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Sample records for poly vinyl pyridines

  1. Phase Behavior of Block Copolymers containing Poly(vinyl pyridine) by Coordination with Metal Chloride

    NASA Astrophysics Data System (ADS)

    Lee, Dong Hyun; Kim, Hwang Yong; Kim, Jin Kon; Ryu, Du Yeol; Huh, June

    2007-03-01

    We studied, via small angle X-ray scattering, rheology, and transmission electron microscopy, the change of the domain spacing (D) and the order-to-disorder transition temperature (TODT) with the amount of cadmium chloride (CdCl2) for polystyrene-block-poly(2-vinyl pyridine) copolymers (PS-P2VP) and polystyrene-block-poly(4-vinyl pyridine) copolymers (PS-P4VP). With increasing amount of CdCl2, both D and TODT of PS-P2VP increased greatly. On the other hand, with increasing amount of CdCl2, D of PS-P4VP decreased, whereas TODT of PS-P4VP increased dramatically. These results are due to different types of the coordination between CdCl2 and nitrogen atoms in the 2-position of pyridine ring (intra-chain coordination) in PS-P2VP, compared with nitrogen atoms in the 4-position (inter-chain coordination) in PS-P4VP. This work was supported by Creative Research Initiative Program supported by KOSEF

  2. Phase Behavior of poly(2-vinyl pyridine)-block-poly(4-vinyl pridine) Copolymers

    NASA Astrophysics Data System (ADS)

    Han, Sung Hyun; Lee, Dong Hyun; Kim, Jin Kon

    2007-03-01

    Phase behavior of a block copolymer depends on the volume fraction (f) of one block, total degree of polymerization (N), and the segmental interaction parameter (χ). Recently, we found that the order-to-disorder transition temperature (TODT) of polystyrene-block-poly(2-vinylpridine) copolymer (PS-P2VP) was much lower than that of PS-block-poly(4-vinylpridine) copolymer (PS-P4VP) at similar values of f and N. The only difference between PS-P2VP and PS-P4VP is the different location of the nitrogen group in phenyl ring (2 versus 4-position). In this study, we studied, via small angle X-ray scattering (SAXS), rheometry, and birefringence, the phase behavior P2VP-block-P4VP copolymers (P2VP-P4VP) with various f and N. We determined the temperature dependence of χ between P2VP and P4VP from SAXS profiles in the disordered states with the aid of the random phase approximation. We found that the value of χ between P2VP and P4VP was relatively large. For instance, it is larger than χ between PS and P2VP. Thus, even when the molecular weight of symmetric P2VP-P4VP is ca. 12000, the TODT is larger than 280 ^oC. This work was supported by Creative Research Initiative Program supported by KOSEF

  3. Calorimetric evidence for a mobile surface layer in ultrathin polymeric films: poly(2-vinyl pyridine).

    PubMed

    Madkour, Sherif; Yin, Huajie; Füllbrandt, Marieke; Schönhals, Andreas

    2015-10-28

    Specific heat spectroscopy was used to study the dynamic glass transition of ultrathin poly(2-vinyl pyridine) films (thicknesses: 405-10 nm). The amplitude and the phase angle of the differential voltage were obtained as a measure of the complex heat capacity. In a traditional data analysis, the dynamic glass transition temperature Tg is estimated from the phase angle. These data showed no thickness dependency on Tg down to 22 nm (error of the measurement of ±3 K). A derivative-based method was established, evidencing a decrease in Tg with decreasing thickness up to 7 K, which can be explained by a surface layer. For ultrathin films, data showed broadening at the lower temperature side of the spectra, supporting the existence of a surface layer. Finally, temperature dependence of the heat capacity in the glassy and liquid states changes with film thickness, which can be considered as a confinement effect.

  4. Self-assembled structures of hydrogen-bonded poly(vinyl chloride-g-4-vinyl pyridine) graft copolymers

    NASA Astrophysics Data System (ADS)

    Koh, Joo Hwan; Seo, Jin Ah; Koh, Jong Kwan; Kim, Jong Hak

    2010-09-01

    An amphiphilic graft copolymer of poly(vinyl chloride-graft-4-vinyl pyridine), i.e., PVC-g-P4VP was synthesized via atom transfer radical polymerization (ATRP) and modified by introducing 1,5-dihydroxynaphthalene (DHN) as a hydrogen bonding donor to form hydrogen-bonded macromolecules. The PVC-g-P4VP graft copolymer prepared from a selective solvent for PVC, i.e., tetrahydrofuran (THF) exhibited a well-organized micellar morphology consisting of a P4VP core and a PVC corona. However, the graft copolymer prepared from a good solvent for both domains, i.e., N, N-dimethylformamide (DMF) showed a less-organized, random microphase-separated morphology. Upon the introduction of DHN, a more spherical morphology and a more-organized 'bicontinuous-like' morphology was observed in THF and DMF, respectively. This results from strong segregation between the two domains due to the enhanced interfacial energy by DHN. When DHN was removed by methanol, nanoporous films with versatile pore sizes and shapes were generated.

  5. Glassy dynamics of poly(2-vinyl-pyridine) brushes with varying grafting density.

    PubMed

    Neubauer, Nils; Winkler, René; Tress, Martin; Uhlmann, Petra; Reiche, Martin; Kipnusu, Wycliffe Kiprop; Kremer, Friedrich

    2015-04-21

    The molecular dynamics of poly(2-vinyl-pyridine) (P2VP) brushes is measured by Broadband Dielectric Spectroscopy (BDS) in a wide temperature (250 K to 440 K) and broad spectral (0.1 Hz to 1 MHz) range. This is realized using nanostructured, highly conductive silicon electrodes being separated by silica spacers as small as 35 nm. A "grafting-to"-method is applied to prepare the P2VP-brushes with five different grafting densities (0.030 nm(-2) to 0.117 nm(-2)), covering the "true-brush" regime with highly stretched coils and the "mushroom-to-brush" transition regime. The film thickness ranges between 1.8 to 7.1 (±0.2) nm. Two relaxations are observed, an Arrhenius-like process being attributed to fluctuations in the poly(glycidyl-methacrylate) (PGMA) linker used for the grafting reaction and the segmental dynamics (dynamic glass transition) of the P2VP brushes. The latter is characterized by a Vogel-Fulcher-Tammann dependence similar to bulk P2VP. The results can be comprehended considering the length scale on which the dynamic glass transition (≤1 nm) takes place.

  6. Dental Pulp Stem Cell Differentiation on Poly-4-vinyl-pyridine surfaces

    NASA Astrophysics Data System (ADS)

    Suarato, Giulia; Bherwani, Aneel; Chang, Chung-Chueh; Rafailovich, Miriam; Simon, Marcia

    2012-02-01

    In the regeneration of a natural tissue, the mechanics and the chemical properties of the artificial substrate play a critical role. In this study, the influence of poly-4-vinyl-pyridine scaffold morphology on dental pulp stem cell differentiation was analyzed. Cells were plated on spun cast films and electrospun fibers with diameters ranging from nano to micrometers. Confocal microscopy showed the presence of various cell morphologies: on microfibers cells conform precisely to the main axis of elongation, while on nanometric scaffolds they result spread and in contact with several fibers. Even if the surface chemistry was identical, a great variation in the curvature was present. From day 9 of incubation, spontaneous biomineralization in the absence of induction agents occurred only on the fibrous structures. The SEM revealed template deposits directly on the microfibers, while on the nanofibers large spherical islands were also present. EDAX determined hydroxyl apatite nature of the deposits. RT-PCR indicated upregulation of osteogenic markers, confirming differentiation. SEM also revealed the presence of ECM fibers covering the polymer structure, which may enhance the expression of focal adhesion sites on the cell membrane.

  7. Synthesis and characterization of poly(4-vinyl pyridine-co-styrene)/FHAP nanocomposite, and its biomedical application

    NASA Astrophysics Data System (ADS)

    Dhanalakshmi, C. P.; Vijayalakshmi, L.; Narayanan, V.

    2013-10-01

    Among the composite materials, ceramic/polymer possesses significant advantages of high mechanical reliability and excellent biocompatibility for applications in load-bearing areas. In this work, PVPCS(Poly (4-vinyl pyridine-co-styrene))/FHAp nanocomposites of varying weight percentages were synthesized and characterized physical-chemically by XRD, FTIR, 31P NMR, TGA, DTA, and FE-SEM and biologically by antimicrobial and anti-inflammatory assays for evaluating their potential use for biomedical applications. The results indicated that the size and crystallinity of FHAp nanoparticles decrease with increase in PVPCS concentration in the composite. SEM confirmed the presence of FHAp nano rod crystals in PVPCS matrix. The nano PVPCS20/FHAp demonstrated the highest antifungal and antibacterial activity and favorable inhibition of human cell hemolysis. The designed PVPCS/FHAp nanocomposites constitute promising candidates for biomedical applications.

  8. Facile Synthesis of Thick Films of Poly(methyl methacrylate), Poly(styrene), and Poly(vinyl pyridine) from Au Surfaces

    PubMed Central

    Saha, Sampa

    2011-01-01

    Atom transfer radical polymerization (ATRP) is commonly used to grow polymer brushes from Au surfaces, but the resulting film thicknesses are usually significantly less than with ATRP from SiO2 substrates. On Au, growth of poly(methyl methacrylate) (PMMA) blocks from poly(tert-butyl acrylate) brushes occurs more rapidly than growth of PMMA from initiator monolayers, suggesting that the disparity between growth rates from Au and SiO2 stems from the Au surface. Radical quenching by electron transfer from Au is probably not the termination mechanism because polymerization from thin, cross-linked initiators gives film thicknesses that are essentially the same as the thicknesses of films grown from SiO2 under the same polymerization conditions. However, this result is consistent with termination through desorption of thiols from non-cross-linked films, and reaction of these thiols with growing polymer chains. The enhanced stability of cross-linked initiators allows ATRP at temperatures up to ~100 °C and enables the growth of thick films of PMMA (350 nm), polystyrene (120 nm) and poly(vinyl pyridine) (200 nm) from Au surfaces in 1 hour. At temperatures >100 °C, the polymer brush layers delaminate as large area films. PMID:21728374

  9. Fabrication of 3D interconnected porous TiO2 nanotubes templated by poly(vinyl chloride-g-4-vinyl pyridine) for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Koh, Joo Hwan; Koh, Jong Kwan; Seo, Jin Ah; Shin, Jong-Shik; Kim, Jong Hak

    2011-09-01

    Porous TiO2 nanotube arrays with three-dimensional (3D) interconnectivity were prepared using a sol-gel process assisted by poly(vinyl chloride-graft-4-vinyl pyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A 7 µm long ZnO nanorod array was grown from the fluorine-doped tin oxide (FTO) glass via a liquid phase deposition method. The TiO2 sol-gel solution templated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection between the adjacent ZnO nanorods during spin coating. Upon etching of ZnO, TiO2 nanotubes consisting of 10-15 nm nanoparticles were generated, as confirmed by wide-angle x-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). The ordered and interconnected nanotube architecture showed an enhanced light scattering effect and increased penetration of polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversion efficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight (Mw) and 0.74% for high Mw polymer electrolytes.

  10. Fabrication of 3D interconnected porous TiO2 nanotubes templated by poly(vinyl chloride-g-4-vinyl pyridine) for dye-sensitized solar cells.

    PubMed

    Koh, Joo Hwan; Koh, Jong Kwan; Seo, Jin Ah; Shin, Jong-Shik; Kim, Jong Hak

    2011-09-07

    Porous TiO(2) nanotube arrays with three-dimensional (3D) interconnectivity were prepared using a sol-gel process assisted by poly(vinyl chloride-graft-4-vinyl pyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A 7 µm long ZnO nanorod array was grown from the fluorine-doped tin oxide (FTO) glass via a liquid phase deposition method. The TiO(2) sol-gel solution templated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection between the adjacent ZnO nanorods during spin coating. Upon etching of ZnO, TiO(2) nanotubes consisting of 10-15 nm nanoparticles were generated, as confirmed by wide-angle x-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). The ordered and interconnected nanotube architecture showed an enhanced light scattering effect and increased penetration of polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversion efficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight (M(w)) and 0.74% for high M(w) polymer electrolytes.

  11. Poly(4-vinyl pyridine) radiografted PVDF track etched membranes as sensors for monitoring trace mercury in water

    NASA Astrophysics Data System (ADS)

    Bessbousse, H.; Zran, N.; Fauléau, J.; Godin, B.; Lemée, V.; Wade, T.; Clochard, M.-C.

    2016-01-01

    By a radiation-induced grafting technique, we have functionalized track-etched nanoporous polymer membranes with mercury sensitive poly-4-vinyl pyridine (P4VP). Coating of these membranes with a very thin layer of gold results in an electrochemical sensor that is very selective and highly sensitive for mercury LOD 5 ng/L - well below the norms for water (0.015 μg/L potable water and 0.5 μg/L residual waters-French water norms of 27 October 2011). E-beam irradiation permitted optimization of the radiografting synthesis on PVDF thin films prior to ion-track grafting. Synthesis and characterization by EPR, FESEM and FTIR are described in detail. A comparison between FTIR in ATR and transmission modes enabled us to localize the grafting on the surface of the e-beam irradiated PVDF films allowing us to extrapolate what happens on the etched tracks. Using Square Wave Anodic Stripping Voltammetry (SW-ASV), mercury concentrations of 1 μg/L are detected in 2 h and low ng/L concentrations are detected after 24 h of adsorption. The adsorption is passive so sensors do not require instrumentation and the analysis takes only 3-4 min. Also, the P4VP functionalized sensor appears insensitive to pH variations (pHs 3-9), high salt concentrations (up to 1 g/L) and the presence of other heavy metals in the same solution.

  12. Room temperature aqueous self-assembly of poly(ethylene glycol)-poly(4-vinyl pyridine) block copolymers: From spherical to worm-like micelles.

    PubMed

    Rodrigues, Daniela P; Costa, João R C; Rocha, Nuno; Góis, Joana R; Serra, Arménio C; Coelho, Jorge F J

    2016-09-01

    The solution self-assembly and the formation, at room temperature, of a wide range of nanostructures based on monomethyl ether poly(ethylene glycol)-b-poly(4-vinyl pyridine) (mPEG-b-P4VP) block copolymer is reported. Copolymers with different compositions and molecular weights were synthesized through Atom Transfer Radical Polymerization (ATRP) method. The solution self-assembly of the block copolymers was studied by transmission electron microscopy (TEM) for different solution pHs. It was found that the formation of non-spherical nanostructures, such as rod- and worm-like micelles can be easily achieved, at room temperature, by simply varying the molecular weight of the different segments as well as the mPEG to P4VP ratio in the block copolymer structure. Because P4VP segments are known to form strong complexes with metals, the nanostructures prepared in this manuscript can find innovative applications in the biomedical field and be used as nano-templates for inorganic materials.

  13. Water-stable diblock polystyrene-block-poly(2-vinyl pyridine) and diblock polystyrene-block-poly(methyl methacrylate) cylindrical patterned surfaces inhibit settlement of zoospores of the green alga Ulva.

    PubMed

    Grozea, Claudia M; Gunari, Nikhil; Finlay, John A; Grozea, Daniel; Callow, Maureen E; Callow, James A; Lu, Zheng-Hong; Walker, Gilbert C

    2009-04-13

    Nanopatterned surfaces with hydrophobic and hydrophilic domains were produced using the diblock copolymer polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA). The PS-b-P2VP diblock copolymer, mixed with the cross-linker benzophenone and spin-coated onto silicon wafers, showed self-assembled cylindrical structures, which were retained after UV treatment for cross-linking. The thin films displayed cylindrical domains after immersion in water. This study shows that pattern retention in water is possible for a long period of time, at least for two weeks in pure water and three weeks in artificial seawater. The PS-b-PMMA diblock showed self-assembled cylindrical structures. PS-b-P2VP and PS-b-PMMA cylindrical patterned surfaces showed reduced settlement of zoospores of the green alga Ulva compared to unpatterned surfaces. The copolymers were investigated using atomic force microscopy and X-ray photoelectron spectroscopy.

  14. Cationic vinyl pyridine copolymers and products thereof

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor)

    1978-01-01

    Quaternized, cross-linked, insoluble copolymers of unsubstituted and substituted vinyl pyridines and a dihalo organic compound are spontaneously formed at ambient temperature on mixing the two monomers in bulk, in solution or in suspension. The amount of cross-linking may be varied according to the composition and reaction conditions. The polymer product exhibits ion exchange capacity and undergoes a reversible color change from black at a pH above 7 to yellow at a pH below 7. The polymer may be formed in the presence of preformed polymers, substrates such as porous or impervious particles or films to deposit an ion exchange film in situ or on the surface of the substrate. The coated or resin impregnated substrate may be utilized for separation of anionic species from aqueous solution.

  15. Study of the ordered structures of poly(styrene-b-vinyl4pyridine) in a solution state by using small-angle X-ray scattering and generalized indirect Fourier transform.

    PubMed

    Park, Soo-Young; Chang, Yun-Jeong; Farmer, B L

    2006-12-19

    The structures of the mesophases and their subunits (micelles) of poly(styrene-b-vinyl4pyridine) (PS-b-P4VP) in a toluene solution were studied by using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and generalized indirect Fourier transform (GIFT) methods. The structures of PS-b-P4VP, such as the individual micelle, the face-centered cubic (fcc) and body-centered cubic (bcc), and the lamellar, were identified. The SAXS from the PS-b-P4VP solution showed a good contrast for the micelle, even in a low concentration of 0.25 wt %. As the concentration increases, the fcc and both fcc and bcc appear for the packing of the micelles of PS(3.3K)-b-P4VP(4.7K) and PS(12K)-b-P4VP(11.8K), respectively. The lamellar structure was also identified, with a further increase in the concentration for PS(3.3K)-b-P4VP(4.7K). These structures were also identified via TEM images.

  16. Organometallic mediated radical polymerization of vinyl acetate using bis(imino)pyridine vanadium trichloride complexes.

    PubMed

    Perry, Mitchell R; Allan, Laura E N; Decken, Andreas; Shaver, Michael P

    2013-07-07

    The synthesis and characterization of one novel proligand and six novel vanadium(III) trichloride complexes is described. The controlled radical polymerization activity towards vinyl acetate of these, and eight other bis(imino)pyridine vanadium trichloride complexes previously reported, is investigated. Those complexes possessing variation at the N-aryl para-position with no steric protection offered by ortho-substituents (4 examples) result in poor control over poly(vinyl acetate) polymerization. Control is improved with increasing steric bulk at the ortho-position of the N-aryl substituent (4 examples) although attempts to increase steric bulk past isopropyl were unsuccessful. Synthesizing bis(imino)pyridine vanadium trichloride complexes with substituted imine backbones restores polymerization control when aliphatic substituents are used (4 examples) but ceases to make any drastic improvements on catalyst lifetime. Modification of the polymerization conditions is also investigated, in an attempt to improve the catalyst lifetime. Expansion of the monomer scope to include other vinyl esters, particularly those derived from renewable resources, shows promising results.

  17. Evaluation of morphology, aggregation pattern and size-dependent drug-loading efficiency of gold nanoparticles stabilised with poly (2-vinyl pyridine)

    NASA Astrophysics Data System (ADS)

    Rahim, Sana; Ali, Syed Abid; Ahmed, Farid; Imran, Muhammad; Shah, Muhammad Raza; Malik, Muhammad Imran

    2017-07-01

    Presence of basic nitrogen throughout the chain of poly(2-vinylpyridine) make them alluring candidate for applications requiring chelation of heavy metals. In this study, we report the use of poly (2-vinylpyridine) (P2VP) homopolymers of varying molar masses for the stabilization of gold nanoparticles for the first time. A study based on AFM, DLS and UV-visible spectroscopy was conducted to establish a correlation of the molar mass of P2VP with the size and distribution of the gold nanoparticles. Systematic and gradual change in the absorbance intensity and shift in SPR band of gold nanoparticles were also observed upon variations in treatment temperature, concentration of polymer, residence time, pH, and electrolyte concentration. The results obtained by UV-visible spectroscopy, AFM and DLS are complementary. The size of the P2VP-stabilised AuNPs was found to be in the range of 20-130 nms. At last, the effect of the size of P2VP-stabilised AuNPs (directly related to the molar mass of P2VP) on the drug-loading efficiency is evaluated. [Figure not available: see fulltext.

  18. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  19. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  20. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  1. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  2. MECHANICAL PROPERTIES OF BLENDS OF PAMAM DENDRIMERS WITH POLY(VINYL CHLORIDE) AND POLY(VINYL ACETATE)

    EPA Science Inventory

    Hybrid blends of poly(amidoamine) PAMAM dendrimers with two linear high polymers, poly(vinyl chloride), PVC, and poly(vinyl acetate), PVAc, are reported. The interaction between the blend components was studied using dynamic mechanical analysis, xenon nuclear magnetic resonacne ...

  3. MECHANICAL PROPERTIES OF BLENDS OF PAMAM DENDRIMERS WITH POLY(VINYL CHLORIDE) AND POLY(VINYL ACETATE)

    EPA Science Inventory

    Hybrid blends of poly(amidoamine) PAMAM dendrimers with two linear high polymers, poly(vinyl chloride), PVC, and poly(vinyl acetate), PVAc, are reported. The interaction between the blend components was studied using dynamic mechanical analysis, xenon nuclear magnetic resonacne ...

  4. Poly(vinyl alcohol)/poly(vinyl chloride) composite polymer membranes for secondary zinc electrodes

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Yang, Jen Ming; Wu, Cheng-Yeou

    A microporous composite polymer membrane composed of poly(vinyl alcohol) (PVA) and poly(vinyl chloride) (PVC), was prepared by a solution casting method and a partial dissolution process. The characteristic properties of microporous PVA/PVC composite polymer membranes containing 2.5-10 wt.% PVC polymers as fillers were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), capillary flow porometry (CFP), micro-Raman spectroscopy, dynamic mechanical analyzer (DMA) and the AC impedance method. The electrochemical properties of a secondary Zn electrode with the PVA/PVC composite polymer membrane were studied using the galvanostatic charge/discharge method. The PVA/PVC composite polymer membrane showed good thermal, mechanical and electrochemical properties. As a result, the PVA/PVC composite polymer membrane appears to be a good candidate for use on the secondary Zn electrodes.

  5. Poly(vinyl chloride) processes and products.

    PubMed Central

    Wheeler, R N

    1981-01-01

    Poly(vinyl chloride) resins are produced by four basic processes: suspension, emulsion, bulk and solution polymerization. PVC suspensions resins are usually relatively dust-free and granular with varying degrees of particle porosity. PVC emulsion resins are small particle powders containing very little free monomer. Bulk PVC resins are similar to suspension PVC resins, though the particles tend to be more porous. Solution PVC resins are smaller in particle size than suspension PVC with high porosity particles containing essentially no free monomer. The variety of PVC resin products does not lend itself to broad generalizations concerning health hazards. In studying occupational hazards the particular PVC process and the product must be considered and identified in the study. PMID:7333230

  6. Thermal Decomposition and Stabilisation of Poly(vinyl Chloride)

    NASA Astrophysics Data System (ADS)

    Troitskii, B. B.; Troitskaya, L. S.

    1985-08-01

    The kinetics and mechanism of the thermal dehydrochlorination of poly(vinyl chloride) and low-molecular-weight chlorohydrocarbons which model various fragments of the polymer molecule, are discussed. Studies designed to determine the qualitative and quantitative compositions of the unstable fragments in poly(vinyl chloride) macromolecules by 13C NMR are examined. Attention is concentrated on the consideration of the mechanism of the action of the most effective thermostabilisers for the polymer - organotin compounds. The principal features of synergism in the stabilisation of poly(vinyl chloride) and the mechanism of the action of synergistic mixtures are analysed. The bibliography includes 107 references.

  7. Hydrothermal carbonization of poly(vinyl chloride).

    PubMed

    Poerschmann, J; Weiner, B; Woszidlo, S; Koehler, R; Kopinke, F-D

    2015-01-01

    Poly(vinyl chloride) (PVC) was subjected to hydrothermal carbonization in subcritical water at 180-260 °C. Dehydrochlorination increased with increasing reaction temperature. The release of chlorine was almost quantitative above ∼235 °C. The fraction of organic carbon (OC) recovered in the hydrochar decreased with increasing operating temperature from 93% at 180 °C to 75% at 250 °C. A wide array of polycyclic aromatic hydrocarbons (PAHs) could be detected in the aqueous phase, but their combined concentration amounted to only ∼140 μg g(-1) PVC-substrate at 240 °C. A pathway for the formation of cyclic hydrocarbons and O-functionalized organics was proposed. Chlorinated hydrocarbons including chlorophenols could only be identified at trace levels (low ppb). Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) could not be detected. The sorption potential of the hydrochar turned out to be very low, in particular for polar organic pollutants. Our results provide strong evidence that hydrothermal carbonization of household organic wastes which can be tied to co-discarded PVC-plastic residues is environmentally sound regarding the formation of toxic organic products. Following these findings, hydrothermal treatment of PVC-waste beyond operating temperatures of ∼235 °C to allow complete release of organic chlorine should be further pursued.

  8. Worker exposure to vinyl chloride and poly(vinyl chloride).

    PubMed Central

    Jones, J H

    1981-01-01

    The National Institute for Occupational Safety and Health (NIOSH) in early 1974 began industrial hygiene studies of vinyl chloride exposed workers. Three VC monomer plants, three VC polymerization plants, and seven PVC fabrication plants were surveyed. V polymerization plant workers and workers in one job category in VC monomer plants were exposed to average levels above 1 ppm. The highest average exposure was 22 ppm. NIOSH health hazard evaluation studies since these initial surveys have primarily shown nondetectable levels of vinyl chloride. A NIOSH control technology study in 1977 showed that exposure levels in VC polymerization plants had been drastically reduced but exposure levels above 1 ppm were still found in several cases. PMID:7333231

  9. Radiation-chemical preparation of poly(vinyl alcohol) hydrogels

    NASA Astrophysics Data System (ADS)

    Duflot, Anastasia V.; Kitaeva, Natalia K.; Duflot, Vladimir R.

    2015-02-01

    This work reports the usage of method of radiation-chemical synthesis to prepare cross-linked hydrogels from poly(vinyl alcohol) modified with glycidyl methacrylate. Synthesis kinetics of modified poly(vinyl alcohol) and properties of hydrogels were studied. The gel fraction, swelling, mechanical properties, and water content of the hydrogels were measured. It was found that gel fraction increases with increasing radiation dose, concentration of modified poly(vinyl alcohol), and reaches 60%. It was established by differential scanning calorimetry that a fraction of the "bound" water in hydrogels is 50-70% and independent of gel fraction content. In addition to "bound" and "free" states, water in hydrogels is also present in the intermediate state.

  10. Methods for the synthesis of deuterated vinyl pyridine monomers

    DOEpatents

    Hong, Kunlun; Yang, Jun; Bonnesen, Peter V

    2015-01-13

    Methods for synthesizing deuterated vinylpyridine compounds of the Formula (1), wherein the method includes: (i) deuterating an acyl pyridine of the Formula (2) in the presence of a metal catalyst and D.sub.2O, wherein the metal catalyst is active for hydrogen exchange in water, to produce a deuterated acyl compound of Formula (3); (ii) reducing the compound of Formula (3) with a deuterated reducing agent to convert the acyl group to an alcohol group, and (iii) dehydrating the compound produced in step (ii) with a dehydrating agent to afford the vinylpyridine compound of Formula (1). The resulting deuterated vinylpyridine compounds are also described.

  11. Methods for the synthesis of deuterated vinyl pyridine monomers

    SciTech Connect

    Hong, Kunlun; Yang, Jun; Bonnesen, Peter V

    2014-02-25

    Methods for synthesizing deuterated vinylpyridine compounds of the Formula (1), wherein the method includes: (i) deuterating an acyl pyridine of the Formula (2) in the presence of a metal catalyst and D.sub.2O, wherein the metal catalyst is active for hydrogen exchange in water, to produce a deuterated acyl compound of Formula (3); (ii) reducing the compound of Formula (3) with a deuterated reducing agent to convert the acyl group to an alcohol group, and (iii) dehydrating the compound produced in step (ii) with a dehydrating agent to afford the vinylpyridine compound of Formula (1). The resulting deuterated vinylpyridine compounds are also described.

  12. Electrospun nanofibers of poly (vinyl alcohol) reinforced with cellulose nanofibrils

    USDA-ARS?s Scientific Manuscript database

    In this work, nanofibers of poly (vinyl alcohol) (PVA) reinforced with cellulose nanofibrils (CnF) were produced by electrospinning. The effects of applied voltage, polymer concentration and injection rate, tip-to-collector distance (TCD), rotation speed of the collector, and relative humidity on m...

  13. Preparation of Syndiotactic Poly(vinyl alcohol)/Poly(vinyl pivalate/vinyl acetate) Microspheres with Radiopacity Using Suspension Copolymerization and Saponification

    NASA Astrophysics Data System (ADS)

    Seok Lyoo, Won; Wook Cha, Jin; Young Kwak, Kun; Jae Lee, Young; Yong Jeon, Han; Sik Chung, Yong; Kyun Noh, Seok

    2010-06-01

    To prepare Poly(vinyl pivalate/vinyl acetate) [P(VPi/VAc)] microspheres with radiopacity, the suspension copolymerization approach in the presence of aqueous radiopaque nanoparticles was used. After, The P(VPi/VAc) microspheres with radiopacity were saponified in heterogeneous system, and then P(VPi/VAc) microspheres without aggregates were converted to s-PVA/P(VPi/VAc) microspheres of skin/core structure through the heterogeneous surface saponification. Radiopacity of microspheres was confirmed with Computed tomography (CT).

  14. Toxicity of vinyl chloride and poly(vinyl chloride): a critical review.

    PubMed Central

    Wagoner, J K

    1983-01-01

    In 1974, vinyl chloride (VC) was first reported in the open scientific literature to induce angiosarcoma of the liver both in humans and in animals. Additional research has now demonstrated the carcinogenicity of VC to other organs and at lower concentrations. The target organs for VC now clearly include the liver, brain and the lung, and probably the lymphohematopoietic system. The evidence for a carcinogenic risk has been extended to jobs associated with poly(vinyl chloride) exposure. Cases of liver angiosarcoma have been reported among individuals employed in PVC fabrication facilities and an epidemiological study has demonstrated a significant association between exposure to PVC dust and the risk of lung cancer mortality. Cases of angiosarcoma of the liver also have been reported among individuals living in near proximity to vinyl chloride-poly(vinyl chloride) plants. An association between PVC dust and pneumoconiosis also has been demonstrated. On the basis of findings, prudent control of PVC dust in the industrial setting is indicated. PMID:6360677

  15. Characterisation of poly(vinyl alcohol) by liquid chromatography techniques

    SciTech Connect

    Meehan, E.; Warner, F.P.; Patterson, M.

    1995-12-01

    The molecular weight distribution of poly (vinyl alcohol) can be measured by aqueous size exclusion chromatography methods but the choice of eluent is critical in eliminating non size exclusion behavior. Aqueous size exclusion experiments have been carried out using a number of eluents including standard electrolytes and surfactants. The most favorable molecular size separation was obtained using 0.25% w/v sodium lauryl sulphate as eluent. Compositional distributions in copolymer systems can be assessed using high performance liquid chromatography employing a reverse phase separation mechanism. For poly (vinyl alcohol) gradient elution with water/tetrahydrofuran was found to produce a separation according to composition. Fast gradient elution (>10% tetrahydrofuran/minute) suggested abroad distribution of composition which was verified using a column packed with non-porous beads. Slower gradient elution (<1% tetrahydrofuran/minute) suggested that this was not due to a gradual composition change but rather discrete fractions of similarly hydrophobic material.

  16. Industrial preparation of poly(vinyl chloride).

    PubMed Central

    Cohan, G F

    1975-01-01

    Vinyl chloride (VCM) is unloaded from railroad tank cars or tank trucks into pressurized storage spheres. VCM, emulsifiers, and catalysts are metered into polymerization vessels wherein PVC is produced through a chemical reaction in an aqueous medium under controlled conditions of temperature and pressure. After the reaction reaches a predetermined completion, the contents are transferred to a secondary vessel wherein steam is injected and the VCM containing vapors are pumped to a recovery system. The VCM-containing vapors are compressed, cooled, condensed, decanted, and recycled to the process for reuse. The stripped PVC resin water slurry is then pumped to blending tanks where the batches from multiple reaction vessels are blended for product uniformity. From the plant tanks the PVC resin water slurry is pumped to a dewatering centrifuge, where approximately 90% of the water is removed and subsequently discharged to the industrial sewer system. The PVC resin wet cake is conveyed from the centrifuge to a flash dryer where essentially all the remaining water is removed. At this point, the dry resin is buoyant in an air stream and enters a two-stage collection system for separation of conveying air. The PVC resin is then screened and air-conveyed to storage for bulk shipment, compounding, or bagging. PMID:1175567

  17. Tunneling conduction in graphene/(poly)vinyl alcohol composite

    NASA Astrophysics Data System (ADS)

    Mitra, Sreemanta; Banerjee, Sourish; Chakravorty, Dipankar

    2013-04-01

    Graphene/(Poly)vinyl alcohol (PVA) composite film with thickness 60μm was synthesized by solidification of a PVA solution comprising of dispersed graphene nanosheets. The close proximity of the graphene sheets enables the fluctuation induced tunneling of electrons to occur from one sheet to another. The dielectric data show that the present system can be simulated to a parallel resistance-capacitor network. The high frequency exponent of the frequency variation of the ac conductivity indicates that the charge carriers move in a two-dimensional space. The sample preparation technique will be helpful for synthesizing flexible conductors.

  18. Tuning of surface properties of poly vinyl alcohol by using graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Mishra, Mukesh; Mohanty, T.

    2017-05-01

    In this work, we emphasize on the surface property modification involved during the strong interfacial adhesion of graphene oxide (GO) nanosheets with poly vinyl alcohol (PVA) matrix. Raman, x-ray diffraction spectrum and scanning Kelvin probe microscopic measurement were done to analyze the effect of graphene oxide on surface property of poly vinyl alcohol.

  19. Preparation and application of low molecular weight poly(vinyl chloride). III mechanical properties of blended poly(vinyl chloride)

    SciTech Connect

    Yamamoto, Kikuo; Maehala, Takashi; Mitani, Katsuo; Mizutani, Yukio )

    1993-11-05

    The blending effect of poly(vinyl chloride) with relatively higher molecular weight (HMW-PVC) and relatively lower molecular weight (LMW-PVC) has been investigated by measuring various mechanical properties: melt properties, tensile strength, tensile modulus, and impact strength. The blended PVC has slightly improved melt properties in comparison with the HMW-PVC used. The tensile strength of the blended PVC is related to the weight-average polymerization degree (Pw) of LMW-PVC and the LMW-PVC content. At the LMW-PVC content of 20%, the tensile strength of blended PVC is a maximum: approximately 58 MPa.

  20. Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers.

    PubMed

    Knecht, Daniela; Rittig, Frank; Lange, Ronald F M; Pasch, Harald

    2006-10-13

    A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.

  1. Separator Membrane from Crosslinked Poly(Vinyl Alcohol) and Poly(Methyl Vinyl Ether-alt-Maleic Anhydride)

    PubMed Central

    Rohatgi, Charu Vashisth; Dutta, Naba K.; Choudhury, Namita Roy

    2015-01-01

    In this work, we report separator membranes from crosslinking of two polymers, such as poly vinyl alcohol (PVA) with an ionic polymer poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-MA). Such interpolymer-networked systems were extensively used for biomedical and desalination applications but they were not examined for their potential use as membranes or separators for batteries. Therefore, the chemical interactions between these two polymers and the influence of such crosslinking on physicochemical properties of the membrane are systematically investigated through rheology and by critical gel point study. The hydrogen bonding and the chemical interaction between PMVE-MA and PVA resulted in highly cross-linked membranes. Effect of the molecular weight of PVA on the membrane properties was also examined. The developed membranes were extensively characterized by studying their physicochemical properties (water uptake, swelling ratio, and conductivity), thermal and electrochemical properties using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The DSC study shows the presence of a single Tg in the membranes indicating compatibility of the two polymers in flexible and transparent films. The membranes show good stability and ion conductivity suitable for separator applications. PMID:28347019

  2. Conductance in Water-Poly(vinyl alcohol) Mixtures

    PubMed Central

    Komiyama, Jiro; Fuoss, Raymond M.

    1972-01-01

    The conductance of 0.02-0.10 N potassium chloride in poly(vinyl alcohol)-water mixtures at 25° decreases by about 50% as the polymer content increases from zero to 20% by weight, while the bulk viscosity increases from 0.0089 to over 1000 poises. Further increases in polymer concentration transform the highly viscous liquid into an elastomeric solid, in which the conductance still remains relatively high; it decreases significantly only after the glass composition (75% polymer at 25°) is reached. The internal viscosity, which controls ionic mobility, was estimated from the conductance data: it ranges from 0.01 to about 0.14 over the range 0-55% polymer, similar to the viscosity of many ordinary liquids. Rates of diffusion-controlled processes involving small molecules in macromolecular media can, therefore, be expected to be similar to those in usual solution. PMID:16591975

  3. Physical and conductivity properties of poly (vinyl chloride) ionomers

    NASA Astrophysics Data System (ADS)

    Misra, Nira; Panda, H. S.; Kapusetti, Govinda; Jaiswal, Shilpa; Bhattacharya, Subhratanu

    2011-02-01

    Poly (vinyl chloride)(PVC) is a cheapest plastic. Importance of PVC based ionomer has been gradually being popularizing due to compatibility of PVC with a number of salts to replace polyethylene oxide based ionomer. Under present investigation few of chloride group of PVC chain have been replaced by basic thiouronium group and these thiouronium groups are further oxidized to sulfonate group. Introduction of thiouronium group in PVC is confirmed through FTIR and further its oxidation to sulfonate group is also confirmed by FTIR. Conductivity in different stoichiometric ratio of PVCTU and PVCSO3H was studied and found that PVCTU: PVCSO3H in 1:1 ratio has conductivity near to pure PVC (10-9 Ohm-1 cm-1) and increases with proportion of PVCSO3Na in the mixture (10-6 Ohm-1 cm-1) for pure PVC, PVCTU has less conductivity not much significant.

  4. Immobilization of enzyme onto poly(ethylene-vinyl alcohol) membrane

    SciTech Connect

    Imai, K.; Shiomi, T.; Uchida, K.; Miya, M.

    1986-02-01

    Invertase was ionically bound to the poly(ethylene-vinyl alcohol) membrane surface modified with two aminoacetals with different molecular length, 2-dimethyl-aminoacetoaldehyde dimethylacetal (AAA) and 3-(N,N-dimethylamino-n-propanediamine) propionaldehyde dimethylacetal (APA). Immobilization conditions were determined with respect to enzyme concentration in solution, pH value, ionic strength in immobilization solution, and immobilization time. Various properties of immobilized invertase were evaluated, and thermal stability was found especially to be improved by immobilization. The apparent Michaelis constant, Km, was smaller for invertase bound by APA with longer molecular lengths than for invertase bound by AAA. We attempted to bind glucoamylase of Rhizopus delemarorigin in the same way. The amount and activity of immobilized glucoamylase were much less than those of invertase. 16 references.

  5. Immobilization of enzyme into poly(vinyl alcohol) membrane

    SciTech Connect

    Imai, K.; Shiomi, T.; Uchida, K.; Miya, M.

    1986-11-01

    Glucoamylase, invertase, and cellulase were entrapped within poly(vinyl alcohol) (PVA) membrane cross-linked by means of irradiation of ultraviolet light. The conditions for immobilization of glucoamylase were examined with respect to enzyme concentration in PVA, sensitizer (sodium benzoate) concentration in PVA, irradiation time, and membrane thickness. Various characteristics of immobilized glucoamylase were evaluated. Among them, the pH activity curve for the immobilized enzyme was superior to that for the native one, and thermal stability was improved by immobilization with bovine albumin. The apparent Km was larger for immobilized glucoamylase than for the native one, while Vmax was smaller for the immobilized enzyme. Also, the apparent Km appeared to be affected by the molecular size of the substrate. Further, immobilized invertase and cellulase showed good stabilities in repeating usage. 9 references.

  6. SYNTHESIS AND INVESTIGATION OF HIGH-MOLECULAR-WEIGHT TERTIARY AMINES AND QUATERNARY AMMONIUM COMPOUNDS FROM COPOLYMERS OF 2-METHYL-5-VINYL-PYRIDINE AND VARIOUS CROSS-LINKING AGENTS

    DTIC Science & Technology

    AMIDES, *COPOLYMERIZATION, *ION EXCHANGE RESINS, *PYRIDINES, ACRYLIC RESINS, ALKYL RADICALS, BENZENE, CHEMICAL PROPERTIES, CHEMICAL REACTIONS ...ETHYLENES, GLYCOLS, METHYL RADICALS, PHYSICAL PROPERTIES, POLYMERIZATION, POLYMERS, SYNTHESIS, VINYL RADICALS.

  7. Effects of solvents on the radiation grafting reaction of vinyl compounds on poly (3-hydroxybutyrate)

    NASA Astrophysics Data System (ADS)

    Torres, Maykel González; Talavera, José Rogelio Rodríguez; Muñoz, Susana Vargas; Pérez, Manuel González; Castro, Ma. Pilar. Carreón.; Cortes, Jorge Cerna; Muñoz, Rodrigo Alonso Esparza

    2015-03-01

    Vinyl Acetate was grafted onto poly (3-hydroxybutyrate) by the simultaneous gamma irradiation method using different types of solvents and in bulk (solvent free), at 10 kGy and 1.62 kGy/h dose and dose rate respectively. Subsequent complete hydrolysis allowed the conversion of grafted chains from poly (vinyl acetate) to poly (vinyl alcohol). The aim of this study is to determine the effect of solvent through the estimation of the dependence of the degree of grafting with the choice of solvent, the calculation of the degree of crystallinity, and to study the biodegradation of the products. The results showed a greater degree of grafting in bulk, while the more suitable solvent was hexane. Characterization of the grafted copolymer indicated that crystallinity percentage decreased by an increase in grafting, while the biodegradability was promoted by the increment in poly (vinyl alcohol) grafted.

  8. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...(vinyl fluoride) basic resins have an intrinsic viscosity of not less than 0.75 deciliter per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride... (ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride...

  9. A 'degradable' poly(vinyl alcohol) iron oxide nanoparticle hydrogel.

    PubMed

    Bannerman, A Dawn; Li, Xinyi; Wan, Wankei

    2017-08-01

    Polymeric materials that contain magnetic nanoparticles are extremely useful in many applications including as multifunctional drug carriers, imaging contrast agents, or scaffold material. There is a need for biomaterials with appropriate chemical, mechanical, and magnetic properties that also have the ability to degrade or dissolve over time so they can be eliminated from the body following use. In this work, we explore the use of iron oxide nanoparticle (IONP) formation in poly(vinyl alcohol) (PVA) as a crosslinking method in conjunction with physical crosslinking achieved using low temperature thermal cycling (LTTC). PVA-IONP hydrogels were fabricated and characterized. IONPs contribute to the crosslinking of the PVA-IONP material, and their subsequent removal reduces crosslinking, and therefore stability, of the material, allowing dissolution to occur. Dissolution studies were performed on PVA-IONP hydrogels and dissolution was compared for films in solutions of varying pH, in the presence of iron chelating agents, and in simulated physiological and tumor conditions in cell culture media. Iron release, mass loss, and mechanical testing data was collected. This work demonstrates the ability of this biomaterial to 'degrade' over time, which may be very advantageous for applications such as drug delivery. This importance of this work extends to other areas such as the use of stimuli-responsive hydrogels. This manuscript explores the stability of an iron oxide nanoparticle (IONP)-containing, physically crosslinked poly(vinyl alcohol) (PVA) hydrogel. The PVA-IONP hydrogel's stability is imparted through crosslinks created through a low temperature thermal cycling process and through the IONPs. Subsequent IONP removal reduces crosslinks so material dissolution can occur, resulting in a 'degradable' and multifunctional biomaterial. PVA-IONP films were fabricated, characterized and evaluated in terms of dissolution in solutions of varying pH and in the presence of

  10. Study of poly(3-hexylthiophene)/cross-linked poly(vinyl alcohol) as semiconductor/insulator for application in low voltage organic field effect transistors

    NASA Astrophysics Data System (ADS)

    Benvenho, Adriano R. V.; Machado, Wagner S.; Cruz-Cruz, Isidro; Hümmelgen, Ivo A.

    2013-06-01

    In this work we study the cross-linked poly(vinyl alcohol)/poly(3-hexylthiophene) interfacial properties of an organic field effect transistor. We use cross-linked poly(vinyl alcohol) prepared with different ammonium dichromate:poly(vinyl alcohol) proportions, ranging from 0% to 35%, as insulator. Using admittance spectroscopy, we show that the interfacial properties change when the ammonium dichromate concentration is altered. The interfacial properties and the better insulation are responsible for the improvement of the device performance in these organic field effect transistors, achieving best performance in the blend with ammonium dichromate:poly(vinyl alcohol) proportion of 0.25:1.

  11. Properties of electrospun pollock gelatin/poly(vinyl alcohol) and pollock gelatin/poly(lactic acid) fibers

    USDA-ARS?s Scientific Manuscript database

    Pollock gelatin/poly(vinyl alcohol) (PVA) fibers were electrospun using deionized water as the solvent and pollock gelatin/poly(lactic acid) (PLA) fibers were electrospun using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the solvent. The chemical, thermal, and thermal stability properties were exami...

  12. Fabrication of aligned poly (vinyl alcohol) nanofibers by electrospinning.

    PubMed

    Chuangchote, Surawut; Supaphol, Pitt

    2006-01-01

    Electrospinning has become a versatile tool for fabricating nanofibers from materials of diverse origins. Normally, mats of randomly-aligned fibers were obtained. A number of techniques have been proposed to arrive at uniaxially-aligned fibers. This work reports a new technique, i.e., dual vertical wire technique, for fabrication of uniaxially-aligned fibers. This technique utilized two stainless steel wires that were vertically set in a parallel manner between a charged needle and a grounded collector plate. This technique allowed simultaneous collection of aligned fibers (between the parallel vertical wires) and a randomly-aligned fiber mat (on the collector plate). Application of the technique on poly(vinyl alcohol) (PVA) to prepare uniaxially-aligned fibers was found to be successful at short collection times. Unexpected formation of a large fiber tow consisting of individual as-spun nanofibers that were bound into a bundle was observed at long collection times. Morphological appearance and size of the fiber tow was affected by the change in the distance between the two vertical wire electrodes, while the average diameter of the individual fibers was not (i.e., about 340 to 350 nm). Lastly, mechanical properties and thermal behavior of the fiber tow were also investigated.

  13. Self-assembled hemocompatible coating on poly (vinyl chloride) surface

    NASA Astrophysics Data System (ADS)

    Zha, Zhengbao; Ma, Yan; Yue, Xiuli; Liu, Meng; Dai, Zhifei

    2009-11-01

    A stable hemocompatible coating was fabricated by consecutive alternating adsorption of iron (III) and two kinds of polysaccharides, heparin (Hep) and dextran sulfate (DS), onto poly (vinyl chloride) (PVC) surfaces via electrostatic interaction. The fluctuation of contact angles with the alternative deposition of iron (III) and polysaccharides verified the progressive buildup of the mulitilayer coating onto the PVC surface. Atomic force microscopy (AFM) analysis revealed that the PVC surfaces were completely masked by iron-polysaccharides multilayer coatings. The activated partial thromboplastin time (APTT) assay showed that both Hep/Fe 3+/Hep and DS/Fe 3+/Hep coated PVC were less thrombogenic than the uncoated one. Chromogenic assay for heparin activity proved definitively that the inhibition of locally produced thrombin was ascribed to the thromboresistance of the surface-bound heparin. Compared with the unmodified PVC surfaces, iron-polysaccharide multilayer coating presented a drastically reduced adhesion in vitro of platelets, polymorphonuclear neutrophil leukocytes (PMN) and peripheral blood mononuclear cells (PBMC). Interestingly, the DS/Fe 3+/Hep coating was found to exhibit higher hydrophilicity and stability, hence lower non-specific protein adsorption in comparison with Hep/Fe 3+/Hep coating due to the incorporation of dextran sulfate into the multilayer coating.

  14. Gas production in the radiolysis of poly(vinyl chloride).

    PubMed

    LaVerne, Jay A; Carrasco-Flores, Eduardo A; Araos, M S; Pimblott, Simon M

    2008-04-17

    The yields of H2 and Cl- were determined in the radiolysis of deaerated, aerated, and water mixtures of poly(vinyl chloride) (PVC) powders with gamma-rays and 5 MeV He ions. H2 yields with gamma-rays are low at about 0.25 molecule/100 eV and they double with He ion radiolysis indicating a second order formation process. The production of H2 in the gamma-radiolysis of water-PVC mixtures is much greater than expected from the weight fraction of the components and is due to acidification of the aqueous phase by the evolution of HCl from the polymer. Cl- yields in the gamma-radiolysis of PVC with number average weights of 22,000, 47,000, and 99,000 Daltons are 19.6, 33.8, and 32.5 atoms/100 eV. Cl- continuously evolves from the polymer for days following radiolysis. The extremely large yields suggest that a chain process involving radicals stabilized on the polymeric chain are responsible. Reflectance UV/vis and infrared spectroscopy show subtle changes in the PVC with radiolysis while UV/vis absorption spectra clearly indicate the formation of polyenes with 1 to 11 units. Cl- formation is probably initiated by Cl radical production followed by an electron rearrangement mechanism along the PVC chain to produce more Cl- and polyenes.

  15. Poly(vinyl alcohol) gels as photoacoustic breast phantoms revisited

    NASA Astrophysics Data System (ADS)

    Xia, Wenfeng; Piras, Daniele; Heijblom, Michelle; Steenbergen, Wiendelt; van Leeuwen, Ton G.; Manohar, Srirang

    2011-07-01

    A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F-T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where temperature distributions during F-T are relatively homogeneous. In this work, in breast-sized samples we observed substantial temperature differences between the shallow regions and the interior during the F-T procedure. We investigated whether spatial variations were also present in the acoustic and optical properties. The speed of sound, acoustic attenuation, and optical reduced scattering coefficients were measured on specimens sampled at various locations in a large phantom. In general, the properties matched values quoted for breast tissue. But while acoustic properties were relatively homogeneous, the reduced scattering was substantially different at the surface compared with the interior. We correlated these variations with gel microstructure inspected using scanning electron microscopy. Interestingly, the phantom's reduced scattering spatial distribution matches the optical properties of the standard two-layer breast model used in x ray dosimetry. We conclude that large PVA samples prepared using the standard recipe make excellent breast tissue phantoms.

  16. Broadband Dielectric Study on Dynamics of Poly(vinyl pyrrolidone)-Poly(ethylene glycol) Blend

    NASA Astrophysics Data System (ADS)

    Tsubotani, S.; Sudo, S.; Nakamura, H.; Shinyashiki, N.; Yagihara, S.; Sengwa, R. J.

    2004-04-01

    Dielectric measurements for blends of poly(vinyl pyrrolidone) (PVP) (Mw=40,000) and poly(ethylene glycol) (PEG) (Mw=400) with various compositions were carried out in the frequency range of 1μHz to 10GHz and temperatures range between 298 and 173K. Three relaxation processes were observed above 298K. The high frequency process (h1 process) is caused by the chain motion of PEG, the middle frequency process (m process) is caused by the segmental motion of PVP chains, and the low frequency process is caused by ionic impurities in the mixture. The relaxation time of h1 process increased with decreasing temperature and separated into two processes at 253K. Moreover h1 process was separated again at 223K. The relaxation time of h1 process was 100s at 208K. The glass transition is attributed to the motion of unfrozen PEG molecules.

  17. Fabrication of Poly (methyl methacrylate) and Poly(vinyl alcohol) Thin Film Capacitors on Flexible Substrates

    NASA Astrophysics Data System (ADS)

    Salim, Bindu; Meenaa Pria KNJ, Jaisree; Alagappan, M.; Kandaswamy, A.

    2015-11-01

    Flexible electronics is becoming more popular with introduction of more and more organic conducting materials and processes for making thin films. The use of polymers as gate dielectric has over ruled the usage of conventional inorganic oxides in Organic Thin Film Transistors (OTFTs) on account of its solution process ability and ease of making highly insulating thin film. In this work Capacitance is fabricated with polymeric dielectrics namely poly (methyl methacrylate) - PMMA and poly (vinyl alcohol) - PVA. The electrodes used for these capacitors are Indium Tin Oxide (ITO) and Aluminium. Capacitance value of 9.5nF/cm2 and 33.12nF/cm2 is achieved for thickness of 510 nm of PMMA and 80 nm of PVA respectively. This study on capacitance can be used for assessing the suitability of these polymers as gate insulators in OTFTs.

  18. Chitosan/poly (vinyl pyrollidone) coatings improve the antibacterial properties of poly(ethylene terephthalate)

    NASA Astrophysics Data System (ADS)

    Wang, Bai-liang; Wang, Jin-lei; Li, Dan-dan; Ren, Ke-feng; Ji, Jian

    2012-08-01

    Chitosan/poly (vinyl pyrollidone) (CHI/PVP) coatings were prepared to improve the antibacterial properties of poly (ethylene terephthalate) (PET) by a simple dip-coating method. The binding capability of CHI/PVP coatings was enhanced by successively pretreatment of PET by polyetherimide and polyacrylic acid and crosslinking. Measurements of water contact angle and atomic force microscope revealed that the coatings created a highly hydrophilic surface with low roughness. Adherences of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) on PET with CHI/PVP coating were significantly reduced. Bactericidal activity of CHI/PVP coatings was good against E. coli and S. aureus and the adding of PVP obviously increased its antiadhesion property. In vitro cytotoxicity tests, cell morphology and activity evaluation of human umbilical vein endothelial cells showed that CHI/PVP coatings had good biocompatibility.

  19. Reaction of N-vinylic phosphazenes with alpha,beta-unsaturated aldehydes. Azatriene-mediated synthesis of dihydropyridines and pyridines derived from beta-amino acids.

    PubMed

    Palacios, Francisco; Herran, Esther; Alonso, Concepción; Rubiales, Gloria; Lecea, Begoña; Ayerbe, Mirari; Cossío, Fernando P

    2006-08-04

    Aza-Wittig reaction of N-vinylic phosphazenes (1,2 addition), derived from diphenylmethylphosphine or derived from trimethylphosphine with alpha,beta-unsaturated aldehydes, leads to the formation of 3-azatrienes through a [2 + 2]-cycloaddition-cycloreversion sequence. The presence of an alkyl substituent in position 3 of N-vinylic phosphazenes increases the steric interactions, and [4 + 2] periselectivity (1,4 addition) is observed. Reaction of azatrienes with alpha,beta-unsaturated aldehydes yields pyridines.

  20. Development of functionalized hydroxyapatite/poly(vinyl alcohol) composites

    NASA Astrophysics Data System (ADS)

    Stipniece, Liga; Salma-Ancane, Kristine; Rjabovs, Vitalijs; Juhnevica, Inna; Turks, Maris; Narkevica, Inga; Berzina-Cimdina, Liga

    2016-06-01

    Based on the well-known pharmaceutical excipient potential of poly(vinyl alcohol) (PVA) and clinical success of hydroxyapatite (HAp), the objective of this work was to fabricate functionalized composite microgranules. PVA was modified with succinic anhydride to introduce carboxyl groups (-COOH), respectively, by reaction between the -OH groups of PVA and succinic anhydride, for attachment of drug molecules. For the first time, the functionalized composite microgranules containing HAp/PVA in the ratio of 1:1 were prepared through in situ precipitation of HAp in modified PVA aqueous solutions followed by spray drying of obtained suspensions. The microgranules were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry (DSC). The presence of -COOH groups was verified by FT-IR, and the amount of functional groups added to PVA molecules (averaging 15 mol%) was determined by nuclear magnetic resonance spectroscopy (NMR). DSC results showed that modification with -COOH groups slightly decreased the thermal stability of PVA. FT-IR and XRD analysis confirmed that the resulting composites contain mainly nanocrystalline HAp and PVA. Moreover, the images taken by FE-SEM revealed that the microgranules consisted of nanosized HAp crystallites homogenously embedded in the PVA matrix. DSC measurements indicated that decomposition mechanism of the HAp/PVA differs from that of pure PVA and occurs at lower temperatures. However, the presence of HAp had minor influence on the thermal decomposition of the PVA modified with succinic anhydride. The investigation of composite microgranules confirmed interaction and integration between the HAp and PVA.

  1. Non-mulberry silk sericin/poly (vinyl alcohol) hydrogel matrices for potential biotechnological applications.

    PubMed

    Mandal, Biman B; Ghosh, Borna; Kundu, S C

    2011-08-01

    This study reports a novel biopolymeric matrix fabricated by chemically cross-linking poly (vinyl alcohol) with silk sericin protein obtained from cocoons of the tropical tasar silkworm Antheraea mylitta. Glutaraldehyde was used as a cross-linking agent with hydrochloric acid acting as an initiator. The matrices were biophysically characterized and the cytocompatibility of the matrices was evaluated for their suitability as biomaterials. The surface morphology was assessed using atomic force microscopy while the changes taking place after cross-linking were confirmed by Fourier transform infrared spectroscopy. The enhanced thermal stability of the constructs was assessed by thermogravimetric and differential scanning calorimetry. Fourier transform infrared spectroscopy analysis showed that sericin was chemically cross-linked with poly (vinyl alcohol) using glutaraldehyde. Silk sericin protein demonstrated a favorable effect on animal cell culture by successfully improving the adhering and spreading of cells on the poorly adhering surface of poly (vinyl alcohol). Confocal microscopy revealed cell spreading and actin filament development in sericin/poly (vinyl alcohol) hydrogel matrices. These findings prove the potential of non-mulberry silk sericin/poly (vinyl alcohol) hydrogel matrices to be used as biocompatible and biopolymeric material for tissue-engineering and biotechnological applications. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Unusual Morphologies of Poly(vinyl alcohol) Thin Films Adsorbed on Poly(dimethylsiloxane) Substrates.

    PubMed

    Karki, Akchheta; Nguyen, Lien; Sharma, Bhanushee; Yan, Yan; Chen, Wei

    2016-04-05

    Adsorption of poly(vinyl alcohol) (PVOH), 99% and 88% hydrolyzed poly(vinyl acetate), to poly(dimethylsiloxane) (PDMS) substrates was studied. The substrates were prepared by covalently attaching linear PDMS polymers of 2, 9, 17, 49, and 116 kDa onto silicon wafers. As the PDMS molecular weight/thickness increases, the adsorbed PVOH thin films progressively transition from continuous to discontinuous morphologies, including honeycomb and fractal/droplet. The structures are the result of thin film dewetting that occurs upon exposure to air. The PVOH film thickness does not vary significantly on these PDMS substrates, implicating the PDMS thickness as the cause for the morphology differences. The adsorbed PVOH thin films are less stable and have a stronger tendency to dewet on thicker, more liquid-like PDMS layers. When PVOH(99%) and PVOH(88%) thin films are compared, fractal and droplet morphologies are observed on high molecular weight PDMS substrates, respectively. The formation of the unique fractal features in the PVOH(99%) thin films as well as other crystalline and semicrystalline thin films is most likely driven by crystallization during the dehydration process in a diffusion-limited aggregation fashion. The only significant enhancement in hydrophilicity via PVOH adsorption was obtained on PDMS(2k), which is completely covered with a PVOH thin film. To mimic the lower receding contact angle and less liquid-like character of the PDMS(2k) substrate, light plasma treatment of the higher molecular weight PDMS substrates was carried out. On the treated PDMS substrates, the adsorbed PVOH thin films are in the more continuous honeycomb morphology, giving rise to significantly enhanced wettability. Furthermore, hydrophobic recovery of the hydrophilized PDMS substrates was not observed during a 1 week period. Thus, light plasma oxidation and subsequent PVOH adsorption can be utilized as a means to effectively hydrophilize conventional PDMS substrates. This study

  3. Preparation of albumin preferential surfaces on poly(vinyl chloride) membranes via surface self-segregation.

    PubMed

    Ji, Jian; Feng, Linxian; Shen, Jiacong; Barbosa, M A

    2002-08-01

    Poly(vinyl chlorides)-graft-[omega-stearyl-poly(ethylene oxide)] (PVC-g-SPEO), which has a poly(vinyl chloride) (PVC) backbone, poly(ethylene oxide) (PEO) side chain, and stearyl end groups, has been synthesized. Self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides) have been examined as a means to create albumin preferential surfaces on polymer films. X-ray photoelectron spectroscopy (XPS) analysis indicates substantial surface segregation of the PVC-g-SPEO. A surface concentration of 59.9 EO wt % is achieved by the solution casting and heat treatment of a film with a bulk concentration of only 3.78 EO wt %. In the aqueous environment, the surface rearrangement of PVC-g-SPEO/PVC blend film is limited and presents a high interfacial energy and high depolar component of interfacial energy due to the "tail-like" SPEO side chain. Protein adsorption tests confirm that PVC-g-SPEO/PVC blend films absorb high levels of albumin and dramatically resist fibrinogen adsorption. Surfaces to attract and reversibly bind albumin, which might diminish the occurrence of thrombosis, inflammation, and infection, are developed by self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides).

  4. Carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing.

    PubMed

    Zhang, Di; Zhou, Wei; Wei, Bing; Wang, Xin; Tang, Rupei; Nie, Jiemin; Wang, Jun

    2015-07-10

    The objective of this study was to develop a novel carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing. To prepare the crosslinked hydrogels, poly(vinyl alcohol) (PVA) was grafted with succinate acid to yield carboxyl-modified poly(vinyl alcohol) (PVA-COOH). Hydrogel films based on PVA-COOH and chitosan (CS) at different concentrations were crosslinked through the formation of amide linkages. The mechanical properties of these crosslinked hydrogel films in dry and swollen state were greatly improved with high swelling ratio. Water vapor and oxygen permeability evaluations indicated that crosslinked hydrogel films could maintain a moist environment over wound bed. Biocompatibility test showed the crosslinked hydrogels had no cytotoxicity and hemolytic potential. Gentamicin sulfate-loaded crosslinked hydrogel films showed sustained drug release profile, and could effectively suppress bacterial proliferation and protect wound from infection.

  5. Evaluation of CO2-philicity of poly(vinyl acetate) and poly(vinyl acetate-alt-maleate) copolymers through molecular modeling and dissolution behavior measurement.

    PubMed

    Hu, Dongdong; Sun, Shaojun; Yuan, Peiqing; Zhao, Ling; Liu, Tao

    2015-02-19

    Multiscale molecular modeling and dissolution behavior measurement were both used to evaluate the factors conclusive on the CO2-philicity of poly(vinyl acetate) (PVAc) homopolymer and poly(vinyl acetate-alt-maleate) copolymers. The ab initio calculated interaction energies of the candidate CO2-philic molecule models with CO2, including vinyl acetate dimer (VAc), dimethyl maleate (DMM), diethyl maleate (DEM), and dibutyl maleate (DBM), showed that VAc was the most CO2-philc segment. However, the cohesive energy density, solubility parameter, Flory-Huggins parameter, and radial distribution functions calculated by using the molecular dynamics simulations for the four polymer and polymer-CO2 systems indicated that poly(VAc-alt-DBM) had the most CO2-philicity. The corresponding polymers were synthesized by using free radical polymerization. The measurement of cloud point pressures of the four polymers in CO2 also demonstrated that poly(VAc-alt-DBM) had the most CO2-philicity. Although copolymerization of maleate, such as DEM or DBM, with PVAc reduced the polymer-CO2 interactions, the weakened polymer-polymer interaction increased the CO2-philicity of the copolymers. The polymer-polymer interaction had a significant influence on the CO2-philicity of the polymer. Reduction of the polymer-polymer interaction might be a promising strategy to prepare the high CO2-philic polymers on the premise that the strong polymer-CO2 interaction could be maintained.

  6. Vinyl stilbazoles

    NASA Technical Reports Server (NTRS)

    Parker, John A. (Inventor); Heimbuch, Alvin H. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1986-01-01

    Vinyl pyridines including vinyl stilbazole materials and vinyl styrylpyridine oligomer materials are disclosed. These vinylpyridines form copolymers with bismaleimides which copolymers have good fire retardancy and decreased brittleness. The cure temperatures of the copolymers are substantially below the cure temperatures of the bismaleimides alone. Reinforced composites made from the cured copolymers are disclosed as well.

  7. Structural and electronic properties of poly(vinyl alcohol) using density functional theory

    SciTech Connect

    Dabhi, Shweta Jha, Prafulla K.

    2014-04-24

    The first principles calculations have been carried out to investigate the structural, electronic band structure density of states along with the projected density of states for poly(vinyl alcohol). Our structural calculation suggests that the poly(vinyl alcohol) exhibits monoclinic structure. The calculated structural lattice parameters are in excellent agreement with available experimental values. The band structure calculations reveal that the direct and indirect band gaps are 5.55 eV and 5.363 eV respectively in accordance with experimental values.

  8. Modifying theophylline microparticle surfaces via the sequential deposition of poly(vinyl alcohol-co-vinyl acetate) copolymers.

    PubMed

    Zhao, Yanjun; Alas'ad, Mannar A; Jones, Stuart A

    2014-03-10

    The aim of this study was to investigate the manner in which amphiphilic poly(vinyl alcohol-co-vinyl acetate) copolymers (PVA-Ac) assembled on drug surfaces and use this information to generate a novel bi-layer polymer coating for a theophylline microparticle. Three grades of PVA-Ac, differing in hydrolysis degree and monomer distribution, were synthesised, characterised by nuclear magnetic resonance and shown to interact with theophylline when suspended in water. PVA-Ac deposition at the solid/liquid interface was driven by polymer hydrogen bond formation in a process that induced consequential structural changes in the macromolecule architecture. The most hydrophobic grades of the copolymer appeared to adsorb in a multistage process that passed through a series of equilibrium points. The PVA-Ac surface allowed two grades of the copolymer to be sequentially adsorbed and this resulted in the fabrication of a microparticle with desirable characteristics for pharmaceutical formulation production.

  9. Water vapor absorption into amorphous sucrose-poly(vinyl pyrrolidone) and trehalose-poly(vinyl pyrrolidone) mixtures.

    PubMed

    Zhang, J; Zografi, G

    2001-09-01

    Previous studies from this laboratory suggested that a solution model (Flory-Huggins equation) modified by a free volume model (Vrentas equation) could satisfactorily describe water absorption into an amorphous solid composed of a sugar or a polymer. This paper has extended the studies of single solutes to binary mixtures of trehalose-and sucrose-poly(vinyl pyrrolidone) (trehalose-PVP and sucrose-PVP, respectively) either co-lyophilized or individually lyophilized and then physically mixed. Water vapor absorption isotherms of the binary mixtures were determined at 30 degrees C. Co-lyophilized PVP-sugar mixtures take up essentially the same amount of water as predicted by the weight average of individual isotherms, whereas sugar crystallization is significant retarded in the molecular dispersions. The sugar-PVP interaction, as reflected in the Flory-Huggins chi interaction parameter, was estimated by fitting the high relative pressure (p/p(0)) region of the isotherm, at which the system is in a liquid state, with a three-component Flory-Huggins-type model. The estimated sugar-water PVP-water, and sugar-PVP interaction parameters suggest that the solute-water interactions are not significantly affected by the sugar-PVP interaction; that is, the solute-water interaction parameters in a binary solute system are similar to those in the corresponding single solute systems. Based on these interaction parameters, the sucrose-PVP interaction appears to be stronger than that of trehalose-PVP. Manipulation of the interaction parameters suggest that the water vapor absorption isotherm is not a sensitive indicator of possible sugar-PVP interactions. Density, glass transition temperature, T(g), and the heat capacity change, DeltaC(p), at T(g) were determined to estimate the excess water absorption energy due to the plasticizing effect of water using the structural relaxation model, as described by Vrentas. Results suggest that PVP is a better antiplasticizer for sucrose than for

  10. Bioinert membranes prepared from amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) graft copolymers.

    PubMed

    Patel, Rajkumar; Patel, Madhumita; Ahn, Sung Hoon; Sung, Yong Kiel; Lee, Hyung-Keun; Kim, Jong Hak; Sung, Jung-Suk

    2013-04-01

    Poly(vinyl chloride) (PVC) membrane was hydrophilically modified by grafting with poly(oxyethylene methacrylate) (POEM) using atom transfer radical polymerization (ATRP). The successful grafting of PVC main chain by POEM was characterized by Fourier transform infrared spectroscopy (FT-IR). The molecular weight and hydrophilicity of membranes increased with the amount of POEM grafting, as characterized by gel permeation chromatography (GPC) and contact angle measurement, respectively. Transmission electron microscope (TEM) and small angle X-ray scattering (SAXS) analysis revealed the microphase-separated structure of PVC-g-POEM and the domain spacing increased from 59.3 to 86.1 nm with increasing grafting degree. Scanning electron microscopy (SEM) was used for the direct visualization of the mouse embryonic fibroblast (MEF) cell and bacteria adhesion on the membrane surface. Protein adsorption and eukaryotic and prokaryotic cell adhesion tests showed that the bioinert properties of membranes were significantly increased with POEM content. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Preparation and study of poly(vinyl acetate) and poly(styrene) nanosized latex with indometacin.

    PubMed

    Andonova, V; Georgiev, G; Toncheva, V; Kassarova, M

    2012-07-01

    During the last decade the number of investigations on the preparation and application of more effective drug release systems on the basis of nanocarriers from biocompatible and biodegradable polymers are considerably increasing. This is notably in force for practically water insoluble drugs to be applied in liquid forms (eye solutions for an example). The aim of the work presented was the preparation of model poly(vinyl acetate) and poly(styrene) nanosupports for indometacin and their potential inclusion in eye drops. The polymers are synthesized as nanosized latex by a radical polymerization of the monomers in the presence of indometacin. It is proved that the low polymerization temperature and initiator used do not influence indometacin structure and properties. The nanoparticles were characterized by attenuated total reflection Fourier transform infrared spectroscopic analyses, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The size of the latex particles was around 200 nm, determined by the scan electron microscopy. The indometacin delivery rate from the supports discussed in aqueous solutions was determined at pH 7.4. The change of this rate, in comparison with that for a pure drug substance, was established also as well as its dependence on the nature of the carrier.

