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Sample records for alcohol pva polymer

  1. Fabrication and operation of a system for the PVA (polyvinyl alcohol) coating of polymer microshells with trace gas fill

    SciTech Connect

    King, K.J.

    1988-03-31

    Polymer microshells with a PVA (polyvinyl alcohol) coating are produced for the ICF Program by the Fusion Target Fabrication (FTF) Group at Lawrence Livermore National Laboratories. A PVA coating greatly reduces the permeation of gas through a polymer microshell. The equipment and procedures used in the production of PVA coated microshells are discussed. 6 figs.

  2. Electrical Conductivity Study of Polymer Electrolyte Magnetic Nanocomposite Based Poly(Vinyl) Alcohol (PVA) Doping Lithium and Nickel Salt

    NASA Astrophysics Data System (ADS)

    Aji, Mahardika Prasetya; Rahmawati, Silvia, Bijaksana, Satria; Khairurrijal, Abdullah, Mikrajuddin

    2010-10-01

    Composite polymer electrolyte magnetic systems composed of poly(vinyl) alcohol (PVA) as the host polymer, lithium and nickel salt as dopant were studied. The effect upon addition of lithium ions in polimer PVA had been enhanced conductivity with the increase of lithium concentration. The conductivity values were 1.19x10-6, 1.25x10-5, 4.89x-5, 1.88x10-4, and 1.33x10-3 Sṡcm-1 for pure PVA and 1%, 3%, 5% and 7% LiOH complexed PVA, respectively. Meanwhile, the addition nickel salt into polymer electrolyte PVA-LiOH does not significantly change of conductivity value, on order 10-3 Sṡcm-1. The ionic transport is dominantly regarded by Li+ ions present in polymer electrolyte magnetic because the atomic mass Li+ is smaller than Ni2+. The absence of external magnetic field in polimer electrolyte magnetic causes the existence Ni2+ ions not significantly affected of conductivity.

  3. Modifying Poly(Vinyl Alcohol) (PVA) from Insulator to Small-Bandgap Polymer: A Novel Approach for Organic Solar Cells and Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Aziz, Shujahadeen B.

    2016-01-01

    An innovative method has been used to reduce the bandgap of poly(vinyl alcohol) (PVA) polymer by addition of a nontoxic, inexpensive, and environmentally friendly material. The resulting materials are small-bandgap polymers, hence opening new frontiers in green chemistry. The doped PVA films showed a wide range of light absorption of the solar spectrum from 200 nm to above 800 nm. Nonsharp absorption behavior versus wavelength was observed for the samples. The refractive index exhibited a wide range of dispersion. Shift of the absorption edge from 6.2 eV to 1.5 eV was observed. The energy bandgap of PVA was diminished to 1.85 eV upon addition of black tea extract solution, lying in the range of small-bandgap polymers. Increase of the optical dielectric constant was observed with increasing tea solution addition. The results indicate that small-bandgap PVA with good film-forming ability could be useful in terms of cost-performance tradeoff, solving problems of short lifetime, cost, and flexibility associated with conjugated polymers. The decrease of the Urbach energy upon addition of black tea extract solution indicates modification of PVA from a disordered to ordered material. X-ray diffraction results confirm an increase of the crystalline fraction in the doped samples.

  4. Proton Conducting Polymer Electrolyte Based on Pva-Pan

    NASA Astrophysics Data System (ADS)

    Devi, S. Siva; Selvasekarapandian, S.; Rajeswari, N.; Genova, F. Kingslin Mary; Karthikeyan, S.; Raja, C. Sanjeevi

    2013-07-01

    Proton conducting polymer electrolytes based on blend polymer using Poly Vinyl Alcohol (PVA) and Poly Acrylo Nitrile (PAN) doped with ammonium nitrate have been prepared by solution casting method. The highest conductivity at room temperature (305K) has been found to be 1.8×10-3 S cm-1 for 15 mole % NH4NO3 doped PVA-PAN system. X ray Diffraction pattern of the doped and the undoped blend polymer electrolyte confirms the amorphous nature of blend polymer, when salt is added. The complex formation between the blend polymer and the salt has been confirmed by Fourier transform infrared spectroscopy.

  5. Spectral studies of Donepezil release from streched PVA polymer films

    NASA Astrophysics Data System (ADS)

    Nechifor, Cristina-Delia; Zelinschi, Carmen-Beatrice; Stoica, Iuliana; Closca, Valentina; Dorohoi, Dana-Ortansa

    2013-07-01

    The focus of this research is to obtain poly vinyl alcohol (PVA) polymer foils containing Donepezil in different concentration, in order to be used in controlled drug release as a palliative treatment of mild to moderate Alzheimer's disease. The influence of polymeric foil stretching degree on drug release was analyzed using spectral measurements.

  6. Effects of PVA(Polyvinyl Alcohol) on Supercooling Phenomena of Water

    NASA Astrophysics Data System (ADS)

    Kumano, Hiroyuki; Saito, Akio; Okawa, Seiji; Takizawa, Hiroshi

    In this paper, effects of polymer additive on supercooling of water were investigated experimentally. Poly-vinyl alcohol (PVA) were used as the polymer, and the samples were prepared by dissolving PVA in ultra pure water. Concentration, degree of polymerization and saponification of PVA were varied as the experimental parameters. The sample was cooled, and the temperature at the instant when ice appears was measured. Since freezing of supercooled water is statistical phenomenon, many experiments were carried out and average degrees of supercooling were obtained for each experimental condition. As the result, it was found that PVA affects nucleation of supercooling and the degree of supercooling increases by adding the PVA. Especially, it is found that the average degree of supercooling increases and the standard deviation of average degree of supercooling decreases with increase of degree of saponification of PVA. However, the average degree of supercooling are independent of the degree of polymerization of PVA in the range of this study.

  7. Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea.

    PubMed

    Jiang, Hong; Zuo, Yi; Zhang, Li; Li, Jidong; Zhang, Aiming; Li, Yubao; Yang, Xiaochao

    2014-03-01

    Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt. PMID:24464723

  8. Electrical properties of starch-PVA biodegradable polymer blend

    NASA Astrophysics Data System (ADS)

    Chatterjee, B.; Kulshrestha, N.; Gupta, P. N.

    2015-02-01

    Solid polymer electrolyte films were prepared by adding different contents of potassium chloride (KCl) in a polymer matrix composed of two versatile biodegradable polymers: starch and polyvinyl alcohol (PVA), using the solution cast method. The complexation of the added salt (KCl) with the polymer matrix was confirmed from an x-ray diffraction study (XRD). The evolution of a smooth and uniform morphology with the increasing content of KCl was confirmed from scanning electron microscopy (SEM). The transference number measurement established ions as the dominant charge carriers in the system. The maximum ionic conductivity ˜5.44 × 10-5 S cm-1 at ambient conditions was obtained for the film with 1.5 wt% of KCl using complex impedance spectroscopy. The ionic conductivity and dielectric constant increased with the salt content, thus affirming the amplification in the number of charge carriers. The noteworthy aspect of the investigation is the observation of appreciable ionic conductivity at a relatively low salt content. Low values of activation energy obtained from temperature-dependent ionic conductivity could be favorable from the point of view of the application. Electric modulus studies confirmed the absence of electrode polarization effects in the polymer electrolyte films. The scaling of the electric modulus shows a distribution of relaxation times in the polymer electrolyte films. The study unveils the efficiency of the starch-PVA blend, with glycerol and citric acid as additives, as a hopeful material for preparing biodegradable solid polymer electrolyte films.

  9. Isolation and characterization of a novel poly(vinyl alcohol)-degrading bacterium, Sphingopyxis sp. PVA3.

    PubMed

    Yamatsu, Atsushi; Matsumi, Rie; Atomi, Haruyuki; Imanaka, Tadayuki

    2006-10-01

    We have isolated a poly(vinyl alcohol) (PVA)-degrading bacterium from an activated sludge sample obtained from the drainage of a dyeing factory. Enrichment cultures were performed in media containing PVA as the sole or major carbon source. After several rounds of cultivation on liquid and solid media, we were able to isolate a single colony with PVA-degrading ability (strain PVA3). The bacterium could degrade PVA in the absence of symbionts or cofactors such as pyrroloquinoline quinone (PQQ). Over 90% of PVA, at an initial concentration of 0.1%, was degraded within a 6-day cultivation. Degradation was confirmed by both iodometric methods and gel permeation chromatography. Examination of the PVA attached to the cells revealed a large increase in carbonyl groups, suggesting the oxidation of hydroxyl groups of the polymer on the surfaces of cells. Addition of PQQ to the culture medium did not enhance the growth and the PVA-degrading rates of strain PVA3. Furthermore, we found that cells grown on PVA generated hydrogen peroxide upon the addition of PVA. The results strongly suggest that the initial oxidation of PVA is mediated via a PVA oxidase, and not a PQQ-dependent dehydrogenase. A biochemical and phylogenetic characterization of the bacterium was performed. The sequence of the 16S ribosomal RNA gene of the bacterium indicated a phylogenetic position of the strain within the genus Sphingopyxis, and the strain was therefore designated Sphingopyxis sp. PVA3. PMID:16583228

  10. Luminescence study of ZnSe/PVA (polyvinyl alcohol) composite film

    NASA Astrophysics Data System (ADS)

    Lahariya, Vikas

    2016-05-01

    The ZnSe nanocrystals have been prepared into poly vinyl alcohol(PVA) polymer matrix on glass using ZnCl2 and Na2SeSO3 as zinc and selenium source respectively. Poly vinyl Alcohol (PVA) used as polymer matrix cum capping agent due to their high viscosity and water solubility. It is transparent for visible region and prevents Se- ions to photo oxidation. The ZnSe/PVA composite film was deposited on glass substrate. The film was characterized by X Ray Diffraction (XRD) and UV-Visible absorption Spectroscopy and Photoluminescence. The X Ray Diffraction (XRD) study confirms the nanometer size (10 nm) particle formation within PVA matrix with cubic zinc blend crystal structure. The UV-Visible Absorption spectrum of ZnSe/PVA composite film shown blue shift in absorption edge indicating increased band gap due to quantum confinement. The calculated energy band gap from the absorption edge using Tauc relation is 3.4eV. From the Photoluminescence study a broad peak at 435 nm has been observed in violet blue region due to recombination of surface states.

