and properties were realized through use of a new aromatic dianhydride intermediate containing an ether-linked perfluoroalkylene segment. Tests of thermal, oxidative and hydrolytic stability, fuel resistance, and adhesion are discussed along with tensile strength and elongation results. Efforts to effect a low temperature condensation of amic acid prepolymer to form imide links inside are described.

Ion-Conducting Organic/Inorganic Polymers

NASA Technical Reports Server (NTRS)

Kinder, James D.; Meador, Mary Ann B.

2007-01-01

Ion-conducting polymers that are hybrids of organic and inorganic moieties and that are suitable for forming into solid-electrolyte membranes have been invented in an effort to improve upon the polymeric materials that have been used previously for such membranes. Examples of the prior materials include perfluorosulfonic acid-based formulations, polybenzimidazoles, sulfonated polyetherketone, sulfonated naphthalenic polyimides, and polyethylene oxide (PEO)-based formulations. Relative to the prior materials, the polymers of the present invention offer greater dimensional stability, greater ease of formation into mechanically resilient films, and acceptably high ionic conductivities over wider temperature ranges. Devices in which films made of these ion-conducting organic/inorganic polymers could be used include fuel cells, lithium batteries, chemical sensors, electrochemical capacitors, electrochromic windows and display devices, and analog memory devices. The synthesis of a polymer of this type (see Figure 1) starts with a reaction between an epoxide-functionalized alkoxysilane and a diamine. The product of this reaction is polymerized by hydrolysis and condensation of the alkoxysilane group, producing a molecular network that contains both organic and inorganic (silica) links. The silica in the network contributes to the ionic conductivity and to the desired thermal and mechanical properties. Examples of other diamines that have been used in the reaction sequence of Figure 1 are shown in Figure 2. One can use any of these diamines or any combination of them in proportions chosen to impart desired properties to the finished product. Alternatively or in addition, one could similarly vary the functionality of the alkoxysilane to obtain desired properties. The variety of available alkoxysilanes and diamines thus affords flexibility to optimize the organic/inorganic polymer for a given application.

Environmental Degradation of Fiber-Reinforced Polymer Fasteners in Wood

Treesearch

Samuel L. Zelinka; Douglas R. Rammer

2013-01-01

This paper examines the durability of fiber-reinforced polymer (FRP) nails in treated wood. The FRP nails were exposed to four conditions: (1) accelerated weathering, consisting of exposure to ultraviolet light and condensation; (2) 100% relative humidity (RH); (3) being driven into untreated wood and exposed to 100% RH; and (4) being driven into wood treated with...

Molecular weight profiles of proanthocyanidin polymers

Treesearch

Vincent M. Williams; Lawrence J. Porter; Richard W. Hemingway

1983-01-01

The MW profiles of proanthocyanidin polymers (condensed tannins) from 32 samples representing a wide range of plant tissues of many different species have been obtained by gel permeation chromatography of the peracetate derivatives. The tannins vary widely in MW, with M values for the peracetates in the range 1600-5500. The MW profiles vary greatly from those with...

Hybrid particle-continuum simulations coupling Brownian dynamics and local dynamic density functional theory.

PubMed

Qi, Shuanhu; Schmid, Friederike

2017-11-08

We present a multiscale hybrid particle-field scheme for the simulation of relaxation and diffusion behavior of soft condensed matter systems. It combines particle-based Brownian dynamics and field-based local dynamics in an adaptive sense such that particles can switch their level of resolution on the fly. The switching of resolution is controlled by a tuning function which can be chosen at will according to the geometry of the system. As an application, the hybrid scheme is used to study the kinetics of interfacial broadening of a polymer blend, and is validated by comparing the results to the predictions from pure Brownian dynamics and pure local dynamics calculations.

Functional Stability of a Mixed Microbial Consortium Producing PHA From Waste Carbon Sources

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

David N. Thompson; Erik R. Coats; William A. Smith

2006-04-01

Polyhydroxyalkanoates (PHAs) represent an environmentally-effective alternative to synthetic thermoplastics; however, current production practices are not sustainable. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing real wastewaters and mixed microbial consortia from municipal activated sludge as inoculum. Polymer production reached 85%, 53%, and 10% of the cell dry weight from methanol-enriched pulp-and-paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. Employing denaturing gradient gel electrophoresis of 16S-rDNA from PCR-amplified DNA extracts, distinctly different communities were observed between and within wastewaters following enrichment. Most importantly, functional stability was maintained despite differing and contrasting microbial populations.

Functional Stability of a Mixed Microbial Consortium Producing PHA From Waste Carbon Sources

NASA Astrophysics Data System (ADS)

Coats, Erik R.; Loge, Frank J.; Smith, William A.; Thompson, David N.; Wolcott, Michael P.

Polyhydroxyalkanoates (PHAs) represent an environmentally effective alternative to synthetic thermoplastics; however, current production practices are not sustainable. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing real wastewaters and mixed microbial consortia from municipal activated sludge as inoculum. Polymer production reached 85, 53, and 10% of the cell dry weight from methanol-enriched pulp and paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. Using denaturing gradient gel electrophoresis of 16S-rDNA from polymerase chain reaction-amplified DNA extracts, distinctly different communities were observed between and within wastewaters following enrichment. Most importantly, functional stability was maintained despite differing and contrasting microbial populations.

MALDI-TOF MS analysis of condensed tannins with potent antioxidant activity from the leaf, stem bark and root bark of Acacia confusa.

PubMed

Wei, Shu-Dong; Zhou, Hai-Chao; Lin, Yi-Ming; Liao, Meng-Meng; Chai, Wei-Ming

2010-06-15

The structures of the condensed tannins from leaf, stem bark and root bark of Acacia confusa were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, and their antioxidant activities were measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing/antioxidant power (FRAP) assays. The results showed that the condensed tannins from stem bark and root bark include propelargonidin and procyanidin, and the leaf condensed tannins include propelargonidin, procyanidin and prodelphinidin, all with the procyanidin dominating. The condensed tannins had different polymer chain lengths, varying from trimers to undecamers for leaf and root bark and to dodecamers for stem bark. The condensed tannins extracted from the leaf, stem bark and root bark all showed a very good DPPH radical scavenging activity and ferric reducing power.

Developing Novel Fluorescent Materials with Near Infrared Emission by Using m-Phenylene

NASA Technical Reports Server (NTRS)

Pang, Yi; Liao, Ling; Meador, Michael A.

2003-01-01

Our research focuses on development of novel p-conjugated polymers with desired emission. In the current study, the structure of a highly green-emitting poly[(m-phenylenevinylene)- alt-( p-phenylenevinylene)] has been modified by increasing the content of p-phenylene to achieve red- and infrared-emission. The polymer is synthesized via Wittig-Horner condensation, which is known to lead to trans-olefin linkage. The polymer is soluble in common organic solvents such as toluene, chloroform and THF. The spectroscopic properties of the polymer in both solution and film states will be discussed in comparison with its model compound.

Variability in Lignin Composition and Structure in Cell Walls of Different Parts of Macaúba (Acrocomia aculeata) Palm Fruit.

PubMed

Rencoret, Jorge; Kim, Hoon; Evaristo, Anderson B; Gutiérrez, Ana; Ralph, John; Del Río, José C

2018-01-10

The lignins from different anatomical parts of macaúba (Acrocomia aculeata) palm fruit, namely stalks, epicarp, and endocarp, were studied. The lignin from stalks was enriched in S-lignin units (S/G 1.2) and β-ether linkages (84% of the total) and was partially acylated at the γ-OH of the lignin side-chains (26% lignin acylation), predominantly with p-hydroxybenzoates and acetates. The epicarp lignin was highly enriched in G-lignin units (S/G 0.2) and consequently depleted in β-ethers (65%) and enriched in condensed structures such as phenylcoumarans (24%) and dibenzodioxocins (3%). The endocarp lignin was strikingly different from the rest and presented large amounts of piceatannol units incorporated into the polymer. This resulted in a lignin polymer depleted in β-ethers but enriched in condensed structures and linked piceatannol moieties. The incorporation of piceatannol into the lignin polymer seems to have a role in seed protection.

An ecotoxicological study on tin- and bismuth-catalysed PDMS based coatings containing a surface-active polymer.

PubMed

Pretti, Carlo; Oliva, Matteo; Mennillo, Elvira; Barbaglia, Martina; Funel, Marco; Reddy Yasani, Bhaskar; Martinelli, Elisa; Galli, Giancarlo

2013-12-01

Novel films were prepared by condensation curing reaction of a poly(dimethyl siloxane) (PDMS) matrix with bismuth neodecanoate and dibutyltin diacetate catalysts. An ecotoxicological study was performed on the leachates of the coatings using the bacterium Vibrio fischeri, the unicellular alga Dunaliella tertiolecta, the crustacean Artemia salina and the fish Sparus aurata (larvae) as testing organisms. A copper-based self-polishing commercial paint was also tested as reference. The results showed that the tin-catalysed coatings and the copper paint were highly toxic against at least two of the four test organisms, whereas bismuth-catalysed coatings did not show any toxic effect. Moreover, the same biological assessment was also carried out on PDMS coatings containing a surface-active fluorinated polymer. The toxicity of the entire polymeric system resulted only from the tin catalyst used for the condensation curing reaction, as the bismuth catalysed coatings incorporating the surface-active polymer remained atoxic toward all the tested organisms. © 2013 Elsevier Inc. All rights reserved.

Effect of tetraethoxysilane coating on the improvement of plasma treated polypropylene adhesion

NASA Astrophysics Data System (ADS)

Pantoja, M.; Encinas, N.; Abenojar, J.; Martínez, M. A.

