Radiation-induced polymerization of glass-forming systems. V. Initial polymerization rate in binary glass-forming systems

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

Kaetsu, Isao; Okubo, Hiroshi; Ito, Akihiko

1973-06-01

The radiation-induced polymerization of binary systems consisting of glass-forming monomer and glass-forming solvent in supercooled phase was studied. The initial polymerization rates were markedly affected by T/sub g/ (glass transition temperature) and T/sub v/ of the system (30-50 deg C higher than T/sub g/), which are functions of the composition. The composition and temperature dependence of initial polymerization rate in binary glass-forming systems were much affected by homogeneity of the polymerization system and the T of the glass- forming solvent. The composition and temperature dependences in the glycidyl methacrylate --triacetin system as a typical homogeneous polymerization system were studied inmore » detail, and the polymerizations of hydroxyethyl methacrylate triacetln and hydroxyethyl methacrylate --isoamyl acetate systems were studied for the heterogeneous polymerization systems; the former illustrates the combination of lower T/sub g/ monomer and higher T/sub g/ solvent and the latter typifies a system consisting of higher T/sub g/ monomer and lower T/sub g/ solvent. All experimental results for the composition and temperature dependence of initial polymerization rate in binary glass-forming systems could be explained by considering the product of the effect of the physical effect relating to T/sub v/ and T/sub g/ of the system and the effect of composition in normal solution polymerization at higher temperature, which was also the product of a dilution effect and a chemical or physical acceleration effect. (auth)« less

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

Zheng, Haiyan; Wang, Lijuan; Li, Kuo

Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6- are identified with gas chromatography-mass spectrometry and severalmore » other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 107 fold enhancement of the electrical conductivity. The polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less

Encapsulated nano-heat-sinks for thermal management of heterogeneous chemical reactions.

PubMed

Zhang, Minghui; Hong, Yan; Ding, Shujiang; Hu, Jianjun; Fan, Yunxiao; Voevodin, Andrey A; Su, Ming

2010-12-01

This paper describes a new way to control temperatures of heterogeneous exothermic reactions such as heterogeneous catalytic reaction and polymerization by using encapsulated nanoparticles of phase change materials as thermally functional additives. Silica-encapsulated indium nanoparticles and silica encapsulated paraffin nanoparticles are used to absorb heat released in catalytic reaction and to mitigate gel effect of polymerization, respectively. The local hot spots that are induced by non-homogenous catalyst packing, reactant concentration fluctuation, and abrupt change of polymerization rate lead to solid to liquid phase change of nanoparticle cores so as to avoid thermal runaway by converting energies from exothermic reactions to latent heat of fusion. By quenching local hot spots at initial stage, reaction rates do not rise significantly because the thermal energy produced in reaction is isothermally removed. Nanoparticles of phase change materials will open a new dimension for thermal management of exothermic reactions to quench local hot spots, prevent thermal runaway of reaction, and change product distribution.

Pressure-induced polymerization of acetylene: Structure-directed stereoselectivity and a possible route to graphane

DOE PAGES

Sun, Jiangman; Dong, Xiao; Wang, Yajie; ...

2017-05-02

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Moreover, following this route produces a pure cis-isomer and more surprisingly, predictsmore » that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure.« less

Polymerization of anionic wormlike micelles.

PubMed

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles.

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

Zheng, Haiyan; Wang, Lijuan; Li, Kuo

Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC 2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC 2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6– are identified with gas chromatography-mass spectrometrymore » and several other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 10 7 fold enhancement of the electrical conductivity. As a result, the polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less

Phase diagram and transformations of iron pentacarbonyl to nm layered hematite and carbon-oxygen polymer under pressure

DOE PAGES

Ryu, Young Jay; Kim, Minseob; Yoo, Choong -Shik

2015-10-12

In this study, we present the phase diagram of Fe(CO) 5, consisting of three molecular polymorphs (phase I, II and III) and an extended polymeric phase that can be recovered at ambient condition. The phase diagram indicates a limited stability of Fe(CO) 5 within a pressure-temperature dome formed below the liquid- phase II- polymer triple point at 4.2 GPa and 580 K. The limited stability, in turn, signifies the temperature-induced weakening of Fe-CO back bonds, which eventually leads to the dissociation of Fe-CO at the onset of the polymerization of CO. The recovered polymer is a composite of novel nm-lamellarmore » layers of crystalline hematite Fe 2O 3 and amorphous carbon-oxygen polymers. These results, therefore, demonstrate the synthesis of carbon-oxygen polymer by compressing Fe(CO) 5, which advocates a novel synthetic route to develop atomistic composite materials by compressing organometallic compounds.« less

Interference lithography for optical devices and coatings

NASA Astrophysics Data System (ADS)

Juhl, Abigail Therese

Interference lithography can create large-area, defect-free nanostructures with unique optical properties. In this thesis, interference lithography will be utilized to create photonic crystals for functional devices or coatings. For instance, typical lithographic processing techniques were used to create 1, 2 and 3 dimensional photonic crystals in SU8 photoresist. These structures were in-filled with birefringent liquid crystal to make active devices, and the orientation of the liquid crystal directors within the SU8 matrix was studied. Most of this thesis will be focused on utilizing polymerization induced phase separation as a single-step method for fabrication by interference lithography. For example, layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The holographic exposure of the particles within the monomer resin offers a single-step method to anisotropically structure the nanoconstituents within a composite. A one-step holographic exposure was also used to fabricate self-healing coatings that use water from the environment to catalyze polymerization. Polymerization induced phase separation was used to sequester an isocyanate monomer within an acrylate matrix. Due to the periodic modulation of the index of refraction between the monomer and polymer, the coating can reflect a desired wavelength, allowing for tunable coloration. When the coating is scratched, polymerization of the liquid isocyanate is catalyzed by moisture in air; if the indices of the two polymers are matched, the coatings turn transparent after healing. Interference lithography offers a method of creating multifunctional self-healing coatings that readout when damage has occurred.

An insight into polymerization-induced self-assembly by dissipative particle dynamics simulation.

PubMed

Huang, Feng; Lv, Yisheng; Wang, Liquan; Xu, Pengxiang; Lin, Jiaping; Lin, Shaoliang

2016-08-14

Polymerization-induced self-assembly is a one-pot route to produce concentrated dispersions of block copolymer nano-objects. Herein, dissipative particle dynamics simulations with a reaction model were employed to investigate the behaviors of polymerization-induced self-assembly. The polymerization kinetics in the polymerization-induced self-assembly were analyzed by comparing with solution polymerization. It was found that the polymerization rate enhances in the initial stage and decreases in the later stage. In addition, the effects of polymerization rate, length of macromolecular initiators, and concentration on the aggregate morphologies and formation pathway were studied. The polymerization rate and the length of the macromolecular initiators are found to have a marked influence on the pathway of the aggregate formations and the final structures. Morphology diagrams were mapped correspondingly. A comparison between simulation results and experimental findings is also made and an agreement is shown. This work can enrich our knowledge about polymerization-induced self-assembly.

Nonperturbative Renormalization Group Approach to Polymerized Membranes

NASA Astrophysics Data System (ADS)

Essafi, Karim; Kownacki, Jean-Philippe; Mouhanna, Dominique

2014-03-01

Membranes or membrane-like materials play an important role in many fields ranging from biology to physics. These systems form a very rich domain in statistical physics. The interplay between geometry and thermal fluctuations lead to exciting phases such flat, tubular and disordered flat phases. Roughly speaking, membranes can be divided into two group: fluid membranes in which the molecules are free to diffuse and thus no shear modulus. On the other hand, in polymerized membranes the connectivity is fixed which leads to elastic forces. This difference between fluid and polymerized membranes leads to a difference in their critical behaviour. For instance, fluid membranes are always crumpled, whereas polymerized membranes exhibit a phase transition between a crumpled phase and a flat phase. In this talk, I will focus only on polymerized phantom, i.e. non-self-avoiding, membranes. The critical behaviour of both isotropic and anisotropic polymerized membranes are studied using a nonperturbative renormalization group approach (NPRG). This allows for the investigation of the phase transitions and the low temperature flat phase in any internal dimension D and embedding d. Interestingly, graphene behaves just as a polymerized membrane in its flat phase.

Pressure-Induced Polymerization of Acetylene: Structure-Directed Stereoselectivity and a Possible Route to Graphane.

PubMed

Sun, Jiangman; Dong, Xiao; Wang, Yajie; Li, Kuo; Zheng, Haiyan; Wang, Lijuan; Cody, George D; Tulk, Christopher A; Molaison, Jamie J; Lin, Xiaohuan; Meng, Yufei; Jin, Changqing; Mao, Ho-Kwang

2017-06-01

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Following this route produces a pure cis-isomer and more surprisingly, predicts that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High pressure study of acetophenone azine

NASA Astrophysics Data System (ADS)

Tang, X. D.; Ding, Z. J.; Zhang, Z. M.

2009-02-01

High pressure Raman spectra of acetophenone azine (APA) have been measured up to 17.7 GPa with a diamond anvil cell. Two crystalline-to-crystalline phase transformations are found at pressures about 3.6 and 5.8 GPa. A disappearance of external modes and the C-H vibration at pressures higher than 8.7 GPa suggests that the sample undergoes a phase transition to amorphous or orientationally disordered (plastic) state, and the amorphization was completed at about 12.1 GPa. The disordered state is unstable and, then, a polymerization transformation reaction occurs with a further pressure increase. After the pressure has been released, the polymerization state can remain at the ambient condition, indicating that the virgin crystalline state is not recovered. The results show that the phenomenon underlying the pressure induced phase transition of APA may involve profound changes in the coordination environments of the symmetric aromatic azine.

Selective Photophysical Modification on Light-Emitting Polymer Films for Micro- and Nano-Patterning

PubMed Central

Zhang, Xinping; Liu, Feifei; Li, Hongwei

2016-01-01

Laser-induced cross-linking in polymeric semiconductors was utilized to achieve micro- and nano-structuring in thin films. Single- and two-photon cross-linking processes led to the reduction in both the refractive index and thickness of the polymer films. The resultant photonic structures combine the features of both relief- and phase-gratings. Selective cross-linking in polymer blend films based on different optical response of different molecular phases enabled “solidification” of the phase-separation scheme, providing a stable template for further photonic structuring. Dielectric and metallic structures are demonstrated for the fabrication methods using cross-linking in polymer films. Selective cross-linking enables direct patterning into polymer films without introducing additional fabrication procedures or additional materials. The diffraction processes of the emission of the patterned polymeric semiconductors may provide enhanced output coupling for light-emitting diodes or distributed feedback for lasers. PMID:28773248

Synthesis of long Prebiotic Oligomers on Mineral Surfaces

NASA Technical Reports Server (NTRS)

Ferris, James P.; Hill, Aubrey R., Jr.; Liu, Rihe; Orgel, Leslie E.

1996-01-01

Most theories of the origin of biological organization assume that polymers with lengths in the range of 30-60 monomers are needed to make a genetic system viable. But it has not proved possible to synthesize plausibly prebiotic polymers this long by condensation in aqueous solution, because hydrolysis competes with polymerization. The potential of mineral surfaces to facilitate prebiotic polymerization was pointed out long ago. Here we describe a system that models prebiotic polymerization by the oligomerization of activated monomers -both nucleotides and amino acids. We find that whereas the reactions in solution produce only short oligomers (the longest typically being a 10-mer), the presence of mineral surfaces (montmorillonite for nucleotides, illite and hydroxylapatite for amino adds) induces the formation of oligomers up to 55 monomers long. These are formed by successive "feedings" with the monomers; polymerization takes place on the mineral surfaces in a manner akin to solid-phase synthesis of biopolymers.

Progressive Transverse Microtubule Array Organization in Hormone-Induced Arabidopsis Hypocotyl Cells[W

PubMed Central

Vineyard, Laura; Elliott, Andrew; Dhingra, Sonia; Lucas, Jessica R.; Shaw, Sidney L.

2013-01-01

The acentriolar cortical microtubule arrays in dark-grown hypocotyl cells organize into a transverse coaligned pattern that is critical for axial plant growth. In light-grown Arabidopsis thaliana seedlings, the cortical array on the outer (periclinal) cell face creates a variety of array patterns with a significant bias (>3:1) for microtubules polymerizing edge-ward and into the side (anticlinal) faces of the cell. To study the mechanisms required for creating the transverse coalignment, we developed a dual-hormone protocol that synchronously induces ∼80% of the light-grown hypocotyl cells to form transverse arrays over a 2-h period. Repatterning occurred in two phases, beginning with an initial 30 to 40% decrease in polymerizing plus ends prior to visible changes in the array pattern. Transverse organization initiated at the cell’s midzone by 45 min after induction and progressed bidirectionally toward the apical and basal ends of the cell. Reorganization corrected the edge-ward bias in polymerization and proceeded without transiting through an obligate intermediate pattern. Quantitative comparisons of uninduced and induced microtubule arrays showed a limited deconstruction of the initial periclinal array followed by a progressive array reorganization to transverse coordinated between the anticlinal and periclinal cell faces. PMID:23444330

Photo-responsive polymeric micelles.

PubMed

Huang, Yu; Dong, Ruijiao; Zhu, Xinyuan; Yan, Deyue

2014-09-07

Photo-responsive polymeric micelles have received increasing attention in both academic and industrial fields due to their efficient photo-sensitive nature and unique nanostructure. In view of the photo-reaction mechanism, photo-responsive polymeric micelles can be divided into five major types: (1) photoisomerization polymeric micelles, (2) photo-induced rearrangement polymeric micelles, (3) photocleavage polymeric micelles, (4) photo-induced crosslinkable polymeric micelles, and (5) photo-induced energy conversion polymeric micelles. This review highlights the recent advances of photo-responsive polymeric micelles, including the design, synthesis and applications in various biomedical fields. Especially, the influence of different photo-reaction mechanisms on the morphology, structure and properties of the polymeric micelles is emphasized. Finally, the possible future directions and perspectives in this emerging area are briefly discussed.

High-pressure synthesis, amorphization, and decomposition of silane.

PubMed

Hanfland, Michael; Proctor, John E; Guillaume, Christophe L; Degtyareva, Olga; Gregoryanz, Eugene

2011-03-04

By compressing elemental silicon and hydrogen in a diamond anvil cell, we have synthesized polymeric silicon tetrahydride (SiH(4)) at 124 GPa and 300 K. In situ synchrotron x-ray diffraction reveals that the compound forms the insulating I4(1)/a structure previously proposed from ab initio calculations for the high-pressure phase of silane. From a series of high-pressure experiments at room and low temperature on silane itself, we find that its tetrahedral molecules break up, while silane undergoes pressure-induced amorphization at pressures above 60 GPa, recrystallizing at 90 GPa into the polymeric crystal structures.

Guided in Situ Polymerization of MEH-PPV in Mesoporous Titania Photoanodes.

PubMed

Minar, Norma K; Docampo, Pablo; Fattakhova-Rohlfing, Dina; Bein, Thomas

2015-05-20

Incorporation of conjugated polymers into porous metal oxide networks is a challenging task, which is being pursued via many different approaches. We have developed the guided in situ polymerization of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) in porous titania films by means of surface functionalization. The controlled polymerization via the Gilch route was induced by an alkoxide base and by increasing the temperature. The selected and specially designed surface-functionalizing linker molecules mimic the monomer or its activated form, respectively. In this way, we drastically enhanced the amount of MEH-PPV incorporated into the porous titania phase compared to nonfunctionalized samples by a factor of 6. Additionally, photovoltaic measurements were performed. The devices show shunting or series resistance limitations, depending on the surface functionalization prior to in situ polymerization of MEH-PPV. We suggest that the reason for this behavior can be found in the orientation of the grown polymer chains with respect to the titania surface. Therefore, the geometry of the anchoring via the linker molecules is relevant for exploiting the full electronic potential of the conjugated polymer in the resulting hybrid composite. This observation will help to design future synthesis methods for new hybrid materials from conjugated polymers and n-type semiconductors to take full advantage of favorable electronic interactions between the two phases.

Photopolymerization of Dienoyl Lipids Creates Planar Supported Poly(lipid) Membranes with Retained Fluidity.

PubMed

Orosz, Kristina S; Jones, Ian W; Keogh, John P; Smith, Christopher M; Griffin, Kaitlyn R; Xu, Juhua; Comi, Troy J; Hall, H K; Saavedra, S Scott

2016-02-16

Polymerization of substrate-supported bilayers composed of dienoylphosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability; however, the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl-phosphatidylcholine (mono-SorbPC), bis-dienoyl-phosphatidylcholine (bis-DenPC), and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity; however, measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate interleaflet bonding. The D values measured after polymerization were 0.1-0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.

Photopolymerization of dienoyl lipids creates planar supported poly(lipid) membranes with retained fluidity

PubMed Central

Orosz, Kristina S.; Jones, Ian W.; Keogh, John P.; Smith, Christopher M.; Griffin, Kaitlyn R.; Xu, Juhua; Comi, Troy J.; Hall, H. K.

2016-01-01

Polymerization of substrate-supported bilayers composed of dienoyl phosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability, however the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl phosphatidylcholine (mono-SorbPC), bis-dienoyl phosphatidylcholine (bis-DenPC) and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity, however measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate inter-leaflet bonding. The D values measured after polymerization were 0.1 to 0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases, and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed. PMID:26794208

In situ X-ray polymerization: from swollen lamellae to polymer-surfactant complexes.

PubMed

Agzenai, Yahya; Lindman, Björn; Alfredsson, Viveka; Topgaard, Daniel; Renamayor, Carmen S; Pacios, Isabel E

2014-01-30

The influence of the monomer diallyldimethylammonium chloride (D) on the lamellar liquid crystal formed by the anionic surfactant aerosol OT (AOT) and water is investigated, determining the lamellar spacings by SAXS and the quadrupolar splittings by deuterium NMR, as a function of the D or AOT concentrations. The cationic monomer D induces a destabilization of the AOT lamellar structure such that, at a critical concentration higher than 5 wt %, macroscopic phase separation takes place. When the monomer, which is dissolved in the AOT lamellae, is polymerized in situ by X-ray initiation, a new collapsed lamellar phase appears, corresponding to the complexation of the surfactant with the resulting polymer. A theoretical model is employed to analyze the variation of the interactions between the AOT bilayers and the stability of the lamellar structure.

Rational synthesis of low-polydispersity block copolymer vesicles in concentrated solution via polymerization-induced self-assembly.

PubMed

Gonzato, Carlo; Semsarilar, Mona; Jones, Elizabeth R; Li, Feng; Krooshof, Gerard J P; Wyman, Paul; Mykhaylyk, Oleksandr O; Tuinier, Remco; Armes, Steven P

2014-08-06

Block copolymer self-assembly is normally conducted via post-polymerization processing at high dilution. In the case of block copolymer vesicles (or "polymersomes"), this approach normally leads to relatively broad size distributions, which is problematic for many potential applications. Herein we report the rational synthesis of low-polydispersity diblock copolymer vesicles in concentrated solution via polymerization-induced self-assembly using reversible addition-fragmentation chain transfer (RAFT) polymerization of benzyl methacrylate. Our strategy utilizes a binary mixture of a relatively long and a relatively short poly(methacrylic acid) stabilizer block, which become preferentially expressed at the outer and inner poly(benzyl methacrylate) membrane surface, respectively. Dynamic light scattering was utilized to construct phase diagrams to identify suitable conditions for the synthesis of relatively small, low-polydispersity vesicles. Small-angle X-ray scattering (SAXS) was used to verify that this binary mixture approach produced vesicles with significantly narrower size distributions compared to conventional vesicles prepared using a single (short) stabilizer block. Calculations performed using self-consistent mean field theory (SCMFT) account for the preferred self-assembled structures of the block copolymer binary mixtures and are in reasonable agreement with experiment. Finally, both SAXS and SCMFT indicate a significant degree of solvent plasticization for the membrane-forming poly(benzyl methacrylate) chains.

Mechanism of Cdc42-induced Actin Polymerization in Neutrophil Extracts

PubMed Central

Zigmond, Sally H.; Joyce, Michael; Yang, Changsong; Brown, Kevin; Huang, Minzhou; Pring, Martin

1998-01-01

Cdc42, activated with GTPγS, induces actin polymerization in supernatants of lysed neutrophils. This polymerization, like that induced by agonists, requires elongation at filament barbed ends. To determine if creation of free barbed ends was sufficient to induce actin polymerization, free barbed ends in the form of spectrin-actin seeds or sheared F-actin filaments were added to cell supernatants. Neither induced polymerization. Furthermore, the presence of spectrin-actin seeds did not increase the rate of Cdc42-induced polymerization, suggesting that the presence of Cdc42 did not facilitate polymerization from spectrin-actin seeds such as might have been the case if Cdc42 inhibited capping or released G-actin from a sequestered pool. Electron microscopy revealed that Cdc42-induced filaments elongated rapidly, achieving a mean length greater than 1 μm in 15 s. The mean length of filaments formed from spectrin-actin seeds was <0.4 μm. Had spectrin-actin seeds elongated at comparable rates before they were capped, they would have induced longer filaments. There was little change in mean length of Cdc42-induced filaments between 15 s and 5 min, suggesting that the increase in F-actin over this time was due to an increase in filament number. These data suggest that Cdc42 induction of actin polymerization requires both creation of free barbed ends and facilitated elongation at these ends. PMID:9722612

Mechanism of Cdc42-induced actin polymerization in neutrophil extracts.

PubMed

Zigmond, S H; Joyce, M; Yang, C; Brown, K; Huang, M; Pring, M

1998-08-24

Cdc42, activated with GTPgammaS, induces actin polymerization in supernatants of lysed neutrophils. This polymerization, like that induced by agonists, requires elongation at filament barbed ends. To determine if creation of free barbed ends was sufficient to induce actin polymerization, free barbed ends in the form of spectrin-actin seeds or sheared F-actin filaments were added to cell supernatants. Neither induced polymerization. Furthermore, the presence of spectrin-actin seeds did not increase the rate of Cdc42-induced polymerization, suggesting that the presence of Cdc42 did not facilitate polymerization from spectrin-actin seeds such as might have been the case if Cdc42 inhibited capping or released G-actin from a sequestered pool. Electron microscopy revealed that Cdc42-induced filaments elongated rapidly, achieving a mean length greater than 1 micron in 15 s. The mean length of filaments formed from spectrin-actin seeds was <0.4 micron. Had spectrin-actin seeds elongated at comparable rates before they were capped, they would have induced longer filaments. There was little change in mean length of Cdc42-induced filaments between 15 s and 5 min, suggesting that the increase in F-actin over this time was due to an increase in filament number. These data suggest that Cdc42 induction of actin polymerization requires both creation of free barbed ends and facilitated elongation at these ends.

The effect of environmental pH on polymeric transfection efficiency.

PubMed

Kang, Han Chang; Samsonova, Olga; Kang, Sun-Woong; Bae, You Han

2012-02-01

Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6-7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1-2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers. Copyright © 2011 Elsevier Ltd. All rights reserved.

Poly(acrylic acid) to induce competitive crystallization of a theophylline/oxalic acid cocrystal and a theophylline polymorph

NASA Astrophysics Data System (ADS)

Jang, Jisun; Kim, Il Won

2016-01-01

Polymeric additives to induce competitive crystallization of pharmaceutical compounds were explored. A cocrystal of theophylline and oxalic acid was used as a model system, and poly(acrylic acid), poly(caprolactone), and poly(ethylene glycol) were the additives. The cocrystal formation was selectively hindered with addition of poly(acrylic acid). First the size of the cocrystals were reduced, and eventually the cocrystallization was inhibited to generate neat theophylline crystals. The theophylline crystals were of a distinctively different crystal structure from known polymorphs, based on powder X-ray diffraction. They were also obtained in nanoscale size, when millimeter-scale crystals formed without poly(acrylic acid). Polymeric additives that could form specific interactions with crystallizing compounds seem to be useful tools for the phase and size control of pharmaceutical crystals.

Pressure-Induced Polymerization of LiN(CN) 2

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

Keefer, Derek W.; Gou, Huiyang; Purdy, Andrew P.

The high-pressure behavior of lithium dicyanamide (LiN(CN) 2) was studied with in situ Raman and infrared (IR) spectroscopies, and synchrotron angle-dispersive powder X-ray diffraction (PXRD) in a diamond anvil cell (DAC) to 22 GPa. The fundamental vibrational modes associated with molecular units were assigned using a combination of experimental data and density functional perturbation theory. Some low-frequency modes were observed for the first time. On the basis of spectroscopic and diffraction data, we suggest a polymorphic phase transformation at ~8 GPa, wherein dicyanamide ions remain as discrete molecular species. Above ca. 18 GPa, dicyanamide units polymerize, forming a largely disorderedmore » network, and the extent of polymerization may be increased by annealing at elevated temperature. The polymerized product consists of tricyanomelaminate-like groups containing sp 2-hybidized carbon–nitrogen bonds and exhibits a visible absorption edge near 540 nm. The product is recoverable to ambient conditions but is not stable in air/moisture.« less

Artificial biofilms establish the role of matrix interactions in staphylococcal biofilm assembly and disassembly.

PubMed

Stewart, Elizabeth J; Ganesan, Mahesh; Younger, John G; Solomon, Michael J

2015-08-14

We demonstrate that the microstructural and mechanical properties of bacterial biofilms can be created through colloidal self-assembly of cells and polymers, and thereby link the complex material properties of biofilms to well understood colloidal and polymeric behaviors. This finding is applied to soften and disassemble staphylococcal biofilms through pH changes. Bacterial biofilms are viscoelastic, structured communities of cells encapsulated in an extracellular polymeric substance (EPS) comprised of polysaccharides, proteins, and DNA. Although the identity and abundance of EPS macromolecules are known, how these matrix materials interact with themselves and bacterial cells to generate biofilm morphology and mechanics is not understood. Here, we find that the colloidal self-assembly of Staphylococcus epidermidis RP62A cells and polysaccharides into viscoelastic biofilms is driven by thermodynamic phase instability of EPS. pH conditions that induce phase instability of chitosan produce artificial S. epidermidis biofilms whose mechanics match natural S. epidermidis biofilms. Furthermore, pH-induced solubilization of the matrix triggers disassembly in both artificial and natural S. epidermidis biofilms. This pH-induced disassembly occurs in biofilms formed by five additional staphylococcal strains, including three clinical isolates. Our findings suggest that colloidal self-assembly of cells and matrix polymers produces biofilm viscoelasticity and that biofilm control strategies can exploit this mechanism.

Artificial biofilms establish the role of matrix interactions in staphylococcal biofilm assembly and disassembly

PubMed Central

Stewart, Elizabeth J.; Ganesan, Mahesh; Younger, John G.; Solomon, Michael J.

2015-01-01

We demonstrate that the microstructural and mechanical properties of bacterial biofilms can be created through colloidal self-assembly of cells and polymers, and thereby link the complex material properties of biofilms to well understood colloidal and polymeric behaviors. This finding is applied to soften and disassemble staphylococcal biofilms through pH changes. Bacterial biofilms are viscoelastic, structured communities of cells encapsulated in an extracellular polymeric substance (EPS) comprised of polysaccharides, proteins, and DNA. Although the identity and abundance of EPS macromolecules are known, how these matrix materials interact with themselves and bacterial cells to generate biofilm morphology and mechanics is not understood. Here, we find that the colloidal self-assembly of Staphylococcus epidermidis RP62A cells and polysaccharides into viscoelastic biofilms is driven by thermodynamic phase instability of EPS. pH conditions that induce phase instability of chitosan produce artificial S. epidermidis biofilms whose mechanics match natural S. epidermidis biofilms. Furthermore, pH-induced solubilization of the matrix triggers disassembly in both artificial and natural S. epidermidis biofilms. This pH-induced disassembly occurs in biofilms formed by five additional staphylococcal strains, including three clinical isolates. Our findings suggest that colloidal self-assembly of cells and matrix polymers produces biofilm viscoelasticity and that biofilm control strategies can exploit this mechanism. PMID:26272750

Direct evidence for the gas phase thermal polymerization of styrene. Determination of the initiation mechanism and structures of the early oligomers by ion mobility.

PubMed

Alsharaeh, Edreese H; Ibrahim, Yehia M; El-Shall, M Samy

2005-05-04

We present here direct evidence for the thermal self-initiated polymerization of styrene in the gas phase and establish that the initiation process proceeds via essentially the same mechanism (the Mayo mechanism) as in condensed phase polymerization. Furthermore, we provide structural identifications of the dimers and trimers formed in the gas phase.

Polymerization Behavior of Hydrophilic-Rich Phase of Dentin Adhesive

PubMed Central

Abedin, F.; Parthasarathy, R.; Misra, A.; Spencer, P.

2015-01-01

The 2-fold objectives of this study were 1) to understand whether model hydrophobic- and hydrophilic-rich phase mimics of dentin adhesive polymerize similarly and 2) to determine which factor, the dimethacrylate component, bisphenol A glycerolate dimethacrylate (BisGMA) or photoinitiator concentration, has greater influence on the polymerization of the hydrophilic-rich phase mimic. Current dentin adhesives are sensitive to moisture, as evidenced by nanoleakage in the hybrid layer and phase separation into hydrophobic- and hydrophilic-rich phases. Phase separation leads to limited availability of the cross-linkable dimethacrylate monomer and hydrophobic photoinitiators within the hydrophilic-rich phase. Model hydrophobic-rich phase was prepared as a single-phase solution by adding maximum wt% deuterium oxide (D2O) to HEMA/BisGMA neat resins containing 45 wt% 2-hydroxyethyl methacrylate (HEMA). Mimics of the hydrophilic-rich phase were prepared similarly but using HEMA/BisGMA neat resins containing 95, 99, 99.5, and 100 wt% HEMA. The hydrophilic-rich mimics were prepared with standard or reduced photoinitiator content. The photoinitiator systems were camphorquinone (CQ)/ethyl 4-(dimethylamino)benzoate (EDMAB) with or without [3-(3, 4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-2-hydroxypropyl]trimethylammonium chloride (QTX). The polymerization kinetics was monitored using a Fourier transform infrared spectrophotometer with a time-resolved collection mode. The hydrophobic-rich phase exhibited a significantly higher polymerization rate compared with the hydrophilic-rich phase. Postpolymerization resulting in the secondary rate maxima was observed for the hydrophilic-rich mimic. The hydrophilic-rich mimics with standard photoinitiator concentration but varying cross-linker (BisGMA) content showed postpolymerization and a substantial degree of conversion. In contrast, the corresponding formulations with reduced photoinitiator concentrations exhibited lower polymerization and inhibition/delay of postpolymerization within 2 h. Under conditions relevant to the wet, oral environment, photoinitiator content plays an important role in the polymerization of the hydrophilic-rich phase mimic. Since the hydrophilic-rich phase is primarily water and monomethacrylate monomer (e.g., HEMA as determined previously), substantial polymerization is important to limit the potential toxic response from HEMA leaching into the surrounding tissues. PMID:25576471

Thermoset molecular composites

DOEpatents

Benicewicz, Brian C.; Douglas, Elliot P.; Hjelm, Jr., Rex P.

1996-01-01

A polymeric composition including a liquid crystalline polymer and a thermosettable liquid crystalline monomer matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms and a polymeric composition including a liquid crystalline polymer and a liquid crystalline thermoset matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms are disclosed.

Characterization of hydrophilic-rich phase mimic in dentin adhesive and computer-aided molecular design of water compatible visible light initiators

NASA Astrophysics Data System (ADS)

Abedin, Farhana

The clinical lifetime of moderate-to-large dental composite restorations is lower than dental amalgam restorations. With the imminent and significant reduction in the use and availability of dental amalgam, the application of composite for the restoration of teeth will increase. Since composite has a higher failure rate, the increased use of composite will translate to an increase in the frequency of dental restoration replacement, overall cost for dental health and discomfort for patients. The composite is too viscous to bond directly to the tooth and thus, a low viscosity adhesive is used to form the bond between the composite and tooth. The bond at the adhesive/tooth is intended to form an impervious seal that protects the restored tooth from acids, oral fluids and bacteria that will undermine the composite restoration. The integrity of the adhesive/tooth bond (the exposed tooth structure is largely composed of enamel and dentin) plays an important role in preventing secondary caries which undermine the composite restoration. This study focuses on the durability of etch-and-rinse dental adhesives. As the adhesive infiltrates the demineralized dentin matrix, it undergoes phase separation into hydrophobic- and hydrophilic-rich phases. The hydrophilic-rich phase contains the conventional hydrophobic photo-initiator system (camphorquinone/ethyl 4-(dimethylamino)benzoate) and cross-linker both in inadequate concentrations. This may compromise the polymerization reaction and the cross-linking density of this phase, making it vulnerable to failure. The goal of this study is to characterize the hydrophilic-rich phase of the dental adhesive by monitoring its polymerization kinetics and glass transition temperature under the presence of an iodonium salt (reaction accelerator), and varying water concentration, photo-initiator concentration and light intensity. The final goal is to develop a computational framework for designing water compatible visible light photosensitizers specifically for the hydrophilic-rich phase of dental adhesives. It was observed that the degree of conversion of the hydrophilic-rich mimics is dominated by the photo-initiator concentration and not the cross-linker. A secondary rate maxima was observed in the case of hydrophilic-rich phase mimics which was associated with the formation of microgels during polymerization. A polymerization mechanism involving polymerization- and solvent-induced phase separation was proposed for the hydrophilic-rich mimics. The hydrophilic dental resins were sensitive to light intensity, i.e. at low light intensities the degree of conversion of the hydrophilic resin was reduced substantially in the presence of camphorquinone/ethyl 4-(dimethylamino)benzoate as photo-initiators, whereas a substantial degree of conversion was observed for the hydrophobic resin even at these lower light intensities. The addition of iodonium salt in the hydrophilic resin significantly improved the degree of conversion of the hydrophilic resin at low light intensities. These studies also showed that the iodonium salt could lead to enhanced cyclization and shorter polymer chain lengths within the hydrophilic-rich phase. For the physically separated hydrophilic-rich phase specimens, it was observed that in the presence of the conventional photo-initiator system (camphorquinone/ethyl 4-(dimethylamino)benzoate), there was no polymerization, mostly due to the insufficient partition concentrations of the photo-initiator components within this phase. The addition of iodoinum salt in this case significantly improved the degree of conversion but it was still significantly lower. These studies indicated that the overall polymerization efficiency of the hydrophilic-rich phase was lower than the hydrophobic-rich phase. The lower polymerization efficiency of the hydrophilic-rich phase led to a phase that lacks integrity; the hydrophilic-rich phase could be infiltrated by oral fluids and cariogenic bacteria. The infiltration of these noxious agents at the interface between the material and tooth could pave the way for enhanced degradation of the tooth structure (collagen and mineral) as well as the adhesive polymer. Novel photosensitizer molecules were proposed to improve the polymerization efficiency of this phase. Computer-aided molecular design (CAMD) was employed to obtain the new photosensitizers. These photosensitizers were capable of improving the degree of conversion of the hydrophilic-rich phase. An enhanced degree of conversion of the hydrophilic-rich phase would lead to a better seal at the adhesive/dentin interface and higher bond strength. Computer-aided molecular design (CAMD) is a fast and inexpensive technique compared to the conventional trial-and-error method to rationally design products. (Abstract shortened by ProQuest.).

A thermoplastic/thermoset blend exhibiting thermal mending and reversible adhesion.

PubMed

Luo, Xiaofan; Ou, Runqing; Eberly, Daniel E; Singhal, Amit; Viratyaporn, Wantinee; Mather, Patrick T

2009-03-01

In this paper, we report on the development of a new and broadly applicable strategy to produce thermally mendable polymeric materials, demonstrated with an epoxy/poly(-caprolactone) (PCL) phase-separated blend. The initially miscible blend composed of 15.5 wt % PCL undergoes polymerization-induced phase separation during cross-linking of the epoxy, yielding a "bricks and mortar" morphology wherein the epoxy phase exists as interconnected spheres (bricks) interpenetrated with a percolating PCL matrix (mortar). The fully cured material is stiff, strong, and durable. A heating-induced "bleeding" behavior was witnessed in the form of spontaneous wetting of all free surfaces by the molten PCL phase, and this bleeding is capable of repairing damage by crack-wicking and subsequent recrystallization with only minor concomitant softening during that process. The observed bleeding is attributed to volumetric thermal expansion of PCL above its melting point in excess of epoxy brick expansion, which we term differential expansive bleeding (DEB). In controlled thermal-mending experiments, heating of a cracked specimen led to PCL extrusion from the bulk to yield a liquid layer bridging the crack gap. Upon cooling, a "scar" composed of PCL crystals formed at the site of the crack, restoring a significant portion of the mechanical strength. When a moderate force was applied to assist crack closure, thermal-mending efficiencies exceeded 100%. We further observed that the DEB phenomenon enables strong and facile adhesion of the same material to itself and to a variety of materials, without any requirement for macroscopic softening or flow.

Induction of HoxB Transcription by Retinoic Acid Requires Actin Polymerization

PubMed Central

Ferrai, Carmelo; Naum-Onganía, Gabriela; Longobardi, Elena; Palazzolo, Martina; Disanza, Andrea; Diaz, Victor M.; Crippa, Massimo P.; Scita, Giorgio

2009-01-01

We have analyzed the role of actin polymerization in retinoic acid (RA)-induced HoxB transcription, which is mediated by the HoxB regulator Prep1. RA induction of the HoxB genes can be prevented by the inhibition of actin polymerization. Importantly, inhibition of actin polymerization specifically affects the transcription of inducible Hox genes, but not that of their transcriptional regulators, the RARs, nor of constitutively expressed, nor of actively transcribed Hox genes. RA treatment induces the recruitment to the HoxB2 gene enhancer of a complex composed of “elongating” RNAPII, Prep1, β-actin, and N-WASP as well as the accessory splicing components p54Nrb and PSF. We show that inhibition of actin polymerization prevents such recruitment. We conclude that inducible Hox genes are selectively sensitive to the inhibition of actin polymerization and that actin polymerization is required for the assembly of a transcription complex on the regulatory region of the Hox genes. PMID:19477923

Induction of HoxB transcription by retinoic acid requires actin polymerization.

PubMed

Ferrai, Carmelo; Naum-Onganía, Gabriela; Longobardi, Elena; Palazzolo, Martina; Disanza, Andrea; Diaz, Victor M; Crippa, Massimo P; Scita, Giorgio; Blasi, Francesco

2009-08-01

We have analyzed the role of actin polymerization in retinoic acid (RA)-induced HoxB transcription, which is mediated by the HoxB regulator Prep1. RA induction of the HoxB genes can be prevented by the inhibition of actin polymerization. Importantly, inhibition of actin polymerization specifically affects the transcription of inducible Hox genes, but not that of their transcriptional regulators, the RARs, nor of constitutively expressed, nor of actively transcribed Hox genes. RA treatment induces the recruitment to the HoxB2 gene enhancer of a complex composed of "elongating" RNAPII, Prep1, beta-actin, and N-WASP as well as the accessory splicing components p54Nrb and PSF. We show that inhibition of actin polymerization prevents such recruitment. We conclude that inducible Hox genes are selectively sensitive to the inhibition of actin polymerization and that actin polymerization is required for the assembly of a transcription complex on the regulatory region of the Hox genes.

Design and preparation of polymeric scaffolds for tissue engineering.

PubMed

Weigel, Thomas; Schinkel, Gregor; Lendlein, Andreas

2006-11-01

Polymeric scaffolds for tissue engineering can be prepared with a multitude of different techniques. Many diverse approaches have recently been under development. The adaptation of conventional preparation methods, such as electrospinning, induced phase separation of polymer solutions or porogen leaching, which were developed originally for other research areas, are described. In addition, the utilization of novel fabrication techniques, such as rapid prototyping or solid free-form procedures, with their many different methods to generate or to embody scaffold structures or the usage of self-assembly systems that mimic the properties of the extracellular matrix are also described. These methods are reviewed and evaluated with specific regard to their utility in the area of tissue engineering.

Design and in vitro evaluation of multiparticulate floating drug delivery system of zolpidem tartarate.

PubMed

Amrutkar, P P; Chaudhari, P D; Patil, S B

2012-01-01

Zolpidem tartarate is a non-benzodiazepine, sedative-hypnotic, which finds its major use in various types of insomnia. The present work relates to development of multiparticulate floating drug delivery system based on gas generation technique to prolong the gastric residence time and to increase the overall bioavailability. Modified release dosage form of zolpidem tartarate adapted to release over a predetermined time period, according to biphasic profile of dissolution, where the first phase is immediate release phase for inducing the sleep and the second phase is modified release phase for maintaining the sleep up to 10 h. The system consists of zolpidem tartarate layered pellets coated with effervescent layer and polymeric membrane. The floating ability and in vitro drug release of the system were dependent on amount of the effervescent agent (sodium bicarbonate) layered onto the drug layered pellets, and coating level of the polymeric membrane (Eudragit(®) NE 30D). The system could float completely within 5 min and maintain the floating over a period of 10 h. The multiparticulate floating delivery system of zolpidem tartarate with rapid floating and modified drug release was obtained. Copyright © 2011 Elsevier B.V. All rights reserved.

Detection Of Gas-Phase Polymerization in SiH4 And GeH4

NASA Technical Reports Server (NTRS)

Shing, Yuh-Han; Perry, Joseph W.; Allevato, Camillo E.

1990-01-01

Inelastic scattering of laser light found to indicate onset of gas-phase polymerization in plasma-enhanced chemical-vapor deposition (PECVD) of photoconductive amorphous hydrogenated silicon/germanium alloy (a-SiGe:H) film. In PECVD process, film deposited from radio-frequency glow-discharge plasma of silane (SiH4) and germane (GeH4) diluted with hydrogen. Gas-phase polymerization undesirable because it causes formation of particulates and defective films.

Effect of cooling (4°C) and cryopreservation on cytoskeleton actin and protein tyrosine phosphorylation in buffalo spermatozoa.

PubMed

Naresh, Sai

2016-02-01

Semen cryopreservation is broadly utilized as a part of the bovine reproducing industry, a large portion of the spermatozoa does not survive and the majority of those that do survive experience various molecular and physiological changes that influence their fertilizing capacity. The main aim of this study is to determine the effect of cooling (4 °C) and cryopreservation on cytoskeleton actin, tyrosine phosphorylation and quality of buffalo spermatozoa, and to determine the similarity between in vitro capacitation and cryopreservation induced capacitation like changes. To achieve this, Western blot was used to examine the changes in actin expression and protein tyrosine phosphorylation, whereas changes in actin polymerization, localization of actin and protein tyrosine phosphorylation during capacitation and cryopreservation were evaluated by indirect immunofluorescence technique. Localization studies revealed that the actin localized to flagella and acrosome membrane regions and following, capacitation it migrated towards the acrosome region of sperm. Time dependent increase in actin polymerization and protein tyrosine phosphorylation was observed during in vitro capacitation. The cooling phase (4 °C) and cryopreservation processes resulted in the loss/damage of cytoskeleton actin. In addition, we performed the actin polymerization and protein tyrosine phosphorylation in cooled and cryopreserved buffalo spermatozoa. Interestingly, cooling and cryopreservation induces actin polymerization and protein tyrosine phosphorylation, which were similar to in vitro capacitation (cryo-capacitation). These changes showed 1.3 folds reduction in the sperm quality parameters which includes motility, viability and plasma membrane integrity. Furthermore, our findings indicate that cooling and cryopreservation damages the cytoskeleton actin and also induces capacitation like changes such as protein tyrosine phosphorylation and actin polymerization. This could be one of the main reasons for reduced sperm quality and fertility failure of cryopreserved spermatozoa. Copyright © 2015 Elsevier Inc. All rights reserved.

Thermodynamic and kinetic characterization of polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography.

PubMed

Howerton, Samuel B; McGuffin, Victoria L

2003-07-15

The retention of six polycyclic aromatic hydrocarbons (PAHs) was characterized by reversed-phase liquid chromatography. The PAHs were detected by laser-induced fluorescence at four points along an optically transparent capillary column. The profiles were characterized in space and time using an exponentially modified Gaussian equation. The resulting parameters were used to calculate the retention factors, as well as the concomitant changes in molar enthalpy and molar volume, for each PAH on monomeric (2.7 micromol/m2) and polymeric (5.4 micromol/m2) octadecylsilica. The changes in molar enthalpy become more exothermic as ring number increases and as annelation structure becomes less condensed. The changes in molar volume become more negative as ring number increases for the planar PAHs, but are positive for the nonplanar solutes. In addition, the rate constants, as well as the concomitant activation enthalpy and activation volume, are calculated for the first time. The kinetic data demonstrate that many of the PAHs exhibit very fast transitions between the mobile and stationary phases. The transition state is very high in energy, and the activation enthalpies and volumes become greater as ring number increases and as annelation structure becomes less condensed. The changes in thermodynamic and kinetic behavior are much more pronounced for the polymeric phase than for the monomeric phase.

Light-driven liquid microlenses

NASA Astrophysics Data System (ADS)

Angelini, A.; Pirani, F.; Frascella, F.; Ricciardi, S.; Descrovi, E.

2017-02-01

We propose a liquid polymeric compound based on photo-responsive azo-polymers to be used as light-activated optical element with tunable and reversible functionalities. The interaction of a laser beam locally modifies the liquid density thus producing a refractive index gradient. The laser induced refractive index profiles are observed along the optical axis of the microscope to evaluate the total phase shift induced and along the orthogonal direction to provide the axial distribution of the refractive index variation. The focusing and imaging properties of the liquid lenses as functions of the light intensity are illustrated.

Noncovalent Polymerization of Mesogens Crystallizes Lysozyme: Correlation between Nonamphiphilic Lyotropic Liquid Crystal Phase and Protein Crystal Formation

PubMed Central

Simon, Karen A.; Shetye, Gauri S.; Englich, Ulrich; Wu, Lei; Luk, Yan-Yeung

2011-01-01

Crystallization of proteins is important for fundamental studies and biopharmaceutical development but remains largely an empirical science. Here, we report the use of organic salts that can form a class of unusual non-amphiphilic lyotropic liquid crystals to crystallize the protein lysozyme. Certain non-amphiphilic organic molecules with fused aromatic rings and two charges can assemble into stable thread-like noncovalent polymers that may further form liquid crystal phases in water, traditionally termed chromonic liquid crystals. Using five of these mesogenic molecules as additives to induce protein crystallization, we discover that molecules that can form liquid crystal phases in water are highly effective at inducing the crystal formation of lysozyme, even at concentrations significantly lower than that required for forming liquid crystal phases. This result reveals an example of inducing protein crystallization by the molecular assembly of the additives, and is consistent with a new mechanism by which the strong hydration of an assembly process provides a gradual means to compete for the water molecules to enable solvated proteins to form crystals. PMID:21786812

Near-Infrared-Induced Heating of Confined Water in Polymeric Particles for Efficient Payload Release

PubMed Central

2015-01-01

Near-infrared (NIR) light-triggered release from polymeric capsules could make a major impact on biological research by enabling remote and spatiotemporal control over the release of encapsulated cargo. The few existing mechanisms for NIR-triggered release have not been widely applied because they require custom synthesis of designer polymers, high-powered lasers to drive inefficient two-photon processes, and/or coencapsulation of bulky inorganic particles. In search of a simpler mechanism, we found that exposure to laser light resonant with the vibrational absorption of water (980 nm) in the NIR region can induce release of payloads encapsulated in particles made from inherently non-photo-responsive polymers. We hypothesize that confined water pockets present in hydrated polymer particles absorb electromagnetic energy and transfer it to the polymer matrix, inducing a thermal phase change. In this study, we show that this simple and highly universal strategy enables instantaneous and controlled release of payloads in aqueous environments as well as in living cells using both pulsed and continuous wavelength lasers without significant heating of the surrounding aqueous solution. PMID:24717072

Near-infrared-induced heating of confined water in polymeric particles for efficient payload release.

PubMed

Viger, Mathieu L; Sheng, Wangzhong; Doré, Kim; Alhasan, Ali H; Carling, Carl-Johan; Lux, Jacques; de Gracia Lux, Caroline; Grossman, Madeleine; Malinow, Roberto; Almutairi, Adah

2014-05-27

Near-infrared (NIR) light-triggered release from polymeric capsules could make a major impact on biological research by enabling remote and spatiotemporal control over the release of encapsulated cargo. The few existing mechanisms for NIR-triggered release have not been widely applied because they require custom synthesis of designer polymers, high-powered lasers to drive inefficient two-photon processes, and/or coencapsulation of bulky inorganic particles. In search of a simpler mechanism, we found that exposure to laser light resonant with the vibrational absorption of water (980 nm) in the NIR region can induce release of payloads encapsulated in particles made from inherently non-photo-responsive polymers. We hypothesize that confined water pockets present in hydrated polymer particles absorb electromagnetic energy and transfer it to the polymer matrix, inducing a thermal phase change. In this study, we show that this simple and highly universal strategy enables instantaneous and controlled release of payloads in aqueous environments as well as in living cells using both pulsed and continuous wavelength lasers without significant heating of the surrounding aqueous solution.

Radical polymerization of capillary bridges between micron-sized particles in liquid bulk phase as a low temperature route to produce porous solid materials.

PubMed

Hauf, Katharina; Riazi, Kamran; Willenbacher, Norbert; Koos, Erin

2017-10-01

We present a generic and versatile low temperature route to produce macro-porous bodies with porosity and pore size distribution that are adjustable in a wide range. Capillary suspensions, where the minor fluid is a monomer, are used as pre-cursors. The monomer is preferentially located between the particles, creating capillary bridges, resulting in a strong, percolating network. Thermally induced polymerization of these bridges at temperatures below 100 °C for less than 5 hours and subsequent removal of the bulk fluid yields macroscopic, self-supporting solid bodies with high porosity. This process is demonstrated using methylmethacrylate and hydroxyethylmethacrlyate with glass particles as a model system. The produced PMMA had a molecular weight of about 500.000 g/mol and dispersity about three. Application specific porous bodies, including PMMA particles connected by PMMA bridges, micron-sized capsules containing phase change material with high inner surface, and porous graphite membranes with high electrical conductivity, are also shown.

Radical polymerization of capillary bridges between micron-sized particles in liquid bulk phase as a low temperature route to produce porous solid materials

PubMed Central

Hauf, Katharina; Riazi, Kamran; Willenbacher, Norbert; Koos, Erin

2018-01-01

We present a generic and versatile low temperature route to produce macro-porous bodies with porosity and pore size distribution that are adjustable in a wide range. Capillary suspensions, where the minor fluid is a monomer, are used as pre-cursors. The monomer is preferentially located between the particles, creating capillary bridges, resulting in a strong, percolating network. Thermally induced polymerization of these bridges at temperatures below 100 °C for less than 5 hours and subsequent removal of the bulk fluid yields macroscopic, self-supporting solid bodies with high porosity. This process is demonstrated using methylmethacrylate and hydroxyethylmethacrlyate with glass particles as a model system. The produced PMMA had a molecular weight of about 500.000 g/mol and dispersity about three. Application specific porous bodies, including PMMA particles connected by PMMA bridges, micron-sized capsules containing phase change material with high inner surface, and porous graphite membranes with high electrical conductivity, are also shown. PMID:29503494

Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid

NASA Astrophysics Data System (ADS)

Deng, Bo; Yu, Yang; Zhang, Bowu; Yang, Xuanxuan; Li, Linfan; Yu, Ming; Li, Jingye

2011-02-01

Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid-base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results indicated that adding sulfuric acid and Mohr's salt simultaneously in AAc or MAA solutions led to a strong enhancement in the degree of grafting. The grafted PVDF powder was cast into microfiltration (MF) membranes using the phase inversion method and some properties of the obtained MF membranes were characterized.

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene substrates

NASA Astrophysics Data System (ADS)

Zanini, S.; Orlandi, M.; Colombo, C.; Grimoldi, E.; Riccardi, C.

2009-08-01

A detailed study of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) substrates (membranes and films) is presented. The process consists of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. Influence of the solution and plasma parameters on the process efficiency evaluated in terms of amount of grafted polymer, coverage uniformity and substrates wettability, are investigated. The plasma-induced graft-polymerization of PEGA is then followed by sample weighting, water droplet adsorption time and contact angle measurements, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in phosphate buffer saline (PBS) at 37 °C. Results clearly indicates that plasma-induced graft-polymerization of PEGA is a practical methodology for anti-fouling surface modification of materials.

Super-hydrophobic coatings based on non-solvent induced phase separation during electro-spraying.

PubMed

Gao, Jiefeng; Huang, Xuewu; Wang, Ling; Zheng, Nan; Li, Wan; Xue, Huaiguo; Li, Robert K Y; Mai, Yiu-Wing

2017-11-15

The polymer solution concentration determines whether electrospinning or electro-spraying occurs, while the addition of the non-solvent into the polymer solution strongly influences the surface morphology of the obtained products. Both smooth and porous surfaces of the electro-sprayed microspheres can be harvested by choosing different non-solvent and its amount as well as incorporating polymeric additives. The influences of the solution concentration, weight ratio between the non-solvent and the copolymer, and the polymeric additives on the surface morphology and the wettability of the electro-sprayed products were systematically studied. Surface pores and/or asperities on the microsphere surface were mainly caused by the non-solvent induced phase separation (NIPS) and subsequent evaporation of the non-solvent during electro-spraying. With increasing polymer solution concentration, the microsphere was gradually changed to the bead-on-string geometry and finally to a nanofiber form, leading to a sustained decrease of the contact angle (CA). It was found that the substrate coatings derived from the microspheres possessing hierarchical surface pores or dense asperities had high surface roughness and super-hydrophobicity with CAs larger than 150° while sliding angles smaller than 10°; but coatings composed of microspheres with smooth surfaces gave relatively low CAs. Copyright © 2017 Elsevier Inc. All rights reserved.

Atrazine Molecular Imprinted Polymers: Comparative Analysis by Far-Infrared and Ultraviolet Induced Polymerization

PubMed Central

Chen, Jun; Bai, Lian-Yang; Liu, Kun-Feng; Liu, Run-Qiang; Zhang, Yu-Ping

2014-01-01

Atrazine molecular imprinted polymers (MIPs) were comparatively synthesized using identical polymer formulation by far-infrared (FIR) radiation and ultraviolet (UV)-induced polymerization, respectively. Equilibrium binding experiments were carried out with the prepared MIPs; the results showed that MIPuv possessed specific binding to atrazine compared with their MIPFIR radiation counterparts. Scatchard plot’s of both MIPs indicated that the affinities of the binding sites in MIPs are heterogeneous and can be approximated by two dissociation-constants corresponding to the high-and low-affinity binding sites. Moreover, several common pesticides including atrazine, cyromazine, metamitron, simazine, ametryn, terbutryn were tested to determine their specificity, similar imprinting factor (IF) and different selectivity index (SI) for both MIPs. Physical characterization of the polymers revealed that the different polymerization methods led to slight differences in polymer structures and performance by scanning electron microscope (SEM), Fourier transform infrared absorption (FT-IR), and mercury analyzer (MA). Finally, both MIPs were used as selective sorbents for solid phase extraction (SPE) of atrazine from lake water, followed by high performance liquid chromatography (HPLC) analysis. Compared with commercial C18 SPE sorbent (86.4%–94.8%), higher recoveries of atrazine in spiked lake water were obtained in the range of 90.1%–97.1% and 94.4%–101.9%, for both MIPs, respectively. PMID:24398982

Shedding light on the different behavior of ionic and nonionic surfactants in emulsion polymerization: from atomistic simulations to experimental observations.

PubMed

Magi Meconi, Giulia; Ballard, Nicholas; Asua, José M; Zangi, Ronen

2017-12-06

Although surfactants are known to play a vital role in polymerization reactions carried out in dispersed media, many aspects of their use are poorly understood, perhaps none more so than the vastly different action of ionic and nonionic surfactants in emulsion polymerization. In this work, we combine experimental measurements of emulsion polymerization of styrene with atomistic molecular dynamics simulations to better understand the behavior of surfactants at monomer/polymer-water interfaces. In a batch emulsion polymerization of styrene, the nonionic surfactant Disponil AFX 1080 leads to two nucleation periods, in contrast to the behavior observed for the ionic surfactant SDS. This can be explained by the absorption of the nonionic surfactant into the organic phase at the early stages of the polymerization reaction which is then released as the reaction progresses. Indeed, we find that the partition coefficient of the surfactant between the organic phase and water increases with the amount of monomer in the former, and preferential partitioning is detected to organic phases containing at least 55% styrene. Results from molecular dynamics simulations confirm that spontaneous dissolution of the non-ionic surfactant into a styrene-rich organic phase occurs above a critical concentration of the surfactant adsorbed at the interface. Above this critical concentration, a linear correlation between the amount of surfactant adsorbed at the interface and that absorbed inside the organic phase is observed. To facilitate this absorption into a completely hydrophobic medium, water molecules accompany the intruding surfactants. Similar simulations but with the ionic surfactant instead did not result in any absorption of the surfactant into a neat styrene phase, likely because of its strongly hydrophilic head group. The unusual partitioning behavior of nonionic surfactants explains a number of observable features of emulsion polymerization reactions which use nonionic surfactants and should help with future development of processes for improved control over polymerization.

Bio-inspired method to obtain multifunctional dynamic nanocomposites

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

Kushner, Aaron M.; Guan, Zhibin; Williams, Gregory

A method for a polymeric or nanocomposite material. The method includes assembling a multiphase hard-soft structure, where the structure includes a hard micro- or nano-phase, and a soft micro- or nano-phase that includes a polymeric scaffold. In the method, the polymeric scaffold includes dynamically interacting motifs and has a glass transition temperature (T.sub.g) lower than the intended operating temperature of the material.

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

NASA Astrophysics Data System (ADS)

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

2016-06-01

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

Hydroxyapatite induces spontaneous polymerization of model self-etch dental adhesives.

PubMed

Zhang, Ying; Wu, Ningjing; Bai, Xinyan; Xu, Changqi; Liu, Yi; Wang, Yong

2013-10-01

The objective of this study is to report for the first time the spontaneous polymerization phenomenon of self-etch dental adhesives induced by hydroxylapatite (HAp). Model self-etch adhesives were prepared by using a monomer mixture of bis[2-(methacryloyloxy)ethyl] phosphate (2MP) with 2-hydroxyethyl methacrylate (HEMA). The initiator system consisted of camphorquinone (CQ, 0.022 mmol/g) and ethyl 4-dimethylaminobenzoate (4E, 0.022-0.088 mmol/g). HAp (2-8 wt.%) was added to the neat model adhesive. In a dark environment, the polymerization was monitored in-situ using ATR/FT-IR, and the mechanical properties of the polymerized adhesives were evaluated using nanoindentation technique. Results indicated that spontaneous polymerization was not observed in the absence of HAp. However, as different amounts of HAp were incorporated into the adhesives, spontaneous polymerization was induced. Higher HAp content led to higher degree of conversion (DC), higher rate of polymerization (RP) and shorter induction period (IP). In addition, higher 4E content also elevated DC and RP and reduced IP of the adhesives. Nanoindentation result suggested that the Young's modulus of the polymerized adhesives showed similar dependence on HAp and 4E contents. In summary, interaction with HAp could induce spontaneous polymerization of the model self-etch adhesives. This result provides important information for understanding the initiation mechanism of the self-etch adhesives, and may be of clinical significance to strengthen the adhesive/dentin interface based on the finding. Copyright © 2013 Elsevier B.V. All rights reserved.

Hydroxyapatite induces spontaneous polymerization of model self-etch dental adhesives

PubMed Central

Zhang, Ying; Wu, Ningjing; Bai, Xinyan; Xu, Changqi; Liu, Yi; Wang, Yong

2013-01-01

The objective of this study is to report for the first time the spontaneous polymerization phenomenon of self-etch dental adhesives induced by hydroxylapatite (HAp). Model self-etch adhesives were prepared by using a monomer mixture of bis[2-(methacryloyloxy)ethyl] phosphate (2MP) with 2-hydroxyethyl methacrylate (HEMA). The initiator system consisted of camphorquinone (CQ, 0.022 mmol/g) and ethyl 4-dimethylaminobenzoate (4E, 0.022–0.088 mmol/g). HAp (2–8 wt.%) was added to the neat model adhesive. In a dark environment, the polymerization was monitored in-situ using ATR/FT-IR, and the mechanical properties of the polymerized adhesives were evaluated using nanoindentation technique. Results indicated that spontaneous polymerization was not observed in the absence of HAp. However, as different amounts of HAp were incorporated into the adhesives, spontaneous polymerization was induced. Higher HAp content led to higher degree of conversion (DC), higher rate of polymerization (RP) and shorter induction period (IP). In addition, higher 4E content also elevated DC and RP and reduced IP of the adhesives. Nanoindentation result suggested that the Young's modulus of the polymerized adhesives showed similar dependence on HAp and 4E contents. In summary, interaction with HAp could induce spontaneous polymerization of the model self-etch adhesives. This result provides important information for understanding the initiation mechanism of the self-etch adhesives, and may be of clinical significance to strengthen the adhesive/dentin interface based on the finding. PMID:23910263

Processes for microemulsion polymerization employing novel microemulsion systems

DOEpatents

Beckman, Eric J.; Smith, Richard D.; Fulton, John L.

1990-06-12

This invention is directed to a microemulsion system comprising a first phase including a low-polarity fluid material which is a gas at standard temperature and pressure, and which has a cloud-point density. It also includes a second phase including a polar fluid, typically water, a monomer, preferably a monomer soluble in the polar fluid, and a microemulsion promoter for facilitating the formation of micelles including the monomer in the system. In the subject process, micelles including the monomer are formed in the first phase. A polymerization initiator is introduced into the micelles in the microemulsion system. The monomer is then polymerized in the micelles, preferably in the core of the micelle, to produce a polymeric material having a relatively high molecular weight.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Liquid-liquid two phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review

PubMed Central

Elbert, Donald L.

2010-01-01

Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid-liquid two phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid-liquid two phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of these processes. The role of the kinetics of phase separation in determining the morphology of scaffolds and microspheres is also delineated. Brief descriptions of miniemulsion, microemulsion polymerization and ionotropic gelation are also included. PMID:20659596

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure.

PubMed

Yui, Yuko; Miyazaki, Shota; Ma, Yan; Ohira, Masayoshi; Fiehn, Oliver; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

2016-06-10

Separation of diastereomers of dl-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3mmID, 20cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic dl-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0°C, 536bar, while three peaks were observed when the separation was carried out either at 12.0°C at low pressure or at 20°C at 488bar. Higher temperature (30.0°C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0°C and 441bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0°C and 463bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of dl-α-tocopherol. Copyright © 2016. Published by Elsevier B.V.

Porous polymer networks and ion-exchange media and metal-polymer composites made therefrom

DOEpatents

Kanatzidis, Mercouri G; Katsoulidis, Alexandros

2015-03-10

Porous polymeric networks and composite materials comprising metal nanoparticles distributed in the polymeric networks are provided. Also provided are methods for using the polymeric networks and the composite materials in liquid- and vapor-phase waste remediation applications. The porous polymeric networks, are highly porous, three-dimensional structures characterized by high surface areas. The polymeric networks comprise polymers polymerized from aldehydes and phenolic molecules.

Porous polymer networks and ion-exchange media and metal-polymer composites made therefrom

DOEpatents

Kanatzidis, Mercouri G.; Katsoulidis, Alexandros

2016-10-18

Porous polymeric networks and composite materials comprising metal nanoparticles distributed in the polymeric networks are provided. Also provided are methods for using the polymeric networks and the composite materials in liquid- and vapor-phase waste remediation applications. The porous polymeric networks, are highly porous, three-dimensional structures characterized by high surface areas. The polymeric networks comprise polymers polymerized from aldehydes and phenolic molecules.

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization

NASA Astrophysics Data System (ADS)

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Purification of inkjet ink from water using liquid phase, electric discharge polymerization and cellulosic membrane filtration.

PubMed

Jordan, Alexander T; Hsieh, Jeffery S; Lee, Daniel T

2013-01-01

A method to separate inkjet ink from water was developed using a liquid phase, electric discharge process. The liquid phase, electric discharge process with filtration or sedimentation was shown to remove 97% of inkjet ink from solutions containing between 0.1-0.8 g/L and was consistent over a range of treatment conditions. Additionally, particle size analysis of treated allyl alcohol and treated propanol confirmed the electric discharge treatment has a polymerization mechanism, and small molecule analysis of treated methanol using gas chromatography and mass spectroscopy confirmed the mechanism was free radical initiated polymerization.

Method for nanoencapsulation of aerogels and nanoencapsulated aerogels produced by such method

NASA Technical Reports Server (NTRS)

Sullivan, Thomas A. (Inventor)

2007-01-01

A method for increasing the compressive modulus of aerogels comprising: providing aerogel substrate comprising a bubble matrix in a chamber; providing monomer to the chamber, the monomer comprising vapor phase monomer which polymerizes substantially free of polymerization byproducts; depositing monomer from the vapor phase onto the surface of the aerogel substrate under deposition conditions effective to produce a vapor pressure sufficient to cause the vapor phase monomer to penetrate into the bubble matrix and deposit onto the surface of the aerogel substrate, producing a substantially uniform monomer film; and, polymerizing the substantially uniform monomer film under polymerization conditions effective to produce polymer coated aerogel comprising a substantially uniform polymer coating substantially free of polymerization byproducts.Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating, said polymer coated aerogel comprising porosity and having a compressive modulus greater than the compressive modulus of the aerogel substrate, as measured by a 100 lb. load cell at 1 mm/minute in the linear range of 20% to 40% compression.

Tubulin polymerization promoting protein 1 (Tppp1) phosphorylation by Rho-associated coiled-coil kinase (rock) and cyclin-dependent kinase 1 (Cdk1) inhibits microtubule dynamics to increase cell proliferation.

PubMed

Schofield, Alice V; Gamell, Cristina; Suryadinata, Randy; Sarcevic, Boris; Bernard, Ora

2013-03-15

Tubulin polymerization promoting protein 1 (Tppp1) regulates microtubule (MT) dynamics via promoting MT polymerization and inhibiting histone deacetylase 6 (Hdac6) activity to increase MT acetylation. Our results reveal that as a consequence, Tppp1 inhibits cell proliferation by delaying the G1/S-phase and the mitosis to G1-phase transitions. We show that phosphorylation of Tppp1 by Rho-associated coiled-coil kinase (Rock) prevents its Hdac6 inhibitory activity to enable cells to enter S-phase. Whereas, our analysis of the role of Tppp1 during mitosis revealed that inhibition of its MT polymerizing and Hdac6 regulatory activities were necessary for cells to re-enter the G1-phase. During this investigation, we also discovered that Tppp1 is a novel Cyclin B/Cdk1 (cyclin-dependent kinase) substrate and that Cdk phosphorylation of Tppp1 inhibits its MT polymerizing activity. Overall, our results show that dual Rock and Cdk phosphorylation of Tppp1 inhibits its regulation of the cell cycle to increase cell proliferation.

Self-assembly of Nano-rods in Photosensitive Phase Separation

NASA Astrophysics Data System (ADS)

Liu, Ya; Kuksenok, Olga; Maresov, Egor; Balazs, Anna

2012-02-01

Computer simulations reveal how photo-induced chemical reactions in polymeric mixtures can be exploited to create long-range order in materials whose features range from the sub-micron to the nanoscale. The process is initiated by shining a spatially uniform light on a photosensitive AB binary blend, which thereby undergoes both a reversible chemical reaction and phase separation. When a well-collimated, higher intensity light is rastered over the sample, the system forms defect-free, spatially periodic structures. We now build on this approach by introducing nanorods that have a preferential affinity for one the phases in a binary mixture. By rastering over the sample with the higher intensity light, we can create ordered arrays of rods within periodically ordered materials in essentially one processing step.

Exploiting Photo-induced Reactions in Polymer Blends to Create Hierarchically Ordered, Defect-free Materials

ScienceCinema

Balazs, Anna [University of Pittsburgh, Pittsburgh, Pennsylvania, United States

2017-12-09

Computer simulations reveal how photo-induced chemical reactions can be exploited to create long-range order in binary and ternary polymeric materials. The process is initiated by shining a spatially uniform light over a photosensitive AB binary blend, which undergoes both a reversible chemical reaction and phase separation. We then introduce a well-collimated, higher-intensity light source. Rastering this secondary light over the sample locally increases the reaction rate and causes formation of defect-free, spatially periodic structures. These binary structures resemble either the lamellar or hexagonal phases of microphase-separated di-block copolymers. We measure the regularity of the ordered structures as a function of the relative reaction rates for different values of the rastering speed and determine the optimal conditions for creating defect-free structures in the binary systems. We then add a non-reactive homo-polymer C, which is immiscible with both A and B. We show that this component migrates to regions that are illuminated by the secondary, higher-intensity light, allowing us to effectively write a pattern of C onto the AB film. Rastering over the ternary blend with this collimated light now leads to hierarchically ordered patterns of A, B, and C. The findings point to a facile, non-intrusive process for manufacturing high-quality polymeric devices in a low-cost, efficient manner.

Preparation of Low fouling Polyethersulfone Membranes by Simultaneously Phase Separation and Redox Polymerization

NASA Astrophysics Data System (ADS)

Roihatin, A.; Susanto, H.