  11. AC conductivity and electrochemical studies of PVA/PEG based polymer blend electrolyte films

    NASA Astrophysics Data System (ADS)

    Polu, Anji Reddy; Kumar, Ranveer; Dehariya, Harsha

    2012-06-01

    Polymer blend electrolyte films based on Polyvinyl alcohol(PVA)/Poly(ethylene glycol)(PEG) and magnesium nitrate (Mg(NO3)2) were prepared by solution casting technique. Conductivity in the temperature range 303-373 K and transference number measurements have been employed to investigate the charge transport in this polymer blend electrolyte system. The highest conductivity is found to be 9.63 × 10-5 S/cm at 30°C for sample with 30 weight percent of Mg(NO3)2 in PVA/PEG blend matrix. Transport number data shows that the charge transport in this polymer electrolyte system is predominantly due to ions. Using this electrolyte, an electrochemical cell with configuration Mg/(PVA+PEG+Mg(NO3)2)/(I2+C+electrolyte) was fabricated and its discharge characteristics profile has been studied.

  12. Closantel nano-encapsulated polyvinyl alcohol (PVA) solutions.

    PubMed

    Vega, Abraham Faustino; Medina-Torres, Luis; Calderas, Fausto; Gracia-Mora, Jesus; Bernad-Bernad, MaJosefa

    2016-08-01

    The influence of closantel on the rheological and physicochemical properties (particle size and by UV-Vis absorption spectroscopy) of PVA aqueous solutions is studied here. About 1% PVA aqueous solutions were prepared by varying the closantel content. The increase of closantel content led to a reduction in the particle size of final solutions. All the solutions were buffered at pH 7.4 and exhibited shear-thinning behavior. Furthermore, in oscillatory flow, a "solid-like" type behavior was observed for the sample containing 30 μg/mL closantel. Indicating a strong interaction between the dispersed and continuous phases and evidencing an interconnected network between the nanoparticle and PVA, this sample also showed the highest shear viscosity and higher shear thinning slope, indicating a more intrincate structure disrupted by shear. In conclusion, PVA interacts with closantel in aqueous solution and the critical concentration for closantel encapsulation by PVA was about 30 μg/mL; above this concentration, the average particle size decreased notoriously which was associated to closantel interacting with the surface of the PVA aggregates and thus avoiding to some extent direct polymer-polymer interaction. PMID:26330226

  13. Novel Starch-PVA Polymer for Microparticle Preparation and Optimization Using Factorial Design Study

    PubMed Central

    Chattopadhyay, Helen; De, Amit Kumar; Datta, Sriparna

    2015-01-01

    The aim of our present work was to optimize the ratio of a very novel polymer, starch-polyvinyl alcohol (PVA), for controlled delivery of Ornidazole. Polymer-coated drug microparticles were prepared by emulsion method. Microscopic study, scanning electron microscopic study, and atomic force microscopic study revealed that the microparticles were within 10 micrometers of size with smooth spherical shape. The Fourier transform infrared spectroscopy showed absence of drug polymer interaction. A statistical 32 full factorial design was used to study the effect of different concentration of starch and PVA on the drug release profile. The three-dimensional plots gave us an idea about the contribution of each factor on the release kinetics. Hence this novel polymer of starch and polyvinyl alcohol can be utilized for control release of the drug from a targeted delivery device. PMID:27347511

  14. The development of polyvinyl alcohol (PVA) fibers

    SciTech Connect

    Zheng, Q.; Morgan, R.J.; Cunniff, P.

    1996-12-31

    The conditions for gel-spinning and hot drawing of PVA fibers have been investigated and the effects of simultaneous orientation and chemical crosslinking in hot water and other solution environments studied. Fibers with high tenacities ({approximately}30 g/d) were produced but more precise control of spinning conditions will be required to obtain consistent high fiber tenacities. The fiber mechanical energy absorption can be further enhanced by boiling water exposure that causes additional crystallization and, also, disorientation of the fiber amorphous regions that results in a softer but high energy absorbing PVA fiber with 30-60% greater failure strain without any compromise in fiber strength. Such treated fibers have the potential to exhibit superior ballistic resistance and cost advantage relative to other fibers.

  15. 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.

  16. 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.

  17. Anammox sludge immobilized in polyvinyl alcohol (PVA) cryogel carriers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluated the use of polyvinyl alcohol (PVA) cryogels to encapsulate slow-growing anammox bacteria for deammonification treatment of wastewater. The cryogel pellets were prepared by a freezing-thawing procedure at -8 oC. On average, pellets contained 11.8 mg TSS/g-pellet of enriched anamm...

  18. Characterization of proton conducting blend polymer electrolyte using PVA-PAN doped with NH4SCN

    NASA Astrophysics Data System (ADS)

    Premalatha, M.; Mathavan, T.; Selvasekarapandian, S.; Genova, F. Kingslin Mary; Umamaheswari, R.

    2016-05-01

    Polymer electrolytes with proton conductivity based on blend polymer using polyvinyl alcohol (PVA) and poly acrylo nitrile (PAN) doped with ammonium thiocyanate have been prepared by solution casting method using DMF as solvent. The complex formation between the blend polymer and the salt has been confirmed by FTIR Spectroscopy. The amorphous nature of the blend polymer electrolytes have been confirmed by XRD analysis. The highest conductivity at 303 K has been found to be 3.25 × 10-3 S cm-1 for 20 mol % NH4SCN doped 92.5PVA:7.5PAN system. The increase in conductivity of the doped blend polymer electrolytes with increasing temperature suggests the Arrhenius type thermally activated process. The activation energy is found to be low (0.066 eV) for the highest conductivity sample.

  19. Impedance studies of a green blend polymer electrolyte based on PVA and Aloe-vera

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, S.; Mathavan, T.; Vijaya, N.; Selvasekarapandian, Premalatha, M.; Monisha, S.

    2016-05-01

    The development of polymer electrolyte materials for energy generating and energy storage devices is a challenge today. A new type of blended green electrolyte based on Poly-vinyl alcohol (PVA) and Aloe-vera has been prepared by solution casting technique. The blending of polymers may lead to the increase in stability due to one polymer portraying itself as a mechanical stiffener and the other as a gelled matrix supported by the other. The prepared blend electrolytes were subjected to Ac impedance studies. It has been found out that the polymer film in which 1 gm of PVA was dissolved in 40 ml of Aloe-vera extract exhibits highest conductivity and its value is 3.08 × 10-4 S cm-1.

  20. Rhizobia survival in seeds coated with polyvinyl alcohol (PVA) electrospun nanofibres.

    PubMed

    Damasceno, Raquel; Roggia, Isabel; Pereira, Claudio; de Sá, Enilson

    2013-11-01

    The electrospinning technique of rhizobia immobilization in nanofibres is an innovative and promising alternative for reducing the harmful effects of environmental stress on bacteria strains in a possible inoculant nanotechnology product for use in agriculture. The use of polyvinyl alcohol (PVA) shows up as an effective polymer in cell encapsulation because of its physical characteristics, such as viscosity and power of scattering. The aim of these studies has been to evaluate the survival of rhizobia incorporated in PVA nanofibres, which were applied to soybean seed and then subjected to different storage times and exposure to fungicide. The maintenance of the symbiotic characteristics of the incorporated bacterial strains was also evaluated, noting the formation of nodules in the soybean seedlings. No significant differences in the cell survival at 0 h and after 24 h of storage were observed. After 48 h, a significant difference in the bacterial cell concentration of the seeds affixed with PVA nanofibres was observed. Exposure to the fungicide decreased the viability of the bacteria strains even when coated with the nanofibres. A larger number of nodules formed in soybean seedlings from seeds inoculated with rhizobia incorporated in PVA nanofibres than from seeds inoculated with rhizobia without PVA. Thus, the electrospinning technique is a great alternative to the usual protector inoculants because of its unprecedented capacity to control the release of bacteria. PMID:24206353

  1. Lithium Ion Polymer Electrolyte Based on Pva-Pan

    NASA Astrophysics Data System (ADS)

    Genova, F. Kingslin Mary; Selvasekarapandian, S.; Rajeswari, N.; Devi, S. Siva; Karthikeyan, S.; Raja, C. Sanjeevi

    2013-07-01

    The polymer blend electrolytes based on polyvinylalcohol(PVA) and polyacrylonitrile (PAN) doped with lithium per chlorate (LiClO4) have been prepared by solution casting technique using DMF as solvent. The complex formation between blend polymer and the salt has been confirmed by Fourier transform infrared spectroscopy. The amorphous nature of the blend polymer electrolyte has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared blend polymer electrolyte has been found by ac impedence spectroscopic analysis. The highest ionic conductivity has been found to be 5.0 X10-4 S cm -1 at room temperature for 92.5 PVA: 7.5PAN: 20 molecular wt. % of LiClO4. The effect of salt concentration on the conductivity of the blend polymer electrolyte has been discussed.