2013-09-01

Polypropylene is one of the most used polymers due to its lightweight and recyclability properties, among others. However, its poor characteristics regarding surface energy and lack of polar functional groups have to be overcome to perform adhesion processes. The main objective of this work is to improve the adhesion behavior of polypropylene by combining atmospheric pressure plasma surface activation and silane adhesion promoter. Tetraethoxysilane hydrolysis and condensation are followed through infrared spectroscopy by attenuated total reflectance in order to set the coating conditions. Contact angle measurements and surface energy calculations as well as infrared and X-ray photoelectron spectroscopy are used to evaluate polymer chemical modifications. Morphological changes are studied through scanning electron and atomic force microscopy. Results show the ability of plasma treatment to create active oxydised functional groups on the polypropylene surface. These groups lead to a proper wetting of the polymer by the silane. Shear strength of single-lap bonding of polypropylene with a polyurethane adhesive suffers a significant improvement when the silane coating is applied on previously plasma activated samples. It has been also demonstrated that the silane curing conditions play a decisive role on the adhesion response. Finally, the stability of the silane solution is tested up to 30 days, yielding diminished but still acceptable adhesion strength values.

Preparation and characterization of conjugated polymers made by postpolymerization reactions of alternating polyketones.

PubMed

Cheng, Chen; Guironnet, Damien; Barborak, James; Brookhart, Maurice

2011-06-29

Conjugated polymers possessing a poly(2,5-dimethylene-2,5-dihydrofuran) backbone were prepared through postpolymerization reaction of styrenic polyketones with bromine in one-pot reactions. The modification is proposed to proceed via condensation of two repeating units to form a fully characterized polymer with a poly(2,5-dimethylenetetrahydrofuran) backbone. Subsequent bromination and elimination of HBr yield a polymer with a fully conjugated carbon backbone. The new conjugated polymers were characterized by NMR, IR, and UV-vis spectroscopies and by CV. These polymers have strong absorption in the visible region, with the absorption peaks shifted to the NIR region upon doping with acids. The ease of the synthesis of the starting polyketone and of the modifications allows large-scale preparation of those conjugated polymers.

Functional polycarbonates and their self-assemblies as promising non-viral vectors.

PubMed

Seow, Wei Yang; Yang, Yi Yan

2009-10-01

Polycarbonates are promising biomaterials due to their biocompatibility, degradability and low toxicity. In this study, a series of COOH-functionalized polycarbonates was synthesized via an organocatalytic ring opening polymerization pathway under mild conditions. The polymers displayed a range of molecular weights (M(w): 3.1, 5.5 and 9.7 kDa) and were very narrowly distributed (polydispersity index: 1.07, 1.07 and 1.15 respectively). Aliphatic amines with different chain lengths (triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine) were then conjugated onto the polycarbonate backbone using DIC/NHS chemistry. These amine-functionalized polycarbonates could form nanoparticles upon simple dissolution in water and had CMC values ranging from 22 to 45 mg/L. It was found that a longer amine chain resulted in greater buffering capacity, more positive zeta potential and smaller hydrodynamic size of the polymeric nanoparticles. Results from gel retardation assays indicated that the polymers were able to condense DNA. In-vitro studies further demonstrated that selected amine-functionalized polycarbonates could mediate efficient luciferase expression in HEK293, HepG2 and 4T1 cell lines at levels that were comparable, or even superior, to the polyethylenimine (PEI) standard. Importantly, minimal cytotoxicty was induced in the cells. These functional polycarbonates therefore have the potential to be a useful non-viral vector for gene therapy.

Developmentally-inspired shrink-wrap polymers for mechanical induction of tissue differentiation.

PubMed

Hashmi, Basma; Zarzar, Lauren D; Mammoto, Tadanori; Mammoto, Akiko; Jiang, Amanda; Aizenberg, Joanna; Ingber, Donald E

2014-05-28

A biologically inspired thermoresponsive polymer has been developed that mechanically induces tooth differentiation in vitro and in vivo by promoting mesenchymal cell compaction as seen in each pore of the scaffold. This normally occurs during the physiological mesenchymal condensation response that triggers tooth formation in the embryo. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sonochemical synthesis and structural characterization of a new nanostructured Co(II) supramolecular coordination polymer with Lewis base sites as a new catalyst for Knoevenagel condensation.

PubMed

Joharian, Monika; Abedi, Sedigheh; Morsali, Ali

2017-11-01

A new Co(II) mixed-ligand coordination supramolecular polymer with composition [Co 2 (ppda)(4-bpdh) 2 (NO 3 ) 2 ] n (1) (where, ppda=p-phenylenediacrylic acid, 4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) was synthesized using solvothermal, mechanochemical and sonochemical methods. Compound 1 and the new nanostructure have been characterized by single-crystal X-ray, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) analysis and scanning electron microscopy (SEM). The thermal stability of compound 1 was also studied by thermal gravimetric analysis (TGA). The surface area of these compounds was determined by BET. The single-crystal X-ray data shows a new interesting two-dimensional coordination polymer (CP). In addition, the effect of various sonication concentrations of initial reagents, power of ultrasound irradiation and also the time on the size and morphology of nano-structured coordination polymer 1 were evaluated. Moreover, it has been demonstrated that the nanostructure of the CP1 can be used as a catalyst in Knoevenagel condensation reaction. Copyright © 2017 Elsevier B.V. All rights reserved.

Process for restoring membrane permeation properties

DOEpatents

Pinnau, Ingo; Toy, Lora G.; Casillas, Carlos G.

1997-05-20

A process for restoring the selectivity of high-flee-volume, glassy polymer membranes for condensable components over less-condensable components or non-condensable components of a gas mixture. The process involves exposing the membrane to suitable sorbent vapor, such as propane or butane, thereby reopening the microvoids that make up the free volume. The selectivity of an aged membrane may be restored to 70-100% of its original value. The selectivity of a membrane which is known to age over time can also be maintained by keeping the membrane in a vapor environment when it is not in use.

Process for restoring membrane permeation properties

DOEpatents

Pinnau, I.; Toy, L.G.; Casillas, C.G.

1997-05-20

A process is described for restoring the selectivity of high-free-volume, glassy polymer membranes for condensable components over less-condensable components or non-condensable components of a gas mixture. The process involves exposing the membrane to suitable sorbent vapor, such as propane or butane, thereby reopening the microvoids that make up the free volume. The selectivity of an aged membrane may be restored to 70--100% of its original value. The selectivity of a membrane which is known to age over time can also be maintained by keeping the membrane in a vapor environment when it is not in use. 8 figs.

A Novel Method for Preparing Auxetic Foam from Closed-cell Polymer Foam Based on Steam Penetration and Condensation (SPC) Process.

PubMed

Fan, Donglei; Li, Minggang; Qiu, Jian; Xing, Haiping; Jiang, Zhiwei; Tang, Tao

2018-05-31

Auxetic materials are a class of materials possessing negative Poisson's ratio. Here we establish a novel method for preparing auxetic foam from closed-cell polymer foam based on steam penetration and condensation (SPC) process. Using polyethylene (PE) closed-cell foam as an example, the resultant foams treated by SPC process present negative Poisson's ratio during stretching and compression testing. The effect of steam-treated temperature and time on the conversion efficiency of negative Poisson's ratio foam is investigated, and the mechanism of SPC method for forming re-entrant structure is discussed. The results indicate that the presence of enough steam within the cells is a critical factor for the negative Poisson's ratio conversion in the SPC process. The pressure difference caused by steam condensation is the driving force for the conversion from conventional closed-cell foam to the negative Poisson's ratio foam. Furthermore, the applicability of SPC process for fabricating auxetic foam is studied by replacing PE foam by polyvinyl chloride (PVC) foam with closed-cell structure or replacing water steam by ethanol steam. The results verify the universality of SPC process for fabricating auxetic foams from conventional foams with closed-cell structure. In addition, we explored potential application of the obtained auxetic foams by SPC process in the fabrication of shape memory polymer materials.

Optical enhancing durable anti-reflective coating

DOEpatents

Maghsoodi, Sina; Varadarajan, Aravamuthan; Movassat, Meisam

2016-07-05

Disclosed herein are polysilsesquioxane based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In embodiments, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in the polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, Si--OH condensation catalyst and/or nanofillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes including flow coating and roll coating, and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

High gain durable anti-reflective coating

DOEpatents

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev R.

2016-07-26

Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers, Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

Synthesis and characterization of amphiphilic block polymer poly(ethylene glycol)-poly(propylene carbonate)-poly(ethylene glycol) for drug delivery.

PubMed

Li, Hongchun; Niu, Yongsheng

2018-08-01

A novel amphiphilic block polymer poly(ethylene glycol)-poly(propylene carbonate)-poly(ethylene glycol) (PEG-PPC-PEG) was synthesized via the dicyclohexylcarbodiimide condensation reaction of double PEG-bis-amine and HOOC-PPC-COOH. The obtained copolymer was characterized by NMR to determine its structure. Using the PEG-PPC-PEG as the carrier and using doxorubicin (DOX) as a model drug, DOX-loaded nanoparticles with core shell structure were synthesized by self-assembly in water. The nanoparticles properties such as particle size, drug loading, encapsulation efficiency (EE) and drug release behavior were investigated as a function of the hydrophobic block length of PPC segments and compared with each other. The results showed that the EE was up to 88.8%. Nanoparticles were found to have a certain effect on the controlled release of DOX. Copyright © 2018 Elsevier B.V. All rights reserved.

Interference of condensed tannin in lignin analyses of dry bean and forage crops.

PubMed

Marles, M A Susan; Coulman, Bruce E; Bett, Kirstin E

2008-11-12

Legumes with high concentrations of condensed tannin (pinto bean [Phaseolus vulgaris L.], sainfoin [Onobrychis viciifolia Scop.], and big trefoil [Lotus uliginosus Hoff.]), were compared to a selection of forages, with low or zero condensed tannin (smooth bromegrass [ Bromus inermis Leyss], Lotus japonicus [Regel] K. Larsen, and alfalfa [Medicago sativa L.]), using four methods to estimate fiber or lignin. Protocols were validated by using semipurified condensed tannin polymers in adulteration assays that tested low-lignin tissue with polyphenolic-enriched samples. The effect on lignin assay methods by condensed tannin concentration was interpreted using a multivariate analysis. There was an overestimation of fiber or lignin in the presence of condensed tannin in the acid detergent fiber (ADF) and Klason lignin (KL) assays compared to that in the thioglycolic acid (TGA) and acid detergent lignin (ADL) methods. Sulfite reagents (present in TGA lignin method) or sequential acidic digests at high temperatures (ADF followed by ADL) were required to eliminate condensed tannin. The ADF (alone) and KL protocols are not recommended to screen nonwoody plants, such as forages, where condensed tannin has accumulated in the tissue.