  12. FOAMED ARTICLES BASED ON POTATO STARCH, CORN AND WHEAT FIBRE, AND POLY(VINYL ALCOHOL)

    USDA-ARS?s Scientific Manuscript database

    Continued research cooperation between USDA Laboratories (USA) and the University of Pisa, Italy, has yielded several composites based on blends of poly(vinyl alcohol) (PVA) and either corn or wheat fibres, co-product of the corn-wheat wet-milling process. Foam trays were prepared by baking the blen...

  13. Structural characterisation of printable noble metal/poly(vinyl-alcohol) nanocomposites for optical applications.

    PubMed

    Hourd, A C; Baker, R T; Abdolvand, A

    2015-08-28

    In order to enable exploitation of noble metal/poly(vinyl-alcohol) nanocomposites for device fabrication, solutions of poly(vinyl-alcohol) suitable for piezo-driven inkjet printing techniques are identified and discussed in terms of their material properties. The printable poly(vinyl-alcohol) medium is then exploited as a host material through the formation of silver or gold nanoparticles in order to create nanocomposites that exhibit a surface plasmon resonance behaviour associated with the small metallic inclusions. To mitigate some of the material redistribution effects associated with the drying of printed droplets containing finely divided materials, the metallic nanoparticles are formed after the printing and drying process is completed, by way of an in situ reduction of an appropriate metal salt by the poly(vinyl-alcohol)-host matrix itself, which takes place at modest temperatures compatible with most substrate materials. An obvious application for such nanocomposites is in optical elements whereby the surface plasmon resonance associated with the metal is the functional aspect of devices such as sensors or active optical elements. High Resolution Transmission Electron Microscopy was used to examine the dimensions, distribution, morphology and crystal structure of the silver and gold nanoparticles in detail allowing discussion of their suitability for these applications and what further optimisation may be necessary to adequately control their formation.

  14. Films from spruce galactoglucomannan blended with poly(vinyl alcohol), corn arabinoxylan and konjac glucomannan

    USDA-ARS?s Scientific Manuscript database

    The improvement of mechanical properties of spruce galactoglucomannan (GGM)-based films was sought by blending GGM with each of poly(vinyl alcohol) (PVOH), corn arabinoxylan (cAX), and konjac glucomannan (KGM). The blend ratios were 3:1, 1:1, and 1:3(w/w), and in addition films were made from each o...

  15. Piezoelectric textures based on poly(vinyl chloride) filled with dispersed lead zirconate titanate (PZT-19)

    NASA Astrophysics Data System (ADS)

    Luchnikov, A. P.; Sigov, A. S.

    2009-07-01

    This paper reports on the results in investigations into the properties of piezoelectric textured materials that are formed through technological treatment of a mixture of components of dispersed poly(vinyl chloride) and a ferroelectric powder with the application of an external mechanical shear stress and an electric field.

  16. Improved cellular response of chemically crosslinked collagen incorporated hydroxyethyl cellulose/poly(vinyl) alcohol nanofibers scaffold.

    PubMed

    Zulkifli, Farah Hanani; Jahir Hussain, Fathima Shahitha; Abdull Rasad, Mohammad Syaiful Bahari; Mohd Yusoff, Mashitah

    2015-02-01

    The aim of this research is to develop biocompatible nanofibrous mats using hydroxyethyl cellulose with improved cellular adhesion profiles and stability and use these fibrous mats as potential scaffold for skin tissue engineering. Glutaraldehyde was used to treat the scaffolds water insoluble as well as improve their biostability for possible use in biomedical applications. Electrospinning of hydroxyethyl cellulose (5 wt%) with poly(vinyl alcohol) (15 wt%) incorporated with and without collagen was blended at (1:1:1) and (1:1) ratios, respectively, and was evaluated for optimal criteria as tissue engineering scaffolds. The nanofibrous mats were crosslinked and characterized by scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Scanning electron microscope images showed that the mean diameters of blend nanofibers were gradually increased after chemically crosslinking with glutaraldehyde. Fourier transform infrared spectroscopy was carried out to understand chemical interactions in the presence of aldehyde groups. Thermal characterization results showed that the stability of hydroxyethyl cellulose/poly(vinyl alcohol) and hydroxyethyl cellulose/poly(vinyl alcohol)/collagen nanofibers was increased with glutaraldehyde treatment. Studies on cell-scaffolds interaction were carried out by culturing human fibroblast (hFOB) cells on the nanofibers by assessing the growth, proliferation, and morphologies of cells. The scanning electron microscope results show that better cell proliferation and attachment appeared on hydroxyethyl cellulose/poly(vinyl alcohol)/collagen substrates after 7 days of culturing, thus, promoting the potential of electrospun scaffolds as a promising candidate for tissue engineering applications.

  17. Disk Refining and Ultrasonication Treated Sugarcane Bagasse Residues for Poly(Vinyl Alcohol) Bio-composites

    Treesearch

    Qingzheng Cheng; Zhaohui Tong; Luisa Dempere; Lonnie Ingram; Letian Wang; J.Y. Zhu

    2013-01-01

    Disk refining and ultrasonication treated sugarcane bagasse residues reclaimed from the waste stream of a simplified bioethanol process after fermentation were used to fabricate biobased composites with poly(vinyl alcohol) (PVA) by film casting. The morphologies and the size distributions of residue particles were characterized by scanning electronic microscopy and...

  18. Electrospun nanofibers of poly(vinyl alcohol)reinforced with cellulose nanofibrils

    USDA-ARS?s Scientific Manuscript database

    In this work, nanofibers of poly(vinyl alcohol) (PVA) reinforced with cellulose nanofibrils (CnF) were produced by electrospinning. The effects of applied voltage, polymer concentration and injection rate, tip-to-collector distance (TCD), rotation speed of the collector, and relative humidity on mor...

  19. NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES PREPARED UNDER MICROWAVE IRRADIATION

    EPA Science Inventory

    A facile microwave irradiation approach that results in a cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic and bimetallic systems is described. Nanocomposites of PVA cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-P...

  20. Microstructure and molecular interaction in glycerol plasticized chitosan/poly(vinyl alcohol) blending films

    USDA-ARS?s Scientific Manuscript database

    Poly (vinyl alcohol) (PVA)/chitosan (CS) blended films plasticized by glycerol were investigated using mechanical testing, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and FTIR spectroscopy, with primary emphasis on the effects of the glycerol content and the molecular weig...

  1. NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES PREPARED UNDER MICROWAVE IRRADIATION

    EPA Science Inventory

    A facile microwave irradiation approach that results in a cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic and bimetallic systems is described. Nanocomposites of PVA cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-P...

  2. Pyridine

    Integrated Risk Information System (IRIS)

    Pyridine ; CASRN 110 - 86 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects

  3. Layered Poly(ethylene-co-vinyl acetate)/Poly(ethylene-co-vinyl alcohol) Membranes with Enhanced Water Separation Selectivity and Performance.

    PubMed

    Soto Puente, J A; Fatyeyeva, K; Chappey, C; Marais, S; Dargent, E

    2017-02-22

    A three-layered membrane based on poly(ethylene-co-vinyl acetate) (EVA) and hydrolyzed EVA-poly(ethylene-co-vinyl alcohol) (EVOH), was elaborated by the surface hydrolysis of a dense EVA membrane. Because of the chemical modifications, the three-layered EVOH/EVA/EVOH membrane was characterized by the particular microstructure (amorphous EVA and semicrystalline EVOH) and the tunable hydrophilic/hydrophobic balance. Also, these modifications led to the membrane with the selective barrier properties compared with the pure EVA and completely hydrolyzed EVOH membranes. The water barrier behavior was related to the strong hydrogen-bond interactions of water and vinyl alcohol groups, whereas the weak chemical interactions were revealed for gases (N2 and O2). Furthermore, the influence of the polymer rubbery or glassy state on the permeation kinetics was established. In the case of the three-layered membrane, the considerably high selectivity values were obtained for H2O/O2 (∼11 900) and H2O/N2 (∼48 000) at 25 °C. In addition to these highly selective properties, the three-layered structure does not present delamination features due to its elaboration procedure. Thus, these new layered membranes are very promising as selective materials for the water and gas separation and can be potentially used in food packaging or for the gas dehydration.

  4. Electrodialytic Transport Properties of Anion-Exchange Membranes Prepared from Poly(vinyl alcohol) and Poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride)

    PubMed Central

    Jikihara, Atsushi; Ohashi, Reina; Kakihana, Yuriko; Higa, Mitsuru; Kobayashi, Kenichi

    2012-01-01

    Random-type anion-exchange membranes (AEMs) have been prepared by blending poly(vinyl alcohol) (PVA) and the random copolymer-type polycation, poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride) at various molar percentages of anion-exchange groups to vinyl alcohol groups, Cpc, and by cross-linking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations, CGA. The characteristics of the random-type AEMs were compared with blend-type AEMs prepared in our previous study. At equal molar percentages of the anion exchange groups, the water content of the random-type AEMs was lower than that of the blend-type AEMs. The effective charge density of the random-type AEMs increased with increasing Cpc and reached a maximum value. Further, the maximum value of the effective charge density increased with increasing CGA. The maximum value of the effective charge density, 0.42 mol/dm3, was obtained for the random-type AEM with Cpc = 4.2 mol % and CGA = 0.15 vol %. A comparison of the random-type and blend-type AEMs with almost the same Cpc showed that the random-type AEMs had lower membrane resistance than the blend-type ones. The membrane resistance and dynamic transport number of the random-type AEM with Cpc = 6.0 mol % and CGA = 0.15 vol % were 4.8 Ω cm2 and 0.83, respectively. PMID:24958543

  5. Review of pulmonary effects of poly(vinyl chloride) and vinyl chloride exposure.

    PubMed

    Lilis, R

    1981-10-01

    The contributions of several recent reports to the definition of pulmonary effects of PVC dust inhalation are reviewed. Granulomatous reaction, with inclusion of PVC particles in macrophages and histocytes, and associated interstitial pulmonary fibrosis have been found to lead to exertional dyspnoea, diffuse micronodular chest radiographic opacities and restrictive pulmonary dysfunction. The effects of vinyl chloride (VC) monomer (gas) on proteins and the immunologic mechanisms triggered by the altered protein are possible mechanisms for the development in some cases of interstitial pulmonary fibrosis secondary to VC exposure. Vinyl chloride, a confirmed carcinogen, has been associated with, among other malignant tumors, a significant increase in the incidence of lung cancer. The magnitude of this effect has not yet been completely evaluated.

  6. Biomaterial properties evaluation of poly(vinyl acetate- alt-maleic anhydride)/chitosan nanocapsules

    NASA Astrophysics Data System (ADS)

    Raţă, Delia Mihaela; Popa, Marcel; Chailan, Jean-François; Zamfir, Carmen Lăcrămioara; Peptu, Cătălina Anişoara

    2014-08-01

    Nanocapsules with diameter around 100 nm based on a natural polymer (chitosan) and a synthetic polymer poly(vinyl acetate- alt-maleic anhydride) [poly(MAVA)] by interfacial condensation method were prepared. The present study proposes a new type of biocompatible nanocapsules based on poly(vinyl acetate- alt-maleic anhydride-chitosan) (MCS) able to become a reliable support for inclusion and release of drugs. The spherical shape of the nanocapsules was evidenced by scanning electron microscopy. Nanocapsules presented a good Norfloxacin loading and release capacity. Haemocompatibility tests have demonstrated that the nanocapsules present a low toxicity and a good compatibility with sanguine medium. The biocompatibility properties of the nanocapsules after their intraperitoneal administration in rats were evidenced by histopathological examination of different organs (brain, liver, kidney, and lung). The results are encouraging and the nanocapsules can be used as controlled drug delivery systems.

  7. Poly(vinyl alcohol) reinforced and toughened with poly(dopamine)-treated graphene oxide, and its use for humidity sensing.

    PubMed

    Hwang, Sang-Ha; Kang, Dongwoo; Ruoff, Rodney S; Shin, Hyeon Suk; Park, Young-Bin

    2014-07-22

    Poly(dopamine)-treated graphene oxide/poly(vinyl alcohol) ("dG-O/PVA") composite films were made and characterized. G-O was modified with poly(dopamine) in aqueous solution and then chemically reduced to yield poly(dopamine)-treated reduced G-O. A combination of hydrogen bonding, strong adhesion of poly(dopamine) at the interface of PVA and G-O sheets, and reinforcement by G-O resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure by 39, 100, and 89%, respectively, at 0.5 wt % dG-O loading of the PVA. The dG-O serves as a moisture barrier for water-soluble PVA, and the dG-O/PVA composite films were shown to be effective humidity sensors over the relative humidity range 40-100%.

  8. Poly(N-vinylpyrrolidone)-block-poly(vinyl acetate) as a drug delivery vehicle for hydrophobic drugs.

    PubMed

    Bailly, Nathalie; Thomas, Mark; Klumperman, Bert

    2012-12-10

    Poly((N-vinylpyrrolidone)-block-poly(vinyl acetate)) (PVP-b-PVAc) block copolymers of varying molecular weight and hydrophobic block lengths were synthesized via controlled radical polymerization and investigated as carriers for the solubilization of highly hydrophobic riminophenazine compounds. These compounds have recently been shown to exhibit a strong activity against a variety of cancer types. PVP-b-PVAc self-assembles into polymer vesicles in aqueous media, and the dialysis method was used to load the water-insoluble drug (clofazimine) into these polymer vesicles. The polymer vesicles were characterized by 1H NMR spectroscopy to confirm vesicle formation and the incorporation of the anticancer drugs into the polymer vesicles. Dynamic light scattering was used to determine the particle size and particle size distribution of the drug-loaded vesicles as well as the stability of the vesicles under physiological conditions. The size of the polymer vesicles did not increase upon loading with clofazimine, and the particle size of 180-200 nm and the narrow particle size distribution were maintained. The morphology of the vesicles was examined by transmission electron microscopy. The polymer vesicles had a relatively high drug loading capacity of 20 wt %. In vitro cytotoxicity studies of PVP-b-PVAc and drug-loaded PVP-b-PVAc were performed against MDA-MB-231 multidrug-resistant breast epithelial cancer cells and MCF12A nontumorigenic breast epithelial cells. In vitro experiments demonstrated that the PVP-b-PVAc drug carrier showed no cytotoxicity, which confirms the biocompatibility of the PVP-b-PVAc drug carrier. The results indicate that the present PVP-b-PVAc block copolymer could be a potential candidate as a drug carrier for hydrophobic drugs.

  9. Polyblends of Poly(vinyl alcohol) and Poly(Vegr;-caprolactone) and Their Properties

    NASA Astrophysics Data System (ADS)

    Arcana, I. M.; Alio, L.

    2008-03-01

    The increasing volume of plastic has caused the serious problem in environment. One way to solve this problem is preparation of new plastic materials which can be decomposed by microorganisms in environment These plastics may be prepared from non-biodegradable material by modification of theirs physical and chemical properties, preparation of theirs copolymers and polyblends. The main problem in preparation of polyblends is compatibility between polymers mixtures. In this work has focused on preparation of polyblends between poly(vinyl alcohol) (PVA) and poly(ɛ-caprolactone) (PCL) in various compositions by casting of polymers solution. Characterizations of polyblends were carried out by analysis of functional groups (FTIR), thermal property (DSC and TGA/DTA), mechanical properties (Tensile tester), and crystallinity (XRD). The results of polyblends showed that the compatible and homogeneous polyblends were obtained in solvent composition (dimethyl sulfoxide/tetrahydrofurane) (DMSO/THF) of 3:1 and PCL ratio in polyblends less than 15 % (w/w). The absorption intensity of carbonyl and alkyl groups observed in 1725 cm-1 and 2940 cm-1 increased with increasing PCL composition in polyblends. The melting point (Tm) and fusion enthalpy (ΔHm) for PCL region in polyblends decreased with decreasing PCL composition, but melting point (Tm) and fusion of enthalpy (ΔHm) for PVA region increased. The total fusion enthalpy value obtained by observation was smaller than that of calculation value, indicating the presence of interaction between PCL and PVA to form a part of compatible polyblends with more amorphous structure. The mechanical properties of polyblends tended to decrease with increasing PCL ratio in polyblends. These results were supported by analysis of crystallinity with using X-ray diffraction.

  10. Effect of gamma ray on poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends as biodegradable food packaging films

    NASA Astrophysics Data System (ADS)

    Razavi, Seyed Mohammad; Dadbin, Susan; Frounchi, Masoud

    2014-03-01

    Poly(lactic acid) (PLA)/poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-co-VA) immiscible blends, while the glass transition temperature of the PLA phase decreased; that of the copolymer phase slightly increased. The reduction in the glass transition was about 10 percent for samples irradiated with 50 kGy indicating dominance of chain scission of PLA molecules at high irradiation dose. The latter was verified by drop in mechanical properties of pure PLA after exposing to gamma irradiation at 50 kGy. Blending of PLA with the copolymer P(VAc-co-VA) compensated greatly the adverse effects of irradiation on PLA. The oxygen-barrier property of the blend was superior to the neat PLA and remained almost intact with irradiation. The un-irradiated and irradiated blends had excellent transparency. Gamma ray doses used for sterilization purposes are usually less than 20 kGy. It was shown that gamma irradiation at 20 kGy had no or little adverse effects on PLA/P(VAc-co-VA) blends mechanical and gas barrier properties.

  11. Tensile Properties of Poly (N-vinyl caprolactam) Gels

    NASA Technical Reports Server (NTRS)

    Morgret, Leslie D.; Hinkley, Jeffrey A.

    2004-01-01

    N-vinyl caprolactam was copolymerized with ethylene glycol dimethacrylate using a free-radical initiator in alcohol/water solution. The resulting gels were thermally-responsive in water, undergoing an approximate fivefold reversible volume shrinkage between room temperature and ca. 50 C. Tensile testing showed that the stress-strain behavior was qualitatively different in the collapsed state above the temperature-induced transition. At the higher temperature, gels were stiffer, more ductile, and showed greater time dependence. Implications for the design of gel actuators are briefly discussed.

  12. Poly(vinyl ester) Block Copolymers Synthesized by Reversible Addition−Fragmentation Chain Transfer Polymerizations

    SciTech Connect

    Lipscomb, Corinne E.; Mahanthappa, Mahesh K.

    2009-07-31

    Homopolymerizations and block copolymerizations of vinyl acetate (VAc), vinyl pivalate (VPv), and vinyl benzoate (VBz) by reversible addition-fragmentation chain transfer (RAFT) polymerization have been studied. Polymerizations of VAc initiated with 2,2{prime}-azobis(isobutyronitrile) (AIBN) at 60 C using two different xanthate RAFT agents C{sub 2}H{sub 5}OC(=S)SR (R = -CH(CH{sub 3})CO{sub 2}C{sub 2}H{sub 5} (1) and -CH(CH{sub 3})O{sub 2}CC(CH{sub 3}){sub 3} (2)) were examined to elucidate the dependence of the polydispersities of the resulting polymers on the RAFT agent leaving group R. RAFT agent 2, in which the leaving R-group mimics a growing vinyl ester polymer chain, consistently yields poly(vinyl acetates) having broader polydispersities than those synthesized using 1 (M{sub n} = 3.6-14 kg/mol and M{sub w}/M{sub n} = 1.15-1.33). While VPv exhibits similar controlled polymerization behavior to VAc, RAFT homopolymerizations of VBz mediated by 1 indicate this electron-deficient vinyl ester requires higher temperatures to effect controlled polymerizations to yield polymers having M{sub n} = 4-14 kg/mol and M{sub w}/M{sub n} = 1.29-1.53. Chain extension reactions from xanthate-terminated vinyl ester homopolymers with VAc, VPv, and VBz proceed with variable efficiencies to furnish block copolymers that microphase separate in the melt state as determined by small-angle X-ray scattering.

  13. Controlled release of theophylline from poly(vinyl alcohol) hydrogels/porous silicon nanostructured systems

    NASA Astrophysics Data System (ADS)

    Cervantes-Rincón, N.; Medellín-Rodríguez, F. J.; Escobar-Barrios, V. A.; Palestino, G.

    2013-03-01

    In this research, hybrid hydrogels of poly (vinyl alcohol)/ porous silicon (PSi)/theophylline were synthesized by the freezing and thawing method. We evaluated the influence of the synthesis parameters of the poly (vinyl alcohol) (PVA) hydrogels in relation to their ability to swell and drug released. The parameters studied (using an experimental design developed in Minitab 16) were the polymer concentration, the freezing temperature and the number of freezing/thawing (f/t) cycles. Nanostructured porous silicon particles (NsPSi) and theophylline were added within the polymer matrix to increase the drug charge and the polymer mechanical strength. The hybrid hydrogels were characterized by Infrared Spectroscopy Fourier Transform (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC), drug delivery kinetics were engineered according to the desired drug release schedule.

  14. Radiation-chemical synthesis of poly(vinyl alcohol) hydrogel containing dicyclohexano-18-crown-6

    NASA Astrophysics Data System (ADS)

    Zakurdaeva, O. A.; Nesterov, S. V.; Shmakova, N. A.; Semenova, G. K.; Sozontova, E. O.; Feldman, V. I.

    2007-12-01

    Radiation-chemical synthesis of poly(vinyl alcohol) hydrogels containing physically immobilized dicyclohexano-18-crown-6 was carried out. Remarkable gel fraction of 40-70% was observed at absorbed dose of about 5 kGy. Increasing degree of poly(vinyl alcohol) crosslinking led to growth of the efficiency of crown ether immobilization. Post-irradiation thermal annealing of the hydrogel samples at 120 °C for 0.5-5 h resulted in an increase of crown ether retention as compared with non-annealed samples by approximately 20% at the same absorbed dose. Preliminary results on a sorption behavior of the crown-containing hydrogels with respect to Sr 2+ cations in 2.4 M HNO 3 solution are presented.

  15. Dynamics of poly(vinyl methyl ketone) thin films studied by local dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Casalini, R.; Labardi, M.; Roland, C. M.

    2017-05-01

    Local dielectric spectroscopy, which entails measuring the change in resonance frequency of the conducting tip of an atomic force microscope to determine the complex permittivity of a sample with high spatial (lateral) resolution, was employed to characterize the dynamics of thin films of poly(vinyl methyl ketone) (PVMK) having different substrate and top surface layers. A free surface yields the usual speeding up of the segmental dynamics, corresponding to a glass transition suppression of 6.5° for 18 nm film thickness. This result is unaffected by the presence of a glassy, compatible polymer, poly-4-vinyl phenol (PVPh), between the metal substrate and the PVMK. However, covering the top surface with a thin layer of the PVPh suppresses the dynamics. The speeding up of PVMK segmental motions observed for a free surface is absent due to interfacial interactions of the PVMK with the glass layer, an effect not seen when the top layer is an incompatible polymer.

  16. Poly(vinyl alcohol) hydrogels: their synthesis and steps towards control of electroendosmosis.

    PubMed

    Purss, Helen K; Caulfield, Marcus J; Solomon, David H; Sommer-Knudsen, Jens

    2003-01-01

    Poly(vinyl alcohol) (PVAl) hydrogel networks cross-linked with glutaraldehyde were prepared and their properties as membranes examined using a variety of techniques including preparative electrophoresis. Electroendosmosis (EEO) was observed and shown to be the result of charges on the membrane and of complexation with borate buffer ions. Investigation of "glutaraldehyde" solutions showed acid entities in, or formed in "glutaraldehyde" were responsible for EEO. Techniques for using "glutaraldehyde" which minimize EEO are described.

  17. Composite poly(vinyl alcohol)/poly(vinyl acetate) electrospun nanofibrous mats as a novel wound dressing matrix for controlled release of drugs

    PubMed Central

    Jannesari, Marziyeh; Varshosaz, Jaleh; Morshed, Mohammad; Zamani, Maedeh

    2011-01-01

    The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release. PMID:21720511

  18. Composite poly(vinyl alcohol)/poly(vinyl acetate) electrospun nanofibrous mats as a novel wound dressing matrix for controlled release of drugs.

    PubMed

    Jannesari, Marziyeh; Varshosaz, Jaleh; Morshed, Mohammad; Zamani, Maedeh

    2011-01-01

    The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.

  19. Synthesis and characterization of foldable and magnetic field-sensitive, freestanding poly(vinyl acetate)/poly(vinyl chloride)/polyfuran composite and nanocomposite films

    NASA Astrophysics Data System (ADS)

    Sarıtaş, Sevilay; Eşsiz, Serpil; Sarı, Bekir

    2017-07-01

    In this study, polyfuran and poly(vinyl acetate)/poly(vinyl chloride)/polyfuran ternary composites were synthesized via the chemical polymerization method. The temperature and magnetic field-sensitive novel composites and the nanocomposite were obtained in the form of powders and films. It was observed that the prepared novel conductive films have superior properties at a certain temperature range (25-50 °C) such as bending and folding. The structural properties, thermal behavior, surface morphology, internal structure, and surface roughness of the prepared samples were investigated by various characterization techniques. The conductivities of the samples were measured at room temperature and different temperatures by the four-point technique. X-ray Diffraction analysis results demonstrated that the PF and composites have an amorphous structure, whereas the nanocomposite is in crystalline form. The saturation magnetization (Ms) values of the magnetite and nanocomposite were found to be 58.9 and 5.3 emu g-1, respectively. It was found that magnetite-doped nanocomposite has superparamagnetic properties at room temperature.

  20. Ultrasonic-assisted synthesis of phosphorus graphene oxide/poly (vinyl alcohol) polymer and surface resistivity research of phosphorus graphene oxide/poly (vinyl alcohol) film.

    PubMed

    Li, Jihui; Li, Yongshen; Niu, Shuai; Li, Ning

    2017-05-01

    In this paper, phosphorus graphene oxide/poly (vinyl alcohol) polymer (PGO/PVA polymer) was synthesized by PGO and PVA via the esterification in the case of faint acidity and the ultrasound irradiation and characterized; moreover, phosphorus graphene oxide/poly (vinyl alcohol) film (PGO/PVA film) was prepared by PGO/PVA polymer and characterized; also, the surface resistivity of PGO/PVA film was investigated in the case of the different amount of PGO. Based on those, it had been found that PGO reacted with PVA to produce PGO/PVA polymer via the esterification under the ultrasonic-assisted condition, and PGO/PVA polymer was structured by 2D lattice of PGO and the chain of PVA connected in the form of six-member lactone ring and phosphonic ester, and PGO/PVA film was constituted by PGO/PVA polymer, and surface resistivity of 0.00, 0.75, 1.50, 2.25 and 3.00wt% of PGO/PVA film were 6.85×10(8), 2.98×10(8), 1.42×10(6), 7.66×10(4) and 1.29×10(5)Ω/sq, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Poly(1-Vinyl-1,2,4-triazolium) Poly(Ionic Liquid)s: Synthesis and the Unique Behavior in Loading Metal Ions.

    PubMed

    Zhang, Weiyi; Yuan, Jiayin

    2016-07-01

    Herein, the synthesis of a series of poly(4-alkyl-1-vinyl-1,2,4-triazolium) poly(ionic liquid)s is reported either via straightforward free radical polymerization of their corresponding ionic liquid monomers or via anion metathesis of the polymer precursors bearing halide as counter anion. The ionic liquid monomers are first prepared via N-alkylation reaction of commercially available 1-vinyl-1,2,4-triazole with alkyl iodides, followed by anion metathesis with targeted fluorinated anions. The thermal properties and solubilities of these poly(ionic liquid)s have been systematically investigated. Interestingly, it is found that the poly(4-ethyl-1-vinyl-1,2,4-triazolium) poly(ionic liquid) exhibited an improved loading capacity of transition metal ions in comparison with its imidazolium counterpart.

  2. Branched polyesters based on poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide): effects of polymer structure on cytotoxicity.

    PubMed

    Unger, F; Wittmar, M; Kissel, T

    2007-03-01

    Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. For further optimization of this polymer class their cytotoxicity needs to be characterized establishing structure-toxicity relationships. Effects of type and degree of amine substitution as well as molecular weight on cytotoxicity were evaluated in L929 mouse fibroblasts using a MTT assay whereas interactions with cell membranes were quantified by LDH release and caspase (3/7)-activation. Finally, direct cell-polymer contact assays were conducted. Ungrafted amine-modified polymer backbone yielded IC(50) values in the range of 0.05-10mg/ml. Generally higher toxicities were observed with an increasing degree of amine substitution. Amine substituents could be ranked as diethylaminopropylamine (DEAPA)poly(vinyl alcohol) (PVA) backbones. To attenuate cytotoxic effects DEAPA-PVA backbones were grafted with biodegradable PLGA side chains at molecular ratios of 1:10 and 1:20. Cytotoxicity of extracts of these polymers was significantly lower compared to ungrafted polymers possibly caused by shielding of polycationic backbone with hydrophobic PLGA side chains. P(33)-20, a polymer containing a sufficiently high degree of amine substitution could serve as a lead candidate for further investigations. In conclusion, structure-toxicity relationships could be established and shielding the polycationic backbone using PLGA side chains seems to be a promising strategy meriting further investigations.

  3. Biomedical applications of stereoregular poly(vinyl alcohol) micro- and nanoparticles

    NASA Astrophysics Data System (ADS)

    Lyoo, Won Seok; Kim, Joon Ho; Kim, Sam Soo; Ghim, Han Do

    2002-11-01

    Syndiotactic poly(vinyl alcohol) (PVA)/poly(vinyl pivalate/vinyl acetate) (P(VPi/VAc)) and atactic PVA/PVAc micro- and nanoparticles with skin/core structure have been prepared by heterogeneous saponification of P(VPi/VAc) and PVAc micro- and nanoparticles. Especially, to prepare P(VPi/VAc) and PVAc microparticles having various particle sizes and uniform particle size distribution, vinyl pivalate (VPi)/vinyl acetate (VAc) and VAc were suspension-polymerized using a low-temperature initiator, 2,2"-azobis(2,4-dimethylvaleronitrile). P(VPi/VAc) particles are promising precursor of stereoregular PVA embolic materials which can be introduced through catheters in the management of gastrointestinal bleeders, arteriovenous malformations, hemangiomas, and traumatic rupture of blood vessels. Monodisperse and/or nearly monodisperse P(VPi/VAc) and PVAc microparticles with various particle diameters were obtained by controlling suspension polymerization conditions. Monodisperse P(VPi/VAc) and PVAc microparticles having various particle sizes were partially saponified in the heterogeneous system. PVA/P(VPi/VAc) and PVA/PVAc microparticles having various tacticity and degree of saponification were produced by controlling various polymerization and saponification conditions. The coating of stereoregular PVA micro- and nanoparticles for drug release experiments was conducted with the strepo-avidin-alkaline phosphatase conjugate in variable conditions of pH value, coating buffer, and reaction temperature. Protein-coated syndiotactic PVA micro- and nanoparticles, which does not crosslinking, were more superior to controllability of drug release, durability, and dimensional stability to water and blood than atactic one.

  4. X-ray structures of precursors of styrylpyridine-derivatives used to obtain 4-((E)-2-(pyridin-2-yl)vinyl)benzamido-TEMPO: synthesis and characterization.

    PubMed

    Soriano-Moro, Guillermo; Percino, María Judith; Sánchez, Ana Laura; Chapela, Víctor Manuel; Cerón, Margarita; Castro, María Eugenia

    2015-04-02

    The synthesis and characterization of the precursor isomers trans-4-(2-(pyridin-2-yl)vinylbenzaldehyde (I), trans-4-(2-(pyridin-4-yl)vinylbenzaldehyde (II), trans-4-(2-(pyridin-2-yl)vinylbenzoic acid (III) and (E)-4-(2-(pydridin-4-yl)vinylbenzoic acid (IV) are reported. These compounds were prepared in order to obtain trans-4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO (V). Compounds I and II were obtained by using a Knoevenagel reaction in the absence of a condensing agent and solvent. Oxidation of the aldehyde group using the Jones reagent afforded the corresponding acid forms III and IV. A condensation reaction with 4-amino-TEMPO using oxalyl chloride/DMF/CH2Cl2 provided the 4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO. Single crystals of compounds I, II and III were obtained and characterized by X-ray diffraction. Compound I belongs to space group P2(1)/c, a = 12.6674(19) Å, b = 7.2173(11) Å, c = 11.5877(14) Å, b = 97.203(13)° and the asymmetric unit was Z = 4, whereas compound II was in the space group P2(1), with a = 3.85728(9) Å, b = 10.62375(19) Å, c = 12.8625(2) Å, b = 91.722 (2)° and the asymmetric unit was Z = 2. Compound III crystallized as single colorless needle crystals, belonging to the monoclinic system with space group P2(1), with Z = 2, with a = 3.89359(7) Å, b = 17.7014(3) Å, c = 8.04530(12) Å, b = 94.4030 (16)°. All compounds were completely characterized by IR, (1)H-NMR, EI-MS and UV-Vis.

  5. Microencapsulation of lobster carotenoids within poly(vinyl alcohol) and poly(D,L-lactic acid) membranes.

    PubMed

    Sun, Z M; Poncelet, D; Conway, J; Neufeld, R J

    1995-01-01

    The use of natural pigments such as lobster carotenoids in fish feed formulations offers advantages over the use of the synthetic alternatives. Microencapsulation of the pigments, with or without the addition of antioxidants to the formulation, may be of benefit in terms of stabilizing pigment colour. In the present study, lobster carotenoids were extracted from lobster shell into petroleum ether and microencapsulated by phase separation and salt coacervation within (poly vinyl alcohol) and poly(vinyl alcohol)/poly(D,L-lactic acid) membranes. Spherical microcapsules, with smooth, thin and resilient membranes were obtained with mean diameters ranging from 50 to 150 microns, depending on the membrane material, and source of pigment. The microcapsules were pink-orange in colour, and colour stability was followed spectrophotometrically. Enhanced stability was observed in both membrane materials, in comparison to the non-encapsulated control. Rates of discoloration were determined under a variety of storage conditions, including the absence of light, reduced temperatures and under nitrogen atmosphere. The best stability of lobster carotenoids was observed under a nitrogen atmosphere within PVA/PLA membranes, representing an 11-fold enhancement of pigment stability in comparison to the controls. Under ambient conditions, the enhancement in pigment stability was approximately 6-fold. The optimum concentration of PVA during microencapsulation was 3-4%, and the microencapsulated pigments appeared most stable under acidic conditions. The rate of discoloration appeared independent of pigment concentration.

  6. Effect of Low Pressure Nitrogen DC Plasma on Optical Properties of Biaxial-Oriented Polypropylene (BOPP), Poly Methyl Methacrylate (PMMA) and Poly Vinyl Chloride (PVC) Films

    NASA Astrophysics Data System (ADS)

    Mortazavi, S. H.; Ghoranneviss, M.; Faryadras, S.

    2012-06-01

    In this paper properties of Biaxial-Oriented Polypropylene, Poly Vinyl Chloride and Poly Methyl Methacrylate samples treated by DC glow discharge of N2 plasma have been investigated by UV-Vis_NIR spectrophotometer. It was found that plasma treatment change chemical structure of polymer surfaces. In addition, absorption coefficient, refractive index and extinction coefficient of all treated samples have been slightly changed.

  7. Chemically imaging the effects of the addition of nanofibrillated cellulose on the distribution of poly(acrylic acid) in poly(vinyl alcohol)

    Treesearch

    Craig Clemons; Julia Sedlmair; Barbara Illman; Rebecca Ibach; Carol Hirschmugl

    2013-01-01

    The distribution of poly(acrylic acid) (PAA) in model laminates of nanocellulose and poly(vinyl alcohol) (PVOH) was investigated by FTIR chemical imaging. The method was effective in spatially discerning the three components of the composite. PAA can potentially improve the performance of nanocellulose reinforced PVOH by not only crosslinking the PVOH matrix but also...

  8. Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes.

    PubMed

    Jensen, Bettina E B; Hosta-Rigau, Leticia; Spycher, Philipp R; Reimhult, Erik; Städler, Brigitte; Zelikin, Alexander N

    2013-08-07

    Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.

  9. Surface grafting of vinyl-functionalized poly(fluorene)s via thiol-ene click chemistry.

    PubMed

    Davis, Andrew R; Carter, Kenneth R

    2014-04-22

    Thiol-ene chemistry is used for the surface grafting of vinyl-functionalized poly(fluorene) derivatives onto substrates containing free surface thiol groups. The grafting reaction proceeds in a matter of minutes under UV irradiation without photoinitiator, and the resulting surface-bound, solvent-impervious conjugated polymers retain their characteristic optoelectronic properties. End-chain grafted poly(fluorene)s reach greater surface densities than their side-chain grafted counterparts and show less blue-shifting of photoluminescence upon grafting, suggesting that chain end-grafted conjugated polymers experience less disruption of their extended conjugation and adopt a more brush-like surface conformation. Surface grafted poly(fluorene)s showed facile photopatterning, and thin film transistors with semiconducting polymers directly grafted to the dielectric layer showed performances directly comparable to conventional self-assembled layers of performance-improving alkylsilanes.

  10. Synthesis and Luminescent Property of Poly(9-(3-vinyl-phenyl)-anthracene).

    PubMed

    Lee, Sunmi; Shin, Hwangyu; Park, Beom-Soo Michael; Lee, Jaehyun; Park, Jongwook

    2015-07-01

    Polymer light-emitting diodes (PLEDs) have attracted much attention from academia and industry field because of their various applications such as large area flat-panel displays and lightings. In this paper, we suggest new blue emitting polymer based on anthracene, Poly(9-(3-Vinyl-phenyl)-anthracene) (PVPA). From NMR data, vinyl group protons were disappeared and aromatic protons showed broad proton peaks because of polymer characteristics. PVPA had film property well and it exhibited vivid PL maximum values of 431, 455, 482 nm and broad PL spectrum. Three dopants for green, red, yellow were used to PVPA, all energy transfer was happened well. By using rubrene dopant of yellow emission, doped film provided white PL.

  11. Preparation of poly(vinyl alcohol)/kaolinite nanocomposites via in situ polymerization

    SciTech Connect

    Jia Xin; Li Yanfeng Zhang Bo; Cheng Qiong; Zhang Shujiang

    2008-03-04

    Poly(vinyl alcohol)/kaolinite intercalated nanocomposites (Kao-PVA) were prepared via in situ intercalation radical polymerization. Vinyl acetate (VAc) was intercalated into kaolinite by a displacement method using dimethyl sulfoxide/kaolinite (Kao-DMSO) as the intermediate. Then, PVAc/kaolinite (Kao-PVAc) was obtained via radical polymerization with benzoyl peroxide (BPO) as initiator. Last, PVAc/kaolinite was saponified via direct-hydrolysis with NaOH solution in order to obtain PVA/kaolinite nanocomposites, which was characterized by Fourier-Transformation spectroscopy (FTIR), wide X-ray diffraction (WXRD) and transmission electron microscopy (TEM). Their differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results of the obtained PVA/kaolinite suggested that the thermal properties had an obvious improvement.

  12. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

    DOE PAGES

    Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; ...

    2016-03-11

    The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly-(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligandsmore » (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42 3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Lastly, adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.« less

  13. Modification of poly(vinylidene fluoride) ultrafiltration membranes with poly(vinyl alcohol) for fouling control in drinking water treatment.

    PubMed

    Du, Jennifer R; Peldszus, Sigrid; Huck, Peter M; Feng, Xianshe

    2009-10-01

    A commercial poly(vinylidene fluoride) flat sheet membrane was modified by surface coating with a dilute poly(vinyl alcohol) (PVA) aqueous solution followed by solid-vapor interfacial crosslinking. The resulting PVA layer increased membrane smoothness and hydrophilicity and resulted in comparable pure water permeation between the modified and unmodified membranes. Fouling tests using a 5 mg/L protein solution showed that a short period of coating and crosslinking improved the anti-fouling performance. After 18 h ultrafiltration of a surface water with a TOC of approximately 7 mg C/L, the flux of the modified membrane was twice as high as that of the unmodified membrane. The improved fouling resistance of the modified membrane was related to the membrane physiochemical properties, which were confirmed by pure water permeation, X-ray photoelectron spectroscopy, and contact angle, zeta potential and roughness measurements.

  14. Poly(ethylene glycol)-graft-poly(vinyl acetate) single-chain nanoparticles for the encapsulation of small molecules.

    PubMed

    Bartolini, Arianna; Tempesti, Paolo; Resta, Claudio; Berti, Debora; Smets, Johan; Aouad, Yousef G; Baglioni, Piero

    2017-02-08

    Amphiphilic poly(ethylene glycol)-graft-poly(vinyl acetate) copolymers with a low degree of grafting undergo self-folding in water driven by hydrophobic interactions, resulting in single-chain nanoparticles (SCNPs) possessing a hydrodynamic radius of about 10 nm. A temperature scan revealed a lower critical solution temperature (LCST)-type phase behavior. In addition, SAXS data collected close to the LCST showed that these SCNPs aggregate into one-dimensional elongated objects, preferentially. With respect to the typical linear complex-structured polymer chains, this material is ideally suited for industrial and/or biomedical applications because of its simple molecular architecture and persistence of SCNPs up to 100 mg mL(-1). The so-obtained single-chain globular particles are able to swell upon loading with small hydrophobic molecules therefore promoting solubilization of flavors or drugs, which could be of interest in the food and pharmaceutical industry.

  15. Polydopamine-coated electrospun poly(vinyl alcohol)/poly(acrylic acid) membranes as efficient dye adsorbent with good recyclability.

    PubMed

    Yan, Jiajie; Huang, Yunpeng; Miao, Yue-E; Tjiu, Weng Weei; Liu, Tianxi

    2015-01-01

    Free-standing poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) membranes with polydopamine (PDA) coating were prepared based on the combination of electrospinning and self-polymerization of dopamine. This is a facile, mild, controllable, and low-energy consumption process without any rigorous restriction to reactive conditions. Benefiting from the high specific surface area of electrospun membranes and the abundant "adhesive" functional groups of polydopamine, the as-prepared membranes exhibit efficient adsorption performance towards methyl blue with the adsorption capacity reaching up to 1147.6 mg g(-1). Moreover, compared to other nanoparticle adsorbents, the as-prepared self-standing membrane is highly flexible, easy to operate and retrieve, and most importantly, easy to elute, and regenerate, which enable its potential applications in wastewater treatment. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Novel conducting polymer electrolyte biosensor based on poly(1-vinyl imidazole) and poly(acrylic acid) networks.

    PubMed

    Arslan, Ahu; Kiralp, Senem; Toppare, Levent; Bozkurt, Ayhan

    2006-03-14

    Biosensor construction and characterization studies of poly(acrylic acid) (PAA) and poly(1-vinyl imidazole) (PVI) complex systems have been carried out. The biosensors were prepared by mixing PAA with PVI at several stoichiometric ratios, x (molar ratio of the monomer repeat units). The enzyme, invertase, was entrapped in the PAA/PVA interpenetrating polymer networks during complexation. Modifications were made on the PAA/PVI conducting polymer electrolyte matrixes to improve the stability and performance of the polymer electrolyte-based enzyme biosensor. The maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) were investigated for the immobilized invertase. The temperature and pH optimization, operational stability, and shelf life of the polymer electrolyte biosensor were also examined.

  17. Sulfonated poly(ether sulfone)s containing pyridine moiety for PEMFC.

    PubMed

    Jang, Hohyoun; Islam, Md Monirul; Lim, Youngdon; Hossain, Md Awlad; Cho, Younggil; Joo, Hyunho; Kim, Whangi; Jeon, Heung-Seok

    2014-10-01

    Sulfonated poly(ether sulfone)s with varied degree of sulfonation (DS) were prepared via post-sulfonation of synthesized pyridine based poly(ether sulfone) (PPES) using concentrated sulfuric acid as sulfonating agent. The DS was varied with different mole ratio of 4,4'-(2,2-diphenylethenylidene)diphenol, DHTPE in the polymer unit. PPES copolymers were synthesized by direct polycondensation of pyridine unit with bis-(4-fluorophenyl)-sulfone, 4, 4'-sulfonyldiphenol and DHTPE. The structure of the resulting PPES copolymer membranes with different sulfonated units were studied by 1H NMR spectroscopy and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymer with water. The ion exchange capacity (IEC) and proton conductivity were evaluated according to the increase of DS. The water uptake (WU) of the resulting membranes was in the range of 17-58%, compared to that of Nafion 211 28%. The membranes provided proton conductivities of 65-95 mS/cm in contrast to 103 mS/cm of Nafion 211.

  18. Electrospun nano-fibre mats with antibacterial properties from quaternised chitosan and poly(vinyl alcohol).

    PubMed

    Ignatova, Milena; Starbova, Kirilka; Markova, Nadya; Manolova, Nevena; Rashkov, Iliya

    2006-09-04

    Nano-fibres containing quaternised chitosan (QCh) have been successfully prepared by electrospinning of QCh solutions mixed with poly(vinyl alcohol) (PVA). The average fibre diameter is in the range of 60-200 nm. UV irradiation of the composite electrospun nano-fibrous mats containing triethylene glycol diacrylate as cross-linking agent has resulted in stabilising of the nano-fibres against disintegration in water or water vapours. Microbiological screening has demonstrated the antibacterial activity of the photo-cross-linked electrospun mats against Staphylococcus aureus and Escherichia coli. The obtained nano-fibrous electrospun mats are promising for wound-healing applications.

  19. Catechol-derivatized poly(vinyl alcohol) as a coating molecule for magnetic nanoclusters

    NASA Astrophysics Data System (ADS)

    Burnand, David; Monnier, Christophe A.; Redjem, Anthony; Schaefer, Mark; Rothen-Rutishauser, Barbara; Kilbinger, Andreas; Petri-Fink, Alke

    2015-04-01

    Surface functionalization of superparamagnetic iron oxide nanoparticles (SPIONs) remains indispensable in promoting colloidal stability and biocompatibility. We propose a well-defined and characterized synthesis of a new catechol-functionalized RAFT (reversible addition-fragmentation chain transfer) poly(vinyl alcohol) polymer, which can be anchored onto hydrophobic SPIONs via a one-pot emulsion ligand exchange process. Both single and clustered nanoparticles are obtained and can be separated from each other. As clustered SPIONs are receiving increasing attention, this new macroligand might be of considerable interest for both basic and applied sciences.

  20. Effect of borax concentration on the structure of Poly(Vinyl Alcohol) gels

    NASA Astrophysics Data System (ADS)

    Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

    2012-06-01

    Poly(Vinyl Alcohol) hydrogels cross-linked with varying concentrations of borax have been studied using Small-Angle Neutron Scattering and X-Ray Diffraction. The intensity of scattering increases with borax concentration from 1 mg/ml up to 2 mg/ml and falls thereafter for 4 mg/ml, increasing again for a concentration of 10 mg/ml. The mesoscopic structural changes that cause these trends in the SANS data are in keeping with the variations in the X-ray diffraction patterns pertaining to structures within the PVA chains.

  1. Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification

    NASA Astrophysics Data System (ADS)

    Wada, Yuki; Seko, Noriaki; Nagasawa, Naotsugu; Tamada, Masao; Kasuya, Ken-ichi; Mitomo, Hiroshi

    2007-06-01

    Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.

  2. Novel synthesis and DC electrical studies of polyindole/poly(vinyl acetate) composite films

    NASA Astrophysics Data System (ADS)

    Bhagat, D. J.; Dhokane, G. R.

    2015-01-01

    Novel one pot synthesis of polyindole/poly(vinyl acetate) composite films was prepared chemically. The monomer indole was polymerized using oxidant cupric chloride. As-synthesized composites were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The DC conductivity measurements were done through two probe technique. The DC conductivity value was found to be 8.648 × 10-6 S/cm at 383 K. The transference number measurement shows that ionic conductivity was dominant over electronic conductivity.

  3. Photochromic and microstructural properties of methyl orange doped poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Bhajantri, R. F.; Sali, Renuka; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Rathod, Sunil G.

    2013-02-01

    The effect of Methyl Orange (MO) dye on microstructural, optical and fluorescence properties of the polymer Poly(vinyl alcohol) (PVA) is studied. The FTIR study shows the appearance of new peaks indicates the interaction of MO with PVA. The UV-Vis study shows three absorption regions with the first two shows red shift and the third one shows blue shift and hence correspondingly three optical energy band gaps. In fluorescence study, it is observed that the intensity increases with increasing wavelength. These results are understood by invoking the hydrogen bonding and hydrophobic interaction between PVA and MO, forms the charge transfer complex (CTC).

  4. Chemical modification of poly (vinyl chloride) sheet with thiourea for cell study

    NASA Astrophysics Data System (ADS)

    Monika, Mishra, R. R.; Jaiswal, S.; Kapusetti, G.; Misra, N.

    2013-06-01

    Plasticized poly (vinyl chloride) has been used as biomaterial to make medical equipment. An appropriate reaction situation by temperature at 60-85°C for the surface modification of PVC sheet with sodium thiourea has been investigated. Although, the use of a phase-transfer catalyst (Tetra butyl ammonium hydrogen sulphate-TBHAS) makes it feasible for the nucleophilic substitution reaction to take place, the morphology of the film is changed by the reaction, leading to a loss in both surface smoothness and transparency of the film. According to this study, the reaction with sodium thiourea occurs consistently through the sheets, and modified surface have antibacterial capacity.

  5. Physical properties of gamma irradiated poly(vinyl alcohol) hydrogel preparations

    NASA Astrophysics Data System (ADS)

    Mondino, A. V.; González, M. E.; Romero, G. R.; Smolko, E. E.

    1999-08-01

    Poly(vinyl alcohol) films from 15% w/w aqueous solutions and a thickness of 0.2 mm were selected for this study. The films were first humidified and then acetalized and/or gamma irradiated. Then, their physical properties were tested. Tensile strength of the hydrogel films reached its maximum value in samples irradiated with a 80 kGy dose, in the case of acetalized films the dose necessary for maximum tensile strength was only 40 kGy. The combination of acetalization with formaldehyde and gamma radiation produced an elastic hydrogel with good tackiness and excellent mechanical and thermal strength.

  6. Fabrication of poly(vinyl carbazole) waveguides by oxygen ion implantation

    NASA Astrophysics Data System (ADS)

    Ghailane, Fatima; Manivannan, Gurusamy; Knystautas, Émile J.; Lessard, Roger A.

    1995-08-01

    Polymer waveguides were fabricated by ion implantation involving poly(vinyl carbazole) films. This material was implanted by oxygen ions (O ++ ) of energies ranging from 50 to 250 keV. The ion doses varied from 1010 to 1015 ions / cm2. The conventional prism-film coupler method was used to determine the waveguiding nature of the implanted and unimplanted films. The increase of the surface refractive index in the implanted layer has been studied by measuring the effective refractive index (neff) for different optical modes. Electron spectroscopy chemical analysis measurements were also performed to assess the effect of ion implantation on the polymer matrix.

  7. Composition dependent structural modulations in transparent poly(vinyl alcohol) hydrogels.

    PubMed

    Gupta, Siddhi; Pramanik, Ashit Kumar; Kailath, Ansu; Mishra, Trilochan; Guha, Avijit; Nayar, Suprabha; Sinha, Arvind

    2009-11-01

    Transparent and stable Poly(vinyl alcohol) hydrogels were synthesized from polymer aqueous solution without resorting to a mixed solvent such as dimethyl sulfoxide and water. Contrary to the reported methods involving hydrogen bond induced physical crosslinking by repeated freeze-thawing at -20 degrees C, the present process demonstrates the gelation taking place at relatively higher temperature, i.e. 0 degrees C. While maintaining transparency in all the synthesized hydrogels, the present paper reports systematic structural and morphological variations in the hydrogels as a function of polymer concentration.

  8. Soluble functionalized carbon nanotube/poly(vinyl alcohol) nanocomposite as the electrode for glucose sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Nanyan; Xie, Jining; Varadan, Vijay K.

    2006-02-01

    Carbon nanotubes exhibit excellent properties which make them a good candidate as the electrode material for bioapplications. A soluble functionalized carbon nanotube/poly(vinyl alcohol) nanocomposite was synthesized via esterification reactions. The obtained nanocomposite exhibits significantly improved electrical conductivity. Nanocomposite-based electrodes were prepared by a thick film technique and their performances were electrochemically characterized. After enzyme immobilization, they can be used as biosensors for glucose detection. Preliminary results show these nanotube composite-based electrodes exhibit good electrochemical performance for glucose detection. Comparison was also made between graphite and nanocomposite-based electrodes.

  9. Toxicity of the pyrolysis and combustion products of poly(vinyl chlorides): a literature assessment

    SciTech Connect

    Huggett, C.; Levin, B.C.

    1986-04-01

    Poly(vinyl chlorides) (PVC) constitute a major class of synthetic plastics. Many surveys of the voluminous literature have been performed. The report reviews the literature published in English from 1969 through 1984 and endeavors to be more interpretive than comprehensive. PVC compounds, in general, are among the more fire-resistant common organic polymers, natural or synthetic. The major products of thermal decomposition include hydrogen chloride, benzene, and unsaturated hydrocarbons. In the presence of oxygen, carbon monoxide, carbon dioxide and water are included among the common combustion products. The main toxic products from PVC fires are hydrogen chloride (a sensory and pulmonary irritant) and carbon monoxide (an asphyxiant).

  10. Synergistic toughening of bioinspired poly(vinyl alcohol)-clay-nanofibrillar cellulose artificial nacre.

    PubMed

    Wang, Jianfeng; Cheng, Qunfeng; Lin, Ling; Jiang, Lei

    2014-03-25

    Inspired by the layered aragonite platelet/nanofibrillar chitin/protein ternary structure and integration of extraordinary strength and toughness of natural nacre, artificial nacre based on clay platelet/nanofibrillar cellulose/poly(vinyl alcohol) is constructed through an evaporation-induced self-assembly technique. The synergistic toughening effect from clay platelets and nanofibrillar cellulose is successfully demonstrated. The artificial nacre achieves an excellent balance of strength and toughness and a fatigue-resistant property, superior to natural nacre and other conventional layered clay/polymer binary composites.

  11. Impact behaviour of an innovative plasticized poly(vinyl chloride) for the automotive industry

    NASA Astrophysics Data System (ADS)

    Bernard, C. A.; Bahlouli, N.; Wagner-Kocher, C.; Ahzi, S.; Rémond, Y.

    2015-09-01

    Plasticized poly(vinyl chloride) (PPVC) is widely used in the automotive industry in the design of structural parts for crashworthiness applications. Thus, it is necessary to study and understand the influence of the mechanical response and mechanical properties of PPVC over a wide range of strain rate, from quasi-static to dynamic loadings. The process is also investigated using different sample thicknesses. In this work, the strain rate effect of a new PPVC is investigated over a wide range of strain rates at three temperatures and for three thicknesses. A modelling of the yield stress is also proposed. The numerical prediction is in good agreement with the experimental results.

  12. Transparent poly(vinyl acetate)-silica gels by a sol-gel process

    NASA Astrophysics Data System (ADS)

    Wojcik, Anna B.; Klein, Lisa C.

    1993-12-01

    Rod shaped silica-poly(vinyl acetate) (PVAc) gels have been prepared by a sol gel process. In situ polymerization of tetraethoxysilane (TEOS) was accomplished in the presence of low molecular weight PVAc by dissolving various amounts of PVAc in a mixture of TEOS, ethanol, water and hydrochloric acid (HCl). Gelation of this mixture was carried out between room temperature and slightly above. Silica-PVAc rods recovered from cylindrical molds were homogeneous and transparent. Gels with weight percents of PVAc ranging from 2% to 50% were prepared. Silica-PVAc gels have higher flexure strengths, less brittle character and improved water durability in comparison with pure sol- gel silica.

  13. Characterization of nanocellulose reinforced semi-interpenetrating polymer network of poly(vinyl alcohol) & polyacrylamide composite films.

    PubMed

    Mandal, Arup; Chakrabarty, Debabrata

    2015-12-10

    Semi-interpenetrating polymer network (semi-IPN) of poly(vinyl alcohol)/polyacrylamide was reinforced with various doses of nanocellulose. The different composite films thus prepared were characterized with respect to their mechanical, thermal, morphological and barrier properties. The composite film containing 5 wt.% of nanocellulose showed the highest tensile strength. The semi-interpenetrating polymer network of poly(vinyl alcohol)/polyacrylamide; and its various composites with nanocellulose were almost identical in their thermal stability. Each of the composites however exhibited much superior stability with respect to the linear poly(vinyl alcohol) and crosslinked polyacrylamide. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited phase separated morphology where agglomerates of nanocellulose were found to be dispersed in the matrix of the semi-IPN. The moisture vapor transmission rate (MVTR) was the lowest for the film containing 5 wt.% of nanocellulose.

  14. Novel Poly(3-hydroxybutyrate-g-vinyl alcohol) Polyurethane Scaffold for Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Reyes, Adriana Pétriz; Martínez Torres, Ataúlfo; Carreón Castro, Ma. Del Pilar; Rodríguez Talavera, José Rogelio; Muñoz, Susana Vargas; Aguilar, Víctor Manuel Velázquez; Torres, Maykel González

    2016-08-01

    The design of new synthetic grafted poly(3-hydroxybutyrate) as composite 3D-scaffolds is a convenient alternative for tissue engineering applications. The chemically modified poly(3-hydroxybutyrate) is receiving increasing attention for use as biomimetic copolymers for cell growth. As of yet, these copolymers cannot be used efficiently because of the lack of good mechanical properties. Here, we address this challenge, preparing a composite-scaffold of grafted poly(3-hydroxybutyrate) polyurethane for the first time. However, it is unclear if the composite structure and morphology can also offer a biological application. We obtained the polyurethane by mixing a polyester hydroxylated resin with polyisocyanate and the modified polyhydroxyalkanoates. The results show that the poly(3-hydroxybutyrate) grafted with poly(vinyl alcohol) can be successfully used as a chain extender to form a chemically-crosslinked thermosetting polymer. Furthermore, we show a proposal for the mechanism of the polyurethane synthesis, the analysis of its morphology and the ability of the scaffolds for growing mammalian cells. We demonstrated that astrocytes isolated from mouse cerebellum, and HEK293 can be cultured in the prepared material, and express efficiently fluorescent proteins by adenoviral transduction. We also tested the metabolism of Ca2+ to obtain evidence of the biological activity.

  15. Novel Poly(3-hydroxybutyrate-g-vinyl alcohol) Polyurethane Scaffold for Tissue Engineering

    PubMed Central

    Reyes, Adriana Pétriz; Martínez Torres, Ataúlfo; Carreón Castro, Ma. del Pilar; Rodríguez Talavera, José Rogelio; Muñoz, Susana Vargas; Aguilar, Víctor Manuel Velázquez; Torres, Maykel González

    2016-01-01

    The design of new synthetic grafted poly(3-hydroxybutyrate) as composite 3D-scaffolds is a convenient alternative for tissue engineering applications. The chemically modified poly(3-hydroxybutyrate) is receiving increasing attention for use as biomimetic copolymers for cell growth. As of yet, these copolymers cannot be used efficiently because of the lack of good mechanical properties. Here, we address this challenge, preparing a composite-scaffold of grafted poly(3-hydroxybutyrate) polyurethane for the first time. However, it is unclear if the composite structure and morphology can also offer a biological application. We obtained the polyurethane by mixing a polyester hydroxylated resin with polyisocyanate and the modified polyhydroxyalkanoates. The results show that the poly(3-hydroxybutyrate) grafted with poly(vinyl alcohol) can be successfully used as a chain extender to form a chemically-crosslinked thermosetting polymer. Furthermore, we show a proposal for the mechanism of the polyurethane synthesis, the analysis of its morphology and the ability of the scaffolds for growing mammalian cells. We demonstrated that astrocytes isolated from mouse cerebellum, and HEK293 can be cultured in the prepared material, and express efficiently fluorescent proteins by adenoviral transduction. We also tested the metabolism of Ca2+ to obtain evidence of the biological activity. PMID:27502732

  16. Blend miscibility of cellulose propionate with poly(N-vinyl pyrrolidone-co-methyl methacrylate).

    PubMed

    Sugimura, Kazuki; Teramoto, Yoshikuni; Nishio, Yoshiyuki

    2013-10-15

    The blend miscibility of cellulose propionate (CP) with poly(N-vinyl pyrrolidone-co-methyl methacrylate) (P(VP-co-MMA)) was investigated. The degree of substitution (DS) of CP used ranged from 1.6 to >2.9, and samples for the vinyl polymer component were prepared in a full range of VP:MMA compositions. Through DSC analysis and solid-state (13)C NMR and FT-IR measurements, we revealed that CPs of DS<2.7 were miscible with P(VP-co-MMA)s of VP≥~10mol% on a scale within a few nanometers, in virtue of hydrogen-bonding interactions between CP-hydroxyls and VP-carbonyls. When the DS of CP exceeded 2.7, the miscibility was restricted to the polymer pairs using P(VP-co-MMA)s of VP=ca. 10-40 mol%; the scale of mixing in the blends concerned was somewhat larger (ca. 5-20 nm), however. The appearance of such a "miscibility window" was interpretable as an effect of intramolecular repulsion in the copolymer component. Results of DMA and birefringence measurements indicated that the miscible blending of CP with the vinyl polymer invited synergistic improvements in thermomechanical and optical properties of the respective constituent polymers. Additionally, it was found that the VP:MMA composition range corresponding to the miscibility window was expanded by modification of the CP component into cellulose acetate propionate.

  17. Multi-stage Mass Spectrometry of Poly(vinyl pyrrolidone) and Its Vinyl Succinimide Copolymer Formed upon Exposure to Sodium Hypochlorite

    PubMed Central

    Fouquet, Thierry; Torimura, Masaki; Sato, Hiroaki

    2016-01-01

    The degradation routes of poly(vinyl pyrrolidone) (PVP) exposed to sodium hypochlorite (bleach) have been previously investigated using chemical analyses such as infrared spectroscopy. So far, no reports have proposed mass spectrometry (MS) as an alternative tool despite its capability to provide molecular and structural information using its single stage electrospray (ESI) or matrix assisted laser desorption ionization (MALDI) and multi stage (MSn) configurations, respectively. The present study thus reports on the characterization of PVP after its exposure to bleach by high resolution MALDI spiralTOF-MS and Kendrick mass defect analysis providing clues as to the formation of a vinyl pyrrolidone/vinyl succinimide copolymeric degradation product. A thorough investigation of the fragmentation pathways of PVP adducted with sodium and proton allows one main route to be described—namely the release of the pyrrolidone pendant group in a charge remote and charge driven mechanism, respectively. Extrapolating this fragmentation pathway, the oxidation of vinyl pyrrolidone into vinyl succinimide hypothesized from the single stage MS is validated by the detection of an alternative succinimide neutral loss in lieu of the pyrrolidone release in the ESI-MSn spectra of the aged PVP sample. It constitutes an example of application of multi-stage mass spectrometry for the characterization of the degradation of polymeric samples at a molecular level. PMID:27800293

  18. Poly(vinyl alcohol) Physical Hydrogels: Matrix-Mediated Drug Delivery Using Spontaneously Eroding Substrate

    PubMed Central

    2016-01-01

    Poly(vinyl alcohol) hydrogels have a long and successful history of applications in biomedicine. Historically, these matrices were developed to be nondegradable—limiting their utility to applications as permanent implants. For tissue engineering and drug delivery, herein we develop spontaneously eroding physical hydrogels based on PVA. We characterize in detail a mild, noncryogenic method of producing PVA physical hydrogels using poly(ethylene glycol) as a gelating agent, and investigate PVA molar mass as a means to define the kinetics of erosion of these biomaterials. PVA hydrogels are characterized for associated inflammatory response in adhering macrophages, antiproliferative effects mediated through delivery of cytotoxic drugs to myoblasts, and pro-proliferative activity achieved via presentation of conjugated growth factors to endothelial cells. Together, these data present a multiangle characterization of these novel multifunctional matrices for applications in tissue engineering and drug delivery mediated by implantable biomaterials. PMID:26958864

  19. Integrated antifouling and bactericidal polymer membranes through bioinspired polydopamine/poly(N-vinyl pyrrolidone) coating

    NASA Astrophysics Data System (ADS)

    Wang, Xianghong; Yuan, Shuaishuai; Shi, Dean; Yang, Yingkui; Jiang, Tao; Yan, Shunjie; Shi, Hengchong; Luan, Shifang; Yin, Jinghua

    2016-07-01

    Polypropylene (PP) non-woven has been widely used as wound dressing; however, the hydrophobic nature of PP can initiate bacterial attachment and subsequent biofilm formation. Herein, we propose a facile approach to functionalize PP non-woven with poly(ethylene glycol) (PEG) and poly(N-vinyl pyrrolidone)-iodine complex (PVP-I). PVP and PEG were successively tethered onto PP non-woven surface via versatile bioinspired dopamine (DA) chemistry, followed by complexing iodine with PVP moieties. It was demonstrated through the field emission scanning electron microscope (SEM) and spread plate method that the as-modified PP non-woven integrated both antifouling property of PEG for suppressing bacterial adhesion, and bactericidal property of PVP-I for killing the few adherent bacteria. Meanwhile, it could greatly resist platelet and red blood cell adhesion. The integrated antifouling and bactericidal PP non-woven surfaces might have great potential in various wound dressing applications.

  20. Structural analysis, and antioxidant and antibacterial properties of chitosan-poly (vinyl alcohol) biodegradable films.

    PubMed

    Hajji, Sawssen; Chaker, Achraf; Jridi, Mourad; Maalej, Hana; Jellouli, Kemel; Boufi, Sami; Nasri, Moncef

    2016-08-01

    The development and characterization of biodegradable blend films based on chitosan and poly (vinyl alcohol) for possible use in a variety of biological activities are reported. Fourier transform infrared spectroscopy (FTIR) spectra of chitosan-poly (vinyl alcohol) (Ch/PVA) films showed characteristics peaks shifting to a lower frequency range due to hydrogen bonding between -OH of PVA and -NH2 of chitosan. The chitosan and PVA polymers presented good compatibility. The morphology study of chitosan and composite films showed a compact and homogenous structure. The tensile strength and elongation at break increased with PVA content. In fact, the highest tensile strength and elongation at break (53.58 MPa and 454 %) occurs with pure PVA film. The results showed that PVA incorporation in the blends contributes to increase the intermolecular interactions, thus improving the mechanical properties. In addition, the prepared films demonstrated high antioxidant activities monitored by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging, reducing power, and β-carotene bleaching activity. Nevertheless, PVA addition reduced antioxidant and antibacterial activities against Gram-positive and Gram-negative bacteria tested.

  1. Viscometric Studies in Dilute Solution Mixtures of Chitosan and Microcrystalline Chitosan with Poly(vinyl alcohol).

    PubMed

    Lewandowska, Katarzyna

    2013-01-01

    The viscosity behavior of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B), such as chitosan/poly(vinyl alcohol) (Ch/PVA) and microcrystalline chitosan/poly(vinyl alcohol) (MCCh/PVA), have been investigated at 25 °C. The intrinsic viscosity and the viscosity interaction parameter of each polymer in 0.1 mol·dm(-3) CH3COOH/0.2 mol·dm(-3) NaCl solution as well as the ternary systems (polymer A/polymer B/solvent) have been determined and have served for estimation of the miscibility of different polymer mixtures by means of the method of classical dilution. By comparing the experimental and ideal viscosity data it is clearly seen that the satisfaction of the miscibility criterion depends on the definition of the ideal parameter [Formula: see text]. If the [Formula: see text] parameter is defined according to the Krigbaum-Wall criterion and Garcia criterion, the investigated blends of Ch/PVA satisfy the miscibility criterion. In the case of MCCh/PVA blends, the polymeric components show poor miscibility. Additionally, the viscosity results show that the degree of miscibility depends on the molecular weight of chitosan and on the degree of PVA hydrolysis.

  2. Swelling and mechanical properties of glycol chitosan/poly(vinyl alcohol) IPN-type superporous hydrogels.

    PubMed

    Park, Hyojin; Kim, Dukjoon

    2006-09-15

    Glycol chitosan/poly(vinyl alcohol) interpenetrating polymer network type superporous hydrogels were prepared using a gas foaming/freeze-drying method. The effect of the molecular weight of the strengthener, poly(vinyl alcohol) (PVA), on the swelling and mechanical behavior of the superporous hydrogels was investigated. The introduction of a small amount of high molecular weight PVA significantly enhanced the mechanical strength but slightly reduced the swelling capacity. The freezing/thawing (F/T) drying process had a significant effect on the physical properties of the glycol chitosan/PVA superporous hydrogels, because hydrogen bonds were formed between the PVA molecules as a result of the number of F/T cycles. The swelling ratio decreased but the mechanical strength increased with increasing freezing time. However, this effect was not as strong as the number of F/T cycles. The differential scanning calorimetry was used to examine how the thermal behavior associated with the hydrogen bond-induced crystalline structure was affected by the F/T process.

  3. Bioseparation of papain from Carica papaya latex by precipitation of papain-poly (vinyl sulfonate) complexes.

    PubMed

    Braia, Mauricio; Ferrero, Maximiliano; Rocha, María Victoria; Loureiro, Dana; Tubio, Gisela; Romanini, Diana

    2013-09-01

    The formation of insoluble complexes between enzymes and polyelectrolytes is a suitable technique for isolating these biomolecules from natural sources, because it is a simple and rapid technique that allows the concentration of the protein. This technique can be used in most purification protocols at the beginning of the downstream process. The aim of this investigation is to isolate papain from Carica papaya latex by precipitation of insoluble complexes between this enzyme and poly (vinyl sulfonate). The papain-poly (vinyl sulfonate) complex was insoluble at pH lower than 6, with a PVS/PAP stoichiometric ratio of 1:279. Ionic strength affected the complex formation. The presence of the polymer increased the enzymatic activity and protected the enzyme from autodegradation. The optimal conditions for the formation of insoluble papain-polyelectrolyte complex formation were applied to C. papaya latex and a high recovery was obtained (around 86%) and a purification factor around 2. This method can be applied as an isolation method of papain from C. papaya latex or as a first step in a larger purification strategy. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. How To Learn and Have Fun with Poly(Vinyl Alcohol) and White Glue

    NASA Astrophysics Data System (ADS)

    de Zea Bermudez, V.; Passos de Almeida, P.; Féria Seita, J.