  2. Microstructural and electrical properties of PVA/PVP polymer blend films doped with cupric sulphate

    NASA Astrophysics Data System (ADS)

    Hemalatha, K.; Mahadevaiah, Gowtham, G. K.; Urs, G. Thejas; Somashekarappa, H.; Somashekar, R.

    2016-05-01

    A series of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) polymer blends added with different concentrations of cupric sulphate (CuSO4) were prepared by solution casting method and were subjected to X-ray diffraction (XRD) and Ac conductance measurements. An attempt has been made to study the changes in crystal imperfection parameters in PVA/PVP blend films with the increase in concentration of CuSO4. Results show that decrease in micro crystalline parameter values is accompanied with increase in the amorphous content in the film which is the reason for film to have more flexibility, biodegradability and good ionic conductivity. AC conductance measurements in these films show that the conductivity increases as the concentration of CuSO4 increases. These films were suitable for electro chemical applications.

  3. Crystal structures and magnetic properties of magnetite (Fe3O4)/Polyvinyl alcohol (PVA) ribbon

    NASA Astrophysics Data System (ADS)

    Ardiyanti, Harlina; Suharyadi, Edi; Kato, Takeshi; Iwata, Satoshi

    2016-04-01

    Ribbon of magnetite (Fe3O4)/Polyvinyl Alcohol (PVA) nanoparticles have been successfully fabricated with various concentration of PVA synthesized by co-precipitation method. Particle size of nanoparticles Fe3O4 sample and ribbon Fe3O4/PVA 25% sample is about 9.34 nm and 11.29 nm, respectively. The result of Vibrating Sample Magnetometer (VSM) showed that saturation magnetization value decreased from 76.99 emu/g to 15.01 emu/g and coercivity increased from 49.30 Oe to 158.35 Oe as increasing concentration of PVA. Atomic Force Microscopy (AFM) analysis showed that encapsulated PVA given decreasing agglomeration, controlled shape of nanoparticles Fe3O4 more spherical and dispersed. Surface roughness decreased with increasing concentration of PVA.

  4. Ionic conductivity studies in crystalline PVA/NaAlg polymer blend electrolyte doped with alkali salt KCl

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Potassium Chloride (KCl) doped poly(vinyl alcohol) (PVA)/sodium alginate (NaAlg) in 60:40 wt% polymer blend electrolytes were prepared by solution casting method. The complexation of KCl with host PVA/NaAlg blend is confirmed by FTIR and UV-Vis spectra. The XRD studies show that the crystallinity of the prepared blends increases with increase in doping. The dc conductivity increases with increase in dopant concentration. Temperature dependent dc conductivity shows an Arrhenius behavior. The dielectric properties show that both the dielectric constant and dielectric loss increases with increase in KCl doping concentration and decreases with frequency. The cole-cole plots show a decrease in bulk resistance, indicates the increase in ac conductivity, due to increase in charge carrier mobility. The doping of KCl enhances the mechanical properties of PVA/NaAlg, such as Young's modulus, tensile strength, stiffness.

  5. Spectroscopic properties of (PVA+ZnO):Mn{sup 2+} polymer films

    SciTech Connect

    Rani, Ch.; Raju, D. Siva; Bindu, S. Hima; Krishna, J. Suresh; Raju, Ch. Linga

    2015-05-15

    Electron Paramagnetic Resonance (EPR), optical absorption and infrared spectral studies have been carried out on Mn{sup 2+} ions doped in poly(vinyl alcohol) complexed with zinc oxide polymer films prepared by solution cast technique. The EPR spectra of 1 mol% Mn{sup 2+} ions doped polymer complex (PVA+ZnO) at room temperature exhibit sextet hyperfine structure (hfs), centered at 2.01. The spin-Hamiltonian parameter values indicate that the ground state of Mn{sup 2+} ion in d{sup 5} and the site symmetry around Mn{sup 2+} ions in tetragonally distorted octa hedral site. The optical absorption spectra exhibits two bands centered at 275nm at 437nm. The FTIR spectrum exhibits bands characteristic of stretching and banding vibrations of O-H, C-H and C=C groups.

  6. 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.

  7. Synthesis and characterization of alkaline polyvinyl alcohol and poly(epichlorohydrin) blend polymer electrolytes and performance in electrochemical cells

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Lin, Sheng-Jen; Hsu, Sung-Ting

    Alkaline SPE was obtained from a blend of polyvinyl alcohol (PVA) and poly(epichlorohydrin) (PECH), PVA-PECH, by a solution-cast technique. The PVA host polymer is blended with PECH polymer to provide a polymer electrolyte with improved chemical and mechanical properties. The ionic conductivity of the PVA-PECH polymer electrolytes is between 10 -2 and 10 -3 S cm -1 at room temperature when the blend ratio is varied from 1:0.2 to 1:1. The PVA-PECH polymer was characterized by means of scanning electron microscopy, X-ray diffraction, stress-strain test, cyclic voltammetry, and a.c. impedance spectroscopy. It is found that the polymer electrolytes exhibit good mechanical strength and excellent chemical stability. The electrochemical performance of solid-state Zn-air batteries with various types of the blended polymer electrolyte films is examined by a galvanostatic discharge method.

  8. Electrical behavior of polymer hydrogel composed of poly(vinyl alcohol)/hyaluronic acid in solution

    NASA Astrophysics Data System (ADS)

    Kim, Seon Jeong; Yoon, Seoung Gil; Park, Sang Jun; Lee, Chang Kee; Shin, Su Ryon; Lee, Young Moo; Kim, In Young; Kim, Sun I.

    2003-07-01

    Interpenetrating polymer networks (IPN) composed of poly(vinyl alcohol) (PVA) and hyaluronic acid (HA) were prepared and exhibited electrical sensitive behavior. The swelling behavior of the PVA/HA IPN was studied by immersion of the gel in aqueous NaCl solutions at various concentrations and pHs. Also, the stimuli response of the PVA/HA IPN in electric fields was investigated. When swollen IPN was placed between a pair of electrodes, the PVA/HA IPN exhibited bending behavior upon the application of an electric field. The PVA/HA IPN also showed stepwise bending behavior depending on the electric stimulus. Also, for using biomedical application, the bending behavior of PVA/HA IPN has been studied in hank"s solution at pH 7.4

  9. Study of parallel oriented electrospun polyvinyl alcohol (PVA) nanofibers using modified electrospinning method

    NASA Astrophysics Data System (ADS)

    Yusuf, Yusril; Ula, Nur Mufidatul; Jahidah, Khannah; Kusumasari, Ervanggis Minggar; Triyana, Kuwat; Sosiati, Harini; Harsojo

    2016-04-01

    Parallel orientedpolyvinyl alcohol (PVA) nanofibershasbeen successfully prepared by using modified electrospinning method. This method uses two pairs of copper (Cu) electrodes which are set apart at a certain distance and applied voltage of 15 kV. The concentrations of PVA were varied from 11%, 13%, 15%, 17%, and 19%. The width of gap collector were varied from 5 mm, 10 mm, 15 mm, and 20 mm. The diameter of nanofibers increase as increasing concentration of PVA. As the width of gap collector increase, first diameter of nanofibers decrease and reach a minimum value at 355 ± 7nm in 15 mm of gap, then the diameters increase again. We also calculated the alignment parameter (S) for given aligned nanofiber. The result showed that alignment parameters (S) were on values around 0,9-1.

  10. Alkaline composite PEO-PVA-glass-fibre-mat polymer electrolyte for Zn-air battery

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Lin, Sheng-Jen

    An alkaline composite PEO-PVA-glass-fibre-mat polymer electrolyte with high ionic conductivity (10 -2 S cm -1) at room temperature has been prepared and applied to solid-state primary Zn-air batteries. The electrolyte shows excellent mechanical strength. The electrochemical characteristics of the batteries were experimentally investigated by means of ac impedance spectroscopy and galvanostatic discharge. The results indicate that the PEO-PVA-glass-fibre-mat composite polymer electrolyte is a promising candidate for application in alkaline primary Zn-air batteries.

  11. Functional data analysis of experimental parameters obtained in PVA doped CdCl2 polymer composites

    NASA Astrophysics Data System (ADS)

    Prakash, M. B. Nanda; Urs, Gopal Krishne; Somashekar, R.

    2016-05-01

    Using solution casting method, PVA based polymer composites films with various concentrations of CdCl2 were prepared. Prepared polymer composites films were investigated using XRD. Crystallite size for different concentrations of CdCl2 are computed here using Williamson and Hall plot (WH plot), an in-house program developed by us. To correlate between two independent physical parameters size and conductivity, we have chosen functional data analysis to estimate the maxima and minima in these polymer composites systems.

  12. A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete

    PubMed Central

    Karadelis, John N.; Lin, Yougui

    2015-01-01

    This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6]. PMID:26306313

  13. A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete.

    PubMed

    Karadelis, John N; Lin, Yougui

    2015-09-01

    This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6]. PMID:26306313

  14. Improvement of mechanical robustness of the superhydrophobic wood surface by coating PVA/SiO2 composite polymer

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Wang, Shuliang; Zhang, Ming; Ma, Miaolian; Wang, Chengyu; Li, Jian

    2013-09-01

    Improvement of the robustness of superhydrophobic surfaces is crucial for the purpose of achieving commercial applications of these surfaces in such various areas as self-cleaning, water repellency and corrosion resistance. We have investigated a fabrication of polyvinyl alcohol (PVA)/silica (SiO2) composite polymer coating on wooden substrates with super repellency toward water, low sliding angles, low contact angle hysteresis, and relatively better mechanical robustness. The composite polymer slurry, consisting of well-mixing SiO2 particles and PVA, is prepared simply and subsequently coated over wooden substrates with good adhesion. In this study, the mechanical robustness of superhydrophobic wood surfaces was evaluated. The effect of petaloid structures of the composite polymer on robustness was investigated using an abrasion test and the results were compared with those of superhydrophobic wood surfaces fabricated by other processes. The produced wood surfaces exhibited promising superhydrophobic properties with a contact angle of 159̊ and a sliding angle of 4̊, and the relatively better mechanical robustness.