Electrochemical Coupling of Biomass-Derived Acids: New C8 Platforms for Renewable Polymers and Fuels.

PubMed

Wu, Linglin; Mascal, Mark; Farmer, Thomas J; Arnaud, Sacha Pérocheau; Wong Chang, Maria-Angelica

2017-01-10

Electrolysis of biomass-derived carbonyl compounds is an alternative to condensation chemistry for supplying products with chain length >C 6 for biofuels and renewable materials production. Kolbe coupling of biomass-derived levulinic acid is used to obtain 2,7-octanedione, a new platform molecule only two low process-intensity steps removed from raw biomass. Hydrogenation to 2,7-octanediol provides a chiral secondary diol largely unknown to polymer chemistry, whereas intramolecular aldol condensation followed by hydrogenation yields branched cycloalkanes suitable for use as high-octane, cellulosic gasoline. Analogous electrolysis of an itaconic acid-derived methylsuccinic monoester yields a chiral 2,5-dimethyladipic acid diester, another underutilized monomer owing to lack of availability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Antibacterial Cell Division Inhibitor PC190723 Is an FtsZ Polymer-stabilizing Agent That Induces Filament Assembly and Condensation*

PubMed Central

Andreu, José M.; Schaffner-Barbero, Claudia; Huecas, Sonia; Alonso, Dulce; Lopez-Rodriguez, María L.; Ruiz-Avila, Laura B.; Núñez-Ramírez, Rafael; Llorca, Oscar; Martín-Galiano, Antonio J.

2010-01-01

Cell division protein FtsZ can form single-stranded filaments with a cooperative behavior by self-switching assembly. Subsequent condensation and bending of FtsZ filaments are important for the formation and constriction of the cytokinetic ring. PC190723 is an effective bactericidal cell division inhibitor that targets FtsZ in the pathogen Staphylococcus aureus and Bacillus subtilis and does not affect Escherichia coli cells, which apparently binds to a zone equivalent to the binding site of the antitumor drug taxol in tubulin (Haydon, D. J., Stokes, N. R., Ure, R., Galbraith, G., Bennett, J. M., Brown, D. R., Baker, P. J., Barynin, V. V., Rice, D. W., Sedelnikova, S. E., Heal, J. R., Sheridan, J. M., Aiwale, S. T., Chauhan, P. K., Srivastava, A., Taneja, A., Collins, I., Errington, J., and Czaplewski, L. G. (2008) Science 312, 1673–1675). We have found that the benzamide derivative PC190723 is an FtsZ polymer-stabilizing agent. PC190723 induced nucleated assembly of Bs-FtsZ into single-stranded coiled protofilaments and polymorphic condensates, including bundles, coils, and toroids, whose formation could be modulated with different solution conditions. Under conditions for reversible assembly of Bs-FtsZ, PC190723 binding reduced the GTPase activity and induced the formation of straight bundles and ribbons, which was also observed with Sa-FtsZ but not with nonsusceptible Ec-FtsZ. The fragment 2,6-difluoro-3-methoxybenzamide also induced Bs-FtsZ bundling. We propose that polymer stabilization by PC190723 suppresses in vivo FtsZ polymer dynamics and bacterial division. The biochemical action of PC190723 on FtsZ parallels that of the microtubule-stabilizing agent taxol on the eukaryotic structural homologue tubulin. Both taxol and PC190723 stabilize polymers against disassembly by preferential binding to each assembled protein. It is yet to be investigated whether both ligands target structurally related assembly switches. PMID:20212044

Preparation of Perfluorinated Imidoylamidoxime Polymers

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Kratzer, R. H.; Paciorek, K. J. L.; Ito, T. I.

1982-01-01

Perfluorinated imidoylamidoxime polymers with excellent resistance to heat, chemicals and solvents are prepared by condensing a perfluorinated nitrile with a perfluorinated amidoxime in vacuum or inert atmosphere from 20 degrees to 70 degrees C. When both reactants are difunctional, oligomeric or polymeric products are obtained. After cyclization of imidoylamidoxime groups to 1,2,4-oxadiazole linkages, process yields highly resistant elastomers. Competing side reactions are inhibited by low processing temperature.

BOOK REVIEW: Soft Condensed Matter

NASA Astrophysics Data System (ADS)

Jones, Richard A. L.

2002-11-01

The author states in the preface of the book that the aim is '...to give a unified overview of the various aspects of the physics of soft condensed matter'. The book succeeds in fulfilling this aim in many respects. i) The style is fluent and concise and gives the necessary explanations to make its content understandable to people with some knowledge of the basic principles of physics. ii) The content of the book is complete enough to give a panoramic view of the landscape of soft condensed matter. The first two chapters give, respectively, a short introduction and a presentation of forces, energies and timescales, giving a general overview and pointing out the particular importance of different aspects such as timescales, which are much more important in soft condensed matter than in traditional or 'hard' condensed matter. The next chapter, devoted to phase transition, recalls that the equilibrium between two phases is controlled by free energy considerations. Spinodal decomposition is presented as a counterpart of nucleation and growth. Again, characteristic length scales are considered and applied to a phase separation mixture of polymers in a common solvent. The following three chapters are devoted respectively to specific topics: colloidal dispersion, polymers and gelation. The stability and phase behaviour of colloids are related to the interaction between colloidal particles. Properties of colloidal crystals as well as colloidal dispersion are depicted in terms of stabilization of crystalline colloids. The flow properties of colloidal dispersion are presented in terms of free energy minimization and the structure of the dispersion. After a brief introduction to polymer chemistry and architecture, the coil-globule transition is discussed. Viscoelasticity of polymers is described and discussed by introducing the notion of entanglement. This leads to the introduction of the tube model and the theory of reptation. The sol-gel transition is presented phenomenologically and formulated through the current percolation model and the Flory-Stockmayer model. The next two chapters consider the molecular order in soft condensed matter. The rich complexity of liquid crystals is emphasized and the Frederiks transition is described in relation to liquid crystal displays. The crystallinity in polymers is discussed and its usual semi-crystallinity presented as a consequence of entanglement and timescales. The next chapter describes the self-assembly of phases and the great importance of the self-assembly phenomenon in solutions of amphiphilic molecules is largely discussed in several specific phenomena. The book ends with a chapter devoted to the description of soft matter realizations in nature. Special attention is paid to the components and structure of life: nucleic acids, proteins, polysaccharides and membranes. There are two appendixes recalling the basic concepts of thermodynamics and statistical mechanics. In each chapter, several problems are included, and solutions to a selection of them are given. The bibliography proposed is pertinent and each chapter gives details of further reading, mostly addressed to known books on the topic. iii) The presentation of the book is good. Throughout the book, the relevant, basic or new concepts of each topic are typed in bold characters and succinctly defined. The figures are abundant and adequately illustrate the text either by plots of experimental data or by computed predictions from models. Many schematic representations of structures, molecular distributions or arrangements are also included. In summary, the author has succeeded in producing a scientifically rigorous book of affordable size (around 200 pages) that is well illustrated (about 120 figures) and written in a fluent style that describes the many different physical phenomena involved in soft condensed matter. N Clavaguera

Degradable Polymer with Protein Resistance in a Marine Environment.

PubMed

Ma, Jielin; Ma, Chunfeng; Zhang, Guangzhao

2015-06-16

Protein resistance is the central issue in marine antibiofouling. We have prepared poly(ε-caprolactone) (PCL)-based polyurethane with 2-(dimethylamino) ethyl methacrylate (DEM) as pendant groups by a combination of the thiol-ene click reaction and the condensation reaction. By the use of quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR), we have investigated the adsorption of fibrinogen, bovine serum albumin (BSA), and lysozyme on the polymer surface. The polymer exhibits protein resistance in seawater but not in fresh water because DEM pendant groups carry net neutral charges in the former. The evaluation of antibacterial adhesion of the polymer by using Micrococcus luteus demonstrates that the polymer can effectively inhibit the settlement of marine bacteria. Our studies also show that the polymer is degradable in marine environments.

Highly Selective Membranes For The Separation Of Organic Vapors Using Super-Glassy Polymers

DOEpatents

Pinnau, Ingo; Lokhandwala, Kaaeid; Nguyen, Phuong; Segelke, Scott

1997-11-18

A process for separating hydrocarbon gases of low boiling point, particularly methane, ethane and ethylene, from nitrogen. The process is performed using a membrane made from a super-glassy material. The gases to be separated are mixed with a condensable gas, such as a C.sub.3+ hydrocarbon. In the presence of the condensable gas, improved selectivity for the low-boiling-point hydrocarbon gas over nitrogen is achieved.

Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

PubMed

Weiber, E Annika; Jannasch, Patric

2014-09-01

A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antioxidant tannins from stem bark and fine root of Casuarina equisetifolia.

PubMed

Zhang, Shang-Ju; Lin, Yi-Ming; Zhou, Hai-Chao; Wei, Shu-Dong; Lin, Guang-Hui; Ye, Gong-Fu

2010-08-16

Structures of condensed tannins from the stem bark and fine root of Casuarina equisetifolia were identified using MALDI-TOF MS and HPLC analyses. The condensed tannins from stem bark and fine root consist predominantly of procyanidin combined with prodelphinidin and propelargonidin, and epicatechin is the main extension unit. The condensed tannins had different polymer chain lengths, varying from trimers to tridecamer for stem bark and to pentadecamer for fine root. The antioxidant activities were measured by two models: 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing/ antioxidant power (FRAP). The condensed tannins extracted from C. equisetifolia showed very good DPPH radical scavenging activity and ferric reducing/ antioxidant power, suggesting that these extracts may be considered as new sources of natural antioxidants for food and nutraceutical products.