    1998-11-01

    The general behavior of Newtonian, shear-thinning, shear-thickening, thixotropic, negative thixotropic, and viscoelastic fluids is characterized and briefly discussed in terms of existing theoretical models. Whenever possible, examples of these types of fluids taken from everyday life are given for better understanding. This theoretical introduction is the basis for same, simple, and inexpensive laboratory work employing no special glassware and generally done by pairs of students. The work involves the synthesis of two well-known viscoelastic materials displaying unique properties: poly(vinyl alcohol) (PVA) and white glue, a poly(vinyl acetate)-based emulsion. The students are asked to perform a series of representative mechanical tests on both gels and to describe their observations in full detail. In particular, they are expected to recognize and identify the origin of the intriguing behaviors found (elasticity, spinability, self-siphoning effect, die-swell effect, Weissenberg effect). The tests include the preparation of fibers by extrusion, introducing concepts such as water solubility, hydrogen bonding, and glass transition temperature. The long list of questions, which ideally should be answered at the end of the laboratory work, allows the students to apply the new concepts acquired.

  5. Cosolvent gel-like materials from partially hydrolyzed poly(vinyl acetate)s and borax.

    PubMed

    Angelova, Lora V; Terech, Pierre; Natali, Irene; Dei, Luigi; Carretti, Emiliano; Weiss, Richard G

    2011-09-20

    A gel-like, high-viscosity polymeric dispersion (HVPD) based on cross-linked borate, partially hydrolyzed poly(vinyl acetate) (xPVAc, where x is the percent hydrolysis) is described. Unlike hydro-HVPDs prepared from poly(vinyl alcohol) (PVA) and borate, the liquid portion of these materials can be composed of up to 75% of an organic cosolvent because of the influence of residual acetate groups on the polymer backbone. The effects of the degree of hydrolysis, molecular weight, polymer and cross-linker concentrations, and type and amount of organic cosolvent on the rheological and structural properties of the materials are investigated. The stability of the systems is explored through rheological and melting-range studies. (11)B NMR and small-angle neutron scattering (SANS) are used to probe the structure of the dispersions. The addition of an organic liquid to the xPVAc-borate HVPDs results in a drastic increase in the number of cross-linked borate species as well as the agglomeration of the polymer into bundles. These effects result in an increase in the relaxation time and thermal stability of the networks. The ability to make xPVAc-borate HVPDs with very large amounts of and rather different organic liquids, with very different rheological properties that can be controlled easily, opens new possibilities for applications of PVAc-based dispersions. © 2011 American Chemical Society

  6. Effects of nanoscale dispersion in the dielectric properties of poly(vinyl alcohol)-bentonite nanocomposites.

    PubMed

    Hernández, María C; Suárez, N; Martínez, Luis A; Feijoo, José L; Lo Mónaco, Salvador; Salazar, Norkys

    2008-05-01

    We investigate the effects of clay proportion and nanoscale dispersion in the dielectric response of poly(vinyl alcohol)-bentonite nanocomposites. The dielectric study was performed using the thermally stimulated depolarization current technique, covering the temperature range of the secondary and high-temperature relaxation processes. Important changes in the secondary relaxations are observed at low clay contents in comparison with neat poly(vinyl alcohol) (PVA). The high-temperature processes show a complex peak, which is a combination of the glass-rubber transition and the space-charge relaxations. The analysis of these processes shows the existence of two segmental relaxations for the nanocomposites. Dielectric results were complemented by calorimetric experiments using differential scanning calorimetry. Morphologic characterization was performed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM and XRD results show a mixture of intercalated and exfoliated clay dispersion in a trend that promotes the exfoliated phase as the bentonite content diminishes. Dielectric and morphological results indicate the existence of polymer-clay interactions through the formation of hydrogen bounds and promoted by the exfoliated dispersion of the clay. These interactions affect not only the segmental dynamics, but also the secondary local dynamics of PVA.

  7. Poly(vinyl alcohol) cryogel phantoms for use in ultrasound and MR imaging

    NASA Astrophysics Data System (ADS)

    Surry, K. J. M.; Austin, H. J. B.; Fenster, A.; Peters, T. M.

    2004-12-01

    Poly(vinyl alcohol) cryogel, PVA-C, is presented as a tissue-mimicking material, suitable for application in magnetic resonance (MR) imaging and ultrasound imaging. A 10% by weight poly(vinyl alcohol) in water solution was used to form PVA-C, which is solidified through a freeze-thaw process. The number of freeze-thaw cycles affects the properties of the material. The ultrasound and MR imaging characteristics were investigated using cylindrical samples of PVA-C. The speed of sound was found to range from 1520 to 1540 m s-1, and the attenuation coefficients were in the range of 0.075-0.28 dB (cm MHz)-1. T1 and T2 relaxation values were found to be 718-1034 ms and 108-175 ms, respectively. We also present applications of this material in an anthropomorphic brain phantom, a multi-volume stenosed vessel phantom and breast biopsy phantoms. Some suggestions are made for how best to handle this material in the phantom design and development process.

  8. Deep ultraviolet photoresist based on tungsten polyoxometalates and poly(vinyl alcohol) for bilayer photolithography

    SciTech Connect

    Carls, J.C.; Argitis, P.; Heller, A. )

    1992-03-01

    In this paper a negative tone deep ultraviolet resist, a mixture of phosphotungstic acid and poly(vinyl alcohol) is described. This resist has {lt}100 mJ cm{sup {minus}2} sensitivity and resolves {le}0.3 {mu}m features. Even though the photochemistry involves chemical amplification, the exposed patterns are stable and the process tolerates hours between the exposure and the post-bake steps. The resist is spun from an aqueous solutio, and its wet processing is also aqueous. This resist is used in a bilayer scheme, where advantage is taken of both the resistance of the tungsten oxide to oxygen plasmas and its easy stripping in fluorine-containing plasmas. Because poly(vinyl alcohol) is intrisincally a wetting agent, pinhole-free resist films of {approximately}1000 {Angstrom} thickness can be spun. These thin coatings provide sufficient oxygen plasma etch resistance to allow patterning of a thick 1.5 {mu}m novolac planarizing layer underneath the resist.

  9. Preparation and characterization of reactive blends of poly(lactic acid), poly(ethylene-co-vinyl alcohol), and poly(ethylene-co-glycidyl methacrylate)

    SciTech Connect

    Warangkhana, Phromma; Rathanawan, Magaraphan; Jana Sadhan, C.

    2015-05-22

    The ternary blends of poly(lactic acid) (PLA), poly(ethylene-co-vinyl alcohol) (EVOH), and poly(ethylene-co-glycidyl methacrylate) (EGMA) were prepared. The role of EGMA as a compatibilizer was evaluated. The weight ratio of PLA:EVOH was 80:20 and the EGMA loadings were varied from 5-20 phr. The blends were characterized as follows: thermal properties by differential scanning calorimetry, morphology by scanning electron microscopy, and mechanical properties by pendulum impact tester, and universal testing machine. The glass transition temperature of PLA blends did not change much when compared with that of PLA. The blends of PLA/EGMA and EVOH/EGMA showed EGMA dispersed droplets where the latter led to poor impact properties. However, the tensile elongation at break and tensile toughness substantially increased upon addition of EGMA to blends of PLA and EVOH. It was noted in tensile test samples that both PLA and EVOH domains fibrillated significantly to produce toughness.

  10. Preparation and characterization of reactive blends of poly(lactic acid), poly(ethylene-co-vinyl alcohol), and poly(ethylene-co-glycidyl methacrylate)

    NASA Astrophysics Data System (ADS)

    Warangkhana, Phromma; Jana Sadhan, C.; Rathanawan, Magaraphan

    2015-05-01

    The ternary blends of poly(lactic acid) (PLA), poly(ethylene-co-vinyl alcohol) (EVOH), and poly(ethylene-co-glycidyl methacrylate) (EGMA) were prepared. The role of EGMA as a compatibilizer was evaluated. The weight ratio of PLA:EVOH was 80:20 and the EGMA loadings were varied from 5-20 phr. The blends were characterized as follows: thermal properties by differential scanning calorimetry, morphology by scanning electron microscopy, and mechanical properties by pendulum impact tester, and universal testing machine. The glass transition temperature of PLA blends did not change much when compared with that of PLA. The blends of PLA/EGMA and EVOH/EGMA showed EGMA dispersed droplets where the latter led to poor impact properties. However, the tensile elongation at break and tensile toughness substantially increased upon addition of EGMA to blends of PLA and EVOH. It was noted in tensile test samples that both PLA and EVOH domains fibrillated significantly to produce toughness.

  11. In vitro anticoagulant activity of polyanionic graft chains modified poly(vinyl alcohol) particles

    NASA Astrophysics Data System (ADS)

    Li, Rong; Wu, Guozhong; Cai, Ximing; Ye, Yin

    2017-05-01

    Poly(acrylic acid), poly(sodium styrenesulfonate), and poly(acrylic acid-co-sodium styrenesulfonate) chains were immobilized onto poly(vinyl alcohol) (PVA) particles via a facile γ-ray simultaneous irradiation induced graft polymerization technique, which were confirmed by the attenuated total reflection Fourier transform infrared spectroscopy and the high swelling ratios of modified PVA particles. The effects of absorbed dose, dose rate, Cu2+ concentration and monomer concentration on the degree of grafting (DG) of PVA particles were investigated to find out a feasible process for preparing polyanionic chains graft-modified PVA particles. The clotting time results illustrated that both PVA-g-PAA and PVA-g-PSSS particles presented excellent anticoagulant activity, and the activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) were effectively prolonged with the increase of DGAA and DGSSS, respectively. Furthermore, the anticoagulant activity of PVA-g-PSSS samples was more efficient than that of PVA-g-PAA samples. However, the anticoagulant effect of PVA-g-P(AA-co-SSS) samples was different from that of PVA-g-PAA and PVA-g-PSSS samples, and was similar to that of heparin, mainly elongating the APTT and TT. This might be due to both of them containing the same negative-charged groups. Additionally, the grafted PVA particles were all non-hemolytic, showing good blood compatibility.

  12. Preparation of poly(vinyl alcohol)-grafted graphene oxide/poly(vinyl alcohol) nanocomposites via in-situ low-temperature emulsion polymerization and their thermal and mechanical characterization

    NASA Astrophysics Data System (ADS)

    Zhang, Shengchang; Liu, Pengqing; Zhao, Xiangsen; Xu, Jianjun

    2017-02-01

    An in-situ polymerization combined with chemical grafting modification method for preparing Poly(vinyl alcohol)-grafted graphene oxide/Poly(vinyl alcohol) (PVA-g-GO/PVA) nanocomposites was reported. Firstly, Poly(vinyl acetate)-grafted graphene oxide/Poly(vinyl acetate) nanocomposites were prepared, and then the PVA-g-GO/PVA nanocomposites could be obtained through alcoholysis reaction. X-ray photoelectron spectrometer and fourier-transform infrared spectrometer confirmed that the PVAc or PVA chains were successfully grafted to GO sheets during in-situ polymerization and alcoholysis. And the results from transmission electron microscopy, scanning electron microscopy and X-ray diffraction showed that the well compatibility and homogenous dispersion of PVA-g-GO in PVA matrix could be achieved. Differential scanning calorimetric, thermogravimetry analysis and tensile test were employed to study the thermal and mechanical properties of the PVA-g-GO/PVA nanocomposites. The results indicated that a 53% improvement of tensile strength and a 36% improvement of Young's modulus were achieved by addition of 0.5 wt% of GO sheets. And the glass transition temperature of PVA-g-GO/PVA nanocomposites was increased, and their thermal stability and crystallization degree were both decreased. Due to well dispersion of fillers and strong interfacial interactions at the filler-matrix interface, in-situ polymerization combined with chemical grafting modification was a good choice to prepare graphene/PVA nanocomposite with excellent mechanical properties.

  13. Poly(vinyl alcohol)/poly(acrylic acid) hydrogel coatings for improving electrode-neural tissue interface.

    PubMed

    Lu, Yi; Wang, Dingfang; Li, Tao; Zhao, Xueqing; Cao, Yuliang; Yang, Hanxi; Duan, Yanwen Y

    2009-09-01

    A major problem which hinders the applications of neural prostheses is the inconsistent performance caused by tissue responses during long-term implantation. The study investigated a new approach for improving the electrode-neural tissue interface. Hydrogel poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks (PVA/PAA IPNs) were synthesized and tailored as coatings for poly(dimethylsiloxane) (PDMS) based neural electrodes with the aid of plasma pretreatment. Changes in the electrochemical impedance and maximum charge injection (Q(inj)) limits of the coated iridium oxide microelectrodes were negligible. Protein adsorption on PDMS was reduced by approximately 85% after coating. In the presence of nerve growth factor (NGF), neurite extension of rat pheochromocytoma (PC12) cells was clearly greater on PVA/PAA IPN films than on PDMS substrates. Furthermore, the tissue responses of PDMS implants coated with PVA/PAA IPN films were studied by 6-week implantation in the cortex of rats, which found that the glial fibrillary acidic protein (GFAP) immunoreactivity in animals (n=8) receiving coated implants was significantly lower (p<0.05) compared to that of uncoated implants (n=7) along the entire distance of 150 microm from the outer skirt to the implant interface. The coated film remained on the surface of the explanted implants, confirmed by scanning electron microscopy (SEM). All of these suggest the hydrogel coating is feasible and favorable to neural electrode applications.

  14. Exploration of CO2-Philicity of Poly(vinyl acetate-co-alkyl vinyl ether) through Molecular Modeling and Dissolution Behavior Measurement.

    PubMed

    Hu, Dongdong; Sun, Shaojun; Yuan, Pei-Qing; Zhao, Ling; Liu, Tao

    2015-09-24

    Hydrocarbon CO2-philes are of great interest for use in expanding CO2 applications as a green solvent. In this work, multiscale molecular modeling and dissolution behavior measurement were both applied to explore CO2-philicity of the poly(vinyl acetate) (PVAc)-based copolymer. Introduction of a favorable comonomer, i.e., vinyl ethyl ether (VEE), could significantly reduce the polymer-polymer interaction on the premise that the polymer-CO2 interaction was not weakened but enhanced. The ab initio calculated interaction of the model molecules with CO2 demonstrated that the ether group in VEE or VBE was the suitable CO2-philic segment. From the molecular dynamics (MD) simulations of polymer/CO2 systems, the interaction energy and Flory-Huggins parameter (χ12) of poly(VAc-alt-VEE)/CO2 supported that poly(VAc-alt-VEE) possessed better CO2-philicity than PVAc. The dissolution behaviors of the synthesized poly(VAc-co-alkyl vinyl ether) copolymers in CO2 showed the best CO2-phile had the VEE content of about 34 mol %. The MD simulations also indicated that the interaction of random poly(VAc-co-VEE) containing about 30 mol % VEE with CO2 was the strongest and the χ12 was the smallest in these polymer/CO2 systems. Not only could the VEE monomer reduce the polymer-polymer interaction, but it could also enhance the polymer-CO2 interaction with an optimized composition. Introducing a suitable comonomer with a certain composition might be a promising strategy to form the synergistic effect of polymer-polymer interaction and polymer-CO2 interaction for screening the hydrocarbon CO2-philes.

  15. Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes

    NASA Astrophysics Data System (ADS)

    Jensen, Bettina E. B.; Hosta-Rigau, Leticia; Spycher, Philipp R.; Reimhult, Erik; Städler, Brigitte; Zelikin, Alexander N.

    2013-07-01

    Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus

  16. Graphene functionalized with poly(vinyl alcohol) as a Pickering stabilizer for suspension polymerization of poly(methyl methacrylate).

    PubMed

    Erdenedelger, Gansukh; Dao, Trung Dung; Jeong, Han Mo

    2016-08-15

    Two types of thermally reduced graphenes (TRGs) having different lateral sizes were non-covalently modified with poly(vinyl alcohol) to endow water-dispersibility. The modified TRGs were examined as Pickering stabilizers for the suspension polymerization of methyl methacrylate (MMA). They were effective graphene-based Pickering stabilizers for the system with almost all of the polymerized composite microparticles having a regular spherical shape. The particle size of the composite microparticles was tunable by the size or the amount of modified TRG used as stabilizer. The almost perfect core-shell structure of the composite microparticles effectively enhanced the thermal stability of the core PMMA. In addition, when the core-shell microparticles were compression molded into a monolith, the obtained composite exhibited an ultra-low percolation threshold of electrical conductivity of around 0.04vol%.

  17. A novel biobased plasticizer of epoxidized cardanol glycidylether: Synthesis and application in soft poly(vinyl chloride) films

    USDA-ARS?s Scientific Manuscript database

    A novel plasticizer derived from cardanol, epoxied cardanol glycidyl ether (ECGE), was synthesized and characterized by 1H-NMR and 13C-NMR. Effects of the ECGE combined with dioctyl phthalate (DOP), a commercial plasticizer, in soft poly(vinyl chloride) (PVC) films were studied. Dynamic mechanical a...

  18. Preparation and characterization of electrospun core sheath nanofibers from multi-walled carbon nanotubes and poly(vinyl pyrrolidone).

    PubMed

    Miao, Jianjun; Miyauchi, Minoru; Dordick, Jonathan S; Linhardt, Robert J

    2012-03-01

    Electrospinning is a versatile technique to prepare polymer fibers in nano to micrometer size ranges using very high electrostatic fields. Electrospun nanofibers with tunable porosity and high specific surface area have various applications, including chromatographic supports for protein separation, biomedical devices, tissue engineering and drug delivery matrices, and as key components in solar cells and supercapacitors. Unspinnable materials such as nanoparticles, nanorods, nanotubes or rigid conducting polymers can also be electrospun into fibers through co-axial electrospinning. In this study, we have prepared core-sheath nanofibers utilizing co-axial electrospinning. The core portion of these electrospun fibers consists of multi-walled carbon nanotubes and the sheath portion is poly(vinyl pyrrolidone) (PVP). Various morphologies were obtained by changing both core and sheath solution concentrations. The core-sheath nanofibers were characterized by scanning electron microscopy and transmission electron microscopy, to confirm core-sheath morphology, thermogravimetric analysis, and mechanical strength testing. The electrical conductivity of the surfaces of poly(vinyl pyrrolidone) fibers and poly(vinyl pyrrolidone)-multi-walled nanotube fibers were both 10(-15) S/m. The highest bulk conductivity observed for the poly(vinyl pyrrolidone)-multi-walled nanotube fibers was 1.2 x 10(-3) S/m.

  19. Poly(vinyl alcohol) composite films with high percent elongation prepared from amylose-fatty ammonium salt inclusion complexes

    USDA-ARS?s Scientific Manuscript database

    Amylose inclusion complexes prepared from cationic fatty ammonium salts and jet-cooked high amylose starch were combined with poly(vinyl alcohol) (PVOH) to form glycerol-plasticized films. Their tensile properties were compared with similar films prepared previously with analogous anionic fatty acid...

  20. Time-resolved spectroscopy of solid poly/1-vinyl naphthalene/ following electron beam pulse radiolysis - Pulse radiolytic studies on polymers

    NASA Technical Reports Server (NTRS)

    Coulter, D. R.; Liang, R. H.; Di Stefano, S.; Moacanin, J.; Gupta, A.

    1982-01-01

    Transient emission studies following pulse radiolysis of solid poly(1-vinyl naphthalene) show existence of excited monomers and two excimers. Quenching experiments indicate that excimers are not formed directly by recombination of ions but probably by trapping of migrating monomeric excitation in preformed traps whose density is approximately one in 1000.

  1. Poly(vinyl alcohol)/cellulose nanofibril hybrid aerogels with an aligned microtubular porous structure and their composites with polydimethylsiloxane

    Treesearch

    Tianliang Zhai; Qifeng Zheng; Zhiyong Cai; Lih-Sheng Turng; Hesheng Xia; Shaoqin Gong

    2015-01-01

    Superhydrophobic poly(vinyl alcohol) (PVA)/ cellulose nanofibril (CNF) aerogels with a unidirectionally aligned microtubular porous structure were prepared using a unidirectional freeze-drying process, followed by the thermal chemical vapor deposition of methyltrichlorosilane. The silanized aerogels were characterized using various techniques including scanning...

  2. On the design of in situ forming biodegradable parenteral depot systems based on insulin loaded dialkylaminoalkyl-amine-poly(vinyl alcohol)-g-poly(lactide-co-glycolide) nanoparticles.

    PubMed

    Packhaeuser, C B; Kissel, T

    2007-11-06

    The feasibility to generate in situ forming parenteral depot systems from insulin loaded dialkylaminoalkyl-amine-poly(vinyl alcohol)-g-poly(lactide-co-glycolide) nanoparticles, was investigated. Biodegradable nanoparticles formed polymeric semi-solid depots upon injection into isotonic phosphate buffered saline (PBS) with no additional initiators. Nanoparticles (NP) prepared from the different amine-modified polyesters displayed a pronounced positive zeta-potential of >25 mV. Diethylaminopropyl-amine-poly(vinyl alcohol)-g-poly(lactide-co-glycolide) (DEAPA(68)-PVAL-g-PLGA(1:20)), diethylaminoethyl-amine-poly(vinyl alcohol)-g-poly(lactide-co-glycolide) (DEAEA(33)-PVAL-g-PLGA(1:20)), and dimethylaminopropyl-amine-poly(vinyl alcohol)-g-poly(lactide-co-glycolide) (DMAPA(33)-PVAL-g-PLGA(1:20)), formed in situ depots by an ion-mediated aggregation with subsequent fusion of nanoparticles, related to a decreased glass transition temperature in the presence of PBS. Moreover, two factors, namely, polymer and insulin-nanocomplex concentration, were evaluated using a response surface design with respect to nanoparticles formation and insulin loading. Nanoparticles and implants were investigated by atomic force microscopy (AFM). The in vitro release from implants loaded with 2% insulin was carried out in a flow trough cell and quantified by high performance liquid chromatography (HPLC). The release showed a triphasic profile with an initial burst, pore diffusion and diffusion from the swollen matrix over more than two weeks. Insulin distribution in the implants during the release was followed by confocal laser scanning microscopy (CLSM). These findings combined with the protection of the model peptide against competitive macromolecules and the possibility to get dry powders by lyophilization make these nanoparticles-based depots suitable candidates for the design of controlled release devices for bioactive macromolecules.

  3. Manipulating the morphologies of poly(vinyl alcohol) block copolymer surfactants

    NASA Astrophysics Data System (ADS)

    Repollet-Pedrosa, Milton H.

    Amphiphilic block copolymers (ABCs) are macromolecules containing well-defined hydrophilic and hydrophobic segments that self-assemble into nanoscale aggregates such as spherical and cylindrical micelles and vesicles, when dispersed in block-selective solvents. ABCs possess a miniscule critical micelle concentration, which results in kinetically trapped and persistent assemblies in solution with slow chain exchange between aggregates. This makes them useful as rheological modifiers for personal care products, enhanced oil recovery, and drug delivery formulations. Their utility in many of these applications is crucially dependent on the ability to control the micellar morphologies that they adopt in selective solvents. Triggering ABC micellar morphological transformations, i.e. from spherical to cylindrical micelles, is important for generating "on-demand" stimuli-responsive morphologies that control the aggregate morphology and the bulk solution properties in any given application. In this thesis, we develop the straightforward synthesis of biodegradable and biocompatible ABCs comprised of poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA), with narrow molecular distributions and variable yet well-defined compositions. These block copolymer amphiphiles readily form spherical micelles in aqueous dispersions. We demonstrate that the addition of a water-soluble poly(ethylene oxide) (PEO) homopolymer to these dispersions results in a rapid transformation of these spherical micelles into cylindrical micelles. Dilution of these cylindrical micelles with water induces their reversion to spherical micelles. Our results indicate that the reversible morphology change depends sensitively on the PEO homopolymer concentration and molecular weight, as well as the length of the PVA corona block of the micelles. Through a series of quantitative 1H NMR studies, we found that the preferential partitioning of PEO homopolymer into the PVAc micellar core drives this morphological

  4. Adsorption of poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) polymers on zinc, zinc oxide, iron, and iron oxide surfaces.

    PubMed

    Seifert, Susan; Simon, Frank; Baumann, Giesela; Hietschold, Michael; Seifert, Andreas; Spange, Stefan

    2011-12-06

    The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-bis-(1,10-phenanthroline)-iron(II) (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b']difuran-2,6-dione (2), and 4-tert-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ(3)-thiazoline (3) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-co-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-co-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-co-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions. © 2011 American Chemical Society

  5. Rheological behaviour of irradiated wound dressing poly(vinyl pyrrolidone) hydrogels

    NASA Astrophysics Data System (ADS)

    Lugão, Ademar B.; Rogero, Sizue O.; Malmonge, Sônia M.

    2002-03-01

    The use of hydrogels as biomaterials has increased lately. Poly(vinyl pyrrolidone) (PVP) is an example of polymer hydrogels applied for the synthesis of hydrogel to be used in different biomedical applications. This paper describes a study on rheological properties of PVP hydrogels obtained by gamma radiation techniques. PVP hydrogels were obtained by gamma radiation of PVP water solutions with different radiation doses. It was studied the influence of additives such as poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO) and glycerol on the rheological behaviour of the gel. The rheological behaviour of hydrogel samples was characterized by measuring the shear storage modulus ( G') under dynamic shear loading. Besides this, sterility and cytotoxicity tests were performed. The study on rheological behaviour of hydrogels showed that G' of PVP gels change according to the additive used. Glycerol increases the fluidity of the gel. The influence of PEG depends on the amount and on its molecular mass. The increase on PEG amount and molecular mass cause a decrease of G' and an increase in the crosslinking density of PVP hydrogel network. The use of high molecular weight PEO allows the increase of the elasticity of the PVP gels.

  6. Nafion/poly(1-vinyl imidazole) composite membranes for fuel cell application

    NASA Astrophysics Data System (ADS)

    Kim, Dukjoon

    2008-03-01

    A base monomer (1-vinyl imidazole, VIDz) was polymerized in Nafion^ 112 membrane by UV irradiation in order to reduce methanol permeability of the latter. With increasing content of poly 1-vinyl imidazole (PVI), equilibrium water uptake was decreased due to reduced size of hydrated ion cluster in the composite membrane as confirmed by a small angle X-ray scattering analysis. The electrochemical properties of the membrane such as ion conductivity, methanol permeability and electro-osmotic drag were also affected by equilibrium water uptake and hydrated pore size. Even a minute incorporation of the base polymer showed a significant effect on proton conductivity and methanol permeability. Methanol transport by electro-osmotic drag was evaluated by using relating equations and methanol permeability and limiting current density data obtained in this study. Although the absolute number of electro-osmotic drag was hard to determine, the trend of change could be studied in relation to bulk-like water in composite membranes. This novel composite membrane exhibited an increased cell performance compared with a plain Nafion membrane due to reduced methanol crossover rate.

  7. 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.

  8. Relaxation phenomena in poly(vinyl alcohol)/fumed silica affected by interfacial water.

    PubMed

    Gun'ko, V M; Pissis, P; Spanoudaki, A; Zarko, V I; Nychiporuk, Y M; Andriyko, L S; Goncharuk, E V; Leboda, R; Skubiszewska-Zieba, J; Osovskii, V D; Ptushinskii, Y G

    2007-08-15

    Interaction of poly(vinyl alcohol) (PVA) with fumed silica was investigated in the gas phase and aqueous media using adsorption, broadband dielectric relaxation spectroscopy (DRS), thermally stimulated depolarization current (TSDC), infrared spectroscopy, thermal analysis, and one-pass temperature-programmed desorption (OPTPD) mass-spectrometry (MS) methods. PVA monolayer formation leads to certain textural changes in the system (after suspension and drying) because of strong hydrogen bonding of the polymer molecules to silica nanoparticles preventing strong interaction between silica particles themselves. This strong interaction promotes associative desorption of water molecules at lower temperatures than in the case of silica alone. Interaction of PVA with silica and residual water leads to depression of glass transition temperature (T(g)). There are three types of dipolar relaxations at temperatures lower and higher than the T(g) value. A small amount of adsorbed water leads to significant conductivity with elevating temperature.

  9. Spectroelectrochemical Studies on Quinacridone by Using Poly(vinyl alcohol) Coating as Protection Layer

    PubMed Central

    Enengl, Sandra; Enengl, Christina; Stadler, Philipp; Neugebauer, Helmut; Sariciftci, Niyazi Serdar

    2015-01-01

    Spectroscopic measurements in the infrared range combined with electrochemistry are a powerful technique for investigation of organic semiconductors to track changes during oxidation and reduction (p- and n-doping) processes. For these measurements it is important that the studied material, mostly deposited as a thin film on an internal reflection element, does not dissolve during this characterization. In this study we introduce a technique that allows infrared spectroelectrochemical characterization of films of these materials for the first time. In many cases so far this has been impossible, due to solubility in the oxidized and/or reduced form. This novel technique is shown on thin films of quinacridone by adding a protection layer of poly(vinyl alcohol) (PVA). PMID:26013836

  10. Asymmetric Polymer Particles with Anisotropic Curvatures by Annealing Polystyrene Microspheres on Poly(vinyl alcohol) Films.

    PubMed

    Tseng, Hsiao-Fan; Cheng, Ming-Hsiang; Jeng, Kai-Sheng; Li, Jia-Wei; Chen, Jiun-Tai

    2016-09-09

    Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self-assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Optimization of aceclofenac-loaded pectinate-poly(vinyl pyrrolidone) beads by response surface methodology.

    PubMed

    Nayak, Amit Kumar; Kalia, Samir; Hasnain, M Saquib

    2013-11-01

    The paper describes development of aceclofenac-loaded pectinate-poly(vinyl pyrrolidone) [PVP] beads through ionotropic-gelation. Effects of amount of pectin and PVP on drug encapsulation efficiency (DEE), and cumulative drug release at 6h (R6h) were optimized by using response surface methodology. The optimized beads showed DEE of 96.58 ± 4.15% and R6h of 41.62 ± 2.18% with controlled drug release pattern. FTIR spectroscopy analysis revealed possible intermolecular hydrogen bonding, which could be formed between C=O groups of PVP and -OH groups of pectin in these beads. The swelling of these beads were influenced by pH of the medium.

  12. Dynamics in poly vinyl alcohol (PVA) based hydrogel: Neutron scattering study

    NASA Astrophysics Data System (ADS)

    Prabhudesai, S. A.; Lawrence, Mathias B.; Mitra, S.; Desa, J. A. E.; Mukhopadhyay, R.

    2015-06-01

    Results of quasielastic neutron scattering measurements carried out on Poly Vinyl Alcohol (PVA) based hydrogels are reported here. PVA hydrogels are formed using Borax as a cross-linking agent in D2O solvent. This synthetic polymer can be used for obtaining the hydrogels with potential use in the field of biomaterials. The aim of this paper is to study the dynamics of polymer chain in the hydrogel since it is known that polymer mobility influences the kinetics of loading and release of drugs. It is found that the dynamics of hydrogen atoms in the polymer chain could be described by a model where the diffusion of hydrogen atoms is limited within a spherical volume of radius 3.3 Å. Average diffusivity estimated from the behavior of quasielastic width is found to be 1.2 × 10-5 cm2/sec.

  13. Poly(vinyl alcohol) physical hydrogels: new vista on a long serving biomaterial.

    PubMed

    Alves, Marie-Helene; Jensen, Bettina E B; Smith, Anton A A; Zelikin, Alexander N

    2011-10-10

    Poly(vinyl alcohol), PVA, and physical hydrogels derived thereof have an excellent safety profile and a successful history of biomedical applications. However, these materials are hardly in the focus of biomedical research, largely due to poor opportunities in nano- and micro-scale design associated with PVA hydrogels in their current form. In this review we aim to demonstrate that with PVA, a (sub)molecular control over polymer chemistry translates into fine-tuned supramolecular association of chains and this, in turn, defines macroscopic properties of the material. This nano- to micro- to macro- translation of control is unique for PVA and can now be accomplished using modern tools of macromolecular design. We believe that this strategy affords functionalized PVA physical hydrogels which meet the demands of modern nanobiotechnology and have a potential to become an indispensable tool in the design of biomaterials. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Electrospinning of carboxyethyl chitosan/poly(vinyl alcohol)/silk fibroin nanoparticles for wound dressings.

    PubMed

    Zhou, Yingshan; Yang, Hongjun; Liu, Xin; Mao, Jun; Gu, Shaojin; Xu, Weilin

    2013-02-01

    Composite nanofibrous membranes of water-soluble N-carboxyethyl chitosan/poly(vinyl alcohol)/silk fibroin nanoparticles were successfully fabricated by electrospinning. The composite nanofibers were subjected to detailed analysis by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). SEM results investigated that the morphology and diameter of the nanofibers were affected by silk fibroin nanoparticles content. XRD and DSC demonstrated that there was intermolecular hydrogen bonding among the molecules of carboxyethyl chitosan, silk fibroin and PVA. The crystalline microstructure of the electrospun fibers was not well developed. The indirect cytotoxicity assessments of the nanofibers were studied. The result showed the nanofibers had good biocompatibility. This novel electrospun matrix would be used as potential wound dressing for skin regeneration. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Studies of Poly(vinyl chloride) Based Endotracheal Tubes From the Microscopic to Macroscopic Scale

    NASA Astrophysics Data System (ADS)

    Brodie, Kristin; Ortiz, Christine

    2003-03-01

    The endotracheal tube (ET) is a polymeric conduit that forms a closed system of pulmonary ventilation that is most often used to allow delivery of air to critically ill patients via intubation. Currently used ETs cause a wide variety of clinical problems including laryngeal edema (inflammation), severe morbidity, and occasionally death. To investigate the origins of this behavior, mechanical, chemical, morphological, and biocompatibility characterization of injection-molded (Endotrol) tubes of poly(vinyl chloride) (PVC) containing 35 wtplasticizer was conducted. Experiments included fourier-transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, accelerated solvent extraction, uniaxial tensile testing, high-resolution force spectroscopy, atomic force microscopy, and plasticizer leaching. We intend for these studies to form the basis for future ET materials selection and design.

  16. Fabrication and Characterization of Graphene/Graphene Oxide-Based Poly(vinyl alcohol) Nanocomposite Membranes

    NASA Astrophysics Data System (ADS)

    Hieu, Nguyen Huu; Long, Nguyen Huynh Bach Son; Kieu, Dang Thi Minh; Nhiem, Ly Tan

    2016-05-01

    Graphene (GE)- or graphene oxide (GO)-based poly(vinyl alcohol) (PVA) nanocomposite membranes have been prepared by the solution blending method. Raman spectra and atomic force microscopy images confirmed that GE and GO were synthesized with average thickness of 0.901 nm and 0.997 nm, respectively. X-ray diffraction patterns indicated good exfoliation of GE or GO in the PVA matrix. Fourier-transform infrared spectra revealed the chemical fractions of the nanocomposite membranes. Differential scanning calorimetry results proved that the thermal stability of the nanocomposite membranes was enhanced compared with neat PVA membrane. Transmission electron microscopy images revealed good dispersion of GE or GO sheets in the PVA matrix with thickness in the range of 19 nm to 39 nm. As a result, good compatibility between GE or GO and PVA was obtained at 0.5 wt.% filler content.

  17. Mechanical and dielectric properties of carbon nanotubes/poly (vinyl alcohol) nanocomposites

    NASA Astrophysics Data System (ADS)

    Amrin, Sayed; Deshpande, V. D.

    2016-05-01

    In this work, two series of nanocomposites of poly(vinyl alcohol) (PVA) incorporated with multiwalled carbon nanotubes (MWNT) and carboxyl functionalized multiwalled carbon nanotubes (MWNT-COOH) were fabricated using solution-cast method and their tensile and dielectric properties were studied. Tensile tests were carried out on composite films of MWNT/PVA and MWNT-COOH/PVA for different loading levels. Results show that overall mechanical properties of the MWNT-COOH/PVA composite was greatly improved as compared to the MWNT/PVA film. The dielectric properties of nanocomposites were investigated in a frequency range from 0.1Hz to 10MHz at room temperature respectively. Compared to MWNT/PVA composites, higher dielectric constant and ac conductivity was achieved in MWNT-COOH/PVA nanocomposite, which can be well explained by the interfacial polarization effect.

  18. Electro-optical properties of poly(vinyl acetate)/polyindole composite film

    NASA Astrophysics Data System (ADS)

    Bhagat, D. J.; Bajaj, N. S.; Dhokane, G. R.

    2016-05-01

    In present work, electrical and optical properties of poly(vinyl acetate)/polyindole (PVAc/PIN) composite film are reported. The prepared composite was characterized via X-ray diffraction (XRD), UV-Vis spectroscopy and DC conductivity measurements. The polymer chain separation was determined using XRD analysis. An attempt has been made to study the temperature dependence of DC conductivity of PVAc/PIN composite in temperature range 308-373 K. The DC conductivity initially increases and reaches to 2.45×10-7 S/cm. The optical band gap value of composite is determined as 4.77 eV. The semiconducting nature of composite observed from electronic as well as optical band gap and Arrhenius behavior of DC plot.

  19. Fast dynamics in poly(vinyl chloride) below the glass transition: self and pair correlation functions

    NASA Astrophysics Data System (ADS)

    Moral, A.; Arbe, A.; Colmenero, J.

    2000-03-01

    In a previous work the incoherent scattering function of poly(vinyl chloride) (PVC) in the microscopic time range was successfully described in the frame of a model which assumes harmonic vibrations coexisting with relaxational contributions controlled by C-C torsional barriers. In the same frame the behaviour of the coherent scattering function well above the glass transition temperature Tg could also be interpreted. In this work, we investigate the applicability of such a model to coherent scattering of PVC below and around Tg. Within the experimental accuracy, the data can be well described starting from the results independently obtained from the study of the incoherent function. This gives additional support to the ideas involved in the proposed model.

  20. High-Strength Nanocomposite Aerogels of Ternary Composition: Poly(vinyl alcohol), Clay, and Cellulose Nanofibrils.

    PubMed

    Liu, Andong; Medina, Lilian; Berglund, Lars A

    2017-02-22

    Clay aerogels are foam-like materials with potential to combine high mechanical performance with fire retardancy. However, the compression strength of these aerogels is much lower than theoretically predicted values. High-strength aerogels with more than 95% porosity were prepared from a ternary material system based on poly(vinyl alcohol), montmorillonite clay platelets, and cellulose nanofibrils. A hydrocolloidal suspension of the three components was subjected to freeze-drying so that a low-density aerogel foam was formed. Cell structure was studied by field-emission scanning electron microscopy. Interactions at the molecular scale were observed by X-ray diffraction and Fourier transform infrared spectroscopy. Cross-linking was carried out using glutaraldehyde or borax, and moisture stability was investigated. These biobased ternary aerogels showed compression strength much better than that of previously studied materials and also showed strength higher than that of high-performance sandwich foam cores such as cross-linked polyvinyl chloride foams.

  1. Fabrication of thromboresistant multilayer thin film on plasma treated poly (vinyl chloride) surface.

    PubMed

    Tan, Qinggang; Ji, Jian; Zhao, Feng; Fan, De-Zeng; Sun, Fu-Yu; Shen, Jia-Cong

    2005-07-01

    Layer-by-layer deposited anticoagulant multilayer films were prepared on ammonia plasma treated poly (vinyl chloride) (PVC). Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and contact angle results revealed the presence of -NH2 on the ammonia plasma treated PVC surfaces and the layer-by-layer self-assembly process. The stability of multilayer film was studied with the radio labeled method. The remainder bovine serum albumin (BSA) in cross-linked 5(heparin/BSA) multilayer films dipped in phosphate buffered saline (PBS, pH 7.4) was more than 90% in 40 days. The static platelet adhesion result indicated the anticoagulant multilayer films deposited on the plasma treated PVC reduced platelet adhesion drastically and no thrombus forming. The plasma recalcification time revealed that the multilayer modified surfaces greatly prolonged the plasma recalcification time. Such an easy processing and shape-independent method may have good potential for surface modification of cardiovascular devices.

  2. Aqueous leaching of di-2-ethylhexyl phthalate and "green" plasticizers from poly(vinyl chloride).

    PubMed

    Kastner, Joshua; Cooper, David G; Marić, Milan; Dodd, Patrick; Yargeau, Viviane

    2012-08-15

    A method was developed to assess leaching of several poly(vinyl chloride) (PVC) plasticizers in aqueous media using gas chromatography (GC), and compared to a gravimetric standard test method (ASTM Method D1239). The GC method was a more direct measurement of plasticizer concentration in the aqueous phase. The leaching of commercial plasticizers, as well as several series of "green" candidate plasticizers, were assessed as a function of their molecular characteristics and compared to the industry standard PVC plasticizer, di-2-ethylhexyl phthalate (DEHP). It was found that plasticizers containing longer alkyl chains or non-polar branching emanating from polar structural units, increased the hydrophobicity of the molecule and reduced its aqueous leaching rate. Several "green" plasticizer candidates were found to minimize aqueous leaching to rates ten times below that of DEHP; notably dioctyl succinate (DOS), dihexyl maleate (DHM), methyl cyclohexyl diester (MCDE), diethylhexyl succinate (DEHS), hexanediol dibenzoate (C6), and the commercially available Hexamoll® DINCH.

  3. Anisotropic Poly(Vinyl Alcohol) Hydrogel: Connection Between Structure and Bulk Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hudson, Stephen; Hutter, Jeffrey; Millon, Leonardo; Wan, Wankei; Nieh, Mu-Ping

    2009-03-01

    Poly(vinyl alcohol) (PVA) hydrogels are formed from PVA solution by creation of physical cross-links during freeze/thaw cycling. By choosing a suitable freeze/thaw protocol and applying a strain during thermal processing, gels with permanent, anisotropic bulk mechanical properties matching those of cardiovascular tissues can be made, making them useful for applications ranging from artificial heart valves to vascular grafts. We have performed small- and ultra small-angle neutron scattering (SANS and USANS) measurements covering length scales from 2 nm to 10 μm, and modeled the structure as interconnected PVA blobs of size 20 to 50 nm arranged in fractal aggregates extending to at least 10 μm. Here, we discuss the relationship between the microstructure and bulk mechanical properties. Strength increases with the number of thermal cycles due to reinforcement of the small-scale gel phase, while anisotropy is due to elongation of the much larger fractal aggregates.

  4. Stiffness- and wettability-dependent myoblast cell compatibility of transparent poly(vinyl alcohol) hydrogels.

    PubMed

    Gupta, Siddhi; T, Greeshma; Basu, Bikramjit; Goswami, Sudipta; Sinha, Arvind

    2013-02-01

    This study reports the in vitro compatibility of muscle cells (C2C12 mouse myoblast cell line) with the transparent poly(vinyl alcohol) (PVA) hydrogels and the results are explained on the basis of surface wettability, crystallinity, and nanoscale elastic stiffness property. Nanoindentation was carried out with a maximum load of 100 μN for all the hydrogel compositions and the properties such as elastic stiffness, hardness and total work done during indentation were computed. The difference in cell viability as well as adhesion of cultured myoblast cells on the investigated hydrogel substrates were discussed in reference to the difference in the nanoscale elastic properties, crystallinity, and surface wettability. An important result has been that both elastic stiffness and surface wettability synergistically influence myoblast viability/adhesion on PVA hydrogels. Copyright © 2012 Wiley Periodicals, Inc.

  5. Novel synthesis of cobalt/poly vinyl alcohol/gamma alumina nanocomposite for catalytic application

    NASA Astrophysics Data System (ADS)

    Hatamie, Shadie; Ahadian, Mohammad Mahdi; Rashidi, Alimoradeh; Karimi, Ali; Akhavan, Omid

    2017-05-01

    In this manuscript, synthesis of cobalt/poly vinyl alcohol (PVA)/gamma alumina nanocomposite via a simple room temperature, as well as its catalyst performance were explored. Brunauer-Emmett-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were conducted. The surface area of the polymeric composite was obtained to be 280 m2/g. The cobalt loading on the nanocomposite was measured using inductivity couple plasma. Transmission electron microscopy analysis showed that the size of cobalt crystalline encapsulate inside the polymer was confined to 5 nm. Magnetic property analysis, using vibrating sample magnetometer, confirmed ferromagnetic nature of the composite. Thermo-gravimetric analyses were employed to explain the degradation process for the polymeric base nanocomposite. Temperature-programmed reduction was used to evaluate the structural form of cobalt oxide in nanocomposite. The catalysis activity was determined by Fischer-Tropsch synthesize, which showed a high catalyst selectivity to C2-C4 hydrocarbons.

  6. Polyurethane/poly(vinyl alcohol) hydrogel coating improves the cytocompatibility of neural electrodes

    PubMed Central

    Li, Mei; Zhou, Hai-han; Li, Tao; Li, Cheng-yan; Xia, Zhong-yuan; Duan, Yanwen Y.

    2015-01-01

    Neural electrodes, the core component of neural prostheses, are usually encapsulated in polydimethylsiloxane (PDMS). However, PDMS can generate a tissue response after implantation. Based on the physicochemical properties and excellent biocompatibility of polyurethane (PU) and poly(vinyl alcohol) (PVA) when used as coating materials, we synthesized PU/PVA hydrogel coatings and coated the surface of PDMS using plasma treatment, and the cytocompatibility to rat pheochromocytoma (PC12) cells was assessed. Protein adsorption tests indicated that the amount of protein adsorption onto the PDMS substrate was reduced by 92% after coating with the hydrogel. Moreover, the PC12 cells on the PU/PVA-coated PDMS showed higher cell density and longer and more numerous neurites than those on the uncoated PDMS. These results indicate that the PU/PVA hydrogel is cytocompatible and a promising coating material for neural electrodes to improve their biocompatibility. PMID:26889197

  7. Conducting hydrogels of tetraaniline-g-poly(vinyl alcohol) in situ reinforced by supramolecular nanofibers.

    PubMed

    Huang, Huabo; Li, Wan; Wang, Hong; Zeng, Xiaoping; Wang, Qin; Yang, Yajiang

    2014-02-12

    Novel conducting hydrogels (PVA-TA) with dual network structures were synthesized by the grafting reaction of tetraaniline (TA) into the main chains of poly(vinyl alcohol) and in situ reinforced by self-assembly of a sorbitol derivative as the gelator. The chemical structure of the PVA-TA hydrogels was characterized by using FT-IR and NMR. The mechanical strength of the PVA-TA hydrogels was strongly improved due to the presence of supramolecular nanofibers. For instance, the compressive and tensile strengths of supramolecular nanofiber-reinforced hydrogels were, respectively, 10 times and 5 times higher than those of PVA-TA hydrogels. Their storage modulus (G') and loss modulus (G″) were 5 times and 21 times higher than those of PVA-TA hydrogels, respectively. Cyclic voltammetry and conductivity measurements indicated that the electroactivity of reinforced hydrogels is not influenced by the presence of supramolecular nanofibers.

  8. Crystallization and hardening of poly(ethylene-co-vinyl acetate) mouthguards during routine use.

    PubMed

    Kuwahara, Ryoko; Tomita, Ryotaro; Ogawa, Natsumi; Nakajima, Kazunori; Takeda, Tomotaka; Uehara, Hiroki; Yamanobe, Takeshi

    2017-03-15

    Mouthguards (MGs) made from poly(ethylene-co-vinyl acetate) (EVA) are widely used in contact sports to prevent injuries such as breaking teeth and lip lacerations and to reduce brain concussion. However, the changes in morphology and the molecular mobility of EVA, which can affect its physical properties during practical usage, have not been precisely examined. Therefore, we attempted to determine the main factors which lead to changes in MG performance after one season of practical use by high school rugby players. Solid-state nuclear magnetic resonance (NMR) and pulse NMR measurements showed the hardening of MGs, which was associated with an increased crystallinity of the EVA resulting from prolonged usage. Furthermore, our data indicated that the increase in the relative amount of the crystalline phase may be primarily attributed to temperature fluctuations and repeated changes in pressure, which could cause the hardening of EVA and eventually diminish the protective ability of MGs.

  9. Fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibres by electrospinning

    NASA Astrophysics Data System (ADS)

    Junkasem, Jirawut; Rujiravanit, Ratana; Supaphol, Pitt

    2006-09-01

    The present contribution reports, for the first time, the successful fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) (PVA) nanocomposite nanofibres by electrospinning. The α-chitin whiskers were prepared from α-chitin flakes from shrimp shells by acid hydrolysis. The as-prepared chitin whiskers exhibited lengths in the range 231-969 nm and widths in the range 12-65 nm, with the average length and width being about 549 and 31 nm, respectively. Successful incorporation of the chitin whiskers within the as-spun PVA/chitin whisker nanocomposite nanofibres was verified by infrared spectroscopic and thermogravimetric methods. The incorporation of chitin whiskers within the as-spun nanocomposite fibre mats increased the Young's modulus by about 4-8 times over that of the neat as-spun PVA fibre mat.

  10. Enhanced mechanical properties and morphological characterizations of poly(vinyl alcohol) carbon nanotube composite films

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Tao, Xiaoming; Xue, Pu; Cheng, Xiaoyin

    2005-12-01

    Tensile tests were carried out on free-standing composite films of poly(vinyl alcohol) (PVA) and multiwall carbon nanotubes (MWNTs) for different loading levels. Results show that overall mechanical properties of the composite were greatly improved as compared to the neat PVA film. For PVA-based materials at significant high loading level such as 9.1 wt.% MWNTs, considerable increases in Young's modulus, tensile strength and toughness by factors of 4.5, 2.7 and 4.1, respectively, were achieved. Raman, SEM, TEM, and DSC techniques were used to evaluate the PVA/MWNTs composite system. Strong acid-modification of the pristine MWNTs and the subsequent ultrasonication processing allowed good distribution of the nanotubes in the matrix. SEM together with DSC result shows apparent good wetting of the nanotubes by the PVA matrix, which are supportive of good interfacial bonding between the modified carbon nanotubes and the hosting polymer matrix.

  11. Activation of Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol) using a Supramolecular Trigger†

    PubMed Central

    Phillips, Daniel J.; Congdon, Thomas R.; Gibson, Matthew I.

    2016-01-01

    Antifreeze (glyco)proteins (AF(G)Ps) have potent ice recrystallisation inhibition (IRI) activity – a desirable phenomenon in applications such as cryopreservation, frozen food and more. In Nature AF(G)P activity is regulated by protein expression levels in response to an environmental stimulus; temperature. However, this level of regulation is not possible in synthetic systems. Here, a synthetic macromolecular mimic is introduced, using supramolecular assembly to regulate activity. Catechol-terminated poly(vinyl alcohol) was synthesised by RAFT polymerization. Upon addition of Fe3+, larger supramolecular star polymers form by assembly with two or three catechols. This increase in molecular weight effectively ‘switches on’ the IRI activity and is the first example of external control over the function of AFP mimetics. This provides a simple but elegant solution to the challenge of external control of AFP-mimetic function. PMID:28003855

  12. Dielectric response of poly(vinyl alcohol)–zinc selenide nanocomposite film

    NASA Astrophysics Data System (ADS)

    Sinha, Subhojyoti; Das, Amit Kumar; Basu, Soumen; Meikap, Ajit Kumar

    2017-10-01

    Poly(vinyl alcohol)–zinc selenide (PVA–ZnSe) nanocomposite films have been prepared, which offer higher effective permittivity than pure PVA. There is an about 2.5-fold increase (at 420 K) in the effective permittivity at 100 kHz for the 4 wt % ZnSe nanostructure impregnated PVA film as calculated from the dielectric reinforcement function. Prevailing relaxation mechanisms in the nanocomposite films, within the frequency range of 100 Hz ≤ f ≤ 1 MHz and in the temperature range of 298 ≤ T ≤ 420 K, have been discussed on the basis of available theoretical approaches in the literature. AC conductivity behavior reveals that correlated barrier hopping is the ac charge transport mechanism for the nanocomposite films, and the maximum barrier heights vary inversely with the weight percent inclusion of ZnSe nanostructures.

  13. Electrochemical properties of poly(vinyl alcohol) and graphene oxide composite for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Theophile, Niyitanga; Jeong, Hae Kyung

    2017-02-01

    Poly(vinyl alcohol), PVA, polymer was successfully combined with graphene oxide (GO) and thermally reduced graphene oxide (RGO), respectively, to make composites and characterized for supercapacitor applications. PVA-RGO composite shows excellent electrochemical properties compared to PVA-GO composite. The capacitance of 190 Fg-1 is obtained from PVA-RGO composite which is larger than that (13 Fg-1) of PVA-GO composite. Electrochemical impedance of PVA-RGO is more than ten times smaller than that of PVA-GO at 20 kHz, demonstrating that PVA-RGO composite has a great advantage for supercapacitor applications compared to PVA, GO, RGO, and PVA-GO composite.

  14. Electro–optical properties of poly(vinyl acetate)/polyindole composite film

    SciTech Connect

    Bhagat, D. J. Dhokane, G. R.; Bajaj, N. S.

    2016-05-06

    In present work, electrical and optical properties of poly(vinyl acetate)/polyindole (PVAc/PIN) composite film are reported. The prepared composite was characterized via X–ray diffraction (XRD), UV–Vis spectroscopy and DC conductivity measurements. The polymer chain separation was determined using XRD analysis. An attempt has been made to study the temperature dependence of DC conductivity of PVAc/PIN composite in temperature range 308–373 K. The DC conductivity initially increases and reaches to 2.45×10–7 S/cm. The optical band gap value of composite is determined as 4.77 eV. The semiconducting nature of composite observed from electronic as well as optical band gap and Arrhenius behavior of DC plot.

  15. Synthesis and dielectric studies of poly (vinyl pyrrolidone) / titanium dioxide nanocomposites

    NASA Astrophysics Data System (ADS)

    Vasudevan, Prathibha; Thomas, Sunil; V, Arunkumar K.; S, Karthika; V, Unnikrishnan N.

    2015-02-01

    In this paper, we present the synthesis of poly vinyl pyrrolidone (PVP) / titanium dioxide nanocomposites via sol- gel technique. The structural and dielectric properties of the samples were also analysed in this work. PVP doped with varying concentrations of TiO2 are prepared by the sol-gel route. The prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and impedance spectroscopy. XRD and TEM confirm the presence of TiO2 nanoparticles in the composites. The dielectric response and the AC electrical conductivity of the samples are investigated for the frequency range 1 kHz-2MHz at room temperature. The dielectric studies show low values for dielectric constant and loss at high frequencies.

  16. Structurally Enhanced Self-Plasticization of Poly(vinyl chloride) via Click Grafting of Hyperbranched Polyglycerol.

    PubMed

    Lee, Kyu Won; Chung, Jae Woo; Kwak, Seung-Yeop

    2016-12-01

    A highly self-plasticized poly(vinyl chloride) (PVC) is demonstrated for the first time via click grafting of hyperbranched polyglycerol (HPG). The plasticizing effect of the grafted HPG on PVC is systematically investigated by various analytical methods. The amorphous and bulky dendritic structure of HPG efficiently increases the free volume of the grafted PVC, which leads to a remarkably lower glass transition temperature comparable to that of the conventional plasticized PVC. Viscoelastic analysis reveals that HPG considerably improves the softness of the grafted PVC at room temperature and promotes the segmental motion in the system. The HPG-grafted PVC films exhibit an exceptional stretchability unlike the mixture of PVC and HPG because the covalent attachment of HPG to PVC allows it to maintain its homogeneous and well-organized architecture under tensile stretching. The work provides valuable insights into the design of highly flexible and stretchable polymeric materials by means of introducing hyperbranched side chains.

  17. Dynamics in poly vinyl alcohol (PVA) based hydrogel: Neutron scattering study

    SciTech Connect

    Prabhudesai, S. A. Mitra, S.; Mukhopadhyay, R.; Lawrence, Mathias B.; Desa, J. A. E.

    2015-06-24

    Results of quasielastic neutron scattering measurements carried out on Poly Vinyl Alcohol (PVA) based hydrogels are reported here. PVA hydrogels are formed using Borax as a cross-linking agent in D{sub 2}O solvent. This synthetic polymer can be used for obtaining the hydrogels with potential use in the field of biomaterials. The aim of this paper is to study the dynamics of polymer chain in the hydrogel since it is known that polymer mobility influences the kinetics of loading and release of drugs. It is found that the dynamics of hydrogen atoms in the polymer chain could be described by a model where the diffusion of hydrogen atoms is limited within a spherical volume of radius 3.3 Å. Average diffusivity estimated from the behavior of quasielastic width is found to be 1.2 × 10{sup −5} cm{sup 2}/sec.

  18. Preparation and antimicrobial activity of poly (vinyl chloride)/gelatin/montmorillonite biocomposite films.

    PubMed

    Haroun, Ahmed A; Ahmed, Eman F; Abd El-Ghaffar, M A

    2011-11-01

    The aim of this study was using a novel antimicrobial thermoplastic plasticizer based on aliphatic anhydride derivative dodecenyl succinic anhydride (DSA) for blending poly (vinyl chloride), PVC, with gelatin in presence of montmorillonite (MMT) using Brabender via polymer melting technique. This anhydride-based plasticizer blended the membrane ingredients homogenously under melting process. The used plasticizer exhibited high performance antimicrobial potency for some biomedical and industrial applications. The prepared biocomposite films were evaluated for antimicrobial activity using agar disc diffusion method against gram-positive and gram-negative bacteria such as: Staphylococcus aureus (S. aureus), Klebsiella pneumonia (K. pneumonia), Bacillus cereus (B. cereus), Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli). The majority of these biocomposites, except the plasticized PVC with DOP, have shown inhibitory effect at different concentrations (1.0-20) mg/ml against all above mentioned bacteria. However, C. albicans and A. niger were the most resistant strains.

  19. Investigation of Salecan/poly(vinyl alcohol) hydrogels prepared by freeze/thaw method.

    PubMed

    Qi, Xiaoliang; Hu, Xinyu; Wei, Wei; Yu, Hao; Li, Junjian; Zhang, Jianfa; Dong, Wei

    2015-03-15

    Salecan is a novel water-soluble extracellular-glucan produced by a new kind of salt-tolerant strain Agrobacterium sp. ZX09 and can be applied in food and medicine industries. In this work, Salecan (Sal) was incorporated into poly(vinyl alcohol) (PVA) to prepare novel Sal/PVA hybrid hydrogels by repeated freeze-thaw processing. Physicochemical and biological characteristics of the hydrogels were investigated to evaluate their potential as cell adhesion materials. By increasing the Salecan content in the hybrid hydrogels, their swelling capacity increased notably, while the compressive modulus decreased. Observed by SEM, Sal/PVA hydrogels had a homogeneous porous structure. The degradation rate of the hydrogels can be controlled by tailoring the composition ratio of Sal/PVA. Furthermore, cells could adhere well on the surface of Sal/PVA hydrogels. In conclusion, these results make Sal/PVA hydrogels attractive materials for biomedical applications.

  20. Development of Chitosan/Poly(Vinyl Alcohol) Electrospun Nanofibers for Infection Related Wound Healing

    PubMed Central

    Wang, Mian; Roy, Amit K.; Webster, Thomas J.

    2017-01-01

    Chitosan is a cheap resource, which is widely used in biomedical applications due to its biocompatible and antibacterial properties. In this study, composite nanofibrous membranes of chitosan (CS) and poly(vinyl alcohol) (PVA) loaded with antibiotics at different ratios were successfully fabricated by electrospinning. The composite nanofibers were subjected to further analysis by scanning electron microscopy (SEM). SEM images revealed that the volumetric ratio of CS/PVA at 50/50 achieved an optimal nanofibrous structure (i.e., that most similar to natural tissues) compared with other volumetric ratios, which indicated that this CS/PVA electrospun scaffold has great potential to be used for infection related wound dressing for skin tissue regeneration. PMID:28123370

  1. Synthesis, characterization and application of biodegradable crosslinked carboxymethyl chitosan/poly(vinyl alcohol) clay nanocomposites.

    PubMed

    Sabaa, Magdy W; Abdallah, Heba M; Mohamed, Nadia A; Mohamed, Riham R

    2015-11-01

    Crosslinked poly(vinyl alcohol) (PVA)/carboxymethyl chitosan (CMCh) nanocomposites were synthesized using terephthaloyl diisothiocyanate crosslinker, in the presence of montmorillonite (MMT), in different ratios of the two matrices. Characterization of nanocomposites was performed using different analyses. Swelling behavior was studied in different buffered solutions. It was found that formation of crosslinked CMCh/PVA hydrogels increased the swellability. Metal ion adsorption has also been investigated. The results indicated that crosslinked CMCh adsorbs various metal ions much more than non crosslinked CMCh. Antimicrobial activity was examined against Gram positive bacteria, against Gram negative bacteria, and also against fungi. Results indicated that most of these nanocomposites exhibited good antimicrobial potency. Degradation study was carried out in Simulated Body Fluid (SBF) for different time periods in order to find out degradation index (Di). Results showed that weight loss of most of the nanocomposites increased as a function of incubation time.

  2. Crystallization and hardening of poly(ethylene-co-vinyl acetate) mouthguards during routine use

    PubMed Central

    Kuwahara, Ryoko; Tomita, Ryotaro; Ogawa, Natsumi; Nakajima, Kazunori; Takeda, Tomotaka; Uehara, Hiroki; Yamanobe, Takeshi

    2017-01-01

    Mouthguards (MGs) made from poly(ethylene-co-vinyl acetate) (EVA) are widely used in contact sports to prevent injuries such as breaking teeth and lip lacerations and to reduce brain concussion. However, the changes in morphology and the molecular mobility of EVA, which can affect its physical properties during practical usage, have not been precisely examined. Therefore, we attempted to determine the main factors which lead to changes in MG performance after one season of practical use by high school rugby players. Solid-state nuclear magnetic resonance (NMR) and pulse NMR measurements showed the hardening of MGs, which was associated with an increased crystallinity of the EVA resulting from prolonged usage. Furthermore, our data indicated that the increase in the relative amount of the crystalline phase may be primarily attributed to temperature fluctuations and repeated changes in pressure, which could cause the hardening of EVA and eventually diminish the protective ability of MGs. PMID:28294184

  3. Hydrogen ion-selective poly(vinyl chloride) membrane electrode based on a calix[4]arene.

    PubMed

    Kuruoğlu, Demet; Canel, Esin; Memon, Shahabuddin; Yilmaz, Mustafa; Kiliç, Esma

    2003-02-01

    A hydrogen ion-selective poly(vinyl chloride) membrane electrode was constructed using 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetracyanomethoxycalix[4]arene as a neutral carrier. The electrode showed an apparent Nernstian response in the 2-11.5 pH range with a slope of 54.0 +/- 0.2 mV/pH at 20 +/- degrees C. This electrode showed a rapid response of the emf to changes in the pH, high ion selectivity with respect to lithium, sodium and potassium, and characteristics similar to those reported for the conventional pH glass membrane electrode. It can be used as a potentiometric indicator electrode in hydrofluoric acid solutions. The effects of iodide, thiocyanate, perchlorate and bromide on the characteristics of the electrode were also considered.

  4. Development and characterization of poly(1-vinylpyrrolidone-co-vinyl acetate) copolymer based polymer electrolytes.

    PubMed

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

    2014-01-01

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

  5. Dynamic mechanical properties of photopolymerizable poly(vinyl alcohol)-acrylate monomer blends

    SciTech Connect

    Koshiba, M.; Yamaoka, T.; Tsunoda, T.

    1983-10-01

    Dynamic mechanical properties of photopolymerizable poly(vinyl alcohol) (PVA)-monoacrylate blends were investigated by measuring dynamic shear modulus G' and loss tangent, tan delta. The dynamic mechanical properties of the blends before being exposed to UV irradiation were governed by the weight percent of the monomers which act as plasticizers. On the other hand, the UV-irradiated blends seemed to be typical two-phase materials since they revealed two tan delta maxima whose positions were independent of the monomer content. Those two maxima were assigned to PVA and photopolymerized acrylates with reference to the dynamic mechanical data of PVA and a PVA-polyacrylamide polyblend. Those dynamic mechanical data suggested that insolubilization of the blend type photopolymers should be caused by a decrease in solubility due to graft polymerization of acrylate monomers onto PVA. 9 figures, 3 tables.

  6. Interpenetrating polymer network of locust bean gum-poly (vinyl alcohol) for controlled release drug delivery.

    PubMed

    Kaity, Santanu; Isaac, Jinu; Ghosh, Animesh

    2013-04-15

    A novel interpenetrating polymer network (IPN) microspheres of locust bean gum (LBG) and poly (vinyl alcohol) (PVA) was developed for oral controlled release of buflomedil hydrochloride (BH) by emulsion crosslinking method using glutaraldehyde as crosslinker. The effects of gum-polymer ratio, concentration of crosslinker and internal phase viscosity were evaluated thoroughly. Drug entrapment efficiency, particle size distribution, swelling property and in vitro release characteristics with kinetic modelling of microspheres were evaluated. The microspheres were characterised by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), solid state C(13) NMR, X-ray diffraction study (XRD) and differential scanning colorimetry (DSC). The microspheres showed control release property without showing any incompatibility in IPN device. Hence, IPN microspheres of LBG and PVA can be used as a potential carrier for controlled oral delivery of highly water soluble drugs like BH.

  7. Paclitaxel-loaded poly(lactide-co-glycolide)/poly(ethylene vinyl acetate) composite for stent coating by ultrasonic atomizing spray

    NASA Astrophysics Data System (ADS)

    Yuk, Soon Hong; Oh, Keun Sang; Park, Jinah; Kim, Soon-Joong; Kim, Jung Ho; Kwon, Il Keun

    2012-04-01

    The mixture of poly(lactide-co-glycolide) (PLGA) and poly(ethylene vinyl acetate) (PEVA) forms a homogeneous liquid in an organic solvent such as tetrahydrofuran, and a phase-separated PLGA/PEVA composite can be prepared from it by evaporating the organic solvent. Exploiting this phenomenon, we designed a novel method of preparing a drug-loaded PLGA/PEVA composite and used it for coating drug-eluting stents (DESs). Paclitaxel (PTX), an anticancer drug, was chosen as a model drug. PLGA acts as a microdepot for PTX, and PEVA provides mechanical strength to the coating material. The presence of PLGA in the PLGA/PEVA composite suppressed PTX crystallization in the coating material, and PTX showed a sustained release rate over more than 30 days. The mechanical strength of the PLGA/PEVA composite was better than that of PEVA used as a control. After coating the stent with a PLGA/PEVA composite using ultrasonic atomizing spray, the morphology of the coated material was observed by scanning electron microscopy, and the release pattern of PTX was measured by high-performance liquid chromatography.

  8. Dynamic modification of poly(methyl methacrylate) chips using poly(vinyl alcohol) for glycosaminoglycan disaccharide isomer separation.

    PubMed

    Zhang, Yong; Ping, Guichen; Kaji, Noritada; Tokeshi, Manabu; Baba, Yoshinobu

    2007-09-01

    We describe a microchip electrophoresis (MCE) method for the assay of unsaturated disaccharides of chondroitin sulfates, dermatan sulfates, and hyaluronic acid (HA). Poly(vinyl alcohol) (PVA) could be irreversibly adsorbed onto poly(methyl methacrylate) (PMMA) substrates and this approach was applicable for dynamic coating. The characteristics of the PMMA surface with PVA coating were evaluated in terms of the wettability, EOF, and adsorption of 2-aminoacridone (AMAC)-labeled disaccharide. The water contact angle decreased from 73 degrees on a pristine PMMA surface to 37.5 degrees on a PVA-coated surface, indicating that the PVA coating increased hydrophilicity. EOF was reduced approximately twofold and was relatively stable. Scanning electron microscopy and fluorescence microscopy images showed that adsorption of AMAC-labeled disaccharides was dramatically suppressed. Using the PVA coating, baseline separation of two pairs of glycosaminoglycan (GAG) disaccharide isomers, DeltaDi-diS(B)/DeltaDi-diS(D) and DeltaDi-0S/DeltaDi-HA, was achieved in Tris-borate buffer within 130 s by MCE.

  9. Actuator based on sulfonated comb copolymer of poly (ethylene-co-vinyl alcohol) grafted by poly (ethylene glycol)

    NASA Astrophysics Data System (ADS)

    Gong, Guifen; Li, Lei; Zhang, Yujun

    2007-07-01

    Comb copolymer consisting of poly (ethylene-co-vinyl alcohol) (EVAL) as backbone and poly (ethylene glycol) (PEG) as side chains (EVAL-g-PEG) has been synthesized, then it was sulfonated by 1,3-propane sultone to get the final ionomer (EVAL-g-SPEG), and ionic polymer-metal composite (IPMC) based on EVAL-g-SPEG was prepared through electroless deposition of platinum onto the surfaces of EVAL-g-SPEG membrane. The graft copolymers were characterized with respect to molecular weight using gel permeation chromatography (GPC) and composition using 1H-NMR. The results showed that the No. of PEG graft of the side chains is n=1, 2 and others. Thermal properties were examined by DSC and TG. The melt temperature (T m) and glass transition temperature (T g) of the comb copolymer increase with the increasing length and the number of the side chains. Moreover, the deformation performance of IPMC material was tested and its results show that the starting response voltage of IPMC actuator decreases with the increasing IEC value. On the other hand, the starting response voltage increases with the decreased side chain length. The IPMC with n=2 side chain length of PEG has the maximum tip displacement, and the maximum tip displacement of IPMC membrane generally decreases with the side chain length of EVAL-g-SPEG. This feature may be the reflection of two opposite effects, namely the decreasing ion densities and increasing water sorption of the membrane.