  15. The role of MgBr2 to enhance the ionic conductivity of PVA/PEDOT:PSS polymer composite

    PubMed Central

    Sheha, Eslam M.; Nasr, Mona M.; El-Mansy, Mabrouk K.

    2014-01-01

    A solid polymer electrolyte system based on poly(vinyl alcohol) (PVA) and poly(3,4-Etylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) complexed with magnesium bromide (MgBr2) salt was prepared using solution cast technique. The ionic conductivity is observed to increase with increasing MgBr2 concentration. The maximum conductivity was found to be 9.89 × 10−6 S/cm for optimum polymer composite film (30 wt.% MgBr2) at room temperature. The increase in the conductivity is attributed to the increase in the number of ions as the salt concentration is increased. This has been proven by dielectric studies. The increase in conductivity is also attributable to the increase in the fraction of amorphous region in the electrolyte films as confirmed by their structural, thermal, electrical and optical properties. PMID:26199746

  16. X-ray irradiation-induced changes in (PVA-PEG-Ag) polymer nanocomposites films

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Benthami, K.; Abutalib, M. M.

    2016-02-01

    The effects of X-ray irradiation on the structural, thermal and optical properties of polyvinyl alcohol-polyethylene glycol-silver (PVA-PEG-Ag) nanocomposites have been investigated. The samples of nanocomposites were prepared by adding Ag nanoparticles with 5 wt% to the (PVA-PEG) blend. The films of 0.05 mm thickness were prepared by the casting method. These films were irradiated with X-ray doses ranging from 20 to 200 kGy. The resultant effect of X-ray irradiation on the structural properties of PVA-PEG-Ag has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy. Also, thermal property studies were carried out using thermogravimetric analysis. Further, the transmission of the PVA-PEG-Ag samples and any color changes were studied. Fourier transform infrared spectroscopy measurements showed that the crosslinking is the dominant mechanism at the dose range 50-200 kGy. This led to a more compact structure of PVA-PEG-Ag samples, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. Moreover, the color intensity ΔE was greatly increased with an increase in the dose, and was accompanied by a significant increase in the yellow color component.

  17. TiO2 and polyvinyl alcohol (PVA) coated polyester filter in bioreactor for wastewater treatment.

    PubMed

    Liu, Lifen; Zhao, Chuanqi; Yang, Fenglin

    2012-04-15

    Prepared by coating TiO(2)/polyvinyl alcohol (PVA) on a low cost polyester filter cloth (22 μm), a composite membrane (10 μm pore size) was successfully used in an anoxic/oxic membrane bioreactor (A/O-MBR) for treating a simulate wastewater in removing nitrate/ammonium for water reuse in a polyester fiber production plant. Its permeate flux and the anti-fouling properties against extracellular polymeric substances (EPS) were studied. Comparing with a commercial (0.1 μm) PVDF (polyvinylidene fluoride) membrane, similar effluent qualities were achieved, meeting the basic COD requirements for reuse. Anti-EPS accumulation, the TiO(2)/PVA Polyester composite membrane had higher sustained permeability and required less frequent cleaning. Its filtration time was 4 times longer when operated at a higher flux than the PVDF membrane. The nano-TiO(2) enhances the interaction between PVA and polyester, forms a more hydrophilic surface, drastically reduces the contact angle with water and reduces EPS fouling. The slow (trans-membrane pressure) TMP rise, loose cake layer, the low filtration resistances, and the EPS, SEM analysis confirmed the advantage of the composite membrane. Potential in lowering the membrane cost, the operation and maintenance cost, and in enhancing MBR waste water treatment efficiency is expected by the use of this new composite membrane. PMID:22325932

  18. Impact of electron-beam irradiation on free-volume related microstructural properties of PVA:NaBr polymer composites

    NASA Astrophysics Data System (ADS)

    Ismayil; Vasachar, Ravindrachary; Bhajantri, Rajashekhar F.; Dhola, Praveena S.; Sanjeev, Ganesh

    2015-01-01

    Sodium Bromide doped Poly(vinyl alcohol) (PVA:NaBr, 80:20) polymer composite films were prepared using a solution casting method. These films were subjected to 8 MeV electron beam radiation at a dose of up to 300 kGy in air at room temperature. The free volume related microstructural and electrical properties of these irradiated films were studied using various characterization methods, such as positron annihilation lifetime spectroscopy (PALS) and AC & DC conductivity measurement techniques. The variations in the positron lifetime data indicate that the free-volume related properties of the doped polymer are affected by irradiation. From the results, it is found that at lower doses, a cross-linking network provides hopping sites for Na+ ions, and at higher doses, the chain-scission process facilitates ionic transport through segmental motion. Thus, the free volume around the polymer chain leads to mobility of the ions as well as the polymer segments and hence contributes to the enhancement of conductivity.

  19. Mucoadhesive polymers: Synthesis and in vitro characterization of thiolated poly(vinyl alcohol).

    PubMed

    Suchaoin, Wongsakorn; Pereira de Sousa, Irene; Netsomboon, Kesinee; Rohrer, Julia; Hoffmann Abad, Patricia; Laffleur, Flavia; Matuszczak, Barbara; Bernkop-Schnürch, Andreas

    2016-04-30

    The aim of this study was to synthesize thiolated poly(vinyl alcohol) (PVA) and to evaluate its mucoadhesive properties. Thiourea and 3-mercaptopropionic acid were utilized in order to obtain thiolated PVAs, namely, TPVA1 and TPVA2, respectively. TPVA1 and TPVA2 displayed 130.44±14.99 and 958.35±155.27μmol immobilized thiol groups per gram polymer, respectively, which were then evaluated regarding reactivity of thiol groups, swelling behavior and mucoadhesive properties. Both thiolated PVAs exhibited the highest reactivity at pH 8.0 whereas more than 95% of free thiol groups were preserved at pH 5.0. Thiolation of PVA decelerated water uptake and prolonged disintegration time of test discs compared to unmodified PVA. Contact time of TPVA1- and TPVA2-based test discs on porcine intestinal mucosa was 3.2- and 15.8-fold prolonged, respectively, in comparison to non-thiolated PVA as measured by rotating cylinder method. According to tensile studies on mucosa, the total work of adhesion (TWA) and the maximum detachment force (MDF) were increased when compared to PVA. Furthermore, thiolated PVAs preserved higher percentage of viable cells compared to unmodified PVA within 24h as evaluated by MTT assay. Accordingly, thiolated PVA represents a novel excipient that can likely improve the mucoadhesive properties of various pharmaceutical formulations. PMID:26965199

  20. Cross-linked poly (vinyl alcohol)/sulfosuccinic acid polymer as an electrolyte/electrode material for H2-O2 proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ebenezer, D.; Deshpande, Abhijit P.; Haridoss, Prathap

    2016-02-01

    Proton exchange membrane fuel cell (PEMFC) performance with a cross-linked poly (vinyl alcohol)/sulfosuccinic acid (PVA/SSA) polymer is compared with Nafion® N-115 polymer. In this study, PVA/SSA (≈5 wt. % SSA) polymer membranes are synthesized by a solution casting technique. These cross-linked PVA/SSA polymers and Nafion are used as electrolytes and ionomers in catalyst layers, to fabricate different membrane electrode assemblies (MEAs) for PEMFCs. Properties of each MEA are evaluated using scanning electron microscopy, contact angle measurements, impedance spectroscopy and hydrogen pumping technique. I-V characteristics of each cell are evaluated in a H2-O2 fuel cell testing fixture under different operating conditions. PVA/SSA ionomer causes only an additional ≈4% loss in the anode performance compared to Nafion ionomer. The maximum power density obtained from PVA/SSA based cells range from 99 to 117.4 mW cm-2 with current density range of 247 to 293.4 mA cm-2. Ionic conductivity of PVA/SSA based cells is more sensitive to state of hydration of MEA, while maximum power density obtained is less sensitive to state of hydration of MEA. Maximum power density of cross-linked PVA/SSA membrane based cell is about 35% that of Nafion® N-115 based cell. From these results, cross-linked PVA/SSA polymer is identified as potential candidate for PEMFCs.

  1. Electrical conduction and dielectric relaxation in p-type PVA/CuI polymer composite

    PubMed Central

    Makled, M.H.; Sheha, E.; Shanap, T.S.; El-Mansy, M.K.

    2012-01-01

    PVA/CuI polymer composite samples have been prepared and subjected to characterizations using FT-IR spectroscopy, DSC analysis, ac spectroscopy and dc conduction. The FT-IR spectral analysis shows remarkable variation of the absorption peak positions whereas DSC illustrates a little decrease of both glass transition temperature, Tg, and crystallization fraction, χ, with increasing CuI concentration. An increase of dc conductivity for PVA/CuI nano composite by increasing CuI concentration is recoded up to 15 wt%, besides it obeys Arhenuis plot with an activation energy in the range 0.54–1.32 eV. The frequency dependence of ac conductivity showed power law with an exponent 0.33 < s < 0.69 which predicts hopping conduction mechanism. The frequency dependence of both dielectric permittivity and dielectric loss obeys Debye dispersion relations in wide range of temperatures and frequency. Significant values of dipole relaxation time obtained which are thermally activated with activation energies in the range 0.33–0.87 eV. A significant value of hopping distance in the range 3.4–1.2 nm is estimated in agreement with the value of Bohr radius of the exciton. PMID:25685462

  2. Comparative study of the electrical and dielectric properties of PVA-PEG-Al 2O 3-MI (M=Na, K, Ag) complex polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Prajapati, G. K.; Gupta, P. N.