Cured composite materials for reactive metal battery electrolytes

DOEpatents

Harrup, Mason K.; Stewart, Frederick F.; Peterson, Eric S.

2006-03-07

A solid molecular composite polymer-based electrolyte is made for batteries, wherein silicate compositing produces a electrolytic polymer with a semi-rigid silicate condensate framework, and then mechanical-stabilization by radiation of the outer surface of the composited material is done to form a durable and non-tacky texture on the electrolyte. The preferred ultraviolet radiation produces this desirable outer surface by creating a thin, shallow skin of crosslinked polymer on the composite material. Preferably, a short-duration of low-medium range ultraviolet radiation is used to crosslink the polymers only a short distance into the polymer, so that the properties of the bulk of the polymer and the bulk of the molecular composite material remain unchanged, but the tough and stable skin formed on the outer surface lends durability and processability to the entire composite material product.

The effect of water on thermal stresses in polymer composites

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

1994-01-01

The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

Phosphorus-containing imide resins

NASA Technical Reports Server (NTRS)

Varma, I. K.; Fohlen, G. M.; Parker, J. A. (Inventor)

1985-01-01

Cured polymers of bis and tris-imides derived from tris(m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, and addition polymers of such imides, including a variant in which a monoimide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride prior to curing are disclosed and claimed. Such polymers are flame resistant. Also disclosed are an improved method of producing tris(m-aminophenyl) phosphine oxides from the nitro analogues by reduction with hydrazine hydrate using palladized charcoal or Raney nickel as the catalyst and fiber reinforced cured resin composites.

Environmental durability diagnostic for printed identification codes of polymer insulation for distribution pipelines

NASA Astrophysics Data System (ADS)

Zhuravleva, G. N.; Nagornova, I. V.; Kondratov, A. P.; Bablyuk, E. B.; Varepo, L. G.

2017-08-01

A research and modelling of weatherability and environmental durability of multilayer polymer insulation of both cable and pipelines with printed barcodes or color identification information were performed. It was proved that interlayer printing of identification codes in distribution pipelines insulation coatings provides high marking stability to light and atmospheric condensation. This allows to carry out their distant damage control. However, microbiological fouling of upper polymer layer hampers the distant damage pipelines identification. The color difference values and density changes of PE and PVC printed insolation due to weather and biological factors were defined.

A mapping variable ring polymer molecular dynamics study of condensed phase proton-coupled electron transfer

NASA Astrophysics Data System (ADS)

Pierre, Sadrach; Duke, Jessica R.; Hele, Timothy J. H.; Ananth, Nandini

2017-12-01

We investigate the mechanisms of condensed phase proton-coupled electron transfer (PCET) using Mapping-Variable Ring Polymer Molecular Dynamics (MV-RPMD), a recently developed method that employs an ensemble of classical trajectories to simulate nonadiabatic excited state dynamics. Here, we construct a series of system-bath model Hamiltonians for the PCET, where four localized electron-proton states are coupled to a thermal bath via a single solvent mode, and we employ MV-RPMD to simulate state population dynamics. Specifically, for each model, we identify the dominant PCET mechanism, and by comparing against rate theory calculations, we verify that our simulations correctly distinguish between concerted PCET, where the electron and proton transfer together, and sequential PCET, where either the electron or the proton transfers first. This work represents a first application of MV-RPMD to multi-level condensed phase systems; we introduce a modified MV-RPMD expression that is derived using a symmetric rather than asymmetric Trotter discretization scheme and an initialization protocol that uses a recently derived population estimator to constrain trajectories to a dividing surface. We also demonstrate that, as expected, the PCET mechanisms predicted by our simulations are robust to an arbitrary choice of the initial dividing surface.

Nanostructured polymer-titanium composites and titanium oxide through polymer swelling in titania precursor.

PubMed

Kierys, A; Zaleski, R; Buda, W; Pikus, S; Dziadosz, M; Goworek, J

2013-06-01

Polymer (XAD7HP)/Ti 4+ nanocomposites were prepared through the swelling of polymer in titanium (IV) ethoxide as a titanium dioxide precursor. The nanocomposite beads exhibit relatively high porosity different than the porosity of the initial polymer. Thermal treatment of composite particles up to 200 °C in vacuum causes the change of their internal structure. At higher temperature, the components of composite become more tightly packed. Calcination at 600 °C and total removal of polymer produce spherically shaped TiO 2 condensed phase as determined by XRD. Thermally treated composites show the substantial change of pore dimensions within micro- and mesopores. The presence of micropores and their transformation during thermal processing was studied successfully by positron annihilation lifetime spectroscopy (PALS). The results derived from PALS experiment were compared with those obtaining from low-temperature nitrogen adsorption data.

High gain durable anti-reflective coating

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

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.

Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers,more » Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.« less

Screening Nylon-3 Polymers, a New Class of Cationic Amphiphiles, for siRNA Delivery

PubMed Central

2015-01-01

Amphiphilic nucleic acid carriers have attracted strong interest. Three groups of nylon-3 copolymers (poly-β-peptides) possessing different cationic/hydrophobic content were evaluated as siRNA delivery agents in this study. Their ability to condense siRNA was determined in SYBR Gold assays. Their cytotoxicity was tested by MTT assays, their efficiency of delivering Alexa Fluor-488-labeled siRNA intracellularly in the presence and absence of uptake inhibitors was assessed by flow cytometry, and their transfection efficacies were studied by luciferase knockdown in a cell line stably expressing luciferase (H1299/Luc). Endosomal release was determined by confocal laser scanning microscopy and colocalization with lysotracker. All polymers efficiently condensed siRNA at nitrogen-to-phosphate (N/P) ratios of 5 or lower, as reflected in hydrodynamic diameters smaller than that at N/P 1. Although several formulations had negative zeta potentials at N/P 1, G2C and G2D polyplexes yielded >80% uptake in H1299/Luc cells, as determined by flow cytometry. Luciferase knockdown (20–65%) was observed after transfection with polyplexes made of the high molecular weight polymers that were the most hydrophobic. The ability of nylon-3 polymers to deliver siRNA intracellularly even at negative zeta potential implies that they mediate transport across cell membranes based on their amphiphilicity. The cellular uptake route was determined to strongly depend on the presence of cholesterol in the cell membrane. These polymers are, therefore, very promising for siRNA delivery at reduced surface charge and toxicity. Our study identified nylon-3 formulations at low N/P ratios for effective gene knockdown, indicating that nylon-3 polymers are a new, promising type of gene delivery agent. PMID:25437915

Screening nylon-3 polymers, a new class of cationic amphiphiles, for siRNA delivery.

PubMed

Nadithe, Venkatareddy; Liu, Runhui; Killinger, Bryan A; Movassaghian, Sara; Kim, Na Hyung; Moszczynska, Anna B; Masters, Kristyn S; Gellman, Samuel H; Merkel, Olivia M

2015-02-02

Amphiphilic nucleic acid carriers have attracted strong interest. Three groups of nylon-3 copolymers (poly-β-peptides) possessing different cationic/hydrophobic content were evaluated as siRNA delivery agents in this study. Their ability to condense siRNA was determined in SYBR Gold assays. Their cytotoxicity was tested by MTT assays, their efficiency of delivering Alexa Fluor-488-labeled siRNA intracellularly in the presence and absence of uptake inhibitors was assessed by flow cytometry, and their transfection efficacies were studied by luciferase knockdown in a cell line stably expressing luciferase (H1299/Luc). Endosomal release was determined by confocal laser scanning microscopy and colocalization with lysotracker. All polymers efficiently condensed siRNA at nitrogen-to-phosphate (N/P) ratios of 5 or lower, as reflected in hydrodynamic diameters smaller than that at N/P 1. Although several formulations had negative zeta potentials at N/P 1, G2C and G2D polyplexes yielded >80% uptake in H1299/Luc cells, as determined by flow cytometry. Luciferase knockdown (20-65%) was observed after transfection with polyplexes made of the high molecular weight polymers that were the most hydrophobic. The ability of nylon-3 polymers to deliver siRNA intracellularly even at negative zeta potential implies that they mediate transport across cell membranes based on their amphiphilicity. The cellular uptake route was determined to strongly depend on the presence of cholesterol in the cell membrane. These polymers are, therefore, very promising for siRNA delivery at reduced surface charge and toxicity. Our study identified nylon-3 formulations at low N/P ratios for effective gene knockdown, indicating that nylon-3 polymers are a new, promising type of gene delivery agent.

Accelerating research into bio-based FDCA-polyesters by using small scale parallel film reactors.

PubMed

Gruter, Gert-Jan M; Sipos, Laszlo; Adrianus Dam, Matheus

2012-02-01

High Throughput experimentation has been well established as a tool in early stage catalyst development and catalyst and process scale-up today. One of the more challenging areas of catalytic research is polymer catalysis. The main difference with most non-polymer catalytic conversions is the fact that the product is not a well defined molecule and the catalytic performance cannot be easily expressed only in terms of catalyst activity and selectivity. In polymerization reactions, polymer chains are formed that can have various lengths (resulting in a molecular weight distribution rather than a defined molecular weight), that can have different compositions (when random or block co-polymers are produced), that can have cross-linking (often significantly affecting physical properties), that can have different endgroups (often affecting subsequent processing steps) and several other variations. In addition, for polyolefins, mass and heat transfer, oxygen and moisture sensitivity, stereoregularity and many other intrinsic features make relevant high throughput screening in this field an incredible challenge. For polycondensation reactions performed in the melt often the viscosity becomes already high at modest molecular weights, which greatly influences mass transfer of the condensation product (often water or methanol). When reactions become mass transfer limited, catalyst performance comparison is often no longer relevant. This however does not mean that relevant experiments for these application areas cannot be performed on small scale. Relevant catalyst screening experiments for polycondensation reactions can be performed in very efficient small scale parallel equipment. Both transesterification and polycondensation as well as post condensation through solid-stating in parallel equipment have been developed. Next to polymer synthesis, polymer characterization also needs to be accelerated without making concessions to quality in order to draw relevant conclusions.