  10. Tunable shape memory behaviors of poly(ethylene vinyl acetate) achieved by adding poly(L-lactide)

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-xing; Liao, Fei; He, Zhen-zhen; Yang, Jing-hui; Huang, Ting; Zhang, Nan; Wang, Yong; Gao, Xiao-ling

    2015-12-01

    In this work, different contents of poly(L-lactide) (PLLA) (20-50 wt%) were introduced into poly(ethylene vinyl acetate) (EVA) to prepare the samples with a tunable shape memory behavior. Morphological characterization demonstrated that with increasing PLLA content from 20 to 50 wt%, the blend morphology changed from sea-island structure to cocontinuous structure. In all the samples, PLLA was amorphous and it did not affect the crystallization of polyethylene part in the EVA component. The presence of PLLA greatly enhanced the storage modulus of samples, especially at relatively low temperatures. The shape memory behaviors of samples were systematically investigated and the results demonstrated that the EVA/PLLA blends exhibited a tunable shape memory effect. On one hand, PLLA accelerated the shape fixation and enhanced the fixity ratio of samples. On the other hand, PLLA reduced the dependence of shape fixity of samples on fixity temperatures. Specifically, for the first time, a critical recovery temperature was observed for the immiscible shape memory polymer blends. In this work, the critical recovery temperature was about 53 °C. At recovery temperature below the critical value, the blends exhibited smaller recovery ratios compared with the pure EVA, however, at recovery temperature above 53 °C, the blends exhibited higher recovery ratios.

  11. Electron Beam Damage in Poly(Vinyl Chloride) and Poly(Acrylonitrile) as Observed by Auger Electron Spectroscopy

    SciTech Connect

    Lea, Alan S.; Engelhard, Mark H.; Baer, Donald R.

    2003-03-07

    AES spectra of spun-cast films of poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) were collected over a period of time to determine specimen damage during exposure to a 10kV electron beam. For the PVC, loss of chlorine was observed over a period of 203 minutes to the extent that the final chlorine concentration was only 20% of its original value. PAN exhibited a loss in nitrogen content over a period of 120 minutes, but the rate of damage to the polymer was significantly less than PVC. Figure 1 shows the atomic concentration in the PVC film as a function of dose (time). It takes a dose of approximately 7.0x10-5 Ccm-5 for the chlorine concentration to fall from its original value by 10% (one definition of critical dose). Figure 2 shows a similar drop in nitrogen concentration in the PAN film as a function of dose. For this polymer, it takes a dose of 1.3x10-3 Ccm-2 for the nitrogen concentration to fall by 10%.

  12. Fabrication and characterization of superparamagnetic poly(vinyl pyrrolidone)/poly(L-lactide)/Fe3O4 electrospun membranes

    NASA Astrophysics Data System (ADS)

    Savva, Ioanna; Constantinou, Demetris; Marinica, Oana; Vasile, Eugeniu; Vekas, Ladislau; Krasia-Christoforou, Theodora

    2014-02-01

    The fabrication of magnetoactive fibrous nanocomposite membranes based on poly(vinyl pyrrolidone) (PVP), poly(L-lactide) (PLLA) and pre-formed oleic acid coated magnetite nanoparticles (OA Fe3O4) is presented. The aforementioned materials have been prepared by means of the electrospinning technique following a single-step fabrication process. The PVP/PLLA/OA Fe3O4 nanocomposite membranes were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that provided information on the fiber diameters as well as on the morphological and dimensional characteristics of the OA Fe3O4 nanoparticles embedded within the fibers. The thermal stability of these materials was evaluated by means of thermal gravimetric analysis (TGA) measurements. Finally, vibrational sample magnetometry (VSM) analysis disclosed superparamagnetic behavior at room temperature. The combination of the hydrophilic, biocompatible and photo-crosslinkable PVP with the biodegradable PLLA and the superparamagnetic OA Fe3O4 nanoparticles within these materials allows for the future development of crosslinked fibrous magnetoactive nanocomposites exhibiting high stability in aqueous solutions, with potential use in biomedical and environmental applications.

  13. Paclitaxel-loaded poly(lactide-co-glycolide)/poly(ethylene vinyl acetate) composite for stent coating by ultrasonic atomizing spray.

    PubMed

    Yuk, Soon Hong; Oh, Keun Sang; Park, Jinah; Kim, Soon-Joong; Kim, Jung Ho; Kwon, Il Keun

    2012-04-01

    The mixture of poly(lactide-co-glycolide) (PLGA) and poly(ethylene vinyl acetate) (PEVA) forms a homogeneous liquid in an organic solvent such as tetrahydrofuran, and a phase-separated PLGA/PEVA composite can be prepared from it by evaporating the organic solvent. Exploiting this phenomenon, we designed a novel method of preparing a drug-loaded PLGA/PEVA composite and used it for coating drug-eluting stents (DESs). Paclitaxel (PTX), an anticancer drug, was chosen as a model drug. PLGA acts as a microdepot for PTX, and PEVA provides mechanical strength to the coating material. The presence of PLGA in the PLGA/PEVA composite suppressed PTX crystallization in the coating material, and PTX showed a sustained release rate over more than 30 days. The mechanical strength of the PLGA/PEVA composite was better than that of PEVA used as a control. After coating the stent with a PLGA/PEVA composite using ultrasonic atomizing spray, the morphology of the coated material was observed by scanning electron microscopy, and the release pattern of PTX was measured by high-performance liquid chromatography.

  14. Branched polyesters based on poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(D,L-lactide-co-glycolide): effects of polymer structure on in vitro degradation behaviour.

    PubMed

    Unger, Florian; Wittmar, Matthias; Morell, Frank; Kissel, Thomas

    2008-05-01

    Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(D,L-lactide-co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. Here the in vitro degradation behaviour with a special emphasis on elucidating structure-property relationships is reported. Effects of type and degree of amine substitution as well as PLGA side chain length were considered. In a first set of experiment, the weight loss of solvent cast films of defined size from 19 polymers was measured as a function of incubation in phosphate buffer (pH 7.4) at 37 degrees C over a time of 21 days. A second study was initiated focusing on three selected polymers in a similar set up, but with additional observation of pH influences (pH 2 and pH 9) and determination of water uptake (swelling) and molecular weights during degradation. Scanning electron micrographs have been recorded at selected time points to characterize film specimens morphologically after degradation. Our investigations revealed the potential to influence the degradation of this polymer class by the degree of amine substitution, higher degrees leading to faster erosion. The erosion rate could further be influenced by the type of amine functionality, DEAPA-modified polyesters degrading as fast as or slightly faster than DMAPA-modified polyesters and these degrading faster than DEAEA-PVA-g-PLGA. As a third option the degradation rate could be modified by the PLGA side chain length, shorter side chains leading to faster erosion. As compared to linear PLGA, remarkably shorter degradation times could be achieved by grafting short PLGA side chains onto amine-modified PVA backbones. Erosion times from less than 5 days to more than 4 weeks could be realized by selecting the type of amine functionality, the degree of amine substitution and the PLGA side chain length at the time of synthesis. In addition, the pathway of hydrolytic degradation can be

  15. Measurements of Dynamic Viscoelasticity of Poly (vinyl alcohol) Hydrogel for the Development of Blood Vessel Biomodeling

    NASA Astrophysics Data System (ADS)

    Kosukegawa, Hiroyuki; Mamada, Keisuke; Kuroki, Kanju; Liu, Lei; Inoue, Kosuke; Hayase, Toshiyuki; Ohta, Makoto

    In vitro blood vessel biomodeling with realistic mechanical properties and geometrical structures is helpful for training in surgical procedures, especial those used in endovascular treatment. Poly (vinyl alcohol) hydrogel (PVA-H), which is made of Poly (vinyl alcohol) (PVA) and water, may be useful as a material for blood vessel biomodeling due to its low surface friction resistance and good transparency. In order to simulate the mechanical properties of blood vessels, measurements of mechanical properties of PVA-H were carried out with a dynamic mechanical analyzer, and the storage modulus (G’) and loss modulus (G”) of PVA-H were obtained. PVA-Hs were prepared by the low-temperature crystallization method. They were made of PVA with various concentrations (C) and degrees of polymerization (DP), and made by blending two kinds of PVA having different DP or saponification values (SV). The G’ and G” of PVA-H increased, as the C or DP of PVA increased, or as the proportion of PVA with higher DP or SV increased. These results indicate that it is possible to obtain PVA-H with desirable dynamic viscoelasticity. Furthermore, it is suggested that PVA-H is stable in the temperature range of 0°C to 40°C, indicating that biomodeling made of PVA-H should be available at 37°C, the physiological temperature. The dynamic viscoelasticity of PVA-H obtained was similar to that of the dog blood vessel measured in previous reports. In conclusion, PVA-H is suggested to be useful as a material of blood vessel biomodeling.

  16. Antibacterial Electrospun Poly(vinyl alcohol)/Enzymatic Synthesized Poly(catechol) Nanofibrous Midlayer Membrane for Ultrafiltration.

    PubMed

    Coelho, Dora; Sampaio, Ana; Silva, Carla J S M; Felgueiras, Helena P; Amorim, M Teresa P; Zille, Andrea

    2017-09-27

    Two different nanofibrous antibacterial membranes containing enzymatically synthesized poly(catechol) (PC) or silver nitrate (AgNO3, positive control) blended with poly(vinyl alcohol) (PVA) and electrospun onto a poly(vinylidene fluoride) (PVDF) basal disc to generate thin-film composite midlayers were produced for water ultrafiltration applications. The developed membranes were thoroughly characterized in terms of morphology, chemical composition, and general mechanical and thermal features, antimicrobial activity, and ultrafiltration capabilities. The electrospun blends were recognized as homogeneous. Data revealed relevant conformational changes in the PVA side groups, attributed to hydrogen bonding, high thermal stability, and residual mass. PVDF+PVA/AgNO3 membrane displayed 100% growth inhibition of both Gram-positive and Gram-negative bacteria strains, despite the wide range of fiber diameters generated, from 24 to 125 nm, formation of numerous beads, and irregular morphology. The PVDF+PVA/PC membrane showed a good growth inhibition of Staphylococcus aureus (92%) and revealed a smooth morphology with no relevant bead formations and diameters ranging from 68 to 131 nm. The ultrafiltration abilities of the membrane containing PVA/PC were tested in a dead-end high-pressure cell (4 bar) using a reactive dye in distilled water and seawater. After 5 cycles, a maximum rejection of ≈85% with an average flux rate of 70 L m(-2) h(-1) for distilled water and ≈64% with an average flux rate of 62 L m(-2) h(-1) for seawater were determined with an overall salt rejection of ≈5%.

  17. Synthesis and antibacterial of carboxymethyl starch-grafted poly(vinyl imidazole) against some plant pathogens.

    PubMed

    El-Hamshary, Hany; Fouda, Moustafa M G; Moydeen, Meera; El-Newehy, Mohamed H; Al-Deyab, Salem S; Abdel-Megeed, Ahmed

    2015-01-01

    Poly(N-vinyl imidazole) (PVI) has been grafted onto carboxymethyl starch (CMS) in aqueous solution using potassium persulfate (KPS) as initiator. Reaction parameters that affect grafting efficiency and percentage grafting such as monomer and initiator concentration, the reaction temperature and time were investigated. The grafted products were characterized by FTIR, thermal analysis, SEM photograph and elemental analysis. The antibacterial effects of the carboxymethyl starch-grafted-poly(N-vinylimidazole) (CMS-g-PVI) was examined against two plant pathogens Gram negative bacteria: Xanthomonas perforanss and Xanthomonas oryzae. Generally, upon application of the CMS-g-PVI to the bacterial cells; the mortality rate increased from 45.71 to 59.37% for Xanthomonas perforans and X. oryzae, respectively. While the MIC for most of both bacterial strains were recorded at concentration of 60 μg/mL. The results indicate that CMS-g-PVI has bactericidal properties and can be used for seed treatment to control xanthomonads associated with bacterial leaf spot (BLS).

  18. Microcontact imprinting of algae on poly(ethylene-co-vinyl alcohol) for biofuel cells.

    PubMed

    Chen, Wen-Janq; Lee, Mei-Hwa; Thomas, James L; Lu, Po-Hsun; Li, Ming-Huan; Lin, Hung-Yin

    2013-11-13

    Hydrogen can be produced using microorganisms (e.g., bacteria and algae); algal production has the additional ecological benefit of carbon dioxide fixation. The conversion of hydrogen to electricity via fuel cells may be more efficient compared to other energy sources of electricity. However, the anode of biofuel cells requires the immobilization of microorganisms or enzymes. In this work, poly(ethylene-co-vinyl alcohol) (EVAL), was coated on the electrode, and green algae was microcontact imprinted onto the EVAL film. The readsorption of algae onto algae-imprinted EVAL thin films was compared to determine the ethylene content that gave highest imprinting effectiveness and algal binding. Scanning electron microscopy and fluorescence spectrometry were employed to characterize the surface morphology, recognition capacity, and reusability of the algae-imprinted cavities. The recognition of an individual algal cell by binding to the imprinted cavities was directly observed by video microscopy. Finally, the power and current density of the algal biofuel cell using the algae-imprinted EVAL-coated electrode were measured at about 2-fold higher than electrode sputtered platinum on poly(ethylene terephthalate).

  19. Improvement of Polylactide Properties through Cellulose Nanocrystals Embedded in Poly(Vinyl Alcohol) Electrospun Nanofibers.

    PubMed

    López de Dicastillo, Carol; Garrido, Luan; Alvarado, Nancy; Romero, Julio; Palma, Juan Luis; Galotto, Maria Jose

    2017-05-11

    Electrospun nanofibers of poly (vinyl alcohol) (PV) were obtained to improve dispersion of cellulose nanocrystals (CNC) within hydrophobic biopolymeric matrices, such as poly(lactic acid) (PLA). Electrospun nanofibers (PV/CNC)n were successfully obtained with a final concentration of 23% (w/w) of CNC. Morphological, structural and thermal properties of developed CNC and electrospun nanofibers were characterized. X-ray diffraction and thermal analysis revealed that the crystallinity of PV was reduced by the electrospinning process, and the incorporation of CNC increased the thermal stability of biodegradable nanofibers. Interactions between CNC and PV polymer also enhanced the thermal stability of CNC and improved the dispersion of CNC within the PLA matrix. PLA materials with CNC lyophilized were also casted in order to compare the properties with materials based on CNC containing nanofibers. Nanofibers and CNC were incorporated into PLA at three concentrations: 0.5%, 1% and 3% (CNC respect to polymer weight) and nanocomposites were fully characterized. Overall, nanofibers containing CNC positively modified the physical properties of PLA materials, such as the crystallinity degree of PLA which was greatly enhanced. Specifically, materials with 1% nanofiber 1PLA(PV/CNC)n presented highest improvements related to mechanical and barrier properties; elongation at break was enhanced almost four times and the permeation of oxygen was reduced by approximately 30%.

  20. Improvement of Polylactide Properties through Cellulose Nanocrystals Embedded in Poly(Vinyl Alcohol) Electrospun Nanofibers

    PubMed Central

    López de Dicastillo, Carol; Garrido, Luan; Alvarado, Nancy; Romero, Julio; Palma, Juan Luis; Galotto, Maria Jose

    2017-01-01

    Electrospun nanofibers of poly (vinyl alcohol) (PV) were obtained to improve dispersion of cellulose nanocrystals (CNC) within hydrophobic biopolymeric matrices, such as poly(lactic acid) (PLA). Electrospun nanofibers (PV/CNC)n were successfully obtained with a final concentration of 23% (w/w) of CNC. Morphological, structural and thermal properties of developed CNC and electrospun nanofibers were characterized. X-ray diffraction and thermal analysis revealed that the crystallinity of PV was reduced by the electrospinning process, and the incorporation of CNC increased the thermal stability of biodegradable nanofibers. Interactions between CNC and PV polymer also enhanced the thermal stability of CNC and improved the dispersion of CNC within the PLA matrix. PLA materials with CNC lyophilized were also casted in order to compare the properties with materials based on CNC containing nanofibers. Nanofibers and CNC were incorporated into PLA at three concentrations: 0.5%, 1% and 3% (CNC respect to polymer weight) and nanocomposites were fully characterized. Overall, nanofibers containing CNC positively modified the physical properties of PLA materials, such as the crystallinity degree of PLA which was greatly enhanced. Specifically, materials with 1% nanofiber 1PLA(PV/CNC)n presented highest improvements related to mechanical and barrier properties; elongation at break was enhanced almost four times and the permeation of oxygen was reduced by approximately 30%. PMID:28492470

  1. Influence of Block Copolymerization on the Antifreeze Protein Mimetic Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol).

    PubMed

    Congdon, Thomas R; Notman, Rebecca; Gibson, Matthew I

    2016-09-12

    Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications-from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action.

  2. The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate).

    PubMed

    Arellanes-Lozada, Paulina; Olivares-Xometl, Octavio; Guzmán-Lucero, Diego; Likhanova, Natalya V; Domínguez-Aguilar, Marco A; Lijanova, Irina V; Arce-Estrada, Elsa

    2014-08-07

    Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC12), poly(1-vinyl-3-octylimidazolium) (PImC₈) and poly(1-vinyl-3-butylimidazolium) (PImC₄) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1-1 M H₂SO₄) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir's isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC₈ > PImC₄) to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs' partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions.

  3. The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate)

    PubMed Central

    Arellanes-Lozada, Paulina; Olivares-Xometl, Octavio; Guzmán-Lucero, Diego; Likhanova, Natalya V.; Domínguez-Aguilar, Marco A.; Lijanova, Irina V.; Arce-Estrada, Elsa

    2014-01-01

    Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC12), poly(1-vinyl-3-octylimidazolium) (PImC8) and poly(1-vinyl-3-butylimidazolium) (PImC4) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1–1 M H2SO4) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir’s isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC8 > PImC4) to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs’ partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions. PMID:28788156

  4. Influence of Block Copolymerization on the Antifreeze Protein Mimetic Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol)

    PubMed Central

    2016-01-01

    Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications—from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action. PMID:27476873

  5. Poly(acrylic acid)-block-poly(vinyl alcohol) anchored maghemite nanoparticles designed for multi-stimuli triggered drug release

    NASA Astrophysics Data System (ADS)

    Liu, Ji; Detrembleur, Christophe; Debuigne, Antoine; de Pauw-Gillet, Marie-Claire; Mornet, Stéphane; Vander Elst, Luce; Laurent, Sophie; Labrugère, Christine; Duguet, Etienne; Jérôme, Christine

    2013-11-01

    Original core/corona nanoparticles composed of a maghemite core and a stimuli-responsive polymer coating made of poly(acrylic acid)-block-poly(vinyl alcohol) macromolecules were fabricated for drug delivery system (DDS) application. This kind of DDS aims to combine the advantage of stimuli-responsive polymer coating, in order to regulate the drug release behaviours under different conditions and furthermore, improve the biocompatibility and in vivo circulation half-time of the maghemite nanoparticles. Drug loading capacity was evaluated with methylene blue (MB), a cationic model drug. The triggered release of MB was studied under various stimuli such as pH, ionic strength and temperature. Local heating generated under alternating magnetic field (AMF) application was studied, and remotely AMF-triggered release was also confirmed, while a mild heating-up of the release medium was observed. Furthermore, their potential application as magnetic resonance imaging (MRI) contrast agents was explored via relaxivity measurements and acquisition of T2-weighted images. Preliminary studies on the cytotoxicity against mouse fibroblast-like L929 cell line and also their cellular uptake within human melanoma MEL-5 cell line were carried out. In conclusion, this kind of stimuli-responsive nanoparticles appears to be promising carriers for delivering drugs to some tumour sites or into cellular compartments with an acidic environment.Original core/corona nanoparticles composed of a maghemite core and a stimuli-responsive polymer coating made of poly(acrylic acid)-block-poly(vinyl alcohol) macromolecules were fabricated for drug delivery system (DDS) application. This kind of DDS aims to combine the advantage of stimuli-responsive polymer coating, in order to regulate the drug release behaviours under different conditions and furthermore, improve the biocompatibility and in vivo circulation half-time of the maghemite nanoparticles. Drug loading capacity was evaluated with methylene

  6. Effects of poly(2-hydroxyethyl methacrylate) and poly(vinyl-pyrrolidone) hydrogel implants on myopic and normal chick sclera

    PubMed Central

    Su, James; Iomdina, Elena; Tarutta, Elena; Ward, Brian; Song, Jie; Wildsoet, Christine F.

    2008-01-01

    There has been generally little attention paid to the utilization of biomaterials as an anti-myopia treatment. The purpose of this study was to investigate whether polymeric hydrogels, either implanted or injected adjacent to the outer scleral surface, slow ocular elongation. White Leghorn (gallus gallus domesticus) chicks were used at 2 weeks of age. Chicks had either (1) strip of poly(2-hydroxyethyl methacrylate) (pHEMA) implanted monocularly against the outer sclera at the posterior pole, or (2) an in situ polymerizing gel [main ingredient: poly(vinyl-pyrrolidone) (PVP)] injected monocularly at the same location. Some of the eyes injected with the polymer were fitted with a diffuser or a −10D lens. In each experiment, ocular lengths were measured at regular intervals by high frequency A-scan ultrasonography, and chicks were sacrificed for histology at staged intervals. No in vivo signs of either orbital or ocular inflammation were observed. The pHEMA implant significantly increased scleral thickness by the third week, and the implant became encapsulated with fibrous tissue. The PVP-injected eyes left otherwise untreated, showed a significant increase in scleral thickness, due to increased chondrocyte proliferation and extracellular matrix deposition. However, there was no effect of the PVP injection on ocular elongation. In eyes wearing optical devices, there was no effect on either scleral thickness or ocular elongation. These results represent “proof of principle” that scleral growth can be manipulated without adverse inflammatory responses. However, since neither approach slowed ocular elongation, additional factors must influence scleral surface area expansion in the avian eye. PMID:19109950

  7. Improved dielectric properties of nanocomposites based on poly(vinylidene fluoride) and poly(vinyl alcohol)-functionalized graphene.

    PubMed

    Wang, Dongrui; Bao, Yaru; Zha, Jun-Wei; Zhao, Jun; Dang, Zhi-Min; Hu, Guo-Hua

    2012-11-01

    In this work, two series of nanocomposites of poly(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10⁷ Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials.

  8. Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Hydrogel in a dc Electric Field: Swelling, Shape Change, and Actuation Characteristics

    PubMed Central

    2014-01-01

    Poly(vinyl alcohol) (PVA)/Poly(acrylic acid) (PAA) hydrogel can be utilized as a biomimetic actuator and coating material for tissue-implant interface, when employing an electrical stimulus. The swelling, shape change, and actuation characteristics of PVA/PAA hydrogel in a range of dc electrical fields were determined to find the optimal electric field for the hydrogel application as biomimetic actuator and coating materials. The hydrogel samples were prepared by dissolving PVA and PAA in deionized water at 4 wt% and mixed together at 1:1 ratio. Two custom made experimental setups were fabricated; one used for the measurement of swelling ratio of the hydrogels; and the other used for the shape changes or actuation characteristics of the hydrogels. Swelling experiments show increased swelling ratios of the hydrogel due to 10 V, 20 V, and 30 V electric fields. The rate of increment of the swelling ratio of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. The width and height changes of rectangular shapes and maximum deflection along the length of hydrogel sample due to a range of electric fields (0-30V) were measured using an optical microscope. Incremental shape change up to a specific threshold value (around 10V) was observed due to electric stimulus. Electrostatic actuation pressure of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. These results suggested that optimal performance of PVA/PAA hydrogel can be achieved around 10V. PMID:25478321

  9. 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; Bakar, Ahmad Ashrif A.; Ratnam, Chantara Thevy; 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.

  10. Protonation effects on the photophysical properties of poly(2,5-pyridine diyl)

    NASA Astrophysics Data System (ADS)

    Monkman, A. P.; Halim, M.; Samuel, I. D. W.; Horsburgh, L. E.

    1998-12-01

    We have recently shown that poly(2,5-pyridine diyl) (PPY) can be synthesized to yield a polymer with high photoluminescence quantum yield (PLQY) in the solid state, and that it is an excellent electron transport material. To explore the photophysical properties of PPY further, we have used a range of acidic "dopants" to protonate the nitrogen sites on each ring and made observations on how this affects the optical properties of the resultant protonated PPY films. In general, we find that sulphonic acids have the greatest effect, causing perturbations to both the ground-state and excited-state properties of the PPY. These changes occur with only moderate reduction of the PLQY, whereas nonsulphonic acids cause a larger reduction in PLQY without significantly affecting the ground- or excited-state energy levels. These aspects of the photophysics of PPY can be described using a simple ring torsion argument. This model can also account for the observed shifts between solution state and solid-state emission wavelengths.

  11. Effect of Poly(Vinyl Alcohol) Addition on the Properties of Hydrothermal Derived Calcium Phosphate Cement for Bone Filling Materials

    NASA Astrophysics Data System (ADS)

    Razali, N. N.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.; Singh, R.

    2017-06-01

    The effect of addition of poly(vinyl alcohol) on hydrothermal derived calcium phosphate cement has been studied. The precursors used to prepare the cement were calcium oxide (CaO) and ammonium dihydrogen phosphate (NH4H2PO4); the reaction was conducted in water at 80-100°C. To improve properties of CPC, poly(vinyl alcohol) (PVA) of 1wt% and 2wt% was added to the liquid phase of CPC and the results were compared to CPC without PVA addition. The addition of PVA was proved to bring remarkable effects on cohesion, setting time and mechanical strength of CPC which make it suitable physically for injectable bone filler applications.

  12. Portable potentiostatic sensor integrated with neopterin-imprinted poly(ethylene-co-vinyl alcohol)-based electrode.

    PubMed

    Huang, C-Y; Hsieh, C-H; Chen, Y-L; Lee, M-H; Lin, C-F; Tsai, H-H; Juang, Y-Z; Liu, B-D; Lin, H-Y

    2011-12-01

    Neopterin is a catabolic product of guanosine triphosphate, a purine nucleotide. Measuring neopterin concentrations in biological fluids such as urine provides information about cellular immune activation in humans under control of T helper cells. A high neopterin concentration in bodily fluids, including serum and urine, indicates cellular immunity activation, which is associated with oxidative stress. In this work, neopterin is the target molecule and imprinted onto poly(ethylene-co-vinyl alcohol) via solvent evaporation. The template molecules on the thin film are then removed, and the membrane is used as a sensing element for electrochemical urinalysis. Poly(ethylene-co-vinyl alcohol) containing 27 mol% ethylene had high imprinting effectiveness and may be integrated with the proposed portable biosensor. In random urine analysis, the cyclic voltammetry measurements of neopterin with an additional recovery method achieved >95% recovery for the neopterin concentration of 15 ng/mL.

  13. Novel hydrogels of chitosan and poly(vinyl alcohol)-g-glycolic acid copolymer with enhanced rheological properties.

    PubMed

    Lejardi, A; Hernández, R; Criado, M; Santos, Jose I; Etxeberria, A; Sarasua, J R; Mijangos, C

    2014-03-15

    Poly(vinyl alcohol) (PVA) has been grafted with glycolic acid (GL), a biodegradable hydroxyl acid to yield modified poly(vinyl alcohol) (PVAGL). The formation of hydrogels at pH = 6.8 and physiological temperature through blending chitosan (CS) and PVAGL at different concentrations has been investigated. FTIR, DOSY NMR and oscillatory rheology measurements have been carried out on CS/PVAGL hydrogels and the results have been compared to those obtained for CS/PVA hydrogels prepared under the same conditions. The experimental results point to an increase in the number of interactions between chitosan and PVAGL in polymer hydrogels prepared with modified PVA. The resulting materials with enhanced elastic properties and thixotropic behavior are potential candidates to be employed as injectable materials for biomedical applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Beam Damage of Poly(Vinyl Chloride) [PVC] Film as Observed by X-ray Photoelectron Spectroscopy

    SciTech Connect

    Engelhard, Mark H.; Krishna, Abhilash; Kulkarni, Pranita B.; Lee, Chi-Ying M.; Baer, Donald R.

    2003-03-08

    XPS spectra of a spin-coated film poly(vinyl chloride) (PVC) were collected over a period of 243 minutes at 303 K to determine specimen damage during long exposures to monochromatic Al Ka x-rays. For this PVC film we measured the loss of chlorine as a function of time by rastering a focused 104.6 w 100 um diameter x-ray beam over a 1.4 mm x 0.2 mm area on the sample.

  15. Development of structure in natural silk spinning and poly(vinyl alcohol) hydrogel formation

    NASA Astrophysics Data System (ADS)

    Willcox, Patricia Jeanene

    This research involves the characterization of structure and structure formation in aqueous systems. Particularly, these studies investigate the effect of various processing variables on the structure formation that occurs upon conversion from aqueous solution to fiber or hydrogel. The two processes studied include natural silk fiber spinning and physical gelation of poly(vinyl alcohol), PVOH, in water. The techniques employed combine cryogenic technology for sample preparation and direct observation by transmission electron microscopy with electron diffraction, atomic force microscopy, optical rheometry, X-ray scattering and optical microscopy. In order to explore the full range of structure formation in natural silk spinning, studies are conducted in vivo and in vitro. In vivo structural investigations are accomplished through the cryogenic quenching and subsequent microtoming of live silk-spinning animals, Nephila clavipes (spider) and Bombyx mori (silkworm). Observations made using transmission electron microscopy, electron diffraction and atomic force microscopy indicate a cholesteric liquid crystalline mesophase of aqueous silk fibroin in both species. The mechanism of structure formation in solution is studied in vitro using optical rheometry on aqueous solutions made from regenerated Bombyx mori cocoon silk. Concentrated solutions exhibit birefringence under flow, with a wormlike conformation of the silk molecules in concentrated salt solution. Changes in salt concentration and pH of the aqueous silk solutions result in differing degrees of alignment and aggregation. These results suggest that structural control in the natural silk spinning process is accomplished by chemical manipulation of the electrostatic interactions and hydrogen bonding between chains. Application of cryogenic methods in transmission electron microscopy also provides a unique look at hydration-dependent structures in gels of poly(vinyl alcohol) produced by freeze-thaw processing

  16. Antifungal activity, biofilm-controlling effect, and biocompatibility of poly(N-vinyl-2-pyrrolidinone)-grafted denture materials

    PubMed Central

    Sun, Xinbo; Cao, Zhengbing; Yeh, Chih-Ko; Sun, Yuyu

    2013-01-01

    Colonization and biofilm-formation of Candida species on denture surfaces cause Candida-associated denture stomatitis (CADS), a common, recurring disease affecting up to 67% of denture wearers. We developed poly(N-vinyl-2-pyrrolidinone)-grafted denture materials that can be repeatedly recharged with various antifungal drugs to achieve long-term antifungal and biofilm-controlling effects. The monomer, N-vinyl-2-pyrrolidinone (NVP), was grafted onto poly(methyl methacrylate) denture resins through plasma-initiated grafting polymerization. The physical properties and biocompatibility of the resulting resins were not negatively affected by the presence of up to 7.92% of grafted poly (N-vinyl-2-pyrrolidinone) (PNVP). Miconazole and chlorhexidine digluconate (CD) were used as model antifungal drugs. PNVP grafting significantly increased the drug absorption capability of the resulting denture materials. Further, the new materials showed sustained drug release and provided antifungal effects for weeks (in the case of CD) to months (in the case of miconazole). The drug-depleted resins could be recharged with the same or a different class of antifungal drug to further extend antifungal duration. If needed, drugs on the PNVP-grafted denture materials could be “washed out” (quenched) by treating with PNVP aqueous solutions to stop drug release. These results point to great potentials of the new materials in controlling biofilm-formation in a wide range of device-related applications. PMID:23708753

  17. Poly(anhydride-ester) and poly(N-vinyl-2-pyrrolidone) blends: salicylic acid-releasing blends with hydrogel-like properties that reduce inflammation.

    PubMed

    Ouimet, Michelle A; Fogaça, Renata; Snyder, Sabrina S; Sathaye, Sameer; Catalani, Luiz H; Pochan, Darrin J; Uhrich, Kathryn E

    2015-03-01

    Polymers such as poly(N-vinyl-2-pyrrolidone) (PVP) have been used to prepare hydrogels for wound dressing applications but are not inherently bioactive. For enhanced healing, PVP was blended with salicylic acid-based poly(anhydride-esters) (SAPAE) and shown to exhibit hydrogel properties upon swelling. In vitro release studies demonstrated that the chemically incorporated drug (SA) was released from the polymer blends over 3-4 d in contrast to 3 h, and that blends of higher PVP content displayed greater swelling values and faster SA release. The polymer blends significantly the inflammatory cytokine, TNF-α, in vitro without negative effects.

  18. Ionic conduction in poly(vinyl chloride)/poly(ethyl methacrylate)-based polymer blend electrolytes complexed with different lithium salts

    NASA Astrophysics Data System (ADS)

    Rajendran, S.; Prabhu, M. Ramesh; Rani, M. Usha

    Poly(vinyl chloride)/poly(ethyl methacrylate)-based polymer blend electrolytes comprising propylene carbonate as a plasticizer and a lithium salt LiX (X = BF 4 -, ClO 4 -, CF 3SO 3 -) are prepared by a solvent casting technique. The electrolytes are subjected to characterization by ionic conductivity, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetic/differential thermal analysis. The electrolytes that contain LiBF 4 exhibit maximum conductivity and are thermally stable up to 254 °C.

  19. Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes

    NASA Astrophysics Data System (ADS)

    Pakzad, A.; Simonsen, J.; Yassar, R. S.

    2012-03-01

    In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content.

  20. Poly(vinyl alcohol)-based film potentially suitable for antimicrobial packaging applications.

    PubMed

    Musetti, Alessandro; Paderni, Katia; Fabbri, Paola; Pulvirenti, Andrea; Al-Moghazy, Marwa; Fava, Patrizia

    2014-04-01

    This work aimed at developing a thin and water-resistant food-grade poly(vinyl alcohol) (PVOH)-based matrix able to swell when in contact with high moisture content food products without rupturing to release antimicrobial agents onto the food surface. This film was prepared by blending PVOH and 7.20% (wt/wt of PVOH) of poly(ethylene glycol) (PEG) with citric acid as crosslinking agent. The film-forming solution was then casted onto a flat surface and the obtained film was 60 μm in thickness and showed a good transparency (close to T = 100%) in the visible region (400 to 700 nm). After immersion in water for 72 h at room temperature, the crosslinked matrix loses only 19.2% of its original weight (the percentage includes the amount of unreacted crosslinking agent, antimicrobial in itself). Water content, degree of swelling, and crosslinking density of the film prove that the presence of PEG diminishes the hydrophilic behavior of the material. Also the mechanical properties of the wet and dry film were assessed. Alongside this, 2.5% (wt/wt of dry film) of grapefruit seed extract (GSE), an antimicrobial agent, was added to the film-forming solution just before casting and the ability of the plastic matrix to release the additive was then evaluated in vitro against 2 GSE-susceptible microorganisms, Salmonella enteritidis and Listeria innocua. The results indicate that the developed matrix may be a promising food-grade material for the incorporation of active substances.

  1. Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes.

    PubMed

    Pakzad, A; Simonsen, J; Yassar, R S

    2012-02-01

    In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content.

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

    PubMed Central

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

    2014-01-01

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

  3. Properties of hot-melt extruded theophylline tablets containing poly(vinyl acetate).

    PubMed

    Zhang, F; McGinity, J W

    2000-09-01

    The objectives of this study were to investigate the properties of poly(vinyl acetate) (PVAc) as a retardant polymer and to study the drug release mechanism of theophylline from matrix tablets prepared by hot-melt extrusion. A physical mixture of drug, polymer, and drug release modifiers was fed into the equipment and heated inside the barrel of the extruder. The cylindrical extrudates were either cut into tablets or ground into granules and compressed with other excipients into tablets. Due to the low glass transition temperature of the PVAc, the melt extrusion process was conducted at approximately 70 degrees C. Theophylline was used as the model drug in this study. Theophylline was present in the extrudate in its crystalline form and was released from the tablets by diffusion. The Higuchi diffusion model and percolation theories were applied to the dissolution data to explain the drug release properties of the matrix systems. The release rate was shown to be dependent on the granule size, drug particle size, and drug loading in the tablets. Water-soluble polymers were demonstrated to be efficient release rate modifiers for this system.

  4. A poly(vinyl alcohol)/sodium alginate blend monolith with nanoscale porous structure.

    PubMed

    Sun, Xiaoxia; Uyama, Hiroshi

    2013-10-04

    A stimuli-responsive poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend monolith with nanoscale porous (mesoporous) structure is successfully fabricated by thermally impacted non-solvent induced phase separation (TINIPS) method. The PVA/SA blend monolith with different SA contents is conveniently fabricated in an aqueous methanol without any templates. The solvent suitable for the fabrication of the present blend monolith by TINIPS is different with that of the PVA monolith. The nanostructural control of the blend monolith is readily achieved by optimizing the fabrication conditions. Brunauer Emmett Teller measurement shows that the obtained blend monolith has a large surface area. Pore size distribution plot for the blend monolith obtained by the non-local density functional theory method reveals the existence of the nanoscale porous structure. Fourier transform infrared analysis reveals the strong interactions between PVA and SA. The pH-responsive property of the blend monolith is investigated on the basis of swelling ratio in different pH solutions. The present blend monolith of biocompatible and biodegradable PVA and SA with nanoscale porous structure has large potential for applications in biomedical and environmental fields.

  5. Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol).

    PubMed

    Sukhlaaied, Wattana; Riyajan, Sa-Ad

    2013-10-15

    The aim of this work was to prepare a carrageenan-g-poly(vinyl alcohol) (CG-g-PVA) polymer using potassium persulphate as an initiator. The effect of different ratios of the polymer blends on the parameters of the grafted polymer was investigated. The grafting ratio decreased with an increase of the CG content in the graft copolymer. The resulting CG-g-PVA was characterized by ATR-FTIR, tensile strength, elongation at break, swelling ratio, contact angle and biodegradation in soil. From the ATR-FTIR the 3,6-anhydride-galactose of the CG showed a peak at 927 cm(-1) that was absent in the CG-g-PVA and the ether linkage of PVA-g-CG between the hydroxyl group of PVA and the 3,6-anhydride-galactose of CG showed a peak at 1089 cm(-1) in the graft copolymer. The tensile strength and elongation at break decreased with an increase of the CG due to its phase separation. The highest tensile strength was observed at 2:8 CG/PVA. In addition, the swelling ratio decreased and the contact angle increased as a function of the increase of the CG in the grafted copolymer. The best ratio of CG-g-PVA was 2:8 CG/PVA. This graft copolymer was easily biodegraded in natural soil. Copyright © 2013. Published by Elsevier Ltd.

  6. Fabrication of antibacterial blend film from poly (vinyl alcohol) and quaternized chitosan for packaging

    SciTech Connect

    Hu, Dongying; Wang, Lijuan

    2016-06-15

    Highlights: • HTCC/PVA blend films were prepared through a simple mixing method. • The blend films had greater elongation at break and good optical transmittance. • The blend films had low oxygen permeability and water vapor permeability. • The films had good activity against Escherichia coli and Staphylococcus aureus. - Abstract: Blend films from poly (vinyl alcohol) (PVA) containing N-(2-hydroxy) propyl-3-trimethyl ammonium chloride chitosan (HTCC) were prepared via a simple mixing and casting method. The films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction measurements (XRD), scanning electron microscopy and ultraviolet-visible measurements (UV–vis). The effects of HTCC amount on mechanical properties, oxygen permeability, water vapor permeation, and antibacterial properties against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) of the films were investigated. FTIR and XRD analysis show that HTCC and PVA in the blend films interacted by hydrogen bonding. SEM and UV–vis analysis reveal the good compatibility between HTCC and PVA. Compared with pure PVA film, the blend films had greater elongation at break, lower water permeability, and higher antibacterial activity. The HTCC addition decreased the tensile strength and the light transmittance. The results suggest that HTCC/PVA blend films have a potential as packaging materials.

  7. Silver nanoparticle/chitosan oligosaccharide/poly(vinyl alcohol) nanofibers as wound dressings: a preclinical study.

    PubMed

    Li, Chenwen; Fu, Ruoqiu; Yu, Caiping; Li, Zhuoheng; Guan, Haiyan; Hu, Daqiang; Zhao, Dehua; Lu, Laichun

    2013-01-01

    In this study, a mixture of poly(vinyl alcohol) (PVA) and chitosan oligosaccharides (COS) was electrospun with silver nanoparticles (AgNPs) to produce fibrous mats for use in wound healing. The AgNPs were reduced by COS prior to electrospinning or Ag(+) was reduced via ultraviolet irradiation in nanofibers. The morphologies of the PVA/COS/AgNO3 and PVA/COS-AgNP nanofibers were analyzed by scanning electron microscopy. Formation of the AgNPs was investigated by field emission transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. We also evaluated the biocompatibility of the nanofibers, particularly their cytotoxicity to human skin fibroblasts and potential to cause primary skin irritation. The in vitro antibacterial activity and in vivo wound healing capacity of the nanofibers were also investigated. The nanofibers had a smooth surface with an average diameter of 130-192 nm. The diameters of the AgNPs were in the range of 15-22 nm. The nanofibers significantly inhibited growth of Escherichia coli and Staphylococcus aureus bacteria. PVA/COS-AgNP nanofibers accelerated the rate of wound healing over that of the control (gauze). The results of our in vitro and in vivo animal experiments suggest that PVA/COS-AgNP nanofibers should be of greater interest than PVA/COS/AgNO3 nanofibers for clinical use as a bioactive wound dressing.

  8. Bubble template fabrication of chitosan/poly(vinyl alcohol) sponges for wound dressing applications.

    PubMed

    Chen, Changfeng; Liu, Li; Huang, Tao; Wang, Qiong; Fang, Yue'e

    2013-11-01

    The present investigation involves the synthesis of chitosan based composite sponges in view of their applications in wound dressing, antibacterial and haemostatic. A facile CO2 bubbles template freeze-drying method was developed for the fabrication of macroporous chitosan-poly(vinyl alcohol) (PVA) composite sponges with a typical porosity of 50% and pore size of 100-300 μm. Effects of the content of cross-linking agent and PVA on morphology, mechanical properties, water uptake and moisture permeability were examined. The macroporous chitosan/PVA composite sponges exhibited an enhanced water absorption capacity over those reported microporous chitosan sponges prepared using traditional free-drying methods. Improved strength and flexibility of the chitosan sponges were observed with the presence of PVA. Further, the antibacterial and haemostatic activities have been also demonstrated. The chitosan/PVA composite sponges showed higher haemostatic activity than pure chitosan sponges and solutions. Erythrocytes cells bind first to the surface of chitosan polymer in the sponges and then promote the binding with other cells in the solution. The chitosan/PVA sponges of high liquid absorbing, appropriate moisture permeability, antimicrobial property and unique haemostatic behavior can be used for wound dressing applications.

  9. Biocompatible poly(vinyl alcohol) nanoparticle-based binary blends for oil spill control.

    PubMed

    Fouad, Rasha Refaat; Aljohani, Hind Abdullah; Shoueir, Kamel Rizq

    2016-11-15

    In the current study, biocompatible and biodegradable blends based on poly(vinyl alcohol) nanoparticles - PVAn mixed with either chitosan (Ch) or starch (St) - were prepared and investigated as nanoabsorbents for oil elimination from wastewater. The use of water/dimethyl sulfoxide (DMSO) as a mixed solvent is the key factor for preparing aggregated PVAn, which is further mixed with Ch or St. Nanoblends were applied as oil absorbents, and the results showed that PVAn/St possess high adsorption capacity than PVAn/Ch and PVAn. The maximum sorption capacities (qg/g) of the PVAn/Ch sorbents for hydraulic oil, kerosene, and toluene were 33.6, 73.96, and 93.1g/g, respectively. The absorbed oil could be rapidly recovered by simple mechanical squeezing and reused without any other modification. The blends showed excellent reusability and could be reused for at least 10 times with minimal losses. The current study demonstrates the application of these blends as an ideal alternative sorbent for oil spillage cleanup. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  10. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    DOE PAGES

    Patel, Mogon; Pitts, Simon; Beavis, Peter; ...

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageingmore » induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.« less

  11. Radiation crosslinking and scission of poly(vinyl methyl ether) in aqueous solution

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Rosiak, Janusz M.

    2002-03-01

    For a wide range of poly(vinyl methyl ether) (PMVE) concentrations (1-16 g dm -3), in anoxic conditions, polymer-derived radicals recombine in two major pathways: (i) crosslinking and (ii) disproportionation. Both these processes proceed inter- and intramolecularly. The radiation-chemical yields and kinetics of crosslinking have been studied by pulse radiolysis with light scattering intensity detection (LSI). In the absence of oxygen, G-values of intermolecular crosslinking were determined on the basis of LSI changes versus applied dose and compared with the results obtained previously for γ-irradiated samples. It has been found that the first half-life time of intermolecular crosslinking decreases with increasing dose per pulse. Addition of small amounts of macroradical scavenger (cysteamine hydrochloride) decreases, drastically, the increase of LSI signal. On increasing the PVME concentration, intermolecular crosslinking becomes more efficient. In the presence of oxygen, for diluted PVME solution (0.1 g dm -3), decrease of LSI signal consisting of the kinetic of a first-order reaction was observed. The rate constant of LSI decrease was found to be 1.1×10 3 s -1 and it was attributed to the main-chain scission.

  12. Rate-dependent Mechanical Deformation Behavior of POSS-filled and Plasticized Poly(vinyl chloride).

    NASA Astrophysics Data System (ADS)

    Soong, Sharon; Cohen, Robert; Boyce, Mary

    2006-03-01

    In different temperatures or strain-rate regimes, the rate sensitivities of polymers change as various primary and secondary molecular mobility mechanisms are accessed. Incorporating nanoparticles into the polymer matrix can potentially alter the molecular level structure and offers an opportunity to tailor the rate-dependent mechanical deformation behavior of the polymer. In this study, methacryl-POSS (C56H88O28Si8) and dioctyl phthalate (DOP) were incorporated into poly(vinyl chloride) (PVC) through melt blending. Dynamic Mechanical Analysis revealed that the incorporation of POSS in PVC plasticizes PVC and reduces both the alpha and beta transition temperatures. As for the PVC/DOP blends, while the alpha-transition temperatures were reduced, beta-motions vanishes with high DOP contents. The rate dependent yield behavior is characterized in compression testing. Zwick Mechine is used for low to moderate strain rate (0.0001 to 0.1/s) and Split Hopkinson Bar is used for high strain rate (500 to 2000/s). It was found that PVC with POSS shows a delay in yield strength rate-sensitivity transition. For PVC with higher DOP contents which show restricted beta-motions, the rate-sensitivity transition in yield stress faded away. Constitutive model used was able to predict the rate-sensitivity transitions in the compression yield behavior of PVC compounds.

  13. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    SciTech Connect

    Patel, Mogon; Pitts, Simon; Beavis, Peter; Robinson, Mathew; Morrell, Paul; Khan, Niaz; Khan, Imran; Pockett, Nicola; Letant, Sonia; Von White, Gregory; Labouriau, Andrea

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageing induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.

  14. Permanent hydrophilic modification of polypropylene and poly(vinyl alcohol) films by vacuum ultraviolet radiation

    NASA Astrophysics Data System (ADS)

    Belmonte, Guilherme Kretzmann; Charles, German; Strumia, Miriam Cristina; Weibel, Daniel Eduardo

    2016-09-01

    Polypropylene (PP) and Poly(vinyl alcohol) (PVA) both synthetics polymers but one of them biodegradable, were surface modified by vacuum ultraviolet (VUV) irradiation. After VUV irradiation in an inert nitrogen atmosphere, the films were exposed to oxygen gas. The treated films were characterized by water contact angle measurements (WCA), optical profilometry, FTIR-ATR, XPS, UPS and NEXAFS techniques. PP and PVA VUV-treated films reached superhydrophilic conditions (WCAs <10°) in about 30 min of irradiation under our experimental conditions. It was observed that when the WCAs reached about 35-40° the hydrophilicity was permanent in both polymers. These results contrasted with typical plasma treatments were a rapid hydrophobic recovery with aging time is usually observed. UPS and XPS data showed the presence of new functionalities on the PP and PVA surfaces that were assigned to COO, Cdbnd O, Csbnd O and Cdbnd C functional groups. Finally, grafting of styrene (ST) as a typical monomer was tested on PP films. It was confirmed that only in the VUV irradiated region an efficient grafting of ST or polymerized ST was found. Outside the irradiated regions no ST grafted was observed. Our results showed the potential use of VUV treatment for surface modification and processing of polymers which lack chromophores in the UV region.

  15. Mesoscopic and microscopic investigation on poly(vinyl alcohol) hydrogels in the presence of sodium decylsulfate.

    PubMed

    Mangiapia, Gaetano; Ricciardi, Rosa; Auriemma, Finizia; Rosa, Claudio De; Celso, Fabrizio Lo; Triolo, Roberto; Heenan, Richard K; Radulescu, Aurel; Tedeschi, Anna Maria; D'Errico, Gerardino; Paduano, Luigi

    2007-03-08

    The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueous solutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined use of small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogels may be described in terms of polymer rich regions, with dimensions of the order of 1-2 microm, dispersed in a water rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a network where the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of approximately 45 A. The structural organization of freeze/thaw PVA hydrogel membranes does not change either after rehydration of dried gels or in the presence of a tensile force. Finally, addition of surfactant micelles inside the gel provides a formulation with both hydrophobic and hydrophilic regions, which demonstrates the potential of the system for drug delivery. Both SANS and EPR measurements show that sodium decylsulfate (C10OS) micelles do not significantly interact with the PVA gel. Variation of the gel structure by the number of freeze/thaw cycles should modulate the rate of release of an active constituent, for example, in a dermal patch.

  16. A facile method for electrospinning of Ag nanoparticles/poly (vinyl alcohol)/carboxymethyl-chitosan nanofibers

    NASA Astrophysics Data System (ADS)

    Zhao, Yinghui; Zhou, Ying; Wu, Xiaomian; Wang, Lu; Xu, Ling; Wei, Shicheng

    2012-09-01

    A facile method to prepare silver nanoparticles (AgNPs) containing nanofibers via electrospinning has been demonstrated. AgNPs were in situ synthesized in poly (vinyl alcohol) (PVA)/carboxymethyl-chitosan (CM-chitosan) blend aqueous solution before electrospinning. UV-vis spectra, viscosity and conductivity of the electrospinning solution were measured to investigate their effects on the electrospinning procedure. The morphology of AgNPs/PVA/CM-chitosan nanofibers was observed by Field Emission Scanning Electron Microscopy. The formation and morphology of AgNPs were investigated by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. The resulted nanofibers have smooth surface and uniform diameters ranging from 295 to 343 nm. The diameters of AgNPs mainly distributed in the range of 4-14 nm, and the electrostatic interaction between AgNPs and fibers was observed. Finally, in vitro Ag release from the nanofibers was measured and the antibacterial behavior of the nanofibers against Escherichia coli was studied by bacterial growth inhibition halos and bactericidal kinetic testing. The AgNPs/PVA/CM-chitosan nanofibers possessed certain antibacterial ability, which makes them capable for antibacterial biomaterials.

  17. Poly(vinyl alcohol) hydrogel as a biocompatible viscoelastic mimetic for articular cartilage.

    PubMed

    Grant, Colin; Twigg, Pete; Egan, Alex; Moody, Alexandra; Smith, Annie; Eagland, Donald; Crowther, Nicholas; Britland, Steve

    2006-01-01

    The prevalence of suboptimal outcome for surgical interventions in the treatment of full-thickness articular cartilage damage suggests that there is scope for a materials-based strategy to deliver a more durable repair. Given that the superficial layer of articular cartilage creates and sustains the tribological function of synovial joints, it is logical that candidate materials should have surface viscoelastic properties that mimic native articular cartilage. The present paper describes force spectroscopy analysis by nano-indentation to measure the elastic modulus of the surface of a novel poly(vinyl alcohol) hydrogel with therapeutic potential as a joint implant. More than 1 order of magnitude decrease in the elastic modulus was detected after adsorption of a hyaluronic acid layer onto the hydrogel, bringing it very close to previously reported values for articular cartilage. Covalent derivatization of the hydrogel surface with fibronectin facilitated the adhesion and growth of cultured rat tibial condyle chondrocytes as evidenced morphologically and by the observance of metachromatic staining with toluidine blue dye. The present results indicate that hydrogel materials with potential therapeutic benefit for injured and diseased joints can be engineered with surfaces with biomechanical properties similar to those of native tissue and are accepted as such by their constituent cell type.

  18. Conductive, tough, hydrophilic poly(vinyl alcohol)/graphene hybrid fibers for wearable supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, Shaohua; Ma, Wujun; Xiang, Hengxue; Cheng, Yanhua; Yang, Shengyuan; Weng, Wei; Zhu, Meifang

    2016-07-01

    Graphene fibers based flexible supercapacitors have great potential as wearable power sources for textile electronics. However, their electrochemical performance is limited by the serious stacking of graphene sheets and their hydrophobicity in aqueous electrolytes. Meanwhile, their brittleness is unfavorable for practical application. Incorporation of nanofillers into graphene fibers has been proved effective for enhancing their capacitance, whereas often leading to deteriorated mechanical strength. Herein we demonstrate that the strength, toughness and capacitive performance of graphene-based fibers can be significantly enhanced simultaneously, simply by incorporating hydrophilic poly(vinyl alcohol) (PVA) into a non-liquid-crystalline graphene oxide (GO) dispersion before wet spinning and chemical reduction. The structure and properties of the resulted PVA/graphene hybrid fibers are systematically investigated, and the mechanism behind these enhancements is discussed in detail. The hybrid fiber with a PVA/GO weight ratio of 10/90 possesses a strength of 186 MPa, a toughness of 11.3 J cm-3, and a capacitance of 241 F cm-3 in 1 M H2SO4. A solid-state yarn supercapacitor assembled from these fibers exhibits a device energy of 5.97 mW h cm-3, and features excellent flexibility and bending stability. This device is robust enough to be integrated into textile and thus promising as wearable power supply for smart textiles.

  19. Gold nanoparticles reinforced poly (vinyl alcohol) of self-standing optical films.

    PubMed

    Ram, S; Tripathy, P; Fecht, H J

    2007-09-01

    A simple one-step process is developed to synthesize self-standing optical films of Au-doped polymer of poly(vinyl alcohol) (PVA). The visible color could be tuned precisely over a wide range from the violet to a yellowish with selective Au-contents from 0.1 to 5.0 wt%. The synthetic procedure involves a caloric Au3+ --> Au reaction in aqueous PVA at 60-90 degrees C temperatures followed by casting the sample (Au-nanocrystals (NCs) embedding in the PVA polymer molecules) as films or other shapes. Stable color persists of nanocolloids as well as films. The NCs are thin platelets of triangular, square, rectangular, or hexagonal shapes. There are very few pentagonal platelets and nanorods. As analyzed with microstructure, the NCs formation results in a structural anisotropy by the preferential adsorption of PVA on selective facets. An Au-content dependent emission occurs in the 400-650 nm regions, useful for possible optical data storage, nonlinear optical devices, and color pigments.

  20. Acoustic Behavior of Subfloor Lightweight Mortars Containing Micronized Poly (Ethylene Vinyl Acetate) (EVA)

    PubMed Central

    Brancher, Luiza R.; Nunes, Maria Fernanda de O.; Grisa, Ana Maria C.; Pagnussat, Daniel T.; Zeni, Mára

    2016-01-01

    This paper aims to contribute to acoustical comfort in buildings by presenting a study about the polymer waste micronized poly (ethylene vinyl acetate) (EVA) to be used in mortars for impact sound insulation in subfloor systems. The evaluation method included physical, mechanical and morphological properties of the mortar developed with three distinct thicknesses designs (3, 5, and 7 cm) with replacement percentage of the natural aggregate by 10%, 25%, and 50% EVA. Microscopy analysis showed the surface deposition of cement on EVA, with preservation of polymer porosity. The compressive creep test estimated long-term deformation, where the 10% EVA sample with a 7 cm thick mortar showed the lowest percentage deformation of its height. The impact noise test was performed with 50% EVA samples, reaching an impact sound insulation of 23 dB when the uncovered slab was compared with the 7 cm thick subfloor mortar. Polymer waste addition decreased the mortar compressive strength, and EVA displayed characteristics of an influential material to intensify other features of the composite. PMID:28787851

  1. Fabrication of low-fire-hazard flexible poly (vinyl chloride) via reutilization of heavy metal biosorbents.

    PubMed

    Pan, Ye-Tang; Wang, De-Yi

    2017-10-05

    As a naturally abundant biopolymer, chitosan is considered to be a suitable adsorbent for stannate (SnO3(2-)) in tin plating wastewater. However, mass transfer of the adsorbent and its recycling remain challenging problems. Though flexible poly(vinyl chloride) (PVC) is highly flammable due to the addition of plasticizers, the traditional flame retardant, antimony trioxide (Sb2O3), is potentially harmful. In this study, chitosan was anchored onto the surface of PVC resin to adsorb SnO3(2-) from wastewater. Thereafter, tin-doped chitosan-coated PVC resin was readily recycled and processed into a flexible PVC composite (modified fPVC). The limiting oxygen index value of the modified fPVC increased to 33.1%, and the peak heat release rate decreased to 161kW/m(2). In addition to reducing fire hazards, this approach also decreased the content of harmful hydrogen chloride gas released during the combustion of modified fPVC. Meanwhile, the tensile properties of modified fPVC were enhanced compared with those of the Sb2O3-treated sample. These results indicated the synthesis of an eco-friendly Sb2O3-free flexible PVC composite that poses a low fire hazard. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Superstretchable Nacre-Mimetic Graphene/Poly(vinyl alcohol) Composite Film Based on Interfacial Architectural Engineering.

    PubMed

    Zhao, Nifang; Yang, Miao; Zhao, Qian; Gao, Weiwei; Xie, Tao; Bai, Hao

    2017-05-23

    Through designing hierarchical structures, particularly optimizing the chemical and architectural interactions at its inorganic/organic interface, nacre has achieved an excellent combination of contradictory mechanical properties such as strength and toughness, which is highly demanded yet difficult to achieve by most synthetic materials. Most techniques applied to develop nacre-mimetic composites have been focused on mimicking the "brick-and-mortar" structure, but the interfacial architectural features, especially the asperities and mineral bridges of "bricks", have been rarely concerned, which are of equal importance for enhancing mechanical properties of nacre. Here, we used a modified bidirectional freezing method followed by uniaxial pressing and chemical reduction to assemble a nacre-mimetic graphene/poly(vinyl alcohol) composite film, with both asperities and bridges introduced in addition to the lamellar layers to mimic the interfacial architectural interactions found in nacre. As such, we have developed a composite film that is not only strong (up to ∼150.9 MPa), but also tough (up to ∼8.50 MJ/m(3)), and highly stretchable (up to ∼10.44%), difficult to obtain by other methods. This was all achieved by only interfacial architectural engineering within the traditional "brick-and-mortar" structure, without introducing a third component or employing chemical cross-linker as in some other nacre-mimetic systems. More importantly, we believe that the design principles and processing strategies reported here can also be applied to other material systems to develop strong and stretchable materials.

  3. Controlled release of retinyl acetate from β-cyclodextrin functionalized poly(vinyl alcohol) electrospun nanofibers.

    PubMed

    Lemma, Solomon M; Scampicchio, Matteo; Mahon, Peter J; Sbarski, Igor; Wang, James; Kingshott, Peter

    2015-04-08

    Retinyl acetate (RA) was effectively incorporated into electrospun nanofibers of poly(vinyl alcohol) (PVA) containing β-cyclodextrin (β-CD) in order to form inclusion complexes for encapsulation to prolong shelf life and thermal stability. The physical and thermal properties of encapsulated RA were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The nanofibers of PVA/RA and PVA/RA/β-CD exhibited bead free average fiber diameters of 264 ± 61 and 223 ± 49 nm, respectively. The surface chemistry of the functional nanofibers was investigated by X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) demonstrated different thermal stabilities between the bioactive and the polymer, with and without β-CD. Square-wave voltammogram peak current changes were used to follow the release kinetics of RA from the nanofibers. Results indicate that RA coated inside PVA/β-CD nanofibers was protected against oxidation much better than RA in PVA nanofibers and should extend the shelf life. In addition, RA encapsulated in the PVA/β-CD had better thermal stability than PVA nanofibers.

  4. Evaluation of cellulose and carboxymethyl cellulose/poly(vinyl alcohol) membranes.

    PubMed

    Ibrahim, Maha M; Koschella, Andreas; Kadry, Ghada; Heinze, Thomas

    2013-06-05

    Cellulose was isolated from rice straw and converted to carboxymethyl cellulose (CMC). Both polymers were crosslinked with poly(vinyl alcholo) (PVA). The physical properties of the resulting membranes were characterized by FT-IR, TGA, DSC and SEM. The cellulose and CMC were first prepared from bleached rice straw pulp. The infrared spectroscopy of the resulting polymer membranes indicated a decrease in the absorbance of the OH group at 3300-3400 cm(-1), which is due to bond formation with either the cellulose or CMC with the PVA. The thermal stability of PVA/cellulose and PVA/CMC membranes was lower than PVA membrane. The surface of the resulting polymer membranes showed smooth surface in case of the PVA/CMC membrane and rough surface in case of the PVA/cellulose membrane. Desalination test, using 0.2% NaCl, showed that pure PVA membranes had no effect while membranes containing either cellulose or CMC as filler were able to decrease the content of the NaCl from the solution by 25% and 15%, respectively. Transport properties, including water and chloroform vapor were studied. The moisture transport was reduced by the presence of both cellulose and CMC. Moreover, the membranes containing cellulose and CMC showed significantly reduced flux compared to the pure PVA. The water sorption, solubility and soaking period at different pH solutions were also studied and showed that the presence of both cellulose and CMC influences the properties.

  5. Poly(vinyl alcohol)/sodium alginate/layered silicate based nanofibrous mats for bacterial inhibition.

    PubMed

    Li, Wei; Li, Xueyong; Chen, Yang; Li, Xiaoxia; Deng, Hongbing; Wang, Ting; Huang, Rong; Fan, Gang

    2013-02-15

    Poly(vinyl alcohol) (PVA)/sodium alginate (ALG)/organic rectorite (OREC) composite nanofibrous mats are fabricated by electrospinning aqueous solutions with different mixing ratios. Both good fiber shape and three-dimensional structure of nanofibrous mats can be observed by Field Emission Scanning Electron Microscopy. Energy-dispersive X-ray spectroscopy shows the existence of OREC in the as-spun composite mats. In addition, small-angle X-ray diffraction confirms that the interlayer of OREC is intercalated by ALG/PVA chains, and the distance between OREC interlayers is increased from 4.50 to 4.74 nm. Wide angle X-ray diffraction and Fourier transform infrared spectra further verify the intercalation is between polymers and layered silicate. Moreover, the thermal gravimetric analysis shows that the addition of OREC has only a small effect on the thermal stability of composites. Furthermore, the antibacterial experiments illustrate that OREC can enhance the bacterial inhibition ability of nanofibrous mats against Escherichia coli and Staphylococcus aureus.

  6. Chromaticity and color saturation of ultraviolet irradiated poly(vinyl alcohol)-anthocyanin coatings

    NASA Astrophysics Data System (ADS)

    Mat Nor, N. A.; Aziz, N.; Mohd-Adnan, A. F.; Taha, R. M.; Arof, A. K.

    2016-06-01

    The purpose of this paper is to evaluate the chromaticity and color saturation of anthocyanin extraction from fruit pericarps of Ixora siamensis in a poly(vinyl alcohol) (PVA) matrix. The colored PVA matrix was exposed to UV-B irradiation for 93 days at UV intensity of 17.55 lux. Anthocyanin colorant has been extracted using methanol acidified with 0.5% trifluoroacetic acid (TFA). Different concentrations of ferulic acid (FA) (0, 1, 2, 3, 4 and 5 wt.%) have been added to the anthocyanin extractions before mixing with PVA to form a coating system. The PVA-anthocyanin-FA mixtures have been coated on glass slides and kept overnight in the dark for curing before exposure to UV-B irradiation. The FA-free sample undergoes more color degradation compared to samples containing FA. The coating with 2% FA has the most stable color with chromaticity of 41% and color saturation of 0.88 compared to other FA containing coats. The FA-free coat exhibits 29% chromaticity and color saturation of 0.38 at the end of the experiment.

  7. Heterogeneous structure of poly(vinyl chloride) as the origin of anomalous dynamical behavior

    NASA Astrophysics Data System (ADS)

    Arbe, A.; Moral, A.; Alegria, A.; Colmenero, J.; Pyckhout-Hintzen, W.; Richter, D.; Farago, B.; Frick, B.

    2002-07-01

    We have investigated the thermal evolution of the structure and the dynamics of poly(vinyl chloride) (PVC) in a wide temperature range. Corroborating earlier findings, small angle neutron scattering revealed the presence of structural heterogeneities. On the other hand, the single chain form factor corresponds to that of Gaussian chains. Gradually with increasing temperature the system becomes homogeneous. A simple description of the heterogeneities in terms of microcrystallites is forwarded. The dynamical behavior of PVC has been investigated combining broadband dielectric spectroscopy (DS) with coherent and incoherent neutron scattering. In a wide temperature range broadband DS facilitated a precise determination of the dynamic response related to the segmental relaxation. Close to the glass transition temperature the line shape strongly deviates from the usual Kohlrausch-Williams-Watts functional form of common glassforming systems. Moreover, the characteristic relaxation time observed by incoherent scattering displays an anomalous dependence on momentum transfer indicating the possible existence of heterogeneities in the sample. Based on the structural and dynamical results, a model is proposed, that considers the coexistence of regions with different dynamical properties leading to a distribution of characteristic relaxation times. The model accounts for the experimental observations, assuming for all regions the same functional form for the alpha-relaxation. It may be univocally determined from the coherent scattering data at the first static structure peak. The distribution of relaxation times found is compatible with the distribution of only one variable, the glass transition temperature.

  8. Bioreactor validation and biocompatibility of Ag/poly(N-vinyl-2-pyrrolidone) hydrogel nanocomposites.

    PubMed

    Jovanović, Zeljka; Radosavljević, Aleksandra; Kačarević-Popović, Zorica; Stojkovska, Jasmina; Perić-Grujić, Aleksandra; Ristić, Mirjana; Matić, Ivana Z; Juranić, Zorica D; Obradovic, Bojana; Mišković-Stanković, Vesna

    2013-05-01

    Silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) nanocomposites containing Ag nanoparticles at different concentrations were synthesized using γ-irradiation. Cytotoxicity of the obtained nanocomposites was determined by MTT assay in monolayer cultures of normal human immunocompetent peripheral blood mononuclear cells (PBMC) that were either non-stimulated or stimulated to proliferate by mitogen phytohemagglutinin (PHA), as well as in human cervix adenocarcinoma cell (HeLa) cultures. Silver release kinetics and mechanical properties of nanocomposites were investigated under bioreactor conditions in the simulated body fluid (SBF) at 37°C. The release of silver was monitored under static conditions, and in two types of bioreactors: perfusion bioreactors and a bioreactor with dynamic compression coupled with SBF perfusion simulating in vivo conditions in articular cartilage. Ag/PVP nanocomposites exhibited slight cytotoxic effects against PBMC at the estimated concentration of 0.4 μmol dm(-3), with negligible variations observed amongst different cell cultures investigated. Studies of the silver release kinetics indicated internal diffusion as the rate limiting step, determined by statistically comparable results obtained at all investigated conditions. However, silver release rate was slightly higher in the bioreactor with dynamic compression coupled with SBF perfusion as compared to the other two systems indicating the influence of dynamic compression. Modelling of silver release kinetics revealed potentials for optimization of Ag/PVP nanocomposites for particular applications as wound dressings or soft tissue implants. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. FAS Grafted Electrospun Poly(vinyl alcohol) Nanofiber Membranes with Robust Superhydrophobicity for Membrane Distillation.

    PubMed

    Dong, Zhe-Qin; Wang, Bao-Juan; Ma, Xiao-hua; Wei, Yong-Ming; Xu, Zhen-Liang

    2015-10-14

    This study develops a novel type of electrospun nanofiber membranes (ENMs) with high permeability and robust superhydrophobicity for membrane distillation (MD) process by mimicking the unique unitary microstructures of ramee leaves. The superhydrophobic ENMs were fabricated by the eletrospinning of poly(vinyl alcohol) (PVA), followed by chemical cross-linking with glutaraldehyde and surface modification via low surface energy fluoroalkylsilane (FAS). The resultant FAS grafted PVA (F-PVA) nanofiber membranes were endowed with self-cleaning properties with water contact angles of 158° and sliding angles of 4° via the modification process, while retaining their high porosities and interconnected open structures. For the first time, the robust superhydrophobicity of the ENMs for MD was confirmed by testing the F-PVA nanofiber membranes under violent ultrasonic treatment and harsh chemical conditions. Furthermore, vacuum membrane distillation experiments illustrated that the F-PVA membranes presented a high and stable permeate flux of 25.2 kg/m2 h, 70% higher than those of the commercial PTFE membranes, with satisfied permeate conductivity (<5 μm/cm) during a continuous test of 16 h (3.5 wt % NaCl as the feed solution, and feed temperature and permeate pressure were set as 333 K and 9 kPa, respectively), suggesting their great potentials in myriad MD processes such as high salinity water desalination and volatile organiccompounds removal.

  10. Facile fabrication of magnetic carboxymethyl starch/poly(vinyl alcohol) composite gel for methylene blue removal.

    PubMed

    Gong, Guisheng; Zhang, Faai; Cheng, Zehong; Zhou, Li

    2015-11-01

    This study presents a simple method to fabricate magnetic carboxymethyl starch/poly(vinyl alcohol) (mCMS/PVA) composite gel. The obtained mCMS/PVA was characterized by Fourier transform infrared (FTIR) spectra, vibrating-sample magnetometer (VSM) and scanning electron microscopy (SEM) measurements. The application of mCMS/PVA as an adsorbent for removal of cationic methylene blue (MB) dye from water was investigated. Benefiting from the combined merits of carboxymethyl starch and magnetic gel, the mCMS/PVA simultaneously exhibited excellent adsorption property toward MB and convenient magnetic separation capability. The effects of initial dye concentration, contact time, pH and ionic strength on the adsorption performance of mCMS/PVA adsorbent were investigated systematically. The adsorption process of mCMS/PVA for MB fitted pseudo-second-order model and Freundlich isotherm. Moreover, desorption experiments revealed that the mCMS/PVA adsorbent could be well regenerated in ethanol solution without obvious compromise of removal efficiency even after eight cycles of desorption/adsorption. Considering the facile fabrication process and robust adsorption performance, the mCMS/PVA composite gel has great potential as a low cost adsorbent for environmental decontamination. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Plasticized poly(vinyl chloride)-based photonic crystal for ion sensing.