    2011-08-01

    Plasticized nanocomposite polymer electrolytes (PNCPEs) based on poly(vinyl alcohol) (PVA)-MI (M=Na, K, Ag) dispersed with nanofillers Al 2O 3 and plasticized with poly(ethylene glycol) (PEG) have been prepared by solution cast technique. The structural properties of the samples have been characterized using various experimental techniques such as XRD, DSC, FTIR and B-G spectroscopy. The ionic conductivity and dielectric constant of the samples have been estimated using a LCZ meter in a wide temperature range, i.e. from 30 to 170 °C. It has been observed that the presence of water molecules in polymer electrolytes significantly affects the mobility of ionic species. The temperature dependent ionic conductivity shows the Arrhenius type behavior separated in three distinct regions. The ionic transference number for all PNCPE samples is found to be ≈1, which strongly suggests their ionic nature.

  3. Study of optical and structural properties of CdSe quantum dot embedded in PVA polymer matrix

    SciTech Connect

    Tyagi, Chetna Sharma, Ambika

    2015-08-28

    To enhance the properties and applicability of devices it is essential to incorporate semiconductor nanoparticles into polymer matrix. This introduces a new branch of science which includes device fabrications such as gas sensors, nonlinear optics, catalysis etc. Herein, we have synthesized CdSe/PVA nanocomposite (NC) material using wet chemical synthesis technique. The XRD studies revealed the formation of crystalline structure of CdSe nanoparticles (NP’s) and PVA NC’s with an average size of 100 nm and 5 nm respectively. Energy band gap is determined using UV-VIS Spectroscopy. A red shift in the absorption edge of CdSe/PVA NC is observed with respect to CdSe Np’s, The photoluminescence spectra also show red shift for CdSe/PVA NC as compared to CdSe NP’s Thus the use of CdSe/PVA for solar cell application would be more preferable than CdSe NP’s.

  4. Investigation on surface molecular conformations and pervaporation performance of the poly(vinyl alcohol) (PVA) membrane.

    PubMed

    Zhang, Wei; Zhang, Zhennan; Wang, Xinping

    2009-05-01

    A simple method of changing pre-treatment temperature in the course of film formation was used to tune the surface structures of PVA membranes. Surface structure and property of the resulting membranes were characterized by X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy, and contact angle measurements. The results show that PVA have different molecular conformations at the membrane surface while those membranes were prepared at different pre-treatment temperature. At higher pre-treatment temperatures, polar acetoxyl residues and hydroxyl groups of the PVA chains oriented in a more orderly fashion, as induced by the faster evaporation of water. When the membranes were in air, CH(3) groups adjacent to the acetoxyl groups covered the surface in order to minimize the surface free energy, while backbones of the PVA were rarely observed. These surfaces exhibited a hydrophilic nature upon contact with water due to rapid surface reconstruction. Conversely, at lower pre-treatment temperatures, the backbone CH(2) groups dominated the surface, forming a less hydrophilic surface. When the PVA membranes were employed to separate ethanol/water mixtures, it was found that the PVA membranes with more hydrophilic surface exhibited higher water selectivity. Our investigation indicates that molecular conformations on the membrane surface have considerable influence on pervaporation performance. PMID:19249794

  5. Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities.

    PubMed

    Zhang, Zhijie; Wu, Yunping; Wang, Zhihua; Zou, Xueyan; Zhao, Yanbao; Sun, Lei

    2016-12-01

    Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. It's also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules. PMID:27612736

  6. A novel biocompatible conducting polyvinyl alcohol (PVA)-polyvinylpyrrolidone (PVP)-hydroxyapatite (HAP) composite scaffolds for probable biological application.

    PubMed

    Chaudhuri, B; Mondal, B; Ray, S K; Sarkar, S C

    2016-07-01

    We have prepared biocompatible composites of 80wt% polyvinyl alcohol (PVA)-(20wt%) polyvinylpyrrolidone (PVP) blend with different concentrations of bioactive nanohydroxyapatite, Ca10(PO4)6(HO)2 (HAP). The composite films demonstrated maximum effective conductivity (σ∼1.64×10(-4)S/m) and effective dielectric constant (ε∼290) at percolation threshold concentration (∼10wt% HAP) at room temperature. These values of σ and ε are much higher than those of PVA, PVP or HAP. Our preliminary observation indicated excellent biocompatibility of the electrospun fibrous meshes of two of these composites with different HAP contents (8.5 and 5wt% within percolation threshold concentration) using NIH 3T3 fibroblast cell line. Cells viability on the well characterized composite fibrous scaffolds was determined by MTT [3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay analysis. Enhancement of σ, due to HAP addition, was found to show increased biocompatibility of the fibrous scaffold. Enhanced σ value of the PVA/PVP-HAP composite provided supporting cues for the increased cell viability and biocompatibility of the composite fibrous meshes. Excellent biocompatibility these electrospun composite scaffolds made them to plausible potential candidates for tissue engineering or other biomedical applications. PMID:26998868

  7. Preparation and characterization of PVP-PVA-ZnO blend polymer nano composite films

    NASA Astrophysics Data System (ADS)

    Divya, S.; Saipriya, G.; Hemalatha, J.

    2016-05-01

    Flexible self-standing films of PVP-PVA blend composites are prepared by using ZnO as a nano filler at different concentrations. The structural, compositional, morphological and optical studies made with the help of X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), Scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-vis) and Photoluminescence (PL) spectra are presented in this paper. The results of XRD indicate that ZnO nanoparticles are formed with hexagonal phase in the polymeric matrix. SEM images show the dispersion of ZnO nano filler in the polymer matrix. UV-vis spectra reveal that the absorption peak is centered around 235nm and 370nm for the nano composite films. The blue shift is observed with decrease in the concentration of the nano filler. PL spectra shows the excitation wavelength is given at 320nm.The emission peaks were observed at 383 nm ascribing to the electronic transitions between valence band and conduction band and the peak at 430 nm.

  8. Effect of Hydroxyl Concentration on Chemical Sensitivity of Polyvinyl Alcohol/Carbon-Black Composite Chemiresistors

    SciTech Connect

    Hughes, Robert C.; Patel, Sanjay V.; Yelton, W. Graham

    1999-05-19

    The sensitivity and selectivity of polyvinyl alcohol (PVA) / carbon black composite films have been found to vary depending upon the hydroxylation percentage ("-OH") of the polymer. These chemiresistors made from PVA films whose polymer backbone is 88% hydroxylated (PVA88) have a high sensitivity to water, while chemiresistors made from PVA75 have a higher sensitivity to methanol. The minor differences in polymer composition result in films with different Hildebrand volubility parameters. The relative responses of several different PVA-based chemiresistors to solvents with different volubility parameters are presented. In addition, polyvinyl acetate (PVAC) films with PVA88 are used in an array to distinguish the responses to methanol-water mixtures.

  9. Dichromated polyvinyl alcohol (DC-PVA) wet processed for high index modulation

    NASA Astrophysics Data System (ADS)

    Rallison, Richard D.

    1997-04-01

    PVA films have been used as mold releases, strippable coatings, binders for photopolymers and when sensitized with metals and/or dyes they have been used as photoresists, volume HOEs, multiplexed holographic optical memory and real time non destructive holographic testing. The list goes on and includes Slime and birth control. In holography, DC-PVA is a real time photoanisotropic recording material useful for phase conjugation experiments and also a stable long term storage medium needing no processing other than heat. Now we add the capability of greatly increasing the versatility of PVA by boosting the index modulation by almost two orders of magnitude. We can add broadband display and HOE applications that were not possible before. Simple two or three step liquid processing is all that is required to make the index modulation grow.

  10. Design strategies for 157-nm single-layer photoresists: lithographic evaluation of a poly(α -trifluoromethyl vinyl alcohol) copolymer

    NASA Astrophysics Data System (ADS)

    Schmaljohann, Dirk; Bae, Young C.; Weibel, Gina L.; Hamad, Alyssandrea H.; Ober, Christopher K.

    2000-06-01

    Poly(vinyl alcohol-co-(alpha) -trifluoromethyl vinyl alcohol) (PVA-co-CF3PVA) protected with an acid cleavable group was prepared as a single-layer photoresist for use in 157 nm VUV lithography. It was found that the (alpha) -trifluoromethyl substituent renders PVA-co-CF3PVA readily soluble in 0.262 N TMAH. The protected polymer can be spin-coated from PGMEA and preliminary studies using 248 nm exposure showed a THP protected PVA-co-CF3PVA undergoes chemically amplified deprotection with a clearing dose of approximately 15 mJ/cm2. Using a VUV spectrometer, absorption coefficients of approximately 3 micrometer-1 were observed at 157 nm with PVA-co-CF3PVA and THP protected PVA-co-CF3PVA. Detailed lithographic evaluation of the polymer is underway and design strategies for 157 nm single-layer photoresists will be discussed.

  11. The effect of poly vinyl alcohol (PVA) surfactant on phase formation and magnetic properties of hydrothermally synthesized CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Jalalian, M.; Mirkazemi, S. M.; Alamolhoda, S.