2017-05-01

This paper presents preparation of low fouling PES membranes by non solvent induced phase separation (NIPS) coupled with redox polymerization. The membrane characterization included water permeability, morphology structure (by SEM) and surface chemistry (by FTIR). Water permeability measurements showed thatthe membranes have water permeability within the range 10-50 L/h.m2.bar. Addition of PEG dan PEGMA intopolymer solution increased water permeability, whereas blending redox initiator and crosslinker, MBAA in polymer solution decreased water permeability. Surface morfology of membranes by SEM showed that unmodified PES membrane had smaller pore size than PEG or PEGMA modified PES membranes. Furthermore, PES-PEG or PES-PEGMA membranes modified by blending with redox initiator and MBAA as crosslinker showed smaller pore size than unmodified membrane. FTIR analysis showed that all membranes have typical spectraof PES polymer; however no additional peak was observed forthe membranes prepared with addition of PEG/PEGMA, initiator redox and also crosslinker. The addition of PEG/PEGMA, redox initiator and crosslinker resulted in membranes with high rejection and an acceptable flux as well as more stable due to relatively high fouling resistance.

Pressure-induced structural transformations and polymerization in ThC2

PubMed Central

Guo, Yongliang; Yu, Cun; Lin, Jun; Wang, Changying; Ren, Cuilan; Sun, Baoxing; Huai, Ping; Xie, Ruobing; Ke, Xuezhi; Zhu, Zhiyuan; Xu, Hongjie

2017-01-01

Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC2. PMID:28383571

Pressure-induced structural transformations and polymerization in ThC2

NASA Astrophysics Data System (ADS)

Guo, Yongliang; Yu, Cun; Lin, Jun; Wang, Changying; Ren, Cuilan; Sun, Baoxing; Huai, Ping; Xie, Ruobing; Ke, Xuezhi; Zhu, Zhiyuan; Xu, Hongjie

2017-04-01

Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC2.

Pressure-induced structural transformations and polymerization in ThC2.

PubMed

Guo, Yongliang; Yu, Cun; Lin, Jun; Wang, Changying; Ren, Cuilan; Sun, Baoxing; Huai, Ping; Xie, Ruobing; Ke, Xuezhi; Zhu, Zhiyuan; Xu, Hongjie

2017-04-06

Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC 2 ) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC 2 .

Controllable fabrication of porous free-standing polypyrrole films via a gas phase polymerization.

PubMed

Lei, Junyu; Li, Zhicheng; Lu, Xiaofeng; Wang, Wei; Bian, Xiujie; Zheng, Tian; Xue, Yanpeng; Wang, Ce

2011-12-15

A facile gas phase polymerization method has been proposed in this work to fabricate porous free-standing polypyrrole (PPy) films. In the presence of pyrrole vapor, the films are obtained in the gas/water interface spontaneously through the interface polymerization with the oxidant of FeCl(3) in the water. Both the thickness of the film and the size of the pores could be controlled by adjusting the concentrations of the oxidant and the reaction time. The as-prepared PPy films exhibited a superhydrophilic behavior due to its composition and porous structures. We have demonstrated a possible formation mechanism for the porous free-standing PPy films. This gas phase polymerization is shown to be readily scalable to prepare large area of PPy films. Copyright © 2011 Elsevier Inc. All rights reserved.

[Evaluation of chromatographic performance of polymerized ionic liquid stationary phase for capillary gas chromatography].

PubMed

Chen, Xiaoyan; Lu, Kai; Qi, Meiling; Fu, Ruonong

2009-11-01

The selectivity and thermal stability of ionic liquids as the stationary phases for capillary gas chromatography (CGC) have attracted much attention of researchers in recent years. In this study, 1-vinyl-3-benzyl imidazolium-bis(trifluoromethane-sulphonyl)imidate (VBIm-NTf2) was synthesized and polymerized (PVBIm-NTf2) in a CGC column. In comparison with VBIm-NTf2, PVBIm-NTf2 exhibits much better thermal stability and chromatographic selectivity, and achieves satisfactory resolution for Grob test mixture, alcohols mixture, esters mixture and aromatics mixture with narrow and symmetric peak shapes. The satisfactory resolution and selectivity of the polymerized column still remain after conditioned at 250 degrees C for 6 h. Additionally, the Abraham solvation parameters of PVBIm-NTf2 were determined and the interactions between the stationary phase and solutes were elucidated. The present work demonstrates that the polymerization is an effective way to improve the selectivity and thermal stability of common ionic liquids as CGC stationary phases.

The use of radiation-induced graft polymerization for modification of polymer track membranes

NASA Astrophysics Data System (ADS)

Shtanko, N. I.; Kabanov, V. Ya.; Apel, P. Yu.; Yoshida, M.

1999-05-01

Track membranes (TM) made of poly(ethylene terephtalate) (PET) and polypropylene (PP) films have a number of peculiarities as compared with other ones. They have high mechanical strength at a low thickness, narrow pore size distribution, low content of extractables. However, TM have some disadvantages such as low chemical resistance in alkaline media (PET TM), the low water flow rate due to the hydrophobic nature of their surface. The use of radiation-induced graft polymerization makes it possible to improve the basic characteristics of TM. In this communication our results on the modification of PET and PP TM are presented. The modified membranes were prepared by radiation-induced graft polymerization from the liquid phase. Three methods of grafting were used: (a) the direct method in argon atmosphere; (b) the pre-irradiation of TM in air followed by grafting in argon atmosphere; (c) pre-irradiation in vacuum followed by grafting in vacuum without contacting oxygen. The aim of the work was to investigate some properties of TM modified by grafted poly(methylvinyl pyridine) (PMVP) and poly(N-isopropylacrylamide) (PNIPAAM). It was shown that the modification of TM with hydrophilic polymer results in the growth of the water flow rate. In the past few years many works have been devoted to the synthesis of new polymers - the so-called "intelligent" materials - such as PNIPAAM. However, it is very difficult to make thin membranes of this polymer. Recently, it has been proposed to manufacture composite membranes by grafting stimulus-responsive polymers onto TM. Following this principle, we prepared thermosensitive membranes by the radiation-induced graft polymerization of N-isopropylacrylamide (NIPAAM) onto PET TM. PET TM with the pore size of about 1 μm and pore density of 10 6 cm -2 were first inserted into a solution of NIPAAM containing inhibitor of homopolymerization (CuCl 2) and then exposed to the γ-rays from a 60Co source. The transport properties of the grafted TM were investigated. The permeation of water through the TM was controlled by temperature. The grafted TM exhibited almost the same transition temperature (about 33°C) as that of PNIPAAM.

Multi-lobulation of the nucleus in prolonged S phase by nuclear expression of Chk tyrosine kinase.

PubMed

Nakayama, Yuji; Yamaguchi, Naoto

2005-04-01

Chk tyrosine kinase phosphorylates Src-family tyrosine kinases and suppresses their kinase activity. We recently showed that Chk localizes to the nucleus as well as the cytoplasm and inhibits cell proliferation. To investigate the role of nuclear Chk in proliferation, various Chk mutants were constructed and expressed. Nuclear localization of Chk-induced dynamic multi-lobulation of the nucleus and prolonged S phase of the cell cycle. The N-terminal domain of Chk and a portion of its kinase domain but not the kinase activity were responsible for induction of the multi-lobulation. Cell sorting analysis revealed that nuclear multi-lobulated cells were enriched in late S phase. Multi-lobulated nuclei were surrounded with lamin B1 that was particularly concentrated in concave regions of the nuclei. Furthermore, treatment with nocodazole or taxol disrupted multi-lobulation of the nucleus. These results suggest that nuclear multi-lobulation in late S phase, which is dependent on polymerization and depolymerization of microtubules, may be involved in nuclear Chk-induced inhibition of proliferation.

Preparation of Paraffin@Poly(styrene-co-acrylic acid) Phase Change Nanocapsules via Combined Miniemulsion/Emulsion Polymerization.

PubMed

Zhang, Feng; Liu, Tian-Yu; Hou, Gui-Hua; Guan, Rong-Feng; Zhang, Jun-Hao

2018-06-01

The fast development of solid-liquid phase change materials calls for nanomaterials with large specific surface area for rapid heat transfer and encapsulation of phase change materials to prevent potential leakage. Here we report a combined miniemulsion/emulsion polymerization method to prepare poly(styrene-co-acrylic acid)-encapsulated paraffin (paraffin@P(St-co-AA)) nanocapsules. The method could suppress the shortcomings of common miniemulsion polymerization (such as evaporation of monomer and decomposition of initiator during ultrasonication). The paraffin@P(St-co-AA) nanocapsules are uniform in size and the polymer shell can be controlled by the weight ratio of St to paraffin. The phase change behavior of the nanocapsules is similar to that of pure paraffin. We believe our method can also be utilized to synthesize other core-shell phase change materials.

ERK reinforces actin polymerization to power persistent edge protrusion during motility.

PubMed

Mendoza, Michelle C; Vilela, Marco; Juarez, Jesus E; Blenis, John; Danuser, Gaudenz

2015-05-19

Cells move through perpetual protrusion and retraction cycles at the leading edge. These cycles are coordinated with substrate adhesion and retraction of the cell rear. We tracked spatial and temporal fluctuations in the molecular activities of individual moving cells to elucidate how extracellular signal-regulated kinase (ERK) signaling controlled the dynamics of protrusion and retraction cycles. ERK is activated by many cell surface receptors, and we found that ERK signaling specifically reinforced cellular protrusions so that they translated into rapid, sustained forward motion of the leading edge. Using quantitative fluorescent speckle microscopy and cross-correlation analysis, we showed that ERK controlled the rate and timing of actin polymerization by promoting the recruitment of the actin nucleator Arp2/3 to the leading edge. These findings support a model in which surges in ERK activity induced by extracellular cues enhance Arp2/3-mediated actin polymerization to generate protrusion power phases with enough force to counteract increasing membrane tension and to promote sustained motility. Copyright © 2015, American Association for the Advancement of Science.

ERK reinforces actin polymerization to power persistent edge protrusion during motility

PubMed Central

Mendoza, Michelle C.; Vilela, Marco; Juarez, Jesus E.; Blenis, John; Danuser, Gaudenz

2016-01-01

Cells move through perpetual protrusion and retraction cycles at the leading edge. These cycles are coordinated with substrate adhesion and retraction of the cell rear. Here, we tracked spatial and temporal fluctuations in the molecular activities of individual moving cells to elucidate how extracellular regulated kinase (ERK) signaling controlled the dynamics of protrusion and retraction cycles. ERK is activated by many cell-surface receptors and we found that ERK signaling specifically reinforced cellular protrusions so that they translated into rapid, sustained forward motion of the leading edge. Using quantitative fluorescent speckle microscopy (qFSM) and cross-correlation analysis, we showed that ERK controlled the rate and timing of actin polymerization by promoting the recruitment of the actin nucleator Arp2/3 to the leading edge. Arp2/3 activity generates branched actin networks that can produce pushing force. These findings support a model in which surges in ERK activity induced by extracellular cues enhance Arp2/3-mediated actin polymerization to generate protrusion power phases with enough force to counteract increasing membrane tension and to promote sustained motility. PMID:25990957

Gas flow-field induced director alignment in polymer dispersed liquid crystal microdroplets deposited on a glass substrate

NASA Technical Reports Server (NTRS)

Parmar, D. S.; Singh, J. J.

1993-01-01

Polymer dispersed liquid crystal thin films have been deposited on glass substrates by the processes of polymerization and solvent evaporation induced phase separation. The electron and the optical polarization microscopies of the films reveal that PDLC microdroplets formed during the process of phase separation near the top surface of the film remain exposed and respond to shear stress due to air or gas flow on the surface. Optical response of the film to an air flow-induced shear stress input on the free surface has been measured. Director orientation in the droplets changes with the applied shear stress leading to time varying transmitted light intensity. Director dynamics of the droplet for an applied step shear stress has been discussed from free energy considerations. Results on the measurement of light transmission as a function of the gas flow parameter unambiguously demonstrate the potential of these systems for use as boundary layer and gas flow sensors.

Self-Supporting, Hydrophobic, Ionic Liquid-Based Reference Electrodes Prepared by Polymerization-Induced Microphase Separation.

PubMed

Chopade, Sujay A; Anderson, Evan L; Schmidt, Peter W; Lodge, Timothy P; Hillmyer, Marc A; Bühlmann, Philippe

2017-10-27

Interfaces of ionic liquids and aqueous solutions exhibit stable electrical potentials over a wide range of aqueous electrolyte concentrations. This makes ionic liquids suitable as bridge materials that separate in electroanalytical measurements the reference electrode from samples with low and/or unknown ionic strengths. However, methods for the preparation of ionic liquid-based reference electrodes have not been explored widely. We have designed a convenient and reliable synthesis of ionic liquid-based reference electrodes by polymerization-induced microphase separation. This technique allows for a facile, single-pot synthesis of ready-to-use reference electrodes that incorporate ion conducting nanochannels filled with either 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-dodecyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide as ionic liquid, supported by a mechanically robust cross-linked polystyrene phase. This synthesis procedure allows for the straightforward design of various reference electrode geometries. These reference electrodes exhibit a low resistance as well as good reference potential stability and reproducibility when immersed into aqueous solutions varying from deionized, purified water to 100 mM KCl, while requiring no correction for liquid junction potentials.

Stimulus-Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self-assembly (PISA).

PubMed

Pei, Yiwen; Lowe, Andrew B; Roth, Peter J

2017-01-01

Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations, suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism ("shape-shifting"), typically between micellar, worm-like, and vesicular phases (order-order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behavior is rationalised in terms of increased solvation of reversibly ionized groups. Temperature-triggered order-order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behavior that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this "smart" nanoparticle behavior are reviewed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymeric Helical Microactuators: Achieving High Speed and High Extension.

NASA Astrophysics Data System (ADS)

Kim, Yongjin; Crosby, Alfred

We proposed novel concepts of actuation mechanism and fabrication method to induce fast and highly extensional motion in polymeric actuators. Exceptionally high extensional strain over 1400% was realized by the geometric transformation from a helix to a stretched ribbon in a responsive and reversible manner. As a model system, sub-micron sized helices were fabricated from a self-assembled, UV-cured, thermo-responsive polymer. By controlling the size and the geometrical asymmetries in the system, a combined effect of surface tension and differential volumetric strain during the transition between swollen-deswollen state induced by phase transition of the material was successfully utilized to generate torsional stresses in the system. For the full understanding of the results, a finite element analysis and measurements on the poroelastic properties of the material were conducted as well as a demonstration on macroscopic system made with PDMS. Finally, remaining questions on the chirality of helices were presented. This material is based upon work supported by, or in part by, the U. S. Army Research Laboratory and the U. S. Army Research Office under contract/Grant Number W911NF-15-1-0358.

Polymeric compositions incorporating polyethylene glycol as a phase change material

DOEpatents

Salyer, Ival O.; Griffen, Charles W.

1989-01-01

A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the composition is useful in making molded and/or coated materials such as flooring, tiles, wall panels and the like; paints containing polyethylene glycols or end-capped polyethylene glycols are also disclosed.

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

Sun, Jiangman; Dong, Xiao; Wang, Yajie

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Moreover, following this route produces a pure cis-isomer and more surprisingly, predictsmore » that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure.« less

THE RADIATION-INDUCED POLYMERIZATION OF ISOBUTENE: A LIQUID PHASE IONIC REACTION

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

Collinson, E.; Dainton, F.S.; Gillis, H.A.

1959-06-01

New evidence is presented in support of the suggestion that the gamma - ray-induced polymerization of liquid isobutene at -78 deg C proceeds solely by a cationic mechanism. Attempts to polymerize isobutene at -78 deg C with free radicals from the photolysis of diacetyl, benzoin and benzil were unsuccessful but the benzil solution irradiated with ultraviolet light at 77 deg K was shown by electron spin resonance measurements to give rise to radicals from the isobutene. Isobutene irradiated in the pure state at a gamma -ray dose rate of 7 x 10/sup 17/ e.v. ml/sup -1/ min/sup -1/ polymerized withmore » G(-C/sub 4/H/sub 8/) = 3.0 plus or minus 1.7 x 10/sup 2/. Solutions of FeCl/sub 3/, DPPH, benzoquinone and iodine in isobutene were also irradiated with gamma -rays. Of these solutes, only benzoquinone reduced the polymerization rate to zero, and DPPH had no significant effect. The effects of FeCl/sub 3/ and I/2 on the polymerization were complicated by other factors. The measured yields of conversion of the solutes after irradiation were G(-DPPH) =3.7 plus or minus 0.2, G(Fe(II)) = 3.0 plus or minus 0.5 and G(-Q) = 1.5 plus or minus 0.2. The electron spin resonance spectrum of isobutene irradiated with gamma -rays at 77 deg K showed the presence of H atoms which disappeared rapidly, and a more stable radical, the spectrum of which consisted of 6 peaks having an over-all spacing of 158 gauss at the operating frequency of 9400 Mc sec./sup -1/. The same six peak pattern was obtained from cyclopropane irradiated with gamma rays at 77 deg K and from a solution of benzil in isoDutene irradiated with ultraviolet light at 77 deg K. It is concluded that the radical responsible for this spectrum is either the cyclopropyl radical or the methyl substituted allyl radical, the latter being the less likely. The most likely initiating ion is considered to be (CH/sub 3/)/sub 3/C/sup +/, and a mechanism consistent with the available data is proposed. (auth)« less

In Situ Monitoring of RAFT Polymerization by Tetraphenylethylene-Containing Agents with Aggregation-Induced Emission Characteristics.

PubMed

Liu, Shunjie; Cheng, Yanhua; Zhang, Haoke; Qiu, Zijie; Kwok, Ryan T K; Lam, Jacky W Y; Tang, Ben Zhong

2018-05-22

A facile and efficient approach is demonstrated to visualize the polymerization in situ. A group of tetraphenylethylene (TPE)-containing dithiocarbamates were synthesized and screened as agents for reversible addition fragmentation chain transfer (RAFT) polymerizations. The spatial-temporal control characteristics of photochemistry enabled the RAFT polymerizations to be ON and OFF on demand under alternating visible light irradiation. The emission of TPE is sensitive to the local viscosity change owing to its aggregation-induced emission characteristic. Quantitative information could be easily acquired by the naked eye without destroying the reaction system. Furthermore, the versatility of such a technique was well demonstrated by 12 different polymerization systems. The present approach thus demonstrated a powerful platform for understanding the controlled living radical polymerization process. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Eutectic phase in water-ice: a self-assembled environment conducive to metal-catalyzed non-enzymatic RNA polymerization.

PubMed

Monnard, Pierre-Alain; Ziock, Hans

2008-08-01

Information and catalytic polymers play an essential role in contemporary cellular life, and their emergence must have been crucial during the complex processes that led to the assembly of the first living systems. Polymerization reactions producing these molecules would have had to occur in aqueous medium, which is known to disfavor such reactions. Thus, it was proposed early on that these polymerizations had to be supported by particular environments, such as mineral surfaces and eutectic phases in water-ice, which would have led to the concentration of the monomers out of the bulk aqueous medium and their condensation. This review presents the work conducted to understand how the eutectic phases in water-ice might have promoted RNA polymerization, thereby presumably contributing to the emergence of the ancient information and catalytic system envisioned by the 'RNA-World' hypothesis.

Radiation-induced controlled polymerization of acrylic acid by RAFT and RAFT-MADIX methods in protic solvents

NASA Astrophysics Data System (ADS)

Sütekin, S. Duygu; Güven, Olgun

2018-01-01

The kinetic investigation of one-pot synthesis of poly(acrylic acid) (PAA) prepared via gamma radiation induced controlled polymerization was reported. PAA homopolymers were prepared by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization in the presence of trithiocarbonate-based chain transfer agent (CTA) 2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) and also by Reversible Addition-Fragmentation/Macromolecular Design by Inter-change of Xanthates (RAFT/MADIX) polymerization in the presence of a xanthate based CTA O-ethyl-S-(1-methoxycarbonyl) ethyl dithiocarbonate (RA1). The polymerizations were performed at room temperature by the virtue of ionizing radiation. Protic solvents were used for the RAFT polymerization of AA considering environmental profits. The linear first-order kinetic plot, close control of molecular weight by the monomer/CTA molar ratio supported that the polymerization proceeds in a living fashion. The linear increase in molecular weight with conversion monitored by Size Exclusion Chromatography (SEC) is another proof of controlling of polymerization. [Monomer]/[RAFT] ratio and conversion was controlled to obtain PAA in the molecular weight range of 6900-35,800 with narrow molecular weight distributions. Reaction kinetics and effect of the amount of RAFT agent were investigated in detail. Between two different types of CTA, trithiocarbonate based DDMAT was found to be more efficient in terms of low dispersity (Đ) and linear first-order kinetic behavior for the radiation induced controlled synthesis of PAA homopolymers.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, LeRoy Louis; Nichols, Monte Carl; Wheeler, David Roger; Loy, Douglas Anson

1997-01-01

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

1997-09-16

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

The autowave modes of solid phase polymerization of metal-containing monomers in two- and three-dimensional fiberglass-filled matrices

NASA Astrophysics Data System (ADS)

Barelko, V. V.; Pomogailo, A. D.; Dzhardimalieva, G. I.; Evstratova, S. I.; Rozenberg, A. S.; Uflyand, I. E.

1999-06-01

The phenomenon of autowave (frontal) solid phase polymerization of metal-containing monomers based on metal-acrylamide complexes is considered. The comparison of the features of autowave processes realized in both the single-component matrices of the monomer and the matrices filled by the fiberglass materials is performed. The unstable regimes of the polymerization wave as well as the conditions for the stabilization of the flat front in the filled matrices are described. The peculiarities of the frontal regimes in the three- and two-dimensional media are studied. Some possibilities for using of autowave polymerization in the fabrication of the polymer-fiberglass composites and composition prepregs are discussed.

Modeling normal shock velocity curvature relations for heterogeneous explosives

NASA Astrophysics Data System (ADS)

Yoo, Choong-Shik; Tomasino, Dane; Smith, Jesse; Kim, Minseob

2017-01-01

Many simple molecules such as N2 and CO2 have the potential to form extended "polymeric" solids under extreme conditions, which can store a large sum of chemical energy in its three-dimensional network structures made of strong covalent bonds. Diatomic nitrogen is particularly of interest because of the uniquely large energy difference between the single (160 kJ/mol) and triple (950 kJ/mol) bonds. As such, the transformation of singly bonded polymeric nitrogen back to triply bonded diatomic nitrogen molecules can release large energy ( 33 kJ/cm3 - three times that of HMX) without any negative environmental impact. Therefore, the goal of the present study has been to investigate the transformation of nitrogen and nitrogen-rich compounds to new singly bonded nitrogen-rich solids at high pressures and temperatures, using heated diamond anvil cells, Raman spectroscopy, and third-generation synchrotron x-ray diffraction. Recently, we have found a new form of singly bonded layered polymeric nitrogen (LP-N), synthesized in the stability pressure-temperature field higher than that of cg-N. This new phase is characterized by a 2D layered structure similar to the predicted Pba2 and two colossal Raman bands, arising from two groups of highly polarized nitrogen atoms. This result also provides a new constraint for the nitrogen phase diagram, highlighting an unusual symmetry lowering 3D cg- to 2D LP-N transition and thereby the enhanced electrostatic contribution to the stabilization of this densely packed LP-N. In this paper, we will review this finding of LP-N, update the phase diagram of nitrogen, and offer a chemistry view of pressure-induced transformations in dense molecular solids.

Ground state structure of high-energy-density polymeric carbon monoxide

NASA Astrophysics Data System (ADS)

Xia, Kang; Sun, Jian; Pickard, Chris J.; Klug, Dennis D.; Needs, Richard J.

2017-04-01

Crystal structure prediction methods and first-principles calculations have been used to explore low-energy structures of carbon monoxide (CO). Contrary to the standard wisdom, the most stable structure of CO at ambient pressure was found to be a polymeric structure of P n a 21 symmetry rather than a molecular solid. This phase is formed from six-membered (four carbon + two oxygen) rings connected by C=C double bonds with two double-bonded oxygen atoms attached to each ring. Interestingly, the polymeric P n a 21 phase of CO has a much higher energy density than trinitrotoluene (TNT). On compression to about 7 GPa, P n a 21 is found to transform into another chainlike phase of C c symmetry which has similar ring units to P n a 21 . On compression to 12 GPa, it is energetically favorable for CO to polymerize into a purely single bonded C m c a phase, which is stable over a wide pressure range and transforms into the previously known C m c m phase at around 100 GPa. Thermodynamic stability of these structures was verified using calculations with different density functionals, including hybrid and van der Waals corrected functionals.

Preparation of l-phenylalanine-imprinted solid-phase extraction sorbent by Pickering emulsion polymerization and the selective enrichment of l-phenylalanine from human urine.

PubMed

Li, Ji; Hu, Xiaoling; Guan, Ping; Zhang, Xiaoyan; Qian, Liwei; Zhang, Nan; Du, Chunbao; Song, Renyuan

2016-05-01

A novel l-phenylalanine molecularly imprinted solid-phase extraction sorbent was synthesized by the combination of Pickering emulsion polymerization and ion-pair dummy template imprinting. Compared to other polymerization methods, the molecularly imprinted polymers thus prepared exhibit a high specific surface, large pore diameter, and appropriate particle size. The key parameters for solid-phase extraction were optimized, and the result indicated that the molecularly imprinted polymer thus prepared exhibits a good recovery of 98.9% for l-phenylalanine. Under the optimized conditions of the procedure, an analytical method for l-phenylalanine was well established. By comparing the performance of the molecularly imprinted polymer and a commercial reverse-phase silica gel, the obtained molecularly imprinted polymer as an solid-phase extraction sorbent is more suitable, exhibiting high precision (relative standard deviation 3.2%, n = 4) and a low limit of detection (60.0 ± 1.9 nmol·L(-1) ) for the isolation of l-phenylalanine. Based on these results, the combination of the Pickering emulsion polymerization and ion-pair dummy template imprinting is effective for preparing selective solid-phase extraction sorbents for the separation of amino acids and organic acids from complex biological samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid coatings deposited from liquid methyl methacrylate via Plasma Polymerization

NASA Astrophysics Data System (ADS)

Wurlitzer, Lisa; Maus-Friedrichs, Wolfgang; Dahle, Sebastian

2016-09-01

The polymerization of methyl methacrylate via plasma discharges is well known today. Usually, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit polymer coatings. Solid coatings are formed out of the liquid phase from methyl methacrylate via dielectric barrier discharge. The formation of the coating proceeds in the gas and the liquid phase. To learn more about the reactions in the two phases, the coatings from MMA monomer will be compared to those from MMA resin. Finally, attenuated total reflection infrared spectroscopy, confocal laser scanning microscopy and X-ray photoelectron spectroscopy are employed to characterize the solid coatings. In conclusion, the plasma enhanced chemical solution deposition is compared to the classical thermal polymerization of MMA.

Modulation of interferon-γ synthesis by the effects of lignin-like enzymatically polymerized polyphenols on antigen-presenting cell activation and the subsequent cell-to-cell interactions.

PubMed

Yamanaka, Daisuke; Motoi, Masuro; Ishibashi, Ken-ichi; Miura, Noriko N; Adachi, Yoshiyuki; Ohno, Naohito

2013-12-15

Lignin-like polymerized polyphenols strongly activate lymphocytes and induce cytokine synthesis. We aimed to characterise the mechanisms of action of polymerized polyphenols on immunomodulating functions. We compared the reactivity of leukocytes from various organs to that of polymerized polyphenols. Splenocytes and resident peritoneal cavity cells (PCCs) responded to polymerized polyphenols and released several cytokines, whereas thymocytes and bone-marrow cells showed no response. Next, we eliminated antigen-presenting cells (APCs) from splenocytes to study their involvement in cytokine synthesis. We found that APC-negative splenocytes showed significantly reduced cytokine production induced by polymerized polyphenols. Additionally, adequate interferon-γ (IFN-γ) induction by polymerized polyphenols was mediated by the coexistence of APCs and T cells because the addition of T cells to PCCs increased IFN-γ production. Furthermore, inhibition of the T cell-APC interaction using neutralising antibodies significantly decreased cytokine production. Thus, cytokine induction by polymerized polyphenols was mediated by the interaction between APCs and T cells. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dynamics of polymerization induced phase separation in reactive polymer blends

NASA Astrophysics Data System (ADS)

Lee, Jaehyung

Mechanisms and dynamics of phase decomposition following polymerization induced phase separation (PIPS) of reactive polymer blends have been investigated experimentally and theoretically. The phenomenon of PIPS is a non-equilibrium and non-linear dynamic process. The mechanism of PIPS has been thought to be a nucleation and growth (NG) type originally, however, newer results indicate spinodal decomposition (SD). In PIPS, the coexistence curve generally passes through the reaction temperature at off-critical compositions, thus phase separation has to be initiated first in the metastable region where nucleation occurs. When the system farther drifts from the metastable to unstable region, the NG structure transforms to the SD bicontinuous morphology. The crossover behavior of PIPS may be called nucleation initiated spinodal decomposition (NISD). The formation of newer domains between the existing ones is responsible for the early stage of PIPS. Since PIPS is non- equilibrium kinetic process, it would not be surprising to discern either or both structures. The phase separation dynamics of DGEBA/CTBN mixtures having various kinds of curing agents from low reactivity to high reactivity and various amount of curing agents were examined at various reaction temperatures. The phase separation behavior was monitored by a quantity of scattered light intensity experimentally and by a quantity of collective structure factor numerically. Prior to the study of phase separation dynamics, a preliminary investigation on the isothermal cure behavior of the mixtures were executed in order to determine reaction kinetics parameters. The cure behavior followed the overall second order reaction kinetics. Next, based on the knowledge obtained from the phase separation dynamics study of DGEBA/CTBN mixtures, the phase separation dynamics of various composition of DGEBA/R45EPI mixtures having MDA as a curing agent were investigated. The phase separation behavior was quite dependent upon the composition variation. R45EPI itself can react with itself or with DGEBA without curing, therefore three-component system was considered in this mixture. For the numerical studies of this three- component mixture, a system that is composed of a reactive component-1 that is miscible with its growing molecules and another reactive component-2 that is not miscible with its growing molecules was considered with crosslinking reaction kinetics of the each component.

Pressure-induced stable BeN4 as a high-energy density material

NASA Astrophysics Data System (ADS)

Zhang, Shoutao; Zhao, Ziyuan; Liu, Lulu; Yang, Guochun

2017-10-01

Polynitrogens are the ideal rocket fuels or propellants. Due to strong triple N≡N bond in N2, the direct polymerization of nitrogen is rather difficult (i.e. extreme high temperature and high pressure). However, the use of nitrides as precursors or the reaction of N2 with other elements has been proved to be an effective way to obtain polynitrogens. Here, with assistance of the advanced first-principles swarm-intelligence structure searches, we found that P 1 bar -BeN4, containing infinite zigzag-like polymeric nitrogen chains, can be synthesized by compressing the mixture of Be3N2 and N2 at 25.4 GPa, which is greatly lower than 110 GPa for synthesizing cubic gauche nitrogen and other polynitrogen compounds (e.g. bulk CNO at 52 GPa and SN4 at 49 GPa). Its structural stability can be attributed to the coexistence of ionic Be-N and covalent N-N bonds. Intriguingly, this phase has high kinetic stability and remains metastable at ambient pressure. The exceptional properties, including high energy density (3.60 kJ g-1), high nitrogen content (86.1%), high dynamical stability, and low polymerization pressure, make P 1 bar -structured BeN4 a promising high energy material. Infinite nitrogen chains in P 1 bar -BeN4 transform to N10 rings network in P21/c phase at 115.1 GPa. P 1 bar -BeN4 is metallic, while P21/c-BeN4 is an insulator.

Influence of conformational changes on spin crossover properties and superstructure formation in 2D coordination polymers [Fe(hbtz)2(RCN)2](ClO4)2.

PubMed

Książek, Maria; Kusz, Joachim; Białońska, Agata; Bronisz, Robert; Weselski, Marek

2015-11-14

2D structurally related iron(ii) coordination networks {[Fe(hbtz)2(RCN)2](ClO4)2}∞ featuring, besides tetrazol-2-yl rings in the first coordination sphere, also axially coordinated propionitrile or allyl cyanide molecules (R = C3H5-, 1; R = C2H5-, 2) were synthesized. Thermally induced spin crossover (SCO) in 1 takes place in two poorly resolved stages (T(1)1/2(↓) = T(1)1/2(↑) = 198 K, T(2)1/2(↓) = 170 K, T(2)1/2(↑) = 171 K) whereas in 2 complete and relatively gradual one step SCO (T1/2(↓) = T1/2(↑) = 160 K) occurs. Diversification of the SCO properties of the complexes originates from the ability of coordinated allyl cyanide in 1 to undergo conformational alterations, which is not observed for propionitrile molecules in 2. SCO in 1 is accompanied by a non-monotonic change of the contribution of allyl cyanide conformers which is related to reconstruction of the network of intermolecular contacts established between polymeric layers. The coordination network 1 exhibits extraordinary elasticity and in the second stage SCO, accompanied by conformational changes of allyl cyanide, triggers a crystallographic phase transition which leads to the formation of a superstructure. What is important, the formation of the superstructure is not caused by long range ordering of HS and LS iron(ii) ions. The structural alteration is associated with corrugation of the polymeric skeleton and disappearance of nitrile disorder. Irradiation of a single crystal of 1 at 15 K with laser light (520 nm) allowed producing a novel low temperature HS phase of 1 in which, contrary to the high temperature HS phase, disordering of anion and allyl cyanide molecules is not observed and the corrugated nature of the polymeric layer, characteristic of the LS phase, is preserved.

Reverse-mode thermoresponsive light attenuators produced by optical anisotropic composites of nematic liquid crystals and reactive mesogens

NASA Astrophysics Data System (ADS)

Kakiuchida, Hiroshi; Ogiwara, Akifumi

2018-04-01

Polymer network liquid crystals (PNLCs) whose optical transmittance state switches between transparence at low temperatures and haze at high temperatures were fabricated from mixtures of nematic liquid crystals (LCs) and reactive mesogens (RMs). This PNLC structure is simple but effective, namely, consists of micro-scale domains of orientation-ordered LCs and anisotropically polymerized RMs. The domains form through photopolymerization induced phase separation with inhomogeneous irradiation projected by laser speckling techniques. This irradiation method enables you to control the size and shape of phase-separation domains, and these PNLCs can be applied to novel thermoresponsive optical devices; optical isolators, thermometric sheets, and smart windows.

Piezochromism and structural and electronic properties of benz[a]anthracene under pressure

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

Cai, Weizhao; Zhang, Rong; Yao, Yansun

2017-01-31

We report a combined experimental and theoretical study of the high pressure behavior of a herringbone-type hydrocarbon benz[a]anthracene (BaA) using fluorescence spectroscopy, X-ray diffraction, optical absorption, photoconductivity measurements, and first-principles density functional theory (DFT) calculations. The ambient-pressure molecular solid phase of BaA was found to be stable up to ~15.0 GPa. Increasing the external pressure within this region would induce a reversible piezochromic colour change in the sample, from yellow-green to light brown. The reversibility of the colour change was confirmed by both optical observations and fluorescence measurements. Further compression beyond 15 GPa leads to polymerization of the sample andmore » formation of an amorphous hydrogenated carbon. The low pressure crystalline phase is not recoverable when the sample is decompressed from pressure above 15 GPa. DFT investigation of the structures at zero temperature suggests that the formation of a crystalline polymeric phase can take place between 30 and 117 GPa, however the kinetic barriers hinder the process at low pressure regions. The phase transition is therefore suggested to proceed along a gradual transition path to an amorphous phase at a lower reaction threshold, activated by finite temperature effects. Optical absorption measurements reveal that the band gap of BaA decreases at high pressure, from 2.4 eV at 0.5 GPa to 1.0 eV at 50.6 GPa. The DFT calculations further suggest that the band gap of BaA in the molecular phase could reduce to ~0.1 eV at 117 GPa. Photoconductivity measurements show a continuous increase of photocurrent in the molecular phase region, which most likely originated from the increase of carrier mobility under pressure.« less

LC-MS/MS analysis of uncommon paracetamol metabolites derived through in vitro polymerization and nitration reactions in liquid nitrogen.

PubMed

Trettin, Arne; Jordan, Jens; Tsikas, Dimitrios

2014-09-01

Paracetamol (acetaminophen, APAP) is a commonly used analgesic drug. Known paracetamol metabolites include the glucuronide, sulfate and mercapturate. N-Acetyl-benzoquinonimine (NAPQI) is considered the toxic intermediate metabolite of paracetamol. In vitro and in vivo studies indicate that paracetamol is also metabolized to additional poorly characterized metabolites. For example, metabolomic studies in urine samples of APAP-treated mice revealed metabolites such as APAP-sulfate-APAP and APAP-S-S-APAP in addition to the classical phase II metabolites. Here, we report on the development and application of LC-MS and LC-MS/MS approaches to study reactions of unlabelled and (2)H-labelled APAP with unlabelled and (15)N-labelled nitrite in aqueous phosphate buffers (pH 7.4) upon their immersion into liquid nitrogen (-196°C). In mechanistic studies, these reactions were also studied in aqueous buffer prepared in (18)O-labelled water. LC-MS and LC-MS/MS analyses were performed on a reverse-phase material (C18) using gradient elution (2mM ammonium acetate/acetonitrile), in positive and negative electrospray mode. We identified a series of APAP metabolites including di-, tri- and tetra-APAP, mono- and di-nitro-APAP and nitric ester of di-APAP. Our study indicates that nitrite induces oxidation, i.e., polymerization and nitration of APAP, when buffered APAP/nitrite solutions are immersed into liquid nitrogen. These reactions are specific for nitrite with respect to nitrate and do not proceed via intermediate formation of NAPQI. Potassium ions and physiological saline but not thiols inhibit nitrite- and shock-freeze-induced reactions of paracetamol. The underlying mechanism likely involves in situ formation of NO2 radicals from nitrite secondary to profound pH reduction (down to pH 1) and disproportionation. Polymeric paracetamol species can be analyzed as pentafluorobenzyl derivatives by LC-MS but not by GC-MS. Copyright © 2013 Elsevier B.V. All rights reserved.

Aqueous dispersion polymerization: a new paradigm for in situ block copolymer self-assembly in concentrated solution.

PubMed

Sugihara, Shinji; Blanazs, Adam; Armes, Steven P; Ryan, Anthony J; Lewis, Andrew L

2011-10-05

Reversible addition-fragmentation chain transfer polymerization has been utilized to polymerize 2-hydroxypropyl methacrylate (HPMA) using a water-soluble macromolecular chain transfer agent based on poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC). A detailed phase diagram has been elucidated for this aqueous dispersion polymerization formulation that reliably predicts the precise block compositions associated with well-defined particle morphologies (i.e., pure phases). Unlike the ad hoc approaches described in the literature, this strategy enables the facile, efficient, and reproducible preparation of diblock copolymer spheres, worms, or vesicles directly in concentrated aqueous solution. Chain extension of the highly hydrated zwitterionic PMPC block with HPMA in water at 70 °C produces a hydrophobic poly(2-hydroxypropyl methacrylate) (PHPMA) block, which drives in situ self-assembly to form well-defined diblock copolymer spheres, worms, or vesicles. The final particle morphology obtained at full monomer conversion is dictated by (i) the target degree of polymerization of the PHPMA block and (ii) the total solids concentration at which the HPMA polymerization is conducted. Moreover, if the targeted diblock copolymer composition corresponds to vesicle phase space at full monomer conversion, the in situ particle morphology evolves from spheres to worms to vesicles during the in situ polymerization of HPMA. In the case of PMPC(25)-PHPMA(400) particles, this systematic approach allows the direct, reproducible, and highly efficient preparation of either block copolymer vesicles at up to 25% solids or well-defined worms at 16-25% solids in aqueous solution.

Application of mercapto-silica polymerized high internal phase emulsions for the solid-phase extraction and preconcentration of trace lead(II).

PubMed

Su, Rihui; Ruan, Guihua; Chen, Zhengyi; Du, Fuyou; Li, Jianping

2015-12-01

A new class of solid-phase extraction column prepared with grafted mercapto-silica polymerized high internal phase emulsion particles was used for the preconcentration of trace lead. First, mercapto-silica polymerized high internal phase emulsion particles were synthesized by using high internal phase emulsion polymerization and carefully assembled in a polyethylene syringe column. The influences of various parameters including adsorption pH value, adsorption and desorption solvents, flow rate of the adsorption and desorption procedure were optimized, respectively, and the suitable uploading sample volumes, adsorption capacity, and reusability of solid phase extraction column were also investigated. Under the optimum conditions, Pb(2+) could be preconcentrated quantitatively over a wide pH range (2.0-5.0). In the presence of foreign ions, such as Na(+) , K(+) , Ca(2+) , Zn(2+) , Mg(2+) , Cu(2+) , Fe(2+) , Cd(2+) , Cl(-) and NO3 (-) , Pb(2+) could be recovered successfully. The prepared solid-phase extraction column performed with high stability and desirable durability, which allowed more than 100 replicate extractions without measurable changes of performance. The feasibility of the developed method was further validated by the extraction of Pb(2+) in rice samples. At three spiked levels of 40.0, 200 and 800 μg/kg, the average recoveries for Pb(2+) in rice samples ranged from 87.3 to 105.2%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Equilibrium polymerization on the equivalent-neighbor lattice

NASA Technical Reports Server (NTRS)

Kaufman, Miron

1989-01-01

The equilibrium polymerization problem is solved exactly on the equivalent-neighbor lattice. The Flory-Huggins (Flory, 1986) entropy of mixing is exact for this lattice. The discrete version of the n-vector model is verified when n approaches 0 is equivalent to the equal reactivity polymerization process in the whole parameter space, including the polymerized phase. The polymerization processes for polymers satisfying the Schulz (1939) distribution exhibit nonuniversal critical behavior. A close analogy is found between the polymerization problem of index the Schulz r and the Bose-Einstein ideal gas in d = -2r dimensions, with the critical polymerization corresponding to the Bose-Einstein condensation.

The autowave modes of solid phase polymerization of metal-containing monomers in two- and three-dimensional fiberglass-filled matrices.

PubMed

Barelko, V. V.; Pomogailo, A. D.; Dzhardimalieva, G. I.; Evstratova, S. I.; Rozenberg, A. S.; Uflyand, I. E.

1999-06-01

The phenomenon of autowave (frontal) solid phase polymerization of metal-containing monomers based on metal-acrylamide complexes is considered. The comparison of the features of autowave processes realized in both the single-component matrices of the monomer and the matrices filled by the fiberglass materials is performed. The unstable regimes of the polymerization wave as well as the conditions for the stabilization of the flat front in the filled matrices are described. The peculiarities of the frontal regimes in the three- and two-dimensional media are studied. Some possibilities for using of autowave polymerization in the fabrication of the polymer-fiberglass composites and composition prepregs are discussed. (c) 1999 American Institute of Physics.

Quaternary ammonium silane-functionalized, methacrylate resin composition with antimicrobial activities and self-repair potential

PubMed Central

Gong, Shi-qiang; Niu, Li-na; Kemp, Lisa K.; Yiu, Cynthia K.Y.; Ryou, Heonjune; Qi, Yi-pin; Blizzard, John D.; Nikonov, Sergey; Brackett, Martha G.; Messer, Regina L.W.; Wu, Christine D.; Mao, Jing; Brister, L. Bryan; Rueggeberg, Frederick A.; Arola, Dwayne D.; Pashley, David H.; Tay, Franklin R.

2012-01-01

Design of antimicrobial polymers for enhancing healthcare issues and minimizing environmental problems is an important endeavor with both fundamental and practical implications. Quaternary ammonium silane-functionalized methacrylate (QAMS) represents an example of antimicrobial macromonomers synthesized by a sol-gel chemical route; these compounds possess flexible Si-O-Si bonds. In present work, a partially-hydrolyzed QAMS copolymerized with bis-GMA is introduced. This methacrylate resin was shown to possess desirable mechanical properties with both a high degree of conversion and minimal polymerization shrinkage. Kill-on-contact microbiocidal activities of this resin were demonstrated using single-species biofilms of Streptococcus mutans (ATCC 36558), Actinomyces naeslundii (ATCC 12104) and Candida albicans (ATCC 90028). Improved mechanical properties after hydration provided the proof-of-concept that QAMS-incorporated resin exhibits self-repair potential via water-induced condensation of organic modified silicate (ormosil) phases within the polymerized resin matrix. PMID:22659173

Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

NASA Technical Reports Server (NTRS)

Parmar, D. S.; Singh, J. J.

1993-01-01

Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

Evidence against impaired brain microtubule protein polymerization at high glucose concentrations or during diabetes mellitus.

PubMed

Eaker, E Y; Angelastro, J M; Purich, D L; Sninsky, C A

1991-06-01

Previous studies suggest that brain microtubule protein exposed to high glucose levels or isolated from diabetic rats can become glucosylated and that this impairs GTP-induced microtubule polymerization. We set out to extend that investigation to define the mechanistic basis for inhibition of microtubule assembly during diabetes or on incubation at high glucose levels. Rat and bovine brain microtubule protein was purified by cycles of polymerization/depolymerization. When microtubules were incubated for 1 h in either buffer or buffer containing glucose (up to 165 mM), there was no difference in polymerization, a finding contrary to the earlier study. Other rats were injected with vehicle or streptozotocin (90 mg/kg) to induce diabetes as evidenced by serum glucose in excess of 300 mg%, and at 4 weeks, brain microtubule protein was isolated by the polymerization cycling method. Again, there was no difference in the amount or purity of isolated microtubule protein between control or diabetic rats. We also observed no increase in microtubule glucosylation, and GTP-induced polymerization in vitro was indistinguishable for protein derived from brains of normal rats and rats with diabetes as measured by turbidity or electron microscopy. Our results suggest that in vitro incubation with glucose or in vivo elevation of glucose during diabetes fails to impair microtubule polymerization, pointing to other mechanisms for the neuropathy associated with diabetes.

Ac102 Participates in Nuclear Actin Polymerization by Modulating BV/ODV-C42 Ubiquitination during Autographa californica Multiple Nucleopolyhedrovirus Infection.

PubMed

Zhang, Yongli; Hu, Xue; Mu, Jingfang; Hu, Yangyang; Zhou, Yuan; Zhao, He; Wu, Chunchen; Pei, Rongjuan; Chen, Jizheng; Chen, Xinwen; Wang, Yun

2018-06-15

As a virus-encoded actin nucleation promoting factor (NPF), P78/83 induces actin polymerization to assist in Autographa californica multiple nucleopolyhedrovirus (AcMNPV) propagation. According to our previous study, although P78/83 actively undergoes ubiquitin-independent proteasomal degradation, AcMNPV encodes budded virus/occlusion derived virus (BV/ODV)-C42 (C42), which allows P78/83 to function as a stable NPF by inhibiting its degradation during viral infection. However, whether there are other viral proteins involved in regulating P78/83-induced actin polymerization has yet to be determined. In this study, we found that Ac102, an essential viral gene product previously reported to play a key role in mediating the nuclear accumulation of actin during AcMNPV infection, is a novel regulator of P78/83-induced actin polymerization. By characterizing an ac102 knockout bacmid, we demonstrated that Ac102 participates in regulating nuclear actin polymerization as well as the morphogenesis and distribution of capsid structures in the nucleus. These regulatory effects are heavily dependent on an interaction between Ac102 and C42. Further investigation revealed that Ac102 binds to C42 to suppress K48-linked ubiquitination of C42, which decreases C42 proteasomal degradation and consequently allows P78/83 to function as a stable NPF to induce actin polymerization. Thus, Ac102 and C42 form a regulatory cascade to control viral NPF activity, representing a sophisticated mechanism for AcMNPV to orchestrate actin polymerization in both a ubiquitin-dependent and ubiquitin-independent manner. IMPORTANCE Actin is one of the most functionally important proteins in eukaryotic cells. Morphologically, actin can be found in two forms: a monomeric form called globular actin (G-actin) and a polymeric form called filamentous actin (F-actin). G-actin can polymerize to form F-actin, and nucleation promoting factor (NPF) is the initiator of this process. Many viral pathogens harness the host actin polymerization machinery to assist in virus propagation. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) induces actin polymerization in host cells. P78/83, a viral NPF, is responsible for this process. Previously, we identified that BV/ODV-C42 (C42) binds to P78/83 and protects it from degradation. In this report, we determined that another viral protein, Ac102, is involved in modulating C42 ubiquitination and, consequently, ensures P78/83 activity as an NPF to initiate actin polymerization. This regulatory cascade represents a novel mechanism by which a virus can harness the cellular actin cytoskeleton to assist in viral propagation. Copyright © 2018 American Society for Microbiology.

Diffusion-regulated phase-transfer catalysis for atom transfer radical polymerization of methyl methacrylate in an aqueous/organic biphasic system.

PubMed

Ding, Mingqiang; Jiang, Xiaowu; Peng, Jinying; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2015-03-01

A concept based on diffusion-regulated phase-transfer catalysis (DRPTC) in an aqueous-organic biphasic system with copper-mediated initiators for continuous activator regeneration is successfully developed for atom transfer radical polymerization (ICAR ATRP) (termed DRPTC-based ICAR ATRP here), using methyl methacrylate (MMA) as a model monomer, ethyl α-bromophenylacetate (EBrPA) as an initiator, and tris(2-pyridylmethyl)amine (TPMA) as a ligand. In this system, the monomer and initiating species in toluene (organic phase) and the catalyst complexes in water (aqueous phase) are simply mixed under stirring at room temperature. The trace catalyst complexes transfer into the organic phase via diffusion to trigger ICAR ATRP of MMA with ppm level catalyst content once the system is heated to the polymerization temperature (75 °C). It is found that well-defined PMMA with controlled molecular weights and narrow molecular weight distributions can be obtained easily. Furthermore, the polymerization can be conducted in the presence of limited amounts of air without using tedious degassed procedures. After cooling to room temperature, the upper organic phase is decanted and the lower aqueous phase is reused for another 10 recycling turnovers with ultra low loss of catalyst and ligand loading. At the same time, all the recycled catalyst complexes retain nearly perfect catalytic activity and controllability, indicating a facile and economical strategy for catalyst removal and recycling. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnolol Inhibits the Growth of Non-Small Cell Lung Cancer via Inhibiting Microtubule Polymerization.

PubMed

Shen, Jia; Ma, Hailin; Zhang, Tiancheng; Liu, Hui; Yu, Linghua; Li, Guosheng; Li, Huishuang; Hu, Meichun

2017-01-01

The tubulin/microtubule system, which is an integral component of the cytoskeleton, plays an essential role in mitosis. Targeting mitotic progression by disturbing microtubule dynamics is a rational strategy for cancer treatment. Microtubule polymerization assay was performed to examine the effect of Magnolol (a novel natural phenolic compound isolated from Magnolia obovata) on cellular microtubule polymerization in human non-small cell lung cancer (NSCLC) cells. Cell cycle analysis, mitotic index assay, cell proliferation assay, colony formation assay, western blotting analysis of cell cycle regulators, Annexin V-FITC/PI staining, and live/dead viability staining were carried out to investigate the Magnolol's inhibitory effect on proliferation and viability of NSCLS cells in vitro. Xenograft model of human A549 NSCLC tumor was used to determine the Magnolol's efficacy in vivo. Magnolol treatment effectively inhibited cell proliferation and colony formation of NSCLC cells. Further study proved that Magnolol induced the mitotic phase arrest and inhibited G2/M progression in a dose-dependent manner, which were mechanistically associated with expression alteration of a series of cell cycle regulators. Furthermore, Magnolol treatment disrupted the cellular microtubule organization via inhibiting the polymerization of microtubule. We also found treatment with NSCLC cells with Magnolol resulted in apoptosis activation through a p53-independent pathway, and autophgy induction via down-regulation of the Akt/mTOR pathway. Finally, Magnolol treatment significantly suppressed the NSCLC tumor growth in mouse xenograft model in vivo. These findings identify Magnolol as a promising candidate with anti-microtubule polymerization activity for NSCLC treatment. © 2017 The Author(s). Published by S. Karger AG, Basel.

Molecular Sensing by Nanoporous Crystalline Polymers

PubMed Central

Pilla, Pierluigi; Cusano, Andrea; Cutolo, Antonello; Giordano, Michele; Mensitieri, Giuseppe; Rizzo, Paola; Sanguigno, Luigi; Venditto, Vincenzo; Guerra, Gaetano

2009-01-01

Chemical sensors are generally based on the integration of suitable sensitive layers and transducing mechanisms. Although inorganic porous materials can be effective, there is significant interest in the use of polymeric materials because of their easy fabrication process, lower costs and mechanical flexibility. However, porous polymeric absorbents are generally amorphous and hence present poor molecular selectivity and undesired changes of mechanical properties as a consequence of large analyte uptake. In this contribution the structure, properties and some possible applications of sensing polymeric films based on nanoporous crystalline phases, which exhibit all identical nanopores, will be reviewed. The main advantages of crystalline nanoporous polymeric materials with respect to their amorphous counterparts are, besides a higher selectivity, the ability to maintain their physical state as well as geometry, even after large guest uptake (up to 10–15 wt%), and the possibility to control guest diffusivity by controlling the orientation of the host polymeric crystalline phase. The final section of the review also describes the ability of suitable polymeric films to act as chirality sensors, i.e., to sense and memorize the presence of non-racemic volatile organic compounds. PMID:22303150

Thiol surface functionalization via continuous phase plasma polymerization of allyl mercaptan, with subsequent maleimide-linked conjugation of collagen.

PubMed

Stynes, Gil D; Gengenbach, Thomas R; Kiroff, George K; Morrison, Wayne A; Kirkland, Mark A

2017-07-01

Thiol groups can undergo a large variety of chemical reactions and are used in solution phase to conjugate many bioactive molecules. Previous research on solid substrates with continuous phase glow discharge polymerization of thiol-containing monomers may have been compromised by oxidation. Thiol surface functionalization via glow discharge polymerization has been reported as requiring pulsing. Herein, continuous phase glow discharge polymerization of allyl mercaptan (2-propene-1-thiol) was used to generate significant densities of thiol groups on a mixed macrodiol polyurethane and tantalum. Three general classes of chemistry are used to conjugate proteins to thiol groups, with maleimide linkers being used most commonly. Here the pH specificity of maleimide reactions was used effectively to conjugate surface-bound thiol groups to amine groups in collagen. XPS demonstrated surface-bound thiol groups without evidence of oxidation, along with the subsequent presence of maleimide and collagen. Glow discharge reactor parameters were optimized by testing the resistance of bound collagen to degradation by 8 M urea. The nature of the chemical bonding of collagen to surface thiol groups was effectively assessed by colorimetric assay (ELISA) of residual collagen after incubation in 8 M urea over 8 days and after incubation with keratinocytes over 15 days. The facile creation of useable solid-supported thiol groups via continuous phase glow discharge polymerization of allyl mercaptan opens a route for attaching a vast array of bioactive molecules. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1940-1948, 2017. © 2017 Wiley Periodicals, Inc.

Flexible diode of polyaniline/ITO heterojunction on PET substrate

NASA Astrophysics Data System (ADS)

Bera, A.; Deb, K.; Kathirvel, V.; Bera, T.; Thapa, R.; Saha, B.

2017-10-01

Hybrid organic-inorganic heterojunction between polyaniline and ITO film coated on flexible polyethylene terephthalate (PET) substrate has been prepared through vapor phase polymerization process. Polaron and bipolaron like defect states induced hole transport and exceptional mobility makes polyaniline a noble hole transport layer. Thus a p-n junction has been obtained between the hole transport layer of polyaniline and highly conductive n-type layer of ITO film. The synthesis process was carried out using FeCl3 as polymerizing agent in the oxidative chemical polymerization process. The prepared polyaniline has been found to be crystalline on characterization through X-ray diffraction measurement. X-ray photoelectron spectroscopic measurements were done for compositional analysis of the prepared film. The UV-vis-NIR absorbance spectra obtained for polyaniline shows the characteristics absorbance as observed for highly conductive polyaniline and confirms the occurrence of partially oxidized emeraldine form of polyaniline. The energy band gap of the polyaniline has been obtained as 2.52 eV, by analyzing the optical transmittance spectra. A rectifying behavior has been observed in the electrical J-V plot, which is of great significance in designing polymer based flexible electronic devices.

Sickle cell dehydration: Pathophysiology and therapeutic applications.

PubMed

Brugnara, Carlo

2018-01-01

Cell dehydration is a distinguishing characteristic of sickle cell disease and an important contributor to disease pathophysiology. Due to the unique dependence of Hb S polymerization on cellular Hb S concentration, cell dehydration promotes polymerization and sickling. In double heterozygosis for Hb S and C (SC disease) dehydration is the determining factor in disease pathophysiology. Three major ion transport pathways are involved in sickle cell dehydration: the K-Cl cotransport (KCC), the Gardos channel (KCNN4) and Psickle, the polymerization induced membrane permeability, most likely mediated by the mechano-sensitive ion channel PIEZO1. Each of these pathways exhibit unique characteristics in regulation by oxygen tension, intracellular and extracellular environment, and functional expression in reticulocytes and mature red cells. The unique dependence of K-Cl cotransport on intracellular Mg and the abnormal reduction of erythrocyte Mg content in SS and SC cells had led to clinical studies assessing the effect of oral Mg supplementation. Inhibition of Gardos channel by clotrimazole and senicapoc has led to Phase 1,2,3 trials in patients with sickle cell disease. While none of these studies has resulted in the approval of a novel therapy for SS disease, they have highlighted the key role played by these pathways in disease pathophysiology.

Polymer amide as an early topology.

PubMed

McGeoch, Julie E M; McGeoch, Malcolm W

2014-01-01

Hydrophobic polymer amide (HPA) could have been one of the first normal density materials to accrete in space. We present ab initio calculations of the energetics of amino acid polymerization via gas phase collisions. The initial hydrogen-bonded di-peptide is sufficiently stable to proceed in many cases via a transition state into a di-peptide with an associated bound water molecule of condensation. The energetics of polymerization are only favorable when the water remains bound. Further polymerization leads to a hydrophobic surface that is phase-separated from, but hydrogen bonded to, a small bulk water complex. The kinetics of the collision and subsequent polymerization are discussed for the low-density conditions of a molecular cloud. This polymer in the gas phase has the properties to make a topology, viz. hydrophobicity allowing phase separation from bulk water, capability to withstand large temperature ranges, versatility of form and charge separation. Its flexible tetrahedral carbon atoms that alternate with more rigid amide groups allow it to deform and reform in hazardous conditions and its density of hydrogen bonds provides adhesion that would support accretion to it of silicon and metal elements to form a stellar dust material.

Self-Supporting, Hydrophobic, Ionic Liquid-Based Reference Electrodes Prepared by Polymerization-Induced Microphase Separation

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

Chopade, Sujay A.; Anderson, Evan L.; Schmidt, Peter W.

Interfaces of ionic liquids and aqueous solutions exhibit stable electrical potentials over a wide range of aqueous electrolyte concentrations. This makes ionic liquids suitable as bridge materials that separate in electroanalytical measurements the reference electrode from samples with low and/or unknown ionic strengths. However, methods for the preparation of ionic liquid-based reference electrodes have not been explored widely. We have designed a convenient and reliable synthesis of ionic liquid-based reference electrodes by polymerization-induced microphase separation. This technique allows for a facile, single-pot synthesis of ready-to-use reference electrodes that incorporate ion conducting nanochannels filled with either 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-dodecyl-3-methylimidazolium bis(trifluoromethylmore » sulfonyl)imide as ionic liquid, supported by a mechanically robust cross-linked polystyrene phase. This synthesis procedure allows for the straightforward design of various reference electrode geometries. These reference electrodes exhibit a low resistance as well as good reference potential stability and reproducibility when immersed into aqueous solutions varying from deionized, purified water to 100 mM KCl, while requiring no correction for liquid junction potentials.« less

Fluorination Induced the Surface Segregation of High Voltage Spinel on Lithium-Rich Layered Cathodes for Enhanced Rate Capability in Lithium Ion Batteries.

PubMed

Jin, Yi-Chun; Duh, Jenq-Gong

2016-02-17

This study is aimed to explore the effect of fluoride doping and the associated structural transformation on lithium-rich layered cathode materials. The polymeric fluoride source is first adopted for synthesizing lithium intercalated oxide through a newly developed organic precipitation process. A heterostructured spinel/layered composite cathode material is obtained after appreciable fluorination and a superior rate capability is successfully achieved. The fluoride dopant amount and the surface spinel phase are evidenced and systematically examined by various structural spectroscopy and electrochemical analysis. It appears the reversible Ni(2+/4+) redox couple at high voltage regime around 4.8 V because of the formation of spinel LiNi1/2Mn3/2O4 phase. The mechanism of "layer to spinel" phase transformation is discussed in detail.

Facile preparation of fluorescent layered double hydroxide polymeric composites through the photo-induced surface-initiated controlled living polymerization

NASA Astrophysics Data System (ADS)

Chen, Junyu; Liu, Meiying; Huang, Qiang; Jiang, Ruming; Huang, Hongye; Deng, Fengjie; Wen, Yuanqing; Tian, Jianwen; Zhang, Xiaoyong; Wei, Yen

2018-05-01

(Zn/Al) layered double hydroxide (LDH) based fluorescence probes have been facilely fabricated via photo-induced surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, which demonstrated green fluorescence, good biocompatibility and excellent dispersion performance in aqueous solution. The as prepared (Zn/Al)LDH polymeric composites were modified with 2-methacryloyloxyethyl phosphorylcholine (MPC), acrylic acid (AA) and diacroloyl-fluorescein (Ac-Fl). Among them, the comonomers MPC and AA were used to endow their water dispersibility, biocompatibility and potential drug carriers, while the Ac-Fl was served both as the fluorescence signal and photocatalyst for RAFT polymerization. A series of characterization methods, including 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, transmission electronic microscopy, thermogravimetric analyses, X-ray photoelectron spectroscopy were employed to conform the successful of surface modification of LDH through photo-induced surface-initiated RAFT polymerization. Besides, UV-vis absorption spectra and fluorescence spectra were adopted to evaluate the optical characteristics of as prepared (Zn/Al)LDH-co-Poly(MPC-AA-Fl) composites, which exhibited high intense green fluorescence. Furthermore, the endocytosis behavior indicates that (Zn/Al)LDH-co-Poly(MPC-AA-Fl) composites could be potentially used in cell imaging and even drug delivery application for their excellent biocompatibility and all advantages described above.

Stabilization of enzymatically polymerized phenolic chemicals in a model soil organic matter-free geomaterial.

PubMed

Palomo, Mónica; Bhandari, Alok

2012-01-01

A variety of remediation methods, including contaminant transformation by peroxidase-mediated oxidative polymerization, have been proposed to manage soils and groundwater contaminated with chlorinated phenols. Phenol stabilization has been successfully observed during cross polymerization between phenolic polymers and soil organic matter (SOM) for soils with SOM >3%. This study evaluates peroxidase-mediated transformation and removal of 2,4-dichlorophenol (DCP) from an aqueous phase in contact with a natural geomaterial modified to contain negligible (<0.3%) SOM. The results are compared with those for soils with higher SOM. The SOM-free sorbent was generated by removing SOM using a NaOCl oxidation. When horseradish peroxidase (HRP) was used to induce polymerization of DCP, the soil-water phase distribution relationship (PDR) of DCP polymerization products (DPP) was complete within 1 d and PDRs did not significantly change over the 28 d of study. The conversion of DCP to DPP was close to 95% efficient. Extractable solute consisted entirely of DPP with 5% or less of unreacted DCP. The aqueous extractability of DPP from SOM-free geomaterial decreased at longer contact times and at smaller residual aqueous concentrations of DPP. DCP stabilization appeared to have resulted from a combination of sorption, precipitation, and ligand exchange between oligomeric products and the exposed mineral surfaces. Modification of the mineral surface through coverage with DPP enhanced the time-dependent retention of the oligomers. DPP stabilization in SOM-free geomaterial was comparable with that reported in the literature with soil containing SOM contents >1%. Results from this study suggest that the effectiveness of HRP-mediated stabilization of phenolic compounds not only depends on the cross-coupling with SOM, but also on the modification of the surface of the sorbent that can augment affinity with oligomers and enhance stabilization. Coverage of the mineral surface by phenolic oligomers may be analogous to SOM that can potentially sorb other xenobiotics. HRP- mediated reactions can be used to stabilize DCP associated with low SOM mineral soils or aquifer media, thereby restricting the transport of phenolic contaminants in the soil environment. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Tailoring the surface properties of polypropylene films through cold atmospheric pressure plasma (CAPP) assisted polymerization and immobilization of biomolecules for enhancement of anti-coagulation activity

NASA Astrophysics Data System (ADS)

Navaneetha Pandiyaraj, K.; Ram Kumar, M. C.; Arun Kumar, A.; Padmanabhan, P. V. A.; Deshmukh, R. R.; Bah, M.; Ismat Shah, S.; Su, Pi-Guey; Halleluyah, M.; Halim, A. S.

2016-05-01

Enhancement of anti-thrombogenic properties of polypropylene (PP) to avert the adsorption of plasma proteins (fibrinogen and albumin), adhesion and activation of the platelets are very important for vast biomedical applications. The cold atmospheric pressure plasma (CAPP) assisted polymerization has potential to create the specific functional groups such as Osbnd Cdbnd O, Cdbnd O, Csbnd N and Ssbnd S. on the surface of polymeric films using selective precursor in vapour phase to enhance anti-thrombogenic properties. Such functionalized polymeric surfaces would be suitable for various biomedical applications especially to improve the blood compatibility. The eventual aspiration of the present investigation is to develop the biofunctional coating onto the surface of PP films using acrylic acid (AAc) and polyethylene glycol (PEG) as a precursor in a vapour phase by incorporating specific functional groups for immobilization of biomolecules such as heparin (HEP), chitosan (CHI) and insulin (INS) on the surface of plasma modified PP films. The surface properties such as hydrophilicity, chemical composition, surface topography of the surface modified PP films were analyzed by contact angle (CA), Fourier transform infrared spectroscopy (FTIR), X-ray photo electron spectroscopy (XPS) and atomic force microscopy (AFM). Furthermore the anti-thrombogenic properties of the surface modified PP films were studied by in vitro tests which include platelet adhesion and protein adsorption analysis. It was found that the anti-thrombogenic properties of the PP films are effectively controlled by the CAPP grafting of AAc and PEG followed by immobilization of biomolecules of heparin, chitosan and insulin. The grafting and immobilization was confirmed by FTIR and XPS through the recognition of specific functional groups such as COOH, Csbnd O, Ssbnd S and Csbnd N. on the surface of PP film. Furthermore, the surface morphology and hydrophilic nature of the PP films also tailored significantly by the successful grafting and immobilization which is confirmed by AFM and CA analysis. Owing to the physico-chemical changes on the surface of PP films induced by CAPP assisted polymerization, the anti-thrombogenic properties of PP films were enhanced as confirmed by in vitro analysis.

Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

PubMed Central

Murthy, S Srinivasa; Murthy, Gargi S

2015-01-01

Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin. Materials and Methods: Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM). Results: In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001). Conclusion: Triad VLC resin can be polymerized by argon ion laser with 1 W/mm2 power and exposure time of 8 min to satisfy ADA specification. Impact strength, surface hardness of laser cure was better than light cure and heat cure resin. Flexural strength of light cure was better than laser cure and heat cure resin. The SEM study showed similar density on surface, the fractured surface of heat cure resin was dense and compact. PMID:26124596

Preparation of molecularly imprinted polymers for strychnine by precipitation polymerization and multistep swelling and polymerization and their application for the selective extraction of strychnine from nux-vomica extract powder.

PubMed

Nakamura, Yukari; Matsunaga, Hisami; Haginaka, Jun

2016-04-01

Monodisperse molecularly imprinted polymers for strychnine were prepared by precipitation polymerization and multistep swelling and polymerization, respectively. In precipitation polymerization, methacrylic acid and divinylbenzene were used as a functional monomer and crosslinker, respectively, while in multistep swelling and polymerization, methacrylic acid and ethylene glycol dimethacrylate were used as a functional monomer and crosslinker, respectively. The retention and molecular recognition properties of the molecularly imprinted polymers prepared by both methods for strychnine were evaluated using a mixture of sodium phosphate buffer and acetonitrile as a mobile phase by liquid chromatography. In addition to shape recognition, ionic and hydrophobic interactions could affect the retention of strychnine in low acetonitrile content. Furthermore, molecularly imprinted polymers prepared by both methods could selectively recognize strychnine among solutes tested. The retention factors and imprinting factors of strychnine on the molecularly imprinted polymer prepared by precipitation polymerization were 220 and 58, respectively, using 20 mM sodium phosphate buffer (pH 6.0)/acetonitrile (50:50, v/v) as a mobile phase, and those on the molecularly imprinted polymer prepared by multistep swelling and polymerization were 73 and 4.5. These results indicate that precipitation polymerization is suitable for the preparation of a molecularly imprinted polymer for strychnine. Furthermore, the molecularly imprinted polymer could be successfully applied for selective extraction of strychnine in nux-vomica extract powder. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-photon absorption spectrum of the photoinitiator Lucirin TPO-L

NASA Astrophysics Data System (ADS)

Mendonca, C. R.; Correa, D. S.; Baldacchini, T.; Tayalia, P.; Mazur, E.