Dropwise condensation

PubMed Central

Leach, R. N.; Stevens, F.; Langford, S. C.; Dickinson, J. T.

2008-01-01

Dropwise condensation of water vapor from a naturally cooling, hot water reservoir onto a hydrophobic polymer film and a silanized glass slide was studied by direct observation and simulations. The observed drop growth kinetics suggest that smallest drops grow principally by the diffusion of water adsorbed on the substrate to the drop perimeter, while drops larger than 50 μm in diameter grow principally by direct deposition from the vapor onto the drop surface. Drop coalescence plays a critical role in determining the drop size distribution, and stimulates the nucleation of new, small drops on the substrates. Simulations of drop growth incorporating these growth mechanisms provide a good description of the observed drop size distribution. Because of the large role played by coalescence, details of individual drop growth make little difference to the final drop size distribution. The rate of condensation per unit substrate area is especially high for the smallest drops, and may help account for the high heat transfer rates associated with dropwise condensation relative to filmwise condensation in heat exchange applications. PMID:17014129

Multifunctional nanocomposites of lanthanide (Eu3+, Tb3+) complexes functionalized magnetic mesoporous silica nanospheres covalently bonded with polymer modified ZnO.

PubMed

Yan, Bing; Shao, Yan-Fei

2013-07-14

Methacrylic-group-modified ZnO nanoparticles (designated ZnO-MAA) prepared through the sol-gel process are copolymerized with 2-hydroxyethyl methacrylate (HEMA) to form ZnO-MAA-PHEMA hybrid system. ZnO-MAA-PHEMA unit is functionalized with 3-(triethoxysilyl)-propyl isocyanate (TEPIC) to form ZnO-MAA-PHEMA-Si hybrids, and then is incorporated with oleic acid-modified Fe3O4 nanoparticles by co-condensation of tetraethoxysilane (TEOS) and ZnO-MAA-PHEMA-Si. Subsequently, ZnO-polymer covalently bonded mesoporous silica nanospheres are assembled using cetyltrimethylammonium bromide (CTAB) surfactant as template. Furthermore, lanthanide (Eu(3+), Tb(3+)) complexes with nicotinic acid (NTA), isonicotinic acid (INTA) and 2-chloronicotinic (CNTA) are introduced by coordination bonds, resulting in the final multifunctional nanocomposites. The detailed physical characterization of these hybrids is discussed in detail. It reveals that they possess both magnetic and luminescent properties. Especially Eu(ZnO-MMS)(CNTA)3 and Tb(ZnO-MMS)(NTA)3 present high quantum yield values of 32.2% and 68.5%, respectively. The results will lay the foundation for further application in biomedical and biopharmaceutical fields.

A comparison of thiolated and disulfide-crosslinked polyethylenimine for nonviral gene delivery.

PubMed

Aravindan, Latha; Bicknell, Katrina A; Brooks, Gavin; Khutoryanskiy, Vitaliy V; Williams, Adrian C

2013-09-01

Branched polyethylenimine (25 kDa) is thiolated and compared with redox-sensitive crosslinked derivatives. Both polymers thiol contents are assessed; the thiolated polymers have 390-2300 mmol SH groups/mol, whereas the crosslinked polymers have lower thiol contents. Cytotoxicity assays show that both modified polymers give lower hemolysis than unmodified PEI. Increased thiol content increases gene transfer efficiency but also elevates cytotoxicity. Crosslinking improves plasmid DNA condensation and enhances transfection efficiency, but extensive crosslinking overstabilizes the polyplexes and decreases transfection, emphasizing the need to balance polyplex stabilization and unpacking. Thus, at low levels of crosslinking, 25 kDa PEI can be an efficient redox-sensitive carrier system. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Evaluation of Polymer Coatings for the Promotion of Dropwise Condensation of Steam.

DTIC Science & Technology

1984-03-01

thermosetting, modi- fied polyester insulating varnish . Although not expected to perfcrm as %ell as the fluorinated compounds, ease of appli- cation...xylylene which can he vapor deposited in very thin films. Unlike PTEE, parylene-N contains no fluorine and therefore would nct be expected to be as...perform. Knowing that water has a surface tensicz of approximately 71.9 dynes/cm and riferring tc Table I, it can be seen that the fluorinated polymers

Intrinsic immunogenicity of rapidly-degradable polymers evolves during degradation.

PubMed

Andorko, James I; Hess, Krystina L; Pineault, Kevin G; Jewell, Christopher M

2016-03-01

Recent studies reveal many biomaterial vaccine carriers are able to activate immunostimulatory pathways, even in the absence of other immune signals. How the changing properties of polymers during biodegradation impact this intrinsic immunogenicity is not well studied, yet this information could contribute to rational design of degradable vaccine carriers that help direct immune response. We use degradable poly(beta-amino esters) (PBAEs) to explore intrinsic immunogenicity as a function of the degree of polymer degradation and polymer form (e.g., soluble, particles). PBAE particles condensed by electrostatic interaction to mimic a common vaccine approach strongly activate dendritic cells, drive antigen presentation, and enhance T cell proliferation in the presence of antigen. Polymer molecular weight strongly influences these effects, with maximum stimulation at short degradation times--corresponding to high molecular weight--and waning levels as degradation continues. In contrast, free polymer is immunologically inert. In mice, PBAE particles increase the numbers and activation state of cells in lymph nodes. Mechanistic studies reveal that this evolving immunogenicity occurs as the physicochemical properties and concentration of particles change during polymer degradation. This work confirms the immunological profile of degradable, synthetic polymers can evolve over time and creates an opportunity to leverage this feature in new vaccines. Degradable polymers are increasingly important in vaccination, but how the inherent immunogenicity of polymers changes during degradation is poorly understood. Using common rapidly-degradable vaccine carriers, we show that the activation of immune cells--even in the absence of other adjuvants--depends on polymer form (e.g., free, particulate) and the extent of degradation. These changing characteristics alter the physicochemical properties (e.g., charge, size, molecular weight) of polymer particles, driving changes in immunogenicity. Our results are important as many common biomaterials (e.g., PLGA) are now known to exhibit immune activity that alters how vaccines are processed. Thus, the results of this study could contribute to more rational design of biomaterial carriers that also actively direct the properties of responses generated by vaccines. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Highly ordered nanocomposites via a monomer self-assembly in situ condensation approach

DOEpatents

Gin, D.L.; Fischer, W.M.; Gray, D.H.; Smith, R.C.

1998-12-15

A method for synthesizing composites with architectural control on the nanometer scale is described. A polymerizable lyotropic liquid-crystalline monomer is used to form an inverse hexagonal phase in the presence of a second polymer precursor solution. The monomer system acts as an organic template, providing the underlying matrix and order of the composite system. Polymerization of the template in the presence of an optional cross-linking agent with retention of the liquid-crystalline order is carried out followed by a second polymerization of the second polymer precursor within the channels of the polymer template to provide an ordered nanocomposite material. 13 figs.

Highly ordered nanocomposites via a monomer self-assembly in situ condensation approach

DOEpatents

Gin, Douglas L.; Fischer, Walter M.; Gray, David H.; Smith, Ryan C.

1998-01-01

A method for synthesizing composites with architectural control on the nanometer scale is described. A polymerizable lyotropic liquid-crystalline monomer is used to form an inverse hexagonal phase in the presence of a second polymer precursor solution. The monomer system acts as an organic template, providing the underlying matrix and order of the composite system. Polymerization of the template in the presence of an optional cross-linking agent with retention of the liquid-crystalline order is carried out followed by a second polymerization of the second polymer precursor within the channels of the polymer template to provide an ordered nanocomposite material.

Polyhydric polymer-functionalized fluorescent probe with enhanced aqueous solubility and specific ion recognition: A test strips-based fluorimetric strategy for the rapid and visual detection of Fe3+ ions.

PubMed

Duan, Zhiqiang; Zhang, Chunxian; Qiao, Yuchun; Liu, Fengjuan; Wang, Deyan; Wu, Mengfan; Wang, Ke; Lv, Xiaoxia; Kong, Xiangmu; Wang, Hua

2017-08-01

A polyhydric polymer-functionalized probe with enhanced aqueous solubility was designed initially by coupling 1-pyrenecarboxyaldehyde (Pyr) onto poly(vinyl alcohol) (PVA) via the one-step condensation reaction. Polyhydric PVA polymer chains could facilitate the Pyr fluorophore with largely improved aqueous solubility and especially strong cyan fluorescence. Importantly, the fluorescence of the PVA-Pyr probes could thereby be quenched specifically by Fe 3+ ions through the strong PVA-Fe 3+ interaction triggering the polymeric probe aggregation. Furthermore, a test strips-based fluorimetric method was developed with the stable and uniform probe distribution by taking advantage of the unique film-forming ability and the depression capacity of "coffee-stain" effects of PVA matrix. The as-developed test strips could allow for the rapid and visual detections of Fe 3+ ions simply by a dipping way, showing a linear concentration range of 5.00-300μM, with the detection limit of 0.73μM. Moreover, the proposed method was applied to the evaluation of Fe 3+ ions in natural water samples, showing the analysis performances better or comparable to those of current detection techniques. This test strips-based fluorimetric strategy promises the extensive applications for the rapid on-site monitoring of Fe 3+ ions in environmental water and the outdoor finding of the potential iron mines. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of an impact- and solvent-resistant thermoplastic composite matrix

NASA Technical Reports Server (NTRS)

Delano, C. B.; Kiskiras, C. J.

1984-01-01

Synthesis, moldability and chloroform, acetone and tricresyl phosphate resistance of 16 polymer compositions are described. These aliphatic heterocyclic polymers include polyimides, polybenzimidazoles, and N-arylenepolybenzimidazoles. A solution condensation (cresol) method to prepare imidized aliphaic polyimides is described. Two polyimides and one polybenzimidazole demonstrate no crazing or cracking during 500 hr exposure to the cited solvents under stress. Modification of one aliphatic polyimide with several aromatic amines suggests that m-phenylenediamine is singular in its behavior to improve the chloroform resistance of that class of polyimides.