    2016-12-01

    Nanoparticles of CoFe2O4 were synthesized by hydrothermal process at 190 °C with and without poly vinyl alcohol (PVA) addition using treatment durations of 1.5-6 h. The synthesized powders were characterized with X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), Field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. XRD results show presence of CoFe2O4 as the main phase and Co3O4 as the lateral phase in some samples. The results show that in the samples synthesized without PVA addition considerable amount of lateral phase is present after 3 h of hydrothermal treatment while with PVA addition this phase is undetectable in the XRD patterns of the sample synthesized at the same conditions. Microstructural studies represent increasing of particle size with increasing of hydrothermal duration and formation of coarser particles with PVA addition. The highest maximum magnetization (Mmax) values in both of the samples that were synthesized with and without PVA addition are about 59 emu/g that were obtained after 4.5 h of hydrothermal treatment. Intrinsic coercive field (iHc) value of the sample without PVA addition increases from 210 to 430 Oe. While with PVA addition the iHc value changes from 83 Oe to 493 Oe. The mechanism of changes in Mmax and iHc values has been explained.

  12. Radiation-crosslinking of shape memory polymers based on poly(vinyl alcohol) in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Basfar, A. A.; Lotfy, S.

    2015-01-01

    Shape memory polymers based on poly(vinyl alcohol) (SM-PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA) and multi-wall carbon nanotubes (MWCNTs) crosslinked by ionizing radiation were investigated. Chemical-crosslinking of PVA by glutaraldehyde in the presence of CEA and MWCNTs was also studied. The swelling and gel fraction of the radiation-crosslinked SM-PVA and chemically crosslinked systems were evaluated. Analysis of the swelling and gel fraction revealed a significant reduction in swelling and an increase in the gel fraction of the material that was chemically crosslinked with glutaraldehyde. The radiation-crosslinked SM-PVA demonstrated 100% gelation at an irradiation dose of 50 kGy. In addition, radiation-crosslinked SM-PVA exhibited good temperature responsive shape-memory behavior. A scanning electron microscopy (SEM) analysis was performed. The thermal properties of radiation-crosslinked SM-PVA were investigated by a thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The ability of the material to return or store energy (E‧), to its ability to lose energy (E″), and the ratio of these effects (Tanδ), which is called damping were examined via DMA. The temperature of Tanδ in the radiation-crosslinked SM-PVA decreased significantly by 6 and 13 °C as a result of the addition of MWCNTs. In addition, the temperature of Tanδ for SM-PVA increased as the irradiation dose increased. These radiation-crosslinked SM-PVA materials show promising shape-memory behavior based on the range of temperatures at which Tanδ appears.

  13. Investigation of electrochemical properties of a poly(vinyl alcohol)/poly(acrylic acid) polymer blend

    SciTech Connect

    DeSantis, C.O.; Seliskar, C.; Heineman, W.R.

    1995-12-31

    Chemical sensors have wide applications in medicine, environmental monitoring, industrial applications, and others because of their versatility, ruggedness, sensitivity, selectivity, and economy. Electrochemical sensors are constructed by using a conducting medium, in this case graphite, and applying a constant potential while measuring changes in the current. Polymers are used for electrochemical sensors to exclude interferents from the electrode surface, to preconcentrate the analyte near the electrode, and in some cases to provide a matrix for the immobilization of analytes, such as enzymes. These functions of the polymer can serve to improve the detection limit of the sensor. This project involves the evaluation of a new polymer for electrode modification. The poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) polymer was originally developed as an ion exchanger for use in space batteries. It has also been used in wastewater cleanup because it will concentrate heavy metals in the presence of calcium ion. This polymer is also optically clear, so it can potentially be used for an optical sensor. We are interested in investigating the ion exchange properties of the PVA/PAA polymer, as well as the ability of this polymer to preconcentrate and exclude analytes on the basis of size, charge, and hydrophilic/hydrophobic interactions.

  14. Electrospinning, mechanical properties, and cell behavior study of chitosan/PVA nanofibers.

    PubMed

    Koosha, Mojtaba; Mirzadeh, Hamid

    2015-09-01

    Electrospinning process has been widely used to produce nanofibers from polymer blends. Poly(vinyl alcohol) (PVA) and chitosan (CS) have numerous biomedical applications such as wound healing and tissue engineering. Nanofibers of CS/PVA have been prepared by many works, however, a complete physicochemical and mechanical characterization as well as cell behavior has not been reported. In this study, PVA and CS/PVA blend solutions in acetic acid 70% with different volume ratios (30/70, 50/50, and 70/30) were electrospun in constant electrospinning process parameters. The structure and morphology of nanofibrous mats were characterized by SEM, FTIR, and XRD methods. The best nanofibrous mat was achieved from the CS/PVA 30/70 blend solution regarding the electrospinning throughput. The dynamic mechanical thermal analysis (DMTA) of PVA and CS/PVA 30/70 nanofibrous mats were measured which were not considered in the previous studies. DMTA results in accordance to the DSC analysis approved the partial compatibility between the two polymers, while a single glass transition temperature was not observed for the blend. The tensile strength of PVA and CS/PVA nanofibers were also reported. Results of cell behavior study indicated that the heat stabilized nanofibrous mat CS/PVA 30/70 was able to support the attachment and proliferation of the fibroblast cells. PMID:25727934

  15. Study of Dielectric Behavior and Charge Conduction Mechanism of Poly(Vinyl Alcohol) (PVA)-Copper (Cu) and Gold (Au) Nanocomposites as a Bio-resorbable Material for Organic Electronics

    NASA Astrophysics Data System (ADS)

    Mahendia, Suman; Goyal, Parveen Kumar; Tomar, Anil Kumar; Chahal, Rishi Pal; Kumar, Shyam

    2016-06-01

    Poly(vinyl alcohol) (PVA) embedded with varying concentrations of chemically synthesized copper (Cu) and gold (Au) nanoparticles (NPs) were prepared using ex situ sol-gel casting method. The addition of almost the same concentration of CuNPs in PVA improves the conducting properties, while that of AuNPs improves the dielectric nature of composite films. It has been found that addition of AuNPs up to ˜0.4 wt.% concentration enhaneces the capacitive nature due to the formation of small Coulomb tunneling knots as internal capacitors. The dielectric studies suggest the Maxwell-Wagner interfacial polarization as the dominant dielectric relaxation process, whereas the I-V characteristics indicate bulk limited Poole-Frenkel emission at high voltages as the dominant charge transport mechanism operating at room temperature in all specimens. These novel features lead to the conclusion that addition of a small quantity of metal nanoparticles can help tune the properties of PVA for desired applications in bio-compatible polymer-based organic electronic devices.

  16. FTIR studies of plasticized poly(vinyl alcohol)-chitosan blend doped with NH 4NO 3 polymer electrolyte membrane

    NASA Astrophysics Data System (ADS)

    Kadir, M. F. Z.; Aspanut, Z.; Majid, S. R.; Arof, A. K.

    2011-03-01

    Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH 4NO 3) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer-solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm -1 and the amine band at 1591 cm -1 to 1650 and 1557 cm -1 respectively and the shift of the hydroxyl band from 3377 to 3354 cm -1. The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm -1 and is observed at 3343 cm -1 in the spectrum of the PVA film. On addition of NH 4NO 3 up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm -1 to 1642, 1541 and 3348 cm -1 indicating that the chitosan has complexed with the salt. In the PVA-NH 4NO 3 spectrum, the hydroxyl band has shifted from 3343 to 3272 cm -1 on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA-chitosan-EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA-chitosan-NH 4NO 3 systems. In the spectrum of PVA-chitosan-NH 4NO 3-EC complex, the doublet C dbnd O stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.

  17. Photogeneration of H2O2 in SPEEK/PVA aqueous polymer solutions.

    PubMed

    Little, Brian K; Lockhart, PaviElle; Slaten, B L; Mills, G

    2013-05-23

    Photolysis of air-saturated aqueous solutions containing sulphonated poly(ether etherketone) and poly(vinyl alcohol) results in the generation of hydrogen peroxide. Consumption of oxygen and H2O2 formation are initially concurrent processes with a quantum yield of peroxide generation of 0.02 in stirred or unstirred solutions within the range of 7 ≤ pH ≤ 9. The results are rationalized in terms of O2 reduction by photogenerated α-hydroxy radicals of the polymeric ketone in competition with radical-radical processes that consume the macromolecular reducing agents. Generation of H2O2 is controlled by the photochemical transformation that produces the polymer radicals, which is most efficient in neutral and slightly alkaline solutions. Quenching of the excited state of the polyketone by both H3O(+) and OH(-) affect the yields of the reducing macromolecular radicals and of H2O2. Deprotonation of the α-hydroxy polymeric radicals at pH > 9 accelerate their decay and contribute to suppressing the peroxide yields in basic solutions. Maxima in [H2O2] are observed when illuminations are performed with static systems, where O2 reduction is faster than diffusion of oxygen into the solutions. Under such conditions H2O2 can compete with O2 for the reducing radicals resulting in a consumption of the peroxide. PMID:23654204

  18. Micro structural studies of PVA doped with metal oxide nanocomposites films

    SciTech Connect

    Kumar, N. B. Rithin; Crasta, Vincent Viju, F.; Praveen, B. M.; Shreeprakash, B.

    2014-04-24

    Nanostructured PVA polymer composites are of rapidly growing interest because of their sized-coupled properties. The present article deals with both ZnO and WO{sub 3} embedded in a polyvinyl alcohol (PVA) matrix using a solvent casting method. These films were characterized using FTIR, XRD, and SEM techniques. The FTIR spectra of the doped PVA shows shift in the bands, which can be understood on the basis of intra/inter molecular hydrogen bonding with the adjacent OH group of PVA. The phase homogeneity and morphology of the polymer composites have been analyzed using scanning electron microscope (SEM). The crystal structure and crystallinity of polymer nanocomposites were studied by X-ray diffraction technique (XRD). Thus due to the interaction of dopant and complex formation, the structural repositioning takes place and crystallinity of the nanocomposites decreases.