2008-03-01

Two-photon absorption induced polymerization provides a powerful method for the fabrication of intricate three-dimensional microstructures. Recently, Lucirin TPO-L was shown to be a photoinitiator with several advantageous properties for two-photon induced polymerization. Here we measure the two-photon absorption cross-section spectrum of Lucirin TPO-L, which presents a maximum of 1.2 GM at 610 nm. Despite its small two-photon absorption cross-section, it is possible to fabricate excellent microstructures by two-photon polymerization due to the high polymerization quantum yield of Lucirin TPO-L. These results indicate that optimization of the two-photon absorption cross-section is not the only material parameter to be considered when searching for new photoinitiators for microfabrication via two-photon absorption.

Polymer-induced DNA Condensation in the Lamellar Phase of DNA-Lipid Complexes

NASA Astrophysics Data System (ADS)

Martin, Ana; Lin, Alison J.; Schulze, Uwe; Safinya, Cyrus R.; Schmidt, Hans-Werner

2000-03-01

The lamellar phase of cationic lipid-DNA complexes (CL-DNA)[1,2] is a model system for the study of a polymer induced condensation in two dimensions. Measurements of X-ray diffraction show DNA condensation with the addition of cationic poly(ethylene glycol) PEG-lipid to the membrane of the CL-DNA complexes, revealing the existence of two different behaviors as a function of the PEG length. For shorter PEG the DNA condensation can be described by considering the charge increase on the membrane due to the incorporation of the cationic polymeric chains. For longer PEG a deviation from the predicted electrostatic distance between DNA chains is observed. This higher condensation is caused by a novel depletion-attraction interaction between DNA chains in two dimensions. This work is supported by NSF-DMR9972246 and a fellowship of the Education Ministry of Spain. [1] Rädler, JO; Koltover, I; Salditt, T; Safinya, CR., Science 275, 810 (1997). [2] Koltover, I; Salditt, T; Safinya, CR., Biophys. J. 77, 915 (1999).

Effect of Monomer Solubility on the Evolution of Copolymer Morphology during Polymerization-Induced Self-Assembly in Aqueous Solution

PubMed Central

2017-01-01

Polymerization-induced self-assembly (PISA) has become a widely used technique for the rational design of diblock copolymer nano-objects in concentrated aqueous solution. Depending on the specific PISA formulation, reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization typically provides straightforward access to either spheres, worms, or vesicles. In contrast, RAFT aqueous emulsion polymerization formulations often lead to just kinetically-trapped spheres. This limitation is currently not understood, and only a few empirical exceptions have been reported in the literature. In the present work, the effect of monomer solubility on copolymer morphology is explored for an aqueous PISA formulation. Using 2-hydroxybutyl methacrylate (aqueous solubility = 20 g dm–3 at 70 °C) instead of benzyl methacrylate (0.40 g dm–3 at 70 °C) for the core-forming block allows access to an unusual “monkey nut” copolymer morphology over a relatively narrow range of target degrees of polymerization when using a poly(methacrylic acid) RAFT agent at pH 5. These new anisotropic nanoparticles have been characterized by transmission electron microscopy, dynamic light scattering, aqueous electrophoresis, shear-induced polarized light imaging (SIPLI), and small-angle X-ray scattering. PMID:28216792

Preparation and Cross-Linking of All-Acrylamide Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly in Aqueous Solution

PubMed Central

2017-01-01

Various carboxylic acid-functionalized poly(N,N-dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC–PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm. In contrast, either highly anisotropic worms or polydisperse vesicles are formed when relatively short macro-CTAs (DP = 40–58) are used. A phase diagram was constructed to enable accurate targeting of pure copolymer morphologies. Dynamic light scattering (DLS) and aqueous electrophoresis studies indicated that in most cases these PDMAC–PDAAM nano-objects are surprisingly resistant to changes in either solution pH or temperature. However, PDMAC40–PDAAM99 worms do undergo partial dissociation to form a mixture of relatively short worms and spheres on adjusting the solution pH from pH 2–3 to around pH 9 at 20 °C. Moreover, a change in copolymer morphology from worms to a mixture of short worms and vesicles was observed by DLS and TEM on heating this worm dispersion to 50 °C. Postpolymerization cross-linking of concentrated aqueous dispersions of PDMAC–PDAAM spheres, worms, or vesicles was performed at ambient temperature using adipic acid dihydrazide (ADH), which reacts with the hydrophobic ketone-functionalized PDAAM chains. The formation of hydrazone groups was monitored by FT-IR spectroscopy and afforded covalently stabilized nano-objects that remained intact on exposure to methanol, which is a good solvent for both blocks. Rheological studies indicated that the cross-linked worms formed a stronger gel compared to linear precursor worms. PMID:28260814

Microporous polymer films and methods of their production

DOEpatents

Aubert, James H.

1995-01-01

A process for producing thin microporous polymeric films for a variety of uses. The process utilizes a dense gas (liquified gas or supercritical fluid) selected to combine with a solvent-containing polymeric film so that the solvent is dissolved in the dense gas, the polymer is substantially insoluble in the dense gas, and two phases are formed. A microporous film is obtained by removal of a dense gas-solvent phase.

Nanoporous thermosetting polymers.

PubMed

Raman, Vijay I; Palmese, Giuseppe R

2005-02-15

Potential applications of nanoporous thermosetting polymers include polyelectrolytes in fuel cells, separation membranes, adsorption media, and sensors. Design of nanoporous polymers for such applications entails controlling permeability by tailoring pore size, structure, and interface chemistry. Nanoporous thermosetting polymers are often synthesized via free radical mechanisms using solvents that phase separate during polymerization. In this work, a novel technique for the synthesis of nanoporous thermosets is presented that is based on the reactive encapsulation of an inert solvent using step-growth cross-linking polymerization without micro/macroscopic phase separation. The criteria for selecting such a monomer-polymer-solvent system are discussed based on FTIR analysis, observed micro/macroscopic phase separation, and thermodynamics of swelling. Investigation of resulting network pore structures by scanning electron microscopy (SEM) and small-angle X-ray scattering following extraction and supercritical drying using carbon dioxide showed that nanoporous polymeric materials with pore sizes ranging from 1 to 50 nm can be synthesized by varying the solvent content. The differences in the porous morphology of these materials compared to more common free radically polymerized analogues that exhibit phase separation were evident from SEM imaging. Furthermore, it was demonstrated that the chemical activity of the nanoporous materials obtained by our method could be tailored by grafting appropriate functional groups at the pore interface.

Self-catalyzed photo-initiated RAFT polymerization for fabrication of fluorescent polymeric nanoparticles with aggregation-induced emission feature.

PubMed

Zeng, Guangjian; Liu, Meiying; Jiang, Ruming; Huang, Qiang; Huang, Long; Wan, Qing; Dai, Yanfeng; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

2018-02-01

In recent years, the fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) feature have been extensively exploited in various biomedical fields owing to their advantages, such as low toxicity, biodegradation, excellent biocompatibility, good designability and optical properties. Therefore, development of a facile, efficient and well designable strategy should be of great importance for the biomedical applications of these AIE-active FPNs. In this work, a novel method for the fabrication of AIE-active FPNs has been developed through the self-catalyzed photo-initiated reversible addition fragmentation chain transfer (RAFT) polymerization using an AIE dye containing chain transfer agent (CTA), which could initiate the RAFT polymerization under light irradiation. The results suggested that the final AIE-active FPNs (named as TPE-poly(St-PEGMA)) showed great potential for biomedical applications owing to their optical and biological properties. More importantly, the method described in the work is rather simple and effective and can be further extended to prepare many other different AIE-active FPNs owing to the good monomer adoptability of RAFT polymerization. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrical condition monitoring method for polymers

DOEpatents

Watkins, Jr. Kenneth S.; Morris, Shelby J.; Masakowski, Daniel D.; Wong, Ching Ping; Luo, Shijian

2010-02-16

An electrical condition monitoring method utilizes measurement of electrical resistivity of a conductive composite degradation sensor to monitor environmentally induced degradation of a polymeric product such as insulated wire and cable. The degradation sensor comprises a polymeric matrix and conductive filler. The polymeric matrix may be a polymer used in the product, or it may be a polymer with degradation properties similar to that of a polymer used in the product. The method comprises a means for communicating the resistivity to a measuring instrument and a means to correlate resistivity of the degradation sensor with environmentally induced degradation of the product.

Non-invasive analysis of swelling in polymer dispersions by means of time-domain(TD)-NMR.

PubMed

Nestle, Nikolaus; Häberle, Karl

2009-11-03

In this contribution, we discuss the potential of low-field time-domain(TD)-NMR to study the swelling of (aqueous) polymer dispersions by a volatile solvent. Due to the sensitivity of transverse relaxation times (T2) to swelling-induced changes in the molecular dynamics of the polymer component, the effects of swelling can be measured without spectral resolution. The measurement is performed on polymer dispersions in native state with solids contents around 50% in a non-invasive way without separating the polymeric phase and the water phase from each other. Using acetone in two polyurethane (PU) dispersions with different hard phase contents, we explore the sensitivity of the method and present a data evaluation strategy based on multicomponent fitting and proton balancing. Furthermore, we report exchange continualization as a further effect that needs to be taken into account for correct interpretation of the data.

Nanoscale control of reversible chemical reaction between fullerene C60 molecules using scanning tunneling microscope.

PubMed

Nakaya, Masato; Kuwahara, Yuji; Aono, Masakazu; Nakayama, Tomonobu

2011-04-01

The nanoscale control of reversible chemical reactions, the polymerization and depolymerization between C60 molecules, has been investigated. Using a scanning tunneling microscope (STM), the polymerization and depolymerization can be controlled at designated positions in ultrathin films of C60 molecules. One of the two chemical reactions can be selectively induced by controlling the sample bias voltage (V(s)); the application of negative and positive values of V(s) results in polymerization and depolymerization, respectively. The selectivity between the two chemical reactions becomes extremely high when the thickness of the C60 film increases to more than three molecular layers. We conclude that STM-induced negative and positive electrostatic ionization are responsible for the control of the polymerization and depolymerization, respectively.

Method of fabricating nested shells and resulting product

DOEpatents

Henderson, Timothy M.; Kool, Lawrence B.

1982-01-01

A multiple shell structure and a method of manufacturing such structure wherein a hollow glass microsphere is surface treated in an organosilane solution so as to render the shell outer surface hydrophobic. The surface treated glass shell is then suspended in the oil phase of an oil-aqueous phase dispersion. The oil phase includes an organic film-forming monomer, a polymerization initiator and a blowing agent. A polymeric film forms at each phase boundary of the dispersion and is then expanded in a blowing operation so as to form an outer homogeneously integral monocellular substantially spherical thermoplastic shell encapsulating an inner glass shell of lesser diameter.

Delivery of Vaccines By Biodegradable Polymeric Microcapsules with Bioadherence Properties. Phase 1.

DTIC Science & Technology

1995-10-01

DAMD17-95-C-5061 TITLE: Delivery of Vaccines by Biodegradable Polymeric Microcapsules with Bioadherence Properties PRINCIPAL INVESTIGATOR: Robert L...SUBTITLE 5. FUNDING NUMBERS Delivery of Vaccines By Biodegradable Polymeric Microcapsules with Bioadherence Properties DAMD17-95-C-5061 6. AUTHOR(S...SUBJECT TERMS 15. NUMBER OF PAGES Polymer microspheres 27 Microencapsulated vaccines 16. PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY

Synthesis of different heterocycles-linked chalcone conjugates as cytotoxic agents and tubulin polymerization inhibitors.

PubMed

Shankaraiah, Nagula; Nekkanti, Shalini; Brahma, Uma Rani; Praveen Kumar, Niggula; Deshpande, Namrata; Prasanna, Daasi; Senwar, Kishna Ram; Jaya Lakshmi, Uppu

2017-09-01

A series of new heterocycles-linked chalcone conjugates has been designed and synthesized by varying different alkane spacers. These conjugates were tested for their in vitro cytotoxic potential against a panel of selected human cancer cell lines namely, lung (A549 and NCI-H460), prostate (DU-145 and PC-3), colon (HCT-15 and HCT-116), and brain (U-87 glioblastoma) by MTT assay. Notably, among all the tested compounds, 4a exhibited potent cytotoxicity on NCI-H460 (lung cancer) cells with IC 50 of 1.48±0.19µM. The compound 4a showed significant inhibition of tubulin polymerization and disruption of the formation of microtubules (IC 50 of 9.66±0.06μM). Moreover, phase contrast microscopy and DAPI staining studies indicated that compound 4a can induce apoptosis in NCI-H460 cells. Further, the flow-cytometry analysis revealed that compound 4a arrests NCI-H460 cells in the G2/M phase of the cell cycle. In addition, molecular docking studies of the most active compounds 4a and 4b into the colchicine site of the tubulin, revealed the possible mode of interaction by these new conjugates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanotransforming Assemblies

NASA Astrophysics Data System (ADS)

Discher, Dennis

2005-03-01

Degradable polymeric materials with hydrolysable backbones have attracted much attention because they break down to non-toxic metabolites. They are the key solutions to many environmental problems, and are particularly useful for various biomedical applications. Much work has been focused on degradable polymers and their co-polymers as bulk, or films and monolayers.^2 Only limited work has explored the degradable amphiphilic copolymer self-assemblies (spherical micelles, worm micelles and vesicles) in solutions, which are quite important for soft-material engineering. Mostly spherical micelles, and in rare cases, vesicles, have been reported made from copolymers with degradable polyester, typically polylactide or polycaprolactone, as the hydrophobic block, connected to biocompatible, stealthy poly (ethylene oxide) as hydrophilic block. Morphological change of such spherical micelles induced by degradation is subtle, and the degradation kinetics and mechanism in assemblies, which can be quite different from that in bulk or film, are not well understood. Here we will describe the phase transformations of worm micelles and vesicles as they degrade and also highlight how these polymeric self-assemblies interact with lipid membranes.

Photo-processing P3HT conjugated polymers, in solution: A new route towards ordered polymeric structures.

NASA Astrophysics Data System (ADS)

Barbosa Neto, Newton; Dutra, Marcia; Araujo, Paulo; Sampaio, Renato

Solution aggregated thin films of conjugated polymers have demonstrated to be promising materials for many applications, e.g., solar cells and field-effect transistors. There are many standard methods to generate aggregates in polymeric solution, which includes poor solvent addiction and solution temperature manipulation. Here, we demonstrate a new approach to induce aggregate formation on solution of P3HT polymer. Under light excitation with 355 nm or 532 nm pulsed laser the polymer exhibit significant changes on its UV-Vis spectrum which are most known in the literature as the formation of H-J aggregates and additional new bands associated with polaron formation. Such changes in the amorphous phase of the polymers are seen in specific conditions of solvent combinations. We show also the dependency on the excitation laser power which can be identified as a threshold to ignite the formation of the new structure. We are grateful to CNPq and CAPES for financial support.

Intermolecular Structural Change for Thermoswitchable Polymeric Photosensitizer

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

Park, Wooram; Park, Sin-Jung; Cho, Soojeong

2016-08-17

A switchable photosensitizer (PS), which can be activated at a spe-cific condition beside light, has tremendous advantages for photo-dynamic therapy (PDT). Herein, we developed a thermo-switchable polymeric photosensitizer (T-PPS) by conjugating PS (Pheophor-bide-a, PPb-a) to a temperature-responsive polymer backbone of biocompatible hydroxypropyl cellulose (HPC). Self-quenched PS molecules linked in close proximity by pi-pi stacking in T-PPS were easily transited to an active monomeric state by the tempera-ture induced phase transition of polymer backbones. The tempera-ture responsive inter-molecular interaction changes of PS molecules in T-PPS were demonstrated in synchrotron small-angle X-ray scattering (SAXS) and UV-Vis spectrophotometer analysis. The T-PPS allowed switchablemore » activation and synergistically enhanced cancer cell killing effect at the hyperthermia temperature (45 °C). Our developed T-PPS has the considerable potential not only as a new class of photomedicine in clinics but also as a biosensor based on temperature responsiveness.« less

Microporous polymer films and methods of their production

DOEpatents

Aubert, J.H.

1995-06-06

A process is described for producing thin microporous polymeric films for a variety of uses. The process utilizes a dense gas (liquefied gas or supercritical fluid) selected to combine with a solvent-containing polymeric film so that the solvent is dissolved in the dense gas, the polymer is substantially insoluble in the dense gas, and two phases are formed. A microporous film is obtained by removal of a dense gas-solvent phase. 9 figs.

Enhancement of polar phase and conductivity relaxation in PIL-modified GO/PVDF composites

NASA Astrophysics Data System (ADS)

Xu, Pei; Fu, Weijia; Cui, Zhaopei; Ding, Yunsheng

2018-02-01

To investigate the effect of graphene oxide (GO) modified by polymerized ionic liquid (PIL) on the crystallization and dielectric relaxation of poly(vinylidene fluoride) (PVDF), a series of PVDF composites have been prepared using the solution casting method. The ion-dipole interaction between PIL and >CF2 and the π-dipole interaction between GO and >CF2 can induce synergistically the polar phase, and the π-ion interaction between GO and PIL can strengthen the induction effect of the polar phase and decrease the degree of crystallization of PVDF. The electric modulus and conductivity relaxation are employed to analyze the experimental complex dielectric permittivity. In the frequency spectra of complex permittivity of PVDF composites, space charge polarization and conductivity lead to a large value of dielectric permittivity. The temperature dependence of relaxation time of conductivity relaxation accords with the Arrhenius equation. A low degree of crystallization, more ion concentration, and polar phase in PVDF/PIL/GO enhance the movement of the polymer chain segment and charge carriers.

Energy storage crystalline gel materials for 3D printing application

NASA Astrophysics Data System (ADS)

Mao, Yuchen; Miyazaki, Takuya; Gong, Jin; Zhu, Meifang

2017-04-01

Phase change materials (PCMs) are considered one of the most reliable latent heat storage and thermoregulation materials. In this paper, a vinyl monomer is used to provide energy storage capacity and synthesize gel with phase change property. The side chain of copolymer form crystal microcell to storage/release energy through phase change. The crosslinking structure of the copolymer can protect the crystalline micro-area maintaining the phase change stable in service and improving the mechanical strength. By selecting different monomers and adjusting their ratios, we design the chemical structure and the crystallinity of gels, which in further affect their properties, such as strength, flexibility, thermal absorb/release transition temperature, transparency and the water content. Using the light-induced polymerization 3D printing techniques, we synthesize the energy storage gel and shape it on a 3D printer at the same time. By optimizing the 3D printing conditions, including layer thickness, curing time and light source, etc., the 3D printing objects are obtained.

Superwettability-Induced Confined Reaction toward High-Performance Flexible Electrodes.

PubMed

Xiong, Weiwei; Liu, Hongliang; Zhou, Yahong; Ding, Yi; Zhang, Xiqi; Jiang, Lei

2016-05-18

To find a general strategy to realize confinement of the conductive layer for high-performance flexible electrodes, with improved interfacial adhesion and high conductivity, is of important scientific significance. In this work, superwettability-induced confined reaction is used to fabricate high-performance flexible Ag/polymer electrodes, showing significantly improved silver conversion efficiency and interfacial adhesion. The as-prepared flexible electrodes by superhydrophilic polymeric surface under oil are highly conductive with an order of magnitude higher than the Ag/polymer electrodes obtained from original polymeric surface. The high conductivity achieved via superhydrophilic confinement is ascribed to the fact that the superhydrophilic polymeric surface can enhance the reaction rate of silver deposition and reduce the size of silver nanoparticles to achieve the densest packing. This new approach will provide a simple method to fabricate flexible and highly conductive Ag/polymer electrodes with excellent adhesion between the conductive layer and the substrate, and can be extended to other metal/polymeric electrodes or alloy/polymeric electrodes.

A New Route for High-Purity Organic Materials: High-Pressure-Ramp-Induced Ultrafast Polymerization of 2-(Hydroxyethyl)Methacrylate

NASA Astrophysics Data System (ADS)

Evlyukhin, E.; Museur, L.; Traore, M.; Perruchot, C.; Zerr, A.; Kanaev, A.

2015-12-01

The synthesis of highly biocompatible polymers is important for modern biotechnologies and medicine. Here, we report a unique process based on a two-step high-pressure ramp (HPR) for the ultrafast and efficient bulk polymerization of 2-(hydroxyethyl)methacrylate (HEMA) at room temperature without photo- and thermal activation or addition of initiator. The HEMA monomers are first activated during the compression step but their reactivity is hindered by the dense glass-like environment. The rapid polymerization occurs in only the second step upon decompression to the liquid state. The conversion yield was found to exceed 90% in the recovered samples. The gel permeation chromatography evidences the overriding role of HEMA2•• biradicals in the polymerization mechanism. The HPR process extends the application field of HP-induced polymerization, beyond the family of crystallized monomers considered up today. It is also an appealing alternative to typical photo- or thermal activation, allowing the efficient synthesis of highly pure organic materials.

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates and Method Relating Thereto

NASA Technical Reports Server (NTRS)

Simpson, Joycelyn O. (Inventor); St.Claire, Terry L. (Inventor)

2002-01-01

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared, This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors. in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches. adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrates; heating the metal electrode coated polymeric substrate in a low dielectric medium; applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates

NASA Technical Reports Server (NTRS)

Simpson, Joycely O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers. acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors, in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors. weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 1000 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium; applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates

NASA Technical Reports Server (NTRS)

Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors. in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium: applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Self assembled linear polymeric chains with tuneable semiflexibility using isotropic interactions.

PubMed

Abraham, Alex; Chatterji, Apratim

2018-04-21

We propose a two-body spherically symmetric (isotropic) potential such that particles interacting by the potential self-assemble into linear semiflexible polymeric chains without branching. By suitable control of the potential parameters, we can control the persistence length of the polymer and can even introduce a controlled number of branches. Thus we show how to achieve effective directional interactions starting from spherically symmetric potentials. The self-assembled polymers have an exponential distribution of chain lengths akin to what is observed for worm-like micellar systems. On increasing particle density, the polymeric chains self-organize to an ordered line-hexagonal phase where every chain is surrounded by six parallel chains, the transition is first order. On further increase in monomer density, the order is destroyed and we get a branched gel-like phase. This potential can be used to model semi-flexible equilibrium polymers with tunable semiflexibility and excluded volume. The use of the potential is computationally cheap and hence can be used to simulate and probe equilibrium polymer dynamics with long chains. The potential also gives a plausible method of tuning colloidal interactions in experiments such that one can obtain self-assembling polymeric chains made up of colloids and probe polymer dynamics using an optical microscope. Furthermore, we show how a modified potential leads to the observation of an intermediate nematic phase of self-assembled chains in between the low density disordered phase and the line-ordered hexagonal phase.

Self assembled linear polymeric chains with tuneable semiflexibility using isotropic interactions

NASA Astrophysics Data System (ADS)

Abraham, Alex; Chatterji, Apratim

2018-04-01

We propose a two-body spherically symmetric (isotropic) potential such that particles interacting by the potential self-assemble into linear semiflexible polymeric chains without branching. By suitable control of the potential parameters, we can control the persistence length of the polymer and can even introduce a controlled number of branches. Thus we show how to achieve effective directional interactions starting from spherically symmetric potentials. The self-assembled polymers have an exponential distribution of chain lengths akin to what is observed for worm-like micellar systems. On increasing particle density, the polymeric chains self-organize to an ordered line-hexagonal phase where every chain is surrounded by six parallel chains, the transition is first order. On further increase in monomer density, the order is destroyed and we get a branched gel-like phase. This potential can be used to model semi-flexible equilibrium polymers with tunable semiflexibility and excluded volume. The use of the potential is computationally cheap and hence can be used to simulate and probe equilibrium polymer dynamics with long chains. The potential also gives a plausible method of tuning colloidal interactions in experiments such that one can obtain self-assembling polymeric chains made up of colloids and probe polymer dynamics using an optical microscope. Furthermore, we show how a modified potential leads to the observation of an intermediate nematic phase of self-assembled chains in between the low density disordered phase and the line-ordered hexagonal phase.

Negatively charged polysulfone membranes with hydrophilicity and antifouling properties based on in situ cross-linked polymerization.

PubMed

Zhu, Lijing; Song, Haiming; Zhang, Dawei; Wang, Gang; Zeng, Zhixiang; Xue, Qunji

2017-07-15

Polysulfone (PSf) membrane has been widely used in water separation and purification, although, membrane fouling is still a serious problem limiting its potential. We aim to improve the antifouling of PSf membranes via a very simple and efficient method. In this work, antifouling PSf membranes were fabricated via in situ cross-linked polymerization coupled with non-solvent induced phase separation. In brief, acrylic acid (AA) and vinyltriethoxysilane (VTEOS) were copolymerized in PSf solution, then directly casted into membranes without purification. With the increase of monomers concentration, the morphology of the as-cast membranes changed from a finger-like morphology to a fully sponge-like structure due to the increased viscosity and decreased precipitation rate of the polymer solutions. Meanwhile, the hydrophilicity and electronegativity of modified membranes were highly improved leading to inhibited protein adsorption and improved antifouling property. Furthermore, in order to further find out the different roles player by AA and VTESO, the modified membrane without VTEOS was prepared and characterized. The results indicated that AA is more effective in the membrane hydrophilicity improvement, VTEOS is more crucial to improve membrane stability. This work provides valuable guidance for fabricating PSf membranes with hydrophilicity and antifouling property via in situ cross-linked polymerization. Copyright © 2017 Elsevier Inc. All rights reserved.

Nanoscale High Energetic Materials: A Polymeric Nitrogen Chain N8 Confined inside a Carbon Nanotube

NASA Astrophysics Data System (ADS)

Abou-Rachid, Hakima; Hu, Anguang; Timoshevskii, Vladimir; Song, Yanfeng; Lussier, Louis-Simon

2008-05-01

We present a theoretical study of a new hybrid material, nanostructured polymeric nitrogen, where a polymeric nitrogen chain is encapsulated in a carbon nanotube. The electronic and structural properties of the new system are studied by means of ab initio electronic structure and molecular dynamics calculations. Finite temperature simulations demonstrate the stability of this nitrogen phase at ambient pressure and room temperature using carbon nanotube confinement. This nanostructured confinement may open a new path towards stabilizing polynitrogen or polymeric nitrogen at ambient conditions.

Synthesis of 2-aryl-1,2,4-oxadiazolo-benzimidazoles: Tubulin polymerization inhibitors and apoptosis inducing agents.

PubMed

Kamal, Ahmed; Reddy, T Srinivasa; Vishnuvardhan, M V P S; Nimbarte, Vijaykumar D; Subba Rao, A V; Srinivasulu, Vunnam; Shankaraiah, Nagula

2015-08-01

A new series of 2-aryl 1,2,4-oxadiazolo-benzimidazole conjugates have been synthesized and evaluated for their antiproliferative activity in the sixty cancer cell line panel of the National Cancer Institute (NCI). Compounds 5l (NSC: 761109/1) and 5x (NSC: 761814/1) exhibited remarkable cytotoxic activity against most of the cancer cell lines in the one dose assay and were further screened at five dose concentrations (0.01, 0.1, 1, 10 and 100 μM) which showed GI50 values in the range of 0.79-28.2 μM. Flow cytometric data of these compounds showed increased cells in G2/M phase, which is suggestive of G2/M cell cycle arrest. Further, compounds 5l and 5x showed inhibition of tubulin polymerization and disruption of the formation of microtubules. These compounds induce apoptosis by DNA fragmentation and chromatin condensation as well as by mitochondrial membrane depolarization. In addition, structure activity relationship studies within the series are also discussed. Molecular docking studies of compounds 5l and 5x into the colchicine-binding site of the tubulin, revealed the possible mode of interaction by these compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lipase-catalyzed ring-opening polymerization of lactones to polyesters and its mechanistic aspects.

PubMed

Namekawa, S; Suda, S; Uyama, H; Kobayashi, S

1999-01-01

Lipase catalysis induced a ring-opening polymerization of lactones with different ring-sizes. Small-size (four-membered) and medium-size lactones (six- and seven-membered) as well as macrolides (12-, 13-, 16-, and 17-membered) were subjected to lipase-catalyzed polymerization. The polymerization behaviors depended primarily on the lipase origin and the monomer structure. The macrolides showing much lower anionic polymerizability were enzymatically polymerized faster than epsilon-caprolactone. The granular immobilized lipase derived from Candida antartica showed extremely efficient catalysis in the polymerization of epsilon-caprolactone. Single-step terminal functionalization of the polyester was achieved by initiator and terminator methods. The enzymatic polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics.

RAFT-Polymerization-Induced Self-Assembly and Reorganizations: Ultrahigh-Molecular-Weight Polymer and Morphology-Tunable Micro-/Nanoparticles in One Pot.

PubMed

Zhang, Xiao-Yun; Liu, Dong-Ming; Lv, Xin-Hu; Sun, Miao; Sun, Xiao-Li; Wan, Wen-Ming

2016-11-01

A one-pot method is introduced for the successful synthesis of narrow-distributed (Đ = 1.22) vinyl polymer with both ultrahigh molecular weight (UHMW) (M w = 1.31 × 10 6 g mol -1 ) and micro-/nanomorphology under mild conditions. The method involves the following four stages: homogeneous polymerization, polymerization-induced self-assembly (PISA), PISA and reorganization, and PISA and multiple reorganizations. The key points to the production of UHMW polystyrene are to minimize radical termination by segregating radicals in different nanoreactors and to ensure sufficient chain propagation by promoting further reorganizations of these reactors in situ. This method therefore endows polymeric materials with the outstanding properties of both UHMW and tunable micro-/nanoparticles under mild conditions in one pot. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent Developments of Versatile Photoinitiating Systems for Cationic Ring Opening Polymerization Operating at Any Wavelengths and under Low Light Intensity Sources.

PubMed

Lalevée, Jacques; Mokbel, Haifaa; Fouassier, Jean-Pierre

2015-04-20

Photoinitiators (PI) or photoinitiating systems (PIS) usable in light induced cationic polymerization (CP) and free radical promoted cationic polymerization (FRPCP) reactions (more specifically for cationic ring opening polymerization (ROP)) together with the involved mechanisms are briefly reviewed. The recent developments of novel two- and three-component PISs for CP and FRPCP upon exposure to low intensity blue to red lights is emphasized in details. Examples of such reactions under various experimental conditions are provided.

[Pseudolaric acid B induces G2/M arrest and inhibits invasion and migration in HepG2 hepatoma cells].

PubMed

Li, Shuai; Guo, Lianyi

2018-01-01

Objective To investigate the mechanisms of pseudolaric acid B (PAB) blocks cell cycle and inhibits invasion and migration in human hepatoma HepG2 cells. Methods The proliferation effect of PAB on HepG2 cells was evaluated by MTT assay. The effect of PAB on the cell cycle of HepG2 cells was analyzed by flow cytometry. Immunofluorescence cytochemical staining was applied to observe the effect of PAB on the α-tubulin polymerization and expression in HepG2 cells. Transwell TM chamber invasion assay and wound healing assay were performed to detect the influence of PAB on the migration and invasion ability of HepG2 cells. Western blotting was used to determine the expressions of α-tubulin, E-cadherin and MMP-9 in HepG2 cells after treated with PAB. Results PAB inhibited the proliferation of HepG2 cells in a dose-dependent manner and blocked the cell cycle in G2/M phase. PAB significantly changed the polymerization and decreased the expression of α-tubulin. The capacities of invasion and migration of HepG2 cells treated by PAB were significantly depressed. The protein levels of α-tubulin and MMP-9 decreased while the E-cadherin protein level increased. Conclusion PAB can inhibits the proliferation of HepG2 cells by down-regulating the expression of α-tubulin and influencing its polymerization, arresting HepG2 cells in G2/M phase. Meanwhile, PAB also can inhibit the invasion and migration of HepG2 cells by lowering cytoskeleton α-tubulin and MMP-9, and increasing E-cadherin.

Unraveling Structure-Property Relationships in Polymer Blends for Intelligent Materials Design

NASA Astrophysics Data System (ADS)

Irwin, Matthew Tyler

Block polymers provide an accessible route to structured, composite materials by combining two or more components with disparate mechanical, chemical, and electrical properties into a single bulk material with nanoscale domains. However, the characteristic lengthscale of these systems is limited, and the choice of components is restricted to those that are able to undergo microstructural ordering at accessible temperatures. This thesis details routes to overcoming these limitations through the addition of a lithium salt, a blend of homopolymers, or both. Chapter 2 describes a study wherein complex sphere phases such as the Frank-Kasper sigma phase can be observed in otherwise disordered asymmetric block polymers through the addition of a lithium salt. Chapter 3 discusses the development and characterization of a ternary polymer blend of an AB diblock copolymer and A and B homopolymers doped with a lithium salt. Detailed characterization showed that doping blends that are otherwise disordered with lithium salt induced microstructural ordering and largely recovers the phase behavior of traditional ternary polymer blends. A systematic study of the ionic conductivity of the blends at a fixed salt concentration demonstrates that, at a given composition, disordered, yet highly structured blends consistently exhibit better conductivity than polycrystalline morphologies with long range order. Chapter 4 extends the methodology of Chapter 3 and details a systematic study of the effects of cross-linker concentration on the performance of polymer electrolyte membranes produced via polymerization-induced microphase separation that exhibit a highly structured, globally disordered microstructure. Finally, Chapter 5 details efforts to develop a water filtration membrane using a polyethylene template derived from a polymeric bicontinuous microemulsion. Throughout all of this work, the goal is to better understand structure-property relationships at the molecular level in order to ultimately inform design criteria for materials where simultaneous control over morphology and mechanical, chemical, or electrical properties is important.

Significant vertical phase separation in solvent-vapor-annealed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) composite films leading to better conductivity and work function for high-performance indium tin oxide-free optoelectronics.

PubMed

Yeo, Jun-Seok; Yun, Jin-Mun; Kim, Dong-Yu; Park, Sungjun; Kim, Seok-Soon; Yoon, Myung-Han; Kim, Tae-Wook; Na, Seok-In

2012-05-01

In the present study, a novel polar-solvent vapor annealing (PSVA) was used to induce a significant structural rearrangement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films in order to improve their electrical conductivity and work function. The effects of polar-solvent vapor annealing on PEDOT:PSS were systematically compared with those of a conventional solvent additive method (SAM) and investigated in detail by analyzing the changes in conductivity, morphology, top and bottom surface composition, conformational PEDOT chains, and work function. The results confirmed that PSVA induces significant phase separation between excess PSS and PEDOT chains and a spontaneous formation of a highly enriched PSS layer on the top surface of the PEDOT:PSS polymer blend, which in turn leads to better 3-dimensional connections between the conducting PEDOT chains and higher work function. The resultant PSVA-treated PEDOT:PSS anode films exhibited a significantly enhanced conductivity of up to 1057 S cm(-1) and a tunable high work function of up to 5.35 eV. The PSVA-treated PEDOT:PSS films were employed as transparent anodes in polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs). The cell performances of organic optoelectronic devices with the PSVA-treated PEDOT:PSS anodes were further improved due to the significant vertical phase separation and the self-organized PSS top surface in PSVA-treated PEDOT:PSS films, which can increase the anode conductivity and work function and allow the direct formation of a functional buffer layer between the active layer and the polymeric electrode. The results of the present study will allow better use and understanding of polymeric-blend materials and will further advance the realization of high-performance indium tin oxide (ITO)-free organic electronics.

In situ AFM investigation of electrochemically induced surface-initiated atom-transfer radical polymerization.

PubMed

Li, Bin; Yu, Bo; Zhou, Feng

2013-02-12

Electrochemically induced surface-initiated atom-transfer radical polymerization is traced by in situ AFM technology for the first time, which allows visualization of the polymer growth process. It affords a fundamental insight into the surface morphology and growth mechanism simultaneously. Using this technique, the polymerization kinetics of two model monomers were studied, namely the anionic 3-sulfopropyl methacrylate potassium salt (SPMA) and the cationic 2-(metharyloyloxy)ethyltrimethylammonium chloride (METAC). The growth of METAC is significantly improved by screening the ammonium cations by the addition of ionic liquid electrolyte in aqueous solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced dual-frequency operation of a polymerized liquid crystal microplate by liquid crystal infiltration

NASA Astrophysics Data System (ADS)

Kumagai, Takayuki; Yoshida, Hiroyuki; Ozaki, Masanori

2017-04-01

The electric-field-induced switching behavior of a polymer microplate is investigated. A microplate fabricated with a photopolymerizable dual-frequency liquid crystal was surrounded by an unpolymerized photopolymerizable dual-frequency liquid crystal in the isotropic phase. As an electric field was applied along the plane of the microplate, the microplate switched to set its interior molecular orientation to be either parallel or perpendicular to the field, depending on the frequency. Analysis of the rotational behavior, as well as numerical calculations, showed that the surrounding unpolymerized photopolymerizable dual-frequency liquid crystal infiltrated into the microplate, which enhanced the dielectric properties of the microplate. To the best of our knowledge, this is the first report of an enhanced dual-frequency dielectric response of a polymer microplate induced by liquid crystal infiltration.

Interferometric pump-probe characterization of the nonlocal response of optically transparent ion implanted polymers

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Hadjichristov, Georgi B.

2012-03-01

Optical interferometric technique is applied to characterize the nonlocal response of optically transparent ion implanted polymers. The thermal nonlinearity of the ion-modified material in the near-surface region is induced by continuous wave (cw) laser irradiation at a relatively low intensity. The interferometry approach is demonstrated for a subsurface layer of a thickness of about 100 nm formed in bulk polymethylmethacrylate (PMMA) by implantation with silicon ions at an energy of 50 keV and fluence in the range 1014-1017 cm-2. The laser-induced thermooptic effect in this layer is finely probed by interferometric imaging. The interference phase distribution in the plane of the ion implanted layer is indicative for the thermal nonlinearity of the near-surface region of ion implanted optically transparent polymeric materials.

Grand-canonical solution of semiflexible self-avoiding trails on the Bethe lattice.

PubMed

Dantas, W G; Oliveira, Tiago J; Stilck, Jürgen F; Prellberg, Thomas

2017-02-01

We consider a model of semiflexible interacting self-avoiding trails (sISATs) on a lattice, where the walks are constrained to visit each lattice edge at most once. Such models have been studied as an alternative to the self-attracting self-avoiding walks (SASAWs) to investigate the collapse transition of polymers, with the attractive interactions being on site as opposed to nearest-neighbor interactions in SASAWs. The grand-canonical version of the sISAT model is solved on a four-coordinated Bethe lattice, and four phases appear: non-polymerized (NP), regular polymerized (P), dense polymerized (DP), and anisotropic nematic (AN), the last one present in the phase diagram only for sufficiently stiff chains. The last two phases are dense, in the sense that all lattice sites are visited once in the AN phase and twice in the DP phase. In general, critical NP-P and DP-P transition surfaces meet with a NP-DP coexistence surface at a line of bicritical points. The region in which the AN phase is stable is limited by a discontinuous critical transition to the P phase, and we study this somewhat unusual transition in some detail. In the limit of rods, where the chains are totally rigid, the P phase is absent and the three coexistence lines (NP-AN, AN-DP, and NP-DP) meet at a triple point, which is the endpoint of the bicritical line.

Glycosylated and nonglycosylated recombinant human granulocyte colony-stimulating factor differently modifies actin polymerization in neutrophils.

PubMed

Zucca, A; Brizzi, S; Riccioni, R; Azzarà, A; Ghimenti, M; Carulli, G

2006-01-01

Several neutrophil functions can be modified by rhG-CSF administration. Neutrophil morphology changes in the course of treatment with Filgrastim (nonglycosylated rhG-CSF), along with impairment of chemotaxis. Both morphology and chemotaxis are not affected by treatment with Lenograstim (glycosylated rhG-CSF). Thus, we evaluated actin polymerization in neutrophils induced by treatment with the two forms of rhG-CSF. In fact, actin polymerization is crucial for neutrophil motility. We evaluated twelve healthy subjects undergoing peripheral blood stem cells (PBSC) mobilization for allogeneic transplantation to HLA-identical siblings. Neutrophils were isolated by peripheral venous blood before and after administration of either Filgrastim (six PBSC donors) or Lenograstim (six PBSC donors). Actin polymerization was investigated by a flow cytometric assay, using FITC-phalloidin as a specific probe for F-actin, and two parameters were measured: spontaneous actin polymerization in resting neutrophils; fMLP-stimulated actin polymerization. Results were expressed as relative F-actin content. Fifteen blood donors were studied as a control group. Filgrastim administration induced an increased relative F-actin content in resting neutrophils; however, no further actin polymerization was observed after fMLP stimulation. Neutrophils from subjects treated with Lenograstim showed a normal behaviour in terms of both spontaneous and stimulated actin polymerization. Glycosylated and nonglycosylated rhG-CSF differently affect actin polymerization in newly generated neutrophils. Such effects may explain some previous findings concerning both morphology and chemotactic properties and may be due to different effects of the two forms of rhG-CSF on proteins involved in neutrophil motility regulation.

PLCβ3 mediates cortactin interaction with WAVE2 in MCP1-induced actin polymerization and cell migration

PubMed Central

Janjanam, Jagadeesh; Chandaka, Giri Kumar; Kotla, Sivareddy; Rao, Gadiparthi N.

2015-01-01

Monocyte chemotactic protein 1 (MCP1) stimulates vascular smooth muscle cell (VSMC) migration in vascular wall remodeling. However, the mechanisms underlying MCP1-induced VSMC migration have not been understood. Here we identify the signaling pathway associated with MCP1-induced human aortic smooth muscle cell (HASMC) migration. MCP1, a G protein–coupled receptor agonist, activates phosphorylation of cortactin on S405 and S418 residues in a time-dependent manner, and inhibition of its phosphorylation attenuates MCP1-induced HASMC G-actin polymerization, F-actin stress fiber formation, and migration. Cortactin phosphorylation on S405/S418 is found to be critical for its interaction with WAVE2, a member of the WASP family of cytoskeletal regulatory proteins required for cell migration. In addition, the MCP1-induced cortactin phosphorylation is dependent on PLCβ3-mediated PKCδ activation, and siRNA-mediated down-regulation of either of these molecules prevents cortactin interaction with WAVE2, affecting G-actin polymerization, F-actin stress fiber formation, and HASMC migration. Upstream, MCP1 activates CCR2 and Gαq/11 in a time-dependent manner, and down-regulation of their levels attenuates MCP1-induced PLCβ3 and PKCδ activation, cortactin phosphorylation, cortactin–WAVE2 interaction, G-actin polymerization, F-actin stress fiber formation, and HASMC migration. Together these findings demonstrate that phosphorylation of cortactin on S405 and S418 residues is required for its interaction with WAVE2 in MCP1-induced cytoskeleton remodeling, facilitating HASMC migration. PMID:26490115

DISPERSION POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE IN SUPERCRITICAL CARBON DIOXIDE. (R826115)

EPA Science Inventory

Herein we report a successful dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) in a carbon dioxide continuous phase with a block copolymer consisting of polystyrene and poly(1,1-dihydroperfluorooctyl acrylate) as a stabilizer. Poly(2-hydroxyethyl methacrylate) was ...

Analyses and comparison of a novel, hybrid, multifunctional orthopedic composite and implant

NASA Astrophysics Data System (ADS)

Dicicco, Michael

In the orthopedic/medical device industry, 2, 2' -bis-(4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (Bis-GMA)- and diurethanedimethacrylate (DUDMA)-based polymeric biomaterials have become well-known substitutes for polymethylmethacrylate (PMMA)- and ultra-high molecular weight polyethylene (UHMWPE)-based biomaterials, respectively. The development of these polymeric biomaterials cannot continue without direct comparison studies against currently marketed materials. The initiative for this research stems wholly from developing analytical methodologies that assist in qualifying novel biomaterials under development, by evaluating their chemical properties, performance, and safety. The goals of this research were: (i) Characterize the assay/quality of every resin component and quantify elution of extractable monomers from novel, DUDMA-based RHAKOSS(TM) implant, (ii) Determine degree of conversion (alpha) and rate of polymerization (Rp) for novel, Bis-GMA-based CORTOSS(TM) composite, (iii) Assess risk for radical-induced post-surgical cytotoxicity for CORTOSS, (iv) Determine if surface radical chemistries occur for sterilized RHAKOSS and assess its oxidative stability, and (v) Quantify antibiotic elution from antibiotic-impregnated CORTOSS and identify factors that control elution. The phenomena studied necessitated the utilization of several analytical spectroscopic techniques; fluorometry, differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), ultraviolet-visible (UV-VIS), attenuated total reflectance---Fourier-transform infrared (ATR-FTIR), and high performance liquid chromatography (HPLC). A battery of lateral chemical techniques were employed as well; including molecular derivatization/tagging, phase partitioning, spin-trapping, and thermal annealing. Results demonstrated that RHAKOSS monomer percent compositions were prepared according to formulations and monomer elution was virtually undetectable, serving as an empirical gauge to portend degree of polymerization (DOP). A high alpha was reported for CORTOSS and essentially all bifunctional monomers had at least one functional group polymerized, stressing low monomer elution potential. Regarding cytotoxicity, CORTOSS impeded further production of hydroxyl radicals (•OH), whereas RHAKOSS did not facilitate the Fenton reaction but displayed some chelating abilities. Residual radicals in RHAKOSS were easily terminated, thus not projected to form oxidative degradants. Additionally, significant antibiotic concentrations, over extended durations, eluted from CORTOSS in linear-type fashion, advocating a sustained therapeutic effect, and phase partitioning correlated antibiotic release to hydrophilicity. The incurred data comprehensively argues in favor of the excellent biocompatibility that CORTOSS and RHAKOSS inherently possess, and was definitive in rendering them as advanced biomaterials, possessing favorable chemical properties.

The small molecule CS1 inhibits mitosis and sister chromatid resolution in HeLa cells.

PubMed

Wu, Xingkang; Li, Zhenyu; Shen, Yuemao

2018-05-01

Mitosis, the most dramatic event in the cell cycle, involves the reorganization of virtually all cellular components. Antimitotic agents are useful for dissecting the mechanism of this reorganization. Previously, we found that the small molecule CS1 accumulates cells in G2/M phase [1], but the mechanism of its action remains unknown. Cell cycle analysis, live cell imaging and nuclear staining were used. Chromosomal morphology was detected by chromosome spreading. The effects of CS1 on microtubules were confirmed by tubulin polymerization, colchicine tubulin-binding, cellular tubulin polymerization and immunofluorescence assays and by analysis of microtubule dynamics and molecular modeling. Histone phosphoproteomics was performed using mass spectrometry. Cell signaling cascades were analyzed using immunofluorescence, immunoprecipitation, immunoblotting, siRNA knockdown and chemical inhibition of specific proteins. The small molecule CS1 was shown to be an antimitotic agent. CS1 potently inhibited microtubule polymerization via interaction with the colchicine-binding pocket of tubulin in vitro and inhibited the formation of the spindle apparatus by reducing the bulk of growing microtubules in HeLa cells, which led to activation of the spindle assembly checkpoint (SAC) and mitotic arrest of HeLa cells. Compared with colchicine, CS1 impaired the progression of sister chromatid resolution independent of cohesin dissociation, and this was reversed by the removal of CS1. Additionally, CS1 induced unique histone phosphorylation patterns distinct from those induced by colchicine. CS1 is a unique antimitotic small molecule and a powerful tool with unprecedented value over colchicine that makes it possible to specifically and conditionally perturb mitotic progression. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparison of expandable endotracheal stents in the treatment of surgically induced piglet tracheomalacia.

PubMed

Mair, E A; Parsons, D S; Lally, K P; Van Dellen, A F

1991-09-01

Present surgical alternatives for pediatric tracheobronchomalacia are limited and associated with many potentially undesirable complications. The feasibility of different intraluminal expandable endotracheal stents for the treatment of surgically induced tracheomalacia was analyzed in 27 piglets. A potentially fatal tracheomalacia was surgically created. Either a stainless steel "zig-zag" stent or a woven polymeric stent was then implanted. Tracheal patency, mucosal function, histopathologic respiratory tract changes, and effects of the stent on esophageal motility were evaluated over a 16-week period. Piglets with steel stents uniformly experienced intense inflammation leading to tracheal dysfunction and death. Piglets with polymeric stents experienced minimal respiratory symptoms. Expandable polymeric endotracheal stents alleviate surgically induced piglet tracheomalacia, were easy to insert, allowed for tracheal growth, and reduced the need for high-risk surgical procedures with prolonged ventilatory support.

The effect of phase change materials on the frontal polymerization of a triacrylate

NASA Astrophysics Data System (ADS)

Viner, Veronika G.; Pojman, John A.; Golovaty, Dmitry

2010-06-01

The production of smoke and fumes is a major obstacle to the practical use of thermal frontal polymerization. The front temperature and the amount of smoking can be reduced by adding inert fillers, such as clay and silica, to the reactive mixture. Here we investigate the possibility of incorporating inert materials that melt (so-called phase change materials) to the mixture. By performing both experiments and mathematical modeling, we demonstrate that, in addition to the standard parameters of frontal polymerization, the front temperature and velocity depend on the melting point and heat of fusion of the phase change material. We use the method of matched asymptotic expansions to develop an explicit expression for the velocity of the reaction front. The expression demonstrates that the behavior of the front is determined by the difference between the reaction temperature and the melting temperature, with the front being slower and cooler if melting occurs farther ahead of the reaction front. The theoretical trends are hard to confirm directly because different characteristics of the phase change material cannot be varied separately.

Liquid Crystals in Chromatography

NASA Astrophysics Data System (ADS)

Witkiewicz, Zygfryd

The following sections are included: * INTRODUCTION * LIQUID CRYSTALS SUITABLE FOR GAS CHROMATOGRAPHY * Monomeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Conventional Analytical Columns * Capillary Columns * FACTORS AFFECTING THE CHROMATOGRAPHIC SEPARATIONS ON LIQUID CRYSTAL STATIONARY PHASES * Kind of Mesophase of the Liquid Crystal * Molecular Structure of the Liquid Crystals and of the Chromatographed Substances * Substrate on which the Liquid Crystal is Deposited * ANALYTICAL APPLICATIONS OF LIQUID CRYSTAL STATIONARY PHASES IN GAS CHROMATOGRAPHY * Separation of Isomers of Benzene and Naphthalene Derivatives * Separation of Alkane and Alkene Isomers * Separation of Mixtures of Benzene and Aliphatic Hydrocarbon Derivatives Containing Heteroatoms * Separation of Polynuclear Hydrocarbons * INVESTIGATION OF THE PROPERTIES OF LIQUID CRYSTALS BY GAS CHROMATOGRAPHY * APPLICATION OF LIQUID CRYSTALS IN LIQUID CHROMATOGRAPHY * Column Chromatography * Thin-Layer Chromatography * APPLICATION OF LIQUID CRYSTAL STATIONARY PHASES IN SUPERCRITICAL FLUID CHROMATOGRAPHY * FINAL REMARKS * References

Design of multi-phase dynamic chemical networks

NASA Astrophysics Data System (ADS)

Chen, Chenrui; Tan, Junjun; Hsieh, Ming-Chien; Pan, Ting; Goodwin, Jay T.; Mehta, Anil K.; Grover, Martha A.; Lynn, David G.

2017-08-01

Template-directed polymerization reactions enable the accurate storage and processing of nature's biopolymer information. This mutualistic relationship of nucleic acids and proteins, a network known as life's central dogma, is now marvellously complex, and the progressive steps necessary for creating the initial sequence and chain-length-specific polymer templates are lost to time. Here we design and construct dynamic polymerization networks that exploit metastable prion cross-β phases. Mixed-phase environments have been used for constructing synthetic polymers, but these dynamic phases emerge naturally from the growing peptide oligomers and create environments suitable both to nucleate assembly and select for ordered templates. The resulting templates direct the amplification of a phase containing only chain-length-specific peptide-like oligomers. Such multi-phase biopolymer dynamics reveal pathways for the emergence, self-selection and amplification of chain-length- and possibly sequence-specific biopolymers.

Spatially controlled, in situ synthesis of polymers

DOEpatents

Caneba, Gerard T.; Tirumala, Vijaya Raghavan; Mancini, Derrick C.; Wang, Hsien-Hau

2005-03-22

An in situ polymer microstructure formation method. The monomer mixture is polymerized in a solvent/precipitant through exposure to ionizing radiation in the absence any chemical mediators. If an exposure mask is employed to block out certain regions of the radiation cross section, then a patterned microstructure is formed. The polymerization mechanism is based on the so-called free-radical retrograde-precipitation polymerization process, in which polymerization occurs while the system is phase separating above the lower critical solution temperature. This method was extended to produce a crosslinked line grid-pattern of poly (N-isopropylacrylamide), which has been known to have thermoreversible properties.

Interfacially polymerized layers for oxygen enrichment: a method to overcome Robeson's upper-bound limit.

PubMed

Tsai, Ching-Wei; Tsai, Chieh; Ruaan, Ruoh-Chyu; Hu, Chien-Chieh; Lee, Kueir-Rarn

2013-06-26

Interfacial polymerization of four aqueous phase monomers, diethylenetriamine (DETA), m-phenylenediamine (mPD), melamine (Mela), and piperazine (PIP), and two organic phase monomers, trimethyl chloride (TMC) and cyanuric chloride (CC), produce a thin-film composite membrane of polymerized polyamide layer capable of O2/N2 separation. To achieve maximum efficiency in gas permeance and O2/N2 permselectivity, the concentrations of monomers, time of interfacial polymerization, number of reactive groups in monomers, and the structure of monomers need to be optimized. By controlling the aqueous/organic monomer ratio between 1.9 and 2.7, we were able to obtain a uniformly interfacial polymerized layer. To achieve a highly cross-linked layer, three reactive groups in both the aqueous and organic phase monomers are required; however, if the monomers were arranged in a planar structure, the likelihood of structural defects also increased. On the contrary, linear polymers are less likely to result in structural defects, and can also produce polymer layers with moderate O2/N2 selectivity. To minimize structural defects while maximizing O2/N2 selectivity, the planar monomer, TMC, containing 3 reactive groups, was reacted with the semirigid monomer, PIP, containing 2 reactive groups to produce a membrane with an adequate gas permeance of 7.72 × 10(-6) cm(3) (STP) s(-1) cm(-2) cm Hg(-1) and a high O2/N2 selectivity of 10.43, allowing us to exceed the upper-bound limit of conventional thin-film composite membranes.

Enhancement of in vivo Antitumor Activity of a Novel Antimitotic 1‐Phenylpropenone Derivative, AM‐132, by Tumor Necrosis Factor‐cc or Interleukin‐6

PubMed Central

Tatsumi, Yasuaki; Arioka, Hitoshi; Ikeda, Shun‐ichi; Fukumoto, Hisao; Miyamoto, Ken‐ichi; Fukuoka, Kazuya; Ohe, Yuichiro; Saijo, Nagahiro

2001-01-01

TK5048 and its derivatives, AM‐132, AM‐138, and AM‐97, are recently developed antimitotic (AM) compounds. These 1‐phenylpropenone derivatives induce cell cycle arrest at the G2/M phase of the cell cycle. TK5048 inhibited tubulin polymerization in human lung cancer PC‐14 cells in a concentration‐dependent manner. In a polymerization assay using bovine brain tubulin, AM‐132 and AM‐138 were quite strong, AM‐97 was moderately strong, and TK5048 was a relatively weak inhibitor of tubulin polymerization. A murine leukemia cell line resistant to a sulfonamide antimitotic agent, E7010, which binds to colchicine‐binding sites on tubulin, was cross‐resistant to the in vitro growth‐inhibitory effect of AM compounds. Inhibition of tubulin polymerization is therefore one of the mechanisms of action of these AM compounds against tumor cells. To profile the antitumor effect of AM compounds, the in vivo antitumor effect of AM‐132 was evaluated against cytokine‐secreting Lewis lung carcinoma (LLC). Tumor‐bearing mice were treated with intravenous AM‐132 using three different treatment schedules. LLC tumors expressing tumor necrosis factor‐a (TNF‐α), granulocyte macrophage colony‐stimulating factor (GM‐CSF), or interleukin (TL)‐6 were very sensitive to AM‐132. In particular, LLC tumors expressing IL‐6 were markedly reduced by AM‐132 treatment, and showed coloring of the tumor surface and unusual hemorrhagic necrosis. These results suggest a combined effect of AM‐132 and cytokines on the blood supply to tumors. PMID:11473728

Enhancement of in vivo antitumor activity of a novel antimitotic 1-phenylpropenone derivative, AM-132, by tumor necrosis factor-alpha or interleukin-6.

PubMed

Tatsumi, Y; Arioka, H; Ikeda, S; Fukumoto, H; Miyamoto, K; Fukuoka, K; Ohe, Y; Saijo, N; Nishio, K

2001-07-01

TK5048 and its derivatives, AM-132, AM-138, and AM-97, are recently developed antimitotic (AM) compounds. These 1-phenylpropenone derivatives induce cell cycle arrest at the G2 / M phase of the cell cycle. TK5048 inhibited tubulin polymerization in human lung cancer PC-14 cells in a concentration-dependent manner. In a polymerization assay using bovine brain tubulin, AM-132 and AM-138 were quite strong, AM-97 was moderately strong, and TK5048 was a relatively weak inhibitor of tubulin polymerization. A murine leukemia cell line resistant to a sulfonamide antimitotic agent, E7010, which binds to colchicine-binding sites on tubulin, was cross-resistant to the in vitro growth-inhibitory effect of AM compounds. Inhibition of tubulin polymerization is therefore one of the mechanisms of action of these AM compounds against tumor cells. To profile the antitumor effect of AM compounds, the in vivo antitumor effect of AM-132 was evaluated against cytokine-secreting Lewis lung carcinoma (LLC). Tumor-bearing mice were treated with intravenous AM-132 using three different treatment schedules. LLC tumors expressing tumor necrosis factor-alpha (TNF-alpha), granulocyte macrophage colony-stimulating factor (GM-CSF), or interleukin (IL)-6 were very sensitive to AM-132. In particular, LLC tumors expressing IL-6 were markedly reduced by AM-132 treatment, and showed coloring of the tumor surface and unusual hemorrhagic necrosis. These results suggest a combined effect of AM-132 and cytokines on the blood supply to tumors.

Selective, retrieval-independent disruption of methamphetamine-associated memory by actin depolymerization.

PubMed

Young, Erica J; Aceti, Massimiliano; Griggs, Erica M; Fuchs, Rita A; Zigmond, Zachary; Rumbaugh, Gavin; Miller, Courtney A

2014-01-15

Memories associated with drugs of abuse, such as methamphetamine (METH), increase relapse vulnerability to substance use disorder. There is a growing consensus that memory is supported by structural and functional plasticity driven by F-actin polymerization in postsynaptic dendritic spines at excitatory synapses. However, the mechanisms responsible for the long-term maintenance of memories, after consolidation has occurred, are largely unknown. Conditioned place preference (n = 112) and context-induced reinstatement of self-administration (n = 19) were used to assess the role of F-actin polymerization and myosin II, a molecular motor that drives memory-promoting dendritic spine actin polymerization, in the maintenance of METH-associated memories and related structural plasticity. Memories formed through association with METH but not associations with foot shock or food reward were disrupted by a highly-specific actin cycling inhibitor when infused into the amygdala during the postconsolidation maintenance phase. This selective effect of depolymerization on METH-associated memory was immediate, persistent, and did not depend upon retrieval or strength of the association. Inhibition of non-muscle myosin II also resulted in a disruption of METH-associated memory. Thus, drug-associated memories seem to be actively maintained by a unique form of cycling F-actin driven by myosin II. This finding provides a potential therapeutic approach for the selective treatment of unwanted memories associated with psychiatric disorders that is both selective and does not rely on retrieval of the memory. The results further suggest that memory maintenance depends upon the preservation of polymerized actin. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

PubMed

Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

2011-08-15

Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. Copyright © 2011 Elsevier Inc. All rights reserved.

Ultralow protein adsorbing coatings from clickable PEG nanogel solutions: Benefits of attachment under salt-induced phase separation conditions and comparison with PEG/albumin nanogel coatings

PubMed Central

Donahoe, Casey D.; Cohen, Thomas L.; Li, Wenlu; Nguyen, Peter K.; Fortner, John D.; Mitra, Robi D.; Elbert, Donald L.

2013-01-01

Clickable nanogel solutions were synthesized by using the copper catalyzed azide/alkyne cycloaddition (CuAAC) to partially polymerize solutions of azide and alkyne functionalized poly(ethylene glycol) (PEG) monomers. Coatings were fabricated using a second click reaction: a UV thiol-yne attachment of the nanogel solutions to mercaptosilanated glass. Because the CuAAC reaction was effectively halted by the addition of a copper-chelator, we were able to prevent bulk gelation and limit the coating thickness to a single monolayer of nanogels in the absence of the solution reaction. This enabled the inclusion of kosmotropic salts, which caused the PEG to phase-separate and nearly double the nanogel packing density, as confirmed by Quartz Crystal Microbalance with Dissipation (QCM-D). Protein adsorption was analyzed by single molecule counting with total internal reflection fluorescence (TIRF) microscopy and cell adhesion assays. Coatings formed from the phase-separated clickable nanogel solutions attached with salt adsorbed significantly less fibrinogen than other 100% PEG coatings tested, as well as poly-L-lysine-g-PEG (PLL-g-PEG) coatings. However, PEG/albumin nanogel coatings still outperformed the best 100% PEG clickable nanogel coatings. Additional surface crosslinking of the clickable nanogel coating in the presence of copper further reduced levels of fibrinogen adsorption closer to those of PEG/albumin nanogel coatings. However, this step negatively impacted long-term resistance to cell adhesion and dramatically altered the morphology of the coating by atomic force microscopy (AFM). The main benefit of the click strategy is that the partially polymerized solutions are stable almost indefinitely, allowing attachment in the phase-separated state without danger of bulk gelation, and thus, producing the best performing 100% PEG coating that we have studied to date. PMID:23441808

Early stages of styrene-isoprene copolymerization in gas phase clusters probed by resonance enhanced multiphoton ionization.

PubMed

Mahmoud, Hatem; Germanenko, Igor N; El-Shall, M Samy

2006-04-06

We present direct evidence for the formation of the covalent bonded styrene (isoprene)(2) oligomer and the isoprene dimer ions following resonance ionization of the gas phase styrene-isoprene binary clusters. The application of resonance ionization to study polymerization reactions in clusters provides new information on the structure and mechanism of formation of the early stages of polymerization and holds considerable promise for the discovery of new initiation mechanisms and for the development of novel materials with unique properties.

The fabrication of small molecule organic light-emitting diode pixels by laser-induced forward transfer

NASA Astrophysics Data System (ADS)

Shaw-Stewart, J. R. H.; Mattle, T.; Lippert, T. K.; Nagel, M.; Nüesch, F. A.; Wokaun, A.

2013-01-01

Laser-induced forward transfer (LIFT) is a versatile organic light-emitting diode (OLED) pixel deposition process, but has hitherto been applied exclusively to polymeric materials. Here, a modified LIFT process has been used to fabricate small molecule Alq3 organic light-emitting diodes (SMOLEDs). Small molecule thin films are considerably more mechanically brittle than polymeric thin films, which posed significant challenges for LIFT of these materials. The LIFT process presented here uses a polymeric dynamic release layer, a reduced environmental pressure, and a well-defined receiver-donor gap. The Alq3 pixels demonstrate good morphology and functionality, even when compared to conventionally fabricated OLEDs. The Alq3 SMOLED pixel performances show a significant amount of fluence dependence, not observed with polymerical OLED pixels made in previous studies. A layer of tetrabutyl ammonium hydroxide has been deposited on top of the aluminium cathode, as part of the donor substrate, to improve electron injection to the Alq3, by over 600%. These results demonstrate that this variant of LIFT is applicable for the deposition of functional small molecule OLEDs as well as polymeric OLEDs.

Structure modification and extracellular polymeric substances conversion during sewage sludge biodrying process.

PubMed

Cai, Lu; Krafft, Thomas; Chen, Tong-Bin; Gao, Ding; Wang, Li

2016-09-01

Biodrying, an economical and energy-saving biomass waste treatment, removes water from waste using the biological heat generated by organic matter degradation. Technical limitations associated with dewatering complicate the biodrying of sewage sludge. This study investigated the sludge alteration associated with its water removal, focusing on sludge form, extracellular polymeric substances, and free water release. An auto-feedback control technology was used for the biodrying; a scanning electron microscope was used to record the morphological change; three-dimensional excitation-emission matrix fluorescence spectroscopy was used to analyze extracellular polymeric substances (EPS) variation, and time domain reflectometry was used to assess the free water release. Over the 20-day biodrying, there was a 62% water removal rate during the first thermophilic phase. Biodrying created a hollow and stratified sludge structure. Aromatic proteins and soluble microbial byproducts in the EPS were significantly degraded. The thermophilic phase was the phase resulting in the greatest free water release. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of sonically induced deflocculation on the efficiency of ozone mediated partial sludge disintegration for improved production of biogas.

PubMed

Sowmya Packyam, G; Kavitha, S; Adish Kumar, S; Kaliappan, S; Yeom, Ick Tae; Rajesh Banu, J

2015-09-01

In this study, ultrasonication was used for sludge deflocculation, followed by cell disintegration using ozone. The effect of this phase separated sono-ozone pretreatment is evaluated based on extra polymeric substances release, deoxyribonucleic acid (DNA) in the medium, solubilization of intra cellular components and suspended solids (SS) reduction. Ultrasonically induced deflocculation was optimized at an energy dosage of 76.4(log 1.88)kJ/kg TS. During cell disintegration (ozone dosage 0.0011 mgO3/mgSS), chemical oxygen demand solubilization (COD) and SS reduction of sonic mediated ozone pretreated sludge were 25.4% and 17.8% comparatively higher than ozone pretreated sludge, respectively. Further, biogas production potential of control (raw), flocculated (ozone pretreated), and deflocculated (sonic mediated ozone pretreated) sludges were observed to be 0.202, 0.535 and 0.637 L/(gVS), respectively. Thus, the phase separated pretreatment at lower ultrasonic specific energy and low dose ozone proved to enhance the anaerobic biodegradability efficiently. Copyright © 2015 Elsevier B.V. All rights reserved.

PES-Kaolin Mixed Matrix Membranes for Arsenic Removal from Water

PubMed Central

Russo, Francesca; Rezzouk, Lina

2017-01-01

The aim of this work was the fabrication and the characterization of mixed matrix membranes (MMMs) for arsenic (As) removal from water. Membrane separation was combined with an adsorption process by incorporating the kaolin (KT2) Algerian natural clay in polymeric membranes. The effects of casting solution composition was explored using different amounts of polyethersufone (PES) as a polymer, polyvinyl-pyrrolidone (PVP K17) and polyethylene glycol (PEG 200) as pore former agents, N-methyl pyrrolidone (NMP) as a solvent, and kaolin. Membranes were prepared by coupling Non-solvent Induced Phase Separation and Vapour Induced Phase Separation (NIPS and VIPS, respectively). The influence of the exposure time to controlled humid air and temperature was also investigated. The MMMs obtained were characterized in terms of morphology, pore size, porosity, thickness, contact angle and pure water permeability. Adsorption membrane-based tests were carried out in order to assess the applicability of the membranes produced for As removal from contaminated water. Among the investigated kaolin concentrations (ranging from 0 wt % to 5 wt %), a content of 1.25 wt % led to the MMM with the most promising performance. PMID:28974009

Radiation-induced polymerization of glass forming systems. VI. Polymerization rate at higher conversion in binary systems

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

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-08-01

The effect of temperature and composition on the inflection point in the time-conversion curve and the saturated conversion was investigated in the gamma -radio-induced radical polymerization of binary systems consisting of a glass- forming monomer and a solvent. In the polymerization of completely homogeneous systems such as glycidyl methacrylate (GMA) -triacetin and hydroxyethyl methacrylate (HEMA) --propylene glycol systems, the time-conversion curve has an inflection point at polymerization temperatures between T/sub vm/(T/sub v/ of monomer system) and T/sub vp/ (T/sub v/ of polymer system). Such conversions at the inflection point changed monotonically between 0 and 100% in this temperature range. T/submore » v/ was found to be 30 to 50 deg C higher than T/sub g/ (glass transition temperature) and a monotonic function of composition (monomer -- polymer -- solvent). The acceleration effect continued to 100% conversion above T/sub vp/, and no acceleration effect was observed below T/sub vm/. The saturated conversion in homogeneous systems changed monotonically between 0 and 100% for polymerization temperatures between T/sub gm/ (T/sub g/ of monomer system) and T/sub gp/(T of polymer system). T/sub g/ was also a monotonic function of composition. No saturation in conversion was observed above T/sub gp/ , and no polymerization occurred below T/sub gm/. In the polymerization of completely heterogeneous systems such as HEMA-dioctyl phthalate, no acceleration effect was observed at any temperature and composition. The saturated conversion was 100% sbove T/sub g/ of pure HEMA, and no polymerization occurred below this temperature in this system. (auth)« less

Investigation of gamma-ray induced polymer formation of the carboranes. Annual progress report, November 1, 1972--September 30, 1973

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

Klingen, T.J.