Methods for the synthesis of polysilanes

DOEpatents

Zeigler, John M.

1991-01-01

A method of controlling the yield of polysilane of a desired molecular weight and/or polydispersity prepared in a reductive condensation of corresponding silane monomers on a solid catalyst dispersed in an inert solvent for both the monomers and the growing polymer chains, comprises determining the variation of molecular weight and/or polydispersity of the polysilane as a function of the solubility of the polysilane in reaction solvent, determining thereby a chosen optimum solubility of the polysilane in solvent for obtaining a desired yield of polysilane of said desired molecular weight and/or polydispersity, and thereafter carrying out the preparation of the polysilane in a solvent in which the polysilane has said chosen optimum solubility.

Balancing cationic and hydrophobic content of PEGylated siRNA polyplexes enhances endosome escape, stability, blood circulation time, and bioactivity in vivo.

PubMed

Nelson, Christopher E; Kintzing, James R; Hanna, Ann; Shannon, Joshua M; Gupta, Mukesh K; Duvall, Craig L

2013-10-22

A family of pH-responsive diblock polymers composed of poly[(ethylene glycol)-b-[(2-(dimethylamino)ethyl methacrylate)-co-(butyl methacrylate)], PEG-(DMAEMA-co-BMA), was reversible addition-fragmentation chain transfer (RAFT) synthesized with 0-75 mol % BMA in the second polymer block. The relative mole % of DMAEMA and BMA was varied in order to identify a polymer that can be used to formulate PEGylated, siRNA-loaded polyplex nanoparticles (NPs) with an optimized balance of cationic and hydrophobic content in the NP core based on siRNA packaging, cytocompatibility, blood circulation half-life, endosomal escape, and in vivo bioactivity. The polymer with 50:50 mol % of DMAEMA:BMA (polymer "50 B") in the RAFT-polymerized block efficiently condensed siRNA into 100 nm NPs that displayed pH-dependent membrane disruptive behavior finely tuned for endosomal escape. In vitro delivery of siRNA with polymer 50 B produced up to 94% protein-level knockdown of the model gene luciferase. The PEG corona of the NPs blocked nonspecific interactions with constituents of human whole blood, and the relative hydrophobicity of polymer 50 B increased NP stability in the presence of human serum or the polyanion heparin. When injected intravenously, 50 B NPs enhanced blood circulation half-life 3-fold relative to more standard PEG-DMAEMA (0 B) NPs (p < 0.05), due to improved stability and a reduced rate of renal clearance. The 50 B NPs enhanced siRNA biodistribution to the liver and other organs and significantly increased gene silencing in the liver, kidneys, and spleen relative to the benchmark polymer 0 B (p < 0.05). These collective findings validate the functional significance of tuning the balance of cationic and hydrophobic content of polyplex NPs utilized for systemic siRNA delivery in vivo.

Sweet Vector for Gene Delivery: the Sugar Decoration of Polyplexes Reduces Cytotoxicity with a Balanced Effect on Gene Expression.

PubMed

Albuquerque, Lindomar J C; Alavarse, Alex C; Carlan da Silva, Maria C; Zilse, Morgana S; Barth, Maitê T; Bellettini, Ismael C; Giacomelli, Fernando C

2018-02-01

The use of sugar-functionalized polyplexes as a nonviral gene delivery vector with lower cytotoxicity than the well-known polymeric carrier branched polyethyleneimine (BPEI) is investigated. The substitution of primary amine groups in the BPEI chains with lactose residues leads to larger polyplexes, presumably due to the higher amount of polymer required to complete DNA condensation. Nevertheless, the sugar functionalization substantially reduces the cytotoxicity of the assemblies. The nanocomplexes are taken up by the cells to a greater extent, whereas the levels of gene expression are maintained compared to those obtained using BPEI, which is known for its excellent transfection efficiency. Accordingly, the preparation of lower-cytotoxicity polyplexes while maintaining gene expression, which is highly relevant to the field, is demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiple β-Ketothiolases Mediate Poly(β-Hydroxyalkanoate) Copolymer Synthesis in Ralstonia eutropha

PubMed Central

Slater, Steven; Houmiel, Kathryn L.; Tran, Minhtien; Mitsky, Timothy A.; Taylor, Nancy B.; Padgette, Stephen R.; Gruys, Kenneth J.

1998-01-01

Polyhydroxyalkanoates (PHAs) are a class of carbon and energy storage polymers produced by numerous bacteria in response to environmental limitation. The type of polymer produced depends on the carbon sources available, the flexibility of the organism’s intermediary metabolism, and the substrate specificity of the PHA biosynthetic enzymes. Ralstonia eutropha produces both the homopolymer poly-β-hydroxybutyrate (PHB) and, when provided with the appropriate substrate, the copolymer poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PHBV). A required step in production of the hydroxyvalerate moiety of PHBV is the condensation of acetyl coenzyme A (acetyl-CoA) and propionyl-CoA to form β-ketovaleryl-CoA. This activity has generally been attributed to the β-ketothiolase encoded by R. eutropha phbA. However, we have determined that PhbA does not significantly contribute to catalyzing this condensation reaction. Here we report the cloning and genetic analysis of bktB, which encodes a β-ketothiolase from R. eutropha that is capable of forming β-ketovaleryl-CoA. Genetic analyses determined that BktB is the primary condensation enzyme leading to production of β-hydroxyvalerate derived from propionyl-CoA. We also report an additional β-ketothiolase, designated BktC, that probably serves as a secondary route toward β-hydroxyvalerate production. PMID:9555876

Semipermeable polymers and method for producing same

DOEpatents

Buschmann, Wayne E [Boulder, CO

2012-04-03

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

Organic/inorganic nanocomposites, methods of making, and uses as a permeable reactive barrier

DOEpatents

Harrup, Mason K [Idaho Falls, ID; Stewart, Frederick F [Idaho Falls, ID

2007-05-15

Nanocomposite materials having a composition including an inorganic constituent, a preformed organic polymer constituent, and a metal ion sequestration constituent are disclosed. The nanocomposites are characterized by being single phase, substantially homogeneous materials wherein the preformed polymer constituent and the inorganic constituent form an interpenetrating network with each other. The inorganic constituent may be an inorganic oxide, such as silicon dioxide, formed by the in situ catalyzed condensation of an inorganic precursor in the presence of the solvated polymer and metal ion sequestration constituent. The polymer constituent may be any hydrophilic polymer capable of forming a type I nanocomposite such as, polyacrylonitrile (PAN), polyethyleneoxide (PEO), polyethylene glycol (PEG), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), and combinations thereof. Nanocomposite materials of the present invention may be used as permeable reactive barriers (PRBs) to remediate contaminated groundwater. Methods for making nanocomposite materials, PRB systems, and methods of treating groundwater are also disclosed.

Ultrahigh molecular weight aromatic siloxane polymers

NASA Technical Reports Server (NTRS)

Ludwick, L. M.

1982-01-01

The condensation of a diol with a silane in toluene yields a silphenylene-siloxane polymer. The reaction of stiochiometric amounts of the diol and silane produced products with molecular weights in the range 2.0 - 6.0 x 10 to the 5th power. The molecular weight of the product was greatly increased by a multistep technique. The methodology for synthesis of high molecular weight polymers using a two step procedure was refined. Polymers with weight average molecular weights in excess of 1.0 x 10 to the 6th power produced by this method. Two more reactive silanes, bis(pyrrolidinyl)dimethylsilane and bis(gamma butyrolactam)dimethylsilane, are compared with the dimethyleminodimethylsilane in ability to advance the molecular weight of the prepolymer. The polymers produced are characterized by intrinsic viscosity in tetrahydrofuran. Weight and number average molecular weights and polydispersity are determined by gel permeation chromatography.

Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

NASA Astrophysics Data System (ADS)

Silva Mojica, Ernesto

Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was based on the spectroscopic investigation of the interactions of CO 2 with amine molecules under simulated CO2 capture conditions. Industrial CO2 capture processes involve fluidization and require degradation-resistant sorbents in the form of pellets. Agglomeration of silica-based CO2 capture sorbents involved the formulation of a polymer binder solution and the design of a scalable pelletization process. The characterization of these pellets revealed the formation of a CO 2-permeable polymer-silica network, which is resistant to attrition, and exhibits similar CO2 capture and degradation performance as the non-pelletized sorbents. The performance of these sorbents and pellets was tested in lab-scale and bench-scale adsorption units, using in-house fabricated fixed-bed and fluidized-bed reactors. A compartmental modeling technique was used to simulate the CO2 adsorption process and to elucidate the kinetic and thermodynamic parameters that impact the commercial viability of emerging CO2 capture technologies. The fundamental concepts and experimental techniques developed for the preparation of CO2 capture sorbents served as a basis for fabricating amine-functionalized polymer-silica hybrids for applications in catalysis of organic reactions. (i) Basic catalysts for carbon-carbon addition reactions were prepared by immobilization of amine molecules on silica supports. The activity of these catalysts and the mechanisms of base-catalyzed organic condensation reactions were investigated by an in-situ FTIR micro-scale reactor. (ii) Particle-loaded PVA composite membranes were selected for immobilization of glucose oxidase (GOx). GOx was immobilized by adsorption at pH values between 3.5 and 7.1. The results showed that adsorption was primarily achieved via hydrophobic interactions, and that PVA membranes loaded with amine-functionalized particles could help retain the activity of immobilized GOx by providing a proper hydrophilic/hydrophobic balance to the immobilized enzymes micro-environment.