    PubMed

    Aki, Shoma; Endo, Tatsuro; Sueyoshi, Kenji; Hisamoto, Hideaki

    2014-12-16

    In this study, we, for the first time, developed a plasticized poly(vinyl chloride) (PVC)-based two-dimensional photonic crystal (2D-PhC) optical sensor using nanoimprint lithography (NIL), which can perform highly sensitive, fast, and selective ion sensing based on ion extraction. Concerning the principle of response, present plasticized PVC-based PhC works as a waveguide and a grating. Incident light was guided in the bulk of plasticized PVC and, then, guided light of a specific wavelength was diffracted by a periodic nanostructure. The guided and diffracted light intensity changes of PVC-based PhCs possessing various thicknesses were monitored at 580 nm; then, we found that the 0.35 μm-thick PhC film exhibited the highest diffraction intensity. For the ion-sensing application, potassium-selective sensing elements involving potassium ionophore and lipophilic dye were dissolved in a plasticized PVC-based PhC, and the K(+)-selective response was successfully observed by monitoring the diffracted peak intensity change. The present 2D-PhC optical sensor exhibited a fast response within 5 s (95% response time) due to the use of thin film, and sensitivity was 20 times higher than that of a PVC plane-film optical sensor, due to efficient collection of diffracted light by employing a periodic nanostructure of the photonic crystal.

  12. The molecular interfacial structure and plasticizer migration behavior of "green" plasticized poly(vinyl chloride).

    PubMed

    Zhang, Xiaoxian; Li, Yaoxin; Hankett, Jeanne M; Chen, Zhan

    2015-02-14

    Tributyl acetyl citrate (TBAC), a widely-used "green" plasticizer, has been extensively applied in products for daily use. In this paper, a variety of analytical tools including sum frequency generation vibrational spectroscopy (SFG), coherent anti-Stokes Raman spectroscopy (CARS), contact angle goniometry (CA), and Fourier transform infrared spectroscopy (FTIR) were applied together to investigate the molecular structures of TBAC plasticized poly(vinyl chloride) (PVC) and the migration behavior of TBAC from PVC-TBAC mixtures into water. We comprehensively examine the effects of oxygen and argon plasma treatments on the surface structures of PVC-TBAC thin films containing various bulk percentages of plasticizers and the leaching behavior of TBAC into water. It was found that TBAC is a relatively stable PVC plasticizer compared to traditional non-covalent plasticizers but is also surface active. Oxygen plasma treatment increased the hydrophilicity of TBAC-PVC surfaces, but did not enhance TBAC leaching. However, argon plasma treatment greatly enhanced the leaching of TBAC molecules from PVC plastics to water. Based on our observations, we believe that oxygen plasma treatment could be applied to TBAC plasticized PVC products to enhance surface hydrophilicity for improving the biocompatibility and antibacterial properties of PVC products. The structural information obtained in this study will ultimately facilitate a molecular level understanding of plasticized polymers, aiding in the design of PVC materials with improved properties.

  13. Preparation and characterization of oriented poly(vinyl alcohol)/carbon nanotube composite nanofibers

    NASA Astrophysics Data System (ADS)

    Shimizu, Akikazu; Kato, Hayato; Sato, Taiga; Kushida, Masahito

    2017-07-01

    Oriented nanofiber mats blended with carbon nanotubes (CNTs) are expected to be applied as cell seeding scaffolds. Biomaterials that are often used for cell seeding scaffolds generally have low mechanical strength and low electrical conductivity; thus, it has been difficult to apply them to tissues such as heart and nerve. In this study, we prepared oriented poly(vinyl alcohol) (PVA) nanofiber mats blended with various CNT concentrations (up to 10 wt %) by electrospinning using the parallel plate electrodes as collectors with applied voltage. The morphology, mechanical properties, and electrical properties of the prepared oriented nanofiber mats were measured by using various techniques such as scanning electron microscopy (SEM). The tensile strength of the oriented nanofiber mats in the applied voltage direction increased from 2.5 to 9.7 MPa with CNT concentration. Furthermore, the electrical conductivity of the oriented nanofiber mats in the applied voltage direction increased from 0.67 × 10-7 to 4.3 × 10-7 S·m-1. Also, the mechanical strength and electrical conductivity of the oriented nanofiber mats in the applied voltage direction were 3-4 and 2-3 times higher than those in the perpendicular direction, respectively.

  14. Poly(vinyl alcohol)-coated microfluidic devices for high-performance microchip electrophoresis.

    PubMed

    Belder, Detlev; Deege, Alfred; Kohler, Frank; Ludwig, Martin

    2002-10-01

    The channels of microfluidic glass chips have been coated with poly(vinyl alcohol) (PVA). Applied for microchip electrophoresis, the coated devices exhibited a suppressed electroosmotic flow and improved separation performance. The superior performance of PVA-coated channels could be demonstrated by electrophoretic separations of labeled amines and by video microscopy. While a distorted sample zone is injected using uncoated channels the application of PVA-coated channels results in an improved shape of the sample zone with less band broadening. Applying PVA-coated microchips for the separation of amines labeled with Alexa Fluor 350 even sub-second separations, utilizing a separation length of only 650 microm, could be obtained, while this was not possible using uncoated devices. By using PVA-coated devices rather than an uncoated chip a threefold increase in separation efficiencies could be observed. As the electroosmotic flow (EOF) was suppressed, the anionic compounds were detected at the anode whereas the dominant EOF in uncoated devices resulted in an effective mobility to the cathode. Besides improved separation performance another important feature of the PVA-coated channels was the suppressed adsorption of fluorescent compounds in repetitive runs which results in an improved robustness and detection sensitivity. Applying PVA-coated channels, rinsing or etching steps could be omitted while this was necessary for a reliable operation of uncoated devices.

  15. Sulfoacetic acid modifying poly(vinyl alcohol) hydrogel and its electroresponsive behavior under DC electric field

    NASA Astrophysics Data System (ADS)

    Xiang, Yu; Liu, Genqi; Zhang, Cheng; Liao, Jiae

    2013-01-01

    A strong electrolyte hydrogel was prepared by modifying poly (vinyl alcohol) hydrogel with sulfoacetic acid (SA-PVA). Its swelling properties, mechanical properties, and electroresponsive behavior in Na2SO4 solutions were studied. The results indicated that the water take-up ability of the hydrogel decreased with the increasing ionic strength of Na2SO4 solution. The Young’s modulus, elongation at break and tensile strength of the hydrogel swollen in deionized water are 1.247 MPa, 187% and 2.2 MPa, respectively. The hydrogel swollen in a Na2SO4 solution bent towards the cathode under non-contact dc electric fields, and its bending speed and equilibrium strain increased with increasing applied voltage. There is a critical ionic strength of 0.03 at which the maximum equilibrium strain of the hydrogel occurs. Also the bending behavior of hydrogel was not affected by the pH changes. By altering the direction of the applied potential cyclically, the hydrogel exhibited good reversible bending behavior. On this basis, a gel-worm was designed. Under a cyclically varying electric field (the period was 8 s, and the voltage ranged from -10 to 10 V), the walking speed was up to 15 cm min-1 in Na2SO4 solution with an ionic strength of 0.03.

  16. Effect of sonication on the mechanical properties of poly (vinyl alcohol)/carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Truong, Van-Tan; Tsang, Kelly M. C.; Keough, Shannon J.; St John, Nigel A.

    2006-12-01

    Several sonication procedures were performed on multi-walled carbon nanotubes (MWNTs) in water by varying the length of time, the output power and the type of sonicating horn. Depending on the sonicating conditions, the multi-walled carbon nanotubes (MWNTs) could be well or poorly exfoliated and dispersed. Poly (vinyl alcohol) (PVA) and MNWT (0.5 wt%) composites were cast from the PVA/MWNT aqueous mixture. Enhancement of the mechanical properties of the composites was related to two factors: (1) crystallinity formed at the PVA and MWNT interface and (2) the size of nanotube agglomerates. The poorly dispersed solution produced nanotube agglomerates with the size of 50-100 μm that did not induce crystallization at the polymer/nanotube interface. They became stress concentrators reducing the Young's modulus and the tensile strength. Optimized sonication procedures resulted in well-dispersed nanotube agglomerates of submicron dimensions efficiently enhancing the mechanical properties. As centrifugation facilitated the removal of large agglomerates, noticeable enhancement of mechanical properties of the composites was achieved.

  17. Poly(N-vinyl-2-pyrrolidone) and 1-Octyl-2-pyrrolidinone Modified Ionic Microemulsions.

    PubMed

    Beitz, T.; Kötz, J.; Wolf, G.; Kleinpeter, E.; Friberg, S. E.

    2001-08-15

    The influence of the nonionic polymer poly(N-vinyl-2-pyrrolidone) (PVP) in comparison to the surfactant 1-octyl-2-pyrrolidinone (OP) on the phase behavior of the system SDS/pentanol/xylene/water was studied. In both modified systems a strong increase in the water solubilization capacity was found, accompanied by a change in the spontaneous curvature toward zero. In the polymer-modified system an isotropic phase channel is formed with increasing polymer content that connects the L1 and the L2 phase. The lamellar liquid crystalline phase is destabilized in both cases. In the L1 phase the adsorption of PVP at the surface of the microemulsion droplets and the formation of a cluster-like structure is proven by several methods like (13)C NMR T(1) relaxation time measurments, zeta potential measurements, and rheology. In the L2 phase a modification of the interface of the inverse droplets is detected by a shift in the percolation boundary (conductivity) and (13)C NMR T(1) relaxation measurements. The formation of a cluster-like structure can be assumed on the basis of our rheological measurements. Copyright 2001 Academic Press.

  18. Poly(vinyl alcohol)-Tannic Acid Hydrogels with Excellent Mechanical Properties and Shape Memory Behaviors.

    PubMed

    Chen, Ya-Nan; Peng, Lufang; Liu, Tianqi; Wang, Yaxin; Shi, Shengjie; Wang, Huiliang

    2016-10-12

    Shape memory hydrogels have promising applications in a wide variety of fields. Here we report the facile fabrication of a novel type of shape memory hydrogels physically cross-linked with both stronger and weaker hydrogen bonding (H-bonding). Strong multiple H-bonding formed between poly(vinyl alcohol) (PVA) and tannic acid (TA) leads to their coagulation when they are physically mixed at an elevated temperature and easy gelation at room temperature. The amorphous structure and strong H-bonding endow the PVA-TA hydrogels with excellent mechanical properties, as indicated by their high tensile strengths (up to 2.88 MPa) and high elongations (up to 1100%). The stronger H-bonding between PVA and TA functions as the "permanent" cross-link and the weaker H-bonding between PVA chains as the "temporary" cross-link. The reversible breakage and formation of the weaker H-bonding imparts the PVA-TA hydrogels with excellent temperature-responsive shape memory. Wet and dried hydrogel samples with a deformed or elongated shape can recover to their original shapes when immersed in 60 °C water in a few seconds or at 125 °C in about 2.5 min, respectively.

  19. Physicochemical and morphological properties of plasticized poly(vinyl alcohol)-agar biodegradable films.

    PubMed

    Madera-Santana, T J; Freile-Pelegrín, Y; Azamar-Barrios, J A

    2014-08-01

    The effects of the addition of glycerol (GLY) on the physicochemical and morphological properties of poly(vinyl alcohol) (PVA)-agar films were reported. PVA-agar films were prepared by solution cast method, and the addition of GLY in PVA-agar films altered the optical properties, resulting in a decrease in opacity values and in the color difference (ΔE) of the films. Structural characterization using Fourier transformation infrared (FTIR) spectroscopy and X-ray diffraction (XRD) indicated that the presence of GLY altered the intensity of the bands (from 1200 to 800cm(-1)) and crystallinity. The characterization of the thermal properties indicated that an increase in the agar content produces a decrease in the melting temperature and augments the heat of fusion. Similar tendencies were observed in plasticized films, but at different magnification. The formulation that demonstrated the lowest mechanical properties contained 25wt.% agar, whereas the formulation that contained 75wt.% agar demonstrated a significant improvement. The water vapor transmission rate (WVTR) and surface morphology analysis demonstrated that the structure of PVA-agar films is reorganized upon GLY addition. The physicochemical properties of PVA-agar films using GLY as a plasticizer provide information for the application of this formulation as packaging material for specific food applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Mucus-penetrating nanoparticles made with "mucoadhesive" poly(vinyl alcohol).

    PubMed

    Popov, Alexey; Enlow, Elizabeth; Bourassa, James; Chen, Hongming

    2016-10-01

    Nanoparticles that readily penetrate mucosal layers are desirable for a variety of biomedical applications. Nevertheless, most nanoparticles tend to be immobilized in mucus via steric and/or adhesive interactions. Contrary to the established opinion that poly(vinyl alcohol) (PVA) is mucoadhesive, we discovered that coating otherwise mucoadhesive nanoparticles with certain partially hydrolyzed PVAs can aid particle mobility in mucus. We describe two approaches to producing such mucus-penetrating particles (non-covalent modification of pre-formed nanoparticles and emulsification in the presence of PVA) and provide mobility data in human cervicovaginal mucus ex vivo as measured by multiple particle tracking and bulk permeation. When coated with PVAs that are ≥95% hydrolyzed, nanoparticles as small as ~210nm were immobilized in mucus similarly to well-established mucoadhesive controls (P>0.05). However, nanoparticles coated with PVAs that are <95% hydrolyzed penetrated mucus with velocities significantly exceeding those for the mucoadhesive controls (P<0.001) and were mobile in the bulk permeation assay. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. The impedance characterization of Carbon Nanotubes - Fumed Silica Poly (vinyl alcohol) Composites

    NASA Astrophysics Data System (ADS)

    Othman, R. N.; Wilkinson, A. N.

    2016-06-01

    Carbon Nanotube (CNT) was grown on the surface of fumed silica via chemical vapor deposition (CVD) method. In this work, silica acted as a site that holds CNT together, which prevents further agglomeration during composite processing. Iron catalyst at different loading (7.5 wt. % up to 25 wt. %) was introduced via impregnation method to synthesize CNT at 1000°C, under methane flow. Floating catalyst method was used where ferrocene (2.5 wt. % and 5 wt. %) was used as starting reactants together with toluene at 760°C. The reaction time was set at 1 hour for both methods. It was later confirmed via SEM images that the floating catalyst method is more suitable to produce a large amount of CNTs. The sample synthesized via floating catalyst method at both 2.5 wt.% and 5 wt. % ferrocene was later used to prepare composites. Composite films of the particles in poly (vinyl alcohol) (PVOH) were cast and their TEM images show that the dispersion is indeed uniform. From impedance measurement, it was found that the particles synthesized via floating catalyst method were found to form an electrically-conductive percolated network with percolation threshold of 1 wt. %, obtained via percolation equation.

  2. Synthesis, characterization and applications of N-quaternized chitosan/poly(vinyl alcohol) hydrogels.

    PubMed

    Mohamed, Riham R; Abu Elella, Mahmoud H; Sabaa, Magdy W

    2015-09-01

    Hydrogels composed of N-quaternized chitosan (NQC) and poly(vinyl alcohol) (PVA) in different weight ratios (1:3), (1:1) and (3:1) chemically crosslinked by glutaraldehyde in different weight ratios – 1.0 and 5.0% – have been prepared. The prepared hydrogels were characterized via several analysis tools such as: Fourier transform IR (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Different applications have been done on NQC/PVA hydrogels including; metal ions uptake, swellability in different buffer solutions (pH: 4, 7 and 9), swellability and degradation studies in simulated body fluid (SBF) solutions and antimicrobial activity towards bacteria and fungi. The results indicated that crosslinked NQC/PVA hydrogels with glutaraldehyde (GA) are more thermallystable than non crosslinked hydrogels, NQC/PVA hydrogels swell highly in different buffer solutions as PVA content increases and the antimicrobial activity of NQC/PVA hydrogels is higher than NQC itself.

  3. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite.

    PubMed

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments.

  4. Controlled release of 5-fluorouridine from radiation-crosslinked poly(ethylene-co-vinyl acetate) films.

    PubMed

    de Queiroz, Alvaro A A; Abraham, Gustavo A; Higa, Olga Zazuco

    2006-11-01

    The effect of gamma-radiation doses of 12.5-380 kGy on the infrared spectra, gel content, mechanical properties, and the release of oxobutyl-5-fluoro-2'-deoxyuridine (OfdUrd, an antitumor agent) from poly(ethylene-co-vinyl acetate) (EVA) films was studied. The results showed that the application of radiation doses produced a crosslinking reaction leading to a maximum gel content of about 85% in the case of 150 kGy. Higher doses did not increase the gel content in EVA films. The mechanical properties (tensile strength, percentage elongation at break and Young's modulus) of all studied EVA matrices were affected by the exposure to gamma-radiation. Irradiation doses over 50 kGy caused an increase in the Young's modulus of EVA and at the same time a decrease in the strain per cent. Moreover, the network structure formed after irradiation reduced significantly the OFdUrd release from EVA films. In this manner, the radiation dose applied to the polymeric matrix modulated the release of OFdUrd, avoiding the high concentrations that may cause severe systemic toxicity. The loading of OFdUrd to EVA film triggered a slight hyperemia after implantation, while the inflammatory reaction was only observed during the first two days.

  5. Characterization methods for radiation crosslinked poly(vinyl methyl ether) hydrogels

    NASA Astrophysics Data System (ADS)

    Schmidt, Thomas; Querner, Claudia; Arndt, Karl-Friedrich

    2003-08-01

    The paper reviews recent results of radiation crosslinking of poly(vinyl methyl ether) (PVME). It will give an overview of possible characterization methods for both, soluble and crosslinked PVME. The irradiation of aqueous low concentrated PVME solutions with γ-rays of low doses results in structural changes of PVME molecules. We are able to monitor changes in the chemical structure by spectroscopic methods (IR, NMR) as well as the changes of molecular parameters (e.g. molecular weight, molecular weight distribution, branches) by classical methods for polymer characterization (size exclusion chromatography with diverse detector systems, SLS, viscosimetry). The characterization of the network parameters (crosslinking density νc, molecular weight of the network chains Mc) of PVME bulkgels crosslinked by irradiation at high dose values by classical methods (swelling and compression measurements) provides incorrect results because of the high porosity of the gels. PVME microgel particles can be prepared by irradiation of a phase separated diluted aqueous PVME solution above their lower critical solution temperature. These microgels with decreased dimensions were characterized by SLS, DLS and field emission scanning electron microscopy.

  6. Radiation crosslinking and scission parameters for poly(vinyl methyl ether) in aqueous solution

    NASA Astrophysics Data System (ADS)

    Janik, I.; Kasprzak, E.; Al-Zier, A.; Rosiak, J. M.

    2003-08-01

    In oxygen-free aqueous solutions, poly(vinyl methyl ether) (PVME) was subjected to gamma irradiation. In such conditions PVME radicals recombine by way of crosslinking. The major result of crosslinking is an increase in the average molecular weight of the polymer, which close to the gelation point tends to infinity. Further irradiation increases the amount of formed gel, while the soluble fraction - sol decreases. The basic parameters related to the radiation processing are gelation dose - Dg, as well as radiation yield of intermolecular crosslinking and scission, GX and GS, respectively. There are three general approaches for estimation of those parameters. The first method is based on the study of molecular weight changes before the gelation point. The second method combines the gel-sol as well as the swelling analysis results. The third one allows one to calculate the yield of crosslinking from the value of Dg. All of these methods of calculation were used in this work for determination of radiation parameters and results obtained are discussed.

  7. Effect of salts on the electrospinning of poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Stanger, Jonathan J.; Tucker, Nick; Staiger, Mark; Kirwan, Kerry; Coles, Stuart; Jacobs, Daniel; Larsen, Nigel

    2009-07-01

    Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept of a virtual orifice. The increase in the final fibre diameter is explained by considering the charge distribution in the jet when it behaves like a conductor compared to when it behaves like an insulator. Both mechanisms result from the increase in conductivity of the PVOH solution without significantly modifying other solution properties when salt is added.

  8. Effect of Process Parameters on Particle Removal Efficiency in Poly(vinyl alcohol) Brush Scrubber Cleaning

    NASA Astrophysics Data System (ADS)

    An, Joonho; Lee, Hyunseop; Kim, Hyoungjae; Jeong, Haedo

    2012-02-01

    Wafer cleaning is one of the most critical processes in the semiconductor device manufacturing. Poly(vinyl alcohol) (PVA) brush scrubber cleaning is much attractive when compared with traditional wet-batch cleaning which causes the cross-contamination among the wafers in a bath and environmental issues with huge amount of chemical and deionized water (DIW) usages. The mechanical forces generated from PVA brush contact can remove the particles on a wafer surface under low concentration of chemical solution without cross-contamination. In this research, we monitored the change of the dynamic forces including normal and friction force generated by PVA brush contacts during cleaning process, and also investigated the effects of scrubbing conditions of PVA brush overlap and velocity, and the surface tension (low- or high-hydrophilic) of the wafer on the particle removal efficiency. The results show that the driving mechanism to remove the particle on a wafer surface can be changed by the PVA brush overlap and velocity condition such as the hydrodynamic drag force in the brush soft contact condition and friction force in the brush hard contact condition. The particle removal efficiency is higher under the low-hydrophilic surface having a low surface tension compared to high-hydrophilic surface.

  9. Melt-processed poly(vinyl alcohol) composites filled with microcrystalline cellulose from waste cotton fabrics.

    PubMed

    Sun, Xunwen; Lu, Canhui; Liu, Yong; Zhang, Wei; Zhang, Xinxing

    2014-01-30

    Waste cotton fabrics (WCFs), which are generated in a large volume from the textile industry, have caused serious disposal problem. Recycling WCFs into value-added products is one of the vital measures for both environmental and economic benefits. In this study, microcrystalline cellulose (MCC) was prepared by acid hydrolysis of WCFs, and used as reinforcement for melt-processed poly(vinyl alcohol) (PVA) with water and formamide as plasticizer. The microstructure and mechanical properties of the melt-processed PVA/MCC composites were characterized by Fourier transform infrared spectra, Raman spectra, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, tensile tests and dynamic mechanical analysis. The results indicated that MCC could establish strong interfacial interaction with PVA through hydrogen bonding. As a result, the crystallization of PVA was confined and its melting temperature was decreased, which was beneficial for the melt-processing of PVA. Compared with the unfilled PVA, the PVA/MCC composites exhibited remarkable improvement in modulus and tensile strength.

  10. Acoustic Behavior of Subfloor Lightweight Mortars Containing Micronized Poly (Ethylene Vinyl Acetate) (EVA).

    PubMed

    Brancher, Luiza R; Nunes, Maria Fernanda de O; Grisa, Ana Maria C; Pagnussat, Daniel T; Zeni, Mára

    2016-01-15

    This paper aims to contribute to acoustical comfort in buildings by presenting a study about the polymer waste micronized poly (ethylene vinyl acetate) (EVA) to be used in mortars for impact sound insulation in subfloor systems. The evaluation method included physical, mechanical and morphological properties of the mortar developed with three distinct thicknesses designs (3, 5, and 7 cm) with replacement percentage of the natural aggregate by 10%, 25%, and 50% EVA. Microscopy analysis showed the surface deposition of cement on EVA, with preservation of polymer porosity. The compressive creep test estimated long-term deformation, where the 10% EVA sample with a 7 cm thick mortar showed the lowest percentage deformation of its height. The impact noise test was performed with 50% EVA samples, reaching an impact sound insulation of 23 dB when the uncovered slab was compared with the 7 cm thick subfloor mortar. Polymer waste addition decreased the mortar compressive strength, and EVA displayed characteristics of an influential material to intensify other features of the composite.

  11. Poly(vinyl alcohol) physical hydrogels: noncryogenic stabilization allows nano- and microscale materials design.

    PubMed

    Jensen, Bettina E B; Smith, Anton A A; Fejerskov, Betina; Postma, Almar; Senn, Philipp; Reimhult, Erik; Pla-Roca, Mateu; Isa, Lucio; Sutherland, Duncan S; Städler, Brigitte; Zelikin, Alexander N

    2011-08-16

    Physical hydrogels based on poly(vinyl alcohol), PVA, have an excellent safety profile and a successful history of biomedical applications. However, highly inhomogeneous and macroporous internal organization of these hydrogels as well as scant opportunities in bioconjugation with PVA have largely ruled out micro- and nanoscale control and precision in materials design and their use in (nano)biomedicine. To address these shortcomings, herein we report on the assembly of PVA physical hydrogels via "salting-out", a noncryogenic method. To facilitate sample visualization and analysis, we employ surface-adhered structured hydrogels created via microtransfer molding. The developed approach allows us to assemble physical hydrogels with dimensions across the length scales, from ∼100 nm to hundreds of micrometers and centimeter sized structures. We determine the effect of the PVA molecular weight, concentration, and "salting out" times on the hydrogel properties, i.e., stability in PBS, swelling, and Young's modulus using exemplary microstructures. We further report on RAFT-synthesized PVA and the functionalization of polymer terminal groups with RITC, a model fluorescent low molecular weight cargo. This conjugated PVA-RITC was then loaded into the PVA hydrogels and the cargo concentration was successfully varied across at least 3 orders of magnitude. The reported design of PVA physical hydrogels delivers methods of production of functionalized hydrogel materials toward diverse applications, specifically surface mediated drug delivery.

  12. Single-Walled Aluminosilicate Nanotube/Poly(vinyl alcohol) Nanocomposite Membranes

    SciTech Connect

    Kang, Dun-Yen; Tong, Ho Ming; Zang, Ji; Choudhury, Rudra Prosad; Sholl, David S.; Beckham, Haskell W.; Jones, Christopher W.; Nair, Sankar

    2012-05-29

    The fabrication, detailed characterization, and molecular transport properties of nanocomposite membranes containing high fractions (up to 40 vol %) of individually-dispersed aluminosilicate single-walled nanotubes (SWNTs) in poly(vinyl alcohol) (PVA), are reported. The microstructure, SWNT dispersion, SWNT dimensions, and intertubular distances within the composite membranes are characterized by scanning and transmission electron microscopy (SEM and TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), XRD rocking curve analysis, small-angle X-ray scattering (SAXS), and solid-state NMR. PVA/SWNT nanocomposite membranes prepared from SWNT gels allow uniform dispersion of individual SWNTs in the PVA matrix with a random distribution of orientations. SAXS analysis reveals the length ({approx}500 nm) and outer diameter ({approx}2.2 nm) of the dispersed SWNTs. Electron microscopy indicates good adhesion between the SWNTs and the PVA matrix without the occurrence of defects such as voids and pinholes. The transport properties of the PVA/SWNT membranes are investigated experimentally by ethanol/water mixture pervaporation measurements, computationally by grand canonical Monte Carlo and molecular dynamics, and by a macroscopic transport model for anisotropic permeation through nanotube-polymer composite membranes. The nanocomposite membranes substantially enhance the water throughput with increasing SWNT volume fraction, which leads to a moderate reduction of the water/ethanol selectivity. The model is parameterized purely from molecular simulation data with no fitted parameters, and shows reasonably good agreement with the experimental water permeability data.

  13. Properties and performance of sulfide-substituted plasticized poly(vinyl chloride) as a biomaterial.

    PubMed

    Lakshmi, S; Jayakrishnan, A

    2003-04-15

    Plasticized poly(vinyl chloride) (PVC) was surface modified by nucleophilic substitution of the chlorine atoms of PVC by sulfide ions in aqueous media in the presence of a phase-transfer catalyst (PTC) to make it migration resistant. The modified PVC was sterilized by steam autoclaving and gamma radiation and subjected to plasticizer extraction in an extraction medium such as hexane. Virtually no plasticizer migrated out of modified PVC into the medium even after prolonged incubation for 30 d. The properties of the modified surface were evaluated by contact angle measurements, scanning electron microscopy (SEM), cell-culture studies, hemolysis assay, and whole-blood clotting time measurements. The mechanical properties of modified sheets were evaluated by measurements of tensile strength and strain at break after subjecting the specimens to different modes of sterilization. The modified PVC surface showed enhanced wettability and was found to be non-hemolytic and non-cytotoxic. Whole-blood clotting profiles of unmodified and modified PVC were virtually the same. Modification imparted slight yellow color to the material. Surface modification resulted in an 8% decrease in the ultimate stress and 28% decrease in the strain at break values. The sulfide-substituted PVC was found to be blood compatible and would be useful in applications such as tubing for transfusion, dialysis etc., where migration resistance is important.

  14. Characterization of poly(vinyl chloride) aged in a bromine containing electrolyte

    SciTech Connect

    Arnold, C. Jr.; Leo, A.; Tarjani, M.

    1988-01-01

    Poly(vinyl chloride) (PVC) is being considered for use as a flow frame material in a developmental zinc/bromine battery. The choice of PVC was based on its low cost and the ease with which it can be molded into complex parts. The electrolyte used in this battery is a highly corrosive mixture of bromine, zinc bromide, zinc chloride, potassium bromide, potassium chloride and a quaternary amine salt. The quaternary salt serves to reduce the concentration of free bromine in the electrolyte by virtue of its complexing capability. It is well known that aqueous bromine is capable of oxidizing organic compounds. The purpose of the current study was to investigate the effect of a bromine electrolyte on two PVC formulations, PVC-1 and PVC-4. PVC-1 is the designation given to one of B.F. Goodrich's commercial formulations and is the present baseline material for the flow frame. PVC-4 is an experimental B.F. Goodrich formulation that was developed especially for battery applications. We sought answers to such questions as (1) does oxidation and/or bromination take place. (2) does bromine penetrate into the sample and, if so, how far. (3) how are the mechanical and morphological properties affected. and (4) are there differences in stability between PVC-1 and PVC-4. To accelerate the aging processes we aged the PVC samples at an elevated temperature in an electrolyte which did not contain any complexing agent. 5 refs., 6 figs.

  15. Lipase immobilization on epoxy-activated poly(vinyl acetate-acrylamide) microspheres.

    PubMed

    Zhang, Dong-Hao; Peng, Li-Juan; Wang, Yun; Li, Ya-Qiong

    2015-05-01

    Poly(vinyl acetate-acrylamide) microspheres with an average diameter of 2-4μm were successfully prepared and characterized via SEM and FTIR. Then the microspheres were modified with epoxy groups through reacting with epichlorohydrin and used as carriers to covalently immobilize Candida rugosa lipase. The results revealed that agitation played an important role on epoxy activation and the immobilization ratio increased with the increase of the epoxy density. On the other hand, the specific activity of the immobilized lipase as well as the activity recovery declined gradually with the increase in the immobilization ratio from 72% to 93%, which were attributed to the steric hindrance effects caused by enzyme overloading. When epoxy density was 76μmol/g microsphere, the activity recovery reached the maximum at 47.5%, and the activity of the immobilized lipase was 261.3U/g microsphere. Moreover, the thermal stability of the immobilized lipase was much better than that of the free one, which indicated potential applications of the immobilized lipase.

  16. Fabrication and characterization of hybrid nanofibers from poly(vinyl alcohol), milk protein and metal carbonates.

    PubMed

    Mahanta, Narahari; Teow, Yiwei; Valiyaveettil, Suresh

    2012-08-01

    Porous three dimensional nanofibrous membranes were fabricated from poly(vinyl alcohol) (PVA), milk protein and inorganic salts such as calcium carbonate (CaCO3) or magnesium carbonate (MgCO3). Microscopic investigations showed that the fibers have smooth morphology with an average diameter of 300-500 nm and a surface area of 5.29 m2g(-1). Thermal analysis of the composite nanofibers showed a decrease in glass transition temperature as compared to PVA nanofiber. Incorporation of CaCO3 and MgCO3 into the nanofiber matrix was confirmed by energy dispersive spectroscopy and X-ray diffraction analysis. The cytocompatibility of electrospun composite nanofiber sheets was evaluated using human lung fibroblasts (IMR-90). There was an increase in cell attachment and cell density on milk protein incorporated to PVA-CaCO3 and PVA-MgCO3 fibers within a week of cell seeding. The cytocompatibility and increase in cell adhesion property of the hybrid nanofiber may provide significant advantages for such materials in biomedical applications.

  17. Surface Modification of Poly Vinyl Chloride (PVC) Using Low Pressure Argon and Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Mahmood, Ghoranneviss; Sheila, Shahidi; Jakub, Wiener

    2010-04-01

    In this study, commercial poly vinyl chloride (PVC) films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by measuring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy (AFM). The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy (FTIR). The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp decrease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.

  18. Treatment of desizing wastewater containing poly(vinyl alcohol) by wet air oxidation

    SciTech Connect

    Chen, G.; Lei, L.; Yue, P.L.; Cen, P.

    2000-05-01

    The effectiveness of wet air oxidation (WAO) is studied in a 2-L autoclave for the treatment of desizing wastewater from man-made fiber textile plants. At an oxygen pressure of less than 2 MPa, over 30-min, chemical oxygen demand (COD) removal was found to increase from 15 to 65% when the temperature was raised from 150 to 250 C. The biodegradability of the wastewater was also simultaneously increased. Up to 90% of the COD could be removed within 120 min. A simplified reaction mechanism is proposed which involves a direct mineralization step in parallel with a step in which an intermediate is formed prior to mineralization. A kinetic model for COD removal was developed based on this reaction mechanism. The model was tested with experimental COD results over the temperature range of the experiments. The dependence of the specific reaction rate constants was found to follow the Arrhenius type of equation. The direct oxidation of poly(vinyl alcohol) (PVA) to carbon dioxide and water is the dominant reaction step. The intermediates formed are not likely to be the acetic acid but may be short segments of PVA that are easily oxidized.

  19. Early damage detection of epoxy via poly(vinyl cinnamate) mechanophore using Fourier transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Gunckel, Ryan; Nofen, Elizabeth; Hansen-Staggs, Joshua; Babcock, Shelby; Koo, Bonsung; Chattopadhyay, Aditi; Dai, Lenore L.

    2017-07-01

    The employment of mechanophores and mechanochemistry in materials has enabled the development of novel force-responsive materials. Studies exploring the force sensing capabilities of the UV-dimerized cinnamoyl moiety have shown that after severing its cyclobutane bond under an external force, the moiety will revert back to its initial fluorescent state. Current fluorescent detection methods, however, fail to properly detect cyclobutane mechanophore activation in highly opaque samples. In this study, we apply Fourier transform infrared spectroscopy technique to measure a composite’s chemical structure and examine activation of the cinnamoyl moiety’s cyclobutane bond, regardless of sample transparency. Samples containing 10 wt% poly(vinyl cinnamate) as the active mechanophore, as well as set of samples with an additional 0.5 wt% carbon nanotubes, used to create a completely opaque composite, were developed. Both composites showed an increase in peaks at 1650 cm-1 and 1635 cm-1 after strain, which correspond to the cis and trans isomers of the fluorescent double-bond in the cinnamoyl group. A statistical difference in peak height occurs as early as 4% strain—before the yield point of the composites—indicating that early signal detection is possible. This improved sensing method provides a simpler, faster method for early signal detection over fluorescent imaging.

  20. Intense quenching of fluorescence intensity of poly(vinyl pyrrolidone) molecules in presence of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Behera, M.; Ram, S.

    2013-12-01

    We study the quenching of fluorescence intensity of 40 g/L poly(vinyl pyrrolidone) PVP molecules by varying the content of gold nanoparticles (GNPs) from 1 to 5 μM in 1-butanol. A profound exponential decay of the emission band intensity in the π ← nπ* band of the PVP molecules at ~392 nm upon gradual addition of the GNPs demonstrates an existence of an excited state interaction of NPs with the PVP molecules in a gold colloid in 1-butanol. Such quenching is caused by the non-bonding electron transfer from the O-atom of carbonyl group of the PVP molecules to the surface of the GNP. X-ray photoemission spectroscopy (XPS) study corroborates the spectroscopic results. A linear Stern-Volmer plot with a quenching constant of 2.23 × 106 M-1 reveals dynamic quenching in a non-aqueous NF. A mechanism of fluorescence quenching was proposed in support of XPS and images taken from hybrid nanostructure using transmission electron microscope. Study on quenching of fluorescence intensity of PVP fluorophore in the presence of GNPs is useful for optoelectronic devices and biosensors.

  1. Preparation and Properties of Electrospun Poly (Vinyl Pyrrolidone)/Cellulose Nanocrystal/Silver Nanoparticle Composite Fibers

    PubMed Central

    Huang, Siwei; Zhou, Ling; Li, Mei-Chun; Wu, Qinglin; Kojima, Yoichi; Zhou, Dingguo

    2016-01-01

    Poly (vinyl pyrrolidone) (PVP)/cellulose nanocrystal (CNC)/silver nanoparticle composite fibers were prepared via electrospinning using N,N′-dimethylformamide (DMF) as a solvent. Rheology, morphology, thermal properties, mechanical properties, and antimicrobial activity of nanocomposites were characterized as a function of material composition. The PVP/CNC/Ag electrospun suspensions exhibited higher conductivity and better rheological properties compared with those of the pure PVP solution. The average diameter of the PVP electrospun fibers decreased with the increase in the amount of CNCs and Ag nanoparticles. Thermal stability of electrospun composite fibers was decreased with the addition of CNCs. The CNCs help increase the composite tensile strength, while the elongation at break decreased. The composite fibers included Ag nanoparticles showed improved antimicrobial activity against both the Gram-negative bacterium Escherichia coli (E. coli) and the Gram-positive bacterium Staphylococcus aureus (S. aureus). The enhanced strength and antimicrobial performances of PVP/CNC/Ag electrospun composite fibers make the mat material an attractive candidate for application in the biomedical field. PMID:28773644

  2. Preparation and properties of Starch-g-PLA/poly(vinyl alcohol) composite film.

    PubMed

    Hu, Yingmo; Wang, Qingling; Tang, Mingru

    2013-07-25

    Starch/lactic acid graft copolymer (Starch-g-PLA) was prepared by the in situ copolymerization of starch grafted with lactic acid catalyzed with sodium hydroxide, and then mixed with poly(vinyl alcohol) (PVA) to get composite films. The structures of the graft copolymer and composite films were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties, water resistance, and thermal stability were also investigated. It was found that the compatibility of Starch-g-PLA and PVA was better than that of starch and PVA in the composite films. The tensile strength and elongation at break of the Starch-g-PLA/PVA composite film increased by 69.15% and 84.22%, respectively, while the water absorption decreased by 50.39%, which overcame the shortcomings of hydrophilicity and poor mechanical properties of Starch/PVA film. Thermogravimetric analysis (TGA) also showed that the thermal stability of Starch-g-PLA/PVA film was improved compared with Starch/PVA film. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Superabsorbent hydrogel composite based on copolymer cellulose/poly (vinyl alcohol)/CNT

    SciTech Connect

    Khoerunnisa, Fitri Hendrawan,; Sonjaya, Yaya; Putri, Oceu Dwi

    2016-04-19

    Superabsorbent hydrogels are cross-linked hydrophilic polymers that can absorb and retain a large volume of water, saline solution, or physiological fluids. A distinctive superabsorbent hydrogel composite based on cellulose/ poly (vinyl alcohol)/ carbon nanotubes was successfully synthesized via the graft bio-copolymerization in an aqueous medium with glutaraldehide as a crosslinking agent. The effect of carbon nanotubes (CNT) on water absorption capacity and mechanical properties of superabsorbent composite were particularly investigated. The Fourier transform infrared spectra showed the evidence of copolymerization of hydrogel precursors as well as the interaction of CNT filler with the hydrogel matrices, as indicated by the shifting of peak intensity and position of several functional groups (O-H, C-H sp{sup 3}, C=O, C-N, C-O). The modification of hydrogel surface morphology and porosity owing to CNT insertion was also confirmed by scanning electron microscopy images. The CNT insertion improved the mechanical strength of superabsorbent hydrogel composites. Moreover, insertion of CNT into hydrogel matrix remarkably increased the swelling capacity of superabsorbent composites up to 840%. This huge water absorption capacity of hydrogel composites offers promising applications in development of superabsorbent polymers.

  4. Microencapsulation and characterization of poly(vinyl alcohol)-coated titanium dioxide particles for electrophoretic display

    NASA Astrophysics Data System (ADS)

    Lee, Jeongwoo; Hong, Jinho; Park, Dong Wha; Shim, Sang Eun

    2010-02-01

    Titanium dioxide (TiO 2) particles were coated by poly(vinyl alcohol) (PVA) via a simple method of coacervation without a conventionally practiced polymerization step. Transmission electron microscopy (TEM) images clearly showed that the successful coating was achieved on the surface of TiO 2 particles. The average thickness of PVA coating layer was about 1.07 μm and the amount of coated PVA was 1.40 wt.% relative to TiO 2. The existence of PVA layer on TiO 2 was also verified from FT-IR spectra. The PVA-coated TiO 2 particles were further microencapsulated via coacervation of gelatin and gum Arabic. Regarding the performance of the resulting microcapsules, the resulting PVA-coated TiO 2 particles showed both a good electrophoretic movement and a good bistability in the microcapsules. Therefore, these microcapsules embedding PVA-coated TiO 2 particles can be used as a good candidate for the electrophoretic displays.

  5. Adsorption of α-amylase onto poly(N-vinyl 2-pyrrolidone/itaconic acid) hydrogels

    NASA Astrophysics Data System (ADS)

    Tümtürk, Hayrettin; Çaykara, Tuncer; Kantoǧlu, Ömer; Güven, Olgun

    1999-05-01

    α-Amylase enzyme was adsorbed on poly(N-vinyl 2-pyrrolidone/itaconic acid) (P(VP/IA)) hydrogels prepared by irradiating the ternary mixtures of VP/IA/water by γ-rays at ambient temperature. The adsorption capacity of the hydrogels was determined to increase from 2.30 to 3.40 mg α-amylase/g dry gel with increasing amount of IA in gel system. Kinetic parameters were calculated as 2.51 g/dm 3 for Km and 1.67 × 10 -3 g/dm 3 min for Vmax for free enzyme and in the range of 3.88-5.02 g/dm 3 for Km and 1.62 × 10 -3-2.27 × 10 -3 g/dm 3 min for Vmax depending on the amount of IA in the hydrogel. Enzyme activities were found to increase from 49.9% to 77.4% with increasing amount of IA in the gel system and retained their activities for one month storage. On the other hand, the free enzyme loses its activity completely after 20 days.

  6. Silver nanoparticle/chitosan oligosaccharide/poly(vinyl alcohol) nanofibers as wound dressings: a preclinical study

    PubMed Central

    Li, Chenwen; Fu, Ruoqiu; Yu, Caiping; Li, Zhuoheng; Guan, Haiyan; Hu, Daqiang; Zhao, Dehua; Lu, Laichun

    2013-01-01

    In this study, a mixture of poly(vinyl alcohol) (PVA) and chitosan oligosaccharides (COS) was electrospun with silver nanoparticles (AgNPs) to produce fibrous mats for use in wound healing. The AgNPs were reduced by COS prior to electrospinning or Ag+ was reduced via ultraviolet irradiation in nanofibers. The morphologies of the PVA/COS/AgNO3 and PVA/COS-AgNP nanofibers were analyzed by scanning electron microscopy. Formation of the AgNPs was investigated by field emission transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. We also evaluated the biocompatibility of the nanofibers, particularly their cytotoxicity to human skin fibroblasts and potential to cause primary skin irritation. The in vitro antibacterial activity and in vivo wound healing capacity of the nanofibers were also investigated. The nanofibers had a smooth surface with an average diameter of 130–192 nm. The diameters of the AgNPs were in the range of 15–22 nm. The nanofibers significantly inhibited growth of Escherichia coli and Staphylococcus aureus bacteria. PVA/COS-AgNP nanofibers accelerated the rate of wound healing over that of the control (gauze). The results of our in vitro and in vivo animal experiments suggest that PVA/COS-AgNP nanofibers should be of greater interest than PVA/COS/AgNO3 nanofibers for clinical use as a bioactive wound dressing. PMID:24204142

  7. Preparation and Properties of Nano-Hydroxyapatite/Gelatin/Poly(vinyl alcohol) Composite Membrane.

    PubMed

    Liao, Haotian; Shi, Kun; Peng, Jinrong; Qu, Ying; Liao, Jinfeng; Qian, Zhiyong

    2015-06-01

    In this study, the bone-like composite membrane based on blends of gelatin (Gel), nano-hydroxyapatite (n-HA) and poly(vinyl alcohol) (PVA) was fabricated by solvent casting and evaporation methods. The effect of n-HA content and the ratio of Gel/PVA on the properties of the composite was investigated. The Gel/PVA and n-HA/Gel/PVA composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), water contact angle measurement and scanning electron microscopy (SEM). The mechanical properties of the composites were determined by tensile tests. The as prepared composite membranes exhibited hydrophobility, the water contact angle of composite membrane was 126.6 when its mass ratio of n-HA/Gel/PVA was 10/50/40. The tensile strength of composite membranes was greatly increased due to the introduction of n-HA, and the tensile strength was increased to 74.92 MPa when the mass ratio of n-HA/Gel/PVA was 10/50/40. SEM observation indicated that n-HA was dispersed in the membranes and a sea-island structure was formed in the n-HA/Gel/PVA composite membranes, resulting in a significant increase in tensile strength. The as-prepared n-HA/Gel/PVA composite membranes may be applied in the field of bone tissue engineering.

  8. Using carboxylated nanocrystalline cellulose as an additive in cellulosic paper and poly (vinyl alcohol) fiber paper.

    PubMed

    Cha, Ruitao; Wang, Chengyu; Cheng, Shaoling; He, Zhibin; Jiang, Xingyu

    2014-09-22

    Specialty paper (e.g. cigarette paper and battery diaphragm paper) requires extremely high strength properties. The addition of strength agents plays an important role in increasing strength properties of paper. Nanocrystalline cellulose (NCC), or cellulose whiskers, has the potential to enhance the strength properties of paper via improving inter-fibers bonding. This paper was to determine the potential of using carboxylated nanocrystalline cellulose (CNCC) to improve the strength properties of paper made of cellulosic fiber or poly (vinyl alcohol) (PVA) fiber. The results indicated that the addition of CNCC can effectively improve the strength properties. At a CNCC dosage of 0.7%, the tear index and tensile index of the cellulosic paper reached the maximum of 12.8 mN m2/g and 100.7 Nm/g, respectively. More importantly, when increasing the CNCC dosage from 0.1 to 1.0%, the tear index and tensile index of PVA fiber paper were increased by 67.29%, 22.55%, respectively.

  9. Gamma irradiation induced in situ synthesis of lead sulfide nanoparticles in poly(vinyl alcohol) hydrogel

    NASA Astrophysics Data System (ADS)

    Kuljanin-Jakovljević, Jadranka Ž.; Radosavljević, Aleksandra N.; Spasojević, Jelena P.; Carević, Milica V.; Mitrić, Miodrag N.; Kačarević-Popović, Zorica M.

    2017-01-01

    In this study, the nanocomposites based on semiconductor lead sulfide (PbS) nanoparticles and poly(vinyl alcohol) (PVA) were investigated. The gamma irradiation induced in situ incorporation of PbS nanoparticles in crosslinked polymer network i.e. PVA hydrogel was performed. PVA hydrogel was previously obtained also under the influence of gamma irradiation. UV-Vis absorption and X-ray diffraction measurements were employed to investigate optical and structural properties of PbS nanoparticles, respectively, and obtained results indicates the presence of nanoparticles with approximately 6 nm in diameter and face centered cubic rock-salt crystal structure. The porous morphology was confirmed by scanning electron microscopy. Swelling data revealed that investigated hydrogels (PVA and PbS-PVA nanocomposite) shows non-Fickian diffusion, indicating that both diffusion and polymer relaxation processes controlled the fluid transport. The values of diffusion coefficients have an order of magnitude 10-9 cm2/s (typical values for water diffusion in polymers) and the best fit with the experimental results showed the Etters approximation. Comparing the thermal properties of PbS-PVA xerogel nanocomposite with PVA xerogel it was observed that incorporation of PbS nanoparticles in crosslinked PVA matrix just slightly enhanced the thermal stability of nanocomposite.

  10. Char characterization-thermal decomposition chemistry of poly(vinyl alcohol)

    SciTech Connect

    Gilman, J.W.; VanderHart, D.L.; Kashiwagi, Takashi

    1995-12-01

    Currently, due to concerns over the environmental effects of halogenated compound, there is an international demand for the control of polymer flammability without the use of halogenated additives. An alternative to the use of halogenated fire retardants, which control flammability primarily in the gas phase, is to control polymer flammability by manipulating the condensed phase chemistry. Our approach is to increase the amount of char that forms during polymer combustion. Char formation reduces, through crosslinking reactions, the amount of small volatile polymer pyrolysis fragments, or fuel, available for burning in the gas phase; this, in turn reduces the amount of heat feedback to the polymer surface. The char also insulates the underlying virgin polymer. The polymer we chose to investigate was polyvinyl alcohol, PVA, because it is one of the few linear, non-halogenated, aliphatic, polymers with a measurable (approximately 4%) char yield. We report the CP/MAS {sup 13}C NMR characterization of the fundamental condensed phase processes and structures which lead to char formation during the pyrolysis of poly (vinyl-alcohol), PVA, and PVA with nonhalogenated additives.

  11. Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish

    2014-04-01

    In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.

  12. Structure and physical properties of starch/poly vinyl alcohol/sodium montmorillonite nanocomposite films.

    PubMed

    Ali, Samer S; Tang, Xiaozhi; Alavi, Sajid; Faubion, Jon

    2011-12-14

    Nanocomposites of starch, poly vinyl alcohol (PVOH), and sodium montmorillonite (Na(+)MMT) were produced by solution mixing and cast into films. Tensile strength (TS) and elongation at the break (E%) of the films ranged from 11.60 to 22.35 MPa and 28.93-211.40%, respectively, while water vapor permeability (WVP) ranged from 0.718 to 1.430 g·mm/kPa·h·m(2). In general, an increase in Na(+)MMT content (0-20%) enhanced TS and decreased E% and WVP. Use of higher molecular weight PVOH increased both TS and E% and also decreased WVP. Mechanical properties were negatively affected, but water vapor barrier properties improved with increasing starch content (0-80%). X-ray diffraction and transmission electron microscopy were used to analyze the nanostructure, and molecular conformations and interactions in the multicomponent nanocomposites were inferred from glass transition behavior. Interactions between starch and PVOH were strongest, followed by polymer/clay interactions. On the basis of this insight, a conceptual model was presented to explain the phenomena of intercalation and exfoliation in the starch/PVOH/Na(+)MMT nanocomposites.

  13. Quality testing of human albumin by capillary electrophoresis using thermally cross-linked poly(vinyl pyrrolidone)-coated fused-silica capillary.

    PubMed

    Tan, Lin; Zheng, Xiajun; Chen, Lijuan; Wang, Yanmei

    2014-10-01

    To detect the quality of medicinal human albumin by capillary electrophoresis, we produced a fused-silica capillary coated with thermally cross-linked poly(vinyl pyrrolidone) to prohibit protein adsorption. This type of capillary was easily obtained by injecting an aqueous poly(vinyl pyrrolidone) solution into a fused-silica capillary and thermally annealing it at 200°C. Notably, stable and low electro-osmotic flow was obtained in the poly(vinyl pyrrolidone)-coated capillary at pH 2.20-9.00, and the separation of a mixture of four basic proteins indicated that the poly(vinyl pyrrolidone)-coated capillary exhibits excellent repeatability and separation efficiency; moreover, the separation of these four basic proteins could even be achieved at pH 7.00. The protein recovery percentage of human serum albumin in a single-protein solution and a mixed blood proteins solution was determined to be 97.03 and 95.40% in the poly(vinyl pyrrolidone)50-3 (representing the concentration of the capillary-injected poly(vinyl pyrrolidone) aqueous solution, 50 mg/mL, and thermal annealing time, 3 h) capillary, respectively. Based on these results, we used the poly(vinyl pyrrolidone)50-3-coated capillary to quantify the protein content of human albumin, and the results obtained from run to run, day to day and capillary to capillary demonstrated that the coated capillary could be used for quality testing commercially available human albumin. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Effect of monomer sequence distribution in poly(vinyl alcohol-co-vinyl acetate) on the hydrogen bonding structure and physical properties

    NASA Astrophysics Data System (ADS)

    Tasaka, Shun; Urakawa, Osamu; Inoue, Tadashi

    2015-03-01

    It has been well known that hydrogen (H-) bonding interaction in polymer materials strongly affects their properties. For example, glass transition temperature (Tg) and terminal relaxation time increase by introducing H-bonding sites. This is because the molecular motion is restricted due to the formation of inter- and intra-chain H-bonds. For H-bonding copolymers in which H-bonding monomer and non- bonding one are incorporated, the fraction dependence of their properties has been examined so far. However, the influence of sequence distribution on their properties has not been studied in detail. In this work, we investigated the H-bonding structure and physical properties of molten poly(vinyl alcohol-co-vinyl acetate) with different monomer sequences to clarify the effect of the sequence distribution. We found that, with increasing the randomness in monomer sequences, the number of H-bonds between carbonyl group and hydroxyl (OH) group increased. Moreover, OH groups form linearly connected structure (OH-OH-OH) and its number also increases with the sequence randomness. Tg for the samples with higher sequence randomness are higher than those with lower randomness for high VOH copolymers. These results indicate that formation of larger number of H-bonds makes Tg higher.

  15. Separation of statistical poly[(N-vinyl pyrrolidone)-co-(vinyl acetate)]s by reversed-phase gradient liquid chromatography.

    PubMed

    Cheng, Guanglou; Cullen, Jim; Wu, Chi-san

    2011-01-14

    Although size exclusion chromatography (SEC) has been used successfully to determine the molecular weight distribution (MWD) of statistical poly[(N-vinyl pyrrolidone)-co-(vinyl acetate)]s [PVPVAs], SEC cannot separate the copolymers according to their chemical composition. In this article, the separation of commercial PVPVAs with varying chemical compositions is reported, by aqueous reversed-phase gradient liquid chromatography (RPLC) using polystyrene-divinylbenzene-based wide pore columns. RPLC-SEC cross-fractionation indicates the presence of molar mass dependant effects during RPLC separation due to broad MWD for the copolymer studied; therefore the width of the RPLC peak could not be associated entirely with chemical composition distribution of the copolymer. Coupling of RPLC with online FTIR spectroscopy reveals the increase of VA content with increasing THF gradient, an indication of interaction mechanism between VA repeating units and the stationary phase for water soluble PVPVAs. Separation of water insoluble PVPVAs and PVAs by the RPLC are possibly based on both interaction and precipitation/redissolution mechanisms.

  16. Synthesis and Properties of pH-, Thermo-, and Salt-Sensitive Modified Poly(aspartic acid)/Poly(vinyl alcohol) IPN Hydrogel and Its Drug Controlled Release

    PubMed Central

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Zhao, Yansheng

    2015-01-01

    Modified poly(aspartic acid)/poly(vinyl alcohol) interpenetrating polymer network (KPAsp/PVA IPN) hydrogel for drug controlled release was synthesized by a simple one-step method in aqueous system using poly(aspartic acid) grafting 3-aminopropyltriethoxysilane (KH-550) and poly(vinyl alcohol) (PVA) as materials. The hydrogel surface morphology and composition were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The thermal stability was analyzed by thermogravimetric analysis (TGA). The swelling properties and pH, temperature, and salt sensitivities of KPAsp, KPAsp/PVA semi-interpenetrating polymer network (semi-IPN), and KPAsp/PVA IPN hydrogels were also investigated. All of the three hydrogels showed ampholytic pH-responsive properties, and swelling behavior was also extremely sensitive to the temperature, ionic strength, and cationic species. Finally, the drug controlled release properties of the three hydrogels were evaluated and results indicated that three hydrogels could control drug release by external surroundings stimuli. The drug controlled release properties of KPAsp/PVA IPN hydrogel are the most outstanding, and the correlative measured release profiles of salicylic acid at 37°C were 32.6 wt% at pH = 1.2 (simulated gastric fluid) and 62.5 wt% at pH = 7.4 (simulated intestinal fluid), respectively. These results indicated that KPAsp/PVA IPN hydrogels are a promising carrier system for controlled drug delivery. PMID:26351630

  17. Synthesis and Properties of pH-, Thermo-, and Salt-Sensitive Modified Poly(aspartic acid)/Poly(vinyl alcohol) IPN Hydrogel and Its Drug Controlled Release.

    PubMed

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Wang, Liping; Zhao, Yansheng

    2015-01-01

    Modified poly(aspartic acid)/poly(vinyl alcohol) interpenetrating polymer network (KPAsp/PVA IPN) hydrogel for drug controlled release was synthesized by a simple one-step method in aqueous system using poly(aspartic acid) grafting 3-aminopropyltriethoxysilane (KH-550) and poly(vinyl alcohol) (PVA) as materials. The hydrogel surface morphology and composition were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The thermal stability was analyzed by thermogravimetric analysis (TGA). The swelling properties and pH, temperature, and salt sensitivities of KPAsp, KPAsp/PVA semi-interpenetrating polymer network (semi-IPN), and KPAsp/PVA IPN hydrogels were also investigated. All of the three hydrogels showed ampholytic pH-responsive properties, and swelling behavior was also extremely sensitive to the temperature, ionic strength, and cationic species. Finally, the drug controlled release properties of the three hydrogels were evaluated and results indicated that three hydrogels could control drug release by external surroundings stimuli. The drug controlled release properties of KPAsp/PVA IPN hydrogel are the most outstanding, and the correlative measured release profiles of salicylic acid at 37°C were 32.6 wt% at pH = 1.2 (simulated gastric fluid) and 62.5 wt% at pH = 7.4 (simulated intestinal fluid), respectively. These results indicated that KPAsp/PVA IPN hydrogels are a promising carrier system for controlled drug delivery.

  18. A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous membrane for lithium-ion battery separator

    NASA Astrophysics Data System (ADS)

    Xia, Ming; Liu, Qiongzhen; Zhou, Zhou; Tao, Yifei; Li, MuFang; Liu, Ke; Wu, Zhihong; Wang, Dong

    2014-11-01

    A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous separator (referred to NFs/PET/NFs) composed of a poly(ethylene terephthalate) (PET) nonwoven sandwiched between two interconnected poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membranes is successfully developed for lithium-ion battery. Systematical investigations including structural characterization, porosity measurement, water contact angle testing, electrolyte uptake, and thermal shrinkage testing demonstrate that the notable feature of this NFs/PET/NFs nanofibrous separator is an electrolyte-philic, highly porous and hierarchically nanoscaled structure, thus resulting in superior electrolyte wettability, lower thermal shrinkage, and higher ion conductivity, in comparison to the commercial Polypropylene (PP) separator. These structural characteristics enable the NFs/PET/NFs separator to offer an excellent cell performance including outstanding C-rate capability, high capacity and excellent cycling performance. This suggests that the NFs/PET/NFs separator is a promising material for practical application in lithium-ion battery due to it low cost production and high performance.

  19. Effect of poly(vinyl acetate-acrylamide) microspheres properties and steric hindrance on the immobilization of Candida rugosa lipase.

    PubMed

    Zhang, Dong-Hao; Yuwen, Li-Xia; Li, Chao; Li, Ya-Qiong

    2012-11-01

    Poly(vinyl acetate-acrylamide) microspheres were synthesized in the absence or presence of isooctane via suspension polymerization and utilized as carriers to immobilize Candida rugosa lipase. When the hydrophobic/hydrophilic surface characteristics of the microspheres were modified by changing the ratio of vinyl acetate (hydrophobic monomer) to acrylamide (hydrophilic monomer) from 50:50 to 86:24, the immobilization ratio changed from 45% to 92% and the activity of the immobilized lipase increased from 202.5 to 598.0 U/g microsphere. Excessive lipase loading caused intermolecular steric hindrance, which resulted in a decline in lipase activity. The maximum specific activity of the immobilized lipase (4.65 U/mg lipase) was higher than that of free lipase (3.00 U/mg lipase), indicating a high activity recovery during immobilization.

  20. Effect of cellulose whisker content on the properties of poly(ethylene-co-vinyl acetate)/cellulose composites.

    PubMed

    Elanthikkal, Silviya; Gopalakrishnapanicker, Unnikrishnan; Varghese, Soney; Guthrie, James T; Francis, Tania

    2013-06-20

    The reinforcing effect of cellulose whiskers, produced from banana waste fibres, has been investigated using poly(ethylene-co-vinyl acetate) [EVA]/cellulose whisker composites. Cellulose whiskers, approximately 300 nm long and 30 nm wide, were obtained via a sulphuric acid hydrolysis method. The effects of the cellulose whisker loading on the thermal properties, mechanical properties and on the morphological features of the composites have been investigated. EVA copolymer with a vinyl acetate segment content of 40% has been used for composite fabrication. The developed composites showed superior thermal and mechanical properties relative to that of the EVA copolymer alone. Three theoretical models, namely the Halpin-Tsai model, the Kerner model and the Nicolais-Narkis model have been employed to provide a basis for the comparison of the results with the observations from the tensile investigations.

  1. Plasticizer-level study of poly(vinyl chloride) ion-selective membranes.

    PubMed

    Simon, M A; Kusy, R P

    1996-03-01

    Highly plasticized poly(vinyl chloride) (PVC) membranes (200 per hundred resin [phr]) form the basis of one class of ion-selective electrodes (ISEs). In previous work on the mechanical properties of membranes, the optimal ratio of plasticizer level employed to minimal level required for complete plasticization (phr(exp)/phrmin) was found to be 2.0. The current study was designed to determine whether this ratio is necessary or sufficient for proper ISE function. Dynamic mechanical analysis (DMA) was used to examine the effects of five plasticizers on the dynamic mechanical properties of membranes at three frequencies (110, 11.0, and 1.1 Hz) as a function of temperature (-100 degrees C to +100 degrees C); dioctyl sebacate (DOS), epoxidized propylene glycol dioleate (PGDO), ortho-nitrophenyl octyl ether (o-NPOE), epoxidized soybean oil (ESO), and epoxidized linseed oil (ELO). The glass transition temperature of PVC, which was found to be +77.1 degrees C at 11.0 Hz, was depressed by the addition of 200 phr of each plasticizer from a high of -1.4 degrees C (PGDO at 110 Hz) to a low of -70.2 degrees C (DOS at 1.1 Hz). DMA and electromotive-force (EMF) measurements on membranes plasticized with o-NPOE through a range of phr(exp)/phrmin from 0.5 to 9.3 indicated that a "transition window" occurs between phr(exp)/phrmin of 2.0 and 3.3 in which the membranes change from minimally plasticized polymer films to predictable ion-selective membranes, coinciding with the optimal mechanical properties observed previously. Based on dynamic mechanical properties and EMF response data, the optimal phr(exp)/phrmin++ ratios for membranes as a function of plasticizer were proposed: 0.8 for ESO and ELO, 1.3 for PGDO, 1.7 for DOS, and 3.0 for o-NPOE.

  2. High mechanical performance of layered graphene oxide/poly(vinyl alcohol) nanocomposite films.

    PubMed

    Liu, Luqi; Gao, Yun; Liu, Qing; Kuang, Jun; Zhou, Ding; Ju, Siting; Han, Baohang; Zhang, Zhong

    2013-07-22

    The design and fabrication of strong, lightweight, and damage-resistant composite materials are major topics of studies on composites. Biomimetics, a developing multidisciplinary field, is now leading the fabrication of novel materials with remarkable mechanical properties. Graphene oxide (GO), a graphene derivative, possesses good mechanical properties, a high aspect ratio, and good solubility in aqueous solutions, indicating great potential in nanocomposite fields. In this work, bioinspired layered GO/poly(vinyl alcohol) (PVA) nanocomposite films with remarkable mechanical performances are prepared by an environmental friendly, bottom-up assembly methodology. The structural analysis shows alternate piles of inorganic GO platelets and organic PVA binder. Tensile tests indicate that the borate-treated GO/PVA nanocomposite films display 360 MPa of strength, which is twofold to threefold higher than that of biological materials (e.g., nacre). Toughness of GO/PVA nanocomposites is also enhanced fourfold compared with nacre. To reveal the toughening function of the intercalated polymer in the nanocomposites, the influence of polymer with varied molecular weights (Mws) on the fracture mode of the nanocomposites is systematically investigated through quasi-static tensile and creep tests. The PVA molecules with a higher Mw can connect more neighboring GO platelets through inter- and intra-linkages than those with a lower Mw, resulting in efficient stress transfer along the GO plane direction. Thus, tensile strength and toughness are improved. This work illustrates the functions of bonding types between inorganic-organic phases and intercalated polymers with different Mws on the mechanical properties of the layered nanocomposites, including stiffness, strength, and toughness.

  3. Unconfined compression properties of a porous poly(vinyl alcohol)-chitosan-based hydrogel after hydration.

    PubMed

    Lee, Si-Yuen; Pereira, Barry P; Yusof, N; Selvaratnam, L; Yu, Zou; Abbas, A A; Kamarul, T

    2009-07-01

    A poly(vinyl alcohol) (PVA) hydrogel composite scaffold containing N,O-carboxymethylated chitosan (NOCC) was tested to assess its potential as a scaffold for cartilage tissue engineering in a weight-bearing environment. The mechanical properties under unconfined compression for different hydration periods were investigated. The effect of supplementing PVA with NOCC (20wt.% PVA:5vol.% NOCC) produced a porosity of 43.3% and this was compared against a non-porous PVA hydrogel (20g PVA: 100ml of water, control). Under non-hydrated conditions, the porous PVA-NOCC hydrogel behaved in a similar way to the control non-porous PVA hydrogel, with similar non-linear stress-strain response under unconfined compression (0-30% strain). After 7days' hydration, the porous hydrogel demonstrated a reduced stiffness (0.002kPa, at 25% strain), resulting in a more linear stiffness relationship over a range of 0-30% strain. Poisson's ratio for the hydrated non-porous and porous hydrogels ranged between 0.73 and 1.18, and 0.76 and 1.33, respectively, suggesting a greater fluid flow when loaded. The stress relaxation function for the porous hydrogel was affected by the hydration period (from 0 to 600s); however the percentage stress relaxation regained by about 95%, after 1200s for all hydration periods assessed. No significant differences were found between the different hydration periods between the porous hydrogels and control. The calculated aggregate modulus, H(A), for the porous hydrogel reduced drastically from 10.99kPa in its non-hydrated state to about 0.001kPa after 7days' hydration, with the calculated shear modulus reducing from 30.92 to 0.14kPa, respectively. The porous PVA-NOCC hydrogel conformed to a biphasic, viscoelastic model, which has the desired properties required for any scaffold in cartilage tissue engineering.

  4. Composite Scaffold of Poly(Vinyl Alcohol) and Interfacial Polyelectrolyte Complexation Fibers for Controlled Biomolecule Delivery

    PubMed Central

    Cutiongco, Marie Francene A.; Choo, Royden K. T.; Shen, Nathaniel J. X.; Chua, Bryan M. X.; Sju, Ervi; Choo, Amanda W. L.; Le Visage, Catherine; Yim, Evelyn K. F.

    2015-01-01

    Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC) fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor, and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol) hydrogel (PVA). Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight. Next, IPC fibers were incorporated in between layers of PVA to produce PVA–IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA–IPC composite grafts exhibited dependence on molecular weight, with lysozyme showing near-linear release for 1 month. Angiogenic factors were also incorporated into the PVA–IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA–IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release, and bioinertness, PVA–IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft tissue

  5. Submillimeter Diameter Poly(Vinyl Alcohol) Vascular Graft Patency in Rabbit Model

    PubMed Central

    Cutiongco, Marie F. A.; Kukumberg, Marek; Peneyra, Jonnathan L.; Yeo, Matthew S.; Yao, Jia Y.; Rufaihah, Abdul Jalil; Le Visage, Catherine; Ho, Jackie Pei; Yim, Evelyn K. F.

    2016-01-01

    Microvascular surgery is becoming a prevalent surgical practice. Replantation, hand reconstruction, orthopedic, and free tissue transfer procedures all rely on microvascular surgery for the repair of venous and arterial defects at the millimeter and submillimeter levels. Often, a vascular graft is required for the procedure as a means to bridge the gap between native arteries. While autologous vessels are desired for their bioactivity and non-thrombogenicity, the tedious harvest process, lack of availability, and caliber or mechanical mismatch contribute to graft failure. Thus, there is a need for an off-the-shelf artificial vascular graft that has low thrombogenic properties and mechanical properties matching those of submillimeter vessels. Poly(vinyl alcohol) hydrogel (PVA) has excellent prospects as a vascular graft due to its bioinertness, low thrombogenicity, high water content, and tunable mechanical properties. Here, we fabricated PVA grafts with submillimeter diameter and mechanical properties that closely approximated those of the rabbit femoral artery. In vitro platelet adhesion and microparticle release assay verified the low thrombogenicity of PVA. A stringent proof-of-concept in vivo test was performed by implanting PVA grafts in rabbit femoral artery with multilevel arterial occlusion. Laser Doppler measurements indicated the improved perfusion of the distal limb after implantation with PVA grafts. Moreover, ultrasound Doppler and angiography verified that the submillimeter diameter PVA vascular grafts remained patent for 2 weeks without the aid of anticoagulant or antithrombotics. Endothelial cells were observed in the luminal surface of one patent PVA graft. The advantageous non-thrombogenic and tunable mechanical properties of PVA that are retained even in the submillimeter diameter dimensions support the application of this biomaterial for vascular replacement in microvascular surgery. PMID:27376059

  6. Thermochemical reaction mechanism of lead oxide with poly(vinyl chloride) in waste thermal treatment.

    PubMed

    Wang, Si-Jia; Zhang, Hua; Shao, Li-Ming; Liu, Shu-Meng; He, Pin-Jing

    2014-12-01

    Poly(vinyl chloride) (PVC) as a widely used plastic that can promote the volatilization of heavy metals during the thermal treatment of solid waste, thus leading to environmental problems of heavy metal contamination. In this study, thermogravimetric analysis (TGA) coupled with differential scanning calorimeter, TGA coupled with Fourier transform infrared spectroscopy and lab-scale tube furnace experiments were carried out with standard PVC and PbO to explicate the thermochemical reaction mechanism of PVC with semi-volatile lead. The results showed that PVC lost weight from 225 to 230°C under both air and nitrogen with an endothermic peak, and HCl and benzene release were also detected. When PbO was present, HCl that decomposed from PVC instantly reacted with PbO via an exothermal gas-solid reaction. The product was solid-state PbCl2 at <501°C, which was the most volatile lead-containing compound with a low melting point and high vapor pressure. At >501°C, PbCl2 melted, volatilized and transferred into flue gas or condensed into fly ash. Almost all PbCl2 volatilized above 900°C, while PbO just started to volatilize slowly at this temperature. Therefore, the chlorination effect of PVC on lead was apt to lower-temperature and rapid. Without oxygen, Pb2O was generated due to the deoxidizing by carbon, with oxygen, the amount of residual Pb in the bottom ash was significantly decreased.