1973-10-01

Research is reported on the radiation chemistry of o-carborane STA 1, 2- dicarba-closo-dodecaborane (11)! and its l-alkyl and 1-alkenyl derivatives. The principal purpose of the research is to establish optirmum conditions for radiation-induced polymerization of such compounds. Properties and structures of polymeric products, identities and yields of minor products, and reaction mechanisms are being determined. (auth)

Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA): New Insights and Opportunities.

PubMed

Yeow, Jonathan; Boyer, Cyrille

2017-07-01

The polymerization-induced self-assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo-PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo-PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo-PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self-assembly process. The purpose of this mini-review is therefore to examine some of these recent advances that have been made in Photo-PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.

Polymerization of the tubulin-colchicine complex: relation to microtubule assembly.

PubMed

Andreu, J M; Wagenknecht, T; Timasheff, S N

1983-03-29

The polymerization of purified tubulin-colchicine complex, which results in polymers different from microtubules under microtubule-promoting conditions, has been characterized. It proceeds as a nucleated condensation polymerization, requires Mg2+, and is inhibited by small concentrations of Ca2+. Polymerization requires GTP binding, but GDP is inhibitory. The GTPase activity proceeds, but it is unlinked to polymerization. The thermodynamic characteristics of the growth reaction, namely, the apparent changes of free energy, enthalpy, entropy, heat capacity, and preferential interaction with H+ and Mg2+, are very similar to those of microtubule assembly. It is proposed that the interactions responsible for the two types of polymerization are very similar and that the molecular mechanism of microtubule inhibition by colchicine may consist in a drug-induced distortion of the normal protomer bonding geometry.

Mobile phase additives for enhancing the chromatographic performance of astaxanthin on nonendcapped polymeric C30-bonded stationary phases.

PubMed

Kaiser, Philipp; Surmann, Peter; Fuhrmann, Herbert

2009-01-01

Astaxanthin shows peak deformation and reduced peak area response when eluted with methanol and methyl tert-butyl ether on nonendcapped polymeric C30-bonded HPLC phases. The present study tested different column manufacturers, column batches, and ten mobile phase additives including acids, bases, buffers, complexing and antioxidant agents for improvement of peak shape and peak area response. Concerning chromatographic benefits and feasibility, ammonium acetate was found to be the best additive followed by triethylamine for all columns tested. Variation of the mobile phase pH equivalent and the column temperature showed no synergistic effects on peak shape and peak area response. Results indicate that peak tailing and variation of peak area response are due to different on-column effects. Possible mechanisms of the observed phenomenon will be discussed.

Preparation of end-grafted polymer brushes by nitroxide-mediated free radical polymerization of vaporized vinyl monomers.

PubMed

Li, Jun; Chen, Xiaoru; Chang, Ying-Chih

2005-10-11

In this work, we report a gas-phase polymerization approach to create end-grafted vinyl based polymer films on silicon oxide based substrates. The "surface-initiated vapor deposition polymerization" (SI-VDP) of vaporized vinyl monomers, via the nitroxide-mediated free radical polymerization mechanism, was developed to fabricate various homo- and block copolymer brushes from surface-bound initiators, 1-(4'-oxa-2'-phenyl-12'-trimethoxysilyldodecyloxy)-2,2,6,6-tetra-methylpiperidine ("TEMPO"). The resulting polymer thin films were characterized by the Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry, and contact angle goniometry, respectively, to identify the surface composition, film thickness, surface coverage, and water contact angles. Through the SI-VDP, end-grafted polymer films of polystyrene (PSt), poly(acrylic acid) (PAAc), poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), and poly(N-isopropylacrylamide) (PNIPAAm) with 10-200 nm thicknesses were fabricated. Furthermore, the block copolymer films of PAAc (1st block)-b-PSt (2nd block), PSt (1st block)-b-PAAc (2nd block), and a triblock copolymer film of PAAc (1st)-b-PSt (2nd)-b-PHPMA (3rd), were also fabricated, suggesting the "renewability" of the TEMPO-initiated polymerization in the SI-VDP scheme. It is also noticed that the SI-VDP is more efficient than the conventional solution phase polymerization in producing functional polymer brushes such as PNIPAAm, PAAc, or PAAc-b-PSt end-grafted films. In summary, our studies have shown clear advantages of the SI-VDP setup for the nitroxide-mediated polymerization scheme in controlling synthesis of end-grafted homo- and copolymer thin films.

Radical-induced generation of small silver particles in SPEEK/PVA polymer films and solutions: UV-Vis, EPR, and FT-IR studies.

PubMed

Korchev, A S; Konovalova, T; Cammarata, V; Kispert, L; Slaten, L; Mills, G

2006-01-03

The present study is centered on the processes involved in the photochemical generation of nanometer-sized Ag particles via illumination at 350 nm of aqueous solutions and cross linked films containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol). Optical and electron paramagnetic resonance experiments, including electron nuclear double resonance data, proved conclusively that the photogenerated chromophore exhibiting a band with lambda(max) = 565 nm is an alpha-hydroxy aromatic (ketyl) radical of the polymeric ketone. This reducing species was produced by illumination of either solutions or films, but the radical lifetime extended from minutes in the fluid phase to hours in the solid. Direct evidence is presented that this long-lived chromophore reduces Ag(I), Cu(II), and Au(III) ions in solution. A rate constant of k = 1.4 x 10(3) M(-)(1) s(-)(1) was obtained for the reduction of Ag(+) by the ketyl radical from the post-irradiation formation of Ag crystallites. FTIR results confirmed that the photoprocess yielding polymeric ketyl radicals involves a reaction between the macromolecules. The photochemical oxidation of the polymeric alcohol, as well as the formation of light-absorbing macromolecular products and polyols, indicates that the sulfonated polyketone experienced transformations similar to those encountered during illumination of the benzophenone/2-propanol system.

Tetra(p-tolyl)borate-functionalized solvent polymeric membrane: a facile and sensitive sensing platform for peroxidase and peroxidase mimetics.

PubMed

Wang, Xuewei; Qin, Wei

2013-07-22

The determination of peroxidase activities is the basis for enzyme-labeled bioaffinity assays, peroxidase-mimicking DNAzymes- and nanoparticles-based assays, and characterization of the catalytic functions of peroxidase mimetics. Here, a facile, sensitive, and cost-effective solvent polymeric membrane-based peroxidase detection platform is described that utilizes reaction intermediates with different pKa values from those of substrates and final products. Several key but long-debated intermediates in the peroxidative oxidation of o-phenylenediamine (o-PD) have been identified and their charge states have been estimated. By using a solvent polymeric membrane functionalized by an appropriate substituted tetraphenylborate as a receptor, those cationic intermediates could be transferred into the membrane from the aqueous phase to induce a large cationic potential response. Thus, the potentiometric indication of the o-PD oxidation catalyzed by peroxidase or its mimetics can be fulfilled. Horseradish peroxidase has been detected with a detection limit at least two orders of magnitude lower than those obtained by spectrophotometric techniques and traditional membrane-based methods. As an example of peroxidase mimetics, G-quadruplex DNAzymes were probed by the intermediate-sensitive membrane and a label-free thrombin detection protocol was developed based on the catalytic activity of the thrombin-binding G-quadruplex aptamer. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Two-Phase Pilot Study to Evaluate the Safety and Tolerability of an In Situ Polymerizing Collagen.

PubMed

Inglefield, Christopher; Rone-McCrate, Rebecca; Brooks, Robert; Zhu, Jiaxun; Grant, Sheila; DeVore, Dale P

2017-09-01

Demand for collagen-based fillers has declined primarily because of limited long-term clinical benefit and the introduction of hyaluronic acid compositions. In situ polymerizing collagen is a noncrosslinked solution of porcine collagen containing a collagenase shield that undergoes fibrillogenesis on injected into tissues forming a natural matrix. Conduct a prospective, single-center, dual-phase open-label study in 8 subjects to evaluate the safety, tolerability, and efficacy of the porcine collagen composition. In Phase I, potential hypersensitivity of the collagen composition was evaluated after skin testing in the back (men) or forearms of subjects (women). In Phase II, subjects showing no signs of hypersensitivity received collagen injections into the nasolabial area followed by evaluation at 1, 4, 8, and 12 weeks using the Global Aesthetic Improvement Scale. None of the subjects had signs of hypersensitivity and all continued in Phase II. The treating physician(s) reported no post-treatment adverse events. Improvement of the nasolabial fold was observed by the physicians and confirmed by assessment of high-resolution photographs and Global Aesthetic Improvement Scale scores over the 12-week treatment were maintained. In this pilot clinical study in situ polymerizing collagen was shown to be safe and effective throughout the 3-month study period.

Surfactant-Induced Ordering and Wetting Transitions of Droplets of Thermotropic Liquid Crystals “Caged” Inside Partially Filled Polymeric Capsules

PubMed Central

2015-01-01

We report a study of the wetting and ordering of thermotropic liquid crystal (LC) droplets that are trapped (or “caged”) within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of “free” LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ < 85°). The wetting transitions induced by SDS also resulted in changes in the internal ordering of the LC to yield states topologically equivalent to axial and radial configurations. Although topologically equivalent to free droplets, the contributions that surface anchoring, LC elasticity, and topological defects make to the free energy of caged LC droplets differ from those of free droplets. Overall, these results and others reported herein lead us to conclude that caged LC droplets offer a platform for new designs of LC-droplet-based responsive soft matter that cannot be realized in dispersions of free droplets. PMID:24911044

Disorder induced spin coherence in polyfluorene thin film semiconductors

NASA Astrophysics Data System (ADS)

Miller, Richard G.; van Schooten, Kipp; Malissa, Hans; Waters, David P.; Lupton, John M.; Boehme, Christoph

2014-03-01

Charge carrier spins in polymeric organic semiconductors significantly influence magneto-optoelectronic properties of these materials. In particular, spin relaxation times influence magnetoresistance and electroluminescence. We have studied the role of structural and electronic disorder in polaron spin-relaxation times. As a model polymer, we used polyfluorene, which can exist in two distinct morphologies: an amorphous (glassy) and an ordered (beta) phase. The phases can be controlled in thin films by preparation parameters and verified by photoluminescence spectroscopy. We conducted pulsed electrically detected magnetic resonance (pEDMR) measurements to determine spin-dephasing times by transient current measurements under bipolar charge carrier injection conditions and a forward bias. The measurements showed that, contrary to intuition, spin-dephasing times increase with material disorder. We attribute this behavior to a reduction in hyperfine field strength for carriers in the glassy phase due to increased structural disorder in the hydrogenated side chains, leading to longer spin coherence times. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

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

PubMed

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

2012-11-01

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

Autocatalytic polymerization generates persistent random walk of crawling cells.

PubMed

Sambeth, R; Baumgaertner, A

2001-05-28

The autocatalytic polymerization kinetics of the cytoskeletal actin network provides the basic mechanism for a persistent random walk of a crawling cell. It is shown that network remodeling by branching processes near the cell membrane is essential for the bimodal spatial stability of the network which induces a spontaneous breaking of isotropic cell motion. Details of the phenomena are analyzed using a simple polymerization model studied by analytical and simulation methods.

In situ chemical oxidative polymerization preparation of poly(3,4-ethylenedioxythiophene)/graphene nanocomposites with enhanced thermoelectric performance.

PubMed

Xu, Kongli; Chen, Guangming; Qiu, Dong

2015-05-01

Three different in situ chemical oxidative polymerization routes, that is, (A) spin-coating and subsequent liquid layer polymerization, (B) spin-coating followed by vapor phase polymerization, and (C) in situ polymerization and then post-treatment by immersion in ethylene glycol (EG), have been developed to achieve poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (PEDOT/rGO) nanocomposites. As demonstrated by scanning electron microscopic and energy-dispersive X-ray spectroscopic techniques, PEDOT has been successfully coated on the surface of the rGO nanosheets by each of the three preparation routes. Importantly, all of the nanocomposites display a greatly enhanced thermoelectric performance (power factors) relative to those of the corresponding neat PEDOT. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of a non-thermal, atmospheric-pressure, plasma brush on conversion of model self-etch adhesive formulations compared to conventional photo-polymerization

PubMed Central

Chen, Mingsheng; Zhang, Ying; Yao, Xiaomei; Li, Hao; Yu, Qingsong; Wang, Yong

2012-01-01

Objective To determine the effectiveness and efficiency of non-thermal, atmospheric plasmas for inducing polymerization of model dental self-etch adhesives. Methods The monomer mixtures used were bis-[2-(methacryloyloxy)ethyl] phosphate (2MP) and 2-hydroxyethyl methacrylate (HEMA), with mass ratios of 70/30, 50/50 and 30/70. Water was added to the above formulations: 10–30 wt%. These monomer/water mixtures were treated steadily for 40 s under a non-thermal atmospheric plasma brush working at temperatures from 32° to 35°C. For comparison, photo-initiators were added to the above formulations for photo-polymerization studies, which were light-cured for 40 s. The degree of conversion (DC) of both the plasma- and light-cured samples was measured using FTIR spectroscopy with an attenuated total reflectance attachment. Results The non-thermal plasma brush was effective in inducing polymerization of the model self-etch adhesives. The presence of water did not negatively affect the DC of plasma-cured samples. Indeed, DC values slightly increased, with increasing water content in adhesives: from 58.3% to 68.7% when the water content increased from 10% to 30% in the adhesives with a 50/50 (2MP/HEMA) mass ratio. Conversion values of the plasma-cured groups were higher than those of light-cured samples with the same mass ratio and water content. Spectral differences between the plasma- and light-cured groups indicate subtle structural distinctions in the resultant polymer networks. Significance This research if the first to demonstrate that the non-thermal plasma brush induces polymerization of model adhesives under clinical settings by direct/indirect energy transfer. This device shows promise for polymerization of dental composite restorations having enhanced properties and performance. PMID:23018084

Smart polyaniline nanoparticles with thermal and photothermal sensitivity

NASA Astrophysics Data System (ADS)

Bongiovanni Abel, Silvestre; Molina, María A.; Rivarola, Claudia R.; Kogan, Marcelo J.; Barbero, Cesar A.

2014-12-01

Conductive polyaniline nanoparticles (PANI NPs) are synthesized by oxidation of aniline with persulfate in acid media, in the presence of polymeric stabilizers: polyvinilpyrrolidone (PVP), poly(N-isopropylacrylamide) (PNIPAM), and hydroxylpropylcellulose (HPC). It is observed that the size of the nanoparticles obtained depends on the polymeric stabilizer used, suggesting a mechanism where the aggregation of polyaniline molecules is arrested by adsorption of the polymeric stabilizer. Indeed, polymerization in the presence of a mixture of two polymers having different stabilizing capacity (PVP and PNIPAM) allows tuning of the size of the nanoparticles. Stabilization with biocompatible PVP, HPC and PNIPAM allows use of the nanoparticle dispersions in biological applications. The nanoparticles stabilized by thermosensitive polymers (PNIPAM and HPC) aggregate when the temperature exceeds the phase transition (coil to globule) temperature of each stabilizer (Tpt = 32 °C for PNIPAM or Tpt = 42 °C for HPC). This result suggests that an extended coil form of the polymeric stabilizer is necessary to avoid aggregation. The dispersions are reversibly restored when the temperature is lowered below Tpt. In that way, the effect could be used to separate the nanoparticles from soluble contaminants. On the other hand, the PANI NPs stabilized with PVP are unaffected by the temperature change. UV-visible spectroscopy measurements show that the nanoparticle dispersion changes their spectra with the pH of the external solution, suggesting that small molecules can easily penetrate the stabilizer shell. Near infrared radiation is absorbed by PANI NPs causing an increase of their temperature which induces the collapse of the thermosensitive polymer shell and aggregation of the NPs. The effect reveals that it is possible to locally heat the nanoparticles, a phenomenon that can be used to destroy tumor cells in cancer therapy or to dissolve protein aggregates of neurodegenerative diseases (e.g. Alzheimer). Moreover, the long range control of aggregation can be used to modulate the nanoparticle residence inside biological tissues.

Isolation of a 5-Kilodalton Actin-Sequestering Peptide from Human Blood Platelets

NASA Astrophysics Data System (ADS)

Safer, Daniel; Golla, Rajasree; Nachmias, Vivianne T.

1990-04-01

Resting human platelets contain ≈0.3 mM unpolymerized actin. When freshly drawn and washed platelets are treated with saponin, 85-90% of the unpolymerized actin diffuses out. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions shows that the bulk of this unpolymerized actin migrates with a higher mobility than does pure G-actin, profilactin, or actin-gelsolin complex. When muscle G-actin is added to fresh or boiled saponin extract, the added muscle actin is shifted to the high-mobility form. The saponin extract contains an acidic peptide having a molecular mass in the range of 5 kDa, which has been purified to homogeneity by reverse-phase HPLC. This peptide also shifts muscle actin to the high-mobility form. Addition of either boiled saponin extract or the purified peptide to muscle G-actin also strongly and stoichiometrically inhibits salt-induced polymerization, as assayed by falling-ball viscometry and by sedimentation. We conclude that this peptide binds to the bulk of the unpolymerized actin in platelets and prevents it from polymerizing.

Rapid analysis of water- and fat-soluble vitamins by electrokinetic chromatography with polymeric micelle as pseudostationary phase.

PubMed

Ni, Xinjiong; Xing, Xiaoping; Cao, Yuhua; Cao, Guangqun

2014-11-28

A novel polymeric micelle, formed by random copolymer poly (stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) has been used as pseudostationary phase (PSP) in electrokinetic chromatography (EKC) for simultaneous and rapid determination of 11 kinds of water- and fat-soluble vitamins in this work. The running buffer consisting of 1% (w/v) P(SMA-co-MAA), 10% (v/v) 1-butanol, 20% (v/v) acetonitrile, and 30 mM Palitzsch buffer solution (pH 9.2) was applied to improve the selectivity and efficiency, as well as to shorten analysis time. 1-Butanol and acetonitrile as the organic solvent modifiers played the most important roles for rapid separation of these vitamins. The effects of organic solvents on microstructure of the polymeric micelle were investigated. The organic solvents swell the polymeric micelle by three folds, lower down the surface charge density and enhance the microenviromental polarity of the polymeric micelle. The 11 kinds of water- and fat-soluble vitamins could be baseline separated within 13 min. The method was applied to determine water- and fat-soluble vitamins in commercial vitamin sample; the recoveries were between 93% and 111% with the relative standard derivations (RSDs) less than 5%. The determination results matched the label claim. Copyright © 2014 Elsevier B.V. All rights reserved.

Industrially relevant epoxy-acrylate hybrid resin photopolymerizations

NASA Astrophysics Data System (ADS)

Ajiboye, Gbenga I.

Photopolymerization of epoxy-acrylate hybrid resins takes advantages of inherent properties present in the free-radical and cationic reactions to reduce oxygen inhibition problems that plague free-radical reactions. Similarly, the combined reaction mechanisms reduce moisture sensitivity of the cationic reactions. Despite the advantages of epoxy-acrylate hybrid resins, problems persist that need to be addressed. For example, low conversion and polymerization rate of the epoxides are a problem, because the fast acrylate conversion prevents the epoxide from reaching high conversion. Controlling phase separation is challenging, since two moieties with different properties are reacting. The physical properties of the polymer will be impacted by the availability of different moieties. High shrinkage stress results from the acrylate moiety, causing buckling and cracking in film and coating applications. The overall goal of this study is to use the fundamental knowledge of epoxy-acrylate hybrid resins to formulate industrially viable polymers. In order to achieve this goal, the study focuses on the following objectives: (I) determine the apparent activation energy of the hybrid monomer METHB, (II) increase epoxide conversion and polymerization rate of hybrid formulations, and (III) control physical properties in epoxy-acrylate hybrid resins. In order to increase the epoxide conversion and rate of polymerization, the sensitivity of epoxides to alcohol is used to facilitate the activated monomer (AM) mechanism and induce a covalent bond between the epoxide and acrylate polymers through the hydroxyl group. It is hypothesized that if the AM mechanism is facilitated, epoxide conversion will increase. As a result, the resins can be tailored to control phase separation and physical properties, and shrinkage stress can be reduced. In pursuit of these objectives, the hybrid monomer METHB was polymerized at temperatures ranging from 30°C to 70°C to obtain apparent activation energy of 23.49 kJ/mol for acrylate and 57 kJ/mol for epoxide moeities. Then, hybrid systems pairing hydroxyl-containing acrylates with epoxides were formulated to promote the faster AM mechanism. Monomer composition was changed in the presence of hydroxyl-containing acrylate, and initiators were carefully selected in order to control phase separation. The conversion of acrylate and epoxide was monitored in real time by Raman spectroscopy. The physical and mechanical properties were monitored using dynamic mechanical analysis. Epoxide conversion and rate of polymerization in epoxide-acrylate hybrid monomer systems were shown to increase through the introduction of a hydroxyl group on the meth/acrylate monomer, taking advantage of the faster AM mechanism. In addition, this covalent bond linking the epoxide network to the meth/acrylate polymer chains resulted in little or no phase separation and a reduction of the Tg for the hybrid polymer compared to the neat epoxide. Fundamental knowledge gained from this research will enable the use of epoxy-acrylate hybrid resins in variety of applications. For instance, shrinkage may be reduced in dental fillings, noise and vibration problems in aircraft and other machinery may be controlled, and photopolymerization cost could be reduced in thin film applications.

Actin polymerization plays a significant role in asbestos-induced inflammasome activation in mesothelial cells in vitro.

PubMed

MacPherson, Maximilian; Westbom, Catherine; Kogan, Helen; Shukla, Arti

2017-05-01

Asbestos exposure leads to malignant mesothelioma (MM), a deadly neoplasm of mesothelial cells of various locations. Although there is no doubt about the role of asbestos in MM tumorigenesis, mechanisms are still not well explored. Recently, our group demonstrated that asbestos causes inflammasome priming and activation in mesothelial cells, which in part is dependent on oxidative stress. Our current study sheds light on yet another mechanism of inflammasome activation by asbestos. Here we show the role of actin polymerization in asbestos-induced activation of the nod-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome. Using human mesothelial cells, we first demonstrate that asbestos and carbon nanotubes induced caspase-1 activation and high-mobility group box 1, interleukin 1 beta and interleukin 18 secretion was blocked by Cytochalasin D (Cyto D) an actin polymerization inhibitor. Next, to understand the mechanism, we assessed whether phagocytosis of fibers by mesothelial cells is affected by actin polymerization inhibition. Transmission electron microscopy showed the inhibition of fiber uptake by mesothelial cells in the presence of Cyto D. Furthermore, localization of components of the inflammasome, apoptotic speck-like protein containing a CARD domain (ASC) and NLRP3, to the perinuclear space in mitochondria or endoplasmic reticulum in response to fiber exposure was also interrupted in the presence of Cyto D. Taken together, our studies suggest that actin polymerization plays important roles in inflammasome activation by fibers via regulation of phagocytosis and/or spatial localization of inflammasome components.

Analysis of beer volatiles by polymeric imidazolium-solid phase microextraction coatings: Synthesis and characterization of polymeric imidazolium ionic liquids.

PubMed

González-Álvarez, Jaime; Blanco-Gomis, Domingo; Arias-Abrodo, Pilar; Pello-Palma, Jairo; Ríos-Lombardía, Nicolás; Busto, Eduardo; Gotor-Fernández, Vicente; Gutiérrez-Álvarez, María Dolores

2013-08-30

Two polymeric ionic liquids, 3-(but-3″-en-1″-yl)-1-[2'-hydroxycyclohexyl]-1H-imidazol-3-ium bis(trifluoromethanesulfonyl)imide (IL-1) and 1-(2'-hydroxycyclohexyl)-3-(4″-vinylbenzyl)-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)imide (IL-2), have been synthesized by a free radical polymerization reaction and used as coatings for solid-phase microextraction (SPME). These new fibers exhibit good film stability, high thermal stability (270-290°C) and long lifetimes, and are used for the extraction of volatile compounds in lemon beer using gas chromatography separation and flame ionization detection. The scanning electron micrographs of the fiber surface revealed a polymeric ionic liquid (PIL) film, which is distributed homogeneously on the fiber. The developed PIL fiber showed good linearity between 50 and 2000μg/L with regression coefficients in the range of 0.996-0.999. The relative standard deviations (RSD) obtained in the peak area were found to vary between 1% and 12%, which assured that adequate repeatability was achieved. The spiked recoveries for three beer samples ranged from 78.4% to 123.6%. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The polymeric IL-1 butenyl fiber showed a greater efficiency compared to the PDMS-DVB (65μm) and CAR-PDMS (75μm) for the extraction of all of the analytes studied. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Small-volume resuscitation from hemorrhagic shock with polymerized human serum albumin.

PubMed

Messmer, Catalina; Yalcin, Ozlem; Palmer, Andre F; Cabrales, Pedro

2012-10-01

Human serum albumin (HSA) is used as a plasma expander; however, albumin is readily eliminated from the intravascular space. The objective of this study was to establish the effects of various-sized polymerized HSAs (PolyHSAs) during small-volume resuscitation from hemorrhagic shock on systemic parameters, microvascular hemodynamics, and functional capillary density in the hamster window chamber model. Polymerized HSA size was controlled by varying the cross-link density (ie, molar ratio of glutaraldehyde to HSA). Hemorrhage was induced by controlled arterial bleeding of 50% of the animal's blood volume (BV), and hypovolemic shock was maintained for 1 hour. Resuscitation was implemented in 2 phases, first, by infusion of 3.5% of the BV of hypertonic saline (7.5% NaCl) then followed by infusion of 10% of the BV of each PolyHSA. Resuscitation provided rapid recovery of blood pressure, blood gas parameters, and microvascular perfusion. Polymerized HSA at a glutaraldehyde-to-HSA molar ratio of 60:1 (PolyHSA(60:1)) provided superior recovery of blood pressure, microvascular blood flow, and functional capillary density, and acid-base balance, with sustained volume expansion in relation to the volume infused. The high molecular weight of PolyHSA(60:1) increased the hydrodynamic radius and solution viscosity. Pharmacokinetic analysis of PolyHSA(60:1) indicates reduced clearance and increased circulatory half-life compared with monomeric HSA and other PolyHSA formulations. In conclusion, HSA molecular size and solution viscosity affect central hemodynamics, microvascular blood flow, volume expansion, and circulation persistence during small-volume resuscitation from hemorrhagic shock. In addition, PolyHSA can be an alternative to HSA in pathophysiological situations with compromised vascular permeability. Copyright © 2012 Elsevier Inc. All rights reserved.

Oil-in-oil emulsions: a unique tool for the formation of polymer nanoparticles.

PubMed

Klapper, Markus; Nenov, Svetlin; Haschick, Robert; Müller, Kevin; Müllen, Klaus

2008-09-01

Polymer latex particles are nanofunctional materials with widespread applications including electronics, pharmaceuticals, photonics, cosmetics, and coatings. These materials are typically prepared using waterborne heterogeneous systems such as emulsion, miniemulsion, and suspension polymerization. However, all of these processes are limited to water-stable catalysts and monomers mainly polymerizable via radical polymerization. In this Account, we describe a method to overcome this limitation: nonaqueous emulsions can serve as a versatile tool for the synthesis of new types of polymer nanoparticles. To form these emulsions, we first needed to find two nonmiscible nonpolar/polar aprotic organic solvents. We used solvent mixtures of either DMF or acetonitrile in alkanes and carefully designed amphiphilic block and statistical copolymers, such as polyisoprene- b-poly(methyl methacrylate) (PI- b-PMMA), as additives to stabilize these emulsions. Unlike aqueous emulsions, these new emulsion systems allowed the use of water-sensitive monomers and catalysts. Although polyaddition and polycondensation reactions usually lead to a large number of side products and only to oligomers in the aqueous phase, these new conditions resulted in high-molecular-weight, defect-free polymers. Furthermore, conducting nanoparticles were produced by the iron(III)-induced synthesis of poly(ethylenedioxythiophene) (PEDOT) in an emulsion of acetonitrile in cyclohexane. Because metallocenes are sensitive to nitrile and carbonyl groups, the acetonitrile and DMF emulsions were not suitable for carrying out metallocene-catalyzed olefin polymerization. Instead, we developed a second system, which consists of alkanes dispersed in perfluoroalkanes. In this case, we designed a new amphipolar polymeric emulsifier with fluorous and aliphatic side chains to stabilize the emulsions. Such heterogeneous mixtures facilitated the catalytic polymerization of ethylene or propylene to give spherical nanoparticles of high molecular weight polyolefins. These nonaqueous systems also allow for the combination of different polymerization techniques to obtain complex architectures such as core-shell structures. Previously, such structures primarily used vinylic monomers, which greatly limited the number of polymer combinations. We have demonstrated how nonaqueous emulsions allow the use of a broad variety of hydrolyzable monomers and sensitive catalysts to yield polyester, polyurethane, polyamide, conducting polymers, and polyolefin latex particles in one step under ambient reaction conditions. This nonpolar emulsion strategy dramatically increases the chemical palette of polymers that can form nanoparticles via emulsion polymerization.

Incorporation of ionic liquid into porous polymer monoliths to enhance the separation of small molecules in reversed-phase high-performance liquid chromatography.

PubMed

Wang, Jiafei; Bai, Ligai; Wei, Zhen; Qin, Junxiao; Ma, Yamin; Liu, Haiyan

2015-06-01

An ionic liquid was incorporated into the porous polymer monoliths to afford stationary phases with enhanced chromatographic performance for small molecules in reversed-phase high-performance liquid chromatography. The effect of the ionic liquid in the polymerization mixture on the performance of the monoliths was studied in detail. While monoliths without ionic liquid exhibited poor resolution and low efficiency, the addition of ionic liquid to the polymerization mixture provides highly increased resolution and high efficiency. The chromatographic performances of the monoliths were demonstrated by the separations of various small molecules including aromatic hydrocarbons, isomers, and homologues using a binary polar mobile phase. The present column efficiency reached 27 000 plates/m, which showed that the ionic liquid monoliths are alternative stationary phases in the separation of small molecules by high-performance liquid chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inducible recruitment of Cdc42 or WASP to a cell-surface receptor triggers actin polymerization and filopodium formation.

PubMed

Castellano, F; Montcourrier, P; Guillemot, J C; Gouin, E; Machesky, L; Cossart, P; Chavrier, P

1999-04-08

Cdc42, a GTP-binding protein of the Rho family, controls actin cytoskeletal organization and helps to generate actin-based protruding structures, such as filopodia. In vitro, Cdc42 regulates actin polymerization by facilitating the creation of free barbed ends - the more rapidly growing ends of actin filaments - and subsequent elongation at these ends. The Wiskott- Aldrich syndrome protein, WASP, which has a pleckstrin-homology domain and a Cdc42/Rac-binding motif, has been implicated in cell signaling and cytoskeleton reorganization. We have investigated the consequences of local recruitment of activated Cdc42 or WASP to the plasma membrane. We used an activated Cdc42 protein that could be recruited to an engineered membrane receptor by adding rapamycin as a bridge, and added antibody-coupled beads to aggregate these receptors. Inducible recruitment of Cdc42 to clusters of receptors stimulated actin polymerization, resulting in the formation of membrane protrusions. Cdc42-induced protrusions were enriched in the vasodilator-stimulated phosphoprotein VASP and the focal-adhesion-associated proteins zyxin and ezrin. The Cdc42 effector WASP could also induce the formation of protrusions, albeit of different morphology. This is the first demonstration that the local recruitment of activated Cdc42 or its downstream effector, WASP, to a membrane receptor in whole cells is sufficient to trigger actin polymerization that results in the formation of membrane protrusions. Our data suggest that Cdc42-induced actin-based protrusions result from the local and serial recruitment of cytoskeletal proteins including zyxin, VASP, and ezrin.

Development, optimisation and application of polyurethane foams as new polymeric phases for stir bar sorptive extraction.

PubMed

Neng, N R; Pinto, M L; Pires, J; Marcos, P M; Nogueira, J M F

2007-11-09

In this contribution, polyurethane foams are proposed as new polymeric phases for stir bar sorptive extraction (SBSE). Assays performed for polyurethane synthesis demonstrated that four series of formulations (P(1), P(2), P(3) and P(4)) present remarkable stability and excellent mechanical resistance to organic solvents. For polymer clean-up treatment, acetonitrile proved to be the best solvent under sonification, ensuring the reduction of the contamination and interferences. SBSE assays performed on these polyurethane polymers followed by liquid desorption and high-performance liquid chromatography-diode array detection (LD-HPLC-DAD) or large volume injection-capillary gas chromatography-mass spectrometry (LD-LVI-GC-MS), showed that P(2) presents the best recovery yields for atrazine, 2,3,4,5-tetrachlorophenol and fluorene, used as model compounds in water samples at a trace level. SBSE(P(2)) assays performed on this polymer mixed up with several adsorbent materials, i.e. activated carbon, a mesoporous material and a calixarene, did not bring any advantages in relation with the polymeric matrix alone. The comparison between assays performed by SBSE(P(2)) and by the conventional SBSE(PDMS) showed much better performance for the former phase on aqueous samples spiked with atrazine, 2,3,4,5-tetrachlorophenol and fluorene, in which the foremost two analytes present recovery values 3- and 10-fold higher, respectively. The polyurethanes proposed as new polymeric phases for SBSE provided powerful capabilities for the enrichment of organic compounds from aqueous matrices, showing to be indicated mainly in the case of the more polar analytes.

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.

A Hybrid Nanomaterial for the Controlled Generation of Free Radicals and Oxidative Destruction of Hypoxic Cancer Cells.

PubMed

Shen, Song; Zhu, Chunlei; Huo, Da; Yang, Miaoxin; Xue, Jiajia; Xia, Younan

2017-07-17

Anticancer modalities based on oxygen free radicals, including photodynamic therapy and radiotherapy, have emerged as promising treatments in the clinic. However, the hypoxic environment in tumor tissue prevents the formation of oxygen free radicals. Here we introduce a novel strategy that employs oxygen-independent free radicals generated from a polymerization initiator for eradicating cancer cells. The initiator is mixed with a phase-change material and loaded into the cavities of gold nanocages. Upon irradiation by a near-infrared laser, the phase-change material is melted due to the photothermal effect of gold nanocages, leading to the release and decomposition of the loaded initiator to generate free radicals. The free radicals produced in this way are highly effective in inducing apoptosis in hypoxic cancer cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of Polysulfone Membranes Prepared with Thermally Induced Phase Separation Technique

NASA Astrophysics Data System (ADS)

Tiron, L. G.; Pintilie, Ș C.; Vlad, M.; Birsan, I. G.; Baltă, Ș

2017-06-01

Abstract Membrane technology is one of the most used water treatment technology because of its high removal efficiency and cost effectiveness. Preparation techniques for polymer membranes show an important aspect of membrane properties. Generally, polysulfone (PSf) and polyethersulfone (PES) are used for the preparation of ultrafiltration (UF) membranes. Polysulfone (PSf) membranes have been widely used for separation and purification of different solutions because of their excellent chemical and thermal stability. Polymeric membranes were obtained by phase inversion method. The polymer solution introduced in the nonsolvent bath (distilled water) initiate the evaporation of the solvent from the solution, this phenomenon has a strong influence on the transport properties. The effect of the coagulation bath temperature on the membrane properties is of interest for this study. Membranes are characterized by pure water flux, permeability, porosity and retention of methylene blue. The low temperature of coagulation bath improve the membrane’s rejection and its influence was most notable.

Proanthocyanidins from grape seeds promote proliferation of mouse hair follicle cells in vitro and convert hair cycle in vivo.

PubMed

Takahashi, T; Kamiya, T; Yokoo, Y

1998-11-01

For the purpose of discovering natural products which possess hair growing activity, we examined about 1000 kinds of plant extracts concerning growth-promoting activity with respect to hair follicle cells. After an extensive search, we discovered that proanthocyanidins extracted from grape seeds promote proliferation of hair follicle cells isolated from mice by about 230% relative to controls (100%); and that proanthocyanidins possess remarkable hair-cycle-converting activity from the telogen phase to the anagen phase in C3H mice in vivo test systems. The profile of the active fraction of the proanthocyanidins was elucidated by thiolytic degradation and tannase hydrolysis. We found that the constitutive monomers were epicatechin and catechin; and that the degree of polymerization was 3.5. We demonstrated the possibility of using the proanthocyanidins extracted from grape seeds as agents inducing hair growth.

Nanoconfinement: an effective way to enhance PVDF piezoelectric properties.

PubMed

Cauda, Valentina; Stassi, Stefano; Bejtka, Katarzyna; Canavese, Giancarlo

2013-07-10

The dimensional confinement and oriented crystallization are both key factors in determining the piezoelectric properties of a polymeric nanostructured material. Here we prepare arrays of one-dimensional polymeric nanowires showing piezoelectric features by template-wetting two distinct polymers into anodic porous alumina (APA) membranes. In particular, poly(vinylidene fluoride), PVDF, and its copolymer poly(vinylidene fluoride-trifluoroethylene), PVTF, are obtained in commercially available APA, showing a final diameter of about 200 nm and several micrometers in length, reflecting the templating matrix features. We show that the crystallization of both polymers into a ferroelectric phase is directed by the nanotemplate confinement. Interestingly, the PVDF nanowires mainly crystallize into the β-phase in the nanoporous matrix, whereas the reference thin film of PVDF crystallizes in the α nonpolar phase. In the case of the PVTF nanowires, needle-like crystals oriented perpendicularly to the APA channel walls are observed, giving insight on the molecular orientation of the polymer within the nanowire structure. A remarkable piezoelectric behavior of both 1-D polymeric nanowires is observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. In particular, an outstanding piezoelectric effect is observed for the PVDF nanowires with respect to the polymeric thin film, considering that no poling was carried out. Current versus voltage (I-V) characteristics showed a consistent switching behavior of the ferroelectric polar domains, thus revealing the importance of the confined and oriented crystallization of the polymer in monodimensional nanoarchitectures.

HPLC separation of triacylglycerol positional isomers on a polymeric ODS column.

PubMed

Kuroda, Ikuma; Nagai, Toshiharu; Mizobe, Hoyo; Yoshimura, Nobuhito; Gotoh, Naohiro; Wada, Shun

2008-07-01

A polymeric ODS column was applied to the resolution of triacylglycerol positional isomers (TAG-PI), i.e. 1,3-dioleoyl-2-palmitoyl-glycerol (OPO) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), with a recycle HPLC system. To investigate the ODS column species and the column temperatures for the resolution of a TAG-PI pair, a mixture of OPO and OOP was subjected to an HPLC system equipped with a non-endcapped polymeric, endcapped monomeric, endcapped intermediate, or non-endcapped monomeric ODS column at three different column temperatures (40, 25, or 10 degrees C). Only the non-endcapped polymeric ODS column achieved the separation of OPO and OOP, and the lowest column temperature (10 degrees C) showed the best resolution for them. The other pair of TAG-PI, a mixture of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO) was also subjected to the system equipped with a non-endcapped polymeric or monomeric ODS column at five different column temperatures (40, 32, 25, 17, and 10 degrees C). Thus, POP and PPO were also separated on only the non-endcapped polymeric ODS column at 25 degrees C. However, no clear peak appeared at 10 degrees C. These results would indicate that the polymeric ODS stationary phase has an ability to recognize the structural differences between TAG-PI pairs. Also, the column temperature is a very important factor for separating the TAG-PI pair, and the optimal temperature would relate to the solubility of TAG-PI in the mobile phase. Furthermore, the recycle HPLC system provided measurements for the separation and analysis of TAG-PI pairs.

Light-Directed Tuning of Plasmon Resonances via Plasmon-Induced Polymerization Using Hot Electrons

PubMed Central

2017-01-01

The precise morphology of nanoscale gaps between noble-metal nanostructures controls their resonant wavelengths. Here we show photocatalytic plasmon-induced polymerization can locally enlarge the gap size and tune the plasmon resonances. We demonstrate light-directed programmable tuning of plasmons can be self-limiting. Selective control of polymer growth around individual plasmonic nanoparticles is achieved, with simultaneous real-time monitoring of the polymerization process in situ using dark-field spectroscopy. Even without initiators present, we show light-triggered chain growth of various monomers, implying plasmon initiation of free radicals via hot-electron transfer to monomers at the Au surface. This concept not only provides a programmable way to fine-tune plasmons for many applications but also provides a window on polymer chemistry at the sub-nanoscale. PMID:28670601

Design, synthesis and molecular modeling of new 4-phenylcoumarin derivatives as tubulin polymerization inhibitors targeting MCF-7 breast cancer cells.

PubMed

Batran, Rasha Z; Kassem, Asmaa F; Abbas, Eman M H; Elseginy, Samia A; Mounier, Marwa M

2018-07-23

A new set of 4-phenylcoumarin derivatives was designed and synthesized aiming to introduce new tubulin polymerization inhibitors as anti-breast cancer candidates. All the target compounds were evaluated for their cytotoxic effects against MCF-7 cell line, where compounds 2f, 3a, 3b, 3f, 7a and 7b, showed higher cytotoxic effect (IC 50  = 4.3-21.2 μg/mL) than the reference drug doxorubicin (IC 50  = 26.1 μg/mL), additionally, compounds 1 and 6b exhibited the same potency as doxorubicin (IC 50  = 25.2 and 28.0 μg/mL, respectively). The thiazolidinone derivatives 3a, 3b and 3f with potent and selective anticancer effects towards MCF-7 cells (IC 50  = 11.1, 16.7 and 21.2 μg/mL) were further assessed for tubulin polymerization inhibition effects which showed that the three compounds were potent tubulin polymerization suppressors with IC 50 values of 9.37, 2.89 and 6.13 μM, respectively, compared to the reference drug colchicine (IC 50  = 6.93 μM). The mechanistic effects on cell cycle progression and induction of apoptosis in MCF-7 cells were determined for compound 3a due to its potent and selective cytotoxic effects in addition to its promising tubulin polymerization inhibition potency. The results revealed that compound 3a induced cell cycle cessation at G2/M phase and accumulation of cells in pre-G1 phase and prevented its mitotic cycle, in addition to its activation of caspase-7 mediating apoptosis of MCF-7 cells. Molecular modeling studies for compounds 3a, 3b and 3f were carried out on tubulin crystallography, the results indicated that the compounds showed binding mode similar to the co-crystalized ligand; colchicine. Moreover, pharmacophore constructed models and docking studies revealed that thiazolidinone, acetamide and coumarin moieties are crucial for the activity. Molecular dynamics (MD) studies were carried out for the three compounds over 100 ps. MD results of compound 3a showed that it reached the stable state after 30 ps which was in agreement with the calculated potential and kinetic energy of compound 3a. Copyright © 2018 Elsevier Ltd. All rights reserved.

Two-photon polymerization of a three dimensional structure using beams with orbital angular momentum

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

Zhang, Shi-Jie; Li, Yan, E-mail: li@pku.edu.cn; Liu, Zhao-Pei

The focus of a beam with orbital angular momentum exhibits internal structure instead of an elliptical intensity distribution of a Gaussian beam, and the superposition of Gauss-Laguerre beams realized by two-dimensional phase modulation can generate a complex three-dimensional (3D) focus. By taking advantage of the flexibility of this 3D focus tailoring, we have fabricated a 3D microstructure with high resolution by two-photon polymerization with a single exposure. Furthermore, we have polymerized an array of double-helix structures that demonstrates optical chirality.

Imaging nanowire plasmon modes with two-photon polymerization

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

Gruber, Christian; Trügler, Andreas; Hohenester, Ulrich

2015-02-23

Metal nanowires sustain propagating surface plasmons that are strongly confined to the wire surface. Plasmon reflection at the wire end faces and interference lead to standing plasmon modes. We demonstrate that these modes can be imaged via two-photon (plasmon) polymerization of a thin film resist covering the wires and subsequent electron microscopy. Thereby, the plasmon wavelength and the phase shift of the nanowire mode picked up upon reflection can be directly retrieved. In general terms, polymerization imaging is a promising tool for the imaging of propagating plasmon modes from the nano- to micro-scale.

Cooperative polymerization of α-helices induced by macromolecular architecture

NASA Astrophysics Data System (ADS)

Baumgartner, Ryan; Fu, Hailin; Song, Ziyuan; Lin, Yao; Cheng, Jianjun

2017-07-01

Catalysis observed in enzymatic processes and protein polymerizations often relies on the use of supramolecular interactions and the organization of functional elements in order to gain control over the spatial and temporal elements of fundamental cellular processes. Harnessing these cooperative interactions to catalyse reactions in synthetic systems, however, remains challenging due to the difficulty in creating structurally controlled macromolecules. Here, we report a polypeptide-based macromolecule with spatially organized α-helices that can catalyse its own formation. The system consists of a linear polymeric scaffold containing a high density of initiating groups from which polypeptides are grown, forming a brush polymer. The folding of polypeptide side chains into α-helices dramatically enhances the polymerization rate due to cooperative interactions of macrodipoles between neighbouring α-helices. The parameters that affect the rate are elucidated by a two-stage kinetic model using principles from nucleation-controlled protein polymerizations; the key difference being the irreversible nature of this polymerization.

Detection of acrylamide in potato chips using a fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots.

PubMed

Hu, Qinqin; Xu, Xiahong; Li, Zhanming; Zhang, Ying; Wang, Jianping; Fu, Yingchun; Li, Yanbin

2014-04-15

Acrylamide is a neurotoxin and potential carcinogen, but is found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple and sensitive methods for on-line detection of acrylamide are needed to ensure food safety. In this paper, a novel fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots (QDs) was proposed for detecting acrylamide in potato chips. The functional QDs were prepared by their binding with N-acryloxysuccinimide (NAS), which was characterized by Fourier transform infrared (FR-IR) spectra. The carbon-carbon double bonds of NAS modified QDs polymerized with assistance of photo initiator under UV irradiation, leading to QDs getting closer along with fluorescence intensity decreasing. Acrylamide in the sample participated in the polymerization and induced an increase of fluorescence intensity. This method possessed a linear range from 3.5×10(-5) to 3.5 g L(-1) (r(2)=0.94) and a limit of detection of 3.5×10(-5) g L(-1). Although the sensitivity and specificity cannot be compared with standard LC-MS/MS analysis, this new method requires much less time and cost, which is promising for on-line rapid detection of acrylamide in food processing. © 2013 Published by Elsevier B.V.

Actin polymerization in neutrophils from donors of peripheral blood stem cells: divergent effects of glycosylated and nonglycosylated recombinant human granulocyte colony-stimulating factor.

PubMed

Carulli, Giovanni; Mattii, Letizia; Azzarà, Antonio; Brizzi, Stefania; Galimberti, Sara; Zucca, Alessandra; Benedetti, Edoardo; Petrini, Mario

2006-05-01

Neutrophil functions can be modified by Recombinant human G-CSF (rhG-CSF) treatment, with divergent effects on phagocytosis, motility, bactericidal activity, and surface molecule expression. Neutrophil morphology is modified by treatment with filgrastim (the nonglycosylated form of rhG-CSF), while it is not affected by lenograstim (the glycosylated type of rhG-CSF). Little information is available about actin polymerization in neutrophils from subjects treated with the two types of rhG-CSF. In the current paper we evaluated two groups of donors of peripheral blood stem cells (PBSC) for allogeneic transplantation. Ten subjects were treated with filgrastim and 10 with lenograstim to mobilize PBSC; 15 blood donors were evaluated as a control group. Actin polymerization (both spontaneous and fMLP-stimulated) was studied by a flow cytometric assay. A microscopic fluorescent assay was also carried out to evaluate F-actin distribution in neutrophils. We found that filgrastim induced an increased F-actin content in resting neutrophils, along with morphologic evidence for increased actin polymerization distributed principally at the cell membrane and frequently polarized in focal areas; in addition, fMLP was not able to induce further actin polymerization. On the contrary, treatment with lenograstim was associated with F-actin content, distribution, and polymerization kinetics indistinguishable from those displayed by control neutrophils. Such experimental results show that filgrastim and lenograstim display divergent effects also on neutrophil actin polymerization and provide further explanation for previous experimental findings. 2006 Wiley-Liss, Inc.

In situ-forming hydrogels for sustained ophthalmic drug delivery.

PubMed

Nanjawade, Basavaraj K; Manvi, F V; Manjappa, A S

2007-09-26

Ophthalmic drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist. The conventional ocular drug delivery systems like solutions, suspensions, and ointments show drawbacks such as increased precorneal elimination, high variability in efficiency, and blurred vision respectively. In situ-forming hydrogels are liquid upon instillation and undergo phase transition in the ocular cul-de-sac to form visco-elastic gel and this provides a response to environmental changes. In the past few years, an impressive number of novel temperature, pH, and ion induced in situ-forming systems have been reported for sustain ophthalmic drug delivery. Each system has its own advantages and drawbacks. The choice of a particular hydrogel depends on its intrinsic properties and envisaged therapeutic use. This review includes various temperature, pH, and ion induced in situ-forming polymeric systems used to achieve prolonged contact time of drugs with the cornea and increase their bioavailability.

Heat Stable Polymers: Polyphenylene and Other Aromatic Polymers

DTIC Science & Technology

1977-01-01

crystalline transition temperature . Model reactions on 4- and 6-phienyl-2-pyrones show that this monomer type is unsuitable for the syntheses of... temperature to a rod-like molecule with a high glass transition temperature . The polymerization reaction is acid catalyzed, but is carried out most...Polymerization Reactions...................24 Solution Properties......................27 Phase Transition Temperatures , Thermal Stability and Thermomechanical

Equilibrium polymerization models of re-entrant self-assembly

NASA Astrophysics Data System (ADS)

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

2009-04-01

As is well known, liquid-liquid phase separation can occur either upon heating or cooling, corresponding to lower and upper critical solution phase boundaries, respectively. Likewise, self-assembly transitions from a monomeric state to an organized polymeric state can proceed either upon increasing or decreasing temperature, and the concentration dependent ordering temperature is correspondingly called the "floor" or "ceiling" temperature. Motivated by the fact that some phase separating systems exhibit closed loop phase boundaries with two critical points, the present paper analyzes self-assembly analogs of re-entrant phase separation, i.e., re-entrant self-assembly. In particular, re-entrant self-assembly transitions are demonstrated to arise in thermally activated equilibrium self-assembling systems, when thermal activation is more favorable than chain propagation, and in equilibrium self-assembly near an adsorbing boundary where strong competition exists between adsorption and self-assembly. Apparently, the competition between interactions or equilibria generally underlies re-entrant behavior in both liquid-liquid phase separation and self-assembly transitions.

A sol-powder coating technique for fabrication of yttria stabilised zirconia

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

Wattanasiriwech, Darunee; Wattanasiriwech, Suthee; Stevens, Ron

Yttria stabilised zirconia has been prepared using a simple sol-powder coating technique. The polymeric yttria sol, which was prepared using 1,3 propanediol as a network modifier, was homogeneously mixed with nanocrystalline zirconia powder and it showed a dual function: as a binder which promoted densification and a phase modifier which stabilised zirconia in the tetragonal and cubic phases. Thermal analysis and X-ray diffraction revealed that the polymeric yttria sol which decomposed at low temperature into yttrium oxide could change the m {sup {yields}} t phase transformation behaviour of the zirconia, possibly due to the small particle size and very highmore » surface area of both yttria and zirconia particles allowing rapid alloying. The sintered samples exhibited three crystalline phases: monoclinic, tetragonal and cubic, in which cubic and tetragonal are the major phases. The weight fractions of the individual phases present in the selected specimens were determined using quantitative Rietveld analysis.« less

Preparation of thermo-responsive polymer brushes on hydrophilic polymeric beads by surface-initiated atom transfer radical polymerization for a highly resolutive separation of peptides.

PubMed

Mizutani, Aya; Nagase, Kenichi; Kikuchi, Akihiko; Kanazawa, Hideko; Akiyama, Yoshikatsu; Kobayashi, Jun; Annaka, Masahiko; Okano, Teruo

2010-09-17

Poly(N-isopropylacrylamide-co-N-tert-butylacrylamide) [P(IPAAm-co-tBAAm)] brushes were prepared on poly(hydroxy methacrylate) (PHMA) [hydrolyzed poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)] beads having large pores by surface-initiated atom transfer radical polymerization (ATRP) and applied to the stationary phases of thermo-responsive chromatography. Optimized amount of copolymer brushes grafted PHMA beads were able to separate peptides and proteins with narrow peaks and a high resolution. The beads were found to have a specific surface area of 43.0 m(2)/g by nitrogen gas adsorption method. Copolymer brush of P(IPAAm-co-tBAAm) grafted PHMA beads improved the stationary phase of thermo-responsive chromatography for the all-aqueous separation of peptides and proteins. 2010 Elsevier B.V. All rights reserved.

Nanoengineered analytical immobilized metal affinity chromatography stationary phase by atom transfer radical polymerization: Separation of synthetic prion peptides

PubMed Central

McCarthy, P.; Chattopadhyay, M.; Millhauser, G.L.; Tsarevsky, N.V.; Bombalski, L.; Matyjaszewski, K.; Shimmin, D.; Avdalovic, N.; Pohl, C.

2010-01-01

Atom transfer radical polymerization (ATRP) was employed to create isolated, metal-containing nanoparticles on the surface of non-porous polymeric beads with the goal of developing a new immobilized metal affnity chromatography (IMAC) stationary phase for separating prion peptides and proteins. Transmission electron microscopy was used to visualize nanoparticles on the substrate surface. Individual ferritin molecules were also visualized as ferritin–nanoparticle complexes. The column's resolving power was tested by synthesizing peptide analogs to the copper binding region of prion protein and injecting mixtures of these analogs onto the column. As expected, the column was capable of separating prion-related peptides differing in number of octapeptide repeat units (PHGGGWGQ), (PHGGGWGQ)2, and (PHGGGWGQ)4. Unexpectedly, the column could also resolve peptides containing the same number of repeats but differing only in the presence of a hydrophilic tail, Q → A substitution, or amide nitrogen methylation. PMID:17481564

Conductive Textiles via Vapor-Phase Polymerization of 3,4-Ethylenedioxythiophene.

PubMed

Ala, Okan; Hu, Bin; Li, Dapeng; Yang, Chen-Lu; Calvert, Paul; Fan, Qinguo

2017-08-30

We fabricated electrically conductive textiles via vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) layers on cotton, cotton/poly(ethylene terephthalate) (PET), cotton/Lycra, and PET fabrics. We then measured the electrical resistivity values of such PEDOT-coated textiles and analyzed the effect of water treatment on the electrical resistivity. Additionally, we tested the change in the electrical resistance of the conductive textiles under cyclic stretching and relaxation. Last, we characterized the uniformity and morphology of the conductive layer formed on the fabrics using scanning electron microscopy and electron-dispersive X-ray spectroscopy.

[Determination of triterpenoic acids in fruits of Ziziphus jujuba using HPLC-MS with polymeric ODS column].

PubMed

Zhang, Yong; Zhou, An; Xie, Xiao-Mei

2013-03-01

A simple and sensitive method has been developed to simultaneously determine betunilic acid, oleanolic acid and ursolic acid in the fruits of Ziziphus jujuba from different regions by HPLC-MS. This HPLC assay was performed on PAH polymeric C18 bonded stationary phase column with mobile phase contained acetonitrile-water (90: 10) and with negative ESI detection mode. The developed approach was characterized by short time consumption for chromatographic separation, high sensitivity and good reliability so as to meet the requirements for rapid analysis of large-batch fruits of Z. jujuba from different habitats.

Method for fabricating thin films of pyrolytic carbon

DOEpatents

Brassell, G.W.; Lewis, J. Jr.; Weber, G.W.

1980-03-13

The present invention relates to a method for fabricating ultrathin films of pyrolytic carbon. Pyrolytic carbon is vapor deposited onto a concave surface of a heated substrate to a total uniform thickness in the range of about 0.1 to 1.0 micrometer. The carbon film on the substrate is provided with a layer of adherent polymeric resin. The resulting composite film of pyrolytic carbon and polymeric resin is then easily separated from the substrate by shrinking the 10 polymeric resin coating with thermally induced forces.

Method for fabricating thin films of pyrolytic carbon

DOEpatents

Brassell, Gilbert W.; Lewis, Jr., John; Weber, Gary W.

1982-01-01

The present invention relates to a method for fabricating ultra-thin films of pyrolytic carbon. Pyrolytic carbon is vapor deposited onto a concave surface of a heated substrate to a total uniform thickness in the range of about 0.1 to 1.0 micrometer. The carbon film on the substrate is provided with a layer of adherent polymeric resin. The resulting composite film of pyrolytic carbon and polymeric resin is then easily separated from the substrate by shrinking the polymeric resin coating with thermally induced forces.

Dynamics and Regulation of RecA Polymerization and De-Polymerization on Double-Stranded DNA

PubMed Central

Muniyappa, Kalappa; Yan, Jie

2013-01-01

The RecA filament formed on double-stranded (ds) DNA is proposed to be a functional state analogous to that generated during the process of DNA strand exchange. RecA polymerization and de-polymerization on dsDNA is governed by multiple physiological factors. However, a comprehensive understanding of how these factors regulate the processes of polymerization and de-polymerization of RecA filament on dsDNA is still evolving. Here, we investigate the effects of temperature, pH, tensile force, and DNA ends (in particular ssDNA overhang) on the polymerization and de-polymerization dynamics of the E. coli RecA filament at a single-molecule level. Our results identified the optimal conditions that permitted spontaneous RecA nucleation and polymerization, as well as conditions that could maintain the stability of a preformed RecA filament. Further examination at a nano-meter spatial resolution, by stretching short DNA constructs, revealed a striking dynamic RecA polymerization and de-polymerization induced saw-tooth pattern in DNA extension fluctuation. In addition, we show that RecA does not polymerize on S-DNA, a recently identified novel base-paired elongated DNA structure that was previously proposed to be a possible binding substrate for RecA. Overall, our studies have helped to resolve several previous single-molecule studies that reported contradictory and inconsistent results on RecA nucleation, polymerization and stability. Furthermore, our findings also provide insights into the regulatory mechanisms of RecA filament formation and stability in vivo. PMID:23825559

PLCβ3 mediates cortactin interaction with WAVE2 in MCP1-induced actin polymerization and cell migration.

PubMed

Janjanam, Jagadeesh; Chandaka, Giri Kumar; Kotla, Sivareddy; Rao, Gadiparthi N

2015-12-15

Monocyte chemotactic protein 1 (MCP1) stimulates vascular smooth muscle cell (VSMC) migration in vascular wall remodeling. However, the mechanisms underlying MCP1-induced VSMC migration have not been understood. Here we identify the signaling pathway associated with MCP1-induced human aortic smooth muscle cell (HASMC) migration. MCP1, a G protein-coupled receptor agonist, activates phosphorylation of cortactin on S405 and S418 residues in a time-dependent manner, and inhibition of its phosphorylation attenuates MCP1-induced HASMC G-actin polymerization, F-actin stress fiber formation, and migration. Cortactin phosphorylation on S405/S418 is found to be critical for its interaction with WAVE2, a member of the WASP family of cytoskeletal regulatory proteins required for cell migration. In addition, the MCP1-induced cortactin phosphorylation is dependent on PLCβ3-mediated PKCδ activation, and siRNA-mediated down-regulation of either of these molecules prevents cortactin interaction with WAVE2, affecting G-actin polymerization, F-actin stress fiber formation, and HASMC migration. Upstream, MCP1 activates CCR2 and Gαq/11 in a time-dependent manner, and down-regulation of their levels attenuates MCP1-induced PLCβ3 and PKCδ activation, cortactin phosphorylation, cortactin-WAVE2 interaction, G-actin polymerization, F-actin stress fiber formation, and HASMC migration. Together these findings demonstrate that phosphorylation of cortactin on S405 and S418 residues is required for its interaction with WAVE2 in MCP1-induced cytoskeleton remodeling, facilitating HASMC migration. © 2015 Janjanam et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters

NASA Astrophysics Data System (ADS)

Babic, Steven; Schreiner, L. John

2006-09-01

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters.

PubMed

Babic, Steven; Schreiner, L John

2006-09-07

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

Characterization of γ-radiation induced polymerization in ethyl methacrylate and methyl acrylate monomers solutions

NASA Astrophysics Data System (ADS)

Baccaro, Stefania; Casieri, Cinzia; Cemmi, Alessia; Chiarini, Marco; D'Aiuto, Virginia; Tortora, Mariagrazia

2017-12-01

The present work is focused on the γ-radiation induced polymerization of ethyl methacrylate (EMA) and methyl acrylate (MA) monomers mixture to obtain a co-polymer with specific features. The effect of the irradiation parameters (radiation absorbed dose, dose rate) and of the environmental atmosphere on the features of the final products was investigated. Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Nuclear Magnetic Resonance high-resolution analyses of hydrogen and carbon nuclei (1H and 13C NMR) were applied to follow the γ-induced modifications by monitoring the co-polymerization process and allowed the irradiation parameters optimization. Diffusion-Ordered NMR (DOSY-NMR) data were used to evaluate the co-polymers polydispersity and polymerization degree. Since the last parameter is strongly influenced by the γ radiation and environmental conditions, a comparison among samples prepared and irradiated in air and under nitrogen atmosphere was carried out. In presence of oxygen, higher radiation was required to obtain a full solid co-polymer since a partial amount of energy released to the samples was involved in competitive processes, i.e. oxygen-containing free radicals formation and primary radicals recombination. Irrespectively to the environmental atmosphere, more homogeneous samples in term of polymerization degree dispersion was achieved at lower dose rates. At radiation absorbed doses higher than those needed for the formation of the co-polymer, while in case of samples irradiated in air heavy depolymerization was verified, a sensible increase of the samples stability was attained if the irradiation was performed under nitrogen atmosphere.

Poly(vinyl alcohol) stabilization of acrylic emulsion polymers using the miniemulsion approach

NASA Astrophysics Data System (ADS)

Kim, Noma

Miniemulsion approach was employed to obtain stable acrylic latexes of n-butyl acrylate and methyl methacrylate (50/50 wt%) stabilized with poly(vinyl alcohol) (PVA) and to enhance the grafting reaction between PVA and acrylic monomers at the water/droplet interface. The stability of miniemulsions were studied in terms of the type and concentration of' the stabilizer, and the PVA partitioning were determined as a function of the PVA concentration. Using the comparison of PVA partitioning at droplet surface and grafted PVA as a function of concentration, it was suggested that the water/monomer interface is the main grafting site in the miniemulsion polymerization. Seeded emulsion and miniemulsion copolymerizations initiated with water-soluble (hydrogen peroxide, HPO), partially water-soluble (t-butyl peroxide, TBHP), and oil-soluble (t-butyl peroxyoctoate, TBPO) initiators were carried out to further investigate the oil/water interface as the grafting site for PVA. The interaction between the capillary wall in the CHDF (capillary hydrodynamic fractionation) chromatographic particle sizer and the water-soluble polymers adsorbed on the particle surface was studied using different types of water-soluble polymers and eluants. Different grafting architectures depending on the initiation site were suggested based on the CHDF results. The amounts of grafted PVA produced in miniemulsion polymers initiated with TBHP and TBPO were substantially less than those in the corresponding seeded emulsion polymerizations. The effect on the internal viscosity at the interface was proposed to explain the difference in grafting in terms of polymerization methods. Aqueous phase and interface grafting were studied using the measurement of the degree of hydrolysis (DH) of the serum PVA and adsorbed PVA after miniemulsion polymerizations. Based on the results, it was found that aqueous phase and interface grafting occurred in the HPO system; however, interface grafting dominated the TBHP system. Colloidal instability in conventional emulsion polymerizations was investigated and compared with the corresponding miniemulsion polymerization. It was found that the grafted PVA in conventional emulsion polymerizations was more hydrophobic presumably due to a greater amount of grafted chains than that in similar miniemulsion polymerizations and this could be correlated with the colloidal instability during conventional emulsion polymerizations.

Acrylate intercalation and in situ polymerization in iron-, cobalt-, or manganese-substituted nickel hydroxides.

PubMed

Vaysse, C; Guerlou-Demourgues, L; Duguet, E; Delmas, C

2003-07-28

A chimie douce route based on successive redox and exchange reactions has allowed us to prepare new hybrid organic-inorganic materials, composed of polyacrylate macromolecules intercalated into layered double hydroxides (LDHs), deriving from Ni(OH)(2). Monomer intercalation and in situ polymerization mechanisms have appeared to be strongly dependent upon the nature of the substituting cation in the slabs. In the case of iron-based LDHs, a phase containing acrylate monomeric intercalates has been isolated and identified by X-ray diffraction and infrared spectroscopy. Second, interslab free-radical polymerization of acrylate anions has been successfully initiated using potassium persulfate. In cobalt- or manganese-based LDHs, one-step polymerization has been observed, leading directly to a material containing polyacrylate intercalate.

The unusual dynamics of parasite actin result from isodesmic polymerization

PubMed Central

Skillman, Kristen M.; Ma, Christopher I.; Fremont, Daved H.; Diraviyam, Karthikeyan; Cooper, John A.; Sept, David; Sibley, L. David

2013-01-01

Previous reports have indicated that parasite actins are short and inherently unstable, despite being required for motility. Here, we re-examine the polymerization properties of actin in Toxoplasma gondii (TgACTI), unexpectedly finding that it exhibits isodesmic polymerization in contrast to the conventional nucleation-elongation process of all previously studied actins from both eukaryotes and bacteria. TgACTI polymerization kinetics lacks both a lag phase and critical concentration, normally characteristic of actins. Unique among actins, the kinetics of assembly can be fit with a single set of rate constants for all subunit interactions, without need for separate nucleation and elongation rates. This isodesmic model accurately predicts the assembly, disassembly, and the size distribution of TgACTI filaments in vitro, providing a mechanistic explanation for actin dynamics in vivo. Our findings expand the repertoire of mechanisms by which actin polymerization is governed and offer clues about the evolution of self-assembling, stabilized protein polymers. PMID:23921463

Actin Polymerization is Stimulated by Actin Crosslinking Protein Palladin

PubMed Central

Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Egelman, Edward H.; Beck, Moriah R.

2016-01-01

The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes. PMID:26607837

Synthesis of crystalline gels on a light-induced polymerization 3D printer (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gong, Jin; Mao, Yuchen; Miyazaki, Takuya; Zhu, Meifang

2017-04-01

3D printing, also knows as Additive Manufacturing (AM), was first commercialized in 1986, and has been growing at breakneck speed since 2009 when Stratasys' key patent expired. Currently the 3D printing machines coming on the market can be broadly classified into three categories from the material state point of view: plastic filament printers, powder (or pellet) printers, film printers and liquid photopolymer printers. Much of the work in our laboratory revolves around the crystalline gels. We have succeeded in developing them with high toughness, high flexibility, particularly with many functions as shape memory, energy storage, freshness-retaining, water-absorbing, etc. These crystalline gels are synthesized by light-induced radical polymerization that involves light-reactive monomer having the property of curing with light of a sufficient energy to drive the reaction from liquid to solid. Note that the light-induced polymerized 3D printing uses the same principle. To open up the possibilities for broader application of our crystalline functional gels, we are interested in making them available for 3D printing. In this paper, we share the results of our latest research on the 3D printing of crystalline gels on light-induced 3D printers.

Altered native stability is the dominant basis for susceptibility of α1-antitrypsin mutants to polymerization

PubMed Central

Irving, James A.; Haq, Imran; Dickens, Jennifer A.; Faull, Sarah V.; Lomas, David A.

2014-01-01

Serpins are protease inhibitors whose most stable state is achieved upon transition of a central 5-stranded β-sheet to a 6-stranded form. Mutations, low pH, denaturants and elevated temperatures promote this transition, which can result in a growing polymer chain of inactive molecules. Different types of polymer are possible, but, experimentally only heat has been shown to generate polymers in vitro consistent with ex vivo pathological specimens. Many mutations that alter the rate of heat-induced polymerization have been described, but interpretation is problematic because discrimination is lacking between the effect of global changes in native stability and specific effects on structural mechanism. We show that the temperature midpoint (Tm) of thermal denaturation reflects the transition of α1-antitrypsin to the polymerization intermediate, and determine the relationship with fixed-temperature polymerization half-times (t0.5) in the presence of stabilizing additives [TMAO (trimethylamine N-oxide), sucrose and sodium sulfate], point mutations and disulfide bonds. Combined with a retrospective analysis of 31 mutants characterized in the literature, the results of the present study show that global changes to native state stability are the predominant basis for the effects of mutations and osmolytes on heat-induced polymerization, summarized by the equation: ln(t0.5,mutant/t0.5,wild-type)=0.34×ΔTm. It is deviations from this relationship that hold key information about the polymerization process. PMID:24552432

Separation and characterization of allergic polymerized impurities in cephalosporins by 2D-HPSEC×LC-IT-TOF MS.