  19. Development, mechanical evaluation and surface characteristics of chitosan/polyvinyl alcohol based polymer composite coatings on titanium metal.

    PubMed

    Mishra, Sandeep K; Kannan, S

    2014-12-01

    Mechanical properties of orthopedic implants play important role in the regeneration and cell growth of the diseased body part. The present investigation was aimed at the development of a biocompatible, biodegradable and mechanically stable coating of chitosan (CS)-polyvinyl alcohol (PVA) polymer composite on Titanium (Ti) metal by employing a simple methodology at ambient conditions. The PVA to CS concentrations were maintained in fixed ratios of 1:4 weight/weight (w/w) for the development of all the coatings on Ti metal. Four different concentrations of the polymers ranging in the order of 5%, 10%, 15% and 20% weight/volume (w/v) solution of CS were selected in an aim to test their efficacy on mechanical stability. The results obtained from the analysis confirmed considerable improvement in mechanical properties of the composite polymer film comprising CS and PVA on Ti metal with the four different concentrations showing variable elastic modulus and hardness. The difference in mechanical properties of both dehydrated and hydrated coatings demonstrates the effective and efficient shielding of high mechanical properties of Ti metal in physiological conditions. The scratch tests performed on the coated specimens also indicated a good adhesion of the polymer on the Ti metal surface. PMID:25265031

  20. Comparative bio-safety and in vivo evaluation of native or modified locust bean gum-PVA IPN microspheres.

    PubMed

    Kaity, Santanu; Ghosh, Animesh

    2015-01-01

    Strategically developed natural polymer-based controlled release multiparticulate drug delivery systems have gained special interest for “spatial placement” and “temporal delivery” of drug molecules. In our earlier study, locust bean gum-poly(vinyl alcohol) interpenetrating polymer network (LBG-PVA IPN), carboxymethylated locust bean gum-poly(vinyl alcohol) interpenetrating polymer network (CMLBG-PVA IPN) and acrylamide grafted locust bean gum-poly(vinyl alcohol) interpenetrating polymer network (Am-g-LBG-PVA IPN) were prepared and characterized. The present study deals with accelerating stability testing, comparative bio-safety and single dose in vivo pharmacokinetic study of all three IPN microspheres for controlled oral delivery of buflomedil hydrochloride (BH). From the stability study, it was observed that the particles were stable throughout the study period. From toxicity and biodegradability study it was proved that the microspheres were safe for internal use and complied with bio-safety criterion. From the in vivo pharmacokinetic study in rabbits, it was observed that the CMLBG-PVA IPN microspheres possessed almost similar Tmax value with BH oral suspension. However, in comparison between the LBG-PVA and Am-g-LBG-PVA IPN microspheres, the later showed well controlled release property than the first in biological condition. Thus, this type of delivery system might be useful to achieve the lofty goals of the controlled release drug delivery. PMID:25307127

  1. A tribo-mechanical analysis of PVA-based building-blocks for implementation in a 2-layered skin model.

    PubMed

    Morales Hurtado, M; de Vries, E G; Zeng, X; van der Heide, E

    2016-09-01

    Poly(vinyl) alcohol hydrogel (PVA) is a well-known polymer widely used in the medical field due to its biocompatibility properties and easy manufacturing. In this work, the tribo-mechanical properties of PVA-based blocks are studied to evaluate their suitability as a part of a structure simulating the length scale dependence of human skin. Thus, blocks of pure PVA and PVA mixed with Cellulose (PVA-Cel) were synthesised via freezing/thawing cycles and their mechanical properties were determined by Dynamic Mechanical Analysis (DMA) and creep tests. The dynamic tests addressed to elastic moduli between 38 and 50kPa for the PVA and PVA-Cel, respectively. The fitting of the creep compliance tests in the SLS model confirmed the viscoelastic behaviour of the samples with retardation times of 23 and 16 seconds for the PVA and PVA-Cel, respectively. Micro indentation tests were also achieved and the results indicated elastic moduli in the same range of the dynamic tests. Specifically, values between 45-55 and 56-81kPa were obtained for the PVA and PVA-Cel samples, respectively. The tribological results indicated values of 0.55 at low forces for the PVA decreasing to 0.13 at higher forces. The PVA-Cel blocks showed lower friction even at low forces with values between 0.2 and 0.07. The implementation of these building blocks in the design of a 2-layered skin model (2LSM) is also presented in this work. The 2LSM was stamped with four different textures and their surface properties were evaluated. The hydration of the 2LSM was also evaluated with a corneometer and the results indicated a gradient of hydration comparable to the human skin. PMID:27236420

  2. Determining the electrical mechanism of the surface resistivity property of doped polyvinyl alcohol (PVA) and the pyroelectric property of polyvinylidene difluoride (PVDF) thin films

    NASA Astrophysics Data System (ADS)

    Edwards, Matthew; Janen, Afef; Guggilla, Padmaja; Polius, Jemelia; Douglas, Jade; Curley, Michael

    2015-08-01

    Previously, we have reported measurements of the temperature-dependent surface resistivity of pure and multi-walled carbon nanotubes doped Polyvinyl Alcohol (PVA) thin films. In the temperature range from 22 °C to 40 °C, with a humidity-controlled environment, we found the surface resistivity to decrease initially but to rise steadily as the temperature continued to increase. Correspondingly, we have measured the temperature-dependent pyroelectric coefficient of doped polyvinylidene difluoride (PVDF) thin films, very well. While the physical mechanism of the pyroelectric phenomenon in PVDF thin films is quite well known, the surface resistivity behavior of PVA thin films is not so well known. Here, we address this concern by reporting the electrical mechanistic phenomena that contribute to surface resistivity of pure and doped PVA thin films, and give preliminary surface resistivity detectivity and other relevant quality factors for infrared (IR) and motion sensors. Regarding the pyroelectric effect of doped PVDF thin films, we give materials Figures-of-Merit based on our measurements. In addition, pyroelectric and surface resistivity infrared fundamentals, IR sensor uniqueness, and innovative techniques are presented.

  3. 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.

  4. One-step synthesis of size-tunable Ag nanoparticles incorporated in electrospun PVA/cyclodextrin nanofibers.

    PubMed

    Celebioglu, Asli; Aytac, Zeynep; Umu, Ozgun C O; Dana, Aykutlu; Tekinay, Turgay; Uyar, Tamer

    2014-01-01

    One-step synthesis of size-tunable silver nanoparticles (Ag-NP) incorporated into electrospun nanofibers was achieved. Initially, in situ reduction of silver salt (AgNO3) to Ag-NP was carried out in aqueous solution of polyvinyl alcohol (PVA). Here, PVA was used as reducing agent and stabilizing polymer as well as electrospinning polymeric matrix for the fabrication of PVA/Ag-NP nanofibers. Afterwards, hydroxypropyl-beta-cyclodextrin (HPβCD) was used as an additional reducing and stabilizing agent in order to control size and uniform dispersion of Ag-NP. The size of Ag-NP was ∼8 nm and some Ag-NP aggregates were observed for PVA/Ag-NP nanofibers, conversely, the size of Ag-NP decreased from ∼8 nm down to ∼2 nm within the fiber matrix without aggregation were attained for PVA/HPβCD nanofibers. The PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibers exhibited surface enhanced Raman scattering (SERS) effect. Moreover, antibacterial properties of PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibrous mats were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. PMID:24274573

  5. Anomalous dielectric behaviour of poly(vinyl alcohol)-silicon dioxide (PVA-SiO2) nanocomposites

    NASA Astrophysics Data System (ADS)

    Choudhary, Shobhna; Sengwa, R. J.

    2016-05-01

    Complex dielectric function, electric modulus, ac conductivity and impedance spectra of PVA-SiO2 nanocomposite films have been investigated in the frequency range of 20 Hz to 1 MHz and temperature range from 30 °C to 60 °C. Real part of dielectric function of the nanocomposites slowly decreases with increase of frequency and it shows a non-linear increase with the increase of temperature. An anomalous variation is observed in dielectric and electrical functions with increase of SiO2 concentrations in the PVA matrix. The ac conductivity of these materials increases whereas impedance values decrease linearly by five orders of magnitude with increase of frequency from 20 Hz to 1 MHz. Dielectric loss values of these films are found minimum at intermediate frequency region, and it increases at low and high frequency regions confirming the presence of multiple relaxation processes. The contributions of interfacial polarization effect and dipolar ordering in dielectric properties of these materials have been explored, and their technological applications as nanodielectrics have been discussed. The XRD patterns reveal that the interactions between PVA and SiO2 disturb the dipolar ordering resulting decrease of crystallinity of the PVA in the nanocomposites.