Comparison of Document Data Bases

ERIC Educational Resources Information Center

Schipma, Peter B.; And Others

This paper presents a detailed analysis of the content and format of seven machine-readable bibliographic data bases: Chemical Abstracts Service Condensates, Chemical and Biological Activities, and Polymer Science and Technology, Biosciences Information Service's BA Previews including Biological Abstracts and BioResearch Index, Institute for…

Low-temperature Condensation of Carbon

NASA Astrophysics Data System (ADS)

Krasnokutski, S. A.; Goulart, M.; Gordon, E. B.; Ritsch, A.; Jäger, C.; Rastogi, M.; Salvenmoser, W.; Henning, Th.; Scheier, P.

2017-10-01

Two different types of experiments were performed. In the first experiment, we studied the low-temperature condensation of vaporized graphite inside bulk liquid helium, while in the second experiment, we studied the condensation of single carbon atoms together with H2, H2O, and CO molecules inside helium nanodroplets. The condensation of vaporized graphite leads to the formation of partially graphitized carbon, which indicates high temperatures, supposedly higher than 1000°C, during condensation. Possible underlying processes responsible for the instant rise in temperature during condensation are discussed. This suggests that such processes cause the presence of partially graphitized carbon dust formed by low-temperature condensation in the diffuse interstellar medium. Alternatively, in the denser regions of the ISM, the condensation of carbon atoms together with the most abundant interstellar molecules (H2, H2O, and CO), leads to the formation of complex organic molecules (COMs) and finally organic polymers. Water molecules were found not to be involved directly in the reaction network leading to the formation of COMs. It was proposed that COMs are formed via the addition of carbon atoms to H2 and CO molecules ({{C}}+{{{H}}}2\\to {HCH},{HCH}+{CO}\\to {{OCCH}}2). Due to the involvement of molecular hydrogen, the formation of COMs by carbon addition reactions should be more efficient at high extinctions compared with the previously proposed reaction scheme with atomic hydrogen.

Molecular Design for Preparation of Hexagonal-Ordered Porous Films Based on Side-chain Type Liquid-Crystalline Star Polymer.

PubMed

Naka, Yumiko; Takayama, Hiromu; Koyama, Teruhisa; Le, Khoa V; Sasaki, Takeo

2018-05-02

Fabrication of regularly porous films by the breath-figure method has attracted much attention. The simple, low-cost technique uses the condensation of water droplets to produce these structures, but the phenomenon itself is complex, requiring control over many interacting parameters that change throughout the process. Developing a unified understanding for the molecular design of polymers to prepare ordered porous films is challenging, but required for further advancements. In this article, the effects of the chemical structure of polymers in the breath-figure technique were systematically explored using side-chain type liquid-crystalline (LC) star polymers. The formation of porous films was affected by the structure of the polymers. Although the entire film surface of poly(11-[4-(4-cyanobiphenyl)oxy]undecyl methacrylate) (P11CB) had a hexagonal ordered porous structure over a certain Mn value, regularly arranged holes did not easily form in poly(methyl methacrylate) (PMMA), even though the main chain of PMMA is similar to that of P11CB. Comparing P11CB and poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11B) (P11CB without cyano groups) showed that the local polar groups in hydrophobic polymers promoted the formation of ordered porous films. No holes formed in poly(4-cyanobiphenyl methacrylate) (P0CB) (P11CB without alkyl spacers) films due to its hydrophilicity. The introduction of alkyl chains in P0CB allowed the preparation of honeycomb-structured films by increasing the internal tension. However, alkyl chains in the side chain alone did not result in a porous structure, as in the case of poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11). Aromatic rings are also required to increase the Tg and improve film formability. In the present study, suitable molecular designs of polymers were found, specifically hydrophobic polymers with local polar groups, to form a regularly porous structure. Development of clear guidelines for the molecular design of polymers is the subject of our current research, which will enable the fabrication of porous films using various functional polymers.

Role of DNA-DNA Interactions on the Structure and Thermodynamics of Bacteriophages Lambda and P4

PubMed Central

Petrov, Anton S.; Harvey, Stephen C.

2010-01-01

Electrostatic interactions play an important role in both packaging of DNA inside bacteriophages and its release into bacterial cells. While at physiological conditions DNA strands repel each other, the presence of polyvalent cations such as spermine and spermidine in solutions leads to the formation of DNA condensates. In this study, we discuss packaging of DNA into bacteriophages P4 and Lambda under repulsive and attractive conditions using a coarse-grained model of DNA and capsids. Packaging under repulsive conditions leads to the appearance of the coaxial spooling conformations; DNA occupies all available space inside the capsid. Under the attractive potential both packed systems reveal toroidal conformations, leaving the central part of the capsids empty. We also present a detailed thermodynamic analysis of packaging and show that the forces required to pack the genomes in the presence of polyamines are significantly lower than those observed under repulsive conditions. The analysis reveals that in both the repulsive and attractive regimes the entropic penalty of DNA confinement has a significant non-negligible contribution into the total energy of packaging. Additionally we report the results of simulations of DNA condensation inside partially packed Lambda. We found that at low densities DNA behaves as free unconfined polymer and condenses into the toroidal structures; at higher densities rearrangement of the genome into toroids becomes hindered, and condensation results in the formation of non-equilibrium structures. In all cases packaging in a specific conformation occurs as a result of interplay between bending stresses experienced by the confined polymer and interactions between the strands. PMID:21074621

Semiconductor grade, solar silicon purification project

NASA Technical Reports Server (NTRS)

Ingle, W. M.; Chaney, R.; Thompson, S.

1977-01-01

The potential for a three step SiF2 polymer transport purification process was examined. The process involves reacting low cost mg silicon with SiF4 to yield SiF2 gas which is condensed to form polymeric (SiF2)x. The polymer is then heated above 400 C to yield Si, SiF4 and higher Si sub n F sub 2n+2 homologues. This report presents and discusses continuing progress on (1) observations on (SiF2)x polymer formation and depolymerization on the small coil, (2) mass balance studies, (3) partial pressures of SiF2 and SiF4, (4) AlF3 mass spectral studies, and (5) material analysis studies.

Synthesis and characterizations of novel polymer electrolytes

NASA Astrophysics Data System (ADS)

Chanthad, Chalathorn

Polymer electrolytes are an important component of many electrochemical devices. The ability to control the structures, properties, and functions of polymer electrolytes remains a key subject for the development of next generation functional polymers. Taking advantage of synthetic strategies is a promising approach to achieve the desired chemical structures, morphologies, thermal, mechanical, and electrochemical properties. Therefore, the major goal of this thesis is to develop synthetic methods for of novel proton exchange membranes and ion conductive membranes. In Chapter 2, new classes of fluorinated polymer- polysilsesquioxane nanocomposites have been designed and synthesized. The synthetic method employed includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in-situ sol-gel condensation of the prepared triethoxylsilane-terminated fluorinated polymers with alkoxide precursors. The properties of the composite membranes have been studied as a function of the content and structure of the fillers. The proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases ion-exchange capacity and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane based nanocomposites. In Chapter 3, the synthesis of a new class of ionic liquid-containing triblock copolymers with fluoropolymer mid-block and imidazolium methacrylate end-blocks is described for the first time. The synthetic strategy involves the preparation of the telechelic fluoropolymers using a functional benzoyl peroxide initiator as the macro-chain transfer agent for subsequent RAFT polymerization of the imidazolium methacrylate monomer. As revealed in DSC, SAXS and dielectric relaxation spectroscopy (DRS) measurements, there was no microphase separation in the triblock copolymers, likely due to solubility of ionic liquid moieties in the fluoropolymer matrix. The anionic counterion has direct impact on the thermal properties, ionic conductivity and segmental dynamics of the polymers. The temperature dependence of the ionic conductivity is well described by the Vogel-Tamman-Fulcher model, suggesting that ion motion is closely coupled to segmental motion. In Chapter 4 and 5, new solid electrolytes for lithium cations have been synthesized by catalyzed hydrosilylation reaction involving hydrogen atoms of polysiloxane and polyhedral oligomeric silsesquioxane (POSS) and double bonds of vinyl tris17-bromo-3,6,9,12,15- pentaoxaheptadecan-1-ol silane. The obtained structures are based on branched or dendritic with ionic liquid-ethylene oxide oligomer. High room temperature ionic conductivities have been obtained in the range of 10-4-10-5 can be regarded as solid electrolytes. This is attributed to the high concentration of ions from ionic liquid moieties in the tripodand molecule, high segmental mobility, and high ion dissociation from ethylene oxide spacers. The influence of anion structures and lithium salts and concentration has been investigated.

Computational Model for DNA Organization Mediated by Protein Interaction in Prokaryotes

NASA Astrophysics Data System (ADS)

Garimella, Karthik; Kharel, Savan

2016-03-01

In Escherichia Coli, there are several mechanisms that drive chromosomal organization. We know through experiments that the E. Coli chromosome is condensed into highly structured regions known as macrodomains (MDs). One of the regions known as the Terminus undergoes DNA-bridging condensation that form loops between distant DNA sites and it is known to be mediated by a Terminus specific protein, which binds to specific markers within the Terminus region. In the absence of Terminus specific protein, however, the Terminus region is known to not condense nearly as much, which will likely impede several biological processes including DNA replication. In order to understand the molecular basis of protein mediation in vivo several models of Terminus specific segregation have been constructed in silico which model DNA as polymer chains.

THE ROLE OF METASTABLE STATES IN POLYMER PHASE TRANSITIONS: Concepts, Principles, and Experimental Observations

NASA Astrophysics Data System (ADS)

Cheng, Stephen Z. D.; Keller, Andrew

1998-08-01

Polymer phases can be described in the same way as phases in other condensed matter using a number density operator and its correlation functions. This description requires the understanding of symmetry operations and order at different atomic and molecular levels. Statistical mechanics provides a link between the microscopic description of the structure and motion and the macroscopic thermodynamic properties. Within the limits of the laws of thermodynamics, polymers exhibit a rich variety of phase transition behaviors. By definition, a first-order phase transition describes a transformation that involves a sudden change of thermodynamic properties at its transition temperature, whereas higher-order phase transitions are classified as critical phenomena. Of special interest is the role of metastability in phase and phase transition behaviors. Although a metastable state possesses a local free energy minimum, it is not at the global equilibrium. Furthermore, metastable states can also be associated with phase sizes. Metastable behavior is also observed in phase transformations that are impeded by kinetic limitations along the pathway to thermodynamic equilibrium. This is illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification, and gel formation, as well as combinations of transformation processes. In these cases, the metastable state often becomes the dominant state for the entire system and is observed over a range of time and size scales. This review describes the general principles of metastability in polymer phases and phase transitions and provides illustrations from current experimental works in selected areas.