PubMed

Xu, Yu; Wang, DanDan; Tang, Lan; Wang, Jian

2017-10-25

Eleven unknown allergic impurities in cefodizime, cefmenoxime and cefonicid were separated and characterized by a trap-free two-dimensional high performance size exclusion chromatography (HPSEC) and reversed phase liquid chromatography (RP-HPLC) coupled to high resolution ion trap/time-of-flight mass spectrometry (2D-HPSEC×LC-IT-TOF MS) with positive and negative modes of electrospray ionization method. Separation and characterization the allergic polymerized impurities in β-lactam antibiotics were on the basis of column-switching technique which effectively combined the advantages of HPSEC and the ability of RP-HPLC to identify the special impurities. In the first dimension HPSEC, the column was Xtimate SEC-120 analytical column (7.8mm×30cm, 5μm), and the gradient elution used pH 7.0 buffer-acetonitrile as mobile phase And the second dimension analytical column was ZORBAX SB-C18 (4.6×150mm, 3.5μm) with ammonium formate solution (10mM) and ammonium formate (8mM) in [acetonitrile-water (4:1, v/v)] solution as mobile phase. Structures of eleven unknown impurities were deduced based on the high resolution MS n data with both positive and negative modes, in which nine impurities were polymerized impurities. The forming mechanism of β-lactam antibiotic polymerization in cephalosporins was also studied. The question on incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely by multidimensional heart-cutting approaches and online demineralization technique, which was worthy of widespread use and application for the advantages of stability and repeatability. Copyright © 2017. Published by Elsevier B.V.

Dental Composites with Calcium / Strontium Phosphates and Polylysine.

PubMed

Panpisut, Piyaphong; Liaqat, Saad; Zacharaki, Eleni; Xia, Wendy; Petridis, Haralampos; Young, Anne Margaret

2016-01-01

This study developed light cured dental composites with added monocalcium phosphate monohydrate (MCPM), tristrontium phosphate (TSrP) and antimicrobial polylysine (PLS). The aim was to produce composites that have enhanced water sorption induced expansion, can promote apatite precipitation and release polylysine. Experimental composite formulations consisted of light activated dimethacrylate monomers combined with 80 wt% powder. The powder phase contained a dental glass with and without PLS (2.5 wt%) and/or reactive phosphate fillers (15 wt% TSrP and 10 wt% MCPM). The commercial composite, Z250, was used as a control. Monomer conversion and calculated polymerization shrinkage were assessed using FTIR. Subsequent mass or volume changes in water versus simulated body fluid (SBF) were quantified using gravimetric studies. These were used, along with Raman and SEM, to assess apatite precipitation on the composite surface. PLS release was determined using UV spectroscopy. Furthermore, biaxial flexural strengths after 24 hours of SBF immersion were obtained. Monomer conversion of the composites decreased upon the addition of phosphate fillers (from 76 to 64%) but was always higher than that of Z250 (54%). Phosphate addition increased water sorption induced expansion from 2 to 4% helping to balance the calculated polymerization shrinkage of ~ 3.4%. Phosphate addition promoted apatite precipitation from SBF. Polylysine increased the apatite layer thickness from ~ 10 to 20 μm after 4 weeks. The novel composites showed a burst release of PLS (3.7%) followed by diffusion-controlled release irrespective of phosphate addition. PLS and phosphates decreased strength from 154 MPa on average by 17% and 18%, respectively. All formulations, however, had greater strength than the ISO 4049 requirement of > 80 MPa. The addition of MCPM with TSrP promoted hygroscopic expansion, and apatite formation. These properties are expected to help compensate polymerization shrinkage and help remineralize demineralized dentin. Polylysine can be released from the composites at early time. This may kill residual bacteria.

Quantitative Phase Microscopy for Accurate Characterization of Microlens Arrays

NASA Astrophysics Data System (ADS)

Grilli, Simonetta; Miccio, Lisa; Merola, Francesco; Finizio, Andrea; Paturzo, Melania; Coppola, Sara; Vespini, Veronica; Ferraro, Pietro

Microlens arrays are of fundamental importance in a wide variety of applications in optics and photonics. This chapter deals with an accurate digital holography-based characterization of both liquid and polymeric microlenses fabricated by an innovative pyro-electrowetting process. The actuation of liquid and polymeric films is obtained through the use of pyroelectric charges generated into polar dielectric lithium niobate crystals.

Evaluation of a new polymeric stationary phase with reversed-phase properties for high temperature liquid chromatography.

PubMed

Vanhoenacker, Gerd; Dos Santos Pereira, Alberto; Kotsuka, Takashi; Cabooter, Deirdre; Desmet, Gert; Sandra, Pat

2010-05-07

The performance of a polymeric stationary phase with reversed-phase properties (ET-RP1) was evaluated for LC separations at elevated temperature. The most significant observation was that the reduced plate height (h) decreased from 3.4 at 25 degrees C (optimal flow 0.5 mL/min) to 2.4 at 150 degrees C (optimal flow 2.5 mL/min) which is comparable to the efficiency obtained with silica-based reversed-phase columns of 4.6mm ID operated at 0.8 mL/min. The phase showed no deterioration after long use at 150 degrees C within the pH range 1-9. Catalytic activity originating from the stationary phase material, e.g. as experienced on zirconium columns operated at elevated temperature, was absent. The performance of ET-RP1 is illustrated with the analysis of some pharmaceutical samples by LC and LC-MS. Operation at elevated temperature also allows to reduce the amount of organic modifier or to replace acetonitrile and methanol by the biodegradable ethanol. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Preparation and evaluation of diblock copolymer-grafted silica by sequential surface initiated-atom transfer radical polymerization for reverse-phase/ion-exchange mixed-mode chromatography.

PubMed

Bo, Chun Miao; Wang, Chaozhan; Wei, Yin Mao

2017-12-01

A novel approach that involved the grafting of diblock copolymer with two types of monomer onto substrate by sequential surface initiated-atom transfer radical polymerization was proposed to prepare a mixed-mode chromatographic stationary phase. The distinguishing feature of this method is that it can be applied in the preparation of various mixed-mode stationary phases. In this study, a new reverse-phase/ion-exchange stationary phase was prepared by grafting hydrophobic styrene and cationic sodium 4-styrenesulfonate by the proposed approach onto silica surface. The chromatographic properties of the prepared stationary phase were evaluated by the separation of benzene derivatives, anilines, and β-agonists, and by the effect of pH values and acetonitrile content on the retention. Compared with typical RP columns, the prepared stationary phase achieved the better resolution and higher selectivity at a shorter separation time and lower organic content. Moreover, the application of the prepared column was proved by separating widely distributed polar and charged compounds simultaneously. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fractography of poly(methyl methacrylates).

PubMed

Kusy, R P; Turner, D T

1975-07-01

For convenience in clinical manipulation, it is the practice to fabricate PMMA protheses from mixtures of powder and monomer. When the monomer is subsequently polymerized an unusual 2-phase polymeric material results in which grains of PMMA are dispersed in a matrix of the same polymer. The mechanical properties of the 2-phase materials are inferior in certain respects relative to 1-phase polymers. The purpose of the present work is to evaluate the failure of 2-phase materials by microscopical examination of their fracture surfaces. A granular microstructure was clearly distinguishable and a distinction made between materials which fail exclusively by transgranular fracture and others which additionally exhibit intergranular fracture. In order to interpret markings observed on the fracture surfaces of the complex 2-phase systems a study was made of the influence of molecular weight on the fractography of 1-phase PMMA. Molecular weight was reduced by degradation of samples by exposure to gamma-rays. The spacing of periodic rib markings on fracture surfaces was found to decrease with molecular weight and this relationship used to provide an estimate of the molecular weight of polymer in the matrix of 2-phase materials.

Crosslinked structurally-tuned polymeric ionic liquids as stationary phases for the analysis of hydrocarbons in kerosene and diesel fuels by comprehensive two-dimensional gas chromatography.

PubMed

Zhang, Cheng; Park, Rodney A; Anderson, Jared L

2016-04-01

Structurally-tuned ionic liquids (ILs) have been previously applied as the second dimension column in comprehensive two-dimensional gas chromatography (GC×GC) and have demonstrated high selectivity in the separation of individual aliphatic hydrocarbons from other aliphatic hydrocarbons. However, the maximum operating temperatures of these stationary phases limit the separation of analytes with high boiling points. In order to address this issue, a series of polymeric ionic liquid (PIL)-based stationary phases were prepared in this study using imidazolium-based IL monomers via in-column free radical polymerization. The IL monomers were functionalized with long alkyl chain substituents to provide the needed selectivity for the separation of aliphatic hydrocarbons. Columns were prepared with different film thicknesses to identify the best performing stationary phase for the separation of kerosene. The bis[(trifluoromethyl)sulfonyl]imide ([NTf2](-))-based PIL stationary phase with larger film thickness (0.28μm) exhibited higher selectivity for aliphatic hydrocarbons and showed a maximum allowable operating temperature of 300°C. PIL-based stationary phases containing varied amount of IL-based crosslinker were prepared to study the effect of the crosslinker on the selectivity and thermal stability of the resulting stationary phase. The optimal resolution of aliphatic hydrocarbons was achieved when 50% (w/w) of crosslinker was incorporated into the PIL-based stationary phase. The resulting stationary phase exhibited good selectivity for different groups of aliphatic hydrocarbons even after being conditioned at 325°C. Finally, the crosslinked PIL-based stationary phase was compared with SUPELCOWAX 10 and DB-17 columns for the separation of aliphatic hydrocarbons in diesel fuel. Better resolution of aliphatic hydrocarbons was obtained when employing the crosslinked PIL-based stationary phase as the second dimension column. Copyright © 2016 Elsevier B.V. All rights reserved.

Phase change compositions

DOEpatents

Salyer, Ival O.; Griffen, Charles W.

1986-01-01

Compositions containing crystalline, long chain, alkyl hydrocarbons as phase change materials including cementitious compositions containing the alkyl hydrocarbons neat or in pellets or granules formed by incorporating the alkyl hydrocarbons in polymers or rubbers; and polymeric or elastomeric compositions containing alkyl hydrocarbons.

Phase change compositions

DOEpatents

Salyer, Ival O.

1989-01-01

Compositions containing crystalline, straight chain, alkyl hydrocarbons as phase change materials including cementitious compositions containing the alkyl hydrocarbons neat or in pellets or granules formed by incorporating the alkyl hydrocarbons in polymers or rubbers; and polymeric or elastomeric compositions containing alkyl hydrocarbons.

Recent advances and developments in composite dental restorative materials.

PubMed

Cramer, N B; Stansbury, J W; Bowman, C N

2011-04-01

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance.

Clays and other minerals in prebiotic processes

NASA Technical Reports Server (NTRS)

Paecht-Horowitz, M.

1984-01-01

Clays and other minerals have been investigated in context with prebiotic processes, mainly in polymerization of amino acids. It was found that peptides adsorbed on the clay, prior to polymerization, influence the reaction. The ratio between the amount of the peptides adsorbed and that of the clay is important for the yield as well as for the degrees of polymerization obtained. Adsorption prior to reaction produces a certain order in the aggregates of the clay particles which might induce better reaction results. Excess of added peptides disturbs this order and causes lesser degrees of polymerization. In addition to adsorption, clays are also able to occlude between their layers substances out of the environment, up to very high concentrations.

Molecular Probe Fluorescence Monitoring of Polymerization

NASA Technical Reports Server (NTRS)

Bunton, Patrick

2002-01-01

This project investigated the feasibility of using fluorescence spectroscopy to determine viscosity of polymer/monomer in support of Transient Interfacial Phenomena in Miscible Polymer Systems (TIPMPS). This project will attempt to measure gradient induced flow at a miscible interface during and / or after in-flight polymerization of dodecyl acrylate (lauryl acrylate). Concentration and temperature gradients will be intentionally introduced during polymerization and the resultant fluid flow determined by Particle Imaging Velocimetry (PIV). This report describes an investigation of the feasibility of using fluorescence of a probe molecule to monitor viscosity and/or concentration during and after polymerization. The probe used was pyrene which has been shown to be sensitive to its local environment in methyl methacrylate.

Recent Advances and Developments in Composite Dental Restorative Materials

PubMed Central

Cramer, N.B.; Stansbury, J.W.; Bowman, C.N.

2011-01-01

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance. PMID:20924063

The accessibility of etheno-nucleotides to collisional quenchers and the nucleotide cleft in G- and F-actin.

PubMed Central

Root, D. D.; Reisler, E.

1992-01-01

Recent publication of the atomic structure of G-actin (Kabsch, W., Mannherz, H. G., Suck, D., Pai, E. F., & Holmes, K. C., 1990, Nature 347, 37-44) raises questions about how the conformation of actin changes upon its polymerization. In this work, the effects of various quenchers of etheno-nucleotides bound to G- and F-actin were examined in order to assess polymerization-related changes in the nucleotide phosphate site. The Mg(2+)-induced polymerization of actin quenched the fluorescence of the etheno-nucleotides by approximately 20% simultaneously with the increase in light scattering by actin. A conformational change at the nucleotide binding site was also indicated by greater accessibility of F-actin than G-actin to positively, negatively, and neutrally charged collisional quenchers. The difference in accessibility between G- and F-actin was greatest for I-, indicating that the environment of the etheno group is more positively charged in the polymerized form of actin. Based on calculations of the change in electric potential of the environment of the etheno group, specific polymerization-related movements of charged residues in the atomic structure of G-actin are suggested. The binding of S-1 to epsilon-ATP-G-actin increased the accessibility of the etheno group to I- even over that in Mg(2+)-polymerized actin. The quenching of the etheno group by nitromethane was, however, unaffected by the binding of S-1 to actin. Thus, the binding of S-1 induces conformational changes in the cleft region of actin that are different from those caused by Mg2+ polymerization of actin.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1304380

Comparison of photo- and thermally initiated polymerization-induced self-assembly: a lack of end group fidelity drives the formation of higher order morphologies† †Electronic supplementary information (ESI) available: Additional NMR spectra, SEC, TEM and DLS data as well as histograms for the PEG113–PHPMA400 formulations and MALDI-ToF data for the oligomer study. See DOI: 10.1039/c7py00407a

PubMed Central

Blackman, Lewis D.; Doncom, Kay E. B.

2017-01-01

Polymerization-induced self-assembly (PISA) is an emerging industrially relevant technology, which allows the preparation of defined and predictable polymer self-assemblies with a wide range of morphologies. In recent years, interest has turned to photoinitiated PISA processes, which show markedly accelerated reaction kinetics and milder conditions, thereby making it an attractive alternative to thermally initiated PISA. Herein, we attempt to elucidate the differences between these two initiation methods using isothermally derived phase diagrams of a well-documented poly(ethylene glycol)-b-(2-hydroxypropyl methacrylate) (PEG-b-HPMA) PISA system. By studying the influence of the intensity of the light source used, as well as an investigation into the thermodynamically favorable morphologies, the factors dictating differences in the obtained morphologies when comparing photo- and thermally initiated PISA were explored. Our findings indicate that differences in a combination of both reaction kinetics and end group fidelity led to the observed discrepencies between the two techniques. We find that the loss of the end group in photoinitiated PISA drives the formation of higher order structures and that a morphological transition from worms to unilamellar vesicles could be induced by extended periods of light and heat irradiation. Our findings demonstrate that PISA of identical block copolymers by the two different initiation methods can lead to structures that are both chemically and morphologically distinct. PMID:29225706

Material Properties of Matrix Lipids Determine Conformation and Intermolecular Reactivity of a Diacetylenic Phosphatidylcholine in the Lipid Bilayer

PubMed Central

Puri, Anu; Jang, Hyunbum; Yavlovich, Amichai; Masood, M. Athar; Veenstra, Timothy D.; Luna, Carlos; Aranda-Espinoza, Helim; Nussinov, Ruth; Blumenthal, Robert

2011-01-01

Photopolymerizable phospholipid DC8,9PC (1,2-bis-(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine) exhibits unique assembly characteristics in the lipid bilayer. Due to the presence of the diacetylene groups, DC8,9PC undergoes polymerization upon UV (254 nm) exposure and assumes chromogenic properties. DC8,9PC photopolymerization in a gel phase matrix lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monitored by UV-VIS absorption spectroscopy occurred within 2 minutes after UV treatment, whereas no spectral shifts were observed when DC8,9PC was incorporated in a liquid phase matrix 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Liquid chromatography-tandem mass spectrometry analysis showed a decrease in DC8,9PC monomer in both DPPC and POPC environments without any change in matrix lipids in UV-treated samples. Molecular Dynamics (MD) simulations of DPPC/DC8,9PC and POPC/DC8,9PC bilayers indicate that the DC8,9PC molecules adjust to the thickness of the matrix lipid bilayer. Furthermore, motions of DC8,9PC in the gel phase bilayer are more restricted than in the fluid bilayer. The restricted motional flexibility of DC8,9PC (in the gel phase) enables the reactive diacetylenes in individual molecules to align and undergo polymerization, whereas the unrestricted motions in the fluid bilayer restrict polymerization due to the lack of appropriate alignment of the DC8,9PC fatty acyl chains. Fluorescence microscopy data indicates homogenous distribution of the lipid probe 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-lissamine rhodamine B sulfonyl ammonium salt (N-Rh-PE) in POPC/DC8,9PC monolayers, but domain formation in DPPC/DC8,9PC monolayers. These results show that the DC8,9PC molecules cluster and assume the preferred conformation in the gel phase matrix for UV-triggered polymerization reaction. PMID:22053903

Design considerations for multi component molecular-polymeric nonlinear optical materials

NASA Astrophysics Data System (ADS)

Singer, K. D.; Kuzyk, M. G.; Fang, T.; Holland, W. R.; Cahill, P. A.

1990-08-01

We review our work on multi component polymeric nonlinear optical materials. These materials consist of nonlinear optical molecules incorporated in a polymeric host. A cross-linked triazine polymer incorporating a dicyanovinyl terminated azo dye was found to be relatively stable at 85 deg and possess an electro-optic coefficient of 11pm/V. We have also observed the zero dispersion condition in a new anomalous dispersion dye for phase matched second harmonic generation, and expect efficient conversion to the blue. A squarylium dye, ISQ, has been found to possess a large third order nonlinearity, and may display two-level behavior.

Stability of whole inactivated influenza virus vaccine during coating onto metal microneedles

PubMed Central

Choi, Hyo-Jick; Bondy, Brian J.; Yoo, Dae-Goon; Compans, Richard W.; Kang, Sang-Moo; Prausnitz, Mark R.

2012-01-01

Immunization using a microneedle patch coated with vaccine offers the promise of simplified vaccination logistics and increased vaccine immunogenicity. This study examined the stability of influenza vaccine during the microneedle coating process, with a focus on the role of coating formulation excipients. Thick, uniform coatings were obtained using coating formulations containing a viscosity enhancer and surfactant, but these formulations retained little functional vaccine hemagglutinin (HA) activity after coating. Vaccine coating in a trehalose-only formulation retained about 40 – 50% of vaccine activity, which is a significant improvement. The partial viral activity loss observed in the trehalose-only formulation was hypothesized to come from osmotic pressure-induced vaccine destabilization. We found that inclusion of a viscosity enhancer, carboxymethyl cellulose, overcame this effect and retained full vaccine activity on both washed and plasma-cleaned titanium surfaces. The addition of polymeric surfactant, Lutrol® micro 68, to the trehalose formulation generated phase transformations of the vaccine coating, such as crystallization and phase separation, which was correlated to additional vaccine activity loss, especially when coating on hydrophilic, plasma-cleaned titanium. Again, the addition of a viscosity enhancer suppressed the surfactant-induced phase transformations during drying, which was confirmed by in vivo assessment of antibody response and survival rate after immunization in mice. We conclude that trehalose and a viscosity enhancer are beneficial coating excipients, but the inclusion of surfactant is detrimental to vaccine stability. PMID:23246470

Kerr effect in the isotropic phase of a side-chain polymeric liquid crystal

NASA Astrophysics Data System (ADS)

Reys, V.; Dormoy, Y.; Collin, D.; Keller, P.; Martinoty, P.

1992-02-01

The birefringence induced by a pulsed electrical field was used to study the pretransitional effects associated with the isotropic phase of a side-chain polysiloxane. The results obtained show that these effects are characterised by a conventional value of the static exponent and an abnormal value of the dynamic exponent, which shows that the dynamic theory of low molecular weight liquid crystals does not apply. The results also reveal competition between the dipolar moments induced by the electrical field and the permanent moments of the mesogenic molecules. La biréfringence induite par un champ électrique impulsionnel a été utilisée pour étudier les effets prétransitionnels associés à la phase isotrope d'un polysiloxane à chaînes latérales. Les résultats obtenus montrent que ces effets sont caractérisés par une valeur classique de l'exposant statique et une valeur anormale de l'exposant dynamique. Ce dernier résultat montre que la théorie dynamique des cristaux liquides de bas poids moléculaire n'est pas applicable au cas présent. Les expériences mettent également en évidence une compétition entre les moments dipolaires induits par le champ électrique et les moments permanents des molécules mésogènes.

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures

NASA Astrophysics Data System (ADS)

Farquet, Patrick; Padeste, Celestino; Solak, Harun H.; Gürsel, Selmiye Alkan; Scherer, Günther G.; Wokaun, Alexander

2007-12-01

Nanostructures of the thermoresponsive poly( N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 °C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures.

Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

NASA Astrophysics Data System (ADS)

Liu, Xiaoqiang; Hao, Junying; Xie, Yuntao

2016-08-01

Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

Composition and method of preparation of solid state dye laser rods

DOEpatents

Hermes, Robert E.

1992-01-01

The present invention includes solid polymeric-host laser rods prepared using bulk polymerization of acrylic acid ester comonomers which, when admixed with dye(s) capable of supporting laser oscillation and polymerized with a free radical initiator under mild thermal conditions, produce a solid product having the preferred properties for efficient lasing. Unsaturated polymerizable laser dyes can also be employed as one of the comonomers. Additionally, a method is disclosed which alleviates induced optical stress without having to anneal the polymers at elevated temperatures (>85.degree. C.).

Survey Study of Trunk Materials for Direct ATRP Grafting

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

Saito, Tomonori; Chatterjee, Sabornie; Johnson, Joseph C.

2015-02-01

In previous study, we demonstrated a new method to prepare polymeric fiber adsorbents via a chemical-grafting method, namely atom-transfer radical polymerization (ATRP), and identified parameters affecting their uranium adsorption capacity. However, ATRP chemical grafting in the previous study still utilized conventional radiation-induced graft polymerization (RIGP) to introduce initiation sites on fibers. Therefore, the objective of the present study is to perform survey study of trunk fiber materials for direct ATRP chemical grafting method without RIGP for the preparation of fiber adsorbents for uranium recovery from seawater.

Effects of viscoelasticity on drop impact and spreading on a solid surface

NASA Astrophysics Data System (ADS)

Izbassarov, Daulet; Muradoglu, Metin

2016-06-01

The effects of viscoelasticity on drop impact and spreading on a flat solid surface are studied computationally using a finite-difference-front-tracking method. The finitely extensible nonlinear elastic-Chilcott-Rallison model is used to account for the fluid viscoelasticity. It is found that viscoelasticity favors advancement of contact line during the spreading phase, leading to a slight increase in the maximum spreading, in agreement with experimental observations [Huh, Jung, Seo, and Lee, Microfluid. Nanofluid. 18, 1221 (2015), 10.1007/s10404-014-1518-4]. However, in contrast with the well-known antirebound effects of polymeric additives, the viscoelasticity is found to enhance the tendency of the drop rebound in the receding phase. These results suggest that the antirebound effects are mainly due to the polymer-induced modification of wetting properties of the substrate rather than the change in the material properties of the drop fluid. A model is proposed to test this hypothesis. It is found that the model results in good qualitative agreement with the experimental observations and the antirebound behavior can be captured by the modification of surface wetting properties in the receding phase.

Molecular Engineering of Liquid Crystalline Polymers by Living Polymerization. 8. Influence of Molecular Weight on the Phase Behavior pf Poly(Omega-((4-cyano-4’Biphenyl)oxy)alkyl Vinyl Ether)s with Ethyl, Propyl and Butyl Alkyl Groups

DTIC Science & Technology

1990-10-16

methanol (15 ml). The mixture was refluxed for 12 hr. After cooling and filtration (to remove the catalyst ) the solvent was distilled in a rotavapor and...was controlled by the monomer/initiator ([M]/[I]0 ) ratio. After quenching the polymerization with ammoniacal methanol , the reaction mixture was...The Phase Behavior of Poly(co-[(4-cyano-4’- biphenyl)oxy] alkyl Vinyl Ether]s with Ethyl, Propyl and Butyl Alkyl Groups Acc,--.o ,; ., x .... V

Effect of the Polymeric Stabilizer in the Aqueous Phase Fischer-Tropsch Synthesis Catalyzed by Colloidal Cobalt Nanocatalysts

PubMed Central

Delgado, Jorge A.; Claver, Carmen; Castillón, Sergio; Curulla-Ferré, Daniel; Godard, Cyril

2017-01-01

A series of small and well defined cobalt nanoparticles were synthesized by the chemical reduction of cobalt salts in water using NaBH4 as a reducing agent and using various polymeric stabilizers. The obtained nanocatalysts of similar mean diameters (ca. 2.6 nm) were fully characterized and tested in the aqueous phase Fischer-Tropsch Synthesis (AFTS). Interestingly, the nature and structure of the stabilizers used during the synthesis of the CoNPs affected the reduction degree of cobalt and the B-doping of these NPs and consequently, influenced the performance of these nanocatalysts in AFTS. PMID:28336892

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors.

PubMed

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-23

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm(-2) at 1 mA cm(-2), good flexibility with a higher value (204.6 mF cm(-2)) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg(-1) (with a power density of 3.2 kW kg(-1)) and a maximum power density of 4.2 kW kg(-1) (with an energy density of 3.1 Wh kg(-1)). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

An easily regenerable enzyme reactor prepared from polymerized high internal phase emulsions.

PubMed

Ruan, Guihua; Wu, Zhenwei; Huang, Yipeng; Wei, Meiping; Su, Rihui; Du, Fuyou

2016-04-22

A large-scale high-efficient enzyme reactor based on polymerized high internal phase emulsion monolith (polyHIPE) was prepared. First, a porous cross-linked polyHIPE monolith was prepared by in-situ thermal polymerization of a high internal phase emulsion containing styrene, divinylbenzene and polyglutaraldehyde. The enzyme of TPCK-Trypsin was then immobilized on the monolithic polyHIPE. The performance of the resultant enzyme reactor was assessed according to the conversion ability of Nα-benzoyl-l-arginine ethyl ester to Nα-benzoyl-l-arginine, and the protein digestibility of bovine serum albumin (BSA) and cytochrome (Cyt-C). The results showed that the prepared enzyme reactor exhibited high enzyme immobilization efficiency and fast and easy-control protein digestibility. BSA and Cyt-C could be digested in 10 min with sequence coverage of 59% and 78%, respectively. The peptides and residual protein could be easily rinsed out from reactor and the reactor could be regenerated easily with 4 M HCl without any structure destruction. Properties of multiple interconnected chambers with good permeability, fast digestion facility and easily reproducibility indicated that the polyHIPE enzyme reactor was a good selector potentially applied in proteomics and catalysis areas. Copyright © 2016 Elsevier Inc. All rights reserved.

The role of disclinations on the organization and conductivity in liquid crystal nanocomposites

NASA Astrophysics Data System (ADS)

Martinez-Miranda, Luz J.; Romero-Hasler, P.; Meneses-Franco, A.; Soto-Bustamante, E. A.

The structure of TiO2 nanoparticles in a liquid crystal nanocomposite was found to be an oblique structure due to the alignment of the TiO2 with respect to the liquid crystals. This order is anisotropic due to the ordering of the liquid crystals. The particles are highly localized in the nanocomposite, which has consequences in the electrical percolation. We want to obtain an understanding of how the nanoparticles organize in this highly localized fashion. The nanoparticles and the liquid crystals phase separate, with the nanoparticles accumulating in the defects exhibited by the liquid crystal even after being sonicated initially. The liquid crystal is polymerized by the process of electropolymerization that takes place in the isotropic phase of the monomers. The nanoparticles are free to move away from the defects where they phase separate since the defects disappear in the isotropic. We believe the polymerization imposes a limitation in the movement of the nanoparticles. The combination of the accumulation in the disclinations, the polymerization in the isotropic and the formation of the liquid crystal unit side chains can affect the conductivity of the nanocomposite. NSF-OISE-1157589; Fondecyt Project 1130187; CONICYT scholarships 21130413 and 21090713.

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-01

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm-2 at 1 mA cm-2, good flexibility with a higher value (204.6 mF cm-2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg-1 (with a power density of 3.2 kW kg-1) and a maximum power density of 4.2 kW kg-1 (with an energy density of 3.1 Wh kg-1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

Highly stabilized, polymer-lipid membranes prepared on silica microparticles as stationary phases for capillary chromatography

PubMed Central

Gallagher, Elyssia S.; Adem, Seid M.; Baker, Christopher A.; Ratnayaka, Saliya N.; Jones, Ian W.; Hall, Henry K.; Saavedra, S. Scott; Aspinwall, Craig A.

2015-01-01

The ability to rapidly screen complex libraries of pharmacological modulators is paramount to modern drug discovery efforts. This task is particularly challenging for agents that interact with lipid bilayers or membrane proteins due to the limited chemical, physical, and temporal stability of conventional lipid-based chromatographic stationary phases. Here, we describe the preparation and characterization of a novel stationary phase material composed of highly stable, polymeric-phospholipid bilayers self-assembled onto silica microparticles. Polymer lipid membranes were prepared by photochemical or redox initiated polymerization of 1,2-bis[10-(2′,4′-hexadieoyloxy)decanoyl]-sn-glycero-2-phosphocholine (bis-SorbPC), a synthetic, polymerizable lipid. The resulting polymerized bis-SorbPC (poly(bis-SorbPC)) stationary phases exhibited enhanced stability compared to particles coated with 1,2-dioleoyl-sn-glycero-phosphocholine (unpolymerized) phospholipid bilayers when exposed to chemical (50mM triton X-100 or 50% acetonitrile) and physical (15 min sonication) insults after 30 days of storage. Further, poly(bis-SorbPC)-coated particles survived slurry packing into fused silica capillaries, compared to unpolymerized lipid membranes, where the lipid bilayer was destroyed during packing. Frontal chromatographic analyses of the lipophilic small molecules acetylsalicylic acid, benzoic acid, and salicylic acid showed > 44% increase in retention times (P < 0.0001) for all analytes on poly(bis-SorbPC)-functionalized stationary phase compared to bare silica microspheres, suggesting a lipophilic retention mechanism. Phospholipid membrane-functionalized stationary phases that withstand the chemical and physical rigors of capillary LC conditions can substantially increase the efficacy of lipid membrane affinity chromatography, and represents a key advance towards the development of robust membrane protein-functionalized chromatographic stationary phases. PMID:25670414

Targeting Src and tubulin in mucinous ovarian carcinoma

PubMed Central

Liu, Tao; Hu, Wei; Dalton, Heather J.; Choi, Hyun Jin; Huang, Jie; Kang, Yu; Pradeep, Sunila; Miyake, Takahito; Song, Jian H.; Wen, Yunfei; Lu, Chunhua; Pecot, Chad V.; Bottsford-Miller, Justin; Zand, Behrouz; Jennings, Nicholas B; Ivan, Cristina; Gallick, Gary E.; Baggerly, Keith A; Hangauer, David G.; Coleman, Robert L.; Frumovitz, Michael; Sood, Anil K.

2013-01-01

Purpose To investigate the antitumor effects of targeting Src and tubulin in mucinous ovarian carcinoma. Experimental design The in vitro and in vivo effects and molecular mechanisms of KX-01, which inhibits Src pathway and tubulin polymerization, were examined in mucinous ovarian cancer models. Results In vitro studies using RMUG-S and RMUG-L cell lines showed that KX-01 inhibited cell proliferation, induced apoptosis, arrested the cell cycle at the G2/M phase, and enhanced the cytotoxicity of oxaliplatin in the KX-01-sensitive cell line, RMUG-S. In vivo studies showed that KX-01 significantly decreased tumor burden in RMUG-S and RMUG-L mouse models relative to untreated controls, and the effects were greater when KX-01 was combined with oxaliplatin. KX-01 alone and in combination with oxaliplatin significantly inhibited tumor growth by reducing cell proliferation and inducing apoptosis in vivo. PTEN knock-in experiments in RMUG-L cells showed improved response to KX-01. Reverse phase protein array analysis showed that in addition to blocking downstream molecules of Src family kinases, KX-01 also activated acute stress-inducing molecules. Conclusion Our results showed that targeting both the Src pathway and tubulin with KX-01 significantly inhibited tumor growth in preclinical mucinous ovarian cancer models, suggesting that this may be a promising therapeutic approach for patients with mucinous ovarian carcinoma. PMID:24100628

Adsorption and electron-induced polymerization of methyl methacrylate on Ru(101xAF0)

NASA Astrophysics Data System (ADS)

Hedhili, M. N.; Yakshinskiy, B. V.; Wasielewski, R.; Ciszewski, A.; Madey, T. E.

2008-05-01

The adsorption and electron irradiation of methyl methacrylate (MMA) on a Ru(101¯0) surface have been studied using x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and low energy ion scattering. TPD analysis indicates that a monolayer of MMA chemisorbs and dissociates on the Ru(101¯0) surface. The reaction products observed upon heating include H2, CO, CO2, and a small amount of MMA. Physisorbed multilayers of MMA desorb at temperatures around 170K. Electron irradiation of physisorbed MMA at 140K leads to a modification of the MMA film: The XPS spectra show an increase in thermal stability of the film with retention of the MMA structure, and indicate that electron irradiation induces polymerization. An increase in the electron bombardment fluence induces a degradation of the formed polymerized species and leads to the accumulation of carbon on the Ru surface. These results are relevant to the accumulation of carbon on surfaces of Ru films that serve as capping layers on Mo /Si multilayer mirrors used in extreme ultraviolet lithography.

Dynamical organization of the cytoskeletal cortex probed by micropipette aspiration

PubMed Central

Brugués, Jan; Maugis, Benoit; Casademunt, Jaume; Nassoy, Pierre; Amblard, François; Sens, Pierre

2010-01-01

Bleb-based cell motility proceeds by the successive inflation and retraction of large spherical membrane protrusions (“blebs”) coupled with substrate adhesion. In addition to their role in motility, cellular blebs constitute a remarkable illustration of the dynamical interactions between the cytoskeletal cortex and the plasma membrane. Here we study the bleb-based motions of Entamoeba histolytica in the constrained geometry of a micropipette. We construct a generic theoretical model that combines the polymerization of an actin cortex underneath the plasma membrane with the myosin-generated contractile stress in the cortex and the stress-induced failure of membrane-cortex adhesion. One major parameter dictating the cell response to micropipette suction is the stationary cortex thickness, controlled by actin polymerization and depolymerization. The other relevant physical parameters can be combined into two characteristic cortex thicknesses for which the myosin stress (i) balances the suction pressure and (ii) provokes membrane-cortex unbinding. We propose a general phase diagram for cell motions inside a micropipette by comparing these three thicknesses. In particular, we theoretically predict and experimentally verify the existence of saltatory and oscillatory motions for a well-defined range of micropipette suction pressures. PMID:20713731

Characterization of extracellular polymeric substances of Bacillus amyloliquefaciens SQR9 induced by root exudates of cucumber.

PubMed

Kimani, Veronicah Njeri; Chen, Lin; Liu, Yunpeng; Raza, Waseem; Zhang, Nan; Mungai, Lewis Kamau; Shen, Qirong; Zhang, Ruifu

2016-11-01

Bacillus amyloliquefaciens SQR9 is a plant growth-promoting rhizobacterium (PGPRs) that forms biofilm on the roots of plants and protects them from a variety of pathogens. In this study, we reported the effect of root exudates produced by cucumber (Cucumis sativus L.) at different developmental stages on the biochemical composition of the biofilm matrix of SQR9. The results showed that the amino acids present in the root exudates of cucumber were responsible for triggering biofilm formation of SQR9. In addition, when root exudates harvested at different growth phases of cucumber were used as carbon sources for biofilm formation, the resulting biofilm matrixes differed both quantitatively and qualitatively. The biofilm matrix was mostly composed of amino groups observed by confocal laser scanning microscope (CLSM) hence the proteins formed the major component of the resulting extracellular polymeric substances (EPS). The potential use of amino acid-based dietary supplements to control biofilm formation in the plants may be a viable option to improve agricultural productivity by recruiting beneficial association with PGPRs in the manufacture of bio fertilizers or bio controls. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diversity of Innate Immune Recognition Mechanism for Bacterial Polymeric meso-Diaminopimelic Acid-type Peptidoglycan in Insects

PubMed Central

Yu, Yang; Park, Ji-Won; Kwon, Hyun-Mi; Hwang, Hyun-Ok; Jang, In-Hwan; Masuda, Akiko; Kurokawa, Kenji; Nakayama, Hiroshi; Lee, Won-Jae; Dohmae, Naoshi; Zhang, Jinghai; Lee, Bok Luel

2010-01-01

In Drosophila, the synthesis of antimicrobial peptides in response to microbial infections is under the control of the Toll and immune deficiency (Imd) signaling pathway. The Toll signaling pathway responds mainly to the lysine-type peptidoglycan of Gram-positive bacteria and fungal β-1,3-glucan, whereas the Imd pathway responds to the meso-diaminopimelic acid (DAP)-type peptidoglycan of Gram-negative bacteria and certain Gram-positive bacilli. Recently we determined the activation mechanism of a Toll signaling pathway biochemically using a large beetle, Tenebrio molitor. However, DAP-type peptidoglycan recognition mechanism and its signaling pathway are still unclear in the fly and beetle. Here, we show that polymeric DAP-type peptidoglycan, but not its monomeric form, formed a complex with Tenebrio peptidoglycan recognition protein-SA, and this complex activated the three-step proteolytic cascade to produce processed Spätzle, a Toll receptor ligand, and induced Drosophila defensin-like antimicrobial peptide in Tenebrio larvae similarly to polymeric lysine-type peptidoglycan. Monomeric DAP-type peptidoglycan induced Drosophila diptericin-like antimicrobial peptide in Tenebrio hemocytes. In addition, both polymeric and monomeric DAP-type peptidoglycans induced expression of Tenebrio peptidoglycan recognition protein-SC2, which is DAP-type peptidoglycan-selective N-acetylmuramyl-l-alanine amidase that functions as a DAP-type peptidoglycan scavenger, appearing to function as a negative regulator of the DAP-type peptidoglycan signaling by cleaving DAP-type peptidoglycan in Tenebrio larvae. Taken together, these results demonstrate that molecular recognition mechanism for polymeric DAP-type peptidoglycan is different between Tenebrio larvae and Drosophila adults, providing biochemical evidences of biological diversity of innate immune responses in insects. PMID:20702416

Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure.

PubMed

Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

2014-04-25

A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure. Copyright © 2014 Elsevier B.V. All rights reserved.

Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics.

PubMed

Xu, Xiaojin; Ni, Xinjiong; Cao, Yuhua; Zhuo, Xiaolu; Yang, Xiaoxiao; Cao, Guangqun

2014-03-01

Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A simple method to separate red wine nonpolymeric and polymeric phenols by solid-phase extraction.

PubMed

Pinelo, Manuel; Laurie, V Felipe; Waterhouse, Andrew L

2006-04-19

Simple polyphenols and tannins differ in the way that they contribute to the organoleptic profile of wine and their effects on human health. Very few straightforward techniques to separate red wine nonpolymeric phenols from the polymeric fraction are available in the literature. In general, they are complex, time-consuming, and generate large amounts of waste. In this procedure, the separation of these compounds was achieved using C18 cartridges, three solvents with different elution strengths, and pH adjustments of the experimental matrices. Two full factorial 2(3) experimental designs were performed to find the optimal critical variables and their values, allowing for the maximization of tannin recovery and separation efficiency (SE). Nonpolymeric phenols such as phenolic acids, monomers, and oligomers of flavonol and flavan-3-ols and anthocyanins were removed from the column by means of an aqueous solvent followed by ethyl acetate. The polymeric fraction was then eluted with a combination of methanol/acetone/water. The best results were attained with 1 mL of wine sample, a 10% methanol/water solution (first eluant), ethyl acetate (second eluant), and 66% acetone/water as the polymeric phenols-eluting solution (third eluant), obtaining a SE of ca. 90%. Trials with this method on fruit juices also showed high separation efficiency. Hence, this solid-phase extraction method has been shown to be a simple and efficient alternative for the separation of nonpolymeric phenolic fractions and the polymeric ones, and this method could have important applications to sample purification prior to biological testing due to the nonspecific binding of polymeric phenolics to nearly all enzymes and receptor sites.

Polymerization on the rocks: beta-amino acids and arginine

NASA Technical Reports Server (NTRS)

Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

We have studied the accumulation of long oligomers of beta-amino acids on the surface of minerals using the 'polymerization on the rocks' protocol. We find that long oligopeptides of beta-glutamic acid which cannot be formed in homogeneous aqueous solution are accumulated efficiently on the surface of hydroxylapatite using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as condensing agent. The EDAC-induced oligomerization of aspartic acid on hydroxylapatite proceeds even more efficiently. Hydroxylapatite can also facilitate the ligation of the tripeptide (glu)3. The 'polymerization on the rocks' scenario is not restricted to negatively-charged amino acids. Oligoarginines are accumulated on the surface of illite using carbonyldiimidizole (CDI) as condensing agent. We find that FeS2 catalyzes the CDI-induced oligomerization of arginine, although it does not adsorb oligoarginines. These results are relevant to the formation of polypeptides on the primitive earth.

A novel headspace gas chromatographic method for in situ monitoring of monomer conversion during polymerization in an emulsion environment.

PubMed

Chai, Xin-Sheng; Zhong, Jin-Feng; Hu, Hui-Chao

2012-05-18

This paper describes a novel multiple-headspace extraction/gas chromatographic (MHE-GC) technique for monitoring monomer conversion during a polymerization reaction in a water-based emulsion environment. The polymerization reaction of methyl methacrylate (MMA) in an aqueous emulsion is used as an example. The reaction was performed in a closed headspace sample vial (as a mini-reactor), with pentane as a tracer. In situ monitoring of the vapor concentration of the tracer, employing a multiple headspace extraction (sampling) scheme, coupled to a GC, makes it possible to quantitatively follow the conversion of MMA during the early stages of polymerization. Data on the integrated amount of the tracer vapor released from the monomer droplet phase during the polymerization is described by a mathematic equation from which the monomer conversion can be calculated. The present method is simple, automated and economical, and provides an efficient tool in the investigation of the reaction kinetics and effects of the reaction conditions on the early stage of polymerization. Copyright © 2012 Elsevier B.V. All rights reserved.

Preparation of a polymeric ionic liquid-coated solid-phase microextraction fiber by surface radical chain-transfer polymerization with stainless steel wire as support.

PubMed

Feng, Juanjuan; Sun, Min; Xu, Lili; Li, Jubai; Liu, Xia; Jiang, Shengxiang

2011-10-28

Polymeric 1-vinyl-3-octylimidazolium hexafluorophosphate was synthesized in situ on stainless steel wire by surface radical chain-transfer polymerization and used as sensitive coatings in solid-phase microextraction. The outer surface of the stainless steel wire was firstly coated with microstructured silver layer via silver mirror reaction and then functionalized with self-assembled monolayers of 1,8-octanedithiol, which acted as chain transfer agent in the polymerization. Coupled to gas chromatography, extraction performance of the fiber was studied with both headspace and direct-immersion modes using benzene, toluene, ethylbenzene and xylenes (BTEX), phenols and polycyclic aromatic hydrocarbon (PAHs) as model analytes. In combination with the microstructured silver layer, the PIL-coated fiber exhibited high extraction efficiency. Linear ranges for BTEX with headspace mode were in the range of 0.2-1000 μg L(-1) for benzene, and 0.1-1000 μg L(-1) for toluene, ethylbenzene and xylenes. Limits of detection (LODs) were from 0.02 to 0.05 μg L(-1). Wide linear ranges of direct-immersion mode for the extraction of several phenols and PAHs were also obtained with correlation coefficients (R) from 0.9943 to 0.9997. The proposed fiber showed good durability with long lifetime. RSDs of 56 times extraction were still in an acceptable range, from 8.85 to 22.8%. Copyright © 2011 Elsevier B.V. All rights reserved.

Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization

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

Rakhymzhanov, A. M.; Utegulov, Z. N., E-mail: zhutegulov@nu.edu.kz, E-mail: fytas@mpip-mainz.mpg.de; Optics Laboratory, National Laboratory Astana, Nazarbayev University, Astana 10000

2016-05-16

The phononic band diagram of a periodic square structure fabricated by femtosecond laser pulse-induced two photon polymerization is recorded by Brillouin light scattering (BLS) at hypersonic (GHz) frequencies and computed by finite element method. The theoretical calculations along the two main symmetry directions quantitatively capture the band diagrams of the air- and liquid-filled structure and moreover represent the BLS intensities. The theory helps identify the observed modes, reveals the origin of the observed bandgaps at the Brillouin zone boundaries, and unravels direction dependent effective medium behavior.

A Critical Appraisal of RAFT-Mediated Polymerization-Induced Self-Assembly

PubMed Central

2016-01-01

Recently, polymerization-induced self-assembly (PISA) has become widely recognized as a robust and efficient route to produce block copolymer nanoparticles of controlled size, morphology, and surface chemistry. Several reviews of this field have been published since 2012, but a substantial number of new papers have been published in the last three years. In this Perspective, we provide a critical appraisal of the various advantages offered by this approach, while also pointing out some of its current drawbacks. Promising future research directions as well as remaining technical challenges and unresolved problems are briefly highlighted. PMID:27019522

Inverse relaxation effect of azo-dye molecules: The role of the film anisotropy

NASA Astrophysics Data System (ADS)

Sehnem, A. L.; Faita, F. L.; Cabrera, F. C.; Job, A. E.; Bechtold, I. H.

2013-11-01

We investigated the effect generally treated in the literature as inverse relaxation, which is related to an increase in the birefringence of azopolymer films after the inscription laser is turned off. The results demonstrate that films prepared with the casting method on anisotropic substrates induce a preferential organization of the polymeric chains. Inverse relaxation is evidenced only when the photo-alignment of the azo groups is induced parallel to the orientation of the polymeric chains. Thus, it is possible to enhance the optical storage in these systems with appropriate alignment methods.

Cofilin, But Not Profilin, Is Required for Myosin-I-Induced Actin Polymerization and the Endocytic Uptake in Yeast

PubMed Central

Idrissi, Fatima-Zahra; Wolf, Bianka L.; Geli, M. Isabel

2002-01-01

Mutations in the budding yeast myosins-I (MYO3 and MYO5) cause defects in the actin cytoskeleton and in the endocytic uptake. Robust evidence also indicates that these proteins induce Arp2/3-dependent actin polymerization. Consistently, we have recently demonstrated, using fluorescence microscopy, that Myo5p is able to induce cytosol-dependent actin polymerization on the surface of Sepharose beads. Strikingly, we now observed that, at short incubation times, Myo5p induced the formation of actin foci that resembled the yeast cortical actin patches, a plasma membrane-associated structure that might be involved in the endocytic uptake. Analysis of the machinery required for the formation of the Myo5p-induced actin patches in vitro demonstrated that the Arp2/3 complex was necessary but not sufficient in the assay. In addition, we found that cofilin was directly involved in the process. Strikingly though, the cofilin requirement seemed to be independent of its ability to disassemble actin filaments and profilin, a protein that closely cooperates with cofilin to maintain a rapid actin filament turnover, was not needed in the assay. In agreement with these observations, we found that like the Arp2/3 complex and the myosins-I, cofilin was essential for the endocytic uptake in vivo, whereas profilin was dispensable. PMID:12429847

Synthesis and characterization of new ion-imprinted polymer for separation and preconcentration of uranyl (UO2(2+)) ions.

PubMed

Ahmadi, Seyed Javad; Noori-Kalkhoran, Omid; Shirvani-Arani, Simindokht

2010-03-15

UO(2)(2+) ion-imprinted polymer materials used for solid-phase extraction were prepared by copolymerization of a ternary complex of uranyl ions with styrene and divinyl benzene in the presence of 2,2'-azobisisobutyronitrile. The imprinted particles were leached by HCl 6M. Various parameters in polymerization steps such as DVB/STY ratio, time of polymerization and temperature of polymerization were varied to achieve the most efficient uranyl-imprinted polymer. X-ray diffraction (XRD), infra-red spectroscopy (IR), thermo gravimetric analysis (TGA), UV-vis and nitrogen sorption were used to characterize the polymer particles. The XRD results showed that uranyl ions were completely removed from the polymer after leaching process. IR Analysis indicated that the N,N'-ethylenebis(pyridoxylideneiminato) remained intact in the polymer even after leaching. Some parameters such as pH, weight of the polymer, elution time, eluent volume and aqueous phase volume which affects the efficiency of the polymer were studied. (c) 2009 Elsevier B.V. All rights reserved.

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates and Method Relating Thereto

NASA Technical Reports Server (NTRS)

Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

1995-01-01

Production of an electric voltage in response to mechanical excitation (piezoelectricity) or thermal excitation (pyroelectricity) requires a material to have a preferred dipole orientation in its structure. This preferred orientation or polarization occurs naturally in some crystals such as quartz and can be induced into some ceramic and polymeric materials by application of strong electric or mechanical fields. For some materials, a combination of mechanical and electrical orientation is necessary to completely polarize the material. The only commercially available piezoelectric polymer is poly(vinylidene fluoride) (PVF2). However, this polymer has material and process limitations which prohibit its use in numerous device applications where thermal stability is a requirement. By the present invention, thermally stable, piezoelectric and pyroelectric polymeric substrates were prepared from polymers having a softening temperature greater than 1000C. A metal electrode material is deposited onto the polymer substrate and several electrical leads are attached to it. The polymer substrate is heated in a low dielectric medium to enhance molecular mobility of the polymer chains. A voltage is then applied to the polymer substrate inducing polarization. The voltage is then maintained while the polymer substrate is cooled 'freezing in' the molecular orientation. The novelty of the invention resides in the process of preparing the piezoelectric and pyroelectric polymeric substrate. The nonobviousness of the invention is found in heating the polymeric substrate in a low dielectric medium while applying a voltage.

Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization

PubMed Central

Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T.

2016-01-01

Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott—Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

Morphological and electro optic studies of polymer dispersed liquid crystal in reverse mode

NASA Astrophysics Data System (ADS)

Sharma, Vandna; Kumar, Pankaj; Chinky, Malik, Praveen; Raina, K. K.

2018-05-01

Present work deals with reverse mode polymer dispersed liquid crystals (PDLCs) sensitive to electric field. Contrary to the conventional PDLCs operate from opaque (OFF state) to transparent state (ON state) with the application of field, reverse mode PDLCs work in transparent to opaque state. Reverse mode PDLC composed of nematic LC and UV curable optical adhesive polymer were prepared by the polymerization induced phase separation. The polarizing optical microscope study shows the vertical alignment of LCs within droplets with initial dark state under cross polarizers and confirms preliminary natural transparent state. The electro optic (EO) results show that the reverse mode PDLC lowered the threshold and operating voltages significantly compared with reported values. The contrast ratio of the film was also studied.

Dialysis membrane for separation on microchips

DOEpatents

Singh, Anup K [San Francisco, CA; Kirby, Brian J [San Francisco, CA; Shepodd, Timothy J [Livermore, CA

2010-07-13

Laser-induced phase-separation polymerization of a porous acrylate polymer is used for in-situ fabrication of dialysis membranes inside glass microchannels. A shaped 355 nm laser beam is used to produce a porous polymer membrane with a thickness of about 15 .mu.m, which bonds to the glass microchannel and forms a semi-permeable membrane. Differential permeation through a membrane formed with pentaerythritol triacrylate was observed and quantified by comparing the response of the membrane to fluorescein and fluorescently tagging 200 nm latex microspheres. Differential permeation was observed and quantified by comparing the response to rhodamine 560 and lactalbumin protein in a membrane formed with SPE-methylene bisacrylamide. The porous membranes illustrate the capability for the present technique to integrate sample cleanup into chip-based analysis systems.

Transdermal thiol-acrylate polyethylene glycol hydrogel synthesis using near infrared light

NASA Astrophysics Data System (ADS)

Chung, Solchan; Lee, Hwangjae; Kim, Hyung-Seok; Kim, Min-Gon; Lee, Luke P.; Lee, Jae Young

2016-07-01

Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation via a mixed-mode reaction with a small increase in temperature (~5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications.Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation via a mixed-mode reaction with a small increase in temperature (~5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications. Electronic supplementary information (ESI) available: FE-SEM image of thiol-acrylate hydrogels; UV/Vis spectra of Ellman's assay; the temperature increase during transdermal photothermal hydrogelation. See DOI: 10.1039/c6nr01956k

AsS melt under pressure: one substance, three liquids.

PubMed

Brazhkin, V V; Katayama, Y; Kondrin, M V; Hattori, T; Lyapin, A G; Saitoh, H

2008-04-11

An in situ high-temperature--high-pressure study of liquid chalcogenide AsS by x-ray diffraction, resistivity measurements, and quenching from melt is presented. The obtained data provide direct evidence for the existence in the melt under compression of two transformations: one is from a moderate-viscosity molecular liquid to a high-viscosity nonmetallic polymerized liquid at P approximately 1.6-2.2 GPa; the other is from the latter to a low-viscosity metallic liquid at P approximately 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.

Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

DOE PAGES

Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; ...

2016-06-22

Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar 3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than inmore » the lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.« less

RhoA, Rac1, and Cdc42 differentially regulate αSMA and collagen I expression in mesenchymal stem cells.

PubMed

Ge, Jianfeng; Burnier, Laurent; Adamopoulou, Maria; Kwa, Mei Qi; Schaks, Matthias; Rottner, Klemens; Brakebusch, Cord

2018-06-15

Mesenchymal stem cells (MSC) are suggested to be important progenitors of myofibroblasts in fibrosis. To understand the role of Rho GTPase signaling in TGFβ-induced myofibroblast differentiation of MSC, we generated a novel MSC line and its descendants lacking functional Rho GTPases and Rho GTPase signaling components. Unexpectedly, our data revealed that Rho GTPase signaling is required for TGFβ-induced expression of α-smooth muscle actin (αSMA) but not of collagen I α1 ( col1a1 ). Whereas loss of RhoA and Cdc42 reduced αSMA expression, ablation of the Rac1 gene had the opposite effect. Although actin polymerization and MRTFa were crucial for TGFβ-induced αSMA expression, neither Arp2/3-dependent actin polymerization nor cofilin-dependent severing and depolymerization of F-actin were required. Instead, F-actin levels were dependent on cell contraction, and TGFβ-induced actin polymerization correlated with increased cell contraction mediated by RhoA and Cdc42. Finally, we observed impaired collagen I secretion in MSC lacking RhoA or Cdc42. These data give novel molecular insights into the role of Rho GTPases in TGFβ signaling and have implications for our understanding of MSC function in fibrosis. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Synthesis and characterization of polymeric V2O5/AlO(OH) with nanopores on alumina support.

PubMed

Ahmad, A L; Abd Shukor, S R; Leo, C P

2006-12-01

Polymeric vanadium pentoxide gel was formed via the reaction of V2O5 powder with hydrogen peroxide. The polymeric vanadium pentoxide gel was then dispersed in alumina gel. Different vanadium loading composites were coated on alumina support and calcined at 500 degrees C for 1 hr. These composite layers were characterized using TGA, FT-IR, XRD, SEM, and Autosorb. It was found that the lamellar structure of polymerized vanadium pentoxide was retained in the inorganic matrix. Crystalline alumina in gamma phase was formed after calcinations. However, the vanadium-alumina mixed oxides are lack of the well defined PXRD peaks for polycrystalline V2O5. This is possibly because the vanadia species are highly dispersed in the alumina matrix or the vanadia species are dispersed as crystalline which is smaller than 4 nm. In addition, the imbedded polymeric vanadium oxide improved the specific area and average pore diameter of the composite layer.

Role of Co-Vapors in Vapor Deposition Polymerization

PubMed Central

Lee, Ji Eun; Lee, Younghee; Ahn, Ki-Jin; Huh, Jinyoung; Shim, Hyeon Woo; Sampath, Gayathri; Im, Won Bin; Huh, Yang–Il; Yoon, Hyeonseok

2015-01-01

Polypyrrole (PPy)/cellulose (PPCL) composite papers were fabricated by vapor phase polymerization. Importantly, the vapor-phase deposition of PPy onto cellulose was assisted by employing different co-vapors namely methanol, ethanol, benzene, water, toluene and hexane, in addition to pyrrole. The resulting PPCL papers possessed high mechanical flexibility, large surface-to-volume ratio, and good redox properties. Their main properties were highly influenced by the nature of the co-vaporized solvent. The morphology and oxidation level of deposited PPy were tuned by employing co-vapors during the polymerization, which in turn led to change in the electrochemical properties of the PPCL papers. When methanol and ethanol were used as co-vapors, the conductivities of PPCL papers were found to have improved five times, which was likely due to the enhanced orientation of PPy chain by the polar co-vapors with high dipole moment. The specific capacitance of PPCL papers obtained using benzene, toluene, water and hexane co-vapors was higher than those of the others, which is attributed to the enlarged effective surface area of the electrode material. The results indicate that the judicious choice and combination of co-vapors in vapor-deposition polymerization (VDP) offers the possibility of tuning the morphological, electrical, and electrochemical properties of deposited conducting polymers. PMID:25673422

Characterization of polymeric solutions as injectable vehicles for hydroxyapatite microspheres.

PubMed

Oliveira, Serafim M; Almeida, Isabel F; Costa, Paulo C; Barrias, Cristina C; Ferreira, M Rosa Pena; Bahia, M Fernanda; Barbosa, Mário A

2010-06-01

A polymeric solution and a reinforcement phase can work as an injectable material to fill up bone defects. However, the properties of the solution should be suitable to enable the transport of that extra phase. Additionally, the use of biocompatible materials is a requirement for tissue regeneration. Thus, we intended to optimize a biocompatible polymeric solution able to carry hydroxyapatite microspheres into bone defects using an orthopedic injectable device. To achieve that goal, polymers usually regarded as biocompatible were selected, namely sodium carboxymethylcellulose, hydroxypropylmethylcellulose, and Na-alginate (ALG). The rheological properties of the polymeric solutions at different concentrations were assessed by viscosimetry before and after moist heat sterilization. In order to correlate rheological properties with injectability, solutions were tested using an orthopedic device applied for minimal invasive surgeries. Among the three polymers, ALG solutions presented the most suitable properties for our goal and a non-sterile ALG 6% solution was successfully used to perform preliminary injection tests of hydroxyapatite microspheres. Sterile ALG 7.25% solution was found to closely match non-sterile ALG 6% properties and it was selected as the optimal vehicle. Finally, sterile ALG 7.25% physical stability was studied at different temperatures over a 3-month period. It was observed that its rheological properties presented minor changes when stored at 25 degrees C or at 4 degrees C.

In-column bonded phase polymerization for improved packing uniformity

PubMed Central

Huckabee, Alexis G.; Yerneni, Charu; Jacobson, Rachel E.; Alzate, Edwin J.; Chen, Tse-Hong; Wirth, Mary J.

2017-01-01

It is difficult to pack chromatographic particles having polymeric-bonded phases because solvents used for making a stable slurry cause the polymer layer to swell. Growth of the polymer inside the column (in situ) after packing was investigated and compared with conventional, ex situ polymer growth. The method of activators generated by electron transfer, along with atom-transfer radical polymerization, enabled polymerization under ambient conditions. Nonporous, 0.62 µm silica particles with silane initiators were used. Polyacrylamide films with a hydrated thickness of 23 nm in 75:25 water/isopropanol grew in 55 min for both in situ and ex situ preparations, and the same carbon coverage was observed. Higher chromatographic resolution and better column-to-column reproducibility were observed for in situ polymer growth, as evaluated by hydrophilic interaction liquid chromatography for the model glycoprotein, ribonuclease B. In situ polymer growth was also found to give lower eddy diffusion, as shown by a narrower peak width for injected acetonitrile in 50:50 acetonitrile/water. When columns were packed more loosely, bed collapse occurred quickly for ex situ, but not for in situ, polymer growth. The higher resolution and stability for in situ polymer growth is explained by packing with hard, rather than soft, contacts between particles. PMID:28387037

Photonic devices based on patterning by two photon induced polymerization techniques

NASA Astrophysics Data System (ADS)

Fortunati, I.; Dainese, T.; Signorini, R.; Bozio, R.; Tagliazucca, V.; Dirè, S.; Lemercier, G.; Mulatier, J.-C.; Andraud, C.; Schiavuta, P.; Rinaldi, A.; Licoccia, S.; Bottazzo, J.; Franco Perez, A.; Guglielmi, M.; Brusatin, G.

2008-04-01

Two and three dimensional structures with micron and submicron resolution have been achieved in commercial resists, polymeric materials and sol-gel materials by several lithographic techniques. In this context, silicon-based sol-gel materials are particularly interesting because of their versatility, chemical and thermal stability, amount of embeddable active compounds. Compared with other micro- and nano-fabrication schemes, the Two Photon Induced Polymerization is unique in its 3D processing capability. The photopolymerization is performed with laser beam in the near-IR region, where samples show less absorption and less scattering, giving rise to a deeper penetration of the light. The use of ultrashort laser pulses allows the starting of nonlinear processes like multiphoton absorption at relatively low average power without thermally damaging the samples. In this work we report results on the photopolymerization process in hybrid organic-inorganic films based photopolymerizable methacrylate-containing Si-nanobuilding blocks. Films, obtained through sol-gel synthesis, are doped with a photo-initiator allowing a radical polymerization of methacrylic groups. The photo-initiator is activated by femtosecond laser source, at different input energies. The development of the unexposed regions is performed with a suitable solvent and the photopolymerized structures are characterized by microscopy techniques.

Actin Polymerization: An Event Regulated by Tyrosine Phosphorylation During Buffalo Sperm Capacitation.

PubMed

Naresh, S; Atreja, S K

2015-12-01

In the female reproductive tract, the spermatozoa undergo a series of physiological and biochemical changes, prior to gaining the ability to fertilize, that result to capacitation. However, the actin polymerization and protein tyrosine phosphorylation are the two necessary steps for capacitation. In this study, we have demonstrated the actin polymerization and established the correlation between protein tyrosine phosphorylation and actin reorganization during in vitro capacitation in buffalo (Bubalus bubalis) spermatozoa. Indirect immunofluorescence and Western blot techniques were used to detect actin polymerization and tyrosine phosphorylation. The time-dependent fluorimetric studies revealed that the actin polymerization starts from the tail region and progressed towards the head region of spermatozoa during capacitation. The lysophosphatidyl choline (LPC)-induced acrosome reaction (AR) stimulated quick actin depolymerization. The inhibitor cytochalasin D (CD) blocked the in vitro capacitation by inhibiting the actin polymerization. In addition, we also performed different inhibitor (Genistein, H-89, PD9809 and GF-109) and enhancer (dbcAMP, H(2)O(2) and vanadate) studies on actin tyrosine phosphorylation and actin polymerization. The inhibitors of tyrosine phosphorylation inhibit actin tyrosine phosphorylation and polymerization, whereas enhancers of tyrosine phosphorylation stimulate F-actin formation and tyrosine phosphorylation. These observations suggest that the tyrosine phosphorylation regulates the actin polymerization, and both are coupled processes during capacitation of buffalo spermatozoa. © 2015 Blackwell Verlag GmbH.

Delayed photo-activation and addition of thio-urethane: Impact on polymerization kinetics and stress of dual-cured resin cements.

PubMed

Faria-E-Silva, André L; Pfeifer, Carmem S

2017-10-01

1) to determine the moment during the redox polymerization reaction of dual cure cements at which to photo-activate the material in order to reduce the polymerization stress, and 2) to evaluate possible synergistic effects between adding chain transfer agents and delayed photo-activation. The two pastes of an experimental dual-cure material were mixed, and the polymerization kinetics of the redox phase was followed. The moment when the material reached its maximum rate of redox polymerization (MRRP) of cement was determined. The degree of conversion (DC) and maximum rates of polymerization (Rp max ) were assessed for materials where: the photoactivation immediately followed material mixing, at MRRP, 1min before and 1min after MRRP. Thio-urethane (TU) additives were synthesized and added to the cement (20% wt), which was then cured under the same conditions. The polymerization kinetics was evaluated for both cements photo-activated immediately or at MRRP, followed by measurements of polymerization stress, flexural strength (FS) and elastic modulus (EM). Knoop hardness was measured before and after ethanol storage. Photo-activating the cement at or after MRRP reduced the Rp max and the polymerization stress. Addition of TU promoted additional and more significant reduction, while not affecting the Rp max . Greater hardness loss was observed for cements with TU, but the final hardness was similar for all experimental conditions. Addition of TU slightly reduced the EM and did not affect the FS. Delayed photo-activation and addition of TU significantly reduce the polymerization stress of dual-cured cements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Recent New Methodologies for Acetylenic Polymers with Advanced Functionalities.

PubMed

Qiu, Zijie; Han, Ting; Lam, Jacky W Y; Tang, Ben Zhong

2017-08-01

Polymers synthesized from acetylenic monomers often possess electronically unsaturated fused rings and thus show versatile optoelectronic properties and advanced functionalities. To expand the family of acetylenic polymers, development of new catalyst systems and synthetic routes is critically important. We summarize herein recent research progress on development of new methodologies towards functional polymers using alkyne building blocks since 2014. The polymerizations are categorized by the number of monomer components, namely homopolymerizations, two-component polymerizations, and multicomponent polymerizations. The properties and applications of acetylenic polymers, such as aggregation-induced emission, fluorescent photopatterning, light refraction, chemosensing, mechanochromism, chain helicity, etc., are also discussed.

Absence of first-order unbinding transitions of fluid and polymerized membranes

NASA Technical Reports Server (NTRS)

Grotehans, Stefan; Lipowsky, Reinhard

1990-01-01

Unbinding transitions of fluid and polymerized membranes are studied by renormalization-group (RG) methods. Two different RG schemes are used and found to give rather consistent results. The fixed-point structure of both RG's exhibits a complex behavior as a function of the decay exponent tau for the fluctuation-induced interaction of the membranes. For tau greater than tau(S2) interacting membranes can undergo first-order transitions even in the strong-fluctuation regime. These estimates for tau(S2) imply, however, that both fluid and polymerized membranes unbind in a continuous way in the absence of lateral tension.

p21-Activated kinase (Pak) regulates airway smooth muscle contraction by regulating paxillin complexes that mediate actin polymerization.