  7. Inhibition of nucleation and growth of ice by poly(vinyl alcohol) in vitrification solution.

    PubMed

    Wang, Hai-Yan; Inada, Takaaki; Funakoshi, Kunio; Lu, Shu-Shen

    2009-08-01

    Control of ice formation is crucial in cryopreservation of biological substances. Successful vitrification using several additives that inhibit ice nucleation in vitrification solutions has previously been reported. Among these additives, here we focused on a synthetic polymer, poly(vinyl alcohol) (PVA), and investigated the effects of PVA on nucleation and growth of ice in 35% (w/w) aqueous 1,2-propanediol solution by using a differential scanning calorimetry (DSC) system equipped with a cryomicroscope. First, the freezing temperature of the solution was measured using the DSC system, and then the change in ice fraction in the solution during cooling was evaluated based on images obtained using the cryomicroscope, at different concentrations of PVA between 0% and 3% (w/w). Based on the ice fraction, the change in residual solution concentration during cooling was also evaluated and then plotted on the state diagram of aqueous 1,2-propanediol solution. Results indicated that, when the partially glassy and partially frozen state was intentionally allowed, the addition of PVA effectively inhibited not only ice nucleation but also ice growth in the vitrification solution. The effect of PVA on ice growth in the vitrification solution was explained based on kinetic limitations mainly due to mass transport. The interfacial kinetics also might limit ice growth in the vitrification solution only when the ice growth rate decreased below a critical value. This coincides with the fact that PVA exhibits a unique antifreeze activity in the same manner as antifreeze proteins when ice growth rate is lower than a critical value.

  8. Solute retention and the states of water in polyethylene glycol and poly(vinyl alcohol) gels.

    PubMed

    Baba, Takayuki; Sakamoto, Ryosaku; Shibukawa, Masami; Oguma, Koichi

    2004-06-18

    The states of water sorbed in a cross-linked polyethylene glycol (PEG) gel, TSKgel Ether-250, and cross-linked poly(vinyl alcohol) (PVA) gels of different pore sizes, TSKgel Toyopearl HW-40S, 50S, 55S and 75S, were investigated by means of differential scanning calorimetry (DSC). It was found that there were three types of water in these hydrogels, non-freezing water, freezable bound water and free water. The amount of water that functions as the stationary phase in the column packed with the each gel was also estimated by a liquid chromatographic method. The estimated amount of the stationary phase water is in good agreement with the sum of the amount of non-freezing water and that of freezable bound water for HW-40S, 50S and 55S, while it agrees with the amount of only non-freezing water for HW-75S and Ether-250. This means that the stationary phase water consists of non-freezing water and freezable bound water for HW-40S, 50S and 55S, while only non-freezing water functions as the stationary phase in HW-75S and Ether-250 gels. This result can be attributed to the difference in the structure of the gels; the PVA gels containing PVA at relatively high concentrations, HW-40S, 50S and 55S, have a homogeneous gel phase, whereas HW-75S and Ether-250 have a heterogeneous gel phase consisting hydrated polymer domains and macropores with relatively hydrophobic surface. The freezable bound water in Toyopearl HW-40S, 50S and 55S can be regarded as a component of a homogeneous PVA solution phase, while that in HW-75S and Ether-250 may be water isolated in small pores of the hydrophobic domains. The results obtained by the investigation on the retention selectivity of these hydrogels in aqueous solutions supported our postulated view on the structures of the hydrogels.

  9. Thermal characteristics of poly(ethylene vinyl acetate) from 80 to 300 K

    NASA Astrophysics Data System (ADS)

    Pattanayak, S.; Bhowmick, T.

    This paper presents experimental results on thermal conductivity from 60 to 300 K and heat capacity from 80 to 300 K for poly(ethylene vinyl acetate) (EVA) having a crystallinity of 42%. Thermal conductivity increases with temperature. A deviation is observed in the region 170-210 K, where it shows a plateau. The variation of thermal conductivity (K) before and after the plateau is expressed by two empirical equations: K = ATm from 60 to 170 K and K = BTn from 210 to 300 K, where A = 9.437 × 10 -10W cm-1K-(m + 1), B = 1.082 × 10 -10W cm -1 K -(n + 1), m = 3.115 and n = 0.50, determined from experimental values. There is a considerable difference in the rates of change of thermal conductivity in the two regions. Below 100 K the change is almost negligible. The heat capacity also increases with temperature and from 170 to 210 K it shoots up and drops down again to match the nonlinear variation of thermal conductivity. A maximum is observed at 195 K, indicating a transition temperature. The change of heat capacity of EVA is well represented by the empirical equation C = DTP where D = 0.0575 J g -1 K -( p + 1) and p = 0.73. The change of C/T3 is 0.023 J g -1 K -4 between 80 and 170 K and 0.00187 J g -1 K -4 between 210 and 300 K. This variation is found to follow the Debye rule when the temperature is > 270 K. The measured heat capacity and thermal conductivity of EVA are compared with those of polyethylene (PE) and polytetrafluoroethylene (PTFE).

  10. Poly(vinyl alcohol)-heparin biosynthetic microspheres produced by microfluidics and ultraviolet photopolymerisation

    PubMed Central

    Young, Cara; Rozario, Kester; Serra, Christophe; Poole-Warren, Laura; Martens, Penny

    2013-01-01

    Biosynthetic microspheres have the potential to address some of the limitations in cell microencapsulation; however, the generation of biosynthetic hydrogel microspheres has not been investigated or applied to cell encapsulation. Droplet microfluidics has the potential to produce more uniform microspheres under conditions compatible with cell encapsulation. Therefore, the aim of this study was to understand the effect of process parameters on biosynthetic microsphere formation, size, and morphology with a co-flow microfluidic method. Poly(vinyl alcohol) (PVA), a synthetic hydrogel and heparin, a glycosaminoglycan were chosen as the hydrogels for this study. A capillary-based microfluidic droplet generation device was used, and by varying the flow rates of both the polymer and oil phases, the viscosity of the continuous oil phase, and the interfacial surface tension, monodisperse spheres were produced from ∼200 to 800 μm. The size and morphology were unaffected by the addition of heparin. The modulus of spheres was 397 and 335 kPa for PVA and PVA/heparin, respectively, and this was not different from the bulk gel modulus (312 and 365 for PVA and PVA/heparin, respectively). Mammalian cells encapsulated in the spheres had over 90% viability after 24 h in both PVA and PVA/heparin microspheres. After 28 days, viability was still over 90% for PVA-heparin spheres and was significantly higher than in PVA only spheres. The use of biosynthetic hydrogels with microfluidic and UV polymerisation methods offers an improved approach to long-term cell encapsulation. PMID:24404042

  11. Soy proteins as environmentally friendly sizing agents to replace poly(vinyl alcohol).

    PubMed

    Chen, Lihong; Reddy, Narendra; Yang, Yiqi

    2013-09-01

    An environmentally friendly and inexpensive substitute to the widely used poly(vinyl alcohol) (PVA) has been developed from soy proteins for textile warp sizing. Textile processing is the major source of industrial water pollution across the world, and sizing and desizing operations account for nearly 30 % of the water consumed in a textile plant. PVA is one of the most common sizing agents used for synthetic fibers and their blends due to PVA's easy water solubility and ability to provide desired sizing performance. However, PVA does not degrade and is a major contributor to pollution in textile effluent treatment plants. Although considerable efforts have been made to replace PVA with biodegradable sizing materials, the performance properties provided by PVA on synthetic fibers and their blends have been unmatched so far. Soy proteins are inexpensive, biodegradable, and have been widely studied for potential use in food packaging, as resins and adhesives. In this research, the potential of using soy proteins as textile sizing agents to replace PVA was studied. Polyester and polyester/cotton rovings, yarns, and fabrics sized with soy protein showed a considerably better improvement in strength and abrasion resistance compared to commercially available PVA-based size. Soy protein size had a 5-day biochemical oxygen demand /chemical oxygen demand ratio of 0.57 compared to 0.01 for PVA indicating that soy protein sizes were easily biodegradable in activated sludge. The total and ammonia nitrogen released from the proteins also did not adversely impact the biodegradability. Good sizing performance and easy biodegradability demonstrate that soy protein-based sizes have potential to replace PVA-based sizes leading to substantial benefits to the textile industry and the environment.

  12. Effect of moisture on electrospun nanofiber composites of poly(vinyl alcohol) and cellulose nanocrystals.

    PubMed

    Peresin, Maria S; Habibi, Youssef; Vesterinen, Arja-Helena; Rojas, Orlando J; Pawlak, Joel J; Seppälä, Jukka V

    2010-09-13

    The effect of humidity on the morphological and thermomechanical properties of electrospun poly(vinyl alcohol) (PVA) fiber mats reinforced with cellulose nanocrystals (CNs) was investigated. Scanning electron microscopy (SEM) images revealed that the incorporation of CNs improved the morphological stability of the composite fibers even in high humidity environments. Thermal and mechanical properties of the electrospun fiber mats were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and large deformation tensile tests under controlled humidity and temperatures. The balance between the moisture-induced plasticization and the reinforcing effect of rigid CN particles was critical in determining the thermomechanical behaviors of the electrospun fiber mats. Results indicated that the stabilizing effect of the CNs in the PVA matrix might be compromised by water absorption, disrupting the hydrogen bonding within the structure. The amount of this disruption depended on the surrounding humidity and the CN loading. The reduction in tensile strength of neat PVA fiber mats as they were conditioned from low relative humidity (10% RH) to high relative humidity (70% RH) was found to be about 80%, from 1.5 to 0.4 MPa. When the structure was reinforced with CNs, the reduction in strength was limited to 40%, from 2 to 0.8 MPa over the same range in relative humidity. More importantly, the CN-loaded PVA fiber mats showed a reversible recovery in mechanical strength after cycling the relative humidity. Finally, humidity treatments of the composite PVA fiber mats induced significant enhancement of their strength as a result of the adhesion between the continuous matrix and the CNs.

  13. Grafting poly(vinyl alcohol) onto polybutadiene rubber latex particles by pre-irradiation

    NASA Astrophysics Data System (ADS)

    Tian, Bo; Dong, Wei; Liu, Yuguang

    2017-06-01

    Poly(vinyl alcohol) (PVA) was grafted on polybutadiene rubber latex (PBL) particles (PB-g-PVA) by pre-irradiation via emulsion grafting copolymerization. The grafting degree (G%) increased almost linearly with the reaction time and the weight ratio of PVA to the PB latex, while decreased gradually when the irradiation dose is over 30 kGy and the reaction temperature is higher than 60 °C. The grafting efficiency (GE%) has the same trend of the G% but the weight ratio of PVA to PBL, GE% decreased with increasing of PVA adding to PB latex. FTIR spectroscopy indicated that the PVA was grafted onto the PB particles. The dynamic light scattering measurement showed that the particle size of PB-g-PVA particles was larger than that of the pristine PBL particles, and it increased with increment of G%. Transmission electron microscopy images of the PB-g-PVA latex particles demonstrated that the size of PB-g-PVA particle was enlarged by the layer of grafted PVA surrounding the PBL particles. Thermal behavior exhibited the phase separation in the PB-g-PVA films, Tg1 and Tg2 related to the PB and PVA respectively, both of which shifted to a higher temperature with increasing of G%, but the Tg2 was still lower than that of the virgin PVA. The increment of the surface free energy of PB-g-PVA films was attributed to the incorporation of the polar PVA, which also resulted in improvement of the hydrophilic properties.

  14. Dressing liposomal particles with chitosan and poly(vinylic alcohol) for oral vaccine delivery.

    PubMed

    Rescia, Vanessa C; Takata, Célia S; de Araujo, Pedro S; Bueno da Costa, Maria H

    2011-03-01

    Liposomes have been used as adjuvants since 1974. One major limitation for the use of liposomes in oral vaccines is the lipid structure instability caused by enzyme activities. Our aim was to combine liposomes that could encapsulate antigens (i.e., Dtxd, diphtheria toxoid) with chitosan, which protects the particles and promotes mucoadhesibility. We employed physical techniques to understand the process by which liposomes (SPC: Cho, 3:1) can be sandwiched with chitosan (Chi) and stabilized by PVA (poly-vinylic alcohol), which are biodegradable, biocompatible polymers. Round, smooth-surfaced particles of REVs-Chi (reversed-phase vesicles sandwiched by Chi) stabilized by PVA were obtained. The REVs encapsulation efficiencies (Dtxd was used as the antigen) were directly dependent on the Chi and PVA present in the formulation. Chi adsorption on the REVs surface was accompanied by an increase of ζ-potential. In contrast, PVA adsorption on the REVs-Chi surface was accompanied by a decrease of ζ-potential. The presence of Dtxd increased the Chi surface-adsorption efficiency. The PVA affinity by mucine was 2,000 times higher than that observed with Chi alone and did not depend on the molecule being in solution or adsorbed on the liposomal surface. The liberation of encapsulated Dtxd was retarded by encapsulation within REVs-Chi-PVA. These results lead us to conclude that these new, stabilized particles were able to be adsorbed by intestinal surfaces, resisted degradation, and controlled antigen release. Therefore, REVs-Chi-PVA particles can be used as an oral delivery adjuvant.

  15. Biosensors based on porous cellulose nanocrystal-poly(vinyl alcohol) scaffolds.

    PubMed

    Schyrr, Bastien; Pasche, Stéphanie; Voirin, Guy; Weder, Christoph; Simon, Yoan C; Foster, E Johan

    2014-08-13

    Cellulose nanocrystals (CNCs), which offer a high aspect ratio, large specific surface area, and large number of reactive surface groups, are well suited for the facile immobilization of high density biological probes. We here report functional high surface area scaffolds based on cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA) and demonstrate that this platform is useful for fluorescence-based sensing schemes. Porous CNC/PVA nanocomposite films with a thickness of 25-70 nm were deposited on glass substrates by dip-coating with an aqueous mixture of the CNCs and PVA, and the porous nanostructure was fixated by heat treatment. In a subsequent step, a portion of the scaffold's hydroxyl surface groups was reacted with 2-(acryloxy)ethyl (3-isocyanato-4-methylphenyl)carbamate to permit the immobilization of thiolated fluorescein-substituted lysine, which was used as a first sensing motif, via nucleophile-based thiol-ene Michael addition. The resulting sensor films exhibit a nearly instantaneous and pronounced change of their fluorescence emission intensity in response to changes in pH. The approach was further extended to the detection of protease activity by immobilizing a Förster-type resonance energy transfer chromophore pair via a labile peptide sequence to the scaffold. This sensing scheme is based on the degradation of the protein linker in the presence of appropriate enzymes, which separate the chromophores and causes a turn-on of the originally quenched fluorescence. Using a standard benchtop spectrometer to monitor the increase in fluorescence intensity, trypsin was detected at a concentration of 250 μg/mL, i.e., in a concentration that is typical for abnormal proteolytic activity in wound fluids.

  16. Composite scaffold of poly(vinyl alcohol) and interfacial polyelectrolyte complexation fibers for controlled biomolecule delivery.

    PubMed

    Cutiongco, Marie Francene A; Choo, Royden K T; Shen, Nathaniel J X; Chua, Bryan M X; Sju, Ervi; Choo, Amanda W L; Le Visage, Catherine; Yim, Evelyn K F

    2015-01-01

    Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC) fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor, and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol) hydrogel (PVA). Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight. Next, IPC fibers were incorporated in between layers of PVA to produce PVA-IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA-IPC composite grafts exhibited dependence on molecular weight, with lysozyme showing near-linear release for 1 month. Angiogenic factors were also incorporated into the PVA-IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA-IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release, and bioinertness, PVA-IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft tissue engineering.

  17. Glass transition and dynamics of poly(vinyl pyrrolidone)-water mixture

    NASA Astrophysics Data System (ADS)

    Miyara, M.; Sakuramatsu, Y.; Sasaki, K.; Kita, R.; Shinyashiki, N.; Yagihara, S.

    2013-02-01

    Broadband dielectric measurements of poly(vinyl pyrrolidone) (PVP)-water mixture were performed in a frequency range of 10 mHz - 50 GHz and at temperatures between 118 K and 318 K. The relaxation processes caused by the reorientational motion of water molecules (h-process) and the local chain motion of PVP (m-process) were observed without crystallization of water. The relaxation time of the m-process, τm, obeys the Vogel-Fulcher law, and the glass transition temperature, Tg, of PVP in the mixture, at which τm being 100 s is 237 K. The relaxation time of the h-process, τh, obeys the Vogel-Fulcher law above Tg = 237 K, and it turns to obey the Arrhenius law below Tg. The relaxation strength of the m-process, Δɛm, increases with decreasing temperature. The relaxation strength of the h-process, Δɛh, increases with decreasing temperature above the crossover temperature, TC (TC = 272 K), and it turns to be almost constant below TC. The temperature dependences of τm and τh are the same as those of the α- and the ν-processes observed in various kinds of water mixtures. In contrast, the temperature dependence of Δɛh is different from that observed in various kinds of water mixtures. The characteristic property of Δɛh could be related to the highest Tg of neat PVP in those of the solutes of other water mixtures.

  18. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite

    PubMed Central

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments. PMID:25482413

  19. The reactive blending of a thermoplastic polyurethane in situ with poly(vinyl chloride)

    NASA Astrophysics Data System (ADS)

    Parnell, Shane Richard

    A novel reactive blending process was investigated to produce high performance poly(vinyl chloride)/thermoplastic polyurethane (PVC/TPU) blends of significant commercial utility. In this process, a high molecular weight TPU with poly(butylene adipate) (PBA) soft segments and 4,4 '-diphenylmethane diisocyanate/1,4-butanediol (MDI/BDO) hard segments was polymerized in situ with PVC. More specifically, the process was broken down into two fundamental stages: the compounding and plasticization of PVC with PBA and BDO, and, upon adding MDI, the subsequent polymerization of TPU in situ with PVC to produce a PVC/TPU blend. A powerful, versatile characterization tool, Raman spectroscopy was used to elucidate the presence of intermolecular interactions in both stages of the PVC/TPU reactive blending process and measure the kinetics of TPU polymerization in situ with PVC. Initially, model studies of the PVC/TPU reactive blending process were conducted on a batch internal mixer. In the first stage of the process, the TPU reactants PBA and BDO effectively functioned as plasticizers as they were completely miscible with PVC. In the second stage of the process, TPU polymerization in situ with PVC was accompanied by reaction induced PVC/TPU blend phase separation. Partially miscible, PVC/TPU blends were characterized by multi-phase morphologies at room temperature, with a broad distribution of phase sizes and compositions. In measuring their effect on reaction kinetics, both PVC and its tin mercaptide thermal stabilizer catalyzed TPU polymerization. In measuring some of their mechanical properties, PVC/TPU blends produced via reactive blending had comparable and even superior tensile properties to analogous PVC/TPU blends produced via melt blending. Using information gleaned from the former model studies, the PVC/TPU reactive blending process was also conducted on a continuous, counter-rotating, intermeshing, twin screw extruder. In these reactive extrusion studies (REX

  20. Anion exchange membrane prepared from simultaneous polymerization and quaternization of 4-vinyl pyridine for non-aqueous vanadium redox flow battery applications

    NASA Astrophysics Data System (ADS)

    Maurya, Sandip; Shin, Sung-Hee; Sung, Ki-Won; Moon, Seung-Hyeon

    2014-06-01

    A simple, single step and environmentally friendly process is developed for the synthesis of anion exchange membrane (AEM) by simultaneous polymerization and quaternization, unlike the conventional membrane synthesis which consists of separate polymerization and quaternization step. The membrane synthesis is carried out by dissolving polyvinyl chloride (PVC) in cyclohexanone along with 4-vinyl pyridine (4VP) and 1,4-dibromobutane (DBB) in the presence of thermal initiator benzoyl peroxide, followed by film casting to get thin and flexible AEMs. The membrane properties such as ion exchange capacity, ionic conductivity and swelling behaviour are tuned by varying the degree of crosslinking. These AEMs exhibit low vanadium permeability, while retaining good dimensional and chemical stability in an electrolyte solution, making them appropriate candidates for non-aqueous vanadium acetylacetonate redox flow battery (VRFB) applications. The optimized membrane displays ion exchange capacity and ionic conductivity of 2.0 mequiv g-1 and 0.105 mS cm-1, respectively, whereas the efficiency of 91.7%, 95.7% and 87.7% for coulombic, voltage and energy parameter in non-aqueous VRFB, respectively. This study reveals that the non-aqueous VRFB performance is greatly influenced by membrane properties; therefore the optimal control over the membrane properties is advantageous for the improved performance.

  1. Gamma-radiation-induced grafting of binary mixture of methacrylic acid and 4-vinyl pyridine onto Teflon-FEP film as an effective polar membrane for separation processes

    NASA Astrophysics Data System (ADS)

    Kaur, Inderjeet; Rattan, Sunita; Chauhan, Sandeep; Gupta, Nitika

    2010-05-01

    Ionic bifunctional membranes have been synthesized by grafting binary mixture of methacrylic acid (MAAc) and 4-vinyl pyridine (4-VP) onto Teflon-FEP film by pre-irradiation method. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of binary mixture (MAAc-co-4-VP) (71.29%) was obtained at an optimum total dose of 54.48 kGy and the total concentration was 9.49 mol/L ([4-VP] = 0.07 mol/L and [MAAc ] = 9.42 mol/L) in 5 ml of water. The effect of alcohols as additives to the reaction medium on percent grafting of the binary mixture has also been studied. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Swelling studies of the membranes were performed in different solvents such as water, benzene, carbon tetrachloride and dimethyl formamide (DMF). Maximum swelling was observed in DMF with minimum swelling in benzene. Metal ion (Cu 2+, Ni 2+ and Fe 2+) uptake studies show better affinity for Fe 2+ ions. Conductance measurements in different aqueous salt solution showed that these membranes have affinity for Na +/K + ions and Cl - ions and hence can be used in desalination/separation processes for the separation of both type of cationic and anionic ions.

  2. Mixed poly(vinyl pyrrolidone)-based drug-loaded nanomicelles shows enhanced efficacy against pancreatic cancer cell lines.

    PubMed

    Veeren, Anisha; Bhaw-Luximon, Archana; Mukhopadhyay, Debabrata; Jhurry, Dhanjay

    2017-03-18

    We report in this paper on the enhanced efficacy of a physical mixture of two single anti-cancer loaded nanomicelles against PANC-1 and BxPC-3. Poly(vinyl pyrrolidone-b-polycaprolactone) (PVP-b-PCL) and poly(vinyl pyrrolidone-b-poly(dioxanone-co-methyl dioxanone)) (PVP-b-P(DX-co-MeDX)) were synthesized and successfully loaded with various anti-cancer drugs - gemcitabine (GEM), doxorubicin.HCl (DOX.HCl), doxorubicin.NH2 (DOX), 5-fluorouracil (5-FU) and paclitaxel (PTX). Spherical micelles of size 160-477 nm were obtained as characterized by DLS while sizes determined by TEM were in the range 140-250 nm. The hydrophobic drugs had a higher loading percentage efficiency compared to hydrophilic drugs in the trend PTX>DOX>5-FU>GEM>DOX.HCl whereas the drug release pattern followed the reverse trend in accordance with decreased polymer-drug interaction as quantified by the binding constant and micellar drug location. Cellular uptake studies showed that nanomicelles are taken up by pancreatic cancer cells into the cytoplasm and nucleus. The free nanomicelles were confirmed to be non-cytotoxic. A physical mixture of GEM loaded micelles and DOX.HCl loaded micelles of comparable size showed significantly higher cytotoxicity than either the free drug mixture or the individual single drug loaded micelles as confirmed by their IC50 values.

  3. Characterisation and in vitro stability of low-dose, lidocaine-loaded poly(vinyl alcohol)-tetrahydroxyborate hydrogels.

    PubMed

    Abdelkader, D H; Osman, M A; El-Gizawy, S A; Faheem, A M; McCarron, P A

    2016-03-16

    Poly(vinyl alcohol) hydrogels cross-linked with the tetrahydroxyborate anion possess textural and rheological properties that can be used as novel drug-loaded vehicles for application to traumatic wounds. However, addition of soluble drug substances causes concentration-dependent phase separation and rheological changes. The aim of this work was to investigate the effect of adding a local anaesthetic, but keeping the concentration low in an attempt to prevent these changes. Cross-linked hydrogels prepared from three grades of poly(vinyl alcohol) were characterised rheologically. Temperature sweep studies showed an elevated complex viscosity upon moving from 25°C to 80°C, which remained high for 48 h following completion of the cycle. Adhesion to model dermal surfaces achieved a maximum of 2.62 N cm(-2) and were greater than that observed to epidermal substrates, with a strong dependence on the rate of detachment used during testing. An optimised formulation (6% w/w PVA (31-50; 99) and 2% w/w THB) containing lidocaine hydrochloride loaded to an upper maximum concentration of 1.5% w/w was assessed for phase separation and drug crystallisation. After six months, crystallisation was present in formulations containing 0.7% and 1.5% lidocaine HCl. Changes in pH in response to increases in lidocaine loading were low. Drug release was shown to operate via a non-Fickian process for all three concentrations, with 60% occurring after approximately 24h. It can be concluded that using a low concentration of lidocaine hydrochloride in hydrogels based on poly(vinyl alcohol) will result in crystallisation. Furthermore, these hydrogels are unlikely to induce rapid anaesthesia due to the low loading and slow release kinetics. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Surface modification of poly(vinyl chloride) by physisorbed free radical initiation for reduced plasticizer migration and antimicrobial properties

    NASA Astrophysics Data System (ADS)

    McGinty, Kathryn

    Poly(vinyl chloride), PVC, is a particularly important commodity polymer that accounts for an annual world-wide production of 26 million tons. It is used frequently in the medical field as blood storage bags, endotracheal and dialysis tubing and intravenous catheters. Common plasticizers, namely di(2-ethylhexyl) phthalate (DEHP), are added to PVC to improve the processability and flexibility by lowering the glass transition temperature. However, most phthalate plasticizers are potential carcinogens. There has been extensive research on PVC with surface coatings to improve biocompatibility, surface crosslinking to create a barrier to the plasticizer leaching and surface grafting of hydrophilic polymers for both biocompatibility and reduced plasticizer migration. A novel surface grafting technique is the grafting of hydrophilic monomers by physisorbed free radical initiators. This modification method can be applied to PVC to attach vinyl hydrophilic monomers by the "grafting from" method. This approach, extending on earlier work involving polymer brush formation on poly(dimethylsiloxane), involves a two-step process: physisorption of a hydrophobic free radical initiator onto a polymer surface followed by radical polymerization of hydrophilic monomers in water. The key step is creating a hydrophobic/hydrophilic diffusional barrier that promotes radical reactions at the polymer surface. Polymers that have been successfully grafted from PVC films and tubing include: poly(hydroxyethyl methacrylate) (PHEMA), poly(dimethylacrylamide) (PDMA), poly(hydroxyethyl acrylate) (PHEA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly(acrylic acid) (PAA), and poly(4-vinylpyridine) (P4VP). Characterization methods performed include bulk chemical composition by transmission infrared spectroscopy, surface composition using X-ray photoelectron spectroscopy, surface wettability by tensiometry and capillary rise, film thickness determination by infrared, gravimetric analysis and UV

  5. A Study of Cross-linked Regions of Poly(Vinyl Alcohol) Gels by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

    2011-07-01

    A poly(vinyl alcohol)-borax cross-linked hydrogel has been studied by Small Angle Neutron Scattering as a function of borax concentration in the wave-vector transfer (Q) range of 0.017 Å-1 to 0.36 Å-1. It is found that as the concentration of borax increases, so does the intensity of scattering in this range. Beyond a borax concentration of 2 mg/ml, the increase in cross-linked PVA chains leads to cross-linked units larger than 150 Å as evidenced by a reduction in intensity in the lower Q region.

  6. Poly(vinyl chloride) membrane cesium ion-selective electrodes based on lipophilic calix[6]arene tetraester derivatives.

    PubMed

    Oh, H; Choi, E M; Jeong, H; Nam, K C; Jeon, S

    2000-12-04

    New lipophilic tetraesters of calix[6]arene and calix[6]diquinone are investigated as cesium ion-selective ionophores in poly(vinyl chloride) membrane electrodes. For an ion-selective electrode based on calix[6]arene tetraester I, the linear response is 1x10(-6)-1x10(-1) M of Cs(+) concentrations. The selectivity coefficients for cesium ion over alkali, alkaline earth and ammonium ions are determined. The detection limit (log a (Cs (+))=-6.31) and the selectivity coefficient (log k (Cs (+),Rb (+))(pot )=-1.88) are obtained for polymeric membrane electrode containing calix[6]arene tetraester I.

  7. Neutron Scattering and Dielectric Study on the Structural and Dynamical Peculiar Properties of Poly(vinyl chloride)

    SciTech Connect

    Arbe, A.; Farago, B.; Frick, B.

    2004-04-30

    In this work we have studied the anomalous dynamical behavior of poly(vinyl chloride) (PVC) searching its origin in the dynamical heterogeneities arising from the structural peculiarities of this polymer. For this purpose we have combined dielectric spectroscopy, coherent and incoherent neutron scattering for the dynamics investigation, and SANS for resolving the heterogeneous structure of PVC. The SANS experiments indicate the existence of structural modulations that persist in the temperature range T < 430 K. We show that a distribution of glass transition temperatures due to these density modulations causes the broadening of the response from the structural relaxation and the anomalous momentum transfer dependence of the incoherent scattering function.

  8. Effects of Saponification Rate on Electrooptical Properties and Morphology of Poly(vinyl alcohol)/Liquid Crystal Composite Films

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Kawatsuki, Nobuhiro

    1995-03-01

    The relationship between the saponification rate of poly(vinyl alcohol) (PVA), and the electrooptical properties and morphology of the PVA/liquid crystal (LC) composite films was investigated. Light transmission clazing and the LC droplet size were varied by changing the saponification rate or the blend ratio of two kinds of PVA with different saponification rates because the refractive index and surface tension could be controlled by the saponification rate of PVA. The threshold voltage decreased with increasing saponification rate though the extrapolation length was decreased. It was suggested that the electrooptical properties were strongly dependent on the droplet size.

  9. Studies on thermal analysis and optical parameters of Cu doped poly(vinyl acetate)/polyindole composites

    NASA Astrophysics Data System (ADS)

    Bhagat, D. J.; Dhokane, G. R.

    2015-05-01

    This article reports investigation on optical parameters and thermal analysis of Cu doped poly(vinyl acetate)/polyindole composites using cupric chloride as an oxidant. The study's complex optical parameters were determined through ultraviolet-visible (UV-vis) spectroscopy. Thermal analysis was done through thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The optical band gap values were found in the range 3.4381-4.8646 eV that reflects that synthesized composites have the potential to have application in optical devices and solar cells. The optical conductivity of composites is calculated to be 1.608 × 107 S-1.

  10. Neutron Scattering and Dielectric Study on the Structural and Dynamical Peculiar Properties of Poly(vinyl chloride)

    NASA Astrophysics Data System (ADS)

    Arbe, A.; Moral, A.; Alegría, A.; Colmenero, J.; Pyckhout-Hintzen, W.; Richter, D.; Farago, B.; Frick, B.

    2004-04-01

    In this work we have studied the anomalous dynamical behavior of poly(vinyl chloride) (PVC) searching its origin in the dynamical heterogeneities arising from the structural peculiarities of this polymer. For this purpose we have combined dielectric spectroscopy, coherent and incoherent neutron scattering for the dynamics investigation, and SANS for resolving the heterogeneous structure of PVC. The SANS experiments indicate the existence of structural modulations that persist in the temperature range T < 430 K. We show that a distribution of glass transition temperatures due to these density modulations causes the broadening of the response from the structural relaxation and the anomalous momentum transfer dependence of the incoherent scattering function.

  11. Poly(vinyl chloride) tubing with covalently bound alkaline phosphatase and alternative approach for investigations of open-tubular bioreactors.

    PubMed

    Rozum, Beata; Gajownik, Kamil; Tymecki, Lukasz; Koncki, Robert

    2010-05-01

    A one-step carbodiimide method was found to allow covalent binding of enzymes to the inner wall of poly(vinyl chloride) (PVC) tubing. The immobilization is performed under mild conditions without laborious pretreatment or activation of reactor surface. In these preliminary studies, alkaline phosphatase (ALP, EC 3.1.3.1) and p-nitrophenyl phosphate (NPP) were applied as a model enzyme and substrate, respectively. The resulting open-tubular bioreactor exhibits satisfactory operational and storage stability. In addition, a novel and very simple instrumental concept for optical monitoring of the biocatalytic process directly inside the microbioreactor using a system of paired emitter-detector diodes is presented.

  12. Nano-free volume characterization by positron annihilation lifetime technique in flame-retardant poly (vinyl chloride) after thermal treatment

    NASA Astrophysics Data System (ADS)

    Mohsen, M.; Mostafa, N.; Rashad, S. M.; Ayoub, A.; Salem, E. F.

    2007-02-01

    The flammability tests are performed on flame-retardant poly (vinyl chloride) (FRPVC) material that has been used in cable insulation and jacketing construction for multi-purpose reactor (MPR) at Atomic Energy Authority of Egypt, as well as carbon-black FRPVC (CB-FRPVC) material produced by Egyptian Electrical Cable Company (EECC). The temperature variation of thermal conductivity, thermal expansion coefficients, and nano-size free volumes by means of positron annihilation lifetime (PAL) technique are determined. Correlation of positron annihilation and thermal conductivity has been discussed in terms of phonons as the main heat carriers.

  13. Removal of some textile dyes from aqueous solutions by poly( N-vinyl-2-pyrrolidone) and poly( N-vinyl-2-pyrrolidone)/K 2S 2O 8 hydrogels

    NASA Astrophysics Data System (ADS)

    Can, Hatice Kaplan; Kirci, Betül; Kavlak, Serap; Güner, Ali

    2003-12-01

    Poly( N-vinyl-2-pyrrolidone)/water and poly( N-vinyl-2-pyrrolidone)/K 2S 2O 8/water systems are hydrogels prepared by irradiation with γ-rays at ambient temperature. Both hydrogel systems were employed for diffusion and swelling experiments in various textile dyes aqueous solutions (textile dyes such as Cibacron Blue (CB) F3GA, Methyl Orange (MO), Congo Red (CR)). For these hydrogel systems, swelling studies indicated that swelling percentages increased in the following order: MO>CB F3GA>CR at fixed dose 96 kGy. Because of this reason MO dye solution has been chosen and all swelling properties are investigated for 26, 64, 96 and 124 kGy. The swelling capabilities of PVP and PVP/K 2S 2O 8 hydrogels in MO dye solution vary in the range of 400-1500%. The diffusion of dye solutions PVP and PVP/K 2S 2O 8 hydrogels was assumed to be Fickian character. The swelling behavior of PVP and PVP/K 2S 2O 8 hydrogels exhibits second-order kinetic in all dye solutions. Diffusion coefficient, initial swelling rate, swelling rate constant, maximum swelling and equilibrium water/dye content were found for all gel systems in dye solutions.

  14. Hydration effects and antifouling properties of poly(vinyl chloride-co-PEGMA) membranes studied using molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Shaikh, Abdul Rajjak; Rajabzadeh, Saeid; Matsuo, Ryuichi; Takaba, Hiromitsu; Matsuyama, Hideto

    2016-04-01

    Polyvinyl chloride (PVC) membranes are widely used in water treatment because of their low cost and chemical stability. However, PVC membranes can become fouled, and this restricts their applications in membrane technology. In order to enhance the antifouling property of PVC membranes, copolymers such as poly(vinyl chloride-co-poly(ethylene glycol)methyl ether methacrylate) (poly(VC-co-PEGMA)) with different PEGMA segment percentages were synthesized in our previous work. Experimentally, it was observed that the poly(VC-co-PEGMA) copolymer has better antifouling properties than those of PVC membranes. Here, we explore effect of the PEGMA segment percentage on the surface hydration properties of poly(VC-co-PEGMA) copolymers. Density functional theory calculations and molecular dynamics simulations were carried out to understand the interactions between PVC and PEGMA. Model structures of these systems were validated by comparing the simulated values of their volumetric properties with the experimental values. MD studies showed that increasing PEGMA percentage in the copolymer increases the interaction with water molecules, leading to improved resistance to fouling. The antifouling mechanism is also discussed with respect to surface hydration and water dynamicity. This study could form a basis for the systematic studies of polymeric membranes as well as their stability from the extent of solvent-polymer, solvent-solvent, and polymer-polymer interactions.

  15. Correlation between Raman and fluorescence microscopy studies of field-aged commercial urethane-backed poly(vinyl chloride)

    NASA Astrophysics Data System (ADS)

    Remillard, J. T.; Weber, W. H.; Jones, J.; Helms, J.; Poindexter, B. D.

    1998-03-01

    Urethane-foam-backed poly(vinyl chloride) (PVC) composites are widely used in vehicle interiors. Exposure to heat and light causes vinyl to degrade through dehydrochlorination, a process which results in the formation of conjugated polyene sequences. This leads to the cracking and discoloration that commonly occurs with age in commercial PVC. We present the results of Raman and fluorescence microscopy measurements used to quantify the degradation of two commercial field-aged foam/PVC composites containing different heat stabilizer packages. Raman spectroscopy provides chemically-specific evidence of polyene formation, and clearly indicates differences in the durability of the two materials. After extracting the low molecular weight components from the vinyl, we find the variations in fluorescence intensity with weathering time are closely correlated with the variations in polyene concentration measured using Raman microscopy. This suggests fluorescence techniques can be used as a semiquantitative measure of PVC degradation. These measurements are most easily performed using a fluorescence microscope and CCD camera to record images of the samples. Intensities are quickly determined through the use of image processing software.

  16. Lung cancer risk in workers exposed to poly(vinyl chloride) dust: a nested case-referent study

    PubMed Central

    Mastrangelo, G; Fedeli, U; Fadda, E; Milan, G; Turato, A; Pavanello, S

    2003-01-01

    Background: There have been few investigations of an association between poly(vinyl chloride) (PVC) dust exposure and an increase in lung cancer incidence, and their conclusions have been inconsistent. Aims: To determine whether PVC and/or vinyl chloride monomer (VCM) is the associated risk factor(s), by means of a nested case-referent study, in order to estimate lung cancer risk, avoiding selection, information, or confounding biases. Methods: Thirty eight cases of histologically verified lung cancer and 224 control subjects without a history of cancer were selected from an Italian cohort of 1658 vinyl chloride workers. Information sources included clinical records (diagnosis, smoking habits) and plant records (occupational history). The risk of lung cancer was estimated by odds ratios (OR) with 95% confidence intervals (CI), calculated using logistic regression models. Results: In PVC baggers exposed to high levels of respirable PVC particles in the workplace, the lung cancer OR increases by 20% for each extra year of work (OR = 1.2003; 95% CI 1.0772 to 1.3469; p = 0.0010), when the influence of age and smoking habits is controlled. No relation was found between lung cancer and cumulative VCM exposure. Conclusion: This nested case-control study showed, in the VCM/PVC industry, an increased risk of lung cancer associated with exposure to PVC dust; previous cohort studies failed to recognise such excess, probably because they used VCM exposure as the risk indicator. PMID:12771394

  17. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    NASA Astrophysics Data System (ADS)

    Palani, P. Bahavan; Abidin, K. Sainul; Kannan, R.; Rajashabala, S.; Sivakumar, M.

    2016-05-01

    The highest proton conductivity value of 0.0802 Scm-1 is obtained at 6wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na+ MMT was modified (protonated) to H+ MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  18. Singly and binary grafted poly(vinyl chloride) urinary catheters that elute ciprofloxacin and prevent bacteria adhesion.

    PubMed

    Islas, Luisa; Alvarez-Lorenzo, Carmen; Magariños, Beatriz; Concheiro, Angel; del Castillo, Luis Felipe; Burillo, Guillermina

    2015-07-05

    Acrylic acid (AAc) and poly(ethylene glycol) methacrylate (PEGMA) were singly and dually grafted onto poly(vinyl chloride) (PVC) urinary catheters with the aim of preventing biofouling by endowing the catheters with the ability to load and release antimicrobial agents and to avoid bacteria adhesion. The polymers were grafted applying an oxidative pre-irradiation ((60)Co source) method in two steps. Grafting percentage and kinetics were evaluated by varying the absorbed pre-irradiation dose, reaction time, monomer concentration, and reaction temperature. Catheters with grafting percentages ranging from 8 to 207% were characterized regarding thermal stability, surface hydrophilicity, mechanical properties, swelling, and lubricity. The modified catheters proved to have better compatibility with fibroblast cells than PVC after long exposure times. Furthermore, grafted catheters were able to load ciprofloxacin and sustained its release in urine medium for several hours. Ciprofloxacin-loaded catheters inhibited the growth of Escherichia coli and Staphylococcus aureus in the catheter surroundings and prevented bacteria adhesion.

  19. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    SciTech Connect

    Palani, P. Bahavan Abidin, K. Sainul; Kannan, R.; Rajashabala, S.; Sivakumar, M.

    2016-05-23

    The highest proton conductivity value of 0.0802 Scm{sup −1} is obtained at 6 wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na{sup +} MMT was modified (protonated) to H{sup +} MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  20. Electrospinning of poly(vinyl alcohol) nanofibers loaded with hexadecane nanodroplets.

    PubMed

    Arecchi, A; Mannino, S; Weiss, J

    2010-08-01

    The feasibility of producing poly(vinyl alcohol) (PVA) nanofibers containing fine-disperse hexadecane droplets by electrospinning a blend of hexadecane-in-water emulsions and PVA was investigated. Hexadecane oil-in-water nanoemulsions (d(10)= 181.2 +/- 0.1 nm) were mixed with PVA at pH 4.5 to yield polymer-emulsion blends containing 0.5 to 1.5 wt% oil droplets and 8-wt% PVA. The solution properties of emulsions and emulsion-PVA blends (viscosity, conductivity, surface tension) were determined. Solutions were electrospun and the morphology and thermal properties of deposited fiber mats characterized by scanning electron microscopy and differential scanning calorimetry. Fiber mats were dissolved in buffer to liberate incorporated hexadecane droplets and the buffer solutions analyzed by optical microscopy, UV-spectroscopy, and light scattering. Analysis of dry fiber mats and their solutions showed that emulsion droplets were indeed part of the electrospun fiber structures. Depending on the concentration of hexadecane in the initial emulsion-polymer blends, droplets were dispersed in the fibers as individual droplets or in form of aggregated flocs of hexadecane droplets. Nanofibers with spindle-like perturbations or nanofibers containing bead-like structures with approximately 5 times larger than the size of droplets in the original nanoemulsion were obtained. Remarkably, incorporation of hexadecane droplets in fibers did not alter size of individual droplets, that is, no coalescence occurred. The manufacture of solid matrix containing nanodroplets could be of substantial interest for manufacturers wishing to develop encapsulation system for lipophilic functional compounds such as lipid-soluble flavors, antimicrobials, antioxidants, and bioactives with tailored release kinetics. Practical Applications: The paper describes the formation of electrospun nanofibers from hydrophilic polymers that contain fine-disperse emulsion droplets. By incorporating emulsion droplets, a

  1. 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

  2. Phosphonium-based ionic liquids as modifiers for biomedical grade poly(vinyl chloride).

    PubMed

    Dias, Ana M A; Marceneiro, Sofia; Braga, Mara E M; Coelho, Jorge F J; Ferreira, Abel G M; Simões, Pedro N; Veiga, Helena I M; Tomé, Liliana C; Marrucho, Isabel M; Esperança, José M S S; Matias, Ana A; Duarte, Catarina M M; Rebelo, Luís P N; de Sousa, Hermínio C

    2012-03-01

    This work reports and discusses the influence of four phosphonium-based ionic liquids (PhILs), namely trihexyl(tetradecyl) phosphonium dicyanamide, [P(6,6,6,14)][dca]; trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide, [P(6,6,6,14)][Tf(2)N]; tetrabutyl phosphonium bromide, [P(4,4,4,4)][Br]; and tetrabutyl phosphonium chloride, [P(4,4,4,4)][Cl], on some of the chemical, physical and biological properties of a biomedical-grade suspension of poly(vinyl chloride) (PVC). The main goal of this work was to evaluate the capacity of these PhILs to modify some of the properties of neat PVC, in particular those that may allow their use as potential alternatives to traditional phthalate-based plasticizers in PVC biomedical applications. PVC films having different PhIL compositions (0, 5, 10 and 20 wt.%) were prepared (by solvent film casting) and characterised by Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, dynamical mechanical thermal analysis, scanning electron microscopy/energy-dispersive X-ray/electron probe microanalysis, X-ray diffraction, transmittance, permeability towards oxygen and carbon dioxide, thermal degradation, contact angle measurement, water and vapour uptake, leachability and biocompatibility (haemolytic potential, thrombogenicity and cytotoxicity). A conventional organic plasticizer (di-isononyl phthalate) was used for comparison purposes. The results obtained showed that it was possible to change the neat PVC hydrophobicity, and consequently its water uptake capacity and plasticizer leachability, just by changing the PhIL employed and its composition. It was also possible to significantly change the thermal and mechanical properties of PVC films by choosing appropriate PhIL cation/anion combinations. However, a specific PhIL may not always be capable of simultaneously keeping and/or improving both physical properties. In addition, ionic halide salts were found to promote PVC

  3. Nonlinear optical properties of ZnO/poly (vinyl alcohol) nanocomposite films

    SciTech Connect

    Jeeju, P. P.; Jayalekshmi, S.; Chandrasekharan, K.

    2014-01-28

    Extensive studies have already been reported on the optical characteristics of ZnO/polymer nanocomposite films, using a variety of polymers including transparent polymers such as polystyrene, polymethyl methacrylate etc and many interesting results have been established regarding the non linear optical characteristics of these systems. Poly (vinyl alcohol)(PVA) is a water soluble polymer. Though the structural and optical studies of ZnO/PVA nanocomposite films have already been investigated, there are no detailed reports on the nonlinear optical characteristics of ZnO/PVA nanocomposite films, irrespective of the fact that these nanocomposite films can be synthesized using quite easy and cost effective methods. The present work is an attempt to study in detail the nonlinear optical behaviour of ZnO/PVA nanocomposite films using Z-scan technique. Highly transparent ZnO/PVA nanocomposite films were prepared from the ZnO incorporated PVA solution in water using spin coating technique. The ZnO nanoparticles were synthesized by the simple chemical route at room temperature. High-resolution transmission electron microscopy studies show that the ZnO nanoparticles are of size around 10 nm. The ZnO/PVA nanocomposite films were structurally characterized by X-ray diffraction technique, from which the presence of both PVA and ZnO in the nanocomposite was established. The optical absorptive nonlinearity in the nanocomposite films was investigated using open aperture Z-scan technique. The results indicate optical limiting type nonlinearity in the films due to two photon absorption in ZnO with efficiency more than 50%. These films also show a self defocusing type negative nonlinear refraction in closed aperture Z-scan experiment. The present studies indicate that, highly transparent and homogeneous films of ZnO/PVA nanocomposite can be obtained on glass substrates using simple methods, in a highly cost effective way, since PVA is water soluble. These nanocomposite films offer

  4. A study of structure and dynamics of poly(aspartic acid) sodium/poly(vinyl alcohol) blends by 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Wang, P.; Ando, I.

    1999-09-01

    Solid state 13C CP/MAS NMR measurements have been carried out on poly(aspartic acid) sodium (PAANa)/poly(vinyl alcohol) (PVA) blends over a wide range of temperatures. From these experimental results, it is found that the main-chain conformations of PAANa in PAANa/PVA blends take the α-helix form over a wide range of blend ratios, and, in contrast, the conformation and dynamics of the side chains of PAANa are strongly influenced by the formation of an intermolecular hydrogen bond between the carboxyl group of the side chains and the hydroxyl group of PVA. The behavior of the proton spin-lattice relaxation times in the rotating frame ( T1 ρ(H)) and the laboratory frame ( T1(H)) indicates that when the blend ratio of PAANa and PVA is 1:1, they are miscible.

  5. Poly(anhydride-ester) and Poly(N-vinyl-2-pyrrolidone) Blends: Salicylic acid-releasing blends with hydrogel-like properties that reduce inflammation

    PubMed Central

    Ouimet, Michelle A.; Fogaça, Renata; Snyder, Sabrina S.; Sathaye, Sameer; Catalani, Luiz H.; Pochan, Darrin J.

    2015-01-01

    Polymers such as poly(N-vinyl-2-pyrrolidone) (PVP) have been used to prepare hydrogels for wound dressing applications but are not inherently bioactive. For enhanced healing, the release of physically admixed therapeutics from hydrogels has been evaluated, but with limited control over drug release profiles. To overcome these limitations, PVP was blended with salicylic acid-based poly(anhydride-esters) (SAPAE) and shown to exhibit hydrogel properties upon swelling. In vitro release studies demonstrated that the chemically incorporated drug (SA) was released from the polymer blends over 3–4 days in contrast to 3 hours, as observed with diffusion-controlled hydrogels. Generally, blends of higher PVP content displayed greater swelling values and faster SA release. The polymer blends significantly reduce the inflammatory cytokine, TNF-α, in vitro without cytotoxic or anti-proliferative effects, further demonstrating their potential as a wound dressing with enhanced healing and decreased scar tissue formation. PMID:25333420

  6. Effect of Cross-Linking on the Mechanical and Thermal Properties of Poly(amidoamine) Dendrimer/Poly(vinyl alcohol) Hybrid Membranes for CO2 Separation

    PubMed Central

    Duan, Shuhong; Kai, Teruhiko; Saito, Takashi; Yamazaki, Kota; Ikeda, Kenichi

    2014-01-01

    Poly(amidoamine) (PAMAM) dendrimers were incorporated into cross-linked poly(vinyl alcohol) (PVA) matrix to improve carbon dioxide (CO2) separation performance at elevated pressures. In our previous studies, PAMAM/PVA hybrid membranes showed high CO2 separation properties from CO2/H2 mixed gases. In this study, three types of organic Ti metal compounds were selected as PVA cross-linkers that were used to prepare PAMAM/cross-linked PVA hybrid membranes. Characterization of the PAMAM/cross-linked PVA hybrid membranes was conducted using nanoindentation and thermogravimetric analyses. The effects of the cross-linker and CO2 partial pressure in the feed gas on CO2 separation performance were discussed. H2O and CO2 sorption of the PAMAM/PVA hybrid membranes were investigated to explain the obtained CO2 separation efficiencies. PMID:24957172

  7. Investigation into the potential use of poly(vinyl alcohol)/methylglyoxal fibres as antibacterial wound dressing components.

    PubMed

    Bulman, Sophie E L; Goswami, Parikshit; Tronci, Giuseppe; Russell, Stephen J; Carr, Chris

    2015-03-01

    As problems of antibiotic resistance increase, a continuing need for effective bioactive wound dressings is anticipated for the treatment of infected chronic wounds. Naturally derived antibacterial agents, such as Manuka honey, consist of a mixture of compounds, more than one of which can influence antimicrobial potency. The non-peroxide bacteriostatic properties of Manuka honey have been previously linked to the presence of methylglyoxal. The incorporation of methylglyoxal as a functional antibacterial additive during fibre production was explored as a potential route for manufacturing wound dressing components. Synthetic methylglyoxal and poly(vinyl alcohol) were fabricated into webs of sub-micron fibres by means of electrostatic spinning of an aqueous spinning solution. Composite fabrics were also produced by direct deposition of the poly(vinyl alcohol)-methylglyoxal fibres onto a preformed spunbonded nonwoven substrate. Attenuated total reflectance fourier transform infrared and proton nuclear magnetic resonance spectroscopies confirmed the presence of methylglyoxal within the resulting fibre structure. The antibacterial activity of the fibres was studied using strains of Staphylococcus aureus and Escherichia coli. Strong antibacterial activity, as well as diffusion of methylglyoxal from the fibres was observed at a concentration of 1.55 mg/cm(2). © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  8. Antifreeze (glyco)protein mimetic behavior of poly(vinyl alcohol): detailed structure ice recrystallization inhibition activity study.

    PubMed

    Congdon, Thomas; Notman, Rebecca; Gibson, Matthew I

    2013-05-13

    This manuscript reports a detailed study on the ability of poly(vinyl alcohol) to act as a biomimetic surrogate for antifreeze(glyco)proteins, with a focus on the specific property of ice-recrystallization inhibition (IRI). Despite over 40 years of study, the underlying mechanisms that govern the action of biological antifreezes are still poorly understood, which is in part due to their limited availability and challenging synthesis. Poly(vinyl alcohol) (PVA) has been shown to display remarkable ice recrystallization inhibition activity despite its major structural differences to native antifreeze proteins. Here, controlled radical polymerization is used to synthesize well-defined PVA, which has enabled us to obtain the first quantitative structure-activity relationships, to probe the role of molecular weight and comonomers on IRI activity. Crucially, it was found that IRI activity is "switched on" when the polymer chain length increases from 10 and 20 repeat units. Substitution of the polymer side chains with hydrophilic or hydrophobic units was found to diminish activity. Hydrophobic modifications to the backbone were slightly more tolerated than side chain modifications, which implies an unbroken sequence of hydroxyl units is necessary for activity. These results highlight that, although hydrophobic domains are key components of IRI activity, the random inclusion of addition hydrophobic units does not guarantee an increase in activity and that the actual polymer conformation is important.

  9. Remediation of environmental pollution by substituting poly(vinyl alcohol) with biodegradable warp size from wheat gluten.

    PubMed

    Chen, Lihong; Reddy, Narendra; Yang, Yiqi

    2013-05-07

    We report the development of wheat gluten as an environmentally friendly sizing agent that can replace poly(vinyl alcohol) (PVA) and make the textile industry more environmentally friendly. Wheat gluten applied onto polyester/cotton (P/C) and polyester as warp sizing agent provided sizing performance and biodegradability in activated sludge necessary to substitute poly(vinyl alcohol) (PVA). PVA is one of the most widely used sizing agents and provides excellent sizing performance to synthetic fibers and their blends but is expensive and difficult to degrade in textile wastewater treatment plants. Although considerable efforts have been made to replace PVA, it has not been possible to develop a warp sizing chemical that can match the sizing performance of PVA and at the same time be cost-effective and biodegrade in effluent treatment plants. At similar % add-on, wheat gluten provided similar cohesion to P/C but much higher abrasion resistance to polyester fabrics compared to PVA. With a biochemical oxygen demand (BOD) to chemical oxygen demand (COD) ratio of 0.7 compared to 0.01 for PVA, wheat gluten was readily degradable in activated sludge. Wheat gluten has the ability to replace PVA for textile warp sizing applications.

  10. Simple, rapid and, cost-effective fabrication of PDMS electrophoresis microchips using poly(vinyl acetate) as photoresist master.

    PubMed

    Lobo-Júnior, Eulício O; Gabriel, Ellen F M; Dos Santos, Rodrigo A; de Souza, Fabrício R; Lopes, Wanderson D; Lima, Renato S; Gobbi, Angelo L; Coltro, Wendell K T

    2017-01-01

    This study describes a simple, rapid, and cost-effective fabrication of PDMS electrophoresis microchips using poly(vinyl acetate) (PVAc) emulsion as photoresist master. High-relief microfluidic structures were defined on poly(vinyl acetate) previously deposited on printed circuit boards surfaces without cleanroom facilities and sophisticated instrumentation. After a UV exposure, channels with heights ranging from 30 to 140 μm were obtained by controlling the emulsion mass deposited on the master surface. The developing stage was performed using water rather than the organic solvents that are applied for conventional masks. The surface morphology was characterized by optical imaging, profilometry, and SEM. Based on the achieved results, the proposed method offers suitable reproducibility for the prototyping of electrophoresis microchips in PDMS. The feasibility of the resulting PDMS electrophoresis chips was successfully demonstrated with the separation of major inorganic cations within 100 s using a contactless conductivity detection system. The separation efficiencies ranged from ca. 67 900 to 125 600 plates/m. Due to the satisfactory performance and simplified instrumentation, we believe this fabrication protocol presents potential to be implemented in any chemical, biochemical, or biological laboratory.

  11. Poly(vinyl chloride) blend with biodegradable cellulose acetate in presence of N-(phenyl amino) maleimides.

    PubMed

    Abdel-Naby, Abir S; Al-Ghamdi, Azza A

    2014-09-01

    Wider plastic applications of poly(vinyl chloride) (PVC) has raised serious problem to the environment. Since (PVC) waste products resist biodegradation and persist in the environment for longer time. The object of this study is to blend (PVC) with biodegradable cellulose acetate to thermally support the polymer during the molding process as well as to enhance the biodegradability of (PVC) waste products. Blending of poly(vinyl chloride) and cellulose acetate (CA) in presence of N-(phenyl amino) maleimides (R-PhAM) where (R=H, 4-NO2) led to improvement in the thermal stability of the blend film at high temperatures as shown from the high values of initial decomposition temperature (To) determined from their thermogravimetry (TG) curves. Also, blending (PVC) with (CA) led to improvement in the mechanical properties of the blend films as compared to (PVC). The crystalline regions of cellulose acetate enhanced the elasticity of the blend films as shown from their high Young's modulus values.

  12. Coating gigaporous polystyrene microspheres with cross-linked poly(vinyl alcohol) hydrogel as a rapid protein chromatography matrix.

    PubMed

    Qu, Jian-Bo; Huan, Guan-Sheng; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo; Huang, Fang

    2014-08-13

    Gigaporous polystyrene (PS) microspheres were hydrophilized by in situ polymerization to give a stable cross-linked poly(vinyl alcohol) (PVA) hydrogel coating, which can shield proteins from the hydrophobic PS surface underneath. The amination of microspheres (PS-NH2) was first carried out through acetylization, oximation and reduction, and then 4,4'-azobis (4-cyanovaleric acid) (ACV), a polymerization initiator, was covalently immobilized on PS-NH2 through amide bond formation, and the cross-linked poly(vinyl acetate) (PVAc) was prepared by radical polymerization at the surfaces of ACV-immobilized PS microspheres (PS-ACV). Finally, the cross-linked PVA hydrogel coated gigaporous PS microspheres (PS-PVA) was easily achieved through alcoholysis of PVAc. Results suggested that the PS microspheres were effectively coated with cross-linked PVA hydrogel, where the gigaporrous structure remained under optimal conditions. After hydrophilic modification (PS-PVA), the protein-resistant ability of microspheres was greatly improved. The hydroxyl-rich PS-PVA surface can be easily derivatized by classical chemical methods. Performance advantages of the PS-PVA column in flow experiment include good permeability, low backpressure, and mechanical stability. These results indicated that PS-PVA should be promising in rapid protein chromatography.

  13. In vitro mechanical fatigue behavior of poly-ɛ-caprolactone macroporous scaffolds for cartilage tissue engineering: Influence of pore filling by a poly(vinyl alcohol) gel.

    PubMed

    Panadero, J A; Vikingsson, L; Gomez Ribelles, J L; Lanceros-Mendez, S; Sencadas, V

    2015-07-01

    Polymeric scaffolds used in regenerative therapies are implanted in the damaged tissue and submitted to repeated loading cycles. In the case of articular cartilage engineering, an implanted scaffold is typically subjected to long-term dynamic compression. The evolution of the mechanical properties of the scaffold during bioresorption has been deeply studied in the past, but the possibility of failure due to mechanical fatigue has not been properly addressed. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. In this work fatigue studies of polycaprolactone scaffolds were carried by subjecting the scaffold to repeated compression cycles in conditions simulating the scaffold implanted in the articular cartilage. The behavior of the polycaprolactone sponge with the pores filled with a poly(vinyl alcohol) gel simulating the new formed tissue within the pores was compared with that of the material immersed in water. Results were analyzed with Morrow's criteria for failure and accurate fittings are obtained just up to 200 loading cycles. It is also shown that the presence of poly(vinyl alcohol) increases the elastic modulus of the scaffolds, the effect being more pronounced with increasing the number of freeze/thawing cycles. © 2014 Wiley Periodicals, Inc.

  14. Combined nitric oxide-releasing poly(vinyl alcohol) film/F127 hydrogel for accelerating wound healing.

    PubMed

    Schanuel, Fernanda Seabra; Raggio Santos, Karen Slis; Monte-Alto-Costa, Andréa; de Oliveira, Marcelo G

    2015-06-01

    Nitric oxide (NO) releasing biomaterials represent a potential strategy for use as active wound dressings capable of accelerating wound healing. Topical NO-releasing poly(vinyl alcohol) (PVA) films and Pluronic F127 hydrogels (F127) have already exhibited effective skin vasodilation and wound healing actions. In this study, we functionalized PVA films with SNO groups via esterification with a mixture of mercaptosucinic acid (MSA) and thiolactic acid (TLA) followed by S-nitrosation of the SH moieties. These films were combined with an underlying layer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), i.e., PEO-PPO-PEO (Pluronic F127) hydrogel and used for the topical treatment of skin lesions in an animal model. The mixed esterification of PVA with MSA and TLA led to chemically crosslinked PVA-SNO films with a high swelling capacity capable of spontaneously releasing NO. Real time NO-release measurements revealed that the hydrogel layer reduces the initial NO burst from the PVA-SNO films. We demonstrate that the combination of PVA-SNO films with F127 hydrogel accelerates wound contraction, decreases wound gap and cellular density and accelerates the inflammatory phase of the lesion. These results were reflected in an increase in myofibroblastic differentiation and collagen type III expression in the cicatricial tissue. Therefore, PVA-SNO films combined with F127 hydrogel may represent a new approach for active wound dressings capable of accelerating wound healing.

  15. Polycaprolactone-poly(ethylene glycol) multiblock copolymers as potential substitutes for di(ethylhexyl) phthalate in flexible poly(vinyl chloride) formulations.

    PubMed

    Ferruti, Paolo; Mancin, Ivan; Ranucci, Elisabetta; De Felice, Claudio; Latini, Giuseppe; Laus, Michele

    2003-01-01

    New high-molecular-weight hydrophobic/hydrophilic segmented copolymers of poly(ester ether carbonate) structure, containing poly(epsilon-caprolactone) (PCL) and poly(ethylene glycol) (PEG) segments in their main chain, were synthesized and characterized. These copolymers were obtained by a two-step chain-extension reaction carried out in the presence of alpha,omega-dihydroxy-oligoPCL of molecular weight 1250 and PEG samples of molecular weight 150, 400, 600, 1000, and 2000. The molecular structures of all synthesized materials were characterized by means of (1)H NMR and (13)C NMR spectroscopy, their molecular weights were determined by means of size exclusion chromatography, and their thermal properties were obtained by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The poly(ester ether carbonate)s of this study are partly or totally miscible at least up to 50 wt % with poly(vinyl chloride) (PVC) and could be used to produce flexible PVC formulations. The miscibility between PVC and the poly(ester ether carbonate)s reported in this paper was investigated by means of DSC and DMA analysis. PVC blends were also analyzed by determining their swellability and the amount of extractables in aqueous media. By comparison purposes, the chain-extension product of PCL1250, that is, PCL polycarbonate, was also synthesized and characterized. The results obtained demonstrated that the copolymers with shortest PEG segment length, i.e. PEG150, 400, and 600, give the best results in terms of miscibility with PVC and lead to blends with maximum resistance to extraction by water. Therefore, they represent, in principle, good substitutes for low-molecular-weight, leachable PVC plasticizers, such as di(ethylhexyl) phthalate.

  16. Poly(vinyl alcohol)-coated chitosan microparticles act as an effective oral vaccine delivery system for hepatitis B vaccine in rat model.

    PubMed

    Shrestha, Bijaya; Rath, Jyoti Prakash

    2014-12-01

    The present study focused on the development of an effective oral vaccine delivery system of poly(vinyl alcohol)-coated chitosan microparticles-based recombinant hepatitis B vaccine. Chitosan microparticles were prepared by ionotropic gelation technique; they were loaded with recombinant hepatitis B vaccine and coated with poly(vinyl alcohol). The average sizes of the microparticles were measured in the range of 100-410 nm. The optimal loading capacity and loading efficiency were recorded around 3.4 and 74%, respectively. In vitro release study shows that the prepared microparticles release the antigen in a sustained manner. Moreover, the microparticles were resistant to simulated gastric environment and release the antigen in the targeted intestinal milieu. Furthermore, oral immunisation of rats with poly(vinyl alcohol)-coated chitosan hepatitis-B microparticles vaccine shows comparable seroprotective immune response to presently practiced intramuscular vaccination. The results demonstrated that poly(vinyl alcohol)-coated chitosan microparticles have the potential for being used as an oral vaccine delivery system for hepatitis B vaccine and may be a suitable alternative for needle-based vaccination.

  17. Films prepared from poly(vinyl alcohol) and amylose-fatty acid salt inclusion complexes with increased surface hydrophobicity and high elongation

    USDA-ARS?s Scientific Manuscript database

    In this study, water-soluble amylose-inclusion complexes were prepared from high amylose corn starch and sodium salts of lauric, palmitic, and stearic acid by steam jet cooking. Cast films were prepared by combining the amylose complexes with poly(vinyl alcohol)(PVOH) solution at ratios varying from...

  18. MICROWAVE-ASSISTED SYNTHESIS OF CROSSLINKED POLY(VINYL ALCOHOL) NANOCOMPOSITES COMPRISING SINGLE-WALLED CARBON NANOTUBES, MULTI-WALLED CARBON NANOTUBES AND BUCKMINSTERFULLERENE

    EPA Science Inventory

    We report a facile method to accomplish cross-linking reaction of poly (vinyl alcohol) (PVA) with single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT), and Buckminsterfullerene (C-60) using microwave (MW) irradiation. Nanocomposites of PVA cross-linked with SW...

  19. MICROWAVE-ASSISTED SYNTHESIS OF CROSSLINKED POLY(VINYL ALCOHOL) NANOCOMPOSITES COMPRISING SINGLE-WALLED CARBON NANOTUBES, MULTI-WALLED CARBON NANOTUBES AND BUCKMINSTERFULLERENE

    EPA Science Inventory

    We report a facile method to accomplish cross-linking reaction of poly (vinyl alcohol) (PVA) with single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT), and Buckminsterfullerene (C-60) using microwave (MW) irradiation. Nanocomposites of PVA cross-linked with SW...

  20. Statistics-enhanced multistage process models for integrated design &manufacturing of poly (vinyl alcohol) treated buckypaper

    NASA Astrophysics Data System (ADS)

    Wang, Kan

    Carbon nanotube (CNT) is considered a promising engineering material because of its exceptional mechanical, electrical, and thermal properties. Buckypaper (BP), a thin sheet of assembled CNTs, is an effective way to handle CNTs in macro scale. Pristine BP is a fragile material which is held together by weak van der Waals attractions among CNTs. This dissertation introduces a modified filtration based manufacturing process which uses poly (vinyl alcohol) (PVA) to treat BP. This treatment greatly improves the handleability of BP, reduces the spoilage during transferring, and shortens the production time. The multistage manufacturing process of PVA-treated BP is discussed in this dissertation, and process models are developed to predict the nanostructure of final products from the process parameters. Based on the nanostructure, a finite element based physical model for prediction of Young's modulus is also developed. This accuracy of this physical model is further improved by statistical methods. The aim of this study is to investigate and improve the scalability of the manufacturing process of PVA-treated BP. To achieve this goal, various statistical tools are employed. The unique issues in nanomanufacturing also motivate the development of new statistical tools and modification of existing tools. Those issues include the uncertainties in nanostructure characterization due to the scale, limited number experimental data due to high cost of raw materials, large variation in final product due to the random nature in structure, and the high complexity in physical models due to the small scale of structural building blocks. This dissertation addresses those issues by combining engineering field knowledge and statistical methods. The resulting statistics-enhanced physical model provides an approach to design the manufacturing process of PVA-treated BP for a targeting property and tailor the robustness of the final product by manipulating the process parameters. In addition

  1. Preparation of Poly(Dinitropropyl Vinyl Ether) with Crosslinking Sites, for Use as a Castable Binder

    DTIC Science & Technology

    1978-12-01

    GPC of Modified and Unmodified Poly-DNPVE ............. 7 3 100 MHz NMR Spectrum of Poly-DNPVE (M.W. 4,000) ...... 18 4 220 MHz NMR Spectrum of Poly...DNPVE in d 6- Acetone/DCl/D 2 0 .................. 19 5 100 MHz NMR Spectrum of Poly-DNPVE (M.W. 4,000), Partially Reduced...20 6 100 MHz NMR Spectrum of Poly-DNPVE (M.W. 4,000), Partially Reduced and Hydroxymethylated .............. 21 TABLES Table Page 1 Reaction

  2. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

    SciTech Connect

    Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; Mehio, Nada; Li, Meijun; Gill, Gary; Tsouris, Costas; Mayes, Richard T.; Saito, Tomonori; Dai, Sheng

    2016-03-11

    The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly-(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligands (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42 3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Lastly, adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.

  3. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

    SciTech Connect

    Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; Mehio, Nada; Li, Meijun; Gill, Gary; Tsouris, Costas; Mayes, Richard T.; Saito, Tomonori; Dai, Sheng

    2016-04-20

    The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly- (vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligands (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42-3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.