Hydrophobic modification of low molecular weight polyethylenimine for improved gene transfection.

PubMed

Teo, Pei Yun; Yang, Chuan; Hedrick, James L; Engler, Amanda C; Coady, Daniel J; Ghaem-Maghami, Sadaf; George, Andrew J T; Yang, Yi Yan

2013-10-01

Hydrophobic modification of low molecular weight (LMW) polyethylenimine (PEI) is known to increase gene transfection efficiency of LMW PEI. However, few studies have explored how the conjugated hydrophobic groups influence the properties of the modified LMW PEI mainly due to difficulties in obtaining well defined final product compositions and limitations in current chemical synthesis routes. The aim of this study was to modify LMW PEI (Mn 1.8 kDa, PEI-1.8) judiciously with different hydrophobic functional groups and to investigate how hydrophobicity, molecular structure and inclusion of hydrogen bonding properties in the conjugated side groups as well as the conjugation degree (number of primary amine groups of PEI-1.8 modified with hydrophobic groups) influence PEI-1.8 gene transfection efficiency. The modified polymers were characterized for DNA binding ability, particle size, zeta potential, in vitro gene transfection efficiency and cytotoxicity in SKOV-3 human ovarian cancer and HepG2 human liver carcinoma cell lines. The study shows that modified PEI-1.8 polymers are able to condense plasmid DNA into cationic nanoparticles, of sizes ~100 nm, whereas unmodified polymer/DNA complexes display larger particle sizes of 2 μm. Hydrophobic modification also increases the zeta potential of polymer/DNA complexes. Importantly, modified PEI-1.8 shows enhanced transfection efficiency over the unmodified counterpart. Higher transfection efficiency is obtained when PEI-1.8 is modified with shorter hydrophobic groups (MTC-ethyl) as opposed to longer ones (MTC-octyl and MTC-deodecyl). An aromatic structured functional group (MTC-benzyl) also enhances transfection efficiency more than an alkyl functional group (MTC-octyl). An added hydrogen-bonding urea group in the conjugated functional group (MTC-urea) does not enhance transfection efficiency over one without urea (MTC-benzyl). The study also demonstrates that modification degree greatly influences gene transfection, and ~100% substitution of primary amine groups leads to significantly lower gene transfection efficiency. These findings provide insights to modification of PEI for development of effective and non-cytotoxic non-viral vectors. Copyright © 2013 Elsevier Ltd. All rights reserved.

Differential solvation of intrinsically disordered linkers drives the formation of spatially organized droplets in ternary systems of linear multivalent proteins

NASA Astrophysics Data System (ADS)

Harmon, Tyler S.; Holehouse, Alex S.; Pappu, Rohit V.

2018-04-01

Intracellular biomolecular condensates are membraneless organelles that encompass large numbers of multivalent protein and nucleic acid molecules. The bodies assemble via a combination of liquid–liquid phase separation and gelation. A majority of condensates included multiple components and show multilayered organization as opposed to being well-mixed unitary liquids. Here, we put forward a simple thermodynamic framework to describe the emergence of spatially organized droplets in multicomponent systems comprising of linear multivalent polymers also known as associative polymers. These polymers, which mimic proteins and/or RNA have the architecture of domains or motifs known as stickers that are interspersed by flexible spacers known as linkers. Using a minimalist numerical model for a four-component system, we have identified features of linear multivalent molecules that are necessary and sufficient for generating spatially organized droplets. We show that differences in sequence-specific effective solvation volumes of disordered linkers between interaction domains enable the formation of spatially organized droplets. Molecules with linkers that are preferentially solvated are driven to the interface with the bulk solvent, whereas molecules that have linkers with negligible effective solvation volumes form cores in the core–shell architectures that emerge in the minimalist four-component systems. Our modeling has relevance for understanding the physical determinants of spatially organized membraneless organelles.

A Biodegradable Thermoset Polymer Made by Esterification of Citric Acid and Glycerol

PubMed Central

Halpern, Jeffrey M.; Urbanski, Richard; Weinstock, Allison K.; Iwig, David F.; Mathers, Robert T.; von Recum, Horst

2014-01-01

A new biomaterial, a degradable thermoset polymer, was made from simple, economical, biocompatable monomers without the need for a catalyst. Glycerol and citric acid, non-toxic and renewable reagents, were crosslinked by a melt polymerization reaction at temperatures from 90-150°C. Consistent with a condensation reaction, water was determined to be the primary byproduct. The amount of crosslinking was controlled by the reaction conditions, including temperature, reaction time, and ratio between glycerol and citric acid. Also, the amount of crosslinking was inversely proportional to the rate of degradation. As a proof-of-principle for drug delivery applications, gentamicin, an antibiotic, was incorporated into the polymer with preliminary evaluations of antimicrobial activity. The polymers incorporating gentamicin had significantly better bacteria clearing of Staphylococcus aureus compared to non-gentamicin gels for up to nine days. PMID:23737239

Swollen poly(dimethylsiloxane) (PDMS) as a template for inorganic morphologies.

PubMed

Brennan, Daniel P; Dobley, Arthur; Sideris, Paul J; Oliver, Scott R J

2005-12-06

We report a series of silica, titania, and zirconia microstructures synthesized within swollen poly(dimethylsiloxane) (PDMS). Voids created by solvent-swelling the polymer are used to template the product. The inorganic morphologies range from spheres to networks, depending upon the nature of the polymer, its degree of swelling, and the synthetic conditions. Organic solvents as well as pure metal alkoxide liquids have been used to swell the polymer. Once the alkoxide precursor is inside the swollen polymer, water is introduced to bring about hydrolysis and condensation polymerization. The product is a textured metal oxide within a PDMS matrix. Scanning electron microscopy (SEM), optical microscopy, nuclear magnetic resonance (NMR), and powder X-ray diffraction (PXRD) were used to characterize the products. Microstructures formed in this manner have potential use as an inexpensive route to catalysts, fillers, capsules, or membranes for separations.

Fabrication of Polyimide Membrane Incorporated with Functional Graphene Oxide for CO2 Separation: The Effects of GO Surface Modification on Membrane Performance.

PubMed

Wang, Ting; Cheng, Cheng; Wu, Li-Guang; Shen, Jiang-Nan; Van der Bruggen, Bart; Chen, Qian; Chen, Di; Dong, Chun-Ying

2017-06-06

Two kinds of isocyanate were used to modify graphene oxide (GO) samples. Then, polyimide (PI) hybrid membranes containing GO and modified GO were prepared by in situ polymerization. The permeation of CO 2 and N 2 was studied using these novel membranes. The morphology experiments showed that the isocyanate groups were successfully grafted on the surface of GO by replacement of the oxygen-containing functional groups. After modification, the surface polarity of the GO increased, and more defect structures were introduced into the GO surface. This resulted in a good distribution of more modified GO samples in the PI polymer matrix. Thus, the PI hybrid membranes incorporated by modified GO samples showed a high gas permeability and ideal selectivity of membranes. In addition, enhancement of the selectivity due to the solubility of CO 2 played a major role in the increase in the separation performance of the hybrid membranes for CO 2 , although the diffusion coefficients for CO 2 also increased. Both the higher condensability and the strong affinity between CO 2 molecules and GO in the polymer matrix caused an enhancement of the solubility selectivity higher than the diffusion selectivity after GO surface modification.

Advanced Polymers Containing the Phenyltrifluoroethylidene Connecting Group

NASA Technical Reports Server (NTRS)

Alstron, William B.; Sivko, Gloria S.

2006-01-01

A new, lower cost fluorinated dianhydride based on the phenyltrifluoroethylidene (3F) connecting linkage was invented by the principal author in the early 1980's. New 3F condensation and addition cured polyimides were synthesized with the newly discovered 3F dianhydride and the previously known 3F diamine. As controls, polyimides based on the somewhat analogous higher cost hexafluoroisopropylidene (6F) linkage were also prepared. The short term thermal oxidative stability (TOS), determined by thermal gravimetric analysis (TGA), and the glass transition temperatures (Tg) of 3F dianhydride polyimides were found to be similar to 6F dianhydride polyimides, but the Tg was slightly higher for 3F diamine polyimides than 6F diamine polyimides. Unfortunately, in real time testing, long term TOS of 3F polymers was clearly inferior to 6F polymers. This was due to a 3 to 5 fold greater rate of loss of trifluoromethyl group from 3F versus 6F linkages. However, at shorter times or lower temperatures, 3F TOS was almost comparable to 6F TOS. The wide scope of the 3F technology was also demonstrated to have distinct unique advantages over 6F technology through the use of the 3F pendant phenyl ring as a synthetic site to introduce other functional groups. These groups have been used for the control or modification of polymer properties; an advantage lacking within 6F technology. The synthetic ease by which 3F can be introduced into various types of monomers has lead to the explosion of advanced 3F polyimides and other high performance advanced 3F polymers in the prior decade of 3F polymer literature as cited herein; covering polyimides, substituted polyimides, at least ten types of nonpolyimide 3F polymer modifications, and also the government's nine 3F U.S. patents and corporations' nine 3F U.S. patents.

Chemistry Notes.

ERIC Educational Resources Information Center

School Science Review, 1984

1984-01-01

Describes: (1) a microcomputer demonstration of autocatalysis; (2) a safe alternative to ethanol and methanol; (3) a simple condenser for test-tube reactions; (4) a new procedure for studying the magnetic properties of transition metal compounds; (5) plasticization of the polymer PVC; and (6) some thoughts on polybasic acids and their salts. (JN)

Mechanics of Sister Chromatids studied with a Polymer Model