PubMed

Zhang, Wenwu; Huang, Youliang; Gunst, Susan J

2016-09-01

In airway smooth muscle, tension development caused by a contractile stimulus requires phosphorylation of the 20 kDa myosin light chain (MLC), which activates crossbridge cycling and the polymerization of a pool of submembraneous actin. The p21-activated kinases (Paks) can regulate the contractility of smooth muscle and non-muscle cells, and there is evidence that this occurs through the regulation of MLC phosphorylation. We show that Pak has no effect on MLC phosphorylation during the contraction of airway smooth muscle, and that it regulates contraction by mediating actin polymerization. We find that Pak phosphorylates the adhesion junction protein, paxillin, on Ser273, which promotes the formation of a signalling complex that activates the small GTPase, cdc42, and the actin polymerization catalyst, neuronal Wiskott-Aldrich syndrome protein (N-WASP). These studies demonstrate a novel role for Pak in regulating the contractility of smooth muscle by regulating actin polymerization. The p21-activated kinases (Pak) can regulate contractility in smooth muscle and other cell and tissue types, but the mechanisms by which Paks regulate cell contractility are unclear. In airway smooth muscle, stimulus-induced contraction requires phosphorylation of the 20 kDa light chain of myosin, which activates crossbridge cycling, as well as the polymerization of a small pool of actin. The role of Pak in airway smooth muscle contraction was evaluated by inhibiting acetylcholine (ACh)-induced Pak activation through the expression of a kinase inactive mutant, Pak1 K299R, or by treating tissues with the Pak inhibitor, IPA3. Pak inhibition suppressed actin polymerization and contraction in response to ACh, but it did not affect myosin light chain phosphorylation. Pak activation induced paxillin phosphorylation on Ser273; the paxillin mutant, paxillin S273A, inhibited paxillin Ser273 phosphorylation and inhibited actin polymerization and contraction. Immunoprecipitation analysis of tissue extracts and proximity ligation assays in dissociated cells showed that Pak activation and paxillin Ser273 phosphorylation triggered the formation of an adhesion junction signalling complex with paxillin that included G-protein-coupled receptor kinase-interacting protein (GIT1) and the cdc42 guanine exchange factor, βPIX (Pak interactive exchange factor). Assembly of the Pak-GIT1-βPIX-paxillin complex was necessary for cdc42 and neuronal Wiskott-Aldrich syndrome protein (N-WASP) activation, actin polymerization and contraction in response to ACh. RhoA activation was also required for the recruitment of Pak to adhesion junctions, Pak activation, paxillin Ser273 phosphorylation and paxillin complex assembly. These studies demonstrate a novel role for Pak in the regulation of N-WASP activation, actin dynamics and cell contractility. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

p21‐Activated kinase (Pak) regulates airway smooth muscle contraction by regulating paxillin complexes that mediate actin polymerization

PubMed Central

Zhang, Wenwu; Huang, Youliang

2016-01-01

Key points In airway smooth muscle, tension development caused by a contractile stimulus requires phosphorylation of the 20 kDa myosin light chain (MLC), which activates crossbridge cycling and the polymerization of a pool of submembraneous actin.The p21‐activated kinases (Paks) can regulate the contractility of smooth muscle and non‐muscle cells, and there is evidence that this occurs through the regulation of MLC phosphorylation.We show that Pak has no effect on MLC phosphorylation during the contraction of airway smooth muscle, and that it regulates contraction by mediating actin polymerization.We find that Pak phosphorylates the adhesion junction protein, paxillin, on Ser273, which promotes the formation of a signalling complex that activates the small GTPase, cdc42, and the actin polymerization catalyst, neuronal Wiskott–Aldrich syndrome protein (N‐WASP).These studies demonstrate a novel role for Pak in regulating the contractility of smooth muscle by regulating actin polymerization. Abstract The p21‐activated kinases (Pak) can regulate contractility in smooth muscle and other cell and tissue types, but the mechanisms by which Paks regulate cell contractility are unclear. In airway smooth muscle, stimulus‐induced contraction requires phosphorylation of the 20 kDa light chain of myosin, which activates crossbridge cycling, as well as the polymerization of a small pool of actin. The role of Pak in airway smooth muscle contraction was evaluated by inhibiting acetylcholine (ACh)‐induced Pak activation through the expression of a kinase inactive mutant, Pak1 K299R, or by treating tissues with the Pak inhibitor, IPA3. Pak inhibition suppressed actin polymerization and contraction in response to ACh, but it did not affect myosin light chain phosphorylation. Pak activation induced paxillin phosphorylation on Ser273; the paxillin mutant, paxillin S273A, inhibited paxillin Ser273 phosphorylation and inhibited actin polymerization and contraction. Immunoprecipitation analysis of tissue extracts and proximity ligation assays in dissociated cells showed that Pak activation and paxillin Ser273 phosphorylation triggered the formation of an adhesion junction signalling complex with paxillin that included G‐protein‐coupled receptor kinase‐interacting protein (GIT1) and the cdc42 guanine exchange factor, βPIX (Pak interactive exchange factor). Assembly of the Pak–GIT1–βPIX–paxillin complex was necessary for cdc42 and neuronal Wiskott–Aldrich syndrome protein (N‐WASP) activation, actin polymerization and contraction in response to ACh. RhoA activation was also required for the recruitment of Pak to adhesion junctions, Pak activation, paxillin Ser273 phosphorylation and paxillin complex assembly. These studies demonstrate a novel role for Pak in the regulation of N‐WASP activation, actin dynamics and cell contractility. PMID:27038336

Moisture-induced phase separation and recrystallization in amorphous solid dispersions.

PubMed

Luebbert, Christian; Sadowski, Gabriele

2017-10-30

Active Pharmaceutical Ingredients (APIs) are often dissolved in polymeric matrices to control the gastrointestinal dissolution and to stabilize the amorphous state of the API. During the pharmaceutical development of new formulations, stability studies via storage at certain temperature and relative humidity (RH) have to be carried out to verify the long-term thermodynamic stability of these formulations against unwanted recrystallization and moisture-induced amorphous-amorphous phase separation (MIAPS). This study focuses on predicting the MIAPS of API/polymer formulations at elevated RH. In a first step, the phase behavior of water-free formulations of ibuprofen (IBU) and felodipine (FEL) combined with the polymers poly(vinyl pyrrolidone) (PVP), poly(vinyl acetate) (PVAC) and poly (vinyl pyrrolidone-co-vinyl acetate) (PVPVA64) was determined experimentally by differential scanning calorimetry (DSC). The phase behavior of these water-free formulations was modeled using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). Based on this, the API solubility and MIAPS in the above-mentioned formulations at humid conditions was predicted in perfect agreement with the results of two-year lasting stability studies at 25°C/0% RH and 40°C/75% RH. MIAPS was predicted and also experimentally found for the FEL/PVP, FEL/PVPVA64 and IBU/PVP formulations, whereas MIAPS was neither predicted nor measured for the IBU/PVPVA64 system and PVAC-containing formulations. It was thus shown that the results of time-consuming long-term stability tests can be correctly predicted via thermodynamic modeling with PC-SAFT. Copyright © 2017 Elsevier B.V. All rights reserved.

Method for preparing dioxyheterocycle-based electrochromic polymers

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

Reynolds, John R.; Estrada, Leandro; Deininger, James

A method for preparing a conjugated polymer involves a DHAP polymerization of a 3,4-dioxythiophene, 3,4-dioxyfuran, or 3,4-dioxypyrrole and, optionally, at least one second conjugated monomer in the presence of a Pd or Ni comprising catalyst, an aprotic solvent, a carboxylic acid at a temperature in excess of 120.degree. C. At least one of the monomers is substituted with hydrogen reactive functionalities and at least one of the monomers is substituted with a Cl, Br, and/or I. The polymerization can be carried out at temperature of 140.degree. C. or more, and the DHAP polymerization can be carried out without a phosphinemore » ligand or a phase transfer agent. The resulting polymer can display dispersity less than 2 and have a degree of polymerization in excess of 10.« less

Influence of gamma irradiation on polymerization of pyrrole and glucose oxidase immobilization onto poly (pyrrole)/poly (vinyl alcohol) matrix

NASA Astrophysics Data System (ADS)

Idris, Sarada; A. Bakar, Ahmad Ashrif; Thevy Ratnam, Chantara; Kamaruddin, Nur Hasiba; Shaari, Sahbudin

2017-04-01

This paper describes the immobilization of glucose oxidase, GOx onto polymer matrix comprising of poly(pyrrole), PPy and poly(vinyl alcohol), PVA using gamma irradiation technique. Py/PVA-GOx film was prepared by spreading PVA:GOx, 1:1 solution onto dried pyrrole film and exposed to gamma irradiation from cobalt 60 source at doses ranging from 0 to 60 kGy. The films were subjected to structural and morphological analyses by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Field emission scanning electron microscope (FESEM) and Atomic-force microscopy (AFM) techniques. Similar studies were also made on pristine pyrrole film which served as control. The SEM and FTIR spectra of Py/PVA-GOx film revealed that pyrrole has been successfully polymerized through irradiation-induced reactions. The results on the morphological properties of the samples characterize using FESEM, SEM and AFM further confirmed the occurrence of radiation-induced modification of Py/PVA-GOx film. The FTIR spectra showed the existence of intermolecular interaction between polymer matrix and GOx indicating that GOx had been successfully immobilized onto Ppy/PVA matrix by radiation-induced reactions. Results revealed that radiation induced reactions such as polymerization of pyrrole, crosslinking of PVA, grafting between the adjacent PVA and pyrrole molecules as well as immobilization of GOx onto Ppy/PVA matrix occurred simultaneously upon gamma irradiation. The optimum dose for GOx immobilization in the polymer matrix found to be 40 kGy. Therefore it is clear that this irradiation technique offered a simple single process to produce Py/PVA-GOx film without additional crosslinking and polymerization agents.

Morphology of LDPE-poly(3-hydroxybutyrate) films

NASA Astrophysics Data System (ADS)

Ol'khov, A. A.; Vlasov, S. V.; Shibryaeva, L. S.; Kosenko, R. Yu.; Iordanskii, A. L.

2012-07-01

The structure and morphology of biodegradable extruded polymeric films based on LDPE and (PHB) were studied by a combination of methods including polarization IR spectroscopy, DSC, and scanning electron microscopy (SEM). The components of LDPE-PHB blends containing 1-32% PHB are immiscible and form morphological structures (phases) with well distinguishable phase boundaries between dispersed phase and dispersion matrix.

Effects of nitric oxide and its congeners on sickle red blood cell deformability.

PubMed

Belanger, Andrea M; Keggi, Christian; Kanias, Tamir; Gladwin, Mark T; Kim-Shapiro, Daniel B

2015-10-01

Sickle cell disease (SCD) is characterized by hemoglobin polymerization upon deoxygenation. Polymerization causes the sickle cells to become rigid and misshapen (sickling). Red blood cell (RBC) dehydration greatly increases polymerization. Cycles of sickling and unsickling cause an influx of calcium that leads to loss of potassium via the calcium-activated Gardos channel, which dehydrates the cells leading to increased polymerization. In this study the effects of nitric oxide (NO) and its congeners on RBC deformability were examined, focusing on sickle RBCs (sRBCs). RBCs from patients with SCD and from nonpatients were exposed to various compounds that release NO or its congeners. Intracellular calcium was increased using a calcium ionophore or cycling of oxygen tension for sRBCs. Deformability was measured by laser-assisted osmotic gradient ektacytometry. Consistent with a previous report, sodium nitroprusside (SNP) was found to protect against calcium-induced loss of deformability in normal RBCs, but (contrary to some previous reports) no effect of any NO donors was observed when calcium influx was not induced. Importantly, in studies of deoxygenation-induced dehydration of sRBCs, SNP resulted in substantial improvements in deformability (p = 0.036) and hydration (p = 0.024). Sodium nitrite showed similar trends. SNP was shown to have no effect on calcium influx, but reduced potassium efflux. These data suggest that SNP and perhaps certain nitrogen oxides (like nitrite) inhibit the Gardos channel and may be able to protect sickle cells from dehydration and thereby improve outcome in the disease. © 2015 AABB.

The Effect of Limited Diffusion and Wet-Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids.

PubMed

Higgs, Paul G

2016-06-08

A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction.

The Effect of Limited Diffusion and Wet–Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids

PubMed Central

Higgs, Paul G.

2016-01-01

A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction. PMID:27338479

Influence of Solutocapillary Convection on Macrovoid Defect Formation in Polymeric Membranes

NASA Technical Reports Server (NTRS)

Pekny, M. R.; Zartman, J.; Greenberg, A. R.; Todd, P.; Krantz, W. B.

2001-01-01

Macrovoids (MVs) are large (10-50 micrometers) pores often found in polymeric membranes prepared via phase-inversion techniques. They are generally considered undesirable, as they adversely affect the permeability properties and performance of polymeric membranes for microfiltration, ultrafiltration, and reverse osmosis. However, MVs can be useful in certain thin-film applications in which vapor transmission is necessary, or for use as reservoirs for enzymes or liquid membrane material. If more could be learned about the nature and causes of MV formation, it might be possible to devise techniques to control and/or prevent MV formation that are more effective than those currently employed. Two hypotheses for the MV growth mechanism have been advanced. Reuvers proposed that once initiated, MV growth can be attributed to diffusion of (primarily) solvent to the MV nuclei. Because this mechanism does not involve gross movement of the MV, the presence or absence of body forces such as buoyancy should not significantly affect MV growth. On the other hand, Shojaie et al. proposed that solutocapillary convection induced by a steep surface-tension gradient along the MV/bulk solution interface enhances mass transfer to the growing MV. This interfacial convection exerts a force that pulls the growing MV downward into the casting solution. Both buoyancy and viscous drag hinder MV growth by inhibiting this motion. Thus, removing the buoyancy force by casting in microgravity should augment MV growth according to this hypothesis. Whereas neither surface tension nor gravity has a significant effect on MV growth according to the first hypothesis, buoyancy forces should be important if the second hypothesis is correct. The overall goal of this research is to test these two hypotheses in order to improve our understanding of the MV growth processing solvent-cast polymeric membranes. Studying MV growth in low-gravity conditions is pivotal to our ability to discriminate between these two hypotheses.

Production methodologies of polymeric and hydrogel particles for drug delivery applications.

PubMed

Lima, Ana Catarina; Sher, Praveen; Mano, João F

2012-02-01

Polymeric particles are ideal vehicles for controlled delivery applications due to their ability to encapsulate a variety of substances, namely low- and high-molecular mass therapeutics, antigens or DNA. Micro and nano scale spherical materials have been developed as carriers for therapies, using appropriated methodologies, in order to achieve a prolonged and controlled drug administration. This paper reviews the methodologies used for the production of polymeric micro/nanoparticles. Emulsions, phase separation, spray drying, ionic gelation, polyelectrolyte complexation and supercritical fluids precipitation are all widely used processes for polymeric micro/nanoencapsulation. This paper also discusses the recent developments and patents reported in this field. Other less conventional methodologies are also described, such as the use of superhydrophobic substrates to produce hydrogel and polymeric particulate biomaterials. Polymeric drug delivery systems have gained increased importance due to the need for improving the efficiency and versatility of existing therapies. This allows the development of innovative concepts that could create more efficient systems, which in turn may address many healthcare needs worldwide. The existing methods to produce polymeric release systems have some critical drawbacks, which compromise the efficiency of these techniques. Improvements and development of new methodologies could be achieved by using multidisciplinary approaches and tools taken from other subjects, including nanotechnologies, biomimetics, tissue engineering, polymer science or microfluidics.

Preparation of three-dimensional mesoporous polymer in situ polymerization solid phase microextraction fiber and its application to the determination of seven chlorophenols.

PubMed

Wang, Xuemei; Wang, Huan; Huang, Pengfei; Ma, Xiaomin; Lu, Xiaoquan; Du, Xinzhen

2017-01-06

A superior solid-phase microextraction (SPME) fiber-coating material, three dimensional order mesoporous polymers with Ia-3d bicontinuous cubic structure (3D-OMPs) was in situ coated on a stainless steel wire by solvent evaporation induced self-assembly (EISA) and thermo-polymerization. Fourier-transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), small-angel X-ray diffraction (SAXRD), N 2 adsorption-desorption transmission, and thermogravimetry analysis (TGA) were applied to the characterization of the synthesized 3D-OMPs coating. The performance and feasibility of the homemade fiber was evaluated through direct immersion (DI) SPME followed by high-performance liquid chromatography-UV detector (HPLC-UV) for the simultaneous extraction of seven chlorophenols in water samples. Under the optimum conditions, the prepared fiber exhibited excellent extraction properties as compared to three commercial fibers, the DI-SPME-HPLC-UV method showed low limits of detection (0.32-1.85μgL -1 ), wide linear ranges (5.0-1000μgL -1 ), and acceptable reproducibility (relative standard deviation, RSD<7.6% for one fiber, RSD<8.9% for fiber to fiber). Moreover, the method was further successfully applied to the analysis of seven CPs in real samples with good recoveries (80.5-99.5%) and satisfactory precisions (RSD<9.2%). It was confirmed that the proposed method has high sensitivity, outstanding selectivity and good reproducibility to the determination of trace CPs in the environmental water. Copyright © 2016 Elsevier B.V. All rights reserved.

In situ reinforced polymers using low molecular weight compounds

NASA Astrophysics Data System (ADS)

Yordem, Onur Sinan

2011-12-01

The primary objective of this research is to generate reinforcing domains in situ during the processing of polymers by using phase separation techniques. Low molecular weight compounds were mixed with polymers where the process viscosity is reduced at process temperatures and mechanical properties are improved once the material system is cooled or reacted. Thermally induced phase separation and thermotropic phase transformation of low molar mass compounds were used in isotactic polypropylene (iPP) and poly(ether ether ketone) (PEEK) resins. Reaction induced phase separation was utilized in thermosets to generate anisotropic reinforcements. A new strategy to increase fracture toughness of materials was introduced. Simultaneously, enhancement in stiffness and reduction in process viscosity were also attained. Materials with improved rheological and mechanical properties were prepared by using thermotropic phase transformations of metal soaps in polymers (calcium stearate/iPP). Morphology and thermal properties were studied using WAXS, DSC and SEM. Mechanical and rheological investigation showed significant reduction in process viscosity and substantial improvement in fracture toughness were attained. Effects of molecular architecture of metal soaps were investigated in PEEK (calcium stearate/PEEK and sodium stearate/PEEK). The selected compounds reduced the process viscosity due to the high temperature co-continuous morphology of metal soaps. Unlike the iPP system that incorporates spherical particles, interaction between PEEK and metal soaps resulted in two discrete and co-continuous phases of PEEK and the metal stearates. DMA and melt rheology exhibited that sodium stearate/PEEK composites are stiffer. Effective moduli of secondary metal stearate phase were calculated using different composite theories, which suggested bicontinuous morphology to the metal soaps in PEEK. Use of low molecular weight crystallizable solvents was investigated in reactive systems. Formation of anisotropic reinforcements was evaluated using dimethyl sulfone (DMS) as the crystallizable diluent and diglycidyl ether of bisphenol-A (DGEBA)/m-phenylene diamine (mPDA) material system as the epoxy thermoset. Miscible blends of DMS and DGEBA/mPDA form homogenous mixtures that undergo polymerization induced phase separation, once the DGEBA oligomers react with mPDA. The effect of the competition between the crystallization and phase separation of DMS resulted in nano-wires to micro-scale fiber-like crystals that were generated by adjusting the reaction temperature and DMS concentration.

Covalently bonded networks through surface-confined polymerization

NASA Astrophysics Data System (ADS)

El Garah, Mohamed; MacLeod, Jennifer M.; Rosei, Federico

2013-07-01

The prospect of synthesizing ordered, covalently bonded structures directly on a surface has recently attracted considerable attention due to its fundamental interest and for potential applications in electronics and photonics. This prospective article focuses on efforts to synthesize and characterize epitaxial one- and two-dimensional (1D and 2D, respectively) polymeric networks on single crystal surfaces. Recent studies, mostly performed using scanning tunneling microscopy (STM), demonstrate the ability to induce polymerization based on Ullmann coupling, thermal dehalogenation and dehydration reactions. The 2D polymer networks synthesized to date have exhibited structural limitations and have been shown to form only small domains on the surface. We discuss different approaches to control 1D and 2D polymerization, with particular emphasis on the surface phenomena that are critical to the formation of larger ordered domains.

Large-scale filament formation inhibits the activity of CTP synthetase

PubMed Central

Barry, Rachael M; Bitbol, Anne-Florence; Lorestani, Alexander; Charles, Emeric J; Habrian, Chris H; Hansen, Jesse M; Li, Hsin-Jung; Baldwin, Enoch P; Wingreen, Ned S; Kollman, Justin M; Gitai, Zemer

2014-01-01

CTP Synthetase (CtpS) is a universally conserved and essential metabolic enzyme. While many enzymes form small oligomers, CtpS forms large-scale filamentous structures of unknown function in prokaryotes and eukaryotes. By simultaneously monitoring CtpS polymerization and enzymatic activity, we show that polymerization inhibits activity, and CtpS's product, CTP, induces assembly. To understand how assembly inhibits activity, we used electron microscopy to define the structure of CtpS polymers. This structure suggests that polymerization sterically hinders a conformational change necessary for CtpS activity. Structure-guided mutagenesis and mathematical modeling further indicate that coupling activity to polymerization promotes cooperative catalytic regulation. This previously uncharacterized regulatory mechanism is important for cellular function since a mutant that disrupts CtpS polymerization disrupts E. coli growth and metabolic regulation without reducing CTP levels. We propose that regulation by large-scale polymerization enables ultrasensitive control of enzymatic activity while storing an enzyme subpopulation in a conformationally restricted form that is readily activatable. DOI: http://dx.doi.org/10.7554/eLife.03638.001 PMID:25030911

Supramolecular "Step Polymerization" of Preassembled Micelles: A Study of "Polymerization" Kinetics.

PubMed

Yang, Chaoying; Ma, Xiaodong; Lin, Jiaping; Wang, Liquan; Lu, Yingqing; Zhang, Liangshun; Cai, Chunhua; Gao, Liang

2018-03-01

In nature, sophisticated functional materials are created through hierarchical self-assembly of nanoscale motifs, which has inspired the fabrication of man-made materials with complex architectures for a variety of applications. Herein, a kinetic study on the self-assembly of spindle-like micelles preassembled from polypeptide graft copolymers is reported. The addition of dimethylformamide and, subsequently, a selective solvent (water) can generate a "reactive point" at both ends of the spindles as a result of the existence of structural defects, which induces the "polymerization" of the spindles into nanowires. Experimental results combined with dissipative particle dynamics simulations show that the polymerization of the micellar subunits follows a step-growth polymerization mechanism with a second-order reaction characteristic. The assembly rate of the micelles is dependent on the subunit concentration and on the activity of the reactive points. The present work reveals a law governing the self-assembly kinetics of micelles with structural defects and opens the door for the construction of hierarchical structures with a controllable size through supramolecular step polymerization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Untemplated nonenzymatic polymerization of 3',5'cGMP: a plausible route to 3',5'-linked oligonucleotides in primordia.

PubMed

Šponer, Judit E; Šponer, Jiří; Giorgi, Alessandra; Di Mauro, Ernesto; Pino, Samanta; Costanzo, Giovanna

2015-02-19

The high-energy 3',5' phosphodiester linkages conserved in 3',5' cyclic GMPs offer a genuine solution for monomer activation required by the transphosphorylation reactions that could lead to the emergence of the first simple oligonucleotide sequences on the early Earth. In this work we provide an in-depth characterization of the effect of the reaction conditions on the yield of the polymerization reaction of 3',5' cyclic GMPs both in aqueous environment as well as under dehydrating conditions. We show that the threshold temperature of the polymerization is about 30 °C lower under dehydrating conditions than in solution. In addition, we present a plausible exergonic reaction pathway for the polymerization reaction, which involves transient formation of anionic centers at the O3' positions of the participating riboses. We suggest that excess Na(+) cations inhibit the polymerization reaction because they block the anionic mechanism via neutralizing the negatively charged O3'. Our experimental findings are compatible with a prebiotic scenario, where gradual desiccation of the environment could induce polymerization of 3',5' cyclic GMPs synthesized in liquid.

Observation and Kinematic Description of Long Actin Tracks Induced by Spherical Beads

PubMed Central

Kang, Hyeran; Perlmutter, David S.; Shenoy, Vivek B.; Tang, Jay X.

2010-01-01

We report an in vitro study comparing the growth of long actin tails induced by spherical beads coated with the verprolin central acidic domain of the polymerization enzyme N-WASP to that induced by Listeria monocytogenes in similar cellular extracts. The tracks behind the beads show characteristic differences in shape and curvature from those left by the bacteria, which have an elongated shape and a similar polymerization-inducing enzyme distributed only on the rear surface of the cell. The experimental tracks are simulated using a generalized kinematic model, which incorporates three modes of bead rotation with respect to the tail. The results show that the trajectories of spherical beads are mechanically deterministic rather than random, as suggested by stochastic models. Assessment of the bead rotation and its mechanistic basis offers insights into the biological function of actin-based motility. PMID:21044576

Magnon Hall effect without Dzyaloshinskii-Moriya interaction.

PubMed

Owerre, S A

2017-01-25

Topological magnon bands and magnon Hall effect in insulating collinear ferromagnets are induced by the Dzyaloshinskii-Moriya interaction (DMI) even at zero magnetic field. In the geometrically frustrated star lattice, a coplanar/noncollinear [Formula: see text] magnetic ordering may be present due to spin frustration. This magnetic structure, however, does not exhibit topological magnon effects even with DMI in contrast to collinear ferromagnets. We show that a magnetic field applied perpendicular to the star plane induces a non-coplanar spin configuration with nonzero spin scalar chirality, which provides topological effects without the need of DMI. The non-coplanar spin texture originates from the topology of the spin configurations and does not need the presence of DMI or magnetic ordering, which suggests that this phenomenon may be present in the chiral spin liquid phases of frustrated magnetic systems. We propose that these anomalous topological magnon effects can be accessible in polymeric iron (III) acetate-a star-lattice antiferromagnet with both spin frustration and long-range magnetic ordering.

H2O2 induced cost effective microwave disintegration of dairy waste activated sludge in acidic environment for efficient biomethane generation.

PubMed

Eswari, A Parvathy; Kavitha, S; Banu, J Rajesh; Karthikeyan, O Parthiba; Yeom, Ick-Tae

2017-11-01

This study aimed to improve the biomethane potential of dairy waste activated sludge (WAS) by H 2 O 2 -acidic pH induced microwave disintegration (HAMW-D) pretreatment approach. The results of HAMW-D compared with the microwave disintegration (MW-D) alone for energy and economic factors. In the two phase disintegration process, the H 2 O 2 concentration of about 0.5mg/g SS under acid pH of 5 was found to be optimum for effective dissociation of Extracellular Polymeric Substances (EPS) matrix. A higher liquefaction of about 46.6% was achieved in HAMW-D when compared to that of MW-D (30%). It subsequently improved the methane yield of about 250mL/g VS in HAMW-D, which was 9.6% higher than MW-D. A net profit of about 49€/ton was achieved for HAMW-D, therefore it is highly recommended for WAS pretreatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Two ultrastructurally distinct tubulin paracrystals induced in sea-urchin eggs by vinblastine sulphate.

PubMed

Starling, D

1976-01-01

Two types of ultrastructurally distinct tubulin paracrystals have been induced in sea-urchin eggs with vinblastine sulphate (VLB) under different sets of conditions. One type of paracrystal appears to consist of hexagonally-close packed microtubules and closely resembles paracrystals present in mammalian cells treated with vinblastine or vincristine sulphate, but not previously reported in sea-urchin eggs. The other type is also made up of tubulin subunits, but these do not seem to have polymerized into microtubules. Both types of paracrystal are induced in sea-urchin eggs in the presence of VLB at a time when tubulin subunits would not normally polymerize. Possible mechanisms for tubulin activation and the induction of paracrystal formation are discussed in respect to the available information on the binding sites of the tubulin subunits.

Doxorubicin Release Controlled by Induced Phase Separation and Use of a Co-Solvent.

PubMed

Park, Seok Chan; Yuan, Yue; Choi, Kyoungju; Choi, Seong-O; Kim, Jooyoun

2018-04-26

Electrospun-based drug delivery is emerging as a versatile means of localized therapy; however, controlling the release rates of active agents still remains as a key question. We propose a facile strategy to control the drug release behavior from electrospun fibers by a simple modification of polymer matrices. Polylactic acid (PLA) was used as a major component of the drug-carrier, and doxorubicin hydrochloride (Dox) was used as a model drug. The influences of a polar co-solvent, dimethyl sulfoxide (DMSO), and a hydrophilic polymer additive, polyvinylpyrrolidone (PVP), on the drug miscibility, loading efficiency and release behavior were investigated. The use of DMSO enabled the homogeneous internalization of the drug as well as higher drug loading efficiency within the electrospun fibers. The PVP additive induced phase separation in the PLA matrix and acted as a porogen. Preferable partitioning of Dox into the PVP domain resulted in increased drug loading efficiency in the PLA/PVP fiber. Fast dissolution of PVP domains created pores in the fibers, facilitating the release of internalized Dox. The novelty of this study lies in the detailed experimental investigation of the effect of additives in pre-spinning formulations, such as co-solvents and polymeric porogens, on the drug release behavior of nanofibers.

Doxorubicin Release Controlled by Induced Phase Separation and Use of a Co-Solvent

PubMed Central

Park, Seok Chan; Choi, Kyoungju; Choi, Seong-O

2018-01-01

Electrospun-based drug delivery is emerging as a versatile means of localized therapy; however, controlling the release rates of active agents still remains as a key question. We propose a facile strategy to control the drug release behavior from electrospun fibers by a simple modification of polymer matrices. Polylactic acid (PLA) was used as a major component of the drug-carrier, and doxorubicin hydrochloride (Dox) was used as a model drug. The influences of a polar co-solvent, dimethyl sulfoxide (DMSO), and a hydrophilic polymer additive, polyvinylpyrrolidone (PVP), on the drug miscibility, loading efficiency and release behavior were investigated. The use of DMSO enabled the homogeneous internalization of the drug as well as higher drug loading efficiency within the electrospun fibers. The PVP additive induced phase separation in the PLA matrix and acted as a porogen. Preferable partitioning of Dox into the PVP domain resulted in increased drug loading efficiency in the PLA/PVP fiber. Fast dissolution of PVP domains created pores in the fibers, facilitating the release of internalized Dox. The novelty of this study lies in the detailed experimental investigation of the effect of additives in pre-spinning formulations, such as co-solvents and polymeric porogens, on the drug release behavior of nanofibers. PMID:29701714

Dextran-5-(4-ethoxycarbonylphenylazo)salicylic acid ester, a polymeric colon-specific prodrug releasing 5-aminosalicylic acid and benzocaine, ameliorates TNBS-induced rat colitis.

PubMed

Nam, Joon; Kim, Wooseong; Lee, Sunyoung; Jeong, Seongkeun; Yoo, Jin-Wook; Kim, Min-Soo; Jung, Yunjin

2016-01-01

Local anesthetics have beneficial effects on colitis. Dextran-5-(4-ethoxycarbonylphenylazo)salicylic acid ester (Dex-5-ESA), designed as a polymeric colon-specific prodrug liberating 5-ASA and benzocaine in the large intestine, was prepared and its therapeutic activity against colitis was evaluated using a TNBS-induced rat colitis model. Dex-5-ESA liberated 5-ASA and benzocaine in the cecal contents while (bio)chemically stable in the small intestinal contents and mucosa. Oral administration of Dex-5-ESA (equivalent to 10 mg 5-ASA/kg, twice a day) alleviated colonic injury and reduced MPO activity in the inflamed colon. In parallel, pro-inflammatory mediators, COX-2, iNOS and CINC-3, elevated by TNBS-induced colitis, were substantially diminished in the inflamed colon. Dex-5-ESA was much more effective for the treatment of colitis than 5-(4-ethoxycarbonylphenylazo)salicylic acid (5-ESA) that may not deliver benzocaine to the large intestine. Our data suggest that Dex-5-ESA is a polymeric colon-specific prodrug, liberating 5-ASA and benzocaine in the target site (large intestine), probably exerting anti-colitic effects by combined action of 5-ASA and benzocaine.

Electron beam-induced graft polymerization of acrylic acid and immobilization of arginine-glycine-aspartic acid-containing peptide onto nanopatterned polycaprolactone.

PubMed

Sun, Hui; Wirsén, Anders; Albertsson, Ann-Christine

2004-01-01

Electron beam- (EB-) induced graft polymerization of acrylic acid and the subsequent immobilization of arginine-glycine-aspartic acid (RGD) peptide onto nanopatterned polycaprolactone with parallel grooves is reported. A high concentration of carboxylic groups was introduced onto the polymer substrate by EB-induced polymerization of acrylic acid. In the coupling of the RGD peptide to the carboxylated polymer surface, a three-step peptide immobilization process was used. This process included the activation of surface carboxylic acid into an active ester intermediate by use of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), the introduction of disulfide groups by use of 2-(2-pyridinyldithio)ethanamine hydrochloride (PDEA), and final immobilization of the peptide via a thiol-disulfide exchange reaction. The extent of coupling was measured by UV spectroscopy. A preliminary study of the in vitro behavior of keratinocytes (NCTC 2544) cultured on the acrylic acid-grafted and RGD peptide-coupled surface showed that most cells grown on the coupled samples had a spread-rounded appearance, while the majority of cells tended to be elongated along the grooves on uncoupled substrates.

A novel hybrid metal-organic framework-polymeric monolith for solid-phase microextraction.

PubMed

Lin, Chen-Lan; Lirio, Stephen; Chen, Ya-Ting; Lin, Chia-Her; Huang, Hsi-Ya

2014-03-17

This study describes the fabrication of a novel hybrid metal-organic framework- organic polymer (MOF-polymer) for use as a stationary phase in fritless solid-phase microextraction (SPME) for validating analytical methods. The MOF-polymer was prepared by using ethylene dimethacrylate (EDMA), butyl methacrylate (BMA), and an imidazolium-based ionic liquid as porogenic solvent followed by microwave-assisted polymerization with the addition of 25 % MOF. This novel hybrid MOF-polymer was used to extract penicillin (penicillin G, penicillin V, oxacillin, cloxacillin, nafcillin, dicloxacillin) under different conditions. Quantitative analysis of the extracted penicillin samples using the MOF-organic polymer for SPME was conducted by using capillary electrochromatography (CEC) coupled with UV analysis. The penicillin recovery was 63-96.2 % with high reproducibility, sensitivity, and reusability. The extraction time with the proposed fabricated SPME was only 34 min. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graft polymerization of wood sawdust and peat with ethylene carbonate. A novel method for the preparation of supports with enhanced mechanical properties to be used in biofiltration of organic vapors.

PubMed

Hernández-Meléndez, O; Peydecastaing, J; Bárzana, E; Vaca-Garcia, C; Hernández-Luna, M; Borredon, M E

2009-01-01

The graft polymerization reaction between ethylene carbonate (EC) and scots pine sawdust (SPS) or peat moss (PM) offers a solvent-free approach to the simple and inexpensive aliphatic derivatization of these lignocellulosic fibers. This reaction was studied with liquid or vapor EC phases in three different reactor configurations: batch stirred (BSR), semi-continuous stirred (SSR) and continuous tubular in the gas phase (CVTR). The use of a vapor phase allowed a satisfactory grafting yield and minimal production of non-grafted polyol by-products. The crosslinking agent 4,4'-methylenebis(phenylisocyanate) (MDI) achieved superior characteristics to form shaped tablets resistant to water disaggregation, a high water retention capacity and high compression strength, characteristics that conventional organic supports like PM or PM-polyurethane foam mixtures used in biofiltration of waste gases do not completely possess.

Monodisperse hydrogel microspheres by forced droplet formation in aqueous two-phase systems.

PubMed

Ziemecka, Iwona; van Steijn, Volkert; Koper, Ger J M; Rosso, Michel; Brizard, Aurelie M; van Esch, Jan H; Kreutzer, Michiel T

2011-02-21

This paper presents a method to form micron-sized droplets in an aqueous two-phase system (ATPS) and to subsequently polymerize the droplets to produce hydrogel beads. Owing to the low interfacial tension in ATPS, droplets do not easily form spontaneously. We enforce the formation of drops by perturbing an otherwise stable jet that forms at the junction where the two aqueous streams meet. This is done by actuating a piezo-electric bending disc integrated in our device. The influence of forcing amplitude and frequency on jet breakup is described and related to the size of monodisperse droplets with a diameter in the range between 30 and 60 μm. Rapid on-chip polymerization of derivatized dextran inside the droplets created monodisperse hydrogel particles. This work shows how droplet-based microfluidics can be used in all-aqueous, surfactant-free, organic-solvent-free biocompatible two-phase environment.

Molecular organization and dynamics of micellar phase of polyelectrolyte-surfactant complexes: ESR spin probe study

NASA Astrophysics Data System (ADS)

Wasserman, A. M.; Kasaikin, V. A.; Zakharova, Yu. A.; Aliev, I. I.; Baranovsky, V. Yu.; Doseva, V.; Yasina, L. L.

2002-04-01

Molecular dynamics and organization of the micellar phase of complexes of linear polyelectrolytes with ionogenic and non-ionogenic surfactants was studied by the ESR spin probe method. Complexes of polyacrylic acid (PAA) and sodium polystyrenesulfonate (PSS) with alkyltrimethylammonium bromides (ATAB), as well as complexes of poly- N, N'-dimethyldiallylammonium chloride (PDACL) with sodium dodecylsulfate (SDS) were studied. The micellar phase of such complexes is highly organized molecular system, molecular ordering of which near the polymeric chain is much higher than in the 'center' of the micelle, it depends on the polymer-detergent interaction, flexibility of polymeric chain and length of carbonic part of the detergent molecule. Complexes of polymethacrylic acid (PMAA) with non-ionic detergent (dodecyl-substituted polyethyleneglycol), show that the local mobility of surfactant in such complexes is significantly lower than in 'free' micelles and depends on the number of micellar particles participating in formation of complexes.

Ternary Polymeric Composites Exhibiting Bulk and Surface Quadruple-Shape Memory Properties.

PubMed

Buffington, Shelby Lois; Posnick, Benjamin M; Paul, Justine Elizabeth; Mather, Patrick T

2018-06-19

We report the design and characterization of a multiphase quadruple shape memory composite capable of switching between 4 programmed shapes, three temporary and one permanent. Our approach combined two previously reported fabrication methods by embedding an electrospun mat of PCL in a miscible blend of epoxy monomers and PMMA as a composite matrix. As epoxy polymerization occurred the matrix underwent phase separation between the epoxy and PMMA materials. This created a multiphase composite with PCL fibers and a two-phase matrix composed of phase-separated epoxy and PMMA. The resulting composite demonstrated three separate thermal transitions and amenability to mechanical programming of three separate temporary shapes in addition to one final, equilibrium shape. In addition, quadruple surface shape memory abilities are successfully demonstrated. The versatility of this approach offers a large degree of design flexibility for multi-shape memory materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sulfamic acid promoted one-pot synthesis of phenanthrene fused-dihydrodibenzo-quinolinones: Anticancer activity, tubulin polymerization inhibition and apoptosis inducing studies.

PubMed

Kumar, Niggula Praveen; Thatikonda, Sowjanya; Tokala, Ramya; Kumari, S Sujana; Lakshmi, Uppu Jaya; Godugu, Chandraiah; Shankaraiah, Nagula; Kamal, Ahmed

2018-05-01

A facile one-pot method for the synthesis of new phenanthrene fused-dihydrodibenzo-quinolinone derivatives has been successfully accomplished by employing sulfamic acid as catalyst. These new compounds were evaluated for their in vitro cytotoxic potential against human lung (A549), prostate (PC-3 and DU145), breast (MCF-7) and colon (HT-29 and HCT-116) cancer cell lines. Among all the tested compounds, one of the derivatives 8p showed good anti-proliferative activity against A549 lung cancer cell line with an IC 50 of 3.17 ± 0.52 µM. Flow cytometric analyses revealed that compound 8p arrested both Sub G1 and G2/M phases of cell cycle in a dose dependent manner. The compound 8p also displayed significant inhibition of tubulin polymerization and disruption of microtubule network (IC 50 of 5.15 ± 0.15 µM). Molecular docking studies revealed that compound 8p efficiently interacted with critical amino acid Cys241 of the α/β-tubulin by a hydrogen bond (SH…O = 2.4 Å). Further, the effect of 8p on cell viability was also studied by AO/EB, DCFDA and DAPI staining. The apoptotic characteristic features revealed that 8p inhibited cell proliferation effectively through apoptosis by inducing the ROS generation. Analysis of mitochondrial membrane potential through JC-1 staining and annexin V binding assay indicated the extent of apoptosis in A549 cancer cells. Copyright © 2018 Elsevier Ltd. All rights reserved.

Prolactin-Induced Protein Is Required for Cell Cycle Progression in Breast Cancer12

PubMed Central

Naderi, Ali; Vanneste, Marion

2014-01-01

Prolactin-induced protein (PIP) is expressed in the majority of breast cancers and is used for the diagnostic evaluation of this disease as a characteristic biomarker; however, the molecular mechanisms of PIP function in breast cancer have remained largely unknown. In this study, we carried out a comprehensive investigation of PIP function using PIP silencing in a broad group of breast cancer cell lines, analysis of expression microarray data, proteomic analysis using mass spectrometry, and biomarker studies on breast tumors. We demonstrated that PIP is required for the progression through G1 phase, mitosis, and cytokinesis in luminal A, luminal B, and molecular apocrine breast cancer cells. In addition, PIP expression is associated with a transcriptional signature enriched with cell cycle genes and regulates key genes in this process including cyclin D1, cyclin B1, BUB1, and forkhead box M1 (FOXM1). It is notable that defects in mitotic transition and cytokinesis following PIP silencing are accompanied by an increase in aneuploidy of breast cancer cells. Importantly, we have identified novel PIP-binding partners in breast cancer and shown that PIP binds to β-tubulin and is necessary for microtubule polymerization. Furthermore, PIP interacts with actin-binding proteins including Arp2/3 and is needed for inside-out activation of integrin-β1 mediated through talin. This study suggests that PIP is required for cell cycle progression in breast cancer and provides a rationale for exploring PIP inhibition as a therapeutic approach in breast cancer that can potentially target microtubule polymerization. PMID:24862759

Plasma-induced polymerization for enhancing paper hydrophobicity.

PubMed

Song, Zhaoping; Tang, Jiebin; Li, Junrong; Xiao, Huining

2013-01-30

Hydrophobic modification of cellulose fibers was conducted via plasma-induced polymerization in an attempt to graft the hydrophobic polymer chains on paper surface, this increasing the hydrophobicity of paper. Two hydrophobic monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA), were grafted on cellulose fibers, induced by atmospheric cold plasma. Various influencing factors associated with the plasma-induced grafting were investigated. Contact-angle measurement, Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to ascertain the occurrence of the grafting and characterized the changes of the cellulose fiber after modification. The results showed that the hydrophobicity of the modified paper sheet was improved significantly after the plasma-induced grafting. The water contact angle on the paper surface reached up to 130°. The morphological differences between modified and unmodified samples were also revealed by SEM observation. The resulting paper is promising as a green-based packaging material. Copyright © 2012 Elsevier Ltd. All rights reserved.

In situ reactive compatibilization of polypropylene/ethylene-propylene-diene monomer thermoplastic vulcanizate by zinc dimethacrylate via peroxide-induced dynamic vulcanization.

PubMed

Chen, Yukun; Xu, Chuanhui; Liang, Xingquan; Cao, Liming

2013-09-12

This work demonstrates an approach of in situ reactive compatibilization between polypropylene (PP) and ethylene-propylene-diene monomer (EPDM) by using zinc dimethacrylate (ZDMA) as a compatibilizer and, simultaneously, as a very strong reinforcing agent. With the incorporation of 7phr ZDMA in the PP/EPDM (30/70, w/w) thermoplastic vulcanizate (TPV), the tensile strength, tear strength, elongation at break, and hardness of PP/EPDM/ZDMA TPV were increased from 5.3 MPa, 31.3 kN/m, 222%, and 78 up to 11.2 MPa, 64.2 kN/m, 396%, and 83, respectively. This tremendous reinforcing as well as the compatibilization effect of the ZDMA was understood by polymerization of ZDMA and ZDMA reacted with EPDM and PP during peroxide-induced dynamic vulcanization. A peculiar phase structure that rubber particles were surrounded and "bonded" by a thick transition zone that contained numerous of nanoparticles with dimensions of about 20-30 nm was observed from transmission electron microscopy. Scanning electron microscopy results confirmed that incorporation of ZDMA reduced the size of the cross-linked EPDM particles. Moreover, we found that the compatibilized TPV showed a higher tan δ peak temperature for EPDM phase and a lower tan δ peak temperature for PP phase. The suggested method for in situ reactive compatibilization of PP and EPDM offers routes to the design of new TPV-based technical products for diversified applications.

An Interferometric Study of Epoxy Polymerization Kinetics

NASA Astrophysics Data System (ADS)

Page, Melissa A.; Tandy Grubbs, W.

1999-05-01

An interferometric method for monitoring polymerization kinetics is described. The experimental apparatus can be constructed from items commonly available in undergraduate laboratories. It consists of a low power helium-neon laser, a home-built Michelson interferometer, and a photodiode light detector. When a polymerizing sample is placed in one arm of the Michelson interferometer, the variation in refractive index will cause a corresponding shift in the phase of the coherent optical beam that passes through the sample, and the output of the interferometer will subsequently fluctuate between constructive and destructive interference. The oscillation in the interferometer output intensity is monitored as a function of time with the photodiode. The time between successive maxima (or minima) is used to calculate the change in refractive index with time (Dn/Dt), which is subsequently used as a phenomenological definition of polymerization rate. We have utilized this device to collect and compare curing profiles of commercially available epoxy glues.

Rapid Engineering of Three-Dimensional, Multicellular Tissues With Polymeric Scaffolds

NASA Technical Reports Server (NTRS)

Gonda, Steve R.; Jordan, Jacqueline; Fraga, Denise N.

2007-01-01

A process has been developed for the rapid tissue engineering of multicellular-tissue-equivalent assemblies by the controlled enzymatic degradation of polymeric beads in a low-fluid-shear bioreactor. In this process, the porous polymeric beads serve as temporary scaffolds to support the assemblies of cells in a tissuelike 3D configuration during the critical initial growth phases of attachment of anchorage-dependent cells, aggregation of the cells, and formation of a 3D extracellular matrix. Once the cells are assembled into a 3D array and enmeshed in a structural supportive 3D extracellular matrix (ECM), the polymeric scaffolds can be degraded in the low-fluid-shear environment of the NASA-designed bioreactor. The natural 3D tissuelike assembly, devoid of any artificial support structure, is maintained in the low-shear bioreactor environment by the newly formed natural cellular/ECM. The elimination of the artificial scaffold allows normal tissue structure and function.

RAFT Aqueous Dispersion Polymerization Yields Poly(ethylene glycol)-Based Diblock Copolymer Nano-Objects with Predictable Single Phase Morphologies

PubMed Central

2013-01-01

A poly(ethylene glycol) (PEG) macromolecular chain transfer agent (macro-CTA) is prepared in high yield (>95%) with 97% dithiobenzoate chain-end functionality in a three-step synthesis starting from a monohydroxy PEG113 precursor. This PEG113-dithiobenzoate is then used for the reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). Polymerizations conducted under optimized conditions at 50 °C led to high conversions as judged by 1H NMR spectroscopy and relatively low diblock copolymer polydispersities (Mw/Mn < 1.25) as judged by GPC. The latter technique also indicated good blocking efficiencies, since there was minimal PEG113 macro-CTA contamination. Systematic variation of the mean degree of polymerization of the core-forming PHPMA block allowed PEG113-PHPMAx diblock copolymer spheres, worms, or vesicles to be prepared at up to 17.5% w/w solids, as judged by dynamic light scattering and transmission electron microscopy studies. Small-angle X-ray scattering (SAXS) analysis revealed that more exotic oligolamellar vesicles were observed at 20% w/w solids when targeting highly asymmetric diblock compositions. Detailed analysis of SAXS curves indicated that the mean number of membranes per oligolamellar vesicle is approximately three. A PEG113-PHPMAx phase diagram was constructed to enable the reproducible targeting of pure phases, as opposed to mixed morphologies (e.g., spheres plus worms or worms plus vesicles). This new RAFT PISA formulation is expected to be important for the rational and efficient synthesis of a wide range of biocompatible, thermo-responsive PEGylated diblock copolymer nano-objects for various biomedical applications. PMID:24400622

Discovering Volatile Chemicals from Window Weatherstripping through Solid-Phase Microextraction/Gas Chromatography-Mass Spectrometry

ERIC Educational Resources Information Center

Rosu, Cornelia; Cueto, Rafael; Veillion, Lucas; David, Connie; Laine, Roger A.; Russo, Paul S.

2017-01-01

Volatile compounds from polymeric materials such as weatherstripping were identified by solid-phase microextraction (SPME), a solvent-free analytical method, coupled to gas chromatography-mass spectrometry (GC-MS). These compounds, originating from additives and fillers used in weatherstripping processing, were mostly polycyclic aromatic…

Toward Ultrasonic Tunable Ultra-Damping Metamaterials

DTIC Science & Technology

2014-03-06

difference is ascribed to the reported presence of a nonmagnetic dead layer around ferrite MNPs and to the silicon-rich shell that is visible on TEM images...spheres deformation. Then, the polymerization of the continuous phase somehow “ freezes ” the structure and the removal of the dispersed phase creates

A Discovery-Oriented Approach to Solid-Phase Peptide Synthesis

ERIC Educational Resources Information Center

Bockman, Matthew R.; Miedema, Christopher J.; Brennan, Brian B.

2012-01-01

In this discovery-oriented laboratory experiment, students use solid-phase synthesis techniques to construct a dipeptide containing an unknown amino acid. Following synthesis and cleavage from the polymeric support, electrospray ionization-mass spectrometry is employed to identify the unknown amino acid that was used in the peptide coupling. This…

Phase Transition of Poly(acrylic acid-co-N-isopropylacrylamide) Core-shell Nanogels

NASA Astrophysics Data System (ADS)

Liu, Xiao-bing; Zhou, Jian-feng; Ye, Xiao-dong

2012-08-01

A series of poly(acrylic acid) macromolecular chain transfer agents with different molecular weights were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and characterized by 1H NMR and gel permeation chromatography. Multiresponsive core-shell nanogels were prepared by dispersion polymerization of N-isopropylacrylamide in water using these poly(potassium acrylate) macro-RAFT agents as the electrosteric stabilizer. The size of the nanogels decreases with the amount of the macro-RAFT agent, indicating that the surface area occupied by per polyelectrolyte group is a critical parameter for stabilizing the nanogels. The volume phase transition and the zeta potentials of the nanogels in aqueous solutions were studied by dynamic light scattering and zetasizer analyzer, respectively.

Structures and properties of poly(3-alkylthiophene) thin-films fabricated though vapor-phase polymerization.

PubMed

Back, Ji-Woong; Song, Eun-Ah; Lee, Keum-Joo; Lee, Youn-Kyung; Hwang, Chae-Ryong; Jo, Sang-Hyun; Jung, Woo-Gwang; Kim, Jin-Yeol

2012-02-01

Organic semiconducting polymer thin-films of 3-hexylthiophene, 3-octylthiophene, 3-decylthiophene, containing highly oriented crystal were fabricated by gas-phase polymerization using the CVD technique. These poly(3-alkylthiophene) films had a crystallinity up to 80%, and possessed a Hall mobility up to 10 cm2/Vs. The degree of crystalinity and the mobility values increased as the alkyl chain length increased. The crystal structure of the polymers was composed of stacked layers constructed by a side-by-side arrangement of alkyl chains and in-plane pi-pi stacking. These thin films are capable of being applied to organic electronics as the active materials used in thin-film transistors and organic photovoltaic cells.

Amphiphilic phase-transforming catalysts for transesterification of triglycerides

NASA Astrophysics Data System (ADS)

Nawaratna, Gayan Ivantha

Heterogeneous catalytic reactions that involve immiscible liquid-phase reactants are challenging to conduct due to limitations associated with mass transport. Nevertheless, there are numerous reactions such as esterification, transesterification, etherification, and hydrolysis where two immiscible liquid reactants (such as polar and non-polar liquids) need to be brought into contact with a catalyst. With the intention of alleviating mass transport issues associated with such systems but affording the ability to separate the catalyst once the reaction is complete, the overall goal of this study is geared toward developing a catalyst that has emulsification properties as well as the ability to phase-transfer (from liquid-phase to solid-phase) while the reaction is ongoing and evaluating the effectiveness of such a catalytic process in a practical reaction. To elucidate this concept, the transesterification reaction was selected. Metal-alkoxides that possess acidic and basic properties (to catalyze the reaction), amphiphilic properties (to stabilize the alcohol/oil emulsion) and that can undergo condensation polymerization when heated (to separate as a solid subsequent to the completion of the reaction) were used to test the concept. Studies included elucidating the effect of metal sites and alkoxide sites and their concentration effects on transesterification reaction, effect of various metal alkoxide groups on the phase stability of the reactant system, and kinetic effects of the reaction system. The studies revealed that several transition-metal alkoxides, especially, titanium and yttrium based, responded positively to this reaction system. These alkoxides were able to be added to the reaction medium in liquid phase and were able to stabilize the alcohol/oil system. The alkoxides were selective to the transesterification reaction giving a range of ester yields (depending on the catalyst used). It was also observed that transition-metal alkoxides were able to be recovered in the form of their polymerized counterparts as a result of condensation polymerization subsequent to completion of the transesterification reaction.

Polymeric ionic liquid bucky gels as sorbent coatings for solid-phase microextraction.

PubMed

Zhang, Cheng; Anderson, Jared L

2014-05-30

Novel cross-linked polymeric ionic liquid (PIL) bucky gels were formed by free-radical polymerization of polymerizable ionic liquids gelled with multi-walled carbon nanotubes (MWCNT) and used as sorbent coatings for solid-phase microextraction (SPME). The combination of PIL with MWCNTs significantly enhanced the π-π interaction between the sorbent coatings and the aromatic analytes. Compared to the neat PIL-based sorbent coating, the PIL bucky gel sorbent coatings demonstrated higher extraction efficiency for the extraction of polycyclic aromatic hydrocarbons (PAHs). A partitioning extraction mechanism was observed for the PIL/MWCNT-based sorbent coatings indicating that the addition of MWCNTs did not seem to affect the extraction mechanism of the sorbent coating. The analyte-to-coating partition coefficients (logKfs) were estimated and the limits of detection (LOD) for selected PIL bucky gel sorbent coating were determined to be in the range of 1-2.5 ng L(-1). Recovery studies were also performed for PAHs in river and tap water to validate the applicability of the developed method. Copyright © 2014 Elsevier B.V. All rights reserved.

Development and validation of an HPLC method to quantify camptothecin in polymeric nanocapsule suspensions.

PubMed

Granada, Andréa; Murakami, Fabio S; Sartori, Tatiane; Lemos-Senna, Elenara; Silva, Marcos A S

2008-01-01

A simple, rapid, and sensitive reversed-phase column high-performance liquid chromatographic method was developed and validated to quantify camptothecin (CPT) in polymeric nanocapsule suspensions. The chromatographic separation was performed on a Supelcosil LC-18 column (15 cm x 4.6 mm id, 5 microm) using a mobile phase consisting of methanol-10 mM KH2PO4 (60 + 40, v/v; pH 2.8) at a flow rate of 1.0 mL/min and ultraviolet detection at 254 nm. The calibration graph was linear from 0.5 to 3.0 microg/mL with a correlation coefficient of 0.9979, and the limit of quantitation was 0.35 microg/mL. The assay recovery ranged from 97.3 to 105.0%. The intraday and interday relative standard deviation values were < 5.0%. The validation results confirmed that the developed method is specific, linear, accurate, and precise for its intended use. The current method was successfully applied to the evaluation of CPT entrapment efficiency and drug content in polymeric nanocapsule suspensions during the early stage of formulation development.

Photoinitiated Polymerization‐Induced Self‐Assembly (Photo‐PISA): New Insights and Opportunities

PubMed Central

Yeow, Jonathan

2017-01-01

The polymerization‐induced self‐assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo‐PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo‐PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo‐PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self‐assembly process. The purpose of this mini‐review is therefore to examine some of these recent advances that have been made in Photo‐PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems. PMID:28725534

A novel synthesis of polymeric CO via useful hard X-ray photochemistry

NASA Astrophysics Data System (ADS)

Pravica, Michael; Sneed, Daniel; Smith, Quinlan; Billinghurst, Brant; May, Tim; White, Melanie; Dziubek, Kamil

2016-12-01

We report on the synchrotron hard X-ray-induced decomposition of strontium oxalate (SrC2O4) pressurized to 7 GPa inside a diamond anvil cell (DAC). After some 4 h of irradiation in a white X-ray synchrotron beam, a dark reddish/brown region formed in the area of irradiation which was surrounded by a yellowish brown remainder in the rest of the sample. Upon depressurization of the sample to ambient conditions, the reacted/decomposed sample was recoverable as a dark brown/red and yellow waxy solid. Synchrotron infrared spectroscopy confirmed the strong presence of CO2 even under ambient conditions with the sample exposed to air and other strongly absorbing regions, suggesting that the sample may likely be polymerized CO (in part) with dispersed CO2 and SrO trapped within the polymer. These results will have significant implications in the ability to readily produce and trap CO2 in situ via irradiation of a simple powder for useful hard X-ray photochemistry and in the ability to easily manufacture polymeric CO (via loading of powders in a DAC or high volume press) without the need for the dangerous and complex loading of toxic CO. A novel means of X-ray-induced polymerization under extreme conditions has also been demonstrated.

Facile fabrication of mesoporous poly(ethylene-co-vinyl alcohol)/chitosan blend monoliths.

PubMed

Wang, Guowei; Xin, Yuanrong; Uyama, Hiroshi

2015-11-05

Poly(ethylene-co-vinyl alcohol) (EVOH)/chitosan blend monoliths were fabricated by thermally-induced phase separation method. Chitosan was successfully incorporated into the polymeric monolith by selecting EVOH as the main component of the monolith. SEM images exhibit that the chitosan was located on the inner surface of the monolith. Fourier-transform infrared analysis and elemental analysis indicate the successful blend of EVOH and chitosan. BET results show that the blend monoliths had high specific surface area and uniform mesopore structure. Good adsorption ability toward various heavy metal ions was found in the blend monoliths due to the large chelation capacity of chitosan. The blend monoliths have potential application for waste water purification or bio-related applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Method for dialysis on microchips using thin porous polymer membrane

DOEpatents

Singh, Anup K [San Francisco, CA; Kirby, Brian J [San Francisco, CA; Shepodd, Timothy J [Livermore, CA

2009-05-19

Laser-induced phase-separation polymerization of a porous acrylate polymer is used for in-situ fabrication of dialysis membranes inside glass microchannels. A shaped 355 nm laser beam is used to produce a porous polymer membrane with a thickness of about 15 .mu.m, which bonds to the glass microchannel and forms a semi-permeable membrane. Differential permeation through a membrane formed with pentaerythritol triacrylate was observed and quantified by comparing the response of the membrane to fluorescein and fluorescently tagging 200 nm latex microspheres. Differential permeation was observed and quantified by comparing the response to rhodamine 560 and lactalbumin protein in a membrane formed with SPE-methylene bisacrylamide. The porous membranes illustrate the capability for the present technique to integrate sample cleanup into chip-based analysis systems.

Dialysis on microchips using thin porous polymer membranes

DOEpatents

Singh, Anup K.; Kirby, Brian J.; Shepodd, Timothy J.

2007-09-04

Laser-induced phase-separation polymerization of a porous acrylate polymer is used for in-situ fabrication of dialysis membranes inside glass microchannels. A shaped 355 nm laser beam is used to produce a porous polymer membrane with a thickness of about 15 .mu.m, which bonds to the glass microchannel and form a semi-permeable membrane. Differential permeation through a membrane formed with pentaerythritol triacrylate was observed and quantified by comparing the response of the membrane to fluorescein and fluorescently tagging 200 nm latex microspheres. Differential permeation was observed and quantified by comparing the response to rhodamine 560 and lactalbumin protein in a membrane formed with SPE-methylene bisacrylamide. The porous membranes illustrate the capability for the present technique to integrate sample cleanup into chip-based analysis systems.

Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

NASA Astrophysics Data System (ADS)

Zonca, Michael R., Jr.

Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a new avenue for stem cell culture and maintenance using an optimal organic-based chemistry.

Determination of the molecular weight of poly(ethylene glycol) in biological samples by reversed-phase LC-MS with in-source fragmentation.

PubMed

Warrack, Bethanne M; Redding, Brian P; Chen, Guodong; Bolgar, Mark S

2013-05-01

PEGylation has been widely used to improve the biopharmaceutical properties of therapeutic proteins and peptides. Previous studies have used multiple analytical techniques to determine the fate of both the therapeutic molecule and unconjugated poly(ethylene glycol) (PEG) after drug administration. A straightforward strategy utilizing liquid chromatography-mass spectrometry (LC-MS) to characterize high-molecular weight PEG in biologic matrices without a need for complex sample preparation is presented. The method is capable of determining whether high-MW PEG is cleaved in vivo to lower-molecular weight PEG species. Reversed-phase chromatographic separation is used to take advantage of the retention principles of polymeric materials whereby elution order correlates with PEG molecular weight. In-source collision-induced dissociation (CID) combined with selected reaction monitoring (SRM) or selected ion monitoring (SIM) mass spectrometry (MS) is then used to monitor characteristic PEG fragment ions in biological samples. MS provides high sensitivity and specificity for PEG and the observed retention times in reversed-phase LC enable estimation of molecular weight. This method was successfully used to characterize PEG molecular weight in mouse serum samples. No change in molecular weight was observed for 48 h after dosing.

Effects of nitric oxide and its congeners on sickle red blood cell deformability

PubMed Central

Belanger, Andrea M.; Keggi, Christian; Kanias, Tamir; Gladwin, Mark T.; Kim-Shapiro, Daniel B.

2015-01-01

BACKGROUND Sickle cell disease is characterized by hemoglobin (Hb) polymerization upon deoxygenation. Polymerization causes the sickle cells to become rigid and misshapen (sickling). Red blood cell (RBC) dehydration greatly increases polymerization. Cycles of sickling and unsickling cause an influx of calcium that leads to loss of potassium via the calcium-activated Gardos channel which dehydrates the cells leading to increased polymerization. In this study effects of NO and its congeners on RBC deformability were examined, focusing on sickle red blood cells. STUDY DESIGN AND METHODS Red blood cells from patients with sickle cell disease and from non-patients were exposed to various compounds that release NO or its congeners. Intracellular calcium was increased using a calcium ionophore or cycling of oxygen tension for sickle red blood cells. Deformability was measured by laser-assisted osmotic gradient ektacytometry. RESULTS Consistent with a previous report, sodium nitroprusside (SNP) was found to protect against calcium-induced loss of deformability in normal red blood cells, but (contrary to some previous reports) no effect of any NO donors was observed when calcium influx was not induced. Importantly, in studies of deoxygenation-induced dehydration of sickle RBCs, SNP resulted in substantial improvements in deformability (p=0.036) and hydration (p=0.024). Sodium nitrite showed similar trends. SNP was shown to have no effect on calcium influx, but reduced potassium efflux. CONCLUSION These data suggest SNP and perhaps certain nitrogen oxides (like nitrite) inhibit the Gardos channel and may be able to protect sickle cells from dehydration and thereby improve outcome in the disease. PMID:25912054

Hydrophobic Coatings on Cotton Obtained by in Situ Plasma Polymerization of a Fluorinated Monomer in Ethanol Solutions.

PubMed

Molina, Ricardo; Teixidó, Josep Maria; Kan, Chi-Wai; Jovančić, Petar

2017-02-15

Plasma polymerization using hydrophobic monomers in the gas phase is a well-known technology to generate hydrophobic coatings. However, synthesis of functional hydrophobic coatings using plasma technology in liquids has not yet been accomplished. This work is consequently focused on polymerization of a liquid fluorinated monomer on cotton fabric initiated by atmospheric plasma in a dielectric barrier discharge configuration. Functional hydrophobic coatings on cotton were successfully achieved using in situ atmospheric plasma-initiated polymerization of fluorinated monomer dissolved in ethanol. Gravimetric measurements reveal that the amount of polymer deposited on cotton substrates can be modulated with the concentration of monomer in ethanol solution, and cross-linking reactions occur during plasma polymerization of a fluorinated monomer even without the presence of a cross-linking agent. FTIR and XPS analysis were used to study the chemical composition of hydrophobic coatings and to get insights into the physicochemical processes involved in plasma treatment. SEM analysis reveals that at high monomer concentration, coatings possess a three-dimensional pattern with a characteristic interconnected porous network structure. EDX analysis reveals that plasma polymerization of fluorinated monomers takes place preferentially at the surface of cotton fabric and negligible polymerization takes place inside the cotton fabric. Wetting time measurements confirm the hydrophobicity of cotton coatings obtained although equilibrium moisture content was slightly decreased. Additionally, the abrasion behavior and resistance to washing of plasma-coated cotton has been evaluated.

DNA polymeric films as a support for cell growth as a new material for regenerative medicine: Compatibility and applicability.

PubMed

Jayme, Cristiano Ceron; de Paula, Leonardo Barcelos; Rezende, Nayara; Calori, Italo Rodrigo; Franchi, Leonardo Pereira; Tedesco, Antonio Claudio

2017-11-15

DNA polymeric films (DNA-PFs) are a promising drug delivery system (DDS) in modern medicine. In this study, we evaluated the growth behavior of oral squamous cell carcinoma (OSCC) cells on DNA-PFs. The morphological, biochemical, and cytometric features of OSCC cell adhesion on DNA-PFs were also assessed. An initial, temporary alteration in cell morphology was observed at early time points owing to the inhibition of cell attachment to the film, which then returned to a normal morphological state at later time points. MTT and resazurin assays showed a moderate reduction in cell viability related to increased DNA concentration in the DNA-PFs. Flow cytometry studies showed low cytotoxicity of DNA-PFs, with cell viabilities higher than 90% in all the DNA-PFs tested. Flow cytometric cell cycle analysis also showed average cell cycle phase distributions at later time points, indicating that OSCC cell growth is maintained in the presence of DNA-PFs. These results show high biocompatibility of DNA-PFs and suggest their use in designing "dressing material," where the DNA film acts as a support for cell growth, or with incorporation of active or photoactive compounds, which can induce tissue regeneration and are useful to treat many diseases, especially oral cancer. Copyright © 2017 Elsevier Inc. All rights reserved.

Polymeric membranes modulate human keratinocyte differentiation in specific epidermal layers.

PubMed

Salerno, Simona; Morelli, Sabrina; Giordano, Francesca; Gordano, Amalia; Bartolo, Loredana De

2016-10-01

In vitro models of human bioengineered skin substitutes are an alternative to animal experimentation for testing the effects and toxicity of drugs, cosmetics and pollutants. For the first time specific and distinct human epidermal strata were engineered by using membranes and keratinocytes. To this purpose, biodegradable membranes of chitosan (CHT), polycaprolactone (PCL) and a polymeric blend of CHT-PCL were prepared by phase-inversion technique and characterized in order to evaluate their morphological, physico-chemical and mechanical properties. The capability of membranes to modulate keratinocyte differentiation inducing specific interactions in epidermal membrane systems was investigated. The overall results demonstrated that the membrane properties strongly influence the cell morpho-functional behaviour of human keratinocytes, modulating their terminal differentiation, with the creation of specific epidermal strata or a fully proliferative epidermal multilayer system. In particular, human keratinocytes adhered on CHT and CHT-PCL membranes, forming the structure of the epidermal top layers, such as the corneum and granulosum strata, characterized by withdrawal or reduction from the cell cycle and cell proliferation. On the PCL membrane, keratinocytes developed an epidermal basal lamina, with high proliferating cells that stratified and migrated over time to form a complete differentiating epidermal multilayer system. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of sodium chloride and sodium bicarbonate on the physicochemical properties of soft wheat flour doughs and gluten polymerization.

PubMed

Chen, Gengjun; Ehmke, Laura; Miller, Rebecca; Faa, Pierre; Smith, Gordon; Li, Yonghui

2018-06-07

Soft wheat flour doughs were prepared with different levels of salt (NaCl) and/or baking soda (NaHCO3). Oscillation rheology, elongational viscosity, and extensibility of doughs were tested to evaluate the effect of salt and/or baking soda on the physical properties of doughs. Furthermore, a series of physical-biochemical analytical techniques were used to investigate gluten polymerization in doughs, including Zeta potential analyzer, Fourier transform infrared spectroscopy (FTIR), spectrophotometer, and reversed phase high performance liquid chromatography (RP-HPLC). Addition of high levels of NaHCO3 (1.0 % fwb), either by itself or in combination with NaCl, increased dough strength, elongational viscosity, and viscoelasticity. RP-HPLC results demonstrated macromolecular aggregation of gluten proteins in the presence of NaCl and/or NaHCO3. Addition of NaHCO3 or NaCl also decreased both free sulfhydryl content and random coil structure of gluten isolated from the doughs. Overall, NaCl and/or NaHCO3 induced the changes of molecular conformation of gluten, which impacted the physicochemical qualities of soft wheat flour dough. Our study provides a better understanding of salt and baking soda functionality in the formation of soft flour dough, which will support the searching of feasible sodium reduction strategies in soft flour bakery products.

Polysulfone hemodiafiltration membranes with enhanced anti-fouling and hemocompatibility modified by poly(vinyl pyrrolidone) via in situ cross-linked polymerization.

PubMed

Zhu, Lijing; Song, Haiming; Wang, Jiarong; Xue, Lixin

2017-05-01

Poly(vinyl pyrrolidone) (PVP) and its copolymers have been widely employed for the modification of hemodiafiltration membranes due to their excellent hydrophilicity, antifouling and hemocompatibility. However, challenges still remain to simplify the modification procedure and to improve the utilization efficiency. In this paper, antifouling and hemocompatibility polysulfone (PSf) hemodiafiltration membranes were fabricated via in situ cross-linked polymerization of vinyl pyrrolidone (VP) and vinyltriethoxysilane (VTEOS) in PSf solutions and non-solvent induced phase separation (NIPS) technique. The prepared membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), which suggested that VP and VTEOS have been cross-linked copolymerized in PSf membranes. The modified PSf membranes with high polymer content showed improved hydrophilicity, ultrafiltration and protein antifouling ability. In addition, the modified PSf membranes showed lower protein adsorption, inhibited platelet adhesion and deformation, prolonged the activated partial thromboplastin time (APTT), prothrombin time (PT), and decreased the content of fibrinogen (FIB) transferring to fibrin, indicating enhanced hemocompatibility. In a word, the present work provides a simple and effective one-step modification method to construct PSf membranes with improved hydrophilicity, antifouling and hemocompatibility. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecularly imprinted polymer/cryogel composites for solid-phase extraction of bisphenol A from river water and wine.