  4. In situ formation of poly(vinyl alcohol)–heparin hydrogels for mild encapsulation and prolonged release of basic fibroblast growth factor and vascular endothelial growth factor

    PubMed Central

    Roberts, Justine J; Farrugia, Brooke L; Green, Rylie A; Rnjak-Kovacina, Jelena; Martens, Penny J

    2016-01-01

    Heparin-based hydrogels are attractive for controlled growth factor delivery, due to the native ability of heparin to bind and stabilize growth factors. Basic fibroblast growth factor and vascular endothelial growth factor are heparin-binding growth factors that synergistically enhance angiogenesis. Mild, in situ encapsulation of both basic fibroblast growth factor and vascular endothelial growth factor and subsequent bioactive dual release has not been demonstrated from heparin-crosslinked hydrogels, and the combined long-term delivery of both growth factors from biomaterials is still a major challenge. Both basic fibroblast growth factor and vascular endothelial growth factor were encapsulated in poly(vinyl alcohol)-heparin hydrogels and demonstrated controlled release. A model cell line, BaF32, was used to show bioactivity of heparin and basic fibroblast growth factor released from the gels over multiple days. Released basic fibroblast growth factor promoted higher human umbilical vein endothelial cell outgrowth over 24 h and proliferation for 3 days than the poly(vinyl alcohol)-heparin hydrogels alone. The release of vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels promoted human umbilical vein endothelial cell outgrowth but not significant proliferation. Dual-growth factor release of basic fibroblast growth factor and vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels resulted in a synergistic effect with significantly higher human umbilical vein endothelial cell outgrowth compared to basic fibroblast growth factor or vascular endothelial growth factor alone. Poly(vinyl alcohol)-heparin hydrogels allowed bioactive growth factor encapsulation and provided controlled release of multiple growth factors which is beneficial toward tissue regeneration applications. PMID:27895888

  5. In situ formation of poly(vinyl alcohol)-heparin hydrogels for mild encapsulation and prolonged release of basic fibroblast growth factor and vascular endothelial growth factor.

    PubMed

    Roberts, Justine J; Farrugia, Brooke L; Green, Rylie A; Rnjak-Kovacina, Jelena; Martens, Penny J

    2016-01-01

    Heparin-based hydrogels are attractive for controlled growth factor delivery, due to the native ability of heparin to bind and stabilize growth factors. Basic fibroblast growth factor and vascular endothelial growth factor are heparin-binding growth factors that synergistically enhance angiogenesis. Mild, in situ encapsulation of both basic fibroblast growth factor and vascular endothelial growth factor and subsequent bioactive dual release has not been demonstrated from heparin-crosslinked hydrogels, and the combined long-term delivery of both growth factors from biomaterials is still a major challenge. Both basic fibroblast growth factor and vascular endothelial growth factor were encapsulated in poly(vinyl alcohol)-heparin hydrogels and demonstrated controlled release. A model cell line, BaF32, was used to show bioactivity of heparin and basic fibroblast growth factor released from the gels over multiple days. Released basic fibroblast growth factor promoted higher human umbilical vein endothelial cell outgrowth over 24 h and proliferation for 3 days than the poly(vinyl alcohol)-heparin hydrogels alone. The release of vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels promoted human umbilical vein endothelial cell outgrowth but not significant proliferation. Dual-growth factor release of basic fibroblast growth factor and vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels resulted in a synergistic effect with significantly higher human umbilical vein endothelial cell outgrowth compared to basic fibroblast growth factor or vascular endothelial growth factor alone. Poly(vinyl alcohol)-heparin hydrogels allowed bioactive growth factor encapsulation and provided controlled release of multiple growth factors which is beneficial toward tissue regeneration applications.

  6. Fabrication of thermo-responsive cotton fabrics using poly(vinyl caprolactam-co-hydroxyethyl acrylamide) copolymer.

    PubMed

    Xiao, Min; González, Edurne; Monterroza, Alexis Martell; Frey, Margaret

    2017-10-15

    A thermo-responsive polymer with hydrophilic to hydrophobic transition behavior, poly(vinyl caprolactam-co-hydroxyethyl acrylamide) P(VCL-co-HEAA), was prepared by copolymerization of vinyl caprolactam and N-hydroxyethyl acrylamide via free radical solution polymerization. The resulting copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), (1)H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The lower critical solution temperature (LCST) of P(VCL-co-HEAA) was determined at 34.5°C. This thermo-responsive polymer was then grafted onto cotton fabrics using 1,2,3,4-butanetetracarboxylic acid (BTCA) as crosslinker and sodium hypophosphite (SHP) as catalyst. FTIR and energy dispersive X-ray spectroscopy (EDS) studies confirmed the successful grafting reaction. The modified cotton fabric exhibited thermo-responsive behavior as evidenced by water vapor permeability measurement confirming decreased permeability at elevated temperature. This is the first demonstration that a PVCL based copolymer is grafted to cotton fabrics. This study provides a new thermo-responsive polymer for fabrication of smart cotton fabrics with thermally switchable hydrophilicity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. An organic dye-polymer (phenol red-poly (vinyl alcohol)) composite architecture towards tunable -optical and -saturable absorption characteristics

    SciTech Connect

    Sreedhar, Sreeja Muneera, C. I.; Illyaskutty, Navas; Sreedhanya, S.; Philip, Reji

    2016-05-21

    Herein, we demonstrate that blending an organic dye (guest/filler), with a vinyl polymer (host template), is an inexpensive and simple approach for the fabrication of multifunctional photonic materials which could display an enhancement in the desirable properties of the constituent materials and, at the same time provide novel synergistic properties for the guest-host system. A new guest-host nanocomposite system comprising Phenol Red dye and poly (vinyl alcohol) as guest and host template, respectively, which exhibits tunable optical characteristics and saturable absorption behavior, is introduced. The dependence of local electronic environment provided by the polymer template and the interactions of the polymer molecules with the encapsulated guest molecules on the observed optical/nonlinear absorption behavior is discussed. An understanding of the tunability of the optical/ photophysical processes, with respect to the filler content, as discussed herein could help in the design of improved optical materials for several photonic device applications like organic light emitting diodes and saturable absorbers.

  8. Anion effects on anti-microbial activity of poly[1-vinyl-3-(2-sulfoethyl imidazolium betaine)].

    PubMed

    Garg, Godawari; Chauhan, Ghanshyam S; Gupta, Reena; Ahn, J-H

    2010-04-01

    Recent investigations in the anti-microbial properties of the functional polymers are predominantly focused on the structure of the cationic moieties. In the present study, we investigated that the nature of the anion present in polysulfobetaines affects activity against certain microorganisms and their anti-microbial properties have been rationalized in terms of the structure-activity relationship. Vinyl imidazolium-based polysulfobetaines were prepared by the quaternization of poly(N-vinyl imidazole) with sodium salt of 2-bromo ethanesulfonic acid. The bromide counter anion of the resulting polymer was exchanged with different anions to generate a series of polymers. These were characterized by FTIR, DSC, XRD, SEM, elemental analysis (C, H, N and S) and viscosity measurements. The anti-microbial activity studies were carried against three fungi (Aspergillus niger, Byssochlamys fulva and Mucor circenelliods) and two bacteria (Bacillus coagulans BTS-3 and Pseudomonas aeruginosa BTS-2). The nature of the anion affects the structure of polysulfobetaine by realignment of polymer chains. The anion-dependent anti-microbial properties of polysulfobetaines result from the interaction of the microbes at the polymer interface.

  9. Recyclable magnetic nanocluster crosslinked with poly(ethylene oxide)-block-poly(2-vinyl-4,4-dimethylazlactone) copolymer for adsorption with antibody.

    PubMed

    Prai-In, Yingrak; Boonthip, Chatchai; Rutnakornpituk, Boonjira; Wichai, Uthai; Montembault, Véronique; Pascual, Sagrario; Fontaine, Laurent; Rutnakornpituk, Metha

    2016-10-01

    Surface modification of magnetic nanoparticle (MNP) with poly(ethylene oxide)-block-poly(2-vinyl-4,4-dimethylazlactone) (PEO-b-PVDM) diblock copolymers and its application as recyclable magnetic nano-support for adsorption with antibody were reported herein. PEO-b-PVDM copolymers were first synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization using poly(ethylene oxide) chain-transfer agent as a macromolecular chain transfer agent to mediate the RAFT polymerization of VDM. They were then grafted on amino-functionalized MNP by coupling with some azlactone rings of the PVDM block to form magnetic nanoclusters with tunable cluster size. The nanocluster size could be tuned by adjusting the chain length of the PVDM block. The nanoclusters were successfully used as efficient and recyclable nano-supports for adsorption with anti-rabbit IgG antibody. They retained higher than 95% adsorption of the antibody during eight adsorption-separation-desorption cycles, indicating the potential feasibility in using this novel hybrid nanocluster as recyclable support in cell separation applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Influence of poly(ethylene glycol) as pore-generator on morphology and performance of chitosan/poly(vinyl alcohol) membrane adsorbents

    NASA Astrophysics Data System (ADS)

    Salehi, E.; Madaeni, S. S.

    2014-01-01

    Macroporous chitosan/poly(vinyl alcohol) membrane adsorbents were synthesized by solvent evaporation in the presence of poly(ethylene glycol) which was utilized as porogen. The membranes were applied for Cu(II) ion adsorption from water. SEM, AFM and wettability analyses were performed for membrane characterization. Insertion of poly(ethylene glycol) generated macrovoids in the dense structure of CS/PVA membranes through particulate leaching out mechanism. According to the static adsorption tests, the uptake capacity of the porous membranes is elevated (∼26 mg/g) compared to that of the dense membranes (∼10 mg/g). This phenomenon is attributed to the increase in the density of active sites, water affinity and surface roughness as a result of the porogen effects. The approachability of the ions to the active sites was also affected by these important parameters. Both size and density of the macrovoids increased with increasing PEG content from nil to 5 wt%. Fragility of the resultant porous structures prohibited synthesizing CS/PVA membranes with higher porogen contents. Desorption tests showed that the porous membranes were better regenerated in comparison to the dense membranes using Na2EDTA as eluant. Generally, the results suggested that the CS/PVA membranes, comprising PEG as pore-generator agent, are potential candidates for adsorption and elimination of Cu(II) ions from water.

  11. Study of behaviour on simulated daylight ageing of artists' acrylic and poly(vinyl acetate) paint films.

    PubMed

    Doménech-Carbó, María Teresa; Silva, Miguel F; Aura-Castro, Elvira; Fuster-López, Laura; Kröner, Stephan; Martínez-Bazán, María Luisa; Más-Barberá, Xavier; Mecklenburg, Marion F; Osete-Cortina, Laura; Doménech, Antonio; Gimeno-Adelantado, José Vicente; Yusá-Marco, Dolores Julia

    2011-03-01

    This work proposes a multi-method approach that combines advanced microscopy (SEM/EDX, AFM) and spectroscopy (UV-vis and FTIR) techniques. This approach not only characterises the behaviour of the additives of two commercial poly(vinyl acetate) (PVAc) and acrylic emulsion paints but also simultaneously characterises the changes in chemical composition and morphology observed in the paint films as a result of ageing due to the paints being exposed to an intense source of simulated daylight. In parallel, a series of mechanical tests were performed that correlate the chemical changes in composition and the changes observed in the films' mechanical properties. This work was a comparative study between both types of acrylic and PVAc paints. The results obtained are of great interest for the modern paint conservation field as they provide valuable information on the mid- and long-term behaviours of these synthetic paints.

  12. Electro-optical properties of one pot synthesized polyindole in the presence of poly(vinyl acetate)

    NASA Astrophysics Data System (ADS)

    Bhagat, D. J.; Dhokane, G. R.

    2015-05-01

    Polyindole was prepared in the presence of poly(vinyl acetate) through a chemical polymerization technique. The indole monomer was polymerized using ferric chloride as an oxidant. Electrical conductivity measurements were performed through a two probe technique. The prepared composites were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), energy dispersive x-ray spectroscopy (EDAX), and ultraviolet-visible (UV-VIS) spectroscopy. The DC conductivity was found to be 4.46 × 10-6 S/cm at 383 K. An attempt has been made to investigate the electrooptical properties of PIN/PVAc composite films.[Figure not available: see fulltext.

  13. Effect of tissue-engineered chitosan-poly(vinyl alcohol) nanofibrous scaffolds on healing of burn wounds of rat skin.

    PubMed

    Gholipour-Kanani, A; Bahrami, S H; Samadi-Kochaksaraie, A; Ahmadi-Tafti, H; Rabbani, S; Kororian, A; Erfani, E

    2012-12-01

    Chitosan-poly(vinyl alcohol) (Cs:PVA) nanofibrous scaffolds were electrospun from 2:3 (wt/wt) Cs:PVA solution dissolved in 80% acetic acid. In vivo study was carried out on the dorsum skin of rat which burnt with a hot brass cylinder. The scaffolds were applied in two forms, that is, acellular (n=6) and cell-seeded with mesenchymal stem cells (n=6). Macroscopic measurements of wound area showed good aspect healing effect of scaffolds in comparison with control wounds specially in 15 days post operating. Pathological studies were done on the wounds to investigate the healing effects. The healing process of the wound covered with Cs/PVA nanofibrous scaffolds was much rapid compared to untreated wounds. However, the presence of stem cells on this scaffolds accelerated the wound healing process owing to their ability of collagen regeneration.

  14. Negative giant magnetoresistance effect in single layered superparamagnetic polymer nanocomposite structures of poly(vinyl alcohol)-polyaniline/bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Prabhakaran, T.; Hemalatha, J.

    2012-08-01

    Superparamagnetic polyaniline/bismuth ferrite (PANI/BFO) nanocomposite powder is synthesized through an in situ sol-gel polymerization method and it is embedded in non-magnetic poly(vinyl alcohol) (PVA) matrix to fabricate high performance flexible films. The interaction between PANI/BFO filler and PVA matrix and hence the formation of composite is identified through XRD and it is further confirmed through FTIR spectra. Vibration sample magnetometry (VSM) studies ensure the superparamagnetic nature of the composite films. The magnetoresistance measurements are made at room temperature for various current values from which it is observed that the samples exhibit a negative giant magnetoresistance (GMR) effect. The variation of GMR from 21% to 66% with filler concentration and also the non-ohmic V-I characteristics of the composite films are reported.

  15. A double-membrane ephedrine selective electrode based on ephedrine-tetraphenylborate in poly (vinyl chloride) resin.

    PubMed

    Chamorro, P R; Díaz, R C

    1993-09-01

    The construction and performance characteristics of a double-membrane ephedrine selective electrode are described. The electrode is based on the use of an internal conducting membrane made of tetrabutylammonium bromide and another external electroactive membrane containing the ionic pair ephedrine-tetraphenylborate in a poly (vinyl chloride) resin (with some plasticizers incorporated) as an inert matrix. The ephedrine electrode exhibits linear Nernstian response within the range 10(-2)-5 x 10(-5)M of ephedrine, with a slope of 58.2 +/- 0.5 mV decade(-1) at 25 +/- 0.2 degrees . The detection limit is 10(-4.5)M. The reproducibility (coefficient of variation) was 0.54% (n = 10 determinations) and the stability of its potential is 2.3 mV/24 h. The selectivity coefficients for 15 ions were calculated. The electrode was applied to the determination of ephedrine in some pharmaceutical preparations with satisfactory results.

  16. Neutron spin-echo studies on dynamic and static fluctuations in two types of poly(vinyl alcohol) gels

    SciTech Connect

    Kanaya, T.; Takahashi, N.; Nishida, K.; Seto, H.; Nagao, M.; Takeda, T.

    2005-01-01

    We report neutron spin-echo measurements on two types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40, and the second is PVA gel in an aqueous borax solution. The observed normalized intermediate scattering functions I(Q,t)/I(Q,0) are very different between them. The former I(Q,t)/I(Q,0) shows a nondecaying component in addition to a fast decay, but the latter does not have the nondecaying one. This clearly indicates that the fluctuations in the former PVA gel consist of static and dynamic fluctuations whereas the latter PVA gel does include only the dynamic fluctuations. The dynamic fluctuations of the former and latter gels have been analyzed in terms of a restricted motion in the network and Zimm motion, respectively, and the origins of these motions will be discussed.

  17. Neutron spin-echo studies on dynamic and static fluctuations in two types of poly(vinyl alcohol) gels

    NASA Astrophysics Data System (ADS)

    Kanaya, T.; Takahashi, N.; Nishida, K.; Seto, H.; Nagao, M.; Takeda, T.

    2005-01-01

    We report neutron spin-echo measurements on two types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40 , and the second is PVA gel in an aqueous borax solution. The observed normalized intermediate scattering functions I(Q,t)/I(Q,0) are very different between them. The former I(Q,t)/I(Q,0) shows a nondecaying component in addition to a fast decay, but the latter does not have the nondecaying one. This clearly indicates that the fluctuations in the former PVA gel consist of static and dynamic fluctuations whereas the latter PVA gel does include only the dynamic fluctuations. The dynamic fluctuations of the former and latter gels have been analyzed in terms of a restricted motion in the network and Zimm motion, respectively, and the origins of these motions will be discussed.

  18. Preparation and properties of a hydrogel of maleated poly(vinyl alcohol) (PVAM) grafted with cassava starch.

    PubMed

    Riyajan, Sa-Ad; Sukhlaaied, Wattana; Keawmang, Woranut

    2015-05-20

    A novel pH-sensitive graft copolymer (PVAM-g-CSt) was synthesized from maleated poly(vinyl alcohol) (PVAM) and cassava starch (CSt) through a grafting reaction using potassium persulfate as a thermal initiator. The chemical structure of the PVAM-g-CSt was revealed by FTIR and ether linkage of the graft copolymer was observed at 1089 cm(-1). The degree of grafting of the copolymer was found to range between 40 and 82%, depending on the PVAM/CSt ratio. The highest tensile strength was found at a ratio of 9:1 PVAM/CSt. In addition, the swelling ratio in water increased with increasing proportions of CSt in the PVAM-g-CSt due to the decrease in the degree of grafting. The resulting hydrogel exhibits good pH sensitivity in different pH mediums. The graft copolymer easily degraded in natural soil, especially at high proportions of CSt in the blend.

  19. Evaluation of an ammonium ionophore for use in poly(vinyl chloride) membrane ion-selective electrodes: solvent mediator effects.

    PubMed

    Ghauri, M S; Thomas, J D

    1994-11-01

    A macrotetrolide nonactin-based ammonium ionophore (AI) preparation containing 25% nonactin optimized for use in liquid membrane ion-selective electrodes was investigated for its possible use in poly(vinyl chloride) (PVC) matrix membrane-type electrodes. Nine different plasticizing solvent mediators were employed in the ammonium ion-selective membranes with PVC and the AI preparation. Near Nernstian responses were observed in aqueous solution with electrodes fabricated with dioctyl sebacate-, 2-nitrophenyl phenyl ether-, dibutyl sebacate-, trioctyl phosphate-, dioctyl adipate-, dioctyl phenyl phosphonate- and 2-nitrophenyl octyl ether-plasticized membranes. The responses of these electrodes were found to improve in the presence of a background concentration of non-interfering calcium ions.

  20. Michael-type addition reactions for the in situ formation of poly(vinyl alcohol)-based hydrogels.

    PubMed

    Tortora, Mariarosaria; Cavalieri, Francesca; Chiessi, Ester; Paradossi, Gaio

    2007-01-01

    Michael-type addition reactions offer the possibility to obtain in situ formation of polymeric hydrogels in the absence of a radical mechanism for the networking process. We explored such a synthetic route for obtaining a poly(vinyl alcohol) (PVA)-based hydrogel as a potential biomaterial for applications in vitro-retinal replacement surgery. The presence of radicals in the reaction medium can represent a risk for in situ surgical treatment. To circumvent this problem we have applied nucleophilic addition to ad hoc modified PVA macromers. The gel formation has been studied with respect to the timing required in this surgery and in terms of the structural characteristics of the obtained network.

  1. Colorful Hydrophobic Poly(Vinyl Butyral)/Cationic Dye Fibrous Membranes via a Colored Solution Electrospinning Process

    NASA Astrophysics Data System (ADS)

    Yan, Xu; You, Ming-Hao; Lou, Tao; Yu, Miao; Zhang, Jun-Cheng; Gong, Mao-Gang; Lv, Fu-Yan; Huang, Yuan-Yuan; Long, Yun-Ze

    2016-12-01

    Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting.

  2. Colloidal Properties of Aqueous Poly(vinyl acetate)-Borate Dispersions with Short-Chain Glycol Ethers.

    PubMed

    Duncan, Teresa T; Berrie, Barbara H; Weiss, Richard G

    2016-08-18

    We report the influence of adding five short-chain glycol ethers (SCGEs) on the structure, stability, and viscoelastic properties of aqueous dispersions of partially hydrolyzed poly(vinyl acetate) and borax. The properties of these gel-like materials have been investigated as a function of the structure of the added SCGE both below and above the critical aggregation (or micellar) concentrations using (11) B and (13) C NMR, rheology, and small-angle neutron scattering. The results indicate that the SCGE aggregation behavior is not affected by incorporation into the gel-like network. However, changes in the viscoelasticity and structural properties of the dispersions were detected that can be correlated to the nature of the solvent system. Also, the ability of these materials to clean an unvarnished acrylic paint surface coated with synthetic soil has been evaluated using colorimetery, and the surface of the dispersion after cleaning was visualized with scanning electron microscopy.

  3. Strong Surface Treatment Effects on Reinforcement Efficiency in Biocomposites Based on Cellulose Nanocrystals in Poly(vinyl acetate) Matrix.

    PubMed

    Ansari, Farhan; Salajková, Michaela; Zhou, Qi; Berglund, Lars A

    2015-12-14

    In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

  4. Use of fluorescence for the high-throughput evaluation of synergistic thermal and photo stabilizer interactions in poly (vinyl chloride)

    SciTech Connect

    Wu Chunyong; Wicks, Douglas A.

    2005-06-15

    The selection of thermal and photo stabilizers for poly (vinyl chloride) (PVC) using conventional methods is a time-consuming process. The high-throughput screening method developed in this research demonstrates rapid and efficient ways to quantify the effectiveness of PVC stabilizers with respect to raw plastic materials, stabilizers, levels of use, and testing conditions. An experimental protocol using liquid sampling and fluorescence measurement was developed to determine the effectiveness of formulations. This was used to evaluate the performance of stabilizers based on the change of fluorescence emission at 440 nm after thermal aging or ultraviolet (UV) radiation. The performance of PVC formulations using six different types of stabilizers was successfully mapped for both PVC resin and flexible PVC.

  5. Colorful Hydrophobic Poly(Vinyl Butyral)/Cationic Dye Fibrous Membranes via a Colored Solution Electrospinning Process.

    PubMed

    Yan, Xu; You, Ming-Hao; Lou, Tao; Yu, Miao; Zhang, Jun-Cheng; Gong, Mao-Gang; Lv, Fu-Yan; Huang, Yuan-Yuan; Long, Yun-Ze

    2016-12-01

    Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting.

  6. Polyene Formation Catalyzed by Phosphotungstic Acid and Aluminum Chloride in Thin Films of Poly(Vinyl Alcohol)

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Maly, A. B.

    2016-01-01

    Formation of linear polyenes -(CH=CH) n - during thermal dehydration of thin layers (9-20 μm) of poly(vinyl alcohol) containing phosphotungstic-acid and aluminum-chloride catalysts was investigated. It was found that the concentration of long-chain ( n ≥ 8) polyenes in films containing phosphotungstic acid increased smoothly with increasing annealing time although the kinetics of the dehydration were independent of the film thickness. The polyene ( n ≥ 8) formation rate in films containing aluminum chloride dropped quickly with decreasing film thickness and increasing annealing time. As a result, long-chain polyenes practically did not form regardless of the annealing time for a film thickness of 11 μm.

  7. Radiation preparation of graphene/carbon nanotubes hybrid fillers for mechanical reinforcement of poly(vinyl alcohol) films

    NASA Astrophysics Data System (ADS)

    Ma, Hui-Ling; Zhang, Long; Zhang, Youwei; Wang, Shuojue; Sun, Chao; Yu, Hongyan; Zeng, Xinmiao; Zhai, Maolin

    2016-01-01

    Graphene/carbon nanotubes (G/CNTs) hybrid fillers were synthesized by γ-ray radiation reduction of graphene oxide (GO) in presence of CNTs. The obtained hybrid fillers with three-dimensional (3D) interconnected network structure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Poly(vinyl alcohol) (PVA) composite films with enhanced mechanical properties and thermal stability were subsequently prepared by solution blending of G/CNTs with PVA matrix. The tensile strength and Young's modulus of PVA composite films containing 1 wt% G/CNTs were measured to be 81.9 MPa and 3.9 GPa respectively, which were 56% and 33.6% higher than those of pure PVA. These substantial improvements could be attributed to the interconnected 3D structure of G/CNTs, homogeneous dispersion as well as the strong hydrogen-bonding interaction between G/CNTs and PVA macromolecular chains.

  8. Preparation and characterization of NaClO4 doped poly(vinyl alcohol)/sodium alginate composite electrolyte

    NASA Astrophysics Data System (ADS)

    Sheela, T.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Rathod, Sunil G.

    2013-02-01

    The 60:40 wt% poly(vinyl alcohol) (PVA)/sodium alginate blend doped with different concentrations of NaClO4 composite films were prepared by solution casting method. The prepared samples were characterized by FTIR, UV-Vis, DC and AC conductivity. The FTIR spectra confirms the complexation of NaClO4 with host polymer blend. From the UV-Vis spectra, the calculated optical band gap decreases from 5.2eV to 4.6eV. The frequency dependent dielectric constant decreases, and hence the dielectric loss and ac conductivity increases with doping level. The mechanical study shows the Young's modulus, tensile strength, stiffness were increases with the NaClO4 concentrations.

  9. Photoinduced crystallization of calcium carbonate from a homogeneous precursor solution in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-04-01

    Photoinduced crystallization of calcium carbonate (CaCO3) was demonstrated by the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) under alkaline conditions (pH 10). In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol %) was used as the precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. Thermogravimetric analysis of the obtained xerogels showed that increasing the UV irradiation time increased the amount of CaCO3 formed and the complete conversion of calcium ions to calcite was achieved after 50 min of UV irradiation. Furthermore, solid phase analyses suggested that nanometer-to-micron-sized calcite crystals were formed and dispersed in the obtained PVAPS matrix.

  10. Effect of γ irradiation on poly(vinyl alcohol) and bacterial cellulose composites used as packaging materials

    NASA Astrophysics Data System (ADS)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jipa, Iuliana; Dobre, Loredana; Zaharescu, Traian

    2013-03-01

    The aim of this paper is to present the influence of bacterial cellulose microfibrils and γ-radiation dose on poly(vinyl alcohol) (PVA)-bacterial cellulose (BC) composites. Two composite materials were obtained: the first one from PVA aqueous solution 4% and 5% wet bacterial cellulose and the second from the same PVA solution and 10% wet bacterial cellulose. In terms of PVA/dry BC ratios (w/w) for these films the ratios are 1/0.025 and 1/0.050. The obtained composite materials were characterized by infrared spectroscopy with Fourier transform (FT-IR) and UV-vis spectroscopy in order to evaluate the irradiation effect on their stability. The swelling behavior of the polymeric composites was also studied. The composite materials were compared with a film of pure PVA and a dry BC membrane.

  11. Study of enhanced red emission from Sm(Sal) 3Phen ternary complexes in Poly Vinyl Alcohol film

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Dwivedi, Y.; Rai, S. B.

    2010-09-01

    In the present work, dinuclear complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized with different concentrations of Samarium ion (Sm 3+) in Poly Vinyl Alcohol (PVA) polymer films and their structural and spectroscopic properties were investigated. Judd-Ofelt theory has been employed to estimate the several radiative parameters for SmCl 3 and Sm(Sal) 3Phen complex in PVA polymer film which are in fairly agreement between the experimental and the theoretical values supporting the J-O theory. Photoluminescence properties of the complex have been studied on 355 nm and 400 nm excitations in steady state as well as in time domain. On the basis of the UV-Vis absorption, FT-IR absorption, excitation, emission spectra and decay curves, spectroscopic properties of these films were studied and the photophysics involved was explained in terms of energy transfer and the RE encapsulation effect.

  12. Comparison of Chain Conformation of Poly(vinyl alcohol) in Solutions and Melts from Quantum Chemistry Based Molecular Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard; Han, Jie; Matsuda, Tsunetoshi; Yoon, Do; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    Confirmations of 2,4-dihydroxypentane (DHP), a model molecule for poly(vinyl alcohol), have been studied by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. QC calculations at the 6-311G MP2 level show the meso tt conformer to be lowest in energy followed by the racemic tg, due to intramolecular hydrogen bond between the hydroxy groups. The Dreiding force field has been modified to reproduce the QC conformer energies for DHP. MD simulations using this force field have been carried out for DHP molecules in the gas phase, melt, and CHCl3 and water solutions. Extensive intramolecular hydrogen bonding is observed for the gas phase and CHCl3 solution, but not for the melt or aqueous solution, Such a condensed phase effect due to intermolecular interactions results in a drastic change in chain conformations, in agreement with experiments.

  13. BOD biosensor based on the yeast Debaryomyces hansenii immobilized in poly(vinyl alcohol) modified by N-vinylpyrrolidone.

    PubMed

    Arlyapov, V A; Yudina, N Yu; Asulyan, L D; Alferov, S V; Alferov, V A; Reshetilov, A N

    2013-09-10

    An amperometric biosensor for assessing the biochemical oxygen demand (BOD) was formed by immobilizing Debaryomyces hansenii VKM Y-2482 yeast cells in poly(vinyl alcohol) modified by N-vinylpyrrolidone. Modification provided for a high sensitivity and stability of the bioreceptor. A high oxidative activity of the receptor element and the absence of any toxic effect of assayed compounds were shown for 34 substrates (alcohols, carbohydrates, carboxylic acids, amino acids, nitrophenols and surfactants) that may occur in wastewaters. Estimates of the measurement range and region of the linear dependence of signals on the BOD level, pH and temperature sensitivities, dependences of signals on concentrations of salts, stability, Michaelis kinetic constants and assay rates were obtained. The BOD values determined by the biosensor in assayed wastewater samples were shown to have a high correlation with those obtained by the standard dilution method. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  14. Effect of Salt Concentration on the Structure of Poly(Vinyl Alcohol) Cryogels Obtained from Aqueous Salt Solutions

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Zagorskaya, S. A.

    2015-03-01

    The degree of polymer crystallinity and water content on the surfaces and in the bulk of poly(vinyl alcohol) (PVA) cryogels prepared from aqueous salt solutions were determined as functions of KCl concentration using FTIR-ATR spectroscopy. It was found that the degree of PVA crystallinity increased with increasing KCl concentration and was much greater in the cryogel bulk than on its surfaces. Addition of salt at a concentration of 1.3 M increased the degree of polymer crystallinity on the cryogel surfaces by 1.6-2.3 times whereas the crystallinity in the bulk increased by 3.3-4 times. The cryogel water contents on the surfaces and in the bulk were approximately equal and were practically independent of the salt concentration.

  15. A new amperometric glucose biosensor based on one-step electrospun poly(vinyl alcohol)/chitosan nanofibers.

    PubMed

    Su, Xiaofang; Wei, Jianfei; Ren, Xiangling; Li, Linlin; Meng, Xianwei; Ren, Jun; Tang, Fangqiong

    2013-10-01

    In this work, a new glucose amperometric biosensor was developed by directly electrospinning poly(vinyl alcohol)/chitostan nanofibers on the surface of the platinum electrode, in which glucose oxidase (GOD) was effectively immobilized in nanofibers by encapsulation. After been cross-linked in glutaraldehyde vapor and modified with a thin nafion film, the nanofibers (PVA/chitosan/GOD)/nafion electrode was used for glucose amperometric measurements. The electrospun nanofibrous enzyme membrane served as a better sensing element than the casing one due to the unique properties of nanofibers such as the special three-dimensional network structure, large pores, high porosity, and large surface to volume ratios. The as-prepared biosensor showed a wide linear calibration range, low detection limit, and low apparent Michaelis-Menten constant in the glucose determination. The stability, reproducibility and anti-interference capability of biosensor were also presented. Furthermore, the new biosensor was successfully applied to detect glucose in human serum samples.

  16. Radiation preparation of drug carriers based polyacrylic acid (PAAc) using poly(vinyl pyrrolidone) (PVP) as a template polymer

    NASA Astrophysics Data System (ADS)

    Abd El-Rehim, H. A.; Hegazy, E. A.; Khalil, F. H.; Hamed, N. A.

    2007-01-01

    The present study deals with the radiation synthesis of stimuli response hydrophilic polymers from polyacrylic acid (PAAc). To maintain the property of PAAc and control the water swellibility for its application as a drug delivery system, radiation polymerization of AAc in the presence of poly(vinyl pyrrolidone) (PVP) as a template polymer was carried out. Characterization of the prepared PAA/PVP inter-polymer complex was investigated by determining gel content, swelling property, hydrogel microstructure and the release rate of caffeine as a model drug. The release rate of caffeine from the PAA/PVP inter-polymer complexes showed pH-dependency, and seemed to be mainly controlled by the dissolution rate of the complex above a p Ka of PAAc. The prepared inter-polymer complex could be used for application as drug carriers.

  17. Cell-compatible properties of calcium carbonates and hydroxyapatite deposited on ultrathin poly(vinyl alcohol)-coated polyethylene films.

    PubMed

    Serizawa, Takeshi; Tateishi, Taishi; Akashi, Mitsuru

    2003-01-01

    Poly(vinyl alcohol) (PVA) was coated onto polyethylene (PE) films by a repetitive adsorption and drying process, and then the PVA-coated PE films were alternately immersed into aqueous solutions of Ca2+ and CO3(2-) ions (alternate soaking cycles), to deposit calcium carbonate (CaCO3) onto the films. The PVA coating was essential for the CaCO3 deposition. The amount of CaCO3 deposited increased with an increasing number of cycles. Scanning electron microscopic observations and attenuated total reflection spectra revealed the presence of both calcite and aragonite as the crystal structures of CaCO3 on the film. L929 fibroblast cells adhered and proliferated on these CaCO3-deposited PE films, as well as the hydroxyapatite-coated PE films previously prepared. It was found that the PVA coating and the subsequent deposition of calcium salts on certain films facilitated cell compatibility.

  18. Design and simulation of a poly(vinyl alcohol)-bacterial cellulose nanocomposite mechanical aortic heart valve prosthesis.

    PubMed

    Mohammadi, H; Boughner, D; Millon, L E; Wan, W K

    2009-08-01

    In this study, a polymeric aortic heart valve made of poly(vinyl alcohol) (PVA)-bacterial cellulose (BC) nanocomposite is simulated and designed using a hyperelastic non-linear anisotropic material model. A novel nanocomposite biomaterial combination of 15 wt % PVA and 0.5 wt % BC is developed in this study. The mechanical properties of the synthesized PVA-BC are similar to those of the porcine heart valve in both the principal directions. To design the geometry of the leaflets an advance surfacing technique is employed. A Galerkin-based non-linear finite element method is applied to analyse the mechanical behaviour of the leaflet in the closing and opening phases under physiological conditions. The model used in this study can be implemented in mechanical models for any soft tissues such as articular cartilage, tendon, and ligament.

  19. Acrylonitrile-grafted poly(vinyl alcohol) copolymer as effective binder for high-voltage spinel positive electrode

    NASA Astrophysics Data System (ADS)

    Tanaka, Shinichi; Narutomi, Takuya; Suzuki, Shigeru; Nakao, Aiko; Oji, Hiroshi; Yabuuchi, Naoaki

    2017-08-01

    Acrylonitrile-grafted poly(vinyl alcohol) copolymer with a branched structure is synthesized and used as binder for a LiNi1/2Mn3/2O4 composite electrode. Electrode performances of composite electrodes with different binders are compared in Li cells at 50 °C. The branched copolymer has better coatability to active materials in comparison to a simple mixture of linear polymers and conventional PVdF as evidenced by hard X-ray photoelectron spectroscopy. Cyclability is effectively improved by using the branched copolymer at elevated temperatures because of high chemical stability of the coated polymer layer and formation of a protective layer on cycles. Moreover, excellent rate-capability is realized by applying the branched copolymer with high adhesive strength, and the composite electrode delivers 70 mAh g-1 of discharge capacity at a rate of 1280 mA g-1.

  20. Optical and morphological characterizations of pyronin dye-poly (vinyl alcohol) thin films formed on glass substrates

    SciTech Connect

    Meral, Kadem Arik, Mustafa Onganer, Yavuz

    2016-04-18

    Thin films of pyronin dye mixed with poly(vinyl alcohol) (PVA) on glass substrate were prepared by using spin-coating technique. The optical and morphological properties of the thin films were studied by UV-Vis., steady-state fluorescence spectroscopies and atomic force microscopy (AFM). The thin films on glass substrate were fabricated at various [PVA]/[dye] (P/D) ratios. Hence, the monomeric and H-aggregates thin films of pyronin dye mixed with PVA were formed as a function of the dye and PVA concentration. It was determined that while the monomeric thin films showed strong fluorescence, the formation of H-aggregates in the thin film caused to decreasing the fluorescence intensity. AFM studies demonstrated that the morphology of the thin film was drastically varied with changing the optical property of the thin film such as monomeric and H-aggregates thin films.

  1. Optical sensing of phenylalanine in urine via extraction with magnetic molecularly imprinted poly(ethylene-co-vinyl alcohol) nanoparticles

    NASA Astrophysics Data System (ADS)

    Hsu, Chung-Yi; Lee, Mei-Hwa; Thomas, James L.; Shih, Ching-Ping; Hung, Tzu-Lin; Whang, Thou-Jen; Lin, Hung-Yin

    2015-07-01

    Incorporation of superparamagnetic nanoparticles into molecularly imprinted polymers (MIPs) is useful for both bioseparations and for concentration and sensing of biomedically relevant target molecules in physiological fluids, through the application of a magnetic field. In this study, we combined the separation and concentration of a target (phenylalanine) in urine, using magnetic molecularly imprinted polymeric composite nanoparticles, with optical sensing, to improve assay sensitivity. This target is important as a catecholamine precursor, and as an important amino acid constituent of proteins. Poly(ethylene-co-vinyl alcohol)s were imprinted with target molecules, and showed a high imprinting effectiveness (target binding compared with binding to non-imprinted polymer particles.) Fluorescence spectrophotometry was used to measure binding of the target, and also binding of possible interfering compounds. These measurements suggest that functional groups on phenylalanine dominate the selectivity of the synthesized MIPs. Finally, the composite nanoparticles were used to separate and sense the target molecule in urine by Raman scattering microscopy.

  2. Investigation of the Ionic conductivity and dielectric measurements of poly (N-vinyl pyrrolidone)-sulfamic acid polymer complexes

    NASA Astrophysics Data System (ADS)

    Daries Bella, R. S.; Karthickprabhu, S.; Maheswaran, A.; Amibika, C.; Hirankumar, G.; Devaraj, Premanand

    2015-02-01

    Polymer electrolyte complexes of poly (N-vinyl pyrrolidone) (PVP)-sulfamic acid (NH2SO3H) were prepared by a familiar solution casting method with different molar concentrations of PVP and sulfamic acid. The interaction between PVP and NH2SO3H was confirmed by Fourier transform infrared spectroscopy analysis. Laser microscopy analysis was used to study the surface morphology of the polymer complexes. The glass transition temperature (Tg) and the melting temperature (Tm) of polymer complexes were computed from Differential scanning calorimetric studies. AC impedance spectroscopic measurements revealed that the polymer complex, 97 mol% PVP-3 mol% NH2SO3H shows higher ionic conductivity with two different activation energies above and below the glass transition temperature (Tg). Dielectric studies confirmed that the dc conduction mechanism has dominated in the polymer complexes. The value of power law exponent (n) confirmed the translational motion of ions from one site to another vacant site in these complexes.

  3. The Gelation of Poly(Vinyl Alcohol) with Na2B4O7 10H2O: Killing Slime

    NASA Astrophysics Data System (ADS)

    McLaughlin, K. W.; Wyffels, N. K.; Jentz, A. B.; Keenan, M. V.

    1997-01-01

    The gelation of poly(vinyl alcohol), PVA, with sodium tetraborate decahydrate (borax) to produce "slime" is a popular chemistry demonstration (1). Since the borate serves to cross-link the PVA, the degree of cross-linking can be varied by changing the borate concentration (2). One way of changing the concentration of borate available to hold the PVA chains together is to "disable" the borate by protonation with a strong acid (3, 4). The titration of slime with sulfuric acid (eq 1) allows students to examine the relationship between cross-linking, viscosity, and the onset of gelation. This modification to a popular chemistry demonstration produces an interesting chemistry laboratory experiment designed to introduce students to the relationship between molecular structure and the bulk properties of macromolecules.

  4. Solvothermal synthesis of uniform bismuth nanospheres using poly(N-vinyl-2-pyrrolidone) as a reducing agent

    PubMed Central

    2011-01-01

    Uniform bismuth nanospheres were successfully prepared from bismuth nitrate in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) by solvothermal process. The product was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray. PVP plays a critical role both as a reducing agent and a capping agent in the formation of bismuth nanospheres. Shape and size of bismuth nanospheres could be tuned by changing the employed PVP/bismuth salt ratio. It was also found the solvent had an effect on the morphologies of bismuth nanomaterials. The possible formation and growth mechanism of bismuth nanospheres were also discussed and proposed to explain the reduction step. PMID:21711606

  5. Poly vinyl acetate and ammonio methacrylate copolymer as unconventional polymer blends increase the mechanical robustness of HPMC matrix tablets.

    PubMed

    Ali, R; Dashevsky, A; Bodmeier, R

    2017-01-10

    The objective was to investigate poly vinyl acetate (Kollicoat(®) SR 30 D) and ammonio methacrylate copolymer (Eudragit(®) RL 30 D) blends as coatings to increase the mechanical robustness of hydroxypropyl methylcellulose (HPMC) matrix tablets. Poly vinyl acetate (Kollicoat(®) SR 30 D - KSR) was selected for its flexibility and ammonio methacrylate copolymer (Eudragit(®) RL 30 D - ERL) because of its high permeability. Films based on KSR:ERL blends were prepared by casting or spraying aqueous dispersions of these polymers and were characterized by water uptake, dry mass loss and mechanical properties. KSR:ERL blends were investigated as coating materials to improve the robustness, mechanical strength and drug release from the HPMC matrix tablets containing propranolol HCl, caffeine and carbamazepine as model drugs. Both HPMC and the polymer coating affected the propranolol release. The release and the mechanical properties could be easily adjusted by varying the polymer blend ratio. The flexibility increased with increasing KSR content. At an 8% w/w coating level, a force of 3.2N was required to rupture the coating of the swollen tablet after 16h in the release medium; the coated tablets were thus robust to withstand gastrointestinal forces. The coating level (6%-10%, w/w) and dissolution agitation rate (50rpm to 150rpm) had no effect on the drug release. The water-insoluble carbamazepine was not released from the coated tablets as HPMC erosion, which is necessary for the release of a poorly water-soluble drug was hindered by the coating. The release of the water-soluble propranolol increased with increasing drug content and decreased with increasing HPMC content.

  6. Fabrication of a tunable glucose biosensor based on zinc oxide/chitosan-graft-poly(vinyl alcohol) core-shell nanocomposite.

    PubMed

    Shukla, S K; Deshpande, Swapneel R; Shukla, Sudheesh K; Tiwari, Ashutosh

    2012-09-15

    A potentiometrically tuned-glucose biosensor was fabricated using core-shell nanocomposite based on zinc oxide encapsulated chitosan-graft-poly(vinyl alcohol) (ZnO/CHIT-g-PVAL). In a typical experiment, ZnO/CHIT-g-PVAL core-shell nanocomposite containing <20 nm ZnO nanoparticles was synthesized using wet-chemical method. The glucose responsive bio-electrode, i.e., glucose oxidase/ZnO/chitosan-graft-poly(vinyl alcohol) (GOD/ZnO/CHIT-g-PVAL/ITO) was obtained by immobilization of glucose oxidase (GOD) onto the electrode made of resulting ZnO core-shell nanocomposite coated on the indium-tin oxide (ITO) glass substrate. The ZnO/CHIT-g-PVAL/ITO and GOD/ZnO/CHIT-g-PVAL electrodes were characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), whereas ZnO/CHIT-g-PVAL size of core-shell nanoparticles were measured using transmission electron microscopy (TEM). The electrostatic interaction between GOD and ZnO/CHIT-g-PVAL provided the resulting tuned enzyme electrode with a high degree of enzyme immobilization and excellent lifetime stability. The response studies were carried out as a function of glucose concentration with potentiometric measurement. The GOD/ZnO/CHIT-g-PVAL/ITO bioelectrode has showed a linear potential response to the glucose concentration ranging from 2 μM to 1.2mM. The glucose biosensor exhibited a fast surface-controlled redox biochemistry with a detection limit of 0.2 μM, a sensitivity of >0.04 V/μM and a response time of three sec. ZnO/CHIT-g-PVAL core-shell nanocomposite could be a promising nanomaterials for a range of enzymic biosensors. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. catena-Poly[[diaqua­dibromidoman­ganese(III)]-μ-pyridine-2-carboxyl­ato

    PubMed Central

    Kim, Nam-Ho; Ha, Kwang

    2009-01-01

    The asymmetric unit of the title compound, [MnBr2(C6H4NO2)(H2O)2]n, contains one monomeric unit of the neutral linear coordination polymer. The Mn3+ ions are bridged by anionic pyridine-2-carboxyl­ate (pic) ligands, thereby forming a chain-like structure along the c axis, and are six-coordinated in a distorted octa­hedral environment by two O atoms of the two different carboxyl­ate groups, two O atoms of two water mol­ecules and two Br atoms. The complex displays inter­molecular O—H⋯Br, O—H⋯N, O—H⋯O, C—H⋯O and C—H⋯Br hydrogen bonding. There may also be inter­molecular π–π inter­actions between adjacent pyridine rings, with a centroid–centroid distance of 3.993 (8) Å. PMID:21583426

  8. Polyvinyl pyridine microspheres

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

    1980-01-01

    Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

  9. Polyvinyl pyridine microspheres

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

    1979-01-01

    Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

  10. Poly(vinyl alcohol) gel sublayers for reverse osmosis membranes. I. Insolubilization by acid-catalyzed dehydration

    SciTech Connect

    Immelman, E.; Sanderson, R.D.; Jacobs, E.P.; Van Reenan, A.J. . Inst. of Polymer Science)

    1993-11-10

    Both flat-sheet and tubular composite reverse osmosis (RO) membranes were prepared by depositing aqueous solutions of poly(vinyl alcohol) (PVA) and a dehydration catalyst on asymmetric poly(arylether sulfone) (PES) substrate membranes. The PVA coatings were insolubilized by heat treatment to create stable hydrophilic gel-layer membranes. The influence of variables such as PVA concentration, catalyst concentration, curing time, and curing temperature was investigated. It was shown that a simple manipulation of one or two variables could lead to membranes with widely differing salt retention and water permeability characteristics. The insolubilized PVA coatings were intended to serve as hydrophilic gel sublayers on which ultra thin salt-retention barriers could ultimately be formed by interfacial polycondensation. For this purpose, high-flux gel layers were required, whereas salt-retention capabilities were not regarded as important. However, the promising salt retentions obtained as 2 MPa (up to 85% NaCl retention and 92% MgSO[sub 4] retention) showed that some of these PES-PVA composite membranes could function as medium-retention, medium-flux RO membranes, even in the absence of an interfacially formed salt-retention barrier.

  11. Solid state solubility of miconazole in poly[(ethylene glycol)-g-vinyl alcohol] using hot-melt extrusion.

    PubMed

    Litvinov, V M; Guns, S; Adriaensens, P; Scholtens, B J R; Quaedflieg, M P; Carleer, R; Van den Mooter, G

    2012-10-01

    The use of hot-melt extrusion for preparing homogeneous API-excipient mixtures is studied for miconazole-PEG-g-PVA [poly(ethylene glycol)-poly(vinyl alcohol) graft copolymer] solid dispersions with a 5 cm(3) table-top, twin-screw corotating microcompounder (DSM Xplore). Phase behavior of PEG-g-PVA, miscibility of miconazole in PEG-g-PVA and the partitioning of miconazole between PEG and PVA amorphous phases are characterized using a combination of modulated DSC, XRPD, and solid-state (1)H and (13)C NMR methods. The (1)H NMR transverse magnetization relaxation (T(2) relaxation) method is used to analyze the phase composition and molecular mobility of the copolymer. The T(2) relaxation decay of pure PEG-g-PVA can be described by four T(2) relaxation components in the temperature range studied. PVA crystallinity is not largely affected by hot-melt extrusion and the presence of the drug. Miconazole preferably resides in the PEG amorphous phase, and its molecules are well dispersed in the PEG-g-PVA matrix using hot-melt extrusion mixing. Miconazole forms amorphous nanoclusters whose average size equals approximately 1.6 nm, indicating solid solution formation (molecular level dispersion) of the drug in the polymer.

  12. Designed chain architecture for enhanced migration resistance and property preservation in poly(vinyl chloride)/polyester blends.

    PubMed

    Lindström, Annika; Hakkarainen, Minna

    2007-04-01

    Blends of poly(vinyl chloride) (PVC) and poly(butylene adipate) (PBA) with varying degrees of branching were analyzed with respect to migration resistance during aging in water, preservation of material properties, and thermal stability. Gas chromatography-mass spectrometry, water absorption, weight loss, thermogravimetric analysis, Fourier transform infrared spectroscopy, contact angle, tensile testing, and differential scanning calorimetry were used to analyze the blends before and after aging in water for 6 weeks. Films plasticized with slightly branched polyester maintained their material and mechanical properties best during aging. High degree of branching was accompanied by poor miscibility, increased hydrophilicity, and polydispersity, and highly branched PBA was not favorable as a plasticizer. Strong intermolecular interactions reduced the water absorption and increased the migration resistance of the blends. Polymeric plasticizers with no, low, or moderate degree of branching improved the thermal stability of films compared to films plasticized with a traditional phthalate plasticizer. Proper design of plasticizer architecture led, thus, to improved migration resistance, long-term properties, and thermal stability in PVC/polyester blends.

  13. Ultrasonic Velocity, Viscosity and Refractive Index Investigation on Interacting Blend Solutions of PAA (Poly Acrylic Acid) and PVA (Poly Vinyl Alcohol) in Solvent DMSO (Di methyl Sulphoxide)

    NASA Astrophysics Data System (ADS)

    Nagamani, Chakrala

    2010-11-01

    The present study provides a great insight into the major new research areas like Plasma research (which is yielding a greater understanding of the universe) and Nano Technology Research (which provides many practical uses like Drug Delivery System). The Ultrasonic Velocities, Viscosities and Refractive indices of Poly (Acrylic Acid) and Poly (Vinyl Alcohol) blends in DMSO solutions have been measured over a wide range of composition, concentration and at different temperatures. The variation of Ultrasonic Velocity, derived acoustical parameters, adiabatic compressibility, acoustic impedance, Rao number, molar compressibility and relaxation strength with composition of blend solution was found not linear. This non-linearity has been attributed to incompatibility in conformity with the earlier findings. This behavior was confirmed by Viscometric and interaction parameters studies, as well as by investigation of Refractive index studies. These investigations offer an entirely new and simple approach to the study of the compatibility of polymer blends which is in general obtained by sophisticated techniques of thermal dynamic mechanical and electron microscopic analysis.

  14. Definition and validation of operating equations for poly(vinyl alcohol)-poly(lactide-co-glycolide) microfiltration membrane-scaffold bioreactors

    PubMed Central

    Shipley, RJ; Waters, SL; Ellis, MJ

    2010-01-01

    The aim of this work is to provide operating data for biodegradable hollow fiber membrane bioreactors. The physicochemical cell culture environment can be controlled with the permeate flowrate, so this aim necessitates the provision of operating equations that enable end-users to set the pressures and feed flowrates to obtain their desired culture environment. In this paper, theoretical expressions for the pure water retentate and permeate flowrates, derived using lubrication theory, are compared against experimental data for a single fiber poly(vinyl alcohol)–poly(lactide-co-glycolide) crossflow module to give values for the membrane permeability and slip. Analysis of the width of the boundary layer region where slip effects are important, together with the sensitivity of the retentate and permeate equations to the slip parameter, show that slip is insignificant for these membranes, which have a mean pore diameter of 1.1 µm. The experimental data is used to determine a membrane permeability, of k = 1.86 × 10−16 m2, and to validate the model. It was concluded that the operating equation that relates the permeate to feed ratio, c, lumen inlet flowrate, Ql,in, lumen outlet pressure, P1, and ECS outlet pressure, P0, is1 where A and B are constants that depend on the membrane permeability and geometry (and are given explicitly). Finally, two worked examples are presented to demonstrate how a tissue engineer can use Equation 1 to specify operating conditions for their bioreactor. PMID:20641054

  15. Synergistic and competitive aspects of the adsorption of poly(ethylene glycol) and poly(vinyl alcohol) onto Na-bentonite.

    PubMed

    Clegg, Francis; Breen, Chris; Khairuddin

    2014-11-20

    The competitive adsorption of poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVOH) onto Na-bentonite has been assessed quantitatively. Particular emphasis was focused on the amount of organic located within the bentonite interlayer and any subsequent effects on the extent of layer expansion. The individual isotherms showed strong adsorption for both PVOH and PEG at amounts lower than the quantities required to produce a fully loaded bilayer (0.33 g of PVOH/g of clay) and single layered structures (0.10 g of PEG/g of clay), respectively. Above these concentrations, the incremental amounts adsorbed were smaller, and the concentration of adsorbates in solution gradually increased. Na-bentonite adsorbed more PVOH than PEG at any given concentration. In the competitive study, the amount of PVOH adsorbed was enhanced in the presence of PEG (0.10 and 0.30 g/g of clay), but less PEG was adsorbed. At low loadings of PVOH (0.02-0.10 g/g of clay), the amount of adsorbed PEG was increased but at higher PVOH levels PEG adsorption was reduced. The XRD data showed stepped changes in the d-spacing as the adsorbed amounts of both PEG and PVOH increased. The PEG-bentonite samples did not expand beyond a bilayer structure (18 Å), but the XRD data for PVOH-treated samples indicated the formation of multilayer structures (d ≥ 44 Å).

  16. Inorganic-organic polymer electrolytes based on poly(vinyl alcohol) and borane/poly(ethylene glycol) monomethyl ether for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Aydın, Hamide; Şenel, Mehmet; Erdemi, Hamit; Baykal, Abdülhadi; Tülü, Metin; Ata, Ali; Bozkurt, Ayhan

    In this study, poly(vinyl alcohol) (PVA) was modified with poly(ethylene glycol) monomethyl ether (PEGME) using borane-tetrahydrofuran (BH 3/THF) complex. Molecular weights of both PVA and PEGME were varied prior to reaction. Boron containing comb-branched copolymers were produced and abbreviated as PVA1PEGMEX and PVA2PEGMEX. Then polymer electrolytes were successfully prepared by doping of the host matrix with CF 3SO 3Li at several stoichiomeric ratios with respect to EO to Li. The materials were characterized via nuclear magnetic resonance (1H NMR and 11B NMR), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG) and differential scanning calorimeter (DSC). The ionic conductivity of these novel polymer electrolytes were studied by dielectric-impedance spectroscopy. Li-ion conductivity of these polymer electrolytes depends on the length of the side units as well as the doping ratio. Such electrolytes possess satisfactory ambient temperature ionic conductivity (>10 -4 S cm -1). Cyclic voltammetry results illustrated that the electrochemical stability domain extends over 4 V.

  17. Thermally and Electrically Triggered Triple-Shape Memory Behavior of Poly(vinyl acetate)/Poly(lactic acid) Due to Graphene-Induced Phase Separation.

    PubMed

    Sabzi, Mohammad; Babaahmadi, Masoud; Rahnama, Mohammadreza

    2017-07-19

    This work aimed to develop a facile and broadly applicable method for fabricating multistimuli responsive triple-shape memory polymers (SMPs). Hence, herein the SMPs were prepared through the simple physical blending of two commercially available biopolymers, poly(lactic acid) (PLA) and poly(vinyl acetate) (PVAc), in the presence of robust and conductive graphene nanoplatelets. Interestingly, atomic force microscopy observations and thermal analyses revealed that the presence of nanofillers led to phase separation and appearance of two well-separated transition temperatures in the blend of these two miscible polymers. Consequently, shape memory results showed that the unfilled blend of PLA/PVAc with a single thermal transition can only show moderate heat triggered dual-shape memory behavior. While, PLA/PVAc/graphene nanocomposite blends demonstrated excellent thermally and electrically actuated triple-shape memory effects besides their remarkable dual-shape memory behavior. In addition, electrical conductivity of the blend was enhanced by ∼14 orders of magnitude in the presence of graphene. More interestingly, electroactive shape recovery experiments exhibited that depending on the applied voltage, temporary shapes in each region of sample can be either individually or simultaneously recovered.

  18. Surface characterization of poly(vinyl chloride) urinary catheters functionalized with acrylic acid and poly(ethylene glycol) methacrylate using gamma-radiation

    NASA Astrophysics Data System (ADS)

    Islas, Luisa; Ruiz, Juan-Carlos; Muñoz-Muñoz, Franklin; Isoshima, Takashi; Burillo, Guillermina

    2016-10-01

    Poly(vinyl chloride) (PVC) urinary catheters were modified with either a single or binary graft of acrylic acid (AAc) and/or poly(ethylene glycol) methacrylate (PEGMA) using gamma-radiation from 60Co to obtain PVC-g-AAc, PVC-g-PEGMA, [PVC-g-AAc]-g-PEGMA, and [PVC-g-PEGMA]-g-AAc copolymers. The outer and inner surfaces of the modified catheters were characterized using scanning electron microscopy (SEM), confocal laser microscopy (CLM) and X-ray photoelectron spectroscopy (XPS). The XPS analyses, by examining the correlation between the variation of the C1s and O1s content at the catheter's surface, revealed that the catheter's surfaces were successfully grafted with the chosen compounds, with those that were binary grafted showing a slightly more covered surface as was evidenced by the disappearance of PVC's Cl peak. The SEM and CLM analyses revealed that catheters that had been grafted with PEGMA had a rougher outer surface as compared to those that had only been grafted with AAc. In addition, these imaging techniques showed that the inner surface of the singly grafted catheters, whether they had been grafted with AAc or PEGMA, retained some smoothness at the analyzed grafting percentages, while the binary grafted catheters showed many protuberances and greater roughness on both outer and inner surfaces.

  19. Failure processes in some polymers: (A) slow crack growth in poly(vinyl chloride) and (B) breakup of poly(ethylene) nanolayers

    NASA Astrophysics Data System (ADS)

    Bernal Lara, Teresa Elizabeth

    Failure processes in poly(vinyl chloride) and high density poly(ethylene) were studied. The effect of impact modification and molecular weight on slow crack growth in poly(vinyl chloride) (PVC) was examined in order to test a methodology for predicting long-term creep fracture from short-term tension-tension fatigue tests. In all the PVC compounds studied, the crack propagated in a stepwise manner through a crack tip craze zone. Step length was analyzed in terms of the Dugdale model for a crack tip plastic zone. The overall crack growth rate in fatigue and creep followed the conventional Paris power law with the same exponent 2.7, da/dt = AfDK2.7I and da/dt = BK2.7I , respectively. Crack growth rate was modeled as the product of a creep contribution that depended only on the maximum stress intensity factor and a fatigue contribution that depended on strain rate da/dt = BfK2.7I,max(1+C 3˙) , where C is a coefficient defining the strain rate sensitivity. A linear correlation allowed for extrapolation of the creep prefactor Bf from fatigue data. Decreasing molecular weight increased Bf and decreased C. Impact modification decreased Bf but had no effect on C. The crystallization and thermal stability of high density polyethylene (HDPE) when confined to very thin layers was examined. Films with hundreds of thin HDPE layers separated by thicker amorphous PS layers were fabricated by "forced assembly" using layer-multiplying coextrusion. Characterization of the films revealed changes in the structure and properties of the HDPE layers as the thickness decreased from the microscale (>100 nm) to the nanoscale (<100 nm). It is inherent to the concept of "forced assembly" that nanolayers may not be stable when they are heated into the melt state. Heating films above the melting temperature of HDPE resulted in fractionated crystallization as indicated by two crystallization exotherms in thermograms. The lower temperature exotherm at 80°C was identified with homogeneous

  20. Poly[di-μ(2)-aqua-μ(5)-(pyridine-2,6-dicarboxyl-ato)-μ(3)-(pyridine-2,6-dicarboxyl-ato)-cobalt(II)disodium].

    PubMed

    Boyko, Alexander N; Golenya, Irina A; Izotova, Yulia A; Haukka, Matti; Prisyazhnaya, Elena V

    2011-12-01

    In the title compound, [CoNa(2)(C(7)H(3)NO(4))(2)(H(2)O)(2)](n), the Co(II) atom is coordinated by two pyridine N atoms and four carboxyl-ate O atoms from two doubly deprotonated pyridine-2,6-dicarboxyl-ate ligands in a distorted octa-hedral geometry. One Na(+) cation is coordinated by three carboxyl-ate O atoms and two water mol-ecules and the other is coordinated by five carboxyl-ate O atoms and two water mol-ecules in an irregular geometry. The bis-(pyridine-2,6-dicarboxyl-ato)cobalt complex units are connected by Na(+) cations and bridging water mol-ecules into a three-dimensional coordination network. O-H⋯O hydrogen bonds are formed between the water mol-ecules and the carboxyl-ate O atoms.

  1. Poly(vinyl alcohol) as a water protecting agent for silver nanoparticles: the role of polymer size and structure.

    PubMed

    Kyrychenko, Alexander; Pasko, Dmitry A; Kalugin, Oleg N

    2017-02-20

    Chemical modification of silver nanoparticles (AgNPs) with a stabilizing agent, such as poly(vinyl alcohol) (PVA), plays an important role in shape-controlled seeded-growth and colloidal stability. However, theoretical aspects of the stabilizing mechanism of PVA are still poorly understood. To gain a better understanding of the role of PVA in water protecting effects for silver nanoparticles, we developed an atomistic model of a AgNP grafted with single-chain PVA of various lengths. Our model, designed for classical molecular dynamics (MD) simulations, approximates the AgNP as a quasi-spherical silver nanocrystal with 3.9 nm diameter and uses a united-atom representation for PVA with its polymer chain length varying from 220 up to 1540 repeating units. We found that PVA adsorbs onto the AgNP surface through multiple non-covalent interactions, among which non-covalent bonding of the hydroxyl groups plays a key role. The analysis of adsorption isotherms by using the Hill, Scatchard, and McGhee & von Hippel models exhibits evidence for positive binding cooperativity with the cooperativity parameter varying from 1.55 to 2.12. Our results indicate that the size of the PVA polymer rather than its structure plays a crucial role in providing water protecting effects for the AgNP core, varying from 40% up to 91%. The water-protecting efficiency was well approximated by the Langmuir-Freundlich equation, allowing us to predict that the saturated coverage of the nanoparticle of a given diameter of 3.9 nm should occur when the PVA molecular weight approaches 115 kDa, which corresponds to the number of vinyl alcohol monomers being equal to 3100 units.

  2. Photo-triggered release from liposomes without membrane solubilization, based on binding to poly(vinyl alcohol) carrying a malachite green moiety.

    PubMed

    Uda, Ryoko M; Kato, Yutaka; Takei, Michiko

    2016-10-01

    When working with liposomes analogous to cell membranes, it is important to develop substrates that can regulate interactions with the liposome surface in response to light. We achieved a photo-triggered release from liposomes by using a copolymer of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). Although PVAMG is a neutral polymer under dark conditions, it is photoionized upon exposure to UV light, resulting in the formation of a cationic site for binding to liposomes with a negatively charged surface. Under UV irradiation, PVAMG showed effective interaction with liposomes, releasing the encapsulated compound; however, this release was negligible under dark conditions. The poly(vinyl alcohol) moiety of PVAMG played an important role in the photo-triggered release. This release was caused by membrane destabilization without lipid solubilization. We also investigated different aspects of liposome/PVAMG interactions, including PVAMG-induced fusion between the liposomes and the change in the liposome morphologies.

  3. Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via UV-induced graft polymerization of N-vinyl pyrrolidone.

    PubMed

    Luan, Shifang; Zhao, Jie; Yang, Huawei; Shi, Hengchong; Jin, Jing; Li, Xiaomeng; Liu, Jingchuan; Wang, Jianwei; Yin, Jinghua; Stagnaro, Paola

    2012-05-01

    Poly(N-vinyl pyrrolidone) (PNVP) was covalently grafted onto the surface of biomedical poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer via a technique of UV-induced graft polymerization combined with plasma pre-treatment. The surface graft polymerization of N-vinyl pyrrolidone (NVP) was confirmed by ATR-FTIR and XPS. Effect of the parameters of graft polymerization, i.e., the initiator concentration, the UV irradiation time and the monomer concentration on the grafting density was investigated. The morphology and the wettability of the PNVP-modified surfaces were characterized by AFM and DSA, respectively. Protein adsorption and platelet adhesion were obviously suppressed after PNVP was grafted onto the SEBS substrates. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Field and laboratory determination of a poly(vinyl/vinylidene chloride) additive in brick mortar.

    PubMed

    Law, S L; Newman, J H; Ptak, F L

    1990-02-01

    A polymerized vinyl/vinylidene chloride additive, used in brick mortar during the 60s and 70s, is detected at the building site by the field method, which employs a commercially available chloride test strip. The field test results can then be verified by the laboratory methods. In one method, total chlorine in the mortar is determined by an oxygen-bomb method and the additive chloride is determined by difference after water-soluble chlorides have been determined on a separate sample. In the second method, the polymerized additive is extracted directly from the mortar with tetrahydrofuran (THF). The difference in weight before and after extraction of the additive gives the weight of additive in the mortar. Evaporation of the THF from the extract leaves a thin film of the polymer, which gives an infrared "fingerprint" spectrum characteristic of the additive polymer.

  5. Using poly([1-vinyl-3-hexylimidazolium] [bis(trifluoromethylsulfonyl)imide]) to adsorb bio-ethanol from a Chamaecyparis obtuse leaves fermentation broth.

    PubMed

    Tang, Baokun; Bi, Wentao; Row, Kyung Ho

    2013-06-01

    Poly([1-vinyl-3-hexylimidazolium] [bis(trifluoromethylsulfonyl)imide]) (poly([VHIM][Tf2N])) was assessed for its ability to adsorb bio-ethanol from Chamaecyparis obtuse leaves fermentation broths. Poly([VHIM][Tf2N]) was prepared by poly([VHIM][Br]) ion exchange with Li(Tf2N). Poly([VHIM][Br]) was obtained using a thermal-initiated polymerization method. The factors affecting the adsorption capacity of poly([VHIM][Tf2N]), such as the initial concentration of bio-ethanol in the fermentation broth, adsorption temperature and dosage of the adsorbent, as well as the adsorption kinetics and equilibrium of poly([VHIM][Tf2N]) were investigated. The Langmuir, Freundlich and Temkin isotherms used to describe the adsorption of bio-ethanol on the adsorbent showed good correlation coefficients of 0.97, 0.96 and 0.98, respectively. A comparison of the separation factors for ethanol/water, ethanol/glucose and ethanol/xylose revealed poly([VHIM][Tf2N]) to have preferential selectivity for bio-ethanol. Compared to activated carbon, poly([VHIM][Tf2N]) exhibited higher adsorption capacity for bio-ethanol under the same adsorption conditions. The adsorbent could be used for 5 cycles with good efficiency, highlighting its reusability as an adsorbent. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Structural characterization of hydrated poly(aspartic acid) sodium and poly(aspartic acid) sodium/poly(vinyl alcohol) blends by high-resolution solid-state 23Na NMR

    NASA Astrophysics Data System (ADS)

    Wang, P.; Ando, I.

    1999-09-01

    The structure of hydrated poly(aspartic acid) sodium (PAANa) and in blended PAANa, which was blended with poly(vinyl alcohol) (PVA), is characterized by means of high-resolution solid-state 23Na NMR. There are two peaks in dried pure PAANa, which are assigned to associated ions (about -16 ppm) and isolated ions or end group ions of PAANa (7.2 ppm), respectively. With an increase in hydration, the 23Na chemical shifts of these two peaks are changed to tend toward 0 ppm, and the line width at half the height of the 23Na resonance decreases. In contrast, in the blended samples, the 23Na resonance shapes and chemical shift values are significantly changed depending on the ratio of the PAANa/PVA blends and the temperature. On the basis of these experimental results, the structure of the blends was elucidated.

  7. Discrimination of poly(vinyl chloride) samples with different plasticizers and prediction of plasticizer contents in poly(vinyl chloride) using near-infrared spectroscopy and neural-network analysis.

    PubMed

    Saeki, Kazumitsu; Funatsu, Kimito; Tanabe, Kazutoshi

    2003-02-01

    In the recycling of poly(vinyl chloride) (PVC), it is required to discriminate every plasticizer for quality control. For this purpose, the near-infrared spectra were measured for 41 kinds of PVC samples with different plasticizers (DINP, DOP, DOA, TOTM and Polyester) and different plasticizer contents (0-49%). A neural-network analysis was applied to the near-infrared spectra pretreated by second-derivative processing. They were discriminated from one another. The neural-network analysis also allowed us to propose a calibration model which predicts the contents of plasticizers in PVC. The correlation coefficient (R) and the root-mean-square error of prediction (RMSEP) for the DINP calibration model were found to be 0.999 and 0.41 wt%, respectively. In comparison, a partial least-squares regression analysis was carried out. The R and RMSEP of the DINP calibration model were calculated to be 0.993 and 1.27 wt%, respectively. It is found that a near-infrared spectra measurement combined with a neural-network analysis is useful for plastic recycling.

  8. Spectral photosensitization of optical anisotropy in poly(vinyl cinnamate) solid films

    NASA Astrophysics Data System (ADS)

    Kozenkov, V. M.; Spakhov, A. A.; Belyaev, V. V.; Chausov, D. N.; Chausova, O. V.; Chigrinov, V. G.