PubMed

Baggiani, Claudio; Baravalle, Patrizia; Giovannoli, Cristina; Anfossi, Laura; Giraudi, Gianfranco

2010-05-01

Superporous monolithic hydrogels (cryogel monoliths) are elastic, sponge-like materials that can be prepared in an aqueous medium through a cryotropic gelation technique. These monoliths show interesting properties for the development of high-throughput solid-phase extraction supports to treat large volumes of aqueous samples. In this work, a cryogel-supported molecularly imprinted solid-phase extraction approach for the endocrine disruptor bisphenol A (BPA) from river water and wine samples is presented. An imprinted polymer with molecular recognition properties for BPA was prepared in acetonitrile by thermal polymerization of a mixture of 4,4'-dihydroxy-2,2-diphenyl-1,1,1,3,3,3-trifluoropropane as a mimic template of BPA, 4-vinylpyridine and trimethylolpropane trimethacrylate in a molar ratio of 1 + 6 + 6. Fine imprinted particles (<10 microm) were embedded in a poly-acrylamide-co-N,N'-methylenbisacrylamide cryogel obtained by ammonium persulfate-induced cryopolymerization at -18 degrees C. The resulting monolithic gel was evaluated for its use as a sorbent support in an off-line solid-phase extraction approach to recover BPA from dilute aqueous samples with minimum pre-loading work-up. The optimized extraction protocol resulted in a reliable MISPE method suitable to selectively extract and preconcentrate BPA from river water and red wine samples, demonstrating the practical feasibility of cryogel-trapped imprinted polymers as solid-phase extraction materials.

Gas-phase and solution-phase polymerization of epoxides by Cr(salen) complexes: evidence for a dinuclear cationic mechanism.

PubMed

Schön, Eva; Zhang, Xiangyang; Zhou, Zhiping; Chisholm, Malcolm H; Chen, Peter

2004-11-15

The gas-phase reactions of a series of mass-selected mononuclear and dinuclear Cr(salen) complexes with propylene oxide suggest that the enhanced reactivity of the dinuclear complexes in gas-phase and in solution may derive from a dicationic mechanism in which the alkoxide chain is mu(2)-coordinated to two Lewis acidic metal centers. The double coordination is proposed to suppress backbiting, and hence chain-transfer in the gas-phase homopolymerization of epoxides.

DH and ESPI laser interferometry applied to the restoration shrinkage assessment

NASA Astrophysics Data System (ADS)

Campos, L. M. P.; Parra, D. F.; Vasconcelos, M. R.; Vaz, M.; Monteiro, J.

2014-01-01

In dental restoration postoperative marginal leakage is commonly associated to polymerization shrinkage effects. In consequence the longevity and quality of restorative treatment depends on the shrinkage mechanisms of the composite filling during the polymerization. In this work the development of new techniques for evaluation of those effects under light-induced polymerization of dental nano composite fillings is reported. The composite resins activated by visible light, initiate the polymerization process by absorbing light in wavelengths at about 470 nm. The techniques employed in the contraction assessment were digital holography (DH) and Electronic Speckle Pattern Interferometry (ESPI) based on laser interferometry. A satisfactory resolution was achieved in the non-contact displacement field measurements on small objects concerning the experimental dental samples. According to a specific clinical protocol, natural teeth were used (human mandibular premolars). A class I cavity was drilled and restored with nano composite material, according to Black principles. The polymerization was monitored by DH and ESPI in real time during the cure reaction of the restoration. The total displacement reported for the material in relation of the tooth wall was 3.7 μm (natural tooth). The technique showed the entire tooth surface (wall) deforming during polymerization shrinkage.

Impact of the lateral boundary conditions resolution on dynamical downscaling of precipitation in mediterranean spain

NASA Astrophysics Data System (ADS)

Amengual, A.; Romero, R.; Homar, V.; Ramis, C.; Alonso, S.

2007-08-01

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle image velocimetry (PIV). Quantitative comparisons of velocity profiles across the shock waves in air and in PDMS demonstrate the improved response achieved by the dynamic witness plate method. Schlieren photographs complement the analysis through direct visualization of detonator-induced shock waves in the witness plates.

Particle response to shock waves in solids: dynamic witness plate/PIV method for detonations

NASA Astrophysics Data System (ADS)

Murphy, Michael J.; Adrian, Ronald J.

2007-08-01

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle image velocimetry (PIV). Quantitative comparisons of velocity profiles across the shock waves in air and in PDMS demonstrate the improved response achieved by the dynamic witness plate method. Schlieren photographs complement the analysis through direct visualization of detonator-induced shock waves in the witness plates.

Study of fracture and stress-induced morphological instabilities in polymeric materials

NASA Astrophysics Data System (ADS)

Sabouri-Ghomi, Mohsen

We study the phenomena of fracture in polymers at the molecular and continuum level. At a molecular level, we study the failure of polymer/polymer interfaces. Our main focus is on a specific mode of failure known as chain pull-out fracture, which is common to weak adhesive junctions, and polymer blends and mixtures. In the case of the interface between incompatible polymers, reinforcement is achieved by adding a block copolymer to the interface. We introduce a microscopic model based on Brownian dynamics to investigate the effect of the polymerization index N, of the block connector chain, on fracture toughness of such reinforced polymeric junctions. We consider the mushroom regime, where connector chains are grafted with low surface density, for the case of large pulling velocity. We find that for short chains the interface fracture toughness depends linearly on the polymerization index N of the connector chains, while for longer chains the dependence becomes N 3/2. We propose a scaling argument, based on the geometry of the initial configuration, that accounts for both short and long chains and the crossover between them. At the continuum level, we study the pattern selection mechanism of finger-like crack growth phenomena in gradient driven growth problems in general, and the structure of stress-induced morphological instabilities in crazing of polymer glasses in particular. We simulate solidification in a narrow channel through the use of a phase-field model with an adaptive grid. By tuning a dimensionless parameter, the Peclet number, we show a continuous crossover from a free dendrite at high Peclet numbers to anisotropic viscous fingering at low Peclet numbers. At low Peclet numbers we find good agreement between our results, theoretical predictions, and experiment, providing the first quantitative test of solvability theory for anisotropic viscous fingers. For high undercoolings, we find new phenomena, a solid forger which satisfies stability and thermodynamic criterion. We further provide an analytical form for the shape of these fingers, based on local models of solidification, which fits our numerical results from simulation. Later we study the growth of crazes in polymer glasses by deriving the equations of motion of plastic flow at the craze tip, and the steady-state velocity profile of this flow. By developing a phenomenological model, we solve the full time-dependent equations of motion of this highly non-linear phenomena. Our simulation produces the steady-state cellular pattern observed in experiments. We further show that polymer glasses with lower yield stress produce cellular patterns with sharper tips and more cells, indicating instabilities with smaller wavelengths.

Slippery interfaces: lubrication of director and helix rotation motions (Conference Presentation)

NASA Astrophysics Data System (ADS)

Yamamoto, Jun; Sakatsuji, Waki; Nishiyama, Isa

2017-02-01

Anchoring effects on the polymer films in the liquid crystal (LC) display devices plays key role to create the restoring force to the black state. However, the chiral materials with spontaneous helix, such as deformed helix mode in SmC* (DH-FLC) or the polymer stabilized blue phase (PSChBP), can recover black state by rewinding motion of the helix itself. We have invented the principle and design of slippery interfaces, which has zero anchoring force for attached LC molecules on the interfaces, and confirmed the drastic reduction of driving voltage in DH-FLC mode of SmC* (<1 order) keeping the fast switching response (tau 50 micro sec). We have reported the lateral slippery interfaces consist of the phase separated liquid phases created by tran-cis isomerization of doped azo dye. It is not enough to the complete transmission of the light(I/I0 1) by applying the typical driving voltage ( 1.0V/micro m) for current IPS panels. It is also problem that slippery interface become effective only just below the I-SmC phase transition temperature (TIC-T<20°). Here, we report new type of the vertical slippery interface realized by the spin coated swollen azo-LC gel films on the glass substrates. Under UV irradiation, trans-cis isomerization of the azo-dye co-polymerized in the azo-LC gel film, induces the vertical slippery interfaces by the disordering effect. Since the co-polymerized azo-dye cannot be dissolved into LC, the disordering effect is completely localized in the interface between swollen azo-LC gel and bulk SmC* material. Then the slippery interfaces can be stabilized over wide temperature range. We greatly improve the reduction of the driving voltage, I/Io=1, 1.0V/micro m for rather slow change of the driving voltage (tau 1msec 2.5msec pulse), I/I0=0.6, 1.5V/micro m for fast change (tau 50 micro sec, 250 micro sec pulse) by lubrication of intra and inter helix C-director rotation motions.

Role of strongly interacting additives in tuning the structure and properties of polymer systems

NASA Astrophysics Data System (ADS)

Daga, Vikram Kumar

Block copolymer (BCP) nanocomposites are an important class of hybrid materials in which the BCP guides the spatial location and the periodic assembly of the additives. High loadings of well-dispersed nanofillers are generally important for many applications including mechanical reinforcing of polymers. In particular the composites shown in this work might find use as etch masks in nanolithography, or for enabling various phase selective reactions for new materials development. This work explores the use of hydrogen bonding interactions between various additives (such as homopolymers and non-polymeric additives) and small, disordered BCPs to cause the formation of well-ordered morphologies with small domains. A detailed study of the organization of homopolymer chains and the evolution of structure during the process of ordering is performed. The results demonstrate that by tuning the selective interaction of the additive with the incorporating phase of the BCP, composites with significantly high loadings of additives can be formed while maintaining order in the BCP morphology. The possibility of high and selective loading of additives in one of the phases of the ordered BCP composite opens new avenues due to high degree of functionalization and the proximity of the additives within the incorporating phase. This aspect is utilized in one case for the formation of a network structure between adjoining additive cores to derive mesoporous inorganic materials with their structures templated by the BCP. The concept of additive-driven assembly is extended to formulate BCPadditive blends with an ability to undergo photo-induced ordering. Underlying this strategy is the ability to transition a weakly interacting additive to its strongly interacting form. This strategy provides an on-demand, non-intrusive route for formation of well-ordered nanostructures in arbitrarily defined regions of an otherwise disordered material. The second area explored in this dissertation deals with the incorporation of additives into photoresists for next generation extreme ultra violet (EUV) photolithography applications. The concept of hydrogen bonding between the additives and the polymeric photoresist was utilized to cause formation of a physical network that is expected to slow down the diffusion of photoacid leading to better photolithographic performance (25-30 nm resolution obtained).

Aronia melanocarpa as a protector against nitration of fibrinogen.

PubMed

Bijak, Michał; Saluk, Joanna; Antosik, Adam; Ponczek, Michał B; Żbikowska, Halina M; Borowiecka, Marta; Nowak, Paweł

2013-04-01

Fibrinogen (Fg) also known as coagulation factor I represents about 4% of the total human plasma proteins. The main function of Fg is its involvement in last phase of blood coagulation cascade, when thrombin-induced conversion of dissolved plasma fibrinogen into an insoluble fibrin clot occurs. The reaction of fibrinogen with peroxynitrite causes both structural modifications and changes of the biological properties of this plasma glycoprotein. Recently, there is an increased interest in the screening of natural products present in fruits, vegetables and herbs for their possible antioxidative activities. Therefore, the aim of our study was to estimate the effect of extract from berries of Aronia melanocarpa against nitrative and oxidative damage induced by peroxynitrite. The extract from A. melanocarpa (0.5-50 μg/ml) added to Fg 10 min before peroxynitrite (100 μM) significantly inhibited both the formation of the high molecular weight protein aggregates and nitration of Fg molecule. The extract also abolished peroxynitrite-induced inhibition of fibrinogen polymerization (by 95% at 50 μg/ml). The obtained results indicate that natural extract from berries of A. melanocarpa has protective effects against peroxynitrite-induced nitrative damage of plasma fibrinogen, and therefore may contribute in the prevention of peroxynitrite-related cardiovascular or inflammatory diseases. Copyright © 2013 Elsevier B.V. All rights reserved.

Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains

NASA Astrophysics Data System (ADS)

Mubeena, Shaikh; Chatterji, Apratim

2015-03-01

We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter σn) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

Characterization of photochemical-cured acrylates with calorimetric methods

NASA Astrophysics Data System (ADS)

Strehmel, Bernd; Anwand, Dirk; Wetzel, Henrik

1994-05-01

Radical polymerization kinetics of different kinds of diacrylates was investigated in linear polymers (binders) by using an isoperibolic calorimeter. For all experiments benzoin compounds were added as photoinitiator. The ester between acrylic acid and bisphenol-A-diglycidylether (DDGDA) and hexamethylenediacrylate were used as monomers. Both compounds have a high limiting conversion and a large polymerization rate in the binders investigated. Additionally, three kinds of termination reaction were observed: first order, second order, and primary radical termination. The last reaction was mainly found in the case of using the hexamethylenediacrylate monomer. The materials were investigated by DSC to determine the phase behavior. Both monomers form one phase with the binder (polymethylmethacrylate, PMMA). In contrast, a phase separation was observed between the crosslinked hexamethylenediacrylate and PMMA. Formations of semi- interpenetrating networks were found in the case of crosslinked DDGDA and PMMA. The glass transition temperatures were determined at different polymerization degrees also. The obtained results indicate that most of the network formation occurred in the glassy state. Fluorescence probe technique was applied to study changes in the mobility during network formation. The fluorescence probe crystal violet (CV) was used because this compound shows a strong free volume-dependent fluorescence. It was found that in the glassy state, where most of networks were formed, a large variation of the molecular mobility was observed during irradiation of the photopolymers. This result was in agreement with the observations during DSC experiments.

Anomalous Debye-like dielectric relaxation of water in micro-sized confined polymeric systems.

PubMed

Colosi, C; Costantini, M; Barbetta, A; Cametti, C; Dentini, M

2013-12-14

While it is well known that spatial confinement on a nm scale affects the molecular dynamics of water resulting in a hindered dipolar reorientation, question of whether these effects could result at length scales larger than these, i.e., in confined regions of the order of μm or more, is still under debate. Here we use dielectric relaxation spectroscopy techniques to study the relaxation orientation dynamics of water entrapped in different polymeric matrices with pore sizes of the order of 100 μm, analyzing the frequency relaxation behaviour of the dielectric response. Our results show that, contrary to what has been generally thought, even in confinements which are not particularly high such as those realized here, regions typically hundred micrometers in size can affect the water structure, inducing a water phase with properties different from those of bulk water. In particular, we observe a dielectric dispersion centered in the range 10(5)-10(7) Hz, in between the one characteristic of ice (8.3 kHz at T = 0 °C) and the one of bulk water (19.2 GHz at T = 25 °C). The analysis of the dependence on temperature of the relaxation time of this unexpected contribution rules out the possibility that it can be attributed to an interfacial polarization (Maxwell-Wagner effect) and suggests a dipolar Debye-like origin due to a slow-down of the hydrogen-bonded network orientational polarization. Also at these scales, the confinement alters the structure of water, leading to a hindered reorientation. These properties imply that water confined within these polymeric porous matrices is more ordered than bulk water. These findings may be important in order to understand biological processes in cells and in different biological compartments, where water is physiologically confined.

Large-scale purification and in vitro characterization of the assembly of MreB from Leptospira interrogans.

PubMed

Barkó, Szilvia; Szatmári, Dávid; Bódis, Emőke; Türmer, Katalin; Ujfalusi, Zoltán; Popp, David; Robinson, Robert C; Nyitrai, Miklós

2016-09-01

Weil's syndrome is caused by Leptospira interrogans infections, a Gram negative bacterium with a distinct thin corkscrew cell shape. The molecular basis for this unusual morphology is unknown. In many bacteria, cell wall synthesis is orchestrated by the actin homolog, MreB. Here we have identified the MreB within the L. interrogans genome and expressed the His-tagged protein product of the synthesized gene (Li-MreB) in Escherichia coli. Li-MreB did not purify under standard nucleotide-free conditions used for MreBs from other species, requiring the continual presence of ATP to remain soluble. Covalent modification of Li-MreB free thiols with Alexa488 produced a fluorescent version of Li-MreB. We developed native and denaturing/refolding purification schemes for Li-MreB. The purified product was shown to assemble and disassemble in MgCl2 and KCl dependent manners, as monitored by light scattering and sedimentation studies. The fluorescence spectrum of labeled Li-MreB-Alexa488 showed cation-induced changes in line with an activation process followed by a polymerization phase. The resulting filaments appeared as bundles and sheets under the fluorescence microscope. Finally, since the Li-MreB polymerization was cation dependent, we developed a simple method to measure monovalent cation concentrations within a test case prokaryote, E. coli. We have identified and initially characterized the cation-dependent polymerization properties of a novel MreB from a non-rod shaped bacterium and developed a method to measure cation concentrations within prokaryotes. This initial characterization of Li-MreB will enable future structural determination of the MreB filament from this corkscrew-shaped bacterium. Copyright © 2016 Elsevier B.V. All rights reserved.

YSL-12, a novel microtubule-destabilizing agent, exerts potent anti-tumor activity against colon cancer in vitro and in vivo.

PubMed

Cai, De; Qiu, Zhiqing; Yao, Weimin; Liu, Yuyu; Huang, Haixiang; Liao, Sihai; Luo, Qun; Xie, Liming; Lin, Zhixiu

2016-06-01

Microtubules play a central role in various fundamental cell functions and thus become an attractive target for cancer therapy. A novel compound YSL-12 is a combretastatin A-4 (CA-4) analogue with more stability. We investigated its anti-tumor activity and mechanisms in vitro and in vivo for the first time. Cytotoxicity was evaluated by MTT method. In vitro microtubule polymerization assay was performed using a fluorescence-based method by multifunction fluorescence microplate reader. Intracellular microtubule network was detected by immunofluorescence method. Cell cycle analysis and apoptosis were measured by flow cytometry. Metabolic stability was recorded by liquid chromatography-ultraviolet detection and liquid chromatography-mass spectrometry. In vivo anti-tumor activity was assessed using HT-29 colon carcinoma xenografts established in BALB/c nude mice. YSL-12 displayed nanomolar-level cytotoxicity against various human cancer cell lines. A high selectivity toward normal cells and potent activity toward drug-resistant cells were also observed. YSL-12 was identified as tubulin polymerization inhibitor evidenced by effectively inhibits tubulin polymerization and heavily disrupted microtubule networks in living HT-29 cells. YSL-12 displayed potent disruption effect of pre-established tumor vasculature in vitro. In addition, YSL-12 treatment also caused cell cycle arrest in the G2/M phase and induced cell apoptosis in a dose-dependent manner. In vitro metabolic stability study revealed YSL-12 displayed considerable better stability than CA-4 in liver microsomes. In vivo, YSL-12 delayed tumor growth with 69.4 % growth inhibition. YSL-12 is a promising microtubule inhibitor that has great potential for the treatment of colon carcinoma in vitro and in vivo and worth being a candidate for further development of cancer therapy.

Polymeric Nanofibers in Tissue Engineering

PubMed Central

Dahlin, Rebecca L.; Kasper, F. Kurtis

2011-01-01

Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed. PMID:21699434

Collapse of surface nanobubbles.

PubMed

Chan, Chon U; Chen, Longquan; Arora, Manish; Ohl, Claus-Dieter

2015-03-20

Surface attached nanobubbles populate surfaces submerged in water. These nanobubbles have a much larger contact angle and longer lifetime than predicted by classical theory. Moreover, it is difficult to distinguish them from hydrophobic droplets, e.g., polymeric contamination, using standard atomic force microscopy. Here, we report fast dynamics of a three phase contact line moving over surface nanobubbles, polymeric droplets, and hydrophobic particles. The dynamics is distinct: across polymeric droplets the contact line quickly jumps and hydrophobic particles pin the contact line, while surface nanobubbles rapidly shrink once merging with the contact line, suggesting a method to differentiate nanoscopic gaseous, liquid, and solid structures. Although the collapse process of surface nanobubbles occurs within a few milliseconds, we show that it is dominated by microscopic dynamics rather than bulk hydrodynamics.

Bile Salt-induced Biofilm Formation in Enteric Pathogens: Techniques for Identification and Quantification.

PubMed

Nickerson, Kourtney P; Faherty, Christina S

2018-05-06

Biofilm formation is a dynamic, multistage process that occurs in bacteria under harsh environmental conditions or times of stress. For enteric pathogens, a significant stress response is induced during gastrointestinal transit and upon bile exposure, a normal component of human digestion. To overcome the bactericidal effects of bile, many enteric pathogens form a biofilm hypothesized to permit survival when transiting through the small intestine. Here we present methodologies to define biofilm formation through solid-phase adherence assays as well as extracellular polymeric substance (EPS) matrix detection and visualization. Furthermore, biofilm dispersion assessment is presented to mimic the analysis of events triggering release of bacteria during the infection process. Crystal violet staining is used to detect adherent bacteria in a high-throughput 96-well plate adherence assay. EPS production assessment is determined by two assays, namely microscopy staining of the EPS matrix and semi-quantitative analysis with a fluorescently-conjugated polysaccharide binding lectin. Finally, biofilm dispersion is measured through colony counts and plating. Positive data from multiple assays support the characterization of biofilms and can be utilized to identify bile salt-induced biofilm formation in other bacterial strains.

A robust Ni(II) α-diimine catalyst for high temperature ethylene polymerization.

PubMed

Rhinehart, Jennifer L; Brown, Lauren A; Long, Brian K

2013-11-06

Sterically demanding Ni(II) α-diimine precatalysts were synthesized utilizing 2,6-bis(diphenylmethyl)-4-methyl aniline. When activated with methylaluminoxane, the catalyst NiBr2(ArN═C(Me)-C(Me)═NAr) (Ar = 2,6 bis(diphenylmethyl)-4-methylbenzene) was highly active, produced well-defined polyethylene at temperatures up to 100 °C (Mw/Mn = 1.09-1.46), and demonstrated remarkable thermal stability at temperatures appropriate for industrially used gas-phase polymerizations (80-100 °C).

Arsenite-induced mitotic death involves stress response and is independent of tubulin polymerization

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

Taylor, B. Frazier; McNeely, Samuel C.; Miller, Heather L.

2008-07-15

Arsenite, a known mitotic disruptor, causes cell cycle arrest and cell death at anaphase. The mechanism causing mitotic arrest is highly disputed. We compared arsenite to the spindle poisons nocodazole and paclitaxel. Immunofluorescence analysis of {alpha}-tubulin in interphase cells demonstrated that, while nocodazole and paclitaxel disrupt microtubule polymerization through destabilization and hyperpolymerization, respectively, microtubules in arsenite-treated cells remain comparable to untreated cells even at supra-therapeutic concentrations. Immunofluorescence analysis of {alpha}-tubulin in mitotic cells showed spindle formation in arsenite- and paclitaxel-treated cells but not in nocodazole-treated cells. Spindle formation in arsenite-treated cells appeared irregular and multi-polar. {gamma}-tubulin staining showed that cellsmore » treated with nocodazole and therapeutic concentrations of paclitaxel contained two centrosomes. In contrast, most arsenite-treated mitotic cells contained more than two centrosomes, similar to centrosome abnormalities induced by heat shock. Of the three drugs tested, only arsenite treatment increased expression of the inducible isoform of heat shock protein 70 (HSP70i). HSP70 and HSP90 proteins are intimately involved in centrosome regulation and mitotic spindle formation. HSP90 inhibitor 17-DMAG sensitized cells to arsenite treatment and increased arsenite-induced centrosome abnormalities. Combined treatment of 17-DMAG and arsenite resulted in a supra-additive effect on viability, mitotic arrest, and centrosome abnormalities. Thus, arsenite-induced abnormal centrosome amplification and subsequent mitotic arrest is independent of effects on tubulin polymerization and may be due to specific stresses that are protected against by HSP90 and HSP70.« less

The Radiation Induced Polymerization of Cyclophosphazene Trimers

DTIC Science & Technology

1989-01-04

Macromolecules, 19, 959 (1986). 14. J. W. Fieldhouse and S. L. Fenske , US Patent 4327064 (1982). 15. S. Ganapathiappan, K. S. Dhathathreyan, S. S...dianhydride. Decalin had been used in catalyzed polymerizations by Fieldhouse and Fenske 12]. This aliphatic hydrocarbon was judged to be innocuous from a...Stannelt, to be published. 2] J. W. Fieldhouse, and S. L. Fenske , US Patent 4327064 (1982). 3] R. B. Taylor, and F. Williams, J. Am. Chem. Soc., 21, 3728

Radiation-hardened polymeric films

DOEpatents

Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

1984-07-16

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Radiation-hardened polymeric films

DOEpatents

Arnold, Jr., Charles; Hughes, Robert C.; Kepler, R. Glen; Kurtz, Steven R.

1986-01-01

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Mutagenic analysis of the nucleation propensity of oxidized Alzheimer's beta-amyloid peptide.

PubMed

Christopeit, Tony; Hortschansky, Peter; Schroeckh, Volker; Gührs, Karlheinz; Zandomeneghi, Giorgia; Fändrich, Marcus

2005-08-01

The formation of polypeptide aggregates represents a nucleated polymerization reaction in which an initial nucleation event (lag phase) is followed by the extension of newly formed nuclei into larger aggregates, including fibrils (growth phase). The efficiencies of these reactions relate to the lag time (lag phase) and to the rate of aggregation (growth phase), which can be determined from experimental aggregation curves. Here we present a mutagenic analysis in which we replace valine 18 of the Alzheimer's Abeta (1-40) peptide with 17 different amino acids and determine its effect on the lag time, and therefore, on the propensity of nucleation. Comparison with various physico-chemical properties shows that nucleation is affected in a predictable manner depending on the beta-sheet propensity and hydrophobicity of residue 18. In addition, we observe a direct proportionality between the lag time and the rate of aggregation. These data imply that the two reactions, nucleation and polymerization, are governed by very similar physicochemical principles and that they involve the formation of the same types of noncovalent interactions.

ABC Triblock Copolymer Worms: Synthesis, Characterization, and Evaluation as Pickering Emulsifiers for Millimeter-Sized Droplets

PubMed Central

2016-01-01

Polymerization-induced self-assembly (PISA) is used to prepare linear poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate)–poly(benzyl methacrylate) [PGMA–PHPMA–PBzMA] triblock copolymer nano-objects in the form of a concentrated aqueous dispersion via a three-step synthesis based on reversible addition–fragmentation chain transfer (RAFT) polymerization. First, GMA is polymerized via RAFT solution polymerization in ethanol, then HPMA is polymerized via RAFT aqueous solution polymerization, and finally BzMA is polymerized via “seeded” RAFT aqueous emulsion polymerization. For certain block compositions, highly anisotropic worm-like particles are obtained, which are characterized by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The design rules for accessing higher order morphologies (i.e., worms or vesicles) are briefly explored. Surprisingly, vesicular morphologies cannot be accessed by targeting longer PBzMA blocks—instead, only spherical nanoparticles are formed. SAXS is used to rationalize these counterintuitive observations, which are best explained by considering subtle changes in the relative enthalpic incompatibilities between the three blocks during the growth of the PBzMA block. Finally, the PGMA–PHPMA–PBzMA worms are evaluated as Pickering emulsifiers for the stabilization of oil-in-water emulsions. Millimeter-sized oil droplets can be obtained using low-shear homogenization (hand-shaking) in the presence of 20 vol % n-dodecane. In contrast, control experiments performed using PGMA–PHPMA diblock copolymer worms indicate that these more delicate nanostructures do not survive even these mild conditions. PMID:27795581

Swelling-induced optical anisotropy of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate): deswelling kinetics probed by quantitative Mueller matrix polarimetry.

PubMed

Patil, Nagaraj; Soni, Jalpa; Ghosh, Nirmalya; De, Priyadarsi

2012-11-29

Thermodynamically favored polymer-water interactions below the lower critical solution temperature (LCST) caused swelling-induced optical anisotropy (linear retardance) of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate). This was exploited to study the macroscopic deswelling kinetics quantitatively by a generalized polarimetry analysis method, based on measurement of the Mueller matrix and its subsequent inverse analysis via the polar decomposition approach. The derived medium polarization parameters, namely, linear retardance (δ), diattenuation (d), and depolarization coefficient (Δ), of the hydrogels showed interesting differences between the gels prepared by conventional free radical polymerization (FRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and also between dry and swollen state. The effect of temperature, cross-linking density, and polymerization technique employed to synthesize hydrogel on deswelling kinetics was systematically studied via conventional gravimetry and corroborated further with the corresponding Mueller matrix derived quantitative polarimetry characteristics (δ, d, and Δ). The RAFT gels exhibited higher swelling ratio and swelling-induced optical anisotropy compared to FRP gels and also deswelled faster at 30 °C. On the contrary, at 45 °C, deswelling was significantly retarded for the RAFT gels due to formation of a skin layer, which was confirmed and quantified via the enhanced diattenuation and depolarization parameters.

High throughput atmospheric pressure plasma-induced graft polymerization for identifying protein-resistant surfaces.

PubMed

Gu, Minghao; Kilduff, James E; Belfort, Georges

2012-02-01

Three critical aspects of searching for and understanding how to find highly resistant surfaces to protein adhesion are addressed here with specific application to synthetic membrane filtration. They include the (i) discovery of a series of previously unreported monomers from a large library of monomers with high protein resistance and subsequent low fouling characteristics for membrane ultrafiltration of protein-containing fluids, (ii) development of a new approach to investigate protein-resistant mechanisms from structure-property relationships, and (iii) adaptation of a new surface modification method, called atmospheric pressure plasma-induced graft polymerization (APP), together with a high throughput platform (HTP), for low cost vacuum-free synthesis of anti-fouling membranes. Several new high-performing chemistries comprising two polyethylene glycol (PEG), two amines and one zwitterionic monomers were identified from a library (44 commercial monomers) of five different classes of monomers as strong protein-resistant monomers. Combining our analysis here, using the Hansen solubility parameters (HSP) approach, and data from the literature, we conclude that strong interactions with water (hydrogen bonding) and surface flexibility are necessary for producing the highest protein resistance. Superior protein-resistant surfaces and subsequent anti-fouling performance was obtained with the HTP-APP as compared with our earlier HTP-photo graft-induced polymerization (PGP). Copyright © 2011 Elsevier Ltd. All rights reserved.

A new indole-3-carbinol tetrameric derivative inhibits cyclin-dependent kinase 6 expression, and induces G1 cell cycle arrest in both estrogen-dependent and estrogen-independent breast cancer cell lines.

PubMed

Brandi, Giorgio; Paiardini, Mirko; Cervasi, Barbara; Fiorucci, Chiara; Filippone, Paolino; De Marco, Cinzia; Zaffaroni, Nadia; Magnani, Mauro

2003-07-15

Indole-3-carbinol (I3C), autolysis product of glucosinolates present in cruciferous vegetables, has been indicated as a promising agent in preventing the development and progression of breast cancer. I3C has been shown to inhibit the growth of human cancer cells in vitro and possesses anticarcinogenic activity in vivo. Because I3C is unstable and may be converted into many polymeric products in the digestive tract, it is not yet clear whether the biological activity observed can be attributed to I3C or some of its polymeric products. In this study we synthesized a stable I3C cyclic tetrameric derivative and investigated its effects on a panel of human breast cancer cell lines. The I3C tetramer suppressed the growth of both estrogen receptor (ER) -positive (MCF-7, 734B, and BT474) and ER-negative (BT20, MDA-MB-231, and BT539) human breast cancer cell lines, and it was found to induce G(1) cell cycle arrest in a dose-dependent manner without evidence of apoptosis, suggesting a growth arrest via a cytostatic mechanism. At the molecular level, the tetramer inhibited cyclin-dependent kinase (CDK) 6 expression and activity, induced an increase in the level of p27(kip1), and reduced the level of retinoblastoma protein expression. Contrarily to CDK6, the level of CDK4, the other kinase involved in the G(1) phase of the cell cycle, remains unchanged. Interestingly, the tetramer resulted about five times more active than I3C in suppressing the growth of human breast cancer cells. On the whole, our data suggest that the I3C tetrameric derivative is a novel lead inhibitor of breast cancer cell growth that may be a considered a new, promising therapeutic agent for both ER+ and ER- breast cancer.

Experimental conditions affecting the kinetics of aqueous HCN polymerization as revealed by UV-vis spectroscopy.

PubMed

Marín-Yaseli, Margarita R; Moreno, Miguel; de la Fuente, José L; Briones, Carlos; Ruiz-Bermejo, Marta

2018-02-15

HCN polymerization is one of the most important and fascinating reactions in prebiotic chemistry, and interest in HCN polymers in the field of materials science is growing. However, little is known about the kinetics of the HCN polymerization process. In the present study, a first approach to the kinetics of two sets of aqueous HCN polymerizations, from NH 4 CN and NaCN, at middle temperatures between 4 and 38°C, has been carried out. For each series, the presence of air and salts in the reaction medium has been systematically explored. A previous kinetic analysis was conducted during the conversion of the insoluble black HCN polymers obtained as gel fractions in these precipitation polymerizations for a reaction of one month, where a limit conversion was achieved at the highest polymerization temperature. The kinetic description of the gravimetric data for this complex system shows a clear change in the linear dependence with the polymerization temperature for the reaction from NH 4 CN, besides a relevant catalytic effect of ammonium, in comparison with those data obtained from the NaCN series. These results also demonstrated the notable influence of air, oxygen, and the saline medium in HCN polymer formation. Similar conclusions were reached when the sol fractions were monitored by UV-vis spectroscopy, and a Hill type correlation was used to describe the polymerization profiles obtained. This technique was chosen because it provides an easy, prompt and fast method to follow the evolution of the liquid or continuous phase of the process under study. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental conditions affecting the kinetics of aqueous HCN polymerization as revealed by UV-vis spectroscopy

NASA Astrophysics Data System (ADS)

Marín-Yaseli, Margarita R.; Moreno, Miguel; de la Fuente, José L.; Briones, Carlos; Ruiz-Bermejo, Marta

2018-02-01

HCN polymerization is one of the most important and fascinating reactions in prebiotic chemistry, and interest in HCN polymers in the field of materials science is growing. However, little is known about the kinetics of the HCN polymerization process. In the present study, a first approach to the kinetics of two sets of aqueous HCN polymerizations, from NH4CN and NaCN, at middle temperatures between 4 and 38 °C, has been carried out. For each series, the presence of air and salts in the reaction medium has been systematically explored. A previous kinetic analysis was conducted during the conversion of the insoluble black HCN polymers obtained as gel fractions in these precipitation polymerizations for a reaction of one month, where a limit conversion was achieved at the highest polymerization temperature. The kinetic description of the gravimetric data for this complex system shows a clear change in the linear dependence with the polymerization temperature for the reaction from NH4CN, besides a relevant catalytic effect of ammonium, in comparison with those data obtained from the NaCN series. These results also demonstrated the notable influence of air, oxygen, and the saline medium in HCN polymer formation. Similar conclusions were reached when the sol fractions were monitored by UV-vis spectroscopy, and a Hill type correlation was used to describe the polymerization profiles obtained. This technique was chosen because it provides an easy, prompt and fast method to follow the evolution of the liquid or continuous phase of the process under study.

Self-organized internal architectures of chiral micro-particles

NASA Astrophysics Data System (ADS)

Provenzano, Clementina; Mazzulla, Alfredo; Pagliusi, Pasquale; De Santo, Maria P.; Desiderio, Giovanni; Perrotta, Ida; Cipparrone, Gabriella

2014-02-01

The internal architecture of polymeric self-assembled chiral micro-particles is studied by exploring the effect of the chirality, of the particle sizes, and of the interface/surface properties in the ordering of the helicoidal planes. The experimental investigations, performed by means of different microscopy techniques, show that the polymeric beads, resulting from light induced polymerization of cholesteric liquid crystal droplets, preserve both the spherical shape and the internal self-organized structures. The method used to create the micro-particles with controlled internal chiral architectures presents great flexibility providing several advantages connected to the acquired optical and photonics capabilities and allowing to envisage novel strategies for the development of chiral colloidal systems and materials.

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.

PubMed

Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

2010-03-01

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure.

Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols.

PubMed

Couturier, Jean-Philippe; Wischerhoff, Erik; Bernin, Robert; Hettrich, Cornelia; Koetz, Joachim; Sütterlin, Martin; Tiersch, Brigitte; Laschewsky, André

2016-05-03

Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers' cloud point, or the induced changes of the hydrogels' swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye.

Fluctuation effects in blends of A + B homopolymers with AB diblock copolymer

NASA Astrophysics Data System (ADS)

Spencer, Russell K. W.; Matsen, Mark W.

2018-05-01

Field-theoretic simulations (FTSs) are performed on ternary blends of A- and B-type homopolymers of polymerization Nh and symmetric AB diblock copolymers of polymerization Nc. Unlike previous studies, our FTSs are conducted in three-dimensional space, with the help of two new semi-grand canonical ensembles. Motivated by the first experiment to discover bicontinuous microemulsion (BμE) in the polyethylene-polyethylene propylene system, we consider molecules of high molecular weight with size ratios of α ≡ Nh/Nc = 0.1, 0.2, and 0.4. Our focus is on the A + B coexistence between the two homopolymer-rich phases in the low-copolymer region of the phase diagram. The Scott line, at which the A + B phases mix to form a disordered melt with increasing temperature (or decreasing χ), is accurately determined using finite-size scaling techniques. We also examine how the copolymer affects the interface between the A + B phases, reducing the interfacial tension toward zero. Although comparisons with self-consistent field theory (SCFT) illustrate that fluctuation effects are relatively small, fluctuations do nevertheless produce the observed BμE that is absent in the SCFT phase diagram. Furthermore, we find evidence of three-phase A + B + BμE coexistence, which may have been missed in the original as well as subsequent experiments.

Phase formation and UV luminescence of Gd{sup 3+} doped perovskite-type YScO{sub 3}

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

Shimizu, Yuhei; Ueda, Kazushige, E-mail: kueda@che.kyutech.ac.jp

Synthesis of pure and Gd{sup 3+}doped perovskite-type YScO{sub 3} was attempted by a polymerized complex (PC) method and solid state reaction (SSR) method. Crystalline phases and UV luminescence of samples were examined with varying heating temperatures. The perovskite-type single phase was not simply formed in the SSR method, as reported in some literatures, and two cubic C-type phases of starting oxide materials remained forming slightly mixed solid solutions. UV luminescence of Gd{sup 3+} doped samples increased with an increase in heating temperatures and volume of the perovskite-type phase. In contrast, a non-crystalline precursor was crystallized to a single C-type phasemore » at 800 °C in the PC method forming a completely mixed solid solution. Then, the phase of perovskite-type YScO{sub 3} formed at 1200 °C and its single phase was obtained at 1400 °C. It was revealed that high homogeneousness of cations was essential to generate the single perovskite-phase of YScO{sub 3}. Because Gd{sup 3+} ions were also dissolved into the single C-type phase in Gd{sup 3+} doped samples, intense UV luminescence was observed above 800 °C in both C-type phase and perovskite-type phase. - Graphical abstract: A pure perovskite-type YScO{sub 3} phase was successfully synthesized by a polymerized complex (PC) method. The perovskite-type YScO{sub 3} was generated through a solid solution of C-type (Y{sub 0.5}Sc{sub 0.5}){sub 2}O{sub 3} with drastic change of morphology. The PC method enabled a preparation of the single phase of the perovskite-type YScO{sub 3} at lower temperature and in shorter heating time. Gd{sup 3+} doped perovskite-type YScO{sub 3} was found to show a strong sharp UV emission at 314 nm. - Highlights: • Pure YScO{sub 3} phase was successfully synthesized by polymerized complex (PC) method. • Pure perovskite-type YScO{sub 3} phase was generated from pure C-type (Y{sub 0.5}Sc{sub 0.5}){sub 2}O{sub 3} one. • YScO{sub 3} was obtained at lower temperature and in shorter heating time by PC method. • Perovskite-type YScO{sub 3}:Gd{sup 3+} was found to show strong sharp UV emission at 314 nm.« less

Analytical methods for the measurement of polymerization kinetics and stresses of dental resin-based composites: A review

PubMed Central

Ghavami-Lahiji, Mehrsima; Hooshmand, Tabassom

2017-01-01

Resin-based composites are commonly used restorative materials in dentistry. Such tooth-colored restorations can adhere to the dental tissues. One drawback is that the polymerization shrinkage and induced stresses during the curing procedure is an inherent property of resin composite materials that might impair their performance. This review focuses on the significant developments of laboratory tools in the measurement of polymerization shrinkage and stresses of dental resin-based materials during polymerization. An electronic search of publications from January 1977 to July 2016 was made using ScienceDirect, PubMed, Medline, and Google Scholar databases. The search included only English-language articles. Only studies that performed laboratory methods to evaluate the amount of the polymerization shrinkage and/or stresses of dental resin-based materials during polymerization were selected. The results indicated that various techniques have been introduced with different mechanical/physical bases. Besides, there are factors that may contribute the differences between the various methods in measuring the amount of shrinkages and stresses of resin composites. The search for an ideal and standard apparatus for measuring shrinkage stress and volumetric polymerization shrinkage of resin-based materials in dentistry is still required. Researchers and clinicians must be aware of differences between analytical methods to make proper interpretation and indications of each technique relevant to a clinical situation. PMID:28928776

Crystallization features of normal alkanes in confined geometry.

PubMed

Su, Yunlan; Liu, Guoming; Xie, Baoquan; Fu, Dongsheng; Wang, Dujin

2014-01-21

How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials. The confined geometry is closely related to both the phase metastability and lifetime of polymer. This affects the phase miscibility, microphase separation, and crystallization behaviors and determines both the performance of polymer materials and how easily these materials can be processed. Furthermore, the size effect of metastable states needs to be clarified in polymers. However, scientists find it difficult to propose a quantitative formula to describe the transition dynamics of metastable states in these complex systems. Normal alkanes [CnH2n+2, n-alkanes], especially linear saturated hydrocarbons, can provide a well-defined model system for studying the complex crystallization behaviors of polymer materials, surfactants, and lipids. Therefore, a deeper investigation of normal alkane phase behavior in confinement will help scientists to understand the crystalline phase transition and ultimate properties of many polymeric materials, especially polyolefins. In this Account, we provide an in-depth look at the research concerning the confined crystallization behavior of n-alkanes and binary mixtures in microcapsules by our laboratory and others. Since 2006, our group has developed a technique for synthesizing nearly monodispersed n-alkane containing microcapsules with controllable size and surface porous morphology. We applied an in situ polymerization method, using melamine-formaldehyde resin as shell material and nonionic surfactants as emulsifiers. The solid shell of microcapsules can provide a stable three-dimensional (3-D) confining environment. We have studied multiple parameters of these microencapsulated n-alkanes, including surface freezing, metastability of the rotator phase, and the phase separation behaviors of n-alkane mixtures using differential scanning calorimetry (DSC), temperature-dependent X-ray diffraction (XRD), and variable-temperature solid-state nuclear magnetic resonance (NMR). Our investigations revealed new direct evidence for the existence of surface freezing in microencapsulated n-alkanes. By examining the differences among chain packing and nucleation kinetics between bulk alkane solid solutions and their microencapsulated counterparts, we also discovered a mechanism responsible for the formation of a new metastable bulk phase. In addition, we found that confinement suppresses lamellar ordering and longitudinal diffusion, which play an important role in stabilizing the binary n-alkane solid solution in microcapsules. Our work also provided new insights into the phase separation of other mixed system, such as waxes, lipids, and polymer blends in confined geometry. These works provide a profound understanding of the relationship between molecular structure and material properties in the context of crystallization and therefore advance our ability to improve applications incorporating polymeric and molecular materials.

Stoichiometry of Nck-dependent actin polymerization in living cells

PubMed Central

Ditlev, Jonathon A.; Michalski, Paul J.; Huber, Greg; Rivera, Gonzalo M.; Mohler, William A.

2012-01-01

Regulation of actin dynamics through the Nck/N-WASp (neural Wiskott–Aldrich syndrome protein)/Arp2/3 pathway is essential for organogenesis, cell invasiveness, and pathogen infection. Although many of the proteins involved in this pathway are known, the detailed mechanism by which it functions remains undetermined. To examine the signaling mechanism, we used a two-pronged strategy involving computational modeling and quantitative experimentation. We developed predictions for Nck-dependent actin polymerization using the Virtual Cell software system. In addition, we used antibody-induced aggregation of membrane-targeted Nck SH3 domains to test these predictions and to determine how the number of molecules in Nck aggregates and the density of aggregates affected localized actin polymerization in living cells. Our results indicate that the density of Nck molecules in aggregates is a critical determinant of actin polymerization. Furthermore, results from both computational simulations and experimentation support a model in which the Nck/N-WASp/Arp2/3 stoichiometry is 4:2:1. These results provide new insight into activities involving localized actin polymerization, including tumor cell invasion, microbial pathogenesis, and T cell activation. PMID:22613834

Reactive centre loop mutants of α-1-antitrypsin reveal position-specific effects on intermediate formation along the polymerization pathway

PubMed Central

Haq, Imran; Irving, James A.; Faull, Sarah V.; Dickens, Jennifer A.; Ordóñez, Adriana; Belorgey, Didier; Gooptu, Bibek; Lomas, David A.

2013-01-01

The common severe Z mutation (E342K) of α1-antitrypsin forms intracellular polymers that are associated with liver cirrhosis. The native fold of this protein is well-established and models have been proposed from crystallographic and biophysical data for the stable inter-molecular configuration that terminates the polymerization pathway. Despite these molecular ‘snapshots’, the details of the transition between monomer and polymer remain only partially understood. We surveyed the RCL (reactive centre loop) of α1-antitrypsin to identify sites important for progression, through intermediate states, to polymer. Mutations at P14P12 and P4, but not P10P8 or P2P1′, resulted in a decrease in detectable polymer in a cell model that recapitulates the intracellular polymerization of the Z variant, consistent with polymerization from a near-native conformation. We have developed a FRET (Förster resonance energy transfer)-based assay to monitor polymerization in small sample volumes. An in vitro assessment revealed the position-specific effects on the unimolecular and multimolecular phases of polymerization: the P14P12 region self-inserts early during activation, while the interaction between P6P4 and β-sheet A presents a kinetic barrier late in the polymerization pathway. Correspondingly, mutations at P6P4, but not P14P12, yield an increase in the overall apparent activation energy of association from ~360 to 550 kJ mol−1. PMID:23659468

The Microstructure Analysis of Barium M- Hexaferrite Particles Coated by Pani Conducting Material with In Situ Polymerization Process

NASA Astrophysics Data System (ADS)

Zainuri, M.; Amalia, L.

2017-05-01

Barium M-Hexaferrite (BaM) was synthesized by coprecipitation method and doped with Zn. Polyaniline (PANI) was synthesized by chemically and doped DBSA. The composite of PANI/BaM was synthesized by in situ polymerization method. The phase identification of the sample was performed by XRD, FTIR and SEM. Based on XRD data, the phase composition of BaM and hematite are 85.52 % and 14.48%. The characteristic peaks of PANI occur at 3435, 1637, 1473, 1298, 1127, 1009, and 799 cm-1. The characteristic metal oxide stretching peaks of BaM occurs at 575 and 437 cm-1. There is no phase changing in PANI/BaM composite. Based on SEM photography, the shape of BaM is hexagonal. The particle size of BaM powder ranges from 400-700 nm. The qualitative interfacial bonding between PANI and BaM particles are conducted very well and the both materials have good wettability.

Phase correlation imaging of unlabeled cell dynamics

NASA Astrophysics Data System (ADS)

Ma, Lihong; Rajshekhar, Gannavarpu; Wang, Ru; Bhaduri, Basanta; Sridharan, Shamira; Mir, Mustafa; Chakraborty, Arindam; Iyer, Rajashekar; Prasanth, Supriya; Millet, Larry; Gillette, Martha U.; Popescu, Gabriel

2016-09-01

We present phase correlation imaging (PCI) as a novel approach to study cell dynamics in a spatially-resolved manner. PCI relies on quantitative phase imaging time-lapse data and, as such, functions in label-free mode, without the limitations associated with exogenous markers. The correlation time map outputted in PCI informs on the dynamics of the intracellular mass transport. Specifically, we show that PCI can extract quantitatively the diffusion coefficient map associated with live cells, as well as standard Brownian particles. Due to its high sensitivity to mass transport, PCI can be applied to studying the integrity of actin polymerization dynamics. Our results indicate that the cyto-D treatment blocking the actin polymerization has a dominant effect at the large spatial scales, in the region surrounding the cell. We found that PCI can distinguish between senescent and quiescent cells, which is extremely difficult without using specific markers currently. We anticipate that PCI will be used alongside established, fluorescence-based techniques to enable valuable new studies of cell function.

Polymeric phase change nanocomposite (PMMA/Fe:ZnO) for electronic packaging application

NASA Astrophysics Data System (ADS)

Maji, Pranabi; Choudhary, Ram Bilash; Majhi, Malati

2018-01-01

This paper reported the effect of Fe-doped ZnO (Fe:ZnO) nanoparticles on the structural, morphological, thermal, optical and dielectric properties of PMMA matrix. Fe-doped ZnO nanoparticle was synthesized by co-precipitation method, after its surface modification incorporated into the PMMA matrix by free radical polymerization method. The phase analysis and crystal structure were investigated by XRD and FTIR technique. These studies confirmed the chemical structure of the PMMA/Fe:ZnO nanocomposite. FESEM image showed the pyramidal shape and high porosity of PMMA/Fe:ZnO nanocomposite. Thermal analysis of the sample was carried out by thermo-gravimetric analyzer. PMMA/Fe:ZnO nanocomposite was found to have better thermal stability compared to pure one. Broadband dielectric spectroscopic technique was used to investigate the transition of electrical properties of Fe-doped ZnO nanoparticle reinforced PMMA matrix in temperature range 313-373 K. The results elucidated a phase transition from glassy to rubbery state at 344 K.

Features of separation on polymeric reversed phase for two classes of higher saturated fatty acids esters

NASA Astrophysics Data System (ADS)

Deineka, V. I.; Lapshova, M. S.; Zakharenko, E. V.; Deineka, L. A.

2013-11-01

The principles of sorption on polymeric reversed phase (PRP) YMS C30 for members of the two classes of esters formed by higher saturated fatty acids, i.e., lutein diesters ( I) and triacylglycerols ( II), are investigated. It is shown that the logarithm of the retention factor increases nonlinearly with an increase of the length of the acid radical, although the retention on PRP is higher in the case of I and lower in the case of II, compared to their retention on traditional monomeric reversed phase (MRP) Kromasil-100 5C18; however, the equivalence of the contributions to the retention of I that correspond to an identical change in acids, does not depend on the length of the hydrocarbon radical of the second acid. It is noted that the Van't Hoff plot for PRP contains a curve break, indicating a change in the retention mechanism upon a rise in temperature.

Synthesis of Novel μ-Star Copolymers with Poly(N-Octyl Benzamide) and Poly(ε-Caprolactone) Miktoarms through Chain-Growth Condensation Polymerization, Styrenics-Assisted Atom Transfer Radical Coupling, and Ring-Opening Polymerization.

PubMed

Huang, Chih-Feng; Aimi, Junko; Lai, Kuan-Yu

2017-02-01

Star copolymers are known to phase separate on the nanoscale, providing useful self-assembled morphologies. In this study, the authors investigate synthesis and assembly behavior of miktoarm star (μ-star) copolymers. The authors employ a new strategy for the synthesis of unprecedented μ-star copolymers presenting poly(N-octyl benzamide) (PBA) and poly(ε-caprolactone) (PCL) arms: a combination of chain-growth condensation polymerization, styrenics-assisted atom transfer radical coupling, and ring-opening polymerization. Gel permeation chromatography, mass-analyzed laser desorption/ionization mass spectrometry, and 1 H NMR spectroscopy reveal the successful synthesis of a well-defined (PBA 11 ) 2 -(PCL 15 ) 4 μ-star copolymer (M n ,NMR ≈ 12 620; Đ = 1.22). Preliminary examination of the PBA 2 PCL 4 μ-star copolymer reveals assembled nanofibers having a uniform diameter of ≈20 nm. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spiral actin-polymerization waves can generate amoeboidal cell crawling

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

Dreher, A.; Aranson, I. S.; Kruse, K.

2014-05-01

Amoeboidal cell crawling on solid substrates is characterized by protrusions that seemingly appear randomly along the cell periphery and drive the cell forward. For many cell types, it is known that the protrusions result from polymerization of the actin cytoskeleton. However, little is known about how the formation of protrusions is triggered and whether the appearance of subsequent protrusions is coordinated. Recently, the spontaneous formation of actin-polymerization waves was observed. These waves have been proposed to orchestrate the cytoskeletal dynamics during cell crawling. Here, we study the impact of cytoskeletal polymerization waves on cell migration using a phase-field approach. Inmore » addition to directionally moving cells, we find states reminiscent of amoeboidal cell crawling. In this framework, new protrusions are seen to emerge from a nucleation process, generating spiral actin waves in the cell interior. Nucleation of new spirals does not require noise, but occurs in a state that is apparently displaying spatio-temporal chaos.« less

Phosphine polymerization by nitric oxide: experimental characterization and theoretical predictions of mechanism.

PubMed

Zhao, Yi-Lei; Flora, Jason W; Thweatt, William David; Garrison, Stephen L; Gonzalez, Carlos; Houk, K N; Marquez, Manuel

2009-02-02

A yellow solid material [P(x)H(y)] has been obtained in the reaction of phosphine (PH(3)) and nitric oxide (NO) at room temperature and characterized by thermogravimetric analysis mass spectrometry (TGA-MS) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. In this work using complete basis set (CBS-QB3) methods a plausible mechanism has been investigated for phosphine polymerization in the presence of nitric oxide (NO). Theoretical explorations with the ab initio method suggest (a) instead of the monomer the nitric oxide dimer acts as an initial oxidant, (b) the resulting phosphine oxides (H(3)P=O <--> H(3)P(+)O(-)) in the gas phase draw each other via strong dipolar interactions between the P-O groups, and (c) consequently an autocatalyzed polymerization occurs among the phosphine oxides, forming P-P chemical bonds and losing water. The possible structures of polyhydride phosphorus polymer were discussed. In the calculations a series of cluster models was computed to simulate polymerization.

WE-D-210-04: Radiation-Induced Polymerization of Ultrasound Contrast Agents in View of Non-Invasive Dosimetry in External Beam Radiation Therapy

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

Callens, M; Verboven, E; Van Den Abeele, K

2015-06-15

Purpose: Ultrasound contrast agents (UCA’s) based on gas-filled microbubbles encapsulated by an amphiphilic shell are well established as safe and effective echo-enhancers in diagnostic imaging. In view of an alternative application of UCA’s, we investigated the use of targeted microbubbles as radiation sensors for external beam radiation therapy. As radiation induces permanent changes in the microbubble’s physico-chemical properties, a robust measure of these changes can provide a direct or indirect estimate of the applied radiation dose. For instance, by analyzing the ultrasonic dispersion characteristics of microbubble distributions before and after radiation treatment, an estimate of the radiation dose at themore » location of the irradiated volume can be made. To increase the radiation sensitivity of microbubbles, polymerizable diacetylene molecules can be incorporated into the shell. This study focuses on characterizing the acoustic response and quantifying the chemical modifications as a function of radiation dose. Methods: Lipid/diacetylene microbubbles were irradiated with a 6 MV photon beam using dose levels in the range of 0–150 Gy. The acoustic response of the microbubbles was monitored by ultrasonic through-transmission measurements in the range of 500 kHz to 20 MHz, thereby providing the dispersion relations of the phase velocity, attenuation and nonlinear coefficient. In addition, the radiation-induced chemical modifications were quantified using UV-VIS spectroscopy. Results: UV-VIS spectroscopy measurements indicate that ionizing radiation induces the polymerization of diacetylenes incorporated in the microbubble shell. The polymer yield strongly depends on the shell composition and the radiation-dose. The acoustic response is inherently related to the visco-elastic properties of the shell and is strongly influenced by the shell composition and the physico-chemical changes in the environment. Conclusion: Diacetylene-containing microbubbles are polymerizable under influence of ionizing radiation and are a promising design concept within the development of a novel non-invasive in-vivo radiation dosimeter for external beam radiation therapy. This work was funded by the Research Foundation - Flanders (FWO)« less

Electrical conductivity of multi-walled carbon nanotubes-SU8 epoxy composites

NASA Astrophysics Data System (ADS)

Grimaldi, Claudio; Mionić, Marijana; Gaal, Richard; Forró, László; Magrez, Arnaud

2013-06-01

We have characterized the electrical conductivity of the composite which consists of multi-walled carbon nanotubes dispersed in SU8 epoxy resin. Depending on the processing conditions of the epoxy (ranging from non-polymerized to cross-linked), we obtained tunneling and percolating-like regimes of the electrical conductivity of the composites. We interpret the observed qualitative change of the conductivity behavior in terms of reduced separation between the nanotubes induced by polymerization of the epoxy matrix.

Advantages and drawbacks of Thiol-ene based resins for 3D-printing

NASA Astrophysics Data System (ADS)

Leonards, Holger; Engelhardt, Sascha; Hoffmann, Andreas; Pongratz, Ludwig; Schriever, Sascha; Bläsius, Jana; Wehner, Martin; Gillner, Arnold

2015-03-01

The technology of 3D printing is conquering the world and awakens the interest of many users in the most varying of applications. New formulation approaches for photo-sensitive thiol-ene resins in combination with various printing technologies, like stereolithography (SLA), projection based printing/digital light processing (DLP) or two-photon polymerization (TPP) are presented. Thiol-ene polymerizations are known for its fast and quantitative reaction and to form highly homogeneous polymer networks. As the resins are locally and temporally photo-curable the polymerization type is very promising for 3D-printing. By using suitable wavelengths, photoinitiator-free fabrication is feasible for single- and two photon induced polymerization. In this paper divinyl ethers of polyethylene glycols in combination with star-shaped tetrathiols were used to design a simple test-system for photo-curable thiol-ene resins. In order to control and improve curing depth and lateral resolution in 3D-polymerization processes, either additives in chemical formulation or process parameters can be changed. The achieved curing depth and resolution limits depend on the applied fabrication method. While two-/multiphoton induced lithography offers the possibility of micron- to sub-micron resolution it lacks in built-up speed. Hence single-photon polymerization is a fast alternative with optimization potential in sub-10-micron resolution. Absorber- and initiator free compositions were developed in order to avoid aging, yellowing and toxicity of resulting products. They can be cured with UV-laser radiation below 300 nm. The development at Fraunhofer ILT is focusing on new applications in the field of medical products and implants, technical products with respect to mechanical properties or optical properties of 3D-printed objects. Recent process results with model system (polyethylene glycol divinylether/ Pentaerithrytol tetrakis (3-mercaptopropionat), Raman measurements of polymer conversion and surface modifications using bifunctional crosslinkers are presented with advantages, drawbacks and a general outlook.

A novel synthesis of polymeric CO via useful hard X-ray photochemistry

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

Pravica, Michael; Sneed, Daniel; Smith, Quinlan

We report on the synchrotron hard X-ray-induced decomposition of strontium oxalate (SrC 2O 4) pressurized to 7 GPa inside a diamond anvil cell (DAC). After some 4 h of irradiation in a white X-ray synchrotron beam, a dark reddish/brown region formed in the area of irradiation which was surrounded by a yellowish brown remainder in the rest of the sample. Upon depressurization of the sample to ambient conditions, the reacted/decomposed sample was recoverable as a dark brown/red and yellow waxy solid. Synchrotron infrared spectroscopy confirmed the strong presence of CO 2 even under ambient conditions with the sample exposed tomore » air and other strongly absorbing regions, suggesting that the sample may likely be polymerized CO (in part) with dispersed CO 2 and SrO trapped within the polymer. These results will have significant implications in the ability to readily produce and trap CO 2 in situ via irradiation of a simple powder for useful hard X-ray photochemistry and in the ability to easily manufacture polymeric CO (via loading of powders in a DAC or high volume press) without the need for the dangerous and complex loading of toxic CO. As a result, a novel means of X-ray-induced polymerization under extreme conditions has also been demonstrated.« less

A novel synthesis of polymeric CO via useful hard X-ray photochemistry

DOE PAGES

Pravica, Michael; Sneed, Daniel; Smith, Quinlan; ...

2016-03-30

We report on the synchrotron hard X-ray-induced decomposition of strontium oxalate (SrC 2O 4) pressurized to 7 GPa inside a diamond anvil cell (DAC). After some 4 h of irradiation in a white X-ray synchrotron beam, a dark reddish/brown region formed in the area of irradiation which was surrounded by a yellowish brown remainder in the rest of the sample. Upon depressurization of the sample to ambient conditions, the reacted/decomposed sample was recoverable as a dark brown/red and yellow waxy solid. Synchrotron infrared spectroscopy confirmed the strong presence of CO 2 even under ambient conditions with the sample exposed tomore » air and other strongly absorbing regions, suggesting that the sample may likely be polymerized CO (in part) with dispersed CO 2 and SrO trapped within the polymer. These results will have significant implications in the ability to readily produce and trap CO 2 in situ via irradiation of a simple powder for useful hard X-ray photochemistry and in the ability to easily manufacture polymeric CO (via loading of powders in a DAC or high volume press) without the need for the dangerous and complex loading of toxic CO. As a result, a novel means of X-ray-induced polymerization under extreme conditions has also been demonstrated.« less

Leveraging Engineering of Indocyanine Green-Encapsulated Polymeric Nanocomposites for Biomedical Applications.

PubMed

Han, Ya-Hui; Kankala, Ranjith Kumar; Wang, Shi-Bin; Chen, Ai-Zheng

2018-05-24

In recent times, photo-induced therapeutics have attracted enormous interest from researchers due to such attractive properties as preferential localization, excellent tissue penetration, high therapeutic efficacy, and minimal invasiveness, among others. Numerous photosensitizers have been considered in combination with light to realize significant progress in therapeutics. Along this line, indocyanine green (ICG), a Food and Drug Administration (FDA)-approved near-infrared (NIR, >750 nm) fluorescent dye, has been utilized in various biomedical applications such as drug delivery, imaging, and diagnosis, due to its attractive physicochemical properties, high sensitivity, and better imaging view field. However, ICG still suffers from certain limitations for its utilization as a molecular imaging probe in vivo, such as concentration-dependent aggregation, poor in vitro aqueous stability and photodegradation due to various physicochemical attributes. To overcome these limitations, much research has been dedicated to engineering numerous multifunctional polymeric composites for potential biomedical applications. In this review, we aim to discuss ICG-encapsulated polymeric nanoconstructs, which are of particular interest in various biomedical applications. First, we emphasize some attractive properties of ICG (including physicochemical characteristics, optical properties, metabolic features, and other aspects) and some of its current limitations. Next, we aim to provide a comprehensive overview highlighting recent reports on various polymeric nanoparticles that carry ICG for light-induced therapeutics with a set of examples. Finally, we summarize with perspectives highlighting the significant outcome, and current challenges of these nanocomposites.

Surface-induced polymerization of actin.

PubMed Central

Renault, A; Lenne, P F; Zakri, C; Aradian, A; Vénien-Bryan, C; Amblard, F

1999-01-01

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m. PMID:10049338

Redox and pH Dual-Responsive Polymeric Micelles with Aggregation-Induced Emission Feature for Cellular Imaging and Chemotherapy.

PubMed

Zhuang, Weihua; Xu, Yangyang; Li, Gaocan; Hu, Jun; Ma, Boxuan; Yu, Tao; Su, Xin; Wang, Yunbing

2018-05-21

Intelligent polymeric micelles for antitumor drug delivery and tumor bioimaging have drawn a broad attention because of their reduced systemic toxicity, enhanced efficacy of drugs, and potential application of tumor diagnosis. Herein, we developed a multifunctional polymeric micelle system based on a pH and redox dual-responsive mPEG-P(TPE- co-AEMA) copolymer for stimuli-triggered drug release and aggregation-induced emission (AIE) active imaging. These mPEG-P(TPE- co-AEMA)-based micelles showed excellent biocompatibility and emission property, exhibiting great potential application for cellular imaging. Furthermore, the antitumor drug doxorubicin (DOX) could be encapsulated during self-assembly process with high loading efficiency, and a DOX-loaded micelle system with a size of 68.2 nm and narrow size distribution could be obtained. DOX-loaded micelles demonstrated great tumor suppression ability in vitro, and the dual-responsive triggered intracellular drug release could be further traced. Moreover, DOX-loaded micelles could efficiently accumulate at the tumor site because of enhanced permeability and retention effect and long circulation of micelles. Compared with free DOX, DOX-loaded micelles exhibited better antitumor effect and significantly reduced adverse effects. Given the efficient accumulation targeting to tumor tissue, dual-responsive drug release, and excellent AIE property, this polymeric micelle would be a potential candidate for cancer therapy and diagnosis.

Redox-Responsive Biomimetic Polymeric Micelle for Simultaneous Anticancer Drug Delivery and Aggregation-Induced Emission Active Imaging.

PubMed

Hu, Jun; Zhuang, Weihua; Ma, Boxuan; Su, Xin; Yu, Tao; Li, Gaocan; Hu, Yanfei; Wang, Yunbing

2018-05-10

Intelligent polymeric micelles have been developed as potential nanoplatforms for efficient drug delivery and diagnosis. Herein, we successfully prepared redox-sensitive polymeric micelles combined aggregation-induced emission (AIE) imaging as an outstanding anticancer drug carrier system for simultaneous chemotherapy and bioimaging. The amphiphilic copolymer TPE-SS-PLAsp- b-PMPC could self-assemble into spherical micelles, and these biomimetic micelles exhibited great biocompatibility and remarkable ability in antiprotein adsorption, showing great potential for biomedical application. Anticancer drug doxorubicin (DOX) could be encapsulated during the self-assembly process, and these drug-loaded micelles showed intelligent drug release and improved antitumor efficacy due to the quick disassembly in response to high levels of glutathione (GSH) in the environment. Moreover, the intracellular DOX release could be traced through the fluorescent imaging of these AIE micelles. As expected, the in vivo antitumor study exhibited that these DOX-carried micelles showed better antitumor efficacy and less adverse effects than that of free DOX. These results strongly indicated that this smart biomimetic micelle system would be a prominent candidate for chemotherapy and bioimaging.

Emulsion-Assisted Polymerization-Induced Hierarchical Self-Assembly of Giant Sea Urchin-like Aggregates in a Large Scale.

PubMed

Xu, Qingsong; Huang, Tong; Li, Shanlong; Li, Ke; Li, Chuanlong; Liu, Yannan; Wang, Yuling; Yu, Chunyang; Zhou, Yongfeng

2018-05-09

Hierarchical solution self-assembly has nowadays become an important biomimetic method to prepare highly complex and multifunctional supramolecular structures. However, despites the great progress, it is still highly challenging to prepare hierarchical self-assemblies in a large scale since the self-assembly processes are generally performed at high dilution. Herein, we report an emulsion-assisted polymerization-induced self-assembly (EAPISA) method with the advantages of in-situ self-assembly process, scalable preparation and facile functionalization to prepare hierarchical multiscale sea urchin-like aggregates (SUAs). It also extends horizons of PISA in monomers and in polymerization method. The obtained SUAs from amphiphilic alternating copolymers represent a novel self-assembled structure with micron-sized rattan ball-like capsule (RBC) acting as the hollow core body and radiating nanotubes tens of micrometers in length as the hollow spines. They can effectively capture model proteins at an ultra-low concentration (≈10 nM) after functionalized with amino groups through click copolymerization. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonlinear photomechanics of nematic networks: upscaling microscopic behaviour to macroscopic deformation

NASA Astrophysics Data System (ADS)

Chung, Hayoung; Choi, Joonmyung; Yun, Jung-Hoon; Cho, Maenghyo

2016-02-01

A liquid crystal network whose chromophores are functionalized by photochromic dye exhibits light-induced mechanical behaviour. As a result, the micro-scaled thermotropic traits of the network and the macroscopic phase behaviour are both influenced as light alternates the shape of the dyes. In this paper, we present an analysis of this photomechanical behaviour based on the proposed multiscale framework, which incorporates the molecular details of microstate evolution into a continuum-based understanding. The effects of trans-to-cis photoisomerization driven by actinic light irradiation are first examined using molecular dynamics simulations, and are compared against the predictions of the classical dilution model; this reveals certain characteristics of mesogenic interaction upon isomerization, followed by changes in the polymeric structure. We then upscale the thermotropic phase-related information with the aid of a nonlinear finite element analysis; macroscopic deflection with respect to the wide ranges of temperature and actinic light intensity are thereby examined, which reveals that the classical model underestimates the true deformation. This work therefore provides measures for analysing photomechanics in general by bridging the gap between the micro- and macro-scales.

Superhydrophobic perfluoropolymer/polystyrene blend films induced by nonsolvent

NASA Astrophysics Data System (ADS)

Gengec, Nevin Atalay; Cengiz, Ugur; Erbil, H. Yildirim

2016-10-01

Statistical copolymers of perfluoroalkyl ethyl acrylate (Zonyl-TAN) and methyl methacrylate (MMA) were synthesized in a CO2 polymerization system where a CO2-expanded monomer mixture was formed at 13 MPa, and 80 °C by using AIBN as initiator. Flat and superhydrophobic surfaces were subsequently prepared on glass slides by applying a phase separation process where the synthesized p(TAN-co-MMA) copolymer and polystyrene (PS) were dissolved in THF solvent. Ethanol was added as the non-solvent to introduce superhydrophobicity during film formation. Water contact angle on the flat p(TAN-co-MMA) copolymer was 118° and increased up to 170° with the formation of surface roughness. The ratio of the ethanol non-solvent in the blend solution has an important effect on the magnitude of surface roughness during the phase separation process. Both pits and protrusions of 1-10 μm in size were formed on the surface when non-solvent was used. Surface roughness increased with the increase in the ethanol ratio and the PS content of the blend solution.

Preparation of ellagic acid molecularly imprinted polymeric microspheres based on distillation-precipitation polymerization for the efficient purification of a crude extract.

PubMed

Zhang, Hua; Zhao, Shangge; Zhang, Lu; Han, Bo; Yao, Xincheng; Chen, Wen; Hu, Yanli

2016-08-01

Molecularly imprinted polymeric microspheres with a high recognition ability toward the template molecule, ellagic acid, were synthesized based on distillation-precipitation polymerization. The as-obtained polymers were characterized by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. Static, dynamic, and selective binding tests were adopted to study the binding properties and the molecular recognition ability of the prepared polymers for ellagic acid. The results indicated that the maximum static adsorption capacity of the prepared polymers toward ellagic acid was 37.07 mg/g and the adsorption equilibrium time was about 100 min when the concentration of ellagic acid was 40 mg/mL. Molecularly imprinted polymeric microspheres were also highly selective toward ellagic acid compared with its analogue quercetin. It was found that the content of ellagic acid in the pomegranate peel extract was enhanced from 23 to 86% after such molecularly imprinted solid-phase extraction process. This work provides an efficient way for effective separation and enrichment of ellagic acid from complex matrix, which is especially valuable in industrial production. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phosphines bearing alkyne substituents: synthesis and hydrophosphination polymerization.

PubMed

Greenberg, Sharonna; Stephan, Douglas W

2009-09-07

A synthetic route is described for a series of phosphines bearing pendant alkyne substituents, from the conversion of BrC(6)H(2)R(2)C[triple bond]CR' (R = Me, i-Pr; R' = Ph, SiMe(3)) to [(mu-Br)Cu(Et(2)N)(2)PC(6)H(2)R(2)C[triple bond]CR'](2) and subsequently to Cl(2)PC(6)H(2)R(2)C[triple bond]CR' and H(2)PC(6)H(2)R(2)C[triple bond]CR'. Lithiation and subsequent alkylation yield the secondary phosphines R(H)PC(6)H(2)(i-Pr)(2)C[triple bond]CPh (R = CH(2)i-Pr, CH(2)Ph). Intermolecular hydrophosphination-polymerization is used to prepare the polymeric species [RPC(6)H(2)(i-Pr)(2)CH=CPh](n), which can then be sulfurized to give [RP(S)C(6)H(2)(i-Pr)(2)CH=CPh](n). The polymeric products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and gel permeation chromatography. These data indicate a degree of polymerization (DP(n)) of up to 60. Discussion of the mechanism is augmented with gas-phase density functional theory calculations.

CVD Polymers for Devices and Device Fabrication.

PubMed

Wang, Minghui; Wang, Xiaoxue; Moni, Priya; Liu, Andong; Kim, Do Han; Jo, Won Jun; Sojoudi, Hossein; Gleason, Karen K

2017-03-01

Chemical vapor deposition (CVD) polymerization directly synthesizes organic thin films on a substrate from vapor phase reactants. Dielectric, semiconducting, electrically conducting, and ionically conducting CVD polymers have all been readily integrated into devices. The absence of solvent in the CVD process enables the growth of high-purity layers and avoids the potential of dewetting phenomena, which lead to pinhole defects. By limiting contaminants and defects, ultrathin (<10 nm) CVD polymeric device layers have been fabricated in multiple laboratories. The CVD method is particularly suitable for synthesizing insoluble conductive polymers, layers with high densities of organic functional groups, and robust crosslinked networks. Additionally, CVD polymers are prized for the ability to conformally cover rough surfaces, like those of paper and textile substrates, as well as the complex geometries of micro- and nanostructured devices. By employing low processing temperatures, CVD polymerization avoids damaging substrates and underlying device layers. This report discusses the mechanisms of the major CVD polymerization techniques and the recent progress of their applications in devices and device fabrication, with emphasis on initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent advances of basic materials to obtain electrospun polymeric nanofibers for medical applications

NASA Astrophysics Data System (ADS)

Manea, L. R.; Hristian, L.; Leon, A. L.; Popa, A.

2016-08-01

The most important applications of electrospun polymeric nanofibers are by far those from biomedical field. From the biological point of view, almost all the human tissues and organs consist of nanofibroas structures. The examples include the bone, dentine, cartilage, tendons and skin. All these are characterized through different fibrous structures, hierarchically organized at nanometer scale. Electrospinning represents one of the nanotechnologies that permit to obtain such structures for cell cultures, besides other technologies, such as selfassembling and phase separation technologies. The basic materials used to produce electrospun nanofibers can be natural or synthetic, having polymeric, ceramic or composite nature. These materials are selected depending of the nature and structure of the tissue meant to be regenerated, namely: for the regeneration of smooth tissues regeneration one needs to process through electrospinning polymeric basic materials, while in order to obtain the supports for the regeneration of hard tissues one must mainly use ceramic materials or composite structures that permit imbedding the bioactive substances in distinctive zones of the matrix. This work presents recent studies concerning basic materials used to obtain electrospun polymeric nanofibers, and real possibilities to produce and implement these nanofibers in medical bioengineering applications.

A Robust Damage-Reporting Strategy for Polymeric Materials Enabled by Aggregation-Induced Emission.

PubMed

Robb, Maxwell J; Li, Wenle; Gergely, Ryan C R; Matthews, Christopher C; White, Scott R; Sottos, Nancy R; Moore, Jeffrey S

2016-09-28

Microscopic damage inevitably leads to failure in polymers and composite materials, but it is difficult to detect without the aid of specialized equipment. The ability to enhance the detection of small-scale damage prior to catastrophic material failure is important for improving the safety and reliability of critical engineering components, while simultaneously reducing life cycle costs associated with regular maintenance and inspection. Here, we demonstrate a simple, robust, and sensitive fluorescence-based approach for autonomous detection of damage in polymeric materials and composites enabled by aggregation-induced emission (AIE). This simple, yet powerful system relies on a single active component, and the general mechanism delivers outstanding performance in a wide variety of materials with diverse chemical and mechanical properties.

Structural and Functional Consequences of Increased Tubulin Glycosylation in Diabetes Mellitus

NASA Astrophysics Data System (ADS)

Williams, Stuart K.; Howarth, Nancy L.; Devenny, James J.; Bitensky, Mark W.

1982-11-01

The extent of in vitro nonenzymatic glycosylation of purified rat brain tubulin was dependent on time and glucose concentration. Tubulin glycosylation profoundly inhibited GTP-dependent tubulin polymerization. Electron microscopy and NaDodSO4/polyacrylamide gel electrophoresis showed that glycosylated tubulin forms high molecular weight amorphous aggregates that are not disrupted by detergents or reducing agents. The amount of covalently bound NaB3H4-reducible sugars in tubulin recovered from brain of streptozotocin-induced diabetic rats was dramatically increased as compared with tubulin recovered from normal rat brain. Moreover, tubulin recovered from diabetic rat brain exhibited less GTP-induced polymerization than tubulin from nondiabetic controls. The possible implications of these data for diabetic neuropathy are discussed.

Melt-Flow Behaviours of Thermoplastic Materials under Fire Conditions: Recent Experimental Studies and Some Theoretical Approaches

PubMed Central

Joseph, Paul; Tretsiakova-McNally, Svetlana

2015-01-01

Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years, more quantitative attempts to measure the mass loss and melt-drip behaviour of some commercially important chain- and step-growth polymers have been accomplished. The present article focuses, primarily, on the experimental and some theoretical aspects of melt-flow behaviours of thermoplastics under heat/fire conditions. PMID:28793746

Vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) on commercial carbon coated aluminum foil as enhanced electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Tong, Linyue; Skorenko, Kenneth H.; Faucett, Austin C.; Boyer, Steven M.; Liu, Jian; Mativetsky, Jeffrey M.; Bernier, William E.; Jones, Wayne E.

2015-11-01

Laminar composite electrodes are prepared for application in supercapacitors using a catalyzed vapor-phase polymerization (VPP) of 3,4-ethylenedioxythiophene (EDOT) on the surface of commercial carbon coated aluminum foil. These highly electrically conducting polymer films provide for rapid and stable power storage per gram at room temperature. The chemical composition, surface morphology and electrical properties are characterized by Raman spectroscopy, scanning electron microscopy (SEM), and conducting atomic force microscopy (C-AFM). A series of electrical measurements including cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy are also used to evaluate electrical performance. The processing temperature of VPP shows a significant effect on PEDOT morphology, the degree of orientation and its electrical properties. The relatively high temperature leads to high specific area and large conductive domains of PEDOT layer which benefits the capacitive behavior greatly according to the data presented. Since the substrate is already highly conductive, the PEDOT based composite can be used as electrode materials directly without adding current collector. By this simple and efficient process, PEDOT based composites exhibit specific capacitance up to 134 F g-1 with the polymerization temperature of 110 °C.

Sorption of small molecules in polymeric media

NASA Astrophysics Data System (ADS)

Camboni, Federico; Sokolov, Igor M.

2016-12-01

We discuss the sorption of penetrant molecules from the gas phase by a polymeric medium within a model which is very close in spirit to the dual sorption mode model: the penetrant molecules are partly dissolved within the polymeric matrix, partly fill the preexisting voids. The only difference with the initial dual sorption mode situation is the assumption that the two populations of molecules are in equilibrium with each other. Applying basic thermodynamics principles we obtain the dependence of the penetrant concentration on the pressure in the gas phase and find that this is expressed via the Lambert W-function, a different functional form than the one proposed by dual sorption mode model. The Lambert-like isotherms appear universally at low and moderate pressures and originate from the assumption that the internal energy in a polymer-penetrant-void ternary mixture is (in the lowest order) a bilinear form in the concentrations of the three components. Fitting the existing data shows that in the domain of parameters where the dual sorption mode model is typically applied, the Lambert function, which describes the same behavior as the one proposed by the gas-polymer matrix model, fits the data equally well.

Preparation of sulfonated graphene/polypyrrole solid-phase microextraction coating by in situ electrochemical polymerization for analysis of trace terpenes.

PubMed

Zhang, Chengjiang; Zhang, Zhuomin; Li, Gongke

2014-06-13

In this study, a novel sulfonated graphene/polypyrrole (SG/PPy) solid-phase microextraction (SPME) coating was prepared and fabricated on a stainless-steel wire by a one-step in situ electrochemical polymerization method. Crucial preparation conditions were optimized as polymerization time of 15min and SG doping amount of 1.5mg/mL. SG/PPy coating showed excellent thermal stability and mechanical durability with a long lifespan of more than 200 stable replicate extractions. SG/PPy coating demonstrated higher extraction selectivity and capacity to volatile terpenes than commonly-used commercial coatings. Finally, SG/PPy coating was practically applied for the analysis of volatile components from star anise and fennel samples. The majority of volatile components identified were terpenes, which suggested the ultra-high extraction selectivity of SG/PPy coating to terpenes during real analytical projects. Four typical volatile terpenes were further quantified to be 0.2-27.4μg/g from star anise samples with good recoveries of 76.4-97.8% and 0.1-1.6μg/g from fennel samples with good recoveries of 80.0-93.1%, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Formulation and characterization of polymeric films containing combinations of antiretrovirals (ARVs) for HIV prevention.

PubMed

Akil, Ayman; Agashe, Hrushikesh; Dezzutti, Charlene S; Moncla, Bernard J; Hillier, Sharon L; Devlin, Brid; Shi, Yuan; Uranker, Kevin; Rohan, Lisa Cencia

2015-02-01

To develop polymeric films containing dual combinations of anti-HIV drug candidate tenofovir, maraviroc and dapivirine for vaginal application as topical microbicides. A solvent casting method was used to manufacture the films. Solid phase solubility was used to identify potential polymers for use in the film formulation. Physical and chemical properties (such as water content, puncture strength and in vitro release) and product stability were determined. The bioactivity of the film products against HIV was assessed using the TZM-bl assay and a cervical explant model. Polymers identified from the solid phase solubility study maintained tenofovir and maraviroc in an amorphous state and prevented drug crystallization. Three combination film products were developed using cellulose polymers and polyvinyl alcohol. The residual water content in all films was <10% (w/w). All films delivered the active agents with release of >50% of film drug content within 30 min. Stability testing confirmed that the combination film products were stable for 12 months at ambient temperature and 6 months under stressed conditions. Antiviral activity was confirmed in TZM-bl and cervical explant models. Polymeric films can be used as a stable dosage form for the delivery of antiretroviral combinations as microbicides.

Melt-Flow Behaviours of Thermoplastic Materials under Fire Conditions: Recent Experimental Studies and Some Theoretical Approaches.

PubMed

Joseph, Paul; Tretsiakova-McNally, Svetlana

2015-12-15

Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years, more quantitative attempts to measure the mass loss and melt-drip behaviour of some commercially important chain- and step-growth polymers have been accomplished. The present article focuses, primarily, on the experimental and some theoretical aspects of melt-flow behaviours of thermoplastics under heat/fire conditions.

Synthesis and chromatographic characterization of dextran-coated zirconia high-performance liquid chromatographic stationary phases.

PubMed

Dunlap, C J; Carr, P W

1996-10-11

Porous zirconia particles made by the oil emulsion (OE) method and the polymerization-induced colloid aggregation (PICA) method have been coated with a small, carboxymethylated (approximately 5%) dextran polymer and crosslinked in place. The parameters of the coating process (dextran concentration, adsorption time and crosslinker concentration) have all been examined and an optimum value for each determined. The coated and uncoated materials were characterized by nitrogen sorptometry and size-exclusion chromatography (SEC) using solutes (polystyrenes and dextrans) of well-defined molecular masses. Nitrogen sorptometry results show that the PICA material has a much lower pore volume and smaller pore diameter than do the OE materials. Despite this, the elution volumes of the SEC probes change very little upon polymer coating the PICA material while the OE material shows a very large change upon coating.

Mechanical Properties of Organized Microcomposites Fabricated by Interference Lithography

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Chang, Sehoon; Jang, Ji-Hyun; Davis, Whitney; Thomas, Edwin; Tsukruk, Vladimir

2009-03-01

We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized in a highly non-traditional field of ordered microcomposites. Organized microcomposite structures are fabricated by employing two independent strategies, namely, capillary infiltration and in situ polymerization of the rubbery component into the porous glassy microframes. The mechanical properties and ultimate fracture behavior of the single and bicomponent microframes are investigated at different length scales. The ordered single and bi-component microstructures with high degree of control over the microscopic organization of the polymeric phases result in excellent mechanical properties. Combining hard and soft polymer components provides multifunctional materials and coatings with synergetic properties and is frequently utilized for design of advanced polymeric composites.

Highly efficient and selective pressure-assisted photon-induced polymerization of styrene

NASA Astrophysics Data System (ADS)

Guan, Jiwen; Song, Yang

2016-06-01

The polymerization process of condensed styrene to produce polystyrene as an industrially important polymeric material was investigated using a novel approach by combining external compression with ultraviolet radiation. The reaction evolution was monitored as a function of time and the reaction products were characterized by in situ Fourier transform infrared spectroscopy. By optimizing the loading pressures, we observed highly efficient and selective production of polystyrene of different tacticities. Specifically, at relatively low loading pressures, infrared spectra suggest that styrene monomers transform to amorphous atactic polystyrene (APS) with minor crystalline isotactic polystyrene. In contrast, APS was found to be the sole product when polymerization occurs at relatively higher loading pressures. The time-dependent reaction profiles allow the examination of the polymerization kinetics by analyzing the rate constant and activation volume as a function of pressure. As a result, an optimized pressure condition, which allows a barrierless reaction to proceed, was identified and attributed to the very desirable reaction yield and kinetics. Finally, the photoinitiated reaction mechanism and the growth geometry of the polymer chains were investigated from the energy diagram of styrene and by the topology analysis of the crystal styrene. This study shows strong promise to produce functional polymeric materials in a highly efficient and controlled manner.

Continuous administration of an elemental diet induces insulin resistance in neonatal pigs

USDA-ARS?s Scientific Manuscript database

We previously showed that total parenteral nutrition (TPN) compared to intermittent enteral feeding of a milk-based formula induces insulin resistance and hepatic steatosis in neonatal pigs. We hypothesized that intravenous (IV) feeding rather than the nature of the diet (elemental vs polymeric) or ...

Mouse IgA inhibits cell growth by stimulating tumor necrosis factor-alpha production and apoptosis of macrophage cell lines.

PubMed

Reljic, Rajko; Crawford, Carol; Challacombe, Stephen; Ivanyi, Juraj

2004-04-01

Potent Fcalpha-mediated actions of IgA have previously been shown for myeloid cells from man, but much less is known in relation to murine cells. Here, we report that mouse monoclonal IgA, irrespective of their antigenic specificity, inhibit the proliferation of mouse macrophage cell lines. The anti-proliferative activity was manifested by both monomeric and polymeric mouse IgA, but not by mouse monoclonal IgG and IgM. Growth of J774 cells was significantly inhibited during the 4-8 days of logarithmic growth, followed by a subsequent recovery of cell numbers prior to the stationary phase. We demonstrated that IgA binds to J774 cells, stimulates tumor necrosis factor (TNF)-alpha production and induces apoptosis which is not dependent on NO or FAS/CD95. We also demonstrated that IgA, in synergy with IFN-gamma, induced TNF-alpha production and apoptosis of thioglycollate-elicited mouse peritoneal macrophages. Thus, the in vitro actions of IgA described may also play a regulatory role for mouse macrophages in vivo.

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

Yang, Xi; Wang, Shanshan; Ghiviriga, Ion

A novel synthetic method to create gold based metallo–oligomers/polymers via the combination of inorganic click (iClick) with intermolecular aurophilic interactions is demonstrated. Complexes [PEt 3Au] 4(μ-N 3C 2C 6H 5) (1) and [PPhMe 2Au] 43C 2C 6H 5) (2) and {[PEt 3Au] 4[(μ-N 3C 2) 2-9,9-dihexyl-9H-fluorene]} n (8) have been synthesized via iClick. The tetranuclear structures of 1 and 2, induced by aurophilic bonding, are confirmed in the solid state through single crystal X-ray diffraction experiments and in solution via variable temperature NMR spectroscopy. The extended 1D structure of 8 is constructed by aurophilic induced self-assembly. 1H DOSY NMR analysismore » reveals that the aurophilic bonds in 1, 2, and 8 are retained in the solution phase. The degree of polymerization within complex 8 is temperature and concentration dependent, as determined by 1H DOSY NMR. The complex 8 is a rare example of a solution stable higher ordered structure linked by aurophilic interactions.« less

Polymer-coated compliant receivers for intact laser-induced forward transfer of thin films: experimental results and modelling

NASA Astrophysics Data System (ADS)

Feinaeugle, Matthias; Horak, Peter; Sones, Collin L.; Lippert, Thomas; Eason, Rob W.

2014-09-01

In this study, we investigate both experimentally and numerically laser-induced forward transfer (LIFT) of thin films to determine the role of a thin polymer layer coating the receiver with the aim of modifying the rate of deceleration and reduction of material stress preventing intact material transfer. A numerical model of the impact phase during LIFT shows that such a layer reduces the modelled stress. The evolution of stress within the transferred deposit and the substrate as a function of the thickness of the polymer layer, the transfer velocity and the elastic properties of the polymer are evaluated. The functionality of the polymer layer is verified experimentally by LIFT printing intact 1- m-thick bismuth telluride films and polymeric light-emitting diode pads onto a layer of 12-m-thick polydimethylsiloxane and 50-nm-thick poly(3,4-ethylenedioxythiophene) blended with poly(styrenesulfonate) (PEDOT:PSS), respectively. Furthermore, it is demonstrated experimentally that the introduction of such a compliant layer improves adhesion between the deposit and its substrate.

Ion-dependent Polymerization Differences between Mammalian β- and γ-Nonmuscle Actin Isoforms*

PubMed Central

Bergeron, Sarah E.; Zhu, Mei; Thiem, Suzanne M.; Friderici, Karen H.; Rubenstein, Peter A.

2010-01-01

β- and γ-nonmuscle actins differ by 4 amino acids at or near the N terminus and distant from polymerization interfaces. β-Actin contains an Asp1-Asp2-Asp3 and Val10 whereas γ-actin has a Glu1-Glu2-Glu3 and Ile10. Despite these small changes, conserved across mammals, fish, and birds, their differential localization in the same cell suggests they may play different roles reflecting differences in their biochemical properties. To test this hypothesis, we established a baculovirus-driven expression system for producing these actins in isoform-pure populations although contaminated with 20–25% insect actin. Surprisingly, Ca-γ-actin exhibits a slower monomeric nucleotide exchange rate, a much longer nucleation phase, and a somewhat slower elongation rate than β-actin. In the Mg-form, this difference between the two is much smaller. Ca-γ-actin depolymerizes half as fast as does β-actin. Mixing experiments with Ca-actins reveal the two will readily co-polymerize. In the Ca-form, phosphate release from polymerizing β-actin occurs much more rapidly and extensively than polymerization, whereas phosphate release lags behind polymerization with γ-actin. Phosphate release during treadmilling is twice as fast with β- as with γ-actin. With Mg-actin in the initial stages, phosphate release for both actins correlates much more closely with polymerization. Calcium bound in the high affinity binding site of γ-actin may cause a selective energy barrier relative to β-actin that retards the equilibration between G- and F-monomer conformations resulting in a slower polymerizing actin with greater filament stability. This difference may be particularly important in sites such as the γ-actin-rich cochlear hair cell stereocilium where local mm calcium concentrations may exist. PMID:20308063

Stabilization of miniemulsion droplets by cerium oxide nanoparticles: a step toward the elaboration of armored composite latexes.

PubMed

Zgheib, Nancy; Putaux, Jean-Luc; Thill, Antoine; D'Agosto, Franck; Lansalot, Muriel; Bourgeat-Lami, Elodie

2012-04-10

Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step. Cryo-transmission electron microscopy (TEM) images of the suspensions formed with 35 wt % of CeO(2) showed the presence of polydisperse 50-150 nm spherical droplets. More surprisingly, some nonspherical (likely discoidal) objects that could be the result of the sonication step were also observed. The subsequent polymerization of these Pickering miniemulsion droplets led to the formation of composite PMMA latex particles armored with CeO(2). In all cases, the conversion was limited to ca. 85%, concomitant with a loss of stability of the latex for CeO(2) contents lower than 35 wt %. This stability issues were likely related to the screening of the cationic charges present on CeO(2) nanoparticles upon polymerization. TEM images showed mostly spherical particles with a diameter ranging from 100 to 400 nm and homogeneously covered with CeO(2). Besides, for particles typically larger than 200 nm, a buckled morphology was observed supporting the presence of residual monomer at the end of the polymerization and consistent with the limited conversion. The versatility of these systems was further demonstrated using 35 wt % of CeO(2) and replacing MMA by n-butyl acrylate (BA) either alone or in combination with MMA. Stable monomer emulsions were always obtained, with the droplet size increasing with the hydrophobicity of the oil phase, pointing out the key influence of the wettability of the solid stabilizer. The polymerization of Pickering miniemulsion stabilized by CeO(2) nanoparticles proved to be an efficient strategy to form armored composite latex particles which may find applications in coating technology. © 2012 American Chemical Society

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

Scherzberg, Maria-Christina; Kiehl, Andreas; Zivkovic, Aleksandra

(Z)-3,5,4′-Trimethoxystilbene (Z-TMS) is a resveratrol analog with increased antiproliferative activity towards a number of cancer cell lines compared to resveratrol, which has been shown to inhibit tubulin polymerization in vitro. The purpose of this study was to investigate if Z-TMS still shows potential for the prevention of metabolic diseases as known for resveratrol. Cell growth inhibition was determined with IC{sub 50} values for Z-TMS between 0.115 μM and 0.473 μM (resveratrol: 110.7 μM to 190.2 μM). Flow cytometric analysis revealed a G{sub 2}/M arrest after Z-TMS treatment, whereas resveratrol caused S phase arrest. Furthermore, Z-TMS was shown to impair microtubulemore » polymerization. Beneficial effects on lipid accumulation were observed for resveratrol, but not for Z-TMS in an in vitro steatosis model. (E)-Resveratrol was confirmed to elevate cAMP levels, and knockdown of AMPK attenuated the antiproliferative activity, while Z-TMS did not show significant effects in these experiments. SIRT1 and AMPK activities were further measured indirectly via induction of the target gene small heterodimer partner (SHP). Thereby, (E)-resveratrol, but not Z-TMS, showed potent induction of SHP mRNA levels in an AMPK- and SIRT1-dependent manner, as confirmed by knockdown experiments. We provide evidence that Z-TMS does not show beneficial metabolic effects, probably due to loss of activity towards resveratrol target genes. Moreover, our data support previous findings that Z-TMS acts as an inhibitor of tubulin polymerization. These findings confirm that the methylation of resveratrol leads to profound changes in the mode of action, which should be taken into consideration when conducting lead structure optimization approaches. - Highlights: • Methylation of resveratrol leads to profound changes in biologic activity. • Z-TMS does not prevent hepatic steatosis, but inhibits tubulin polymerization. • Resveratrol analog Z-TMS does not influence known targets like PDEs, SIRT1, or AMPK. • Resveratrol, but not Z-TMS, potently induces SHP mRNA dependent on AMPK and SIRT1.« less

Method of making soluble polyacetylenic and polyaromatic polymers

DOEpatents

Aldissi, Mahmoud; Liepins, Raimond

1985-01-01

A soluble polyene polymer and a method of making the same are disclosed. The polymer is of the class suitable for doping to produce an electrically conductive polymer. The method is generally applicable to acetylenic and aromatic monomers, proven examples of which include acetylene, benzene, anthracene and napthalene. In accordance with the method, the monomer is dissolved in arsenic trifluoride. Arsenic pentafluoride is then introduced into the solution to induce polymerization by what is speculated to be an ionic polymerization reaction. The resulting polymer differs from other polyene polymers in that it is soluble in common organic solvents, and further in that it can be melted without undergoing decomposition, thereby rendering it particularly suitable for processing to form various polymeric articles.

Soluble polyacetylenic and polyaromatic polymers and method of mking the same

DOEpatents

Aldissi, M.; Liepins, R.

1983-12-16

A soluble polyene polymer and a method of making the same are disclosed. The polymer is of the class suitable for doping to produce an electrically conductive polymer. The method is generally applicable to acetylenic and aromatic monomers, proven examples of which include acetylene, benzene, anthracene and napthalene. In accordance with the method, the monomer is dissolved in arsenic trifluoride. Arsenic pentafluoride is then introduced into the solution to induce polymerization by what is speculated to be an ionic polymerization reaction. The resulting polymer differs from other polyene polymers in that it is soluble in common organic solvents, and further in that it can be melted without undergoing decomposition, thereby rendering it particularly suitable for processing to form various polymeric articles.

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

Li, Hongfei; Yang, Zhenhua; Pan, Cheng

Here, we report that the addition of a non-photoactive tertiary polymer phase in the binary bulk heterojunction (BHJ) polymer solar cell leads to a self-assembled columnar nanostructure, enhancing the charge mobilities and photovoltaic efficiency with surprisingly increased optimal active blend thicknesses over 300 nm, 3–4 times larger than that of the binary counterpart. Using the prototypical poly(3-hexylthiophene) (P3HT):fullerene blend as a model BHJ system, we discover that the inert poly(methyl methacrylate) (PMMA) added in the binary BHJ blend self-assembles into vertical columns, which not only template the phase segregation of electron acceptor fullerenes but also induce the out-of-plane rotation ofmore » the edge-on-orientated crystalline P3HT phase. Using complementary interrogation methods including neutron reflectivity, X-ray scattering, atomic force microscopy, transmission electron microscopy, and molecular dynamics simulations, we show that the enhanced charge transport originates from the more randomized molecular stacking of the P3HT phase and the spontaneous segregation of fullerenes at the P3HT/PMMA interface, driven by the high surface tension between the two polymeric components. The results demonstrate a potential method for increasing the thicknesses of high-performance polymer BHJ solar cells with improved photovoltaic efficiency, alleviating the burden of stringently controlling the ultrathin blend thickness during the roll-to-roll-type large-area manufacturing environment.« less

Template-assisted mineral formation via an amorphous liquid phase precursor route

NASA Astrophysics Data System (ADS)

Amos, Fairland F.

The search for alternative routes to synthesize inorganic materials has led to the biomimetic route of producing ceramics. In this method, materials are manufactured at ambient temperatures and in aqueous solutions with soluble additives and insoluble matrix, similar to the biological strategy for the formation of minerals by living organisms. Using this approach, an anionic polypeptide additive was used to induce an amorphous liquid-phase precursor to either calcium carbonate or calcium phosphate. This precursor was then templated on either organic or inorganic substrates. Non-equilibrium morphologies, such as two-dimensional calcium carbonate films, one-dimensional calcium carbonate mesostructures and "molten" calcium phosphate spherulites were produced, which are not typical of the traditional (additive-free) solution grown crystals in the laboratory. In the study of calcium carbonate, the amorphous calcium carbonate mineral formed via the liquid-phase precursor, either underwent a dissolution-recrystallization event or a pseudo-solid-state transformation to produce different morphologies and polymorphs of the mineral. Discrete or aggregate calcite crystals were formed via the dissolution of the amorphous phase to allow the reprecipitation of the stable crystal. Non-equilibrium morphologies, e.g., films, mesotubules and mesowires were templated using organic and inorganic substrates and compartments. These structures were generated via an amorphous solid to crystalline solid transformation. Single crystalline tablets and mesowires of aragonite, which are reported to be found only in nature as skeletal structures of marine organisms, such as mollusk nacre and echinoderm teeth, were successfully synthesized. These biomimetic structures were grown via the polymer-induced liquid-phase precursor route in the presence of magnesium. Only low magnesium-bearing calcite was formed in the absence of the polymer. A similar approach of using a polymeric additive was implemented in calcium phosphate. Spherulitic crystals and films, seemingly formed from a molten state, were produced. These structures served as nucleating surfaces for the radial formation of calcium oxalate minerals. The composite calcium phosphate-calcium oxalate assemblies are similar to the core-shell structures found in certain kidney stones.

Advances in stir bar sorptive extraction for the determination of acidic pharmaceuticals in environmental water matrices Comparison between polyurethane and polydimethylsiloxane polymeric phases.

PubMed

Silva, Ana Rita M; Portugal, Fátima C M; Nogueira, J M F

2008-10-31

Stir bar sorptive extraction with polyurethane (PU) and polydimethylsiloxane (PDMS) polymeric phases followed by high-performance liquid chromatography with diode array detection [SBSE(PU or PDMS)/HPLC-DAD] was studied for the determination of six acidic pharmaceuticals [o-acetylsalicylic acid (ACA), ibuprofen (IBU), diclofenac sodium (DIC), naproxen (NAP), mefenamic acid (MEF) and gemfibrozil (GEM)], selected as non-steroidal acidic anti-inflammatory drugs and lipid regulators model compounds in environmental water matrices. The main parameters affecting the efficiency of the proposed methodology are fully discussed. Assays performed on 25 mL of water samples spiked at the 10 microg L(-1) level under optimized experimental conditions, yielded recoveries ranging from 45.3+/-9.0% (ACA) to 90.6+/-7.2% (IBU) by SBSE(PU) and 9.8+/-1.6% (NAP) to 73.4+/-5.0% (GEM) by SBSE(PDMS), where the former polymeric phase presented a better affinity to extract these target analytes from water matrices at the trace level. The methodology showed also excellent linear dynamic ranges for the six acidic pharmaceuticals studied, with correlation coefficients higher than 0.9976, limits of detection and quantification between 0.40-1.7 microg L(-1) and 1.5-5.8 microg L(-1), respectively, and suitable precision (RSD <15%). Moreover, the developed methodology was applied for the determination of these target analytes in several environmental matrices, including river, sea and wastewater samples, having achieved good performance and moderate matrix effects. In short, the PU foams demonstrated to be an excellent alternative for the enrichment of the more polar metabolites from water matrices by SBSE, overcoming the limitations of the conventional PDMS phase.

Preparation and characterization of Phase change material microcapsules by a core-shell-like emulsion polymerization method

NASA Astrophysics Data System (ADS)

Ding, Li-ming; Pei, Guang-ling

2015-07-01

Phase change material microcapsules (MicroPCMs) were synthesized by a coreshell-like emulsion polymerization method. Styrene and methylacrylic acid copolymer (PS- MAA) was used as a wall material, and paraffin was used as a core material in order to prepare spherical, high resistance and high enthalpy MicroPCMs. Scanning Electron Microscope (SEM), laser particle size analyzer, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) and Differential Scanning Calorimeter (DSC) were employed to characterize the MicroPCMs. The results indicated that the average particle size of MicroPCMs was 42.29 μm, and the content of paraffin within microcapsules was 57.6%. The melting temperature and crystallization temperature were 30.7°C and 25.2°C.The melting enthalpy and crystallization enthalpy were -84.1 J/g and 91.3 J/g, respectively.

Silane and germane plasma diagnostics for depositing photosensitive a-SiGe:H films

NASA Technical Reports Server (NTRS)

Shing, Y. H.; Perry, J. W.; Allevato, C. E.

1988-01-01

Highly photosensitive a-SiGe:H films with a light-to-dark conductivity ratio of 8 x 103 and an optical bandgap of 1.40 eV have been produced by RF glow discharge using hydrogen dilution of SiH4 and GeH4 mixed gas plasma. The critical role of hydrogen dilution in GeH4 containing plasmas is to suppress the gas-phase polymerization and promote the incorporation of Ge into the film. It is observed that inelastic laser light scattering of the RF plasma is a sensitive method for monitoring the onset of the gas-phase polymerization. In situ coherent anti-Stokes Raman spectroscopy measurements have shown that the dissociation rate of GeH4 is a factor of three larger than that of SiH4.

A High-Performance Recycling Solution for Polystyrene Achieved by the Synthesis of Renewable Poly(thioether) Networks Derived from d-Limonene

PubMed Central

Nash, Landon D.; Rodriguez, Jennifer N.; Lonnecker, Alexander T.; Raymond, Jeffery E.; Wilson, Thomas S.; Wooley, Karen L.; Maitland, Duncan J.

2014-01-01

Nanocomposite polymers have been prepared using a new sustainable materials synthesis process in which d-Limonene functions simultaneously both as a solvent for recycling polystyrene (PS) waste and as a monomer that undergoes UV-catalyzed thiol-ene polymerization reactions with polythiol co-monomers to afford polymeric products comprised of precipitated PS phases dispersed throughout elastomeric poly(thioether) networks. These blended networks exhibit mechanical properties that greatly exceed those of either polystyrene or the poly(thioether) network homopolymers alone. PMID:24249666

Laminated structures and methods and compositions for producing same

DOEpatents

Fumei, Giancarlo J.; Karabedian, James A.

1977-04-05

Methods for bonding two substrates, one of which is polymeric, which comprise coating the surface of at least one substrate with an adhesive composition comprising a major component which is an adhesive for the first substrate and a minor disperse phase which is a solution of a polymer in a solvent for the polymeric substrate and contacting the coated surface of the one substrate with the surface of the other substrate, together with adhesive compositions useful for joining such substrates, laminates so formed, and articles comprised of such laminates.

Light driven mesoscale assembly of a coordination polymeric gelator into flowers and stars with distinct properties.

PubMed

Mukhopadhyay, Rahul Dev; Praveen, Vakayil K; Hazra, Arpan; Maji, Tapas Kumar; Ajayaghosh, Ayyappanpillai

2015-11-13

Control over the self-assembly process of porous organic-inorganic hybrids often leads to unprecedented polymorphism and properties. Herein we demonstrate how light can be a powerful tool to intervene in the kinetically controlled mesoscale self-assembly of a coordination polymeric gelator. Ultraviolet light induced coordination modulation via photoisomerisation of an azobenzene based dicarboxylate linker followed by aggregation mediated crystal growth resulted in two distinct morphological forms (flowers and stars), which show subtle differences in their physical properties.

Nano-interconnection for microelectronics and polymers with benzo-triazole

NASA Technical Reports Server (NTRS)

Park, Yeonjoon; Choi, Sang H.; Noh, Hyunpil; Kuk, Young

2006-01-01

Benzo-Triazole (BTA) is considered as an important bridging material that can connect an organic polymer to the metal electrode on silicon wafers as a part of the microelectronics fabrication technology. We report a detailed process of surface induced 3-D polymerization of BTA on the Cu electrode material which was measured with the Ultraviolet Photoemission Spectroscopy (UPS), X-ray Photoemission Spectroscopy (XPS), and Scanning Tunneling Microscope (STM). The electric utilization of shield and chain polymerization of BTA on Cu surface is contemplated in this study.

Calreticulin attenuated microwave radiation-induced human microvascular endothelial cell injury through promoting actin acetylation and polymerization.

PubMed

Xu, Feifei; Wang, You; Tao, Tianqi; Song, Dandan; Liu, Xiuhua

2017-01-01

Recent work reveals that actin acetylation modification has been linked to different normal and disease processes and the effects associated with metabolic and environmental stressors. Herein, we highlight the effects of calreticulin on actin acetylation and cell injury induced by microwave radiation in human microvascular endothelial cell (HMEC). HMEC injury was induced by high-power microwave of different power density (10, 30, 60, 100 mW/cm 2 , for 6 min) with or without exogenous recombinant calreticulin. The cell injury was assessed by lactate dehydrogenase (LDH) activity and Cell Counting Kit-8 in culture medium, migration ability, intercellular junction, and cytoskeleton staining in HMEC. Western blotting analysis was used to detected calreticulin expression in cytosol and nucleus and acetylation of globular actin (G-actin). We found that HMEC injury was induced by microwave radiation in a dose-dependent manner. Pretreatment HMEC with calreticulin suppressed microwave radiation-induced LDH leakage and increased cell viability and improved microwave radiation-induced decrease in migration, intercellular junction, and cytoskeleton. Meanwhile, pretreatment HMEC with exogenous calreticulin upregulated the histone acetyltransferase activity and the acetylation level of G-actin and increased the fibrous actin (F-actin)/G-actin ratio. We conclude that exogenous calreticulin protects HMEC against microwave radiation-induced injury through promoting actin acetylation and polymerization.

Electronic structure of carbon dioxide under pressure and insights into the molecular-to-nonmolecular transition

PubMed Central

Shieh, Sean R.; Jarrige, Ignace; Wu, Min; Hiraoka, Nozomu; Tse, John S.; Mi, Zhongying; Kaci, Linada; Jiang, Jian-Zhong; Cai, Yong Q.

2013-01-01

Knowledge of the high-pressure behavior of carbon dioxide (CO2), an important planetary material found in Venus, Earth, and Mars, is vital to the study of the evolution and dynamics of the planetary interiors as well as to the fundamental understanding of the C–O bonding and interaction between the molecules. Recent studies have revealed a number of crystalline polymorphs (CO2-I to -VII) and an amorphous phase under high pressure–temperature conditions. Nevertheless, the reported phase stability field and transition pressures at room temperature are poorly defined, especially for the amorphous phase. Here we shed light on the successive pressure-induced local structural changes and the molecular-to-nonmolecular transition of CO2 at room temperature by performing an in situ study of the local electronic structure using X-ray Raman scattering, aided by first-principle exciton calculations. We show that the transition from CO2-I to CO2-III was initiated at around 7.4 GPa, and completed at about 17 GPa. The present study also shows that at ∼37 GPa, molecular CO2 starts to polymerize to an extended structure with fourfold coordinated carbon and minor CO3 and CO-like species. The observed pressure is more than 10 GPa below previously reported. The disappearance of the minority species at 63(±3) GPa suggests that a previously unknown phase transition within the nonmolecular phase of CO2 has occurred. PMID:24167283

A new strategy to engineer polymer bulk heterojunction solar cells with thick active layers via self-assembly of the tertiary columnar phase

DOE PAGES

Li, Hongfei; Yang, Zhenhua; Pan, Cheng; ...

2017-07-14

Here, we report that the addition of a non-photoactive tertiary polymer phase in the binary bulk heterojunction (BHJ) polymer solar cell leads to a self-assembled columnar nanostructure, enhancing the charge mobilities and photovoltaic efficiency with surprisingly increased optimal active blend thicknesses over 300 nm, 3–4 times larger than that of the binary counterpart. Using the prototypical poly(3-hexylthiophene) (P3HT):fullerene blend as a model BHJ system, we discover that the inert poly(methyl methacrylate) (PMMA) added in the binary BHJ blend self-assembles into vertical columns, which not only template the phase segregation of electron acceptor fullerenes but also induce the out-of-plane rotation ofmore » the edge-on-orientated crystalline P3HT phase. Using complementary interrogation methods including neutron reflectivity, X-ray scattering, atomic force microscopy, transmission electron microscopy, and molecular dynamics simulations, we show that the enhanced charge transport originates from the more randomized molecular stacking of the P3HT phase and the spontaneous segregation of fullerenes at the P3HT/PMMA interface, driven by the high surface tension between the two polymeric components. The results demonstrate a potential method for increasing the thicknesses of high-performance polymer BHJ solar cells with improved photovoltaic efficiency, alleviating the burden of stringently controlling the ultrathin blend thickness during the roll-to-roll-type large-area manufacturing environment.« less

Influence of Solutocapillary Convection on Macrovoid Defect Formation in Polymeric Membranes

NASA Technical Reports Server (NTRS)

Greenberg, Alan R.; Krantz, William B.; Todd, Paul

2003-01-01

The focus of this research project involved the dry-cast process for polymeric membrane formation, whereby evaporation of solvent from an initially homogeneous polymer/solvent/ nonsolvent solution results in phase separation and the formation of polymer-rich and polymer-lean phases. Under certain conditions the polymer-lean phase gives rise to very large and usually undesirable, tear-drop-shaped pores (size approx. 10 - 50 microns) termed macrovoids (MVs). Although in many cases the presence of MV pores has deleterious effects on membrane performance, there are a number of innovative applications where the presence of such pores is highly desirable. Although researchers have proposed a variety of mechanisms for MV formation over the past three decades, two main hypotheses are currently favored: one asserts that MV growth can be attributed solely to diffusion (the diffusive growth hypothesis), whereas the other states that solutocapillary convection (the SC hypothesis) at the MV interface contributes to growth. The overall goal of this research was to obtain a more comprehensive understanding of the fundamental mechanism of MV growth. This research incorporates a coupled modeling and experimental approach to test a solutocapillary convection hypothesis for the growth of macrovoid pores in polymeric membranes. Specifically, we utilized a modification of the first principles model developed by two of the PIs (ARG and WBK) for dry-cast CA membranes. For the experimental component, two separate and mutually complementary approaches were used to study MV growth. In the first, membranes cast in a zero-g environment aboard the NASA KC-135 aircraft were compared with those cast on the ground to assess the effect of the buoyancy force on membrane morphology and MV size and shape. In the second approach, videomicroscopy flow visualization (VMFV) was utilized to observe MV formation and growth in real time and to assess the effect of surface tension on the MV growth dynamics. As a result of these fundamental studies, our research group advanced a new hypothesis for MV pore development in polymeric membranes.

Effects of polymerization and nucleotide identity on the conformational dynamics of the bacterial actin homolog MreB

PubMed Central

Colavin, Alexandre; Hsin, Jen; Huang, Kerwyn Casey

2014-01-01

The assembly of protein filaments drives many cellular processes, from nucleoid segregation, growth, and division in single cells to muscle contraction in animals. In eukaryotes, shape and motility are regulated through cycles of polymerization and depolymerization of actin cytoskeletal networks. In bacteria, the actin homolog MreB forms filaments that coordinate the cell-wall synthesis machinery to regulate rod-shaped growth and contribute to cellular stiffness through unknown mechanisms. Like actin, MreB is an ATPase and requires ATP to polymerize, and polymerization promotes nucleotide hydrolysis. However, it is unclear whether other similarities exist between MreB and actin because the two proteins share low sequence identity and have distinct cellular roles. Here, we use all-atom molecular dynamics simulations to reveal surprising parallels between MreB and actin structural dynamics. We observe that MreB exhibits actin-like polymerization-dependent structural changes, wherein polymerization induces flattening of MreB subunits, which restructures the nucleotide-binding pocket to favor hydrolysis. MreB filaments exhibited nucleotide-dependent intersubunit bending, with hydrolyzed polymers favoring a straighter conformation. We use steered simulations to demonstrate a coupling between intersubunit bending and the degree of flattening of each subunit, suggesting cooperative bending along a filament. Taken together, our results provide molecular-scale insight into the diversity of structural states of MreB and the relationships among polymerization, hydrolysis, and filament properties, which may be applicable to other members of the broad actin family. PMID:24550504

Effects of polymerization and nucleotide identity on the conformational dynamics of the bacterial actin homolog MreB.

PubMed

Colavin, Alexandre; Hsin, Jen; Huang, Kerwyn Casey

2014-03-04

The assembly of protein filaments drives many cellular processes, from nucleoid segregation, growth, and division in single cells to muscle contraction in animals. In eukaryotes, shape and motility are regulated through cycles of polymerization and depolymerization of actin cytoskeletal networks. In bacteria, the actin homolog MreB forms filaments that coordinate the cell-wall synthesis machinery to regulate rod-shaped growth and contribute to cellular stiffness through unknown mechanisms. Like actin, MreB is an ATPase and requires ATP to polymerize, and polymerization promotes nucleotide hydrolysis. However, it is unclear whether other similarities exist between MreB and actin because the two proteins share low sequence identity and have distinct cellular roles. Here, we use all-atom molecular dynamics simulations to reveal surprising parallels between MreB and actin structural dynamics. We observe that MreB exhibits actin-like polymerization-dependent structural changes, wherein polymerization induces flattening of MreB subunits, which restructures the nucleotide-binding pocket to favor hydrolysis. MreB filaments exhibited nucleotide-dependent intersubunit bending, with hydrolyzed polymers favoring a straighter conformation. We use steered simulations to demonstrate a coupling between intersubunit bending and the degree of flattening of each subunit, suggesting cooperative bending along a filament. Taken together, our results provide molecular-scale insight into the diversity of structural states of MreB and the relationships among polymerization, hydrolysis, and filament properties, which may be applicable to other members of the broad actin family.

Mapping Polymerization and Allostery of Hemoglobin S Using Point Mutations

PubMed Central

Weinkam, Patrick; Sali, Andrej

2014-01-01

Hemoglobin is a complex system that undergoes conformational changes in response to oxygen, allosteric effectors, mutations, and environmental changes. Here, we study allostery and polymerization of hemoglobin and its variants by application of two previously described methods: (i) AllosMod for simulating allostery dynamics given two allosterically related input structures and (ii) a machine-learning method for dynamics- and structure-based prediction of the mutation impact on allostery (Weinkam et al. J. Mol. Biol. 2013), now applicable to systems with multiple coupled binding sites such as hemoglobin. First, we predict the relative stabilities of substates and microstates of hemoglobin, which are determined primarily by entropy within our model. Next, we predict the impact of 866 annotated mutations on hemoglobin’s oxygen binding equilibrium. We then discuss a subset of 30 mutations that occur in the presence of the sickle cell mutation and whose effects on polymerization have been measured. Seven of these HbS mutations occur in three predicted druggable binding pockets that might be exploited to directly inhibit polymerization; one of these binding pockets is not apparent in the crystal structure but only in structures generated by AllosMod. For the 30 mutations, we predict that mutation-induced conformational changes within a single tetramer tend not to significantly impact polymerization; instead, these mutations more likely impact polymerization by directly perturbing a polymerization interface. Finally, our analysis of allostery allows us to hypothesize why hemoglobin evolved to have multiple subunits and a persistent low frequency sickle cell mutation. PMID:23957820

Nano-sized Soluplus® polymeric micelles enhance the induction of tetanus toxin neutralising antibody response following transcutaneous immunisation with tetanus toxoid.

PubMed

Saydam, Manolya; Cheng, Woei Ping; Palmer, Nathan; Tierney, Robert; Francis, Robert; MacLellan-Gibson, Kirsty; Khan, Ambreen; Mawas, Fatme

2017-04-25

The use of Soluplus® polymeric micelles as a novel adjuvant for tetanus toxoid (TTxd) in transcutaneous immunisation was evaluated. TTxd was added to Soluplus® polymeric micelles to form TTxd-Soluplus® nano-aggregates with a size of 68nm. Non-adjuvanted TTxd commonly induces very poor antibody response by the transcutaneous route. However, in this study, the use of TTxd-Soluplus® resulted in a significant increase in the antibody response to TTxd, which was similar to that induced in the presence of CPG-oligodeoxynucleotides (CPG-ODNs) adjuvant. The toxin neutralising potency of the immune sera induced by TTxd-Soluplus® was also much stronger than that from TTxd alone, in a passive transfer experiment in mice. Soluplus® also enhanced the immunogenicity of the toxoid when TTxd-Soluplus® was stored at 4°C for 4weeks, but not at higher temperatures. Confocal microscopy imaging showed a much higher uptake of TTxd in the epidermis and dermis layers of the skin when it was associated with Soluplus®, suggesting that the mechanism for Soluplus® adjuvanticity is through enhanced uptake of the TTxd through the skin. Overall, our findings demonstrated that Soluplus® is an effective novel adjuvant for transcutaneous immunisation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Probing GFP-actin diffusion in living cells using fluorescence correlation spectroscopy.

PubMed

Engelke, Hanna; Heinrich, Doris; Rädler, Joachim O

2010-12-22

The cytoskeleton of eukaryotic cells is continuously remodeled by polymerization and depolymerization of actin. Consequently, the relative content of polymerized filamentous actin (F-actin) and monomeric globular actin (G-actin) is subject to temporal and spatial fluctuations. Since fluorescence correlation spectroscopy (FCS) can measure the diffusion of fluorescently labeled actin it seems likely that FCS allows us to determine the dynamics and hence indirectly the structural properties of the cytoskeleton components with high spatial resolution. To this end we investigate the FCS signal of GFP-actin in living Dictyostelium discoideum cells and explore the inherent spatial and temporal signatures of the actin cytoskeleton. Using the free green fluorescent protein (GFP) as a reference, we find that actin diffusion inside cells is dominated by G-actin and slower than diffusion in diluted cell extract. The FCS signal in the dense cortical F-actin network near the cell membrane is probed using the cytoskeleton protein LIM and is found to be slower than cytosolic G-actin diffusion. Furthermore, we show that polymerization of the cytoskeleton induced by Jasplakinolide leads to a substantial decrease of G-actin diffusion. Pronounced fluctuations in the distribution of the FCS correlation curves can be induced by latrunculin, which is known to induce actin waves. Our work suggests that the FCS signal of GFP-actin in combination with scanning or spatial correlation techniques yield valuable information about the local dynamics and concomitant cytoskeletal properties.

Synthesis, Structure, and Pressure-Induced Polymerization of Li3Fe(CN)6 Accompanied with Enhanced Conductivity.

PubMed

Li, Kuo; Zheng, Haiyan; Hattori, Takanori; Sano-Furukawa, Asami; Tulk, Christopher A; Molaison, Jamie; Feygenson, Mikhail; Ivanov, Ilia N; Yang, Wenge; Mao, Ho-Kwang

2015-12-07

Pressure-induced polymerization of charged triple-bond monomers like acetylide and cyanide could lead to formation of a conductive metal-carbon network composite, thus providing a new route to synthesize inorganic/organic conductors with tunable composition and properties. The industry application of this promising synthetic method is mainly limited by the reaction pressure needed, which is often too high to be reached for gram amounts of sample. Here we successfully synthesized highly conductive Li3Fe(CN)6 at maximum pressure around 5 GPa and used in situ diagnostic tools to follow the structural and functional transformations of the sample, including in situ X-ray and neutron diffraction and Raman and impedance spectroscopy, along with the neutron pair distribution function measurement on the recovered sample. The cyanide anions start to react around 1 GPa and bond to each other irreversibly at around 5 GPa, which are the lowest reaction pressures in all known metal cyanides and within the technologically achievable pressure range for industrial production. The conductivity of the polymer is above 10(-3) S · cm(-1), which reaches the range of conductive polymers. This investigation suggests that the pressure-induced polymerization route is practicable for synthesizing some types of functional conductive materials for industrial use, and further research like doping and heating can hence be motivated to synthesize novel materials under lower pressure and with better performances.

Development of Photocrosslinkable Urethane-Doped Polyester Elastomers for Soft Tissue Engineering

PubMed Central

Zhang, Yi; Tran, Richard T.; Gyawali, Dipendra; Yang, Jian

2012-01-01

Finding an ideal biomaterial with the proper mechanical properties and biocompatibility has been of intense focus in the field of soft tissue engineering. This paper reports on the synthesis and characterization of a novel crosslinked urethane-doped polyester elastomer (CUPOMC), which was synthesized by reacting a previously developed photocrosslinkable poly (octamethylene maleate citrate) (POMC) prepolymers (pre-POMC) with 1,6-hexamethylene diisocyanate (HDI) followed by thermo- or photo-crosslinking polymerization. The mechanical properties of the CUPOMCs can be tuned by controlling the molar ratios of pre-POMC monomers, and the ratio between the prepolymer and HDI. CUPOMCs can be crosslinked into a 3D network through polycondensation or free radical polymerization reactions. The tensile strength and elongation at break of CUPOMC synthesized under the known conditions range from 0.73±0.12MPa to 10.91±0.64MPa and from 72.91±9.09% to 300.41±21.99% respectively. Preliminary biocompatibility tests demonstrated that CUPOMCs support cell adhesion and proliferation. Unlike the pre-polymers of other crosslinked elastomers, CUPOMC pre-polymers possess great processability demonstrated by scaffold fabrication via a thermally induced phase separation method. The dual crosslinking methods for CUPOMC pre-polymers should enhance the versatile processability of the CUPOMC used in various conditions. Development of CUPOMC should expand the choices of available biodegradable elastomers for various biomedical applications such as soft tissue engineering. PMID:23565318

Polymer chain collapse induced by many-body dipole correlations.

PubMed

Budkov, Yu A; Kalikin, N N; Kolesnikov, A L

2017-04-01

We present a simple analytical theory of a flexible polymer chain dissolved in a good solvent, carrying permanent freely oriented dipoles on the monomers. We take into account the dipole correlations within the random phase approximation (RPA), as well as a dielectric heterogeneity in the internal polymer volume relative to the bulk solution. We demonstrate that the dipole correlations of monomers can be taken into account as pairwise ones only when the polymer chain is in a coil conformation. In this case the dipole correlations manifest themselves through the Keesom interactions of the permanent dipoles. On the other hand, the dielectric heterogeneity effect (dielectric mismatch effect) leads to the effective interaction between the monomers of the polymeric coil. Both of these effects can be taken into account by renormalizing the second virial coefficient of the monomer-monomer volume interactions. We establish that in the case when the solvent dielectric permittivity exceeds the dielectric permittivity of the polymeric material, the dielectric mismatch effect competes with the dipole attractive interactions, leading to polymer coil expansion. In the opposite case, both the dielectric mismatch effect and the dipole attractive interaction lead to the polymer coil collapse. We analyse the coil-globule transition caused by the dipole correlations of monomers within the many-body theory. We demonstrate that accounting for the dipole correlations higher than the pairwise ones smooths this pure electrostatics driven coil-globule transition of the polymer chain.

Automatic reactor for solid-phase synthesis of molecularly imprinted polymeric nanoparticles (MIP NPs) in water.

PubMed

Poma, Alessandro; Guerreiro, Antonio; Caygill, Sarah; Moczko, Ewa; Piletsky, Sergey

We report the development of an automated chemical reactor for solid-phase synthesis of MIP NPs in water. Operational parameters are under computer control, requiring minimal operator intervention. In this study, "ready for use" MIP NPs with sub-nanomolar affinity are prepared against pepsin A, trypsin and α-amylase in only 4 hours.

Automatic reactor for solid-phase synthesis of molecularly imprinted polymeric nanoparticles (MIP NPs) in water

PubMed Central

Poma, Alessandro; Guerreiro, Antonio; Caygill, Sarah; Moczko, Ewa; Piletsky, Sergey

2015-01-01

We report the development of an automated chemical reactor for solid-phase synthesis of MIP NPs in water. Operational parameters are under computer control, requiring minimal operator intervention. In this study, “ready for use” MIP NPs with sub-nanomolar affinity are prepared against pepsin A, trypsin and α-amylase in only 4 hours. PMID:26722622

A micro-reactor for preparing uniform molecularly imprinted polymer beads.

PubMed

Zourob, Mohammed; Mohr, Stephan; Mayes, Andrew G; Macaskill, Alexandra; Pérez-Moral, Natalia; Fielden, Peter R; Goddard, Nicholas J

2006-02-01

In this study, uniform spherical molecularly imprinted polymer beads were prepared via controlled suspension polymerization in a spiral-shaped microchannel using mineral oil and perfluorocarbon liquid as continuous phases. Monodisperse droplets containing the monomers, template, initiator, and porogenic solvent were introduced into the microchannel, and particles of uniform size were produced by subsequent UV polymerization, quickly and without wasting polymer materials. The droplet/particle size was varied by changing the flow conditions in the microfluidic device. The diameter of the resulting products typically had a coefficient of variation (CV) below 2%. The specific binding sites that were created during the imprinting process were analysed via radioligand binding analysis. The molecularly imprinted microspheres produced in the liquid perfluorocarbon continuous phase had a higher binding capacity compared with the particles produced in the mineral oil continuous phase, though it should be noted that the aim of this study was not to optimize or maximize imprinting performance, but rather to demonstrate broad applicability and compatibility with known MIP production methods. The successful imprinting against a model compound using two very different continuous phases (one requiring a surfactant to stabilize the droplets the other not) demonstrates the generality of this current simple approach.

Development and validation of a rapid reversed-phase HPLC method for the determination of the non-nucleoside reverse transcriptase inhibitor dapivirine from polymeric nanoparticles.

PubMed

das Neves, José; Sarmento, Bruno; Amiji, Mansoor M; Bahia, Maria Fernanda

2010-06-05

The objective of this work was to develop and validate a rapid reversed-phase (RP) high-performance liquid chromatography (HPLC) method for the in vitro pharmaceutical characterization of dapivirine-loaded polymeric nanoparticles. Chromatographic runs were performed on a RP C18 column with a mobile phase comprising acetonitrile-0.5% (w/v) triethanolamine solution in isocratic mode (80:20, v/v) at a flow rate of 1 ml/min. Dapivirine was detected at a wavelength of 290 nm. The method was shown to be specific, linear in the range of 1-50 microg/ml (R(2)=0.9998), precise at the intra-day and inter-day levels as reflected by the relative standard deviation values (less than 0.85%), accurate (recovery rate of 100.17+/-0.35%), and robust to changes in the mobile phase and column brand. The detection and quantitation limits were 0.08 and 0.24 microg/ml, respectively. The method was successfully used to determine the loading capacity and association efficiency of dapivirine in poly(lactic-co-glycolic acid)-based nanoparticles and its in vitro release. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Temperature-responsive chromatography for the separation of biomolecules.

PubMed

Kanazawa, Hideko; Okano, Teruo

2011-12-09

Temperature-responsive chromatography for the separation of biomolecules utilizing poly(N-isopropylacrylamide) (PNIPAAm) and its copolymer-modified stationary phase is performed with an aqueous mobile phase without using organic solvent. The surface properties and function of the stationary phase are controlled by external temperature changes without changing the mobile-phase composition. This analytical system is based on nonspecific adsorption by the reversible transition of a hydrophilic-hydrophobic PNIPAAm-grafted surface. The driving force for retention is hydrophobic interaction between the solute molecules and the hydrophobized polymer chains on the stationary phase surface. The separation of the biomolecules, such as nucleotides and proteins was achieved by a dual temperature- and pH-responsive chromatography system. The electrostatic and hydrophobic interactions could be modulated simultaneously with the temperature in an aqueous mobile phase, thus the separation system would have potential applications in the separation of biomolecules. Additionally, chromatographic matrices prepared by a surface-initiated atom transfer radical polymerization (ATRP) exhibit a strong interaction with analytes, because the polymerization procedure forms a densely packed polymer, called a polymer brush, on the surfaces. The copolymer brush grafted surfaces prepared by ATRP was an effective tool for separating basic biomolecules by modulating the electrostatic and hydrophobic interactions. Applications of thermally responsive columns for the separations of biomolecules are reviewed here. Copyright © 2011 Elsevier B.V. All rights reserved.

A Robust Oil-in-Oil Emulsion for the Nonaqueous Encapsulation of Hydrophilic Payloads.

PubMed

Lu, Xiaocun; Katz, Joshua S; Schmitt, Adam K; Moore, Jeffrey S

2018-03-14

Compartmentalized structures widely exist in cellular systems (organelles) and perform essential functions in smart composite materials (microcapsules, vasculatures, and micelles) to provide localized functionality and enhance materials' compatibility. An entirely water-free compartmentalization system is of significant value to the materials community as nonaqueous conditions are critical to packaging microcapsules with water-free hydrophilic payloads while avoiding energy-intensive drying steps. Few nonaqueous encapsulation techniques are known, especially when considering just the scalable processes that operate in batch mode. Herein, we report a robust oil-in-oil Pickering emulsion system that is compatible with nonaqueous interfacial reactions as required for encapsulation of hydrophilic payloads. A major conceptual advance of this work is the notion of the partitioning inhibitor-a chemical agent that greatly reduces the payload's distribution between the emulsion's two phases, thus providing appropriate conditions for emulsion-templated interfacial polymerization. As a specific example, an immiscible hydrocarbon-amine pair of liquids is emulsified by the incorporation of guanidinium chloride (GuHCl) as a partitioning inhibitor into the dispersed phase. Polyisobutylene (PIB) is added into the continuous phase as a viscosity modifier for suitable modification of interfacial polymerization kinetics. The combination of GuHCl and PIB is necessary to yield a robust emulsion with stable morphology for 3 weeks. Shell wall formation was accomplished by interfacial polymerization of isocyanates delivered through the continuous phase and polyamines from the droplet core. Diethylenetriamine (DETA)-loaded microcapsules were isolated in good yield, exhibiting high thermal and chemical stabilities with extended shelf-lives even when dispersed into a reactive epoxy resin. The polyamine phase is compatible with a variety of basic and hydrophilic actives, suggesting that this encapsulation technology is applicable to other hydrophilic payloads such as polyols, aromatic amines, and aromatic heterocyclic bases. Such payloads are important for the development of extended pot or shelf life systems and responsive coatings that report, protect, modify, and heal themselves without intervention.

A Novel Method of Measuring the Phase Behavior and Rheology of Polyethylene Solutions Using a Multi-Pass Rheometer

NASA Astrophysics Data System (ADS)

Lee, Karen; Lacombe, Y.; Cheluget, E.

2008-07-01

The Advanced SCLAIRTECH™ Technology process is used to manufacture Linear Low Density Polyethylene using solution polymerization. In this process ethylene is polymerized in an inert solvent, which is subsequently evaporated and recycled. The reactor effluent in the process is a polymer solution containing the polyethylene product, which is separated from the solvent and unconverted ethylene/co-monomer before being extruded and pelletized. The design of unit operations in this process requires a detailed understanding of the thermophysical properties, phase behaviour and rheology of polymer containing streams at high temperature and pressure, and over a wide range of composition. This paper describes a device used to thermo-rheologically characterize polymer solutions under conditions prevailing in polymerization reactors, downstream heat exchangers and attendant phase separation vessels. The downstream processing of the Advanced SCLAIRTECH™ Technology reactor effluent occurs at temperatures and pressures near the critical point of the solvent and co-monomer mixture. In addition, the process trajectory encompasses regions of liquid-liquid and liquid-liquid-vapour co-existence, which are demarcated by a `cloud point' curve. Knowing the location of this phase boundary is essential for the design of downstream devolatilization processes and for optimizing operating conditions in existing plants. In addition, accurate solution rheology data are required for reliable equipment sizing and design. At NOVA Chemicals, a robust high-temperature and high-pressure-capable version of the Multi-Pass Rheometer (MPR) is used to provide data on solution rheology and phase boundary location. This sophisticated piece of equipment is used to quantify the effects of solvent types, comonomer, and free ethylene concentration on the properties of the reactor effluent. An example of the experimental methodology to characterize a polyethylene solution with hexane solvent, and the ethylene dosing technique developed for the MPR will be described. ™Advanced SCLAIRTECH is a trademark of NOVA Chemicals.

Polymeric Coatings for Combating Biocorrosion

NASA Astrophysics Data System (ADS)

Guo, Jing; Yuan, Shaojun; Jiang, Wei; Lv, Li; Liang, Bin; Pehkonen, Simo O.

2018-03-01

Biocorrosion has been considered as big trouble in many industries and marine environments due to causing great economic loss. The main disadvantages of present approaches to prevent corrosion include being limited by environmental factors, being expensive, inapplicable to field, and sometimes inefficient. Studies show that polymer coatings with anti-corrosion and anti-microbial properties have been widely accepted as a novel and effective approach to preventbiocorrosion. The main purpose of this review is to summarize up the progressive status of polymer coatings used for combating microbially-induced corrosion. Polymers used to synthesize protective coatings are generally divided into three categories: i) traditional polymers incorporated with biocides, ii) antibacterial polymers containing quaternary ammonium compounds, and iii) conductive polymers. The strategies to synthesize polymer coatings resort mainly to grafting anti-bacterial polymers from the metal substrate surface using novel surface-functionalization approaches, such as free radical polymerization, chemically oxidative polymerization and surface-initiated atom transfer radical polymerization, as opposed to the traditional approaches of dip coating or spin coating.

Polymeric scaffolds as stem cell carriers in bone repair.

PubMed

Rossi, Filippo; Santoro, Marco; Perale, Giuseppe

2015-10-01

Although bone has a high potential to regenerate itself after damage and injury, the efficacious repair of large bone defects resulting from resection, trauma or non-union fractures still requires the implantation of bone grafts. Materials science, in conjunction with biotechnology, can satisfy these needs by developing artificial bones, synthetic substitutes and organ implants. In particular, recent advances in polymer science have provided several innovations, underlying the increasing importance of macromolecules in this field. To address the increasing need for improved bone substitutes, tissue engineering seeks to create synthetic, three-dimensional scaffolds made from polymeric materials, incorporating stem cells and growth factors, to induce new bone tissue formation. Polymeric materials have shown a great affinity for cell transplantation and differentiation and, moreover, their structure can be tuned in order to maintain an adequate mechanical resistance and contemporarily be fully bioresorbable. This review emphasizes recent progress in polymer science that allows relaible polymeric scaffolds to be synthesized for stem cell growth in bone regeneration. Copyright © 2013 John Wiley & Sons, Ltd.

Initiator and Photocatalyst-Free Visible Light Induced One-Pot Reaction: Concurrent RAFT Polymerization and CuAAC Click Reaction.

PubMed

Wang, Jie; Wang, Xinbo; Xue, Wentao; Chen, Gaojian; Zhang, Weidong; Zhu, Xiulin

2016-05-01

A new, visible light-catalyzed, one-pot and one-step reaction is successfully employed to design well-controlled side-chain functionalized polymers, by the combination of ambient temperature revisible addtion-fragmentation chain transfer (RAFT) polymerization and click chemistry. Polymerizations are well controlled in a living way under the irradiation of visible light-emitting diode (LED) light without photocatalyst and initiator, using the trithiocarbonate agent as iniferter (initiator-transfer agent-terminator) agent at ambient temperature. Fourier transfer infrared spectroscopy (FT-IR), NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) data confirm the successful one-pot reaction. Compared to the reported zero-valent metal-catalyzed one-pot reaction, the polymerization rate is much faster than that of the click reaction, and the visible light-catalyzed one-pot reaction can be freely and easily regulated by turning on and off the light. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cluster-mediated assembly enables step-growth copolymerization from binary nanoparticle mixtures with rationally designed architectures† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c8sc00220g

PubMed Central

Zhang, Xianfeng; Lv, Longfei; Wu, Guanhong; Yang, Dong

2018-01-01

Directed co-assembly of binary nanoparticles (NPs) into one-dimensional copolymer-like chains is fascinating but challenging in the realm of material science. While many strategies have been developed to induce the polymerization of NPs, it remains a grand challenge to produce colloidal copolymers with widely tailored compositions and precisely controlled architectures. Herein we report a robust colloidal polymerization strategy, which enables the growth of sophisticated NP chains with elaborately designed structures. By quantifying NP assembly statistics and kinetics, we establish that the linear assembly of colloidal NPs, with the assistance of PbSO4 clusters, follows a step-growth polymerization mechanism, and on the basis of this, we design and fabricate NP chains structurally analogous to random, block, and alternating copolymers, respectively. Our studies offer mechanistic insights into cluster-mediated colloidal polymerization, paving the way toward the rational synthesis of colloidal copolymers with quantitatively predicted architectures and functionalities. PMID:29862003