    2017-06-01

    We observed possibilities and properties of sensitized photo induced optical anisotropy formation in amorphous poly (vynyl-cinnamate) films (PVCi) and its derivant poly (vynyl-4-methoxy-cinnamate) (PVMCi) under polarized light, including the one which is not absorbed by the supermolecules of the polymeric material. The effect of the induced optical anisotropy involves transferring the energy of electronic excitation from the donor molecules (Michler’s ketone or 2-benzoyl-methylene-3, methyl-β-naphthosol) to the scavenger’s molecules - PVCi or PVMCi) and photo-topochemical ring formation of cinnamate units in polymeric supermolecules. The discovered photo-induced anisotropy in solid PVCi and PVMCi films provides sensitized photo orientation of low-molecular thermotropic liquid crystals.

  9. Spectrometric measurements and DFT studies on new complex of copper (II) with 2-((E)-9-ethyl-3-(2-(6-(4-methylpyridin-2-yl)pyridin-3-yl)vinyl)-9H-carbazole

    NASA Astrophysics Data System (ADS)

    Zhang, Haoyang; Hu, Jie; Zhao, Jianying; Zhang, Yu

    2016-11-01

    The molecular structure of a new complex of copper (II) with (E)-9-ethyl-3-(2-(6-(4-methylpyridin-2-yl)pyridin-3-yl)vinyl)-9H-carbazole ([Cu2(emppc)2Cl2]Cl2) was optimized with B3LYP/LanL2DZ, PBE1PBE/LanL2DZ and M062X/LanL2DZ theoretical level. The ligand, (E)-9-ethyl-3-(2-(6-(4-methylpyridin-2-yl)pyridin-3-yl)vinyl)-9H-carbazole (emppc), binds to Cu(II) ions with a bi-dentate mode, two Cl- serve as bridging ligand, each Cu(II) ion has a highly distorted tetrahedron coordination geometry. With M062X/LanL2DZ theoretical level, the calculated interaction energies of Cu(II) with coordination atoms N are between 183.3-200.0 kJ mol- 1 for α spin and 319.4-324.9 kJ mol- 1 for β spin, and interaction energies of Cu(II) with coordination atoms Cl atom are 248.0-252.4 kJ mol- 1 for α spin and 332.6-333.6 kJ mol- 1 for β spin. The experimental Fourier transform infrared spectrum was assigned. The calculated IR based on B3LYP/LanL2DZ, PBE1PBE/LanL2DZ and M062X/LanL2DZ methods were performed and compared with experimental results. The UV-Vis experimental spectra of [Cu2(emppc)2Cl2]Cl2 was measured in methanol solution. The calculated electronic spectrum was performed with TD/M062X and PCM-TD/M062X methods with LanL2DZ basis set. The nature bond orbital analysis and temperature dependence of the thermodynamic properties were calculated with the same methods.

  10. Synthesis of a New Titanate Coupling Agent for the Modification of Calcium Sulfate Whisker in Poly(Vinyl Chloride) Composite

    PubMed Central

    Yuan, Wenjin; Lu, Yunhua; Xu, Shiai

    2016-01-01

    A new titanate coupling agent synthesized from polyethylene glycol (PEG), isooctyl alcohol, and phosphorus pentoxide (P2O5) was used for the modification of calcium sulfate whiskers (CSWs) and the preparation of high-performance CSW/poly(vinyl chloride) (PVC) composites. The titanate coupling agent (sTi) and the modified CSWs (sTi–CSW) were characterized by Fourier transform infrared (FTIR) spectroscopy, and the mechanical, dynamic mechanical, and heat resistant properties and thermostability of sTi–CSW/PVC and CSW/PVC composites were compared. The results show that sTi–CSW/PVC composite with 10 wt. % whisker content has the best performance, and its tensile strength, Young’s modulus, elongation at break, break strength, and impact strength are 67.2 MPa, 1926 MPa, 233%, 51.1 MPa, and 12.75 KJ·m−2, with an increase of 20.9%, 11.5%, 145.3%, 24.6%, and 65.4% compared to that of CSW/PVC composite at the same whisker content. As the whisker content increases, the storage modulus increases, the Vicat softening temperature decreases slightly, and the glass transition temperature increases at first and then decreases. PMID:28773748

  11. Photostabilizing Efficiency of Poly(vinyl chloride) in the Presence of Organotin(IV) Complexes as Photostabilizers.

    PubMed

    Ali, Mustafa M; El-Hiti, Gamal A; Yousif, Emad

    2016-08-30

    Three organotin complexes containing furosemide as a ligand (L), Ph₃SnL, Me₂SnL₂ and Bu₂SnL₂, were synthesized and characterized. Octahedral geometry was proposed for the Me₂SnL₂ and Bu₂SnL₂, while the Ph₃SnL complex has trigonal bipyramid geometry. The synthesized organotin complexes (0.5% by weight) were used as additives to improve the photostability of poly(vinyl chloride), PVC, (40 μm thickness) upon irradiation. The changes imposed on functional groups, weight loss and viscosity average molecular weight of PVC films were monitored. The experimental results show that the rate of photodegradation was reduced in the presence of the organotin additives. The quantum yield of the chain scission was found to be low (9.8 × 10(-7)) when Ph₃SnL was used as a PVC photostabilizer compared to controlled PVC (5.18 × 10(-6)). In addition, the atomic force microscope images for the PVC films containing Ph₃SnL₂ after irradiation shows a smooth surface compared to the controlled films. The rate of PVC photostabilization was found to be highest for Ph₃SnL followed by Bu₂SnL₂ and Me₂SnL₂. It has been suggested that the organotin complexes could act as hydrogen chloride scavengers, ultraviolet absorbers, peroxide decomposers and/or radical scavengers.

  12. A novel reutilization method for waste printed circuit boards as flame retardant and smoke suppressant for poly (vinyl chloride).

    PubMed

    Xiu, Fu-Rong; Weng, Huiwei; Qi, Yingying; Yu, Gending; Zhang, Zhigang; Zhang, Fu-Shen

    2016-09-05

    In this study, a novel reutilization method for waste printed circuit boards (PCBs) as flame retardant and smoke suppressant for poly (vinyl chloride) (PVC) was successfully testified. A supercritical water oxidation (SCWO) process was applied to treat waste PCBs before they could be used as flame retardants of PVC. The results indicated that SCWO conditions had a significant effect on the flame retarding and smoke suppressing properties of waste PCBs for PVC. Cu2O, CuO, and SnO2 were the main active ingredients in waste PCBs-derived flame retardants. A conversion of Cu elements (Cu(0)→Cu(+)→Cu(2+)) during SCWO process with the increase of reaction temperature was found to be the key influence factor for the flame retarding properties of SCWO-treated PCBs. The experiment results also showed that there was a synergistic effect of flame retardancy between Cu(+) and Cu(2+). After the optimized SCWO treatment, SCWO-treated PCBs significantly improved the flame retardancy and smoke suppression of PVC. Limiting oxygen index (LOI) and char yield (CY) increased with increasing SCWO-treated PCBs content in PVC, while smoke density rating (SDR) and maximum smoke density (MSD) decreased markedly. The mechanical properties of PVC samples were influenced in different degree by adding different content SCWO-treated PCBs.

  13. Recycled Poly(vinyl alcohol) Sponge for Carbon Encapsulation of Size-Tunable Tin Dioxide Nanocrystalline Composites.

    PubMed

    Ma, Yue; Tai, Cheuk-Wai; Gustafsson, Torbjörn; Edström, Kristina

    2015-06-22

    The recycling of industrial materials could reduce their environmental impact and waste haulage fees and result in sustainable manufacturing. In this work, commercial poly(vinyl alcohol) (PVA) sponges are recycled into a macroporous carbon matrix to encapsulate size-tunable SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) through a scalable, flash-combustion method. The hydroxyl groups present copiously in the recycled PVA sponges guarantee a uniform chemical coupling with a tin(IV) citrate complex through intermolecular hydrogen bonds. Then, a scalable, ultrafast combustion process (30 s) carbonizes the PVA sponge into a 3D carbon matrix. This PVA-sponge-derived carbon could not only buffer the volume fluctuations upon the Li-Sn alloying and dealloying processes but also afford a mixed conductive network, that is, a continuous carbon framework for electrical transport and macropores for facile electrolyte percolation. The best-performing electrode based on this composite delivers a rate performance up to 9.72 C (4 A g(-1) ) and long-term cyclability (500 cycles) for Li(+) ion storage. Moreover, cyclic voltammograms demonstrate the coexistence of alloying and dealloying processes and non-diffusion-controlled pseudocapacitive behavior, which collectively contribute to the high-rate Li(+) ion storage. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Protein aggregation with poly(vinyl) alcohol surfactant reduces double emulsion-encapsulated mammalian cell-free expression

    PubMed Central

    Ho, Kenneth K. Y.; Lee, Jin Woo; Durand, Grégory; Majumder, Sagardip

    2017-01-01

    Development of artificial cell models requires encapsulation of biomolecules within membrane-bound compartments. There have been limited studies of using mammalian cell-free expression (CFE) system as the ‘cytosol’ of artificial cells. We exploit glass capillary droplet microfluidics for the encapsulation of mammalian CFE within double emulsion templated vesicles. The complexity of the physicochemical properties of HeLa cell-free lysate poses a challenge compared with encapsulating simple buffer solutions. In particular, we discovered the formation of aggregates in double emulsion templated vesicles encapsulating mammalian HeLa CFE, but not with bacterial CFE. The aggregates did not arise from insolubility of the proteins made from CFE nor due to the interaction of mammalian CFE with the organic solvents in the middle phase of the double emulsions. We found that aggregation is dependent on the concentration of poly(vinyl) alcohol (PVA) surfactant, a critical double emulsion-stabilizing surfactant, and the lysate concentration in mammalian CFE. Despite vesicle instability and reduced protein expression, we demonstrate protein expression by encapsulating mammalian CFE system. Using mass spectrometry and Western blot, we identified and verified that actin is one of the proteins inside the mammalian CFE that aggregated with PVA surfactant. Our work establishes a baseline description of mammalian CFE system encapsulated in double emulsion templated vesicles as a platform for building artificial cells. PMID:28358875

  15. Shape Memory Composites Based on Electrospun Poly(vinyl alcohol) Fibers and a Thermoplastic Polyether Block Amide Elastomer.

    PubMed

    Shirole, Anuja; Sapkota, Janak; Foster, E Johan; Weder, Christoph

    2016-03-01

    The present study aimed at developing new thermally responsive shape-memory composites, that were fabricated by compacting mats of electrospun poly(vinyl alcohol) (PVA) fibers and sheets of a thermoplastic polyether block amide elastomer (PEBA). This design was based on the expectation that the combination of the rubber elasticity of the PEBA matrix and the mechanical switching exploitable through the reversible glass transition temperature (Tg) of the PVA filler could be combined to create materials that display shape memory characteristics as an emergent effect. Dynamic mechanical analyses (DMA) show that, upon introduction of 10-20% w/w PVA fibers, the room-temperature storage modulus (E') increased by a factor of 4-5 in comparison to the neat PEBA, and they reveal a stepwise reduction of E' around the Tg of PVA (85 °C). This transition could indeed be utilized to fix a temporary shape and recover the permanent shape. At low strain, the fixity was 66 ± 14% and the recovery was 98 ± 2%. Overall, the data validate a simple and practical strategy for the fabrication of shape memory composites that involves a melt compaction process and employs two commercially available polymers.

  16. Amidine-Functionalized Poly(2-vinyl-4,4-dimethylazlactone) for Selective and Efficient CO2 Fixing

    DOE PAGES

    Barkakaty, Balaka; Browning, Katie L.; Sumpter, Bobby; ...

    2016-02-12

    Development of novel polymeric materials capable of efficient CO2 capture and separation under ambient conditions is crucial for cost-effective and practical industrial applications. Here we report the facile synthesis of a new CO2-responsive polymer through post-polymerization modification of poly(2 vinyl-4,4-dimethylazlactone) (PVDMA). The reactive pendant azlactone groups of PVDMA are easily modified with 4-(N-methyltetrahydropyrimidine) benzyl alcohol (PBA) without any by-product formation. FTIR and TGA experiments show the new PBA functionalized polymer powder can reversibly capture CO2 at room temperature and under atmospheric pressure. CO2 capture was selective, showing a high fixing efficiency even with a mixed gas system (20% CO2, 80%more » N2) similar to flue gas. CO2 release occurred at room temperature and release profiles were investigated as a function of temperature. Density Functional Theory (DFT) calculations coupled with modeling and simulation reveal the presence of two CO2 binding sites in the PBA functionalized polymer resulting in a two-step CO2 release at room temperature. Finally, we find that the ease of material preparation, high fixing efficiency, and robust release characteristics suggest that post-polymerization modification may be a useful route to designing new materials for CO2 capture.« less

  17. Multifractal analysis of fracture morphology of poly(ethylene-co-vinyl acetate)/carbon black conductive composite

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Hai; Bai, Bao-Feng; Chen, Jing-Bo; Shen, Chang-Yu; Li, Jian-Qiang

    2010-09-01

    In this paper, based on scanning electron microscope (SEM), the fracture morphology of poly(ethylene-co-vinyl acetate)/carbon black (EVA/CB) conductive composite with various cross-linkers 2,4-di(2-phenylisopropyl) phenol (DCP) contents were analysed by multifractal analysis. The relationship among the multifractal spectrum, cross-linker DCP content, the fracture morphology, fracture process and some mechanical property were discussed. The results showed that the larger the width Δ α (Δ α = αmax - αmin) of the multifractal spectra f( α), the more nonuniform the fracture surface morphology, in other words, the more the roughness. Moreover, the width Δ α (Δ α = αmax - αmin) of the multifractal spectra f( α) is the result of competition between ductile fracture and brittle fracture. Also, some mechanical property will correspondingly change when various cross-linker DCP contents were added. Multifractal analysis showed that the spectrum width Δ α (Δ α = αmax - αmin) of the multifractal spectra f( α) could be used to characterize the surface morphology and mechanical property of EVA/CB conductive composite, quantitatively.

  18. Inductive effect of poly(vinyl pyrrolidone) on morphology and photocatalytic performance of Bi2WO6

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Chen, Jinxing; Xie, Yunyun; Wang, Mozhen; Ge, Xuewu

    2016-04-01

    Bi2WO6 has great potential applications in the field of photocatalyst due to its excellent visible-light photocatalytic performance. This work studied the detailed morphological evolution of Bi2WO6 particles synthesized in a simple hydrothermal system induced by the stabilizer poly(vinyl pyrrolidone) (PVP). The XRD and HRTEM results show PVP would not change the crystal structure of Bi2WO6, but the distribution of PVP on the initially formed Bi2WO6 nanosheets will induce the crystal growth, resulting in a distinct morphology evolution of Bi2WO6 with the increase of the concentration of PVP. At the same time, with the increase of the molecular weight of PVP, the morphology of Bi2WO6 varied from simple sheet-like (S-BWO) to some complicated morphology, such as flower-like (F-BWO), red blood cell-like (B-BWO), and square-pillar-like (SP-BWO). The photocatalytic performances of Bi2WO6 with various morphologies on the decomposition of RhB under visible light irradiation reveal that S-BWO has the best photocatalytic performance, while SP-BWO has the worst. This work not only gives the explanation of the inductive effect of PVP molecular chains on the morphological formation of Bi2WO6 particles, but also provides the controllable way to the preparation of Bi2WO6 with various morphologies taking advantage of the stabilizer PVP.

  19. Recyclable and stable silver deposited magnetic nanoparticles with poly (vinyl pyrrolidone)-catechol coated iron oxide for antimicrobial activity.

    PubMed

    Mosaiab, Tamim; Jeong, Chan Jin; Shin, Gyo Jic; Choi, Kyung Ho; Lee, Sang Kug; Lee, Iksoo; In, Insik; Park, Sung Young

    2013-10-01

    This paper introduces a facile method to make highly stable and recyclable antimicrobial magnetic nanoparticles (NPs). Initially, magnetic iron oxide nanoparticles (IONPs) were coated with poly (vinyl pyrrolidone) conjugated catechol (PVP-CCDP). Afterward, silver nanoparticles (Ag(0)) were deposited onto PVP-CCDP coated IONPs using remain catechol. The prepared nanoparticles showed long term (~4 weeks) colloidal stability and redispersibility, respectively, against external magnetic field and over a broad range of pH (4-12). The NPs were characterized by UV-vis, SEM, XPS, and XRD measurements. TEM and DLS analyses showed that the mean particle size of PVP-CCDP coated IONPs/Ag(0) were about 72 nm. The recyclable magnetic NPs possessed a high antibacterial effect against the model microbes Staphylococcus aureus and Escherichia coli and could be separated easily using magnet following antibacterial test for repeated uses and maintained 100% antibacterial efficiency during three cycles. In MTT assay, the magnetic nanoparticles possessed no measureable cytotoxicity to live cells.

  20. Poly(vinyl chloride) film filled with microcrystalline cellulose prepared from cotton fabric waste: properties and biodegradability study.

    PubMed

    Chuayjuljit, Saowaroj; Su-uthai, Siriwan; Charuchinda, Sireerat

    2010-02-01

    Hydrolysis of cotton fabric waste to produce microcrystalline cellulose (MCC) was carried out using 2.5 N hydrochloric acid at 100 degrees C for 30 min. Characterization of the structure, morphology, particle size as well as the thermal decomposition of the obtained MCC were studied using X-ray diffractometer, scanning electron microscope and laser light scattering particle size analyzer and thermogravimetric analyzer, respectively. These results indicated that the obtained MCC had a fibrous structure of a 40 microm average particle size and possessed a form of highly native crystalline cellulose I. In addition, its maximum degradation temperature was observed at 350 degrees C. The poly(vinyl chloride) (PVC) films in this work were produced by first blending the produced MCC with PVC resin in amounts of 5-30 parts per hundred of resin. The blends were then made into film using a two-roll mill. The tensile properties of the film were measured using a Universal Testing Machine. The biodegradation tests were carried out in soil and in a moisture-controlled chamber. The biodegradability was estimated by the loss of mass, moisture absorption capacity and electron microscope studies. It was found that the tensile strength and Young's modulus of the blends increased with increasing amounts of MCC. Similarly, moisture absorption and biodegradability of the films were also increased as the amount of MCC increased. The results implied that MCC behaved not only as a reinforcing filler but also as a biodegradability promoter of PVC films.

  1. Effect of electron beam irradiation on the structural, thermal and optical properties of poly(vinyl alcohol) thin film

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Bahareth, Radiyah A.

    2013-04-01

    Poly(vinyl alcohol) (PVA) polymer was prepared using the casting technique. The obtained PVA thin films have been irradiated with electron beam doses ranging from 20 to 300 kGy. The resultant effect of electron beam irradiation on the structural properties of PVA has been investigated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), while the thermal properties have been investigated using thermo-gravimetric analysis and differential thermal analysis (DTA). The onset temperature of decomposition T 0 and activation energy of thermal decomposition E a were calculated, results indicate that the PVA thin film decomposes in one main weight loss stage. Also, the electron beam irradiation in dose range 95-210 kGy led to a more compact structure of the PVA polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with electron beam dose has been determined using DTA. The PVA thermograms were characterized by the appearance of an endothermic peak due to melting. In addition, the transmission of the PVA samples and any color changes were studied. The color intensity Δ E was greatly increased with increasing electron beam dose, and was accompanied by a significant increase in the blue color component.

  2. Effects of Molecular Weight upon Irradiation-Cross-Linked Poly(vinyl alcohol)/Clay Aerogel Properties.

    PubMed

    Chen, Hong-Bing; Zhao, Yan; Shen, Peng; Wang, Jun-Sheng; Huang, Wei; Schiraldi, David A

    2015-09-16

    Facile fabrication of mechanically strong poly(vinyl alcohol) (PVOH)/clay aerogel composites through a combination of increasing polymer molecular weights and gamma irradiation-cross-linking is reported herein. The aerogels produced from high polymer molecular weights exhibit significantly increased compressive moduli, similar to the effect of irradiation-induced cross-linking. The required irradiation dose for fabricating strong PVOH composite aerogels with dense microstructure decreased with increasing polymer molecular weight. Neither thermal stability nor flammability was significantly changed by altering the polymer molecular weight or by modest gamma irradiation, but they were highly dependent upon the polymer/clay ratio in the aerogel. Optimization of the mechanical, thermal, and flammability properties of these composite aerogels could therefore be obtained by using relatively low levels of polymer, with very high polymer molecular weight, or lower molecular weight coupled with moderate gamma irradiation. The facile preparation of strong, low flammability aerogels is an alternative to traditional polymer foams in applications where fire safety is important.

  3. Antifouling and antimicrobial polymer membranes based on bioinspired polydopamine and strong hydrogen-bonded poly(N-vinyl pyrrolidone).

    PubMed

    Jiang, Jinhong; Zhu, Liping; Zhu, Lijing; Zhang, Hongtao; Zhu, Baoku; Xu, Youyi

    2013-12-26

    A facile and versatile approach for the preparation of antifouling and antimicrobial polymer membranes has been developed on the basis of bioinspired polydopamine (PDA) in this work. It is well-known that a tightly adherent PDA layer can be generated over a wide range of material surfaces through a simple dip-coating process in dopamine aqueous solution. The resulting PDA coating is prone to be further surface-tailored and functionalized via secondary treatments because of its robust reactivity. Herein, a typical hydrophobic polypropylene (PP) porous membrane was first coated with a PDA layer and then further modified by poly(N-vinyl pyrrolidone) (PVP) via multiple hydrogen-bonding interactions between PVP and PDA. Data of water contact angle measurements showed that hydrophilicity and wettability of the membranes were significantly improved after introducing PDA and PVP layers. Both permeation fluxes and antifouling properties of the modified membranes were enhanced as evaluated in oil/water emulsion filtration, protein filtration, and adsorption tests. Furthermore, the modified membranes showed remarkable antimicrobial activity after iodine complexation with the PVP layer. The PVP layer immobilized on the membrane had satisfying long-term stability and durability because of the strong noncovalent forces between PVP and PDA coating. The strategy of material surface modification reported here is substrate-independent, and applicable to a broad range of materials and geometries, which allows effective development of materials with novel functional coatings based on the mussel-inspired surface chemistry.

  4. In situ fabricated platinum—poly(vinyl alcohol) nanocomposite thin film: a highly reusable ‘dip catalyst’ for hydrogenation

    NASA Astrophysics Data System (ADS)

    Divya Madhuri, U.; Kesava Rao, V.; Hariprasad, E.; Radhakrishnan, T. P.

    2016-04-01

    A simple protocol for the in situ generation of platinum nanoparticles in a poly(vinyl alcohol) (PVA) thin film is developed. Chloroplatinic acid as well as potassium platinum(II) chloride are used as precursors and the film is fabricated by spin coating followed by mild thermal annealing. The chemical process occurring inside the film, wherein the polymer itself acts as the reducing agent, is explored through different spectroscopy and microscopy techniques. The Pt-PVA film, <100 nm thick and containing ˜1 nm size Pt nanoparticles, is shown to be a highly efficient catalyst for the reduction of methylene blue using sodium borohydride. The ease of retrieval and reuse of the thin film is highlighted by the term ‘dip catalyst’. The reaction yield, kinetics and rate are reproducible through several reuses of the same catalyst film. Turnover number (TON = number of mols of product/number of mols of catalyst) and turnover frequency (TOF = TON/reaction time) are significantly higher than those reported earlier for this reaction using metal nanocatalysts. Utility of Pt-PVA film as an efficient catalyst for other hydrogenation reactions is demonstrated.

  5. Borax mediated layer-by-layer self-assembly of neutral poly(vinyl alcohol) and chitosan.

    PubMed

    Manna, Uttam; Patil, Satish

    2009-07-09

    We report a multilayer film of poly(vinyl alcohol) (PVA)-borate complex and chitosan by using a layer-by-layer approach. PVA is an uncharged polymer, but hydroxyl functional groups of PVA can be cross-linked by using borax as a cross-linking agent. As a result electrostatic charges and intra- and interchain cross-links are introduced in the PVA chain and provide physically cross-linked networks. The PVA-borate was then deposited on a flat substrate as well as on colloidal particles with chitosan as an oppositely charged polyelectrolyte. Quartz crystal microbalance, scanning electron microscopy, and atomic force microscopy were used to follow the growth of thin film on flat substrate. Analogous experiments were performed on melamine formaldehyde colloidal particles (3-3.5 microm) to quantify the process for the preparation of hollow microcapsules. Removal of the core in 0.1 N HCl results in hollow microcapsules. Characterization of microcapsules by transmission electron microscopy revealed formation of stable microcapsules. Further, self-assembly of PVA-borate/chitosan was loaded with the anticancer drug doxorubicin, and release rates were determined at different pH values to highlight the drug delivery potential of this system.

  6. Consequences of poly(vinyl chloride) presence on the thermochemical process of lignocellulosic biomass in CO₂ by thermogravimetric analysis.

    PubMed

    He, Yao; Ma, Xiaoqian; Zeng, Guangbo

    2015-02-01

    The thermochemical processes of lignocellulosic biomass and its mixtures with poly(vinyl chloride) (PVC) fractions were investigated by thermogravimetric analysis in CO2 atmosphere. Superposition property was assumed to examine whether and/or to what extent interactions occurred during the mixture decomposition. Results showed that interactions existed, of which the intensities changed with reaction stage, heating rate and PVC quantity, and they actively behaved toward the decomposition in most cases. With PVC presence, lignocellulosic biomass turned from three-stage to four-stage decomposition process where the reactions occurred at lower temperatures with heightened intensity, especially in the first stage. The measured activation energies calculated by Ozawa-Flynn-Wall and Vyazovkin methods were of minor difference <5 kJ/mol, and comparing them between materials in each stage confirmed the results of interaction impact. This work provides a theoretical basis bringing about the possibilities of recycling CO2 into a reaction medium of thermo-treatment of lignocellulosic material with PVC contaminants.

  7. Horseradish peroxidase-catalyzed formation of hydrogels from chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups.

    PubMed

    Sakai, Shinji; Khanmohammadi, Mehdi; Khoshfetrat, Ali Baradar; Taya, Masahito

    2014-10-13

    Horseradish peroxidase-catalyzed cross-linking was applied to prepare hydrogels from aqueous solutions containing chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups (denoted as Ph-chitosan and Ph-PVA, respectively). Comparing the hydrogels prepared from the solution of 1.0% (w/v) Ph-chitosan and 3.0% (w/v) Ph-PVA and that of 3.0% (w/v) Ph-chitosan and 1.0% (w/v) Ph-PVA, the gelation time of the former hydrogel was 47 s, while was 10s longer than that of the latter one. The breaking point for the former hydrogel under stretching (114% strain) was approximately twice larger than that for the latter one. The swelling ratio of the former hydrogel in saline was about half of the latter one. Fibroblastic cells did not adhere on the former hydrogel but adhered and spread on the latter one. The growth of Escherichia coli cells was fully suppressed on the latter hydrogel during 48 h cultivation.

  8. Poly(vinyl alcohol) films reinforced with nanofibrillated cellulose (NFC) isolated from corn husk by high intensity ultrasonication.

    PubMed

    Xiao, Shaoliang; Gao, Runan; Gao, LiKun; Li, Jian

    2016-01-20

    This work was aimed at fabricating and characterizing poly(vinyl alcohol) films that were reinforced by nanofibrillated corn husk celluloses using a combination of chemical pretreatments and ultrasonication. The obtained nanofibrillated celluloses (NFCs) possessed a narrow width ranging from 50 to 250 nm and a high aspect ratio (394). The crystalline type of NFC was cellulose I type. Compared with the original corn husks, the NCF crystallinity and thermal stability increased due to the removal of the hemicelluloses and lignin. PVA films containing different NFC concentrations (0.5%, 1%, 3%, 5%, 7% and 9%, w/w, dry basis) were examined. The 1% PVA/NFC reinforced films exhibited a highly visible light transmittance of 80%, and its tensile strength and the tensile strain at break were increased by 1.47 and 1.80 times compared to that of the pure PVA film, respectively. The NFC with high aspect ratio and high crystallinity is beneficial to the improvement of the mechanical strength and thermal stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. A sustainable slashing industry using biodegradable sizes from modified soy protein to replace petro-based poly(vinyl alcohol).

    PubMed

    Zhao, Yi; Zhao, Yuzhu; Xu, Helan; Yang, Yiqi

    2015-02-17

    Biodegradable sizing agents from triethanolamine (TEA) modified soy protein could substitute poly(vinyl alcohol)(PVA) sizes for high-speed weaving of polyester and polyester/cotton yarns to substantially decrease environmental pollution and impel sustainability of textile industry. Nonbiodegradable PVA sizes are widely used and mainly contribute to high chemical oxygen demand (COD) in textile effluents. It has not been possible to effectively degrade, reuse or replace PVA sizes so far. Soy protein with good biodegradability showed potential as warp sizes in our previous studies. However, soy protein sizes lacked film flexibility and adhesion for required high-speed weaving. Additives with multiple hydroxyl groups, nonlinear molecule, and electric charge could physically modify secondary structure of soy protein and lead to about 23.6% and 43.3% improvement in size adhesion and ability of hair coverage comparing to unmodified soy protein. Industrial weaving results showed TEA-soy protein had relative weaving efficiency 3% and 10% higher than PVA and chemically modified starch sizes on polyester/cotton fabrics, and had relative weaving efficiency similar to PVA on polyester fabrics, although with 3- 6% lower add-on. In addition, TEA-soy sizes had a BOD5/COD ratio of 0.44, much higher than 0.03 for PVA, indicating that TEA-soy sizes were easily biodegradable in activated sludge.

  10. Electromechanical behavior of polyaniline/poly (vinyl alcohol) blend films under static, dynamic and time-dependent strains

    NASA Astrophysics Data System (ADS)

    Akhilesan, S.; Lakshmana Rao, C.; Varughese, S.

    2014-07-01

    We report on the experimentally observed electrical conductivity enhancement in polyaniline/poly (vinyl alcohol) blend films under uniaxial tensile loading. Polyaniline (PANI) is an intrinsically conducting polymer, which does not form stretchable free-standing films easily and hence its electromechanical characterization is a challenge. Blending of PANI with other insulating polymers is a good choice to overcome the processability problem. We report the electromechanical response of solution blended and HCl doped PANI/PVA blends subjected to uniaxial, static, dynamic and time-dependent tensile loading. The demonstrated viscoelastic and morphological contributions of the component polymers to the electrical conductivity behavior in these blends could lead to interesting applications in strain sensors and flexible electronics. The reversibility of the electromechanical response under dynamic strain is found to increase in blends with higher PANI content. Time-dependent conductivity studies during mechanical stress relaxation reveal that variations in the micro-domain ordering and the relative relaxation rate of the individual polymer phases can give rise to interesting electrical conductivity changes in PANI blends. From morphological and electrical conductivity studies, we show that PANI undergoes primary and secondary agglomeration behavior in these blends that contributes to the changes in conductivity behavior during the deformation. A 3D variable range hopping (VRH) process, which uses a deformable core and shell concept based on blend morphology analysis, is used to explain the experimentally observed electromechanical behavior.

  11. Prolonged Hypocalcemic Effect by Pulmonary Delivery of Calcitonin Loaded Poly(Methyl Vinyl Ether Maleic Acid) Bioadhesive Nanoparticles

    PubMed Central

    Varshosaz, J.; Minaiyan, M.; Forghanian, M.

    2014-01-01

    The purpose of the present study was to design a pulmonary controlled release system of salmon calcitonin (sCT). Therefore, poly(methyl vinyl ether maleic acid) [P(MVEMA)] nanoparticles were prepared by ionic cross-linking method using Fe2+ and Zn2+ ions. Physicochemical properties of nanoparticles were studied in vitro. The stability of sCT in the optimized nanoparticles was studied by electrophoretic gel method. Plasma calcium levels until 48 h were determined in rats as pulmonary-free sCT solution or nanoparticles (25 μg·kg−1), iv solution of sCT (5 μg·kg−1), and pulmonary blank nanoparticles. The drug remained stable during fabrication and tests on nanoparticles. The optimized nanoparticles showed proper physicochemical properties. Normalized reduction of plasma calcium levels was at least 2.76 times higher in pulmonary sCT nanoparticles compared to free solution. The duration of hypocalcemic effect of pulmonary sCT nanoparticles was 24 h, while it was just 1 h for the iv solution. There was not any significant difference between normalized blood calcium levels reduction in pulmonary drug solution and iv injection. Pharmacological activity of nanoparticles after pulmonary delivery was 65% of the iv route. Pulmonary delivery of P(MVEMA) nanoparticles of sCT enhanced and prolonged the hypocalcemic effect of the drug significantly. PMID:24701588

  12. Evaluation of poly (vinyl alcohol) based cryogel-zinc oxide nanocomposites for possible applications as wound dressing materials.

    PubMed

    Chaturvedi, Archana; Bajpai, Anil K; Bajpai, Jaya; K Singh, Sunil

    2016-08-01

    In this investigation cryogels composed of poly (vinyl alcohol) (PVA) were prepared by repeated freeze thaw method followed by in situ precipitation of zinc oxide nanoparticles within the cryogel networks. Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX) were used to characterize the nanocomposites. The morphologies of native PVA cryogels and PVA cryogel-ZnO nanocomposites were observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) techniques. The SEM analysis suggested that cryogels show a well-defined porous morphology whereas TEM micrographs revealed the presence of nearly spherical and well separated zinc oxide nanoparticles with diameter<100nm. XRD results showed all relevant Bragg's reflections for crystal structure of zinc oxide nanoparticles. Thermo gravimetric-differential thermal analysis (TG-DTA) was conducted to evaluate thermal stability of the nanocomposites. Mechanical properties of nanocomposites were determined in terms of tensile strength and percent elongation. Biocompatible nature was ascertained by anti-haemolytic activity, bovine serum albumin (blood protein) adsorption and in vitro cytotoxicity tests. The prepared nanocomposites were also investigated for swelling and deswelling behaviours. The results revealed that both the swelling and deswelling process depend on the chemical composition of the nanocomposites, number of freeze-thaw cycles, pH and temperature of the swelling medium. The developed biocompatible PVA cryogel-ZnO nanocomposites were also tested for antibacterial activities against both Gram-negative and Gram-positive bacteria.

  13. Structure, corrosion behavior and mechanical property of a novel poly(vinyl alcohol) composite in simulated body fluid.

    PubMed

    Li, Juan; Suo, Jinping; Zou, Peng; Jia, Lintao; Wang, Shifang

    2010-01-01

    The data for long-term drug-delivery systems are scarce compared to the short-term systems because the required research efforts are more time-consuming. In this study, we report a novel cross-linked composite based on poly(vinyl alcohol) (PVA) containing cupric ions for long-term delivery, which is helpful for contraception and trace element balance in the human body. The composition, corrosion products, crystal structure, chemical structure and mechanical stability of the composite, after being immersed in simulated body fluid (SBF) for one year, were studied by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and mechanical testing. The results show that no other new elements, such as P, Cl and Ca, appear on the surface of the composite and no Cu(2)O was formed after immersion in SBF for one year. The effectiveness of copper can be greatly improved and the side-effects caused by these compounds might also be eliminated. Furthermore, this novel composite exhibits long-term mechanical stability in SBF. The present in vitro long-term data suggest that this novel copper-containing composite may serve as a substitute for conventional materials of copper-containing intrauterine devices (Cu-IUDs) and as a carrier for controlled-release material in a variety of other applications.

  14. Poly(vinyl alcohol) nanoparticles prepared by freezing-thawing process for protein/peptide drug delivery.

    PubMed

    Li, J K; Wang, N; Wu, X S

    1998-12-04

    Poly(vinyl alcohol) (PVA) hydrogel nanoparticles have been prepared by using a water-in-oil emulsion technology plus cyclic freezing-thawing process. The PVA hydrogel nanoparticles prepared by this method are suitable for protein/peptide drug delivery since formation of the hydrogel does not require crosslinking agents or other adjuvants and does not involve any residual monomer. Particularly, there is no emulsifier involved in this new method. Bovine serum albumin (BSA), as a model protein drug, is incorporated into the PVA hydrogel nanoparticles. The PVA hydrogel nanoparticles possess a skewed or log-normal size distribution. The average diameter of the PVA hydrogel nanoparticles is 675.5+/-42.7 nm. Protein drug loading efficiency in the PVA hydrogel nanoparticles is 96.2+/-3.8%. The PVA hydrogel nanoparticles swell in an aqueous solution and the swelling degree increases with the increase of temperature. In vitro release studies show that the BSA release from the nanoparticles can be prolonged to 30 h. The BSA release follows a diffusion-controlled mechanism. The number of freezing-thawing cycle and release temperature both influence BSA release rate considerably. Less freezing-thawing cycle or higher release temperature leads to faster drug release. The BSA is stable during preparation of the PVA hydrogel nanoparticles.

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

    PubMed Central

    2015-01-01

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

  16. Facile approach to the fabrication of 3D cellulose nanofibrils (CNFs) reinforced poly(vinyl alcohol) hydrogel with ideal biocompatibility.

    PubMed

    Chen, Xiao; Chen, Chuntao; Zhang, Heng; Huang, Yang; Yang, Jiazhi; Sun, Dongping

    2017-10-01

    In this study, the reinforcing effects of cellulose nanofibrils (CNFs) on poly (vinyl alcohol) (PVA) matrix were explored. And ethylene glycol was used to enhance the water content and phosphate buffer saline (PBS) absorbency. The morphological aspects of the hydrogel were studied by transmission electron microscope (TEM) and scanning electron microscopy (SEM). The presence of interactions, changes in crystallinity as well as thermal behaviour were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetry respectively. With the increase of CNFs concentration, the composite greatly improved its mechanical strength while maintaining remarkable ductility through tensile test results. The positive results of cell toxicity test suggested our porous hydrogel could provide ideal cell growth environment. This work revealed that CNFs hydrolysed by bacterial cellulose could perform as a perfect reinforcing agents which is of great interest in the fields of biotechnology and biomedicine with the potential values in cell culture, co-cultivation, as well as biomedical scaffold materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Protein aggregation with poly(vinyl) alcohol surfactant reduces double emulsion-encapsulated mammalian cell-free expression.

    PubMed

    Ho, Kenneth K Y; Lee, Jin Woo; Durand, Grégory; Majumder, Sagardip; Liu, Allen P

    2017-01-01

    Development of artificial cell models requires encapsulation of biomolecules within membrane-bound compartments. There have been limited studies of using mammalian cell-free expression (CFE) system as the 'cytosol' of artificial cells. We exploit glass capillary droplet microfluidics for the encapsulation of mammalian CFE within double emulsion templated vesicles. The complexity of the physicochemical properties of HeLa cell-free lysate poses a challenge compared with encapsulating simple buffer solutions. In particular, we discovered the formation of aggregates in double emulsion templated vesicles encapsulating mammalian HeLa CFE, but not with bacterial CFE. The aggregates did not arise from insolubility of the proteins made from CFE nor due to the interaction of mammalian CFE with the organic solvents in the middle phase of the double emulsions. We found that aggregation is dependent on the concentration of poly(vinyl) alcohol (PVA) surfactant, a critical double emulsion-stabilizing surfactant, and the lysate concentration in mammalian CFE. Despite vesicle instability and reduced protein expression, we demonstrate protein expression by encapsulating mammalian CFE system. Using mass spectrometry and Western blot, we identified and verified that actin is one of the proteins inside the mammalian CFE that aggregated with PVA surfactant. Our work establishes a baseline description of mammalian CFE system encapsulated in double emulsion templated vesicles as a platform for building artificial cells.

  18. In vitro investigation of the effect of plasticizers on the blood compatibility of medical grade plasticized poly (vinyl chloride).

    PubMed

    Zhong, Rui; Wang, Hong; Wu, Xia; Cao, Ye; He, Zeng; He, Yuliang; Liu, Jiaxin

    2013-08-01

    This paper reports the results of an in vitro investigation into the blood response of medical grade poly (vinyl chloride) (PVC), and two types of plasticized PVC in tubing or sheet form, with di-(2-ethylhexyl)phthalate (DEHP) and di(isononyl) cyclohexane-1,2-dicarboxylate (HEXAMOLL(®) DINCH) as plasticizer, were selected for assessment of complement activation, coagulation system and platelet activation. The results of the study show that not only the plasticizers at PVC surface have an influence on complement activation, but also the incubation condition such as incubation time and the diameter of PVC tubing. Under static status, C3a, C5a and SC5b-9 concentration in the blood were higher after contacting with PVC plasticized with DEHP (PVC1) than after contacting with PVC plasticized with DINCH (PVC2). However, under dynamic circulation, the results were totally converse, which may be due to smaller diameter and higher shear rate of PVC2. In addition, there was a significant increase of activated partial thrombin time (APTT) and decrease of FIX concentration after plasma contacting with the PVC tubing, which indicated that the intrinsic pathway may be impacted when blood contacted with PVC tubing. However, there was no significant difference of APTT, FIX concentration and CD62p expression rate between the two materials. Moreover, the migration in the DINCH system was considerably lower than for DEHP, which indicates that DINCH could be a promising alterative plasticizer of DEHP.

  19. A novel crosslinking strategy for preparing poly(vinyl alcohol)-based proton-conducting membranes with high sulfonation

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-En; Lin, Chi-Wen; Hwang, Bing-Joe

    This study synthesizes poly(vinyl alcohol) (PVA)-based polymer electrolyte membranes by a two-step crosslinking process involving esterization and acetal ring formation reactions. This work also uses sulfosuccinic acid (SSA) as the first crosslinking agent to form an inter-crosslinked structure and a promoting sulfonating agent. Glutaraldehyde (GA) as the second crosslinking agent, reacts with the spare OH group of PVA and forms, not only a dense structure at the outer membrane surface, but also a hydrophobic protective layer. Compared with membranes prepared by a traditional one-step crosslinking process, membranes prepared by the two-step crosslinking process exhibit excellent dissolution resistance in water. The membranes become water-insoluble even at a molar ratio of SO 3H/PVA-OH as high as 0.45. Moreover, the synthesized membranes also exhibit high proton conductivities and high methanol permeability resistance. The current study measures highest proton conductivity of 5.3 × 10 -2 S cm -1 at room temperature from one of the synthesized membranes, higher than that of the Nafion ® membrane. Methanol permeability of the synthesized membranes measures about 1 × 10 -7 cm 2 S -1, about one order of magnitude lower than that of the Nafion ® membrane.

  20. Ion-selective detection by plasticized poly(vinyl chloride) membrane in glass nanopipette with alternating voltage modulation.

    PubMed

    Deng, Xiao Long; Takami, Tomohide; Son, Jong Wan; Kang, Eun Ji; Kawai, Tomoji; Park, Bae Ho

    2013-08-01

    An alternating current (AC) voltage modulation was applied to ion-selective observations with plasticized poly(vinyl chloride) membranes in glass nanopipettes. The liquid confronting the membranes in the nanopipettes, the conditioning process, and AC voltage modulation play important roles in the ion-selective detection. In the AC detection system developed by us, where distilled water was used as the liquid within the nanopipettes, potassium ions were selectively detected in the sample solution of sodium and potassium ions because sodium ions were captured at the membrane containing bis(12-crown-4) ionophores, before the saturation of the ionophores. The membrane lost the selectivity after the saturation. On using sodium chloride as the liquid within the nanopipette, the membrane selectively detected potassium and sodium ions before and after the saturation of ionophores, respectively. The ion-selective detection of our system can be explained by the ion extraction-diffusion-dissolution mechanism through the bis(12-crown-4) ionophores with AC voltage modulation.

  1. Synthesis of persulfate containing poly ( N-vinyl-2-pyrrolidone) (PVP) hydrogels in aqueous solutions by γ-induced radiation

    NASA Astrophysics Data System (ADS)

    Kaplan Can, Hatice

    2005-04-01

    The effect of 60Co γ-irradiation on aqueous solutions of poly( N-vinyl-2-pyrrolidone) (PVP) in the presence of persulfate anion has been investigated. The gelation dose of PVP and persulfate containing PVP aqueous solutions has been determined. At low concentrations of persulfate (1.00-3.50%), gelation percentages exhibited a decreasing trend by increasing persulfate content in aqueous solutions of the polymer. The gelation doses of persulfate containing polymer solutions were calculated by the Charlesby-Pinner equation. It was observed that the gelation dose values were shifted to higher values by increasing persulfate concentration in solution. The ratio of the chain scission and crosslinking yields ( G( s)/ G( x)) was also determined. The results showed that the G( s)/ G( x) ratios were smaller than one for PVP aqueous solution system, whereas those obtained for persulfate containing PVP aqueous solutions were higher than unity. The results implied that the chain scission of polymer is more effective than crosslinking in the presence of persulfate. Mechanism of the crosslinking and/or degradation and structure-property relationship of PVP and PVP/persulfate hydrogel systems were investigated by Fourier transformation infeared and thermal analysis (differential scanning calorimetry, thermal gravimetric analysis and differential thermai analysis) methods.

  2. Biocompatible Hydroxylated Boron Nitride Nanosheets/Poly(vinyl alcohol) Interpenetrating Hydrogels with Enhanced Mechanical and Thermal Responses.

    PubMed

    Jing, Lin; Li, Hongling; Tay, Roland Yingjie; Sun, Bo; Tsang, Siu Hon; Cometto, Olivier; Lin, Jinjun; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2017-04-25

    Poly(vinyl alcohol) (PVA) hydrogels with tissue-like viscoelasticity, excellent biocompatibility, and high hydrophilicity have been considered as promising cartilage replacement materials. However, lack of sufficient mechanical properties is a critical barrier to their use as load-bearing cartilage substitutes. Herein, we report hydroxylated boron nitride nanosheets (OH-BNNS)/PVA interpenetrating hydrogels by cyclically freezing/thawing the aqueous mixture of PVA and highly hydrophilic OH-BNNS (up to 0.6 mg/mL, two times the highest reported so far). Encouragingly, the resulting OH-BNNS/PVA hydrogels exhibit controllable reinforcements in both mechanical and thermal responses by simply varying the OH-BNNS contents. Impressive 45, 43, and 63% increases in compressive, tensile strengths and Young's modulus, respectively, can be obtained even with only 0.12 wt% (OH-BNNS:PVA) OH-BNNS addition. Meanwhile, exciting improvements in the thermal diffusivity (15%) and conductivity (5%) can also be successfully achieved. These enhancements are attributed to the synergistic effect of intrinsic superior properties of the as-prepared OH-BNNS and strong hydrogen bonding interactions between the OH-BNNS and PVA chains. In addition, excellent cytocompatibility of the composite hydrogels was verified by cell proliferation and live/dead viability assays. These biocompatible OH-BNNS/PVA hydrogels are promising in addressing the mechanical failure and locally overheating issues as cartilage substitutes and may also have broad utility for biomedical applications, such as drug delivery, tissue engineering, biosensors, and actuators.

  3. Extraordinarily large swelling energy of iodine-treated poly(vinyl alcohol) demonstrated by jump of a film.

    PubMed

    Takamura, Tatsuro; Nozawa, Kazuya; Sugimoto, Yoshiki; Shioya, Masatoshi

    2014-10-15

    Organic material characteristics of volume change and stress generation have attracted the attention of many researchers aiming to develop chemomechanical systems such as artificial muscles and polymer engines having the advantages of high energy density and silent operation. Although polymer gels offer a relatively large actuator stroke, their mechanical properties are relatively poor and the working temperature is relatively low, often limited by the evaporation of liquid if contained. We have developed an iodine-treated poly(vinyl alcohol) having extraordinarily large vapor-induced deswelling stress reaching 59 MPa, which is one to two orders of magnitude greater than those of ordinary polymer gels. Furthermore, this material has extremely large volumetric and gravimetric energy densities reaching 1.3 × 10(6) J m(-3) and 9.6 × 10(2) J kg(-1), respectively, and an elastic modulus of a few GPa and is heat-resistant to at least 200 °C. The high performance of this material can be demonstrated by a jump of a film. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1357-1365.

  4. Effect of Copper Sulfide Nanoparticles on the Optical and Electrical Behavior of Poly(vinyl alcohol) Films

    NASA Astrophysics Data System (ADS)

    Abdullah, Omed Gh.; Saleem, Salwan A.

    2016-11-01

    Polymer nanocomposite films based on poly(vinyl alcohol) (PVA) containing copper sulfide nanoparticles (CuS) were prepared using in situ chemical reduction and casting techniques. The synthesized nanocomposites were analyzed using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope, and ultraviolet-visible spectroscopy. The XRD pattern reveals that the CuS nanoparticles incorporated in the PVA showed a crystalline nature. The observed FTIR band shifts indicate the intermolecular interaction between the CuS nanoparticles and the PVA matrix. The absorbance of nanocomposite samples increased with increasing CuS concentration. The optical band gap energy was estimated using Tauc's formula and it decreased with increasing dopant concentration. The conductivity and dielectric behavior of the samples were studied over the frequency range of 300 Hz to 1 MHz in the temperature range of 30-110°C. The ac conductivity was found to increase with the increase of dopant concentration as well as frequency. Moreover, the variation of frequency exponent ( s) indicated that the conduction mechanism was the correlated barrier hopping model. The experimental results reveal that the optical and electrical performance of PVA can be enhanced dramatically by the addition of a small amount of CuS nanoparticles. This improved properties of the PVA/CuS nanocomposite suggest uses in optoelectronic devices.

  5. Antimicrobial filtration with electrospun poly(vinyl alcohol) nanofibers containing benzyl triethylammonium chloride: Immersion, leaching, toxicity, and filtration tests.

    PubMed

    Park, Jeong-Ann; Kim, Song-Bae

    2017-01-01

    Antimicrobial electrospun poly(vinyl alcohol) (PVA) nanofibers were synthesized by impregnating benzyl triethylammonium chloride (BTEAC) as an antimicrobial agent into PVA nanofibers. The BTEAC-PVA nanofibers were heat-methanol treated during the preparation for various tests. The BTEAC-PVA nanofibers became more hydrophilic than the PVA nanofibers due to incorporation of BTEAC. Through heat-methanol treatment, thermal property, crystallinity, and water stability of BTEAC-PVA nanofibers were improved considerably. The immersion test shows that heat-methanol treatment has an advantage over heat treatment to maintain BTEAC content in BTEAC-PVA nanofibers. The acute toxicity test demonstrates that the 24-h EC50 and 48-h EC50 values (EC50 = median effective concentration) of BTEAC to Daphnia magna were 113 and 90 mg/L, respectively. The leaching test indicates that the BTEAC concentration leached from BTEAC-PVA nanofibers was far below the concentration affecting the immobilization of D. magna. For antimicrobial filtration tests, the BTEAC-PVA nanofibers were deposited onto glass fiber filter. The antimicrobial filtration test was conducted against bacteria (Escherichia coli, Staphylococcus aureus) and bacteriophages (MS2, PhiX174), demonstrating that the BTEAC-PVA nanofibers could enhance the removal of E. coli and S. aureus considerably but not the removal of MS2 and PhiX174 under dynamic flow conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Preparation and characterization of novel biocompatible cryogels of poly (vinyl alcohol) and egg-albumin and their water sorption study.

    PubMed

    Bajpai, A K; Saini, Rajesh

    2006-01-01

    Polyvinyl alcohol (PVA) and egg albumin are water-soluble, biocompatible and biodegradable polymers and have been widely employed in biomedical fields. In this paper, novel physically cross-linked hydrogels composed of poly (vinyl alcohol) and egg albumin were prepared by cyclic freezing/thawing processes of aqueous solutions containing PVA and egg albumin. The FTIR analysis of prepared cryogels indicated that egg albumin was successfully introduced into the formed hydrogel possibly via hydrogen bonds among hydroxyl groups, amide groups and amino groups present in PVA and egg albumin. The gels were also characterized thermally and morphologically by DSC and SEM-techniques, respectively. The prepared so called 'cryogels' were evaluated for their water uptake potential and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The effect of salt solution and various simulated biological fluids on the swelling of cryogel was also studied. The in vitro biocompatibility of the prepared cryogel was also judged by methods such as protein (BSA) adsorption, blood clot formation and percentage hemolysis measurements.

  7. Mediator-free amperometric glucose biosensor based on glucose oxidase entrapped in poly(vinyl alcohol) matrix.

    PubMed

    Guascito, Maria Rachele; Chirizzi, Daniela; Malitesta, Cosimino; Mazzotta, Elisabetta

    2011-01-07

    A simple and novel amperometric biosensor for glucose detection is proposed. It is based on the immobilization of glucose oxidase (GOx) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a platinum electrode surface (Pt/GOx-PVA). Glucose was determined in the absence of a mediator used to transfer electrons between the electrode and the enzyme. The correlation between peak current (i(p)) and scan rate has been verified and the effect of pH solution has been checked. Glucose detection has been performed amperometrically at -400 mV by using pulsed amperometric detection (PAD). Under the selected optimal conditions, the biosensor showed low detection limit (10 μM), wide dynamic range (0.1-37 mM) and high sensitivity. The biosensor amperometric response revealed it to be specific to glucose without significant interference from other sugars and electroactive species coexisting with glucose in biological fluids. Response stability was another interesting feature of the developed system as it was almost completely recovered when the biosensor was left in opportune storage conditions (i.e., a response decrease of only 13% after 35 days in air at room temperature). Finally, X-Ray Photoelectron Spectroscopy (XPS) characterization revealed a homogeneous film deposited on the Pt substrate whose structure is also preserved under operative conditions.

  8. Amperometric ethanol biosensor based on poly(vinyl alcohol)-multiwalled carbon nanotube-alcohol dehydrogenase biocomposite.

    PubMed

    Tsai, Yu-Chen; Huang, Jing-Dae; Chiu, Chian-Cheng

    2007-06-15

    A novel amperometric ethanol biosensor was constructed using alcohol dehydrogenase (ADH) physically immobilized within poly(vinyl alcohol)-multiwalled carbon nanotube (PVA-MWCNT) composite obtained by a freezing-thawing process. It comprises a MWCNT conduit, a PVA binder, and an ADH function. The measurement of ethanol is based on the signal produced by beta-nicotinamide adenine dinucleotide (NADH), the product of the enzymatic reaction. The homogeneity of the resulting biocomposite film was characterized by atomic force microscopy (AFM). The performance of the PVA-MWCNT-ADH biocomposite modified glassy carbon electrode was evaluated using cyclic voltammetry and amperometry in the presence of NADH and in the presence of ethanol. The ethanol content in standard solutions was determined and a sensitivity of 196 nA mM(-1), a linear range up to 1.5mM, and a response time of about 8s were obtained. These characteristics allowed its application for direct detection of ethanol in alcoholic beverages: beer, red wine, and spirit.

  9. Facile fabrication of gold nanoparticles-poly(vinyl alcohol) electrospun water-stable nanofibrous mats: efficient substrate materials for biosensors.

    PubMed

    Wang, Juan; Yao, Hong-Bin; He, Dian; Zhang, Chuan-Ling; Yu, Shu-Hong

    2012-04-01

    Electrospun nanofibrous mats are intensively studied as efficient scaffold materials applied in the fields of tissue engineering, catalysis, and biosensors due to their flexibility and porosity. In this paper, we report a facile route to fabricate gold nanoparticles-poly(vinyl alcohol) (Au NPs-PVA) hybrid water stable nanofibrous mats with tunable densities of Au NPs and further demonstrate the potential application of as-prepared Au NPs-PVA nanofibrous mats as efficient biosensor substrate materials. First, through the designed in situ cross-linkage in coelectrospun PVA-glutaraldehyde nanofibers, water insoluble PVA nanofibrous mats with suitable tensile strength were successfully prepared. Then, 3-mercaptopropyltrimethoxysilane (MPTES) was modified on the surface of obtained PVA nanofibrous films, which triggered successful homogeneous decoration of Au NPs through gold-sulfur bonding interactions. Finally, the Au NPs-PVA nanofibrous mats embedded with horseradish peroxidase (HRP) by electrostatic interactions were used as biosensor substrate materials for H(2)O(2) detection. The fabricated HRP-Au NPs/PVA biosensor showed a highly sensitive detection of H(2)O(2) with a detection limit of 0.5 μM at a signal-to-noise ratio of 3. By modifying other different functional nanaoparticles or enzyme on the PVA nanofibrous film will further expand their potential applications as substrate materials of different biosensors.

  10. Growth mechanism of carbon nanotubes produced by pyrolysis of a composite film of poly (vinyl alcohol) and fly ash

    NASA Astrophysics Data System (ADS)

    Nath, Dilip C. D.; Sahajwalla, Veena

    2011-08-01

    We produced carbon nanotubes (CNTs) by pyrolysis of a composite film of poly (vinyl alcohol) (PVA) with fly ash (FA) at 500°C for 10 min under nitrogen. The composite films were prepared by a suspension of PVA and FA in deionized water and cast onto glass petri dishes. The morphologies of the CNTs were observed in the images of scanning and transmission electron microscopy, showing different types of structures, e.g. whiskers, branches, ropes and graphene sheets. The widths of the CNTs measured varied in the range 18-80 nm. X-ray photoelectron spectroscopy analysis showed five types of carbon binding peaks, C-C/C-H (˜77%), C-O-H (˜9%), -C-O-C (˜5%), C=O (˜5%) and -O-C=O (˜3%). From an image of a broken CNT, a mechanism was proposed for the formation of CNTs. The CNTs grown on FA surfaces have potential for the fabrication of high-strength composite materials with polymer and metal.

  11. Macroporous modified poly (vinyl alcohol) hydrogels with charged groups for tissue engineering: Preparation and in vitro evaluation.

    PubMed

    Drozdova, Maria G; Zaytseva-Zotova, Daria S; Akasov, Roman A; Golunova, Anna S; Artyukhov, Alexander A; Udartseva, Olga O; Andreeva, Elena R; Lisovyy, Denis E; Shtilman, Michael I; Markvicheva, Elena A

    2017-06-01

    Poly(vinyl alcohol) (PVA) hydrogels are widely employed for various biomedical applications, including tissue engineering, due to their biocompatibility, high water solubility, low protein adsorption, and chemical stability. However, non-charged surface of PVA-based hydrogels is not optimal for cell adhesion and spreading. Here, cross-linked macroporous hydrogels based on low molecular weight acrylated PVA (Acr-PVA) was synthesized by modification of the pendant alcohol groups on the PVA with glycidyl methacrylate (GMA). To enhance cell affinity, charged groups were introduced to the hydrogel composition. For this purpose, Acr-PVA was copolymerized with either negatively charged acrylic acid (AA) or positively charged 2-(diethylamino) ethyl methacrylate (DEAEMA) monomers. A surface charge of the obtained hydrogels was found to be in function of the co-monomer type and content. Confocal microscopy observations confirmed that adhesion and spreading of both mouse fibroblasts (L929) and human mesenchymal stem cells (hMSC) on the modified Acr-PVA-AA and Acr-PVA-DEAEMA hydrogels were better than those on the non-modified Acr-PVA hydrogel. The increase of DEAEMA monomer content from 5 to 15mol% resulted in the enhancement of cell viability which was 1.5-fold higher for Acr-PVA-DEAEMA-15 hydrogel than that of the non-modified Acr-PVA hydrogel sample. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Thermodynamic and spectroscopic analysis of the conformational transition of poly(vinyl alcohol) by temperature-dependent FTIR

    NASA Astrophysics Data System (ADS)

    Han, Shan; Luan, Ye-Mei; Pang, Shu-Feng; Zhang, Yun-Hong

    2015-03-01

    The conformational change of poly(vinyl alcohol) has been studied by Fourier transform infrared spectroscopy at various temperatures in the 4000-400 cm-1 region. The molecular motion and the trans/gauche content are sensitive to the Csbnd H, Csbnd C stretching modes. FTIR spectra show that the I2920/I2849 decreases from 1.84 to 1.0 with increasing temperature, companying the decrease in I1047/I1095 from 0.78 to 0.58, implying the conformational transition from trans to gauche in alkyl chain. Based on the van't Hoff relation, the enthalpies and entropies have been calculated in different temperatures, which are 4.61 kJ mol-1 and 15.23 J mol-1 K-1, respectively, in the region of 80-140 °C. From the Cdbnd O stretching mode and Osbnd H band, it can be concluded that the intermolecular hydrogen bonds decrease owing to elevating temperature, which leads to more gauche conformers.

  13. A novel approach for fabricating highly tunable and fluffy bioinspired 3D poly(vinyl alcohol) (PVA) fiber scaffolds.

    PubMed

    Roy, Sunanda; Kuddannaya, Shreyas; Das, Tanya; Lee, Heng Yeong; Lim, Jacob; Hu, Xiao 'Matthew'; Chee Yoon, Yue; Kim, Jaehwan

    2017-06-01

    The excellent biocompatibility, biodegradability and chemo-thermal stability of poly(vinyl alcohol) (PVA) have been harnessed in diverse practical applications. These properties have motivated the fabrication of high performance PVA based nanofibers with adequate control over the micro and nano-architectures and surface chemical interactions. However, the high water solubility and hydrophilicity of the PVA polymer limits the application of the electrospun PVA nanofibers in aqueous environments owing to instantaneous dissolution. In this work, we report a novel yet facile concept for fabricating extremely light, fluffy, insoluble and stable three dimensional (3D) PVA fibrous scaffolds with/without coating for multifunctional purposes. While the solubility, morphology, fiber density and mechanical properties of nanofibers could be tuned by optimizing the cross-linking conditions, the surface chemical reactivity could be readily enhanced by coating with a polydopamine (pDA) bioinspired polymer without compromising the stability and innate properties of the native PVA fiber. The 3D pDA-PVA scaffolds exhibited super dye adsorption and constructive synergistic cell-material interactions by promoting healthy adhesion and viability of the human mesenchymal stem cells (hMSCs) within 3D micro-niches. We foresee the application of tunable PVA 3D as a highly adsorbent material and a scaffold material for tissue regeneration and drug delivery with close consideration of realistic in vivo parameters.

  14. Composite films based on biorelated agro-industrial waste and poly(vinyl alcohol). Preparation and mechanical properties characterization.

    PubMed

    Chiellini, E; Cinelli, P; Imam, S H; Mao, L

    2001-01-01

    As a part of an ongoing project on the production of composite materials based on poly(vinyl alcohol) (PVA) and polymeric materials from renewable resources, the present paper reports on the incorporation of agricultural waste materials as organic fillers in a film matrix based on PVA as continuous phase. In this study lignocellulosic fibers byproducts, derived from sugar cane (SC) and apple (AP) and orange (OR) fruit juice extraction, were cast from PVA aqueous solutions. The effect of fiber type and composition on the relative properties of cast films was evaluated and compared. OR resulted to be suitable for blending in higher amounts by weight than SC and AP. Glycerol and urea were added as plasticizing agents and were observed to be effective in giving flexible films. Additionally, cornstarch was added to further increase the composition of polymers from renewable resources in cost-effective and ecoefficient composite film formulations. The prepared films resulted sensitive to moisture and water. To reduce water sensitivity, hexamethoxymethylmelamine (HMMM) was tested as a cross-linking agent for the present composite formulations. Cross-linked films exhibited significant improvement in water-resistance that can be taken as a tuneable structural feature for customized applications. The mechanical properties of the prepared composite films (elongation at break, tensile strength, Young modulus) were found to be dependent upon the nature and content of the filler and on environmental conditions.

  15. High-Strength Single-Walled Carbon Nanotube/Permalloy Nanoparticle/Poly(vinyl alcohol) Multifunctional Nanocomposite Fiber.

    PubMed

    Zhou, Gengheng; Wang, Yi-Qi; Byun, Joon-Hyung; Yi, Jin-Woo; Yoon, Sang-Su; Cha, Hwa-Jin; Lee, Jea-Uk; Oh, Youngseok; Jung, Byung-Mun; Moon, Ho-Jun; Chou, Tsu-Wei

    2015-11-24

    Magnetic nanocomposite fibers are a topic of intense research due to their potential breakthrough applications such as smart magnetic-field-response devices and electromagnetic interference (EMI) shielding. However, clustering of nanoparticles in a polymer matrix is a recognized challenge for obtaining a property-controllable nanocomposite fiber. Another challenge is that the strength and ductility of the nanocomposite fiber decrease significantly with increased weight loading of magnetic nanoparticles in the fiber. Here, we report high-strength single-walled carbon nanotube (SWNT)/permalloy nanoparticle (PNP)/poly(vinyl alcohol) multifunctional nanocomposite fibers fabricated by wet spinning. The weight loadings of SWNTs and PNPs in the fiber were as high as 12.0 and 38.0%, respectively. The tensile strength of the fiber was as high as 700 MPa, and electrical conductivity reached 96.7 S m(-1). The saturation magnetization (Ms) was as high as 24.8 emu g(-1). The EMI attenuation of a fabric woven from the prepared fiber approached 100% when tested with electromagnetic waves with a frequency higher than 6 GHz. The present study demonstrates that a magnetic-field-response device can be designed using the fabricated multifunctional nanocomposite fiber.

  16. Facile and green fabrication of electrospun poly(vinyl alcohol) nanofibrous mats doped with narrowly dispersed silver nanoparticles

    PubMed Central

    Lin, Song; Wang, Run-Ze; Yi, Ying; Wang, Zheng; Hao, Li-Mei; Wu, Jin-Hui; Hu, Guo-Han; He, Hua

    2014-01-01

    Submicrometer-scale poly(vinyl alcohol) (PVA) nanofibrous mats loaded with aligned and narrowly dispersed silver nanoparticles (AgNPs) are obtained via the electrospinning process from pure water. This facile and green procedure did not need any other chemicals or organic solvents. The doped AgNPs are narrowly distributed, 4.3±0.7 nm and their contents on the nanofabric mats can be easily tuned via in situ ultraviolet light irradiation or under preheating conditions, but with different particle sizes and size distributions. The morphology, loading concentrations, and dispersities of AgNPs embedded within PVA nanofiber mats are characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible spectra, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. Moreover, the biocidal activities and cytotoxicity of the electrospun nanofiber mats are determined by zone of inhibition, dynamic shaking method, and cell counting kit (CCK)-8 assay tests. PMID:25170264

  17. Improved biocomposite development of poly(vinyl alcohol) and hydroxyapatite for tissue engineering scaffold fabrication using selective laser sintering.

    PubMed

    Wiria, Florencia Edith; Chua, Chee Kai; Leong, Kah Fai; Quah, Zai Yan; Chandrasekaran, Margam; Lee, Mun Wai

    2008-03-01

    In scaffold guided tissue engineering (TE), temporary three-dimensional scaffolds are essential to guide and support cell proliferation. Selective Laser Sintering (SLS) is studied for the development of such scaffolds by eliminating pore spatial control problems faced in conventional scaffolds fabrication methods. SLS offers good user control over the scaffold's microstructures by adjusting its main processing parameters, namely the laser power, scan speed and part bed temperature. This research focuses on the improvements in the fabrication of TE scaffolds using SLS with powder biomaterials, namely hydroxyapatite (HA) and poly(vinyl alcohol) (PVA). Grinding of as-received PVA powder to varying particle sizes and two methods of mixing are investigated as the preparation process to determine a better mixing method that would enhance the mixture homogeneity. Suitable sintering conditions for the improved biocomposite are then achieved by varying the important process parameters such as laser power, scan speed and part bed temperature.SLS fabricated samples are characterized using Fourier Transform Infrared Spectrometer (FTIR) and Scanning Electron Microscope (SEM). FTIR results show that the grinding and sintering processes neither compromise the chemical composition of the PVA nor cause undue degradation. Visual analysis of the grinding, powder mixing and sintering effect are carried out with SEM. The SEM observations show improvements in the sintering effects. The favorable outcome ascertains PVA/HA biocomposite as a suitable material to be processed by SLS for TE scaffolds.

  18. Poly(methyl vinyl ether-alt-maleic acid)-functionalized porous silicon nanoparticles for enhanced stability and cellular internalization.

    PubMed

    Shahbazi, Mohammad-Ali; Almeida, Patrick V; Mäkilä, Ermei; Correia, Alexandra; Ferreira, Mónica P A; Kaasalainen, Martti; Salonen, Jarno; Hirvonen, Jouni; Santos, Hélder A

    2014-03-01

    Currently, developing a stable nanocarrier with high cellular internalization and low toxicity is a key bottleneck in nanomedicine. Here, we have developed a successful method to covalently conjugate poly(methyl vinyl ether-co-maleic acid) (PMVE-MA) copolymer on the surface of (3-aminopropyl)triethoxysilane-functionalized thermally carbonized porous silicon nanoparticles (APSTCPSi NPs), forming a surface negatively charged nanovehicle with unique properties. This polymer conjugated NPs could modify surface smoothness, charge, and hydrophilicity of the developed NPs, leading to considerable improvement in the colloidal and plasma stabilities via enhanced suspensibility and charge repulsion. Furthermore, despite the surface negative charge of the polymer-conjugated NPs, the cellular internalization was increased in both MDA-MB-231 and MCF-7 breast cancer cells. These results provide a proof-of-concept evidence that such polymer-based PSi nanocomposite can be extensively used as a promising candidate for intracellular drug delivery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    PubMed

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

    2015-09-14

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

  20. Manufacturing scale-up of electrospun poly(vinyl alcohol) fibers containing tenofovir for vaginal drug delivery

    PubMed Central

    Krogstad, Emily A.; Woodrow, Kim A.

    2014-01-01

    Electrospun fibers containing antiretroviral drugs have recently been investigated as a new dosage form for topical microbicides against HIV-1. However, little work has been done to evaluate the scalability of the fiber platform for pharmaceutical production of medical fabrics. Scalability and cost-effectiveness are essential criteria in developing fibers as a practical platform for use as a microbicide and for translation to clinical use. To address this critical gap in the development of fiber-based vaginal dosage forms, we assessed the scale-up potential of drug-eluting fibers delivering tenofovir (TFV), a nucleotide reverse transcriptase inhibitor and lead compound for topical HIV-1 chemoprophylaxis. Here we describe the process of free-surface electrospinning to scale up production of TFV fibers, and evaluate key attributes of the finished products such as fiber morphology, drug crystallinity, and drug loading and release kinetics. Poly(vinyl alcohol) (PVA) containing up to 60 wt% TFV was successfully electrospun into fibers using a nozzle-free production-scale electrospinning instrument. Actual TFV loading in fibers increased with increasing weight percent TFV in solution, and encapsulation efficiency was improved by maintaining TFV solubility and preventing drug sedimentation during batch processing. These results define important solution and processing parameters for scale-up production of TFV drug-eluting fibers by wire electrospinning, which may have significant implications for pharmaceutical manufacturing of fiber-based medical fabrics for clinical use. PMID:25169075