  6. A polymer of caffeyl alcohol in plant seeds

    PubMed Central

    Chen, Fang; Tobimatsu, Yuki; Havkin-Frenkel, Daphna; Dixon, Richard A.; Ralph, John

    2012-01-01

    Lignins are complex phenylpropanoid polymers mostly associated with plant secondary cell walls. Lignins arise primarily via oxidative polymerization of the three monolignols, p-coumaryl, coniferyl, and sinapyl alcohols. Of the two hydroxycinnamyl alcohols that represent incompletely methylated biosynthetic products (and are not usually considered to be monolignols), 5-hydroxyconiferyl alcohol is now well established as incorporating into angiosperm lignins, but incorporation of caffeyl alcohol has not been shown. We report here the presence of a homopolymer of caffeyl alcohol in the seed coats of both monocot and dicot plants. This polymer (C-lignin) is deposited to high concentrations in the seed coat during the early stages of seed development in the vanilla orchid (Vanilla planifolia), and in several members of the Cactaceae. The lignin in other parts of the Vanilla plant is conventionally biosynthesized from coniferyl and sinapyl alcohols. Some species of cacti contain only C-lignin in their seeds, whereas others contain only classical guaiacyl/syringyl lignin (derived from coniferyl and sinapyl alcohols). NMR spectroscopic analysis revealed that the Vanilla seed-coat polymer was massively comprised of benzodioxane units and was structurally similar to the polymer synthesized in vitro by peroxidase-catalyzed polymerization of caffeyl alcohol. CD spectroscopy did not detect any optical activity in the seed polymer. These data support the contention that the C-lignin polymer is produced in vivo via combinatorial oxidative radical coupling that is under simple chemical control, a mechanism analogous to that theorized for classical lignin biosynthesis. PMID:22307645

  7. 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

  8. The effects of addition of poly(vinyl) alcohol (PVA) as a green corrosion inhibitor to the phosphate conversion coating on the anticorrosion and adhesion properties of the epoxy coating on the steel substrate

    NASA Astrophysics Data System (ADS)

    Ramezanzadeh, B.; Vakili, H.; Amini, R.

    2015-02-01

    Steel substrates were chemically treated by room temperature zinc phosphate conversion coating. Poly(vinyl) alcohol (PVA) was added to the phosphate solution as a green corrosion inhibitor. Finally, the epoxy/polyamide coating was applied on the untreated and surface treated steel samples. The effects of PVA on the morphological properties of the phosphate coating were studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measuring device. The adhesion properties of the epoxy coatings applied on the surface treated samples were investigated by pull-off and cathodic delamination tests. Also, the anticorrosion properties of the epoxy coatings were studied by electrochemical impedance spectroscopy (EIS). Results showed that addition of PVA to the phosphate coating increased the population density of the phosphate crystals and decreased the phosphate grain size. The contact angle of the steel surface treated by Zn-PVA was lower than Zn treated one. The corrosion resistance of the epoxy coating was considerably increased on the steel substrate treated by zinc phosphate conversion coating containing PVA. PVA also enhanced the adhesion properties of the epoxy coating to the steel surface and decreased the cathodic delamination significantly.

  9. The study of crystallization and interfacial morphology in polymer/carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Minus, Marilyn Lillith

    This study illustrates the ability of SWNT to nucleate and template polymer crystallization and orientation, and produce materials with improved properties and unique polymer morphologies. This research work focuses primarily on the physical interaction between single-wall carbon nanotubes (SWNT) and the flexible polymer system polyvinyl alcohol (PVA). Polymer crystallization in the near vicinity of SWNT (interphase) has been studied to understand the capability of SWNT in influence polymer morphology in bulk films and fibers. Fibrillar crystallization was achieved by shearing PVA/SWNT dispersions and resulted in the formation of oriented PVA/SWNT fibers or ribbons, while PVA solutions produce unoriented fibers. PVA single crystals were grown in PVA solutions as well as PVA/SWNT dispersions over a period of several months at room temperature (25°C). PVA single crystal growth in PVA/SWNT dispersions is templated by SWNT, and these crystals show the presence of new morphologies for PVA. PVA single crystals of differing morphology were also grown at elevated temperatures, and show morphology dependant electron beam irradiation resistance. Gel-spinning was used to produce PVA, and PVA/SWNT fibers where, PVA crystallization in the bulk fiber was observed. With 1 wt% SWNT loading in PVA, the fiber tensile strength increased from 1.6 GPa for the control PVA to 2.6 GPa for PVA/SWNT. Analysis of this data suggests stress of up to ˜120 GPa on the SWNT. This is the highest reported stress on the SWNT to date and confirm excellent reinforcement and load transfer of SWNT in the PVA matrix. Raman spectroscopy data show high SWNT alignment in the fiber where the I0*/I90* ratio is measured to be 106. High-resolution transmission electron microscopy (HR-TEM) is used to characterize polymer morphology near the polymer-SWNT interface for PVA/SWNT fibers. HR-TEM studies of Polymer/CNT composites show distinct morphological differences at the polymer-SWNT interface/interphase for

  10. Study of structural modification of PVA by incorporating Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Saini, Isha; Sharma, Annu; Rozra, Jyoti; Aggarwal, Sanjeev; Dhiman, Rajnish; Sharma, Pawan K.

    2016-05-01

    Nanocomposites of PVA with Ag nanoparticles dispersed in it were synthesized using solution casting method. The morphology and size distribution of Ag nanoparticles embedded in PVA matrix were obtained by transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE-SEM). Raman spectroscopy was used to examine structural changes taking place inside polyvinyl alcohol (PVA) matrix due to incorporation of Ag nanoparticle. Raman analysis indicates that Ag nanoparticles interact with PVA through H-bonding.

  11. Micropatterning of silver nanoclusters embedded in polyvinyl alcohol films.

    PubMed

    Karimi, Nazanin; Kunwar, Puskal; Hassinen, Jukka; Ras, Robin H A; Toivonen, Juha

    2016-08-01

    Direct laser writing has been utilized to fabricate highly photostable fluorescent nanocluster microstructures in an organic polymer poly(methacrylic acid), where the carboxyl functional group is reported to play a vital role in nanocluster stabilization. In this Letter, we demonstrate that not only the polymer containing the carboxyl functional group, but also the polymer comprising the hydroxyl group, namely polyvinyl alcohol (PVA), can act as an appropriate stabilizer matrix for laser-induced synthesis and patterning of silver nanoclusters. The as-formed nanoclusters in the PVA film exhibit broadband emission and photostability comparable to the nanoclusters formed in the poly(methacrylic acid) polymer. As PVA is a widely used, nontoxic, biocompatible and biodegradable polymer, the technique of patterning fluorescent nanoclusters in PVA thin films is expected to find numerous applications in fields like fluorescence imaging, biolabeling, and sensing. PMID:27472635

  12. pH-sensitive interpenetrating polymer network microspheres of poly(vinyl alcohol) and carboxymethyl cellulose for controlled release of the nonsteroidal anti-inflammatory drug ketorolac tromethamine.

    PubMed

    Kondolot Solak, Ebru; Er, Akın

    2016-05-01

    In this study, we aimed to produce pH-sensitive microspheres for the controlled release of the nonsteroidal anti-inflammatory drug, ketorolac tromethamine (KT). For this purpose, an interpenetrating polymer network (IPN) of microspheres of poly(vinyl alcohol) (PVA)/sodium carboxymethyl cellulose (NaCMC) were prepared, based on different formulations using glutaraldehyde (GA) (0.66 M) and hydrochloric acid (HCl) (3%, v/v). The preparation conditions of the microspheres were optimized by considering the percentage of entrapment efficiency and swelling capacity of the microspheres, and their release data. The effects of PVA and NaCMC ratio on the release of KT for over a period of 6 h, at three pH values (1.2, 6.8, and 7.4), have been discussed. PMID:25619756

  13. Lithium ion conducting PVA:PVdF polymer electrolytes doped with nano SiO2 and TiO2 filler

    NASA Astrophysics Data System (ADS)

    Hema, M.; Tamilselvi, P.

    2016-09-01

    The effect of nano SiO2 and TiO2 fillers on the thermal, mechanical and electrochemical properties of PVA:PVdF:LiCF3SO3 have been investigated by three optimized systems of SPE (80PVA:20PVdF:15LiCF3SO3), CPE-I (SPE:8SiO2) and CPE-II (SPE:4TiO2). From the TGA curve least weight loss has been observed for CPE-II indicating high thermal stability compared to other systems. Stress-strain curve of the prepared samples confirm the enhancement of tensile strength in CPE-II compared to CPE-I and SPE. Conductivity studies show that addition of TiO2 filler slightly enhances ionic conductivity 3.7×10-3 S cm-1 compared to filler free system at 303 K. Dielectric plots have been analyzed and CPE-II possesses higher dielectric constant compared to CPE-I and filler free system. Temperature dependence of modulus plots has been studied for highest conductivity possessing sample. Wider electrochemical stability has been obtained for nano-composite polymer electrolytes. The results conclude that the prepared CPE-II shows the best performance and it will be well suited for lithium ion batteries.

  14. Development of polymer optical waveguide-type alcohol sensor

    NASA Astrophysics Data System (ADS)

    Nagata, Junichi; Honma, Satoshi; Morisawa, Masayuki; Muto, Shinzo

    2008-03-01

    Recently, alcohols such as methanol and ethanol have a wide attention as important fuel in next generation. However, As is known, many alcohols have a toxic and explosive nature. To prevent accidents caused by alcohol, development of a safety and highly sensitive sensor is required strongly. In addition, it is desired to be simple and low-cost. So, in this paper, polymer waveguide-type optical alcohol sensors such as fiber-type and channel waveguide-type have been studied. In these sensor head, refractive index n II of cladding layer was set at slightly larger value than that of core (n I). Therefore, in the state without alcohol, the sensor head operate as a leaky waveguide. On the other hand in the state with alcohol, cladding polymer causes swelling and its refractive index becomes lower than n I in core. Based on this principle, large change in output light intensity occurs and detection of alcohol concentration becomes possible even for vapor phase alcohol. In the experiment using a fiber-type sensor with a core size of 0.25 mm, detection of 1% methanol vapor could easily be obtained. Furthermore, using a channel waveguide-type sensor head with a core size of about 50μm×40μm, large increase in sensitivity was observed.

  15. Alcohol vapor sensory properties of nanostructured conjugated polymers

    NASA Astrophysics Data System (ADS)

    Bearzotti, Andrea; Macagnano, Antonella; Pantalei, Simone; Zampetti, Emiliano; Venditti, Iole; Fratoddi, Ilaria; Vittoria Russo, Maria

    2008-11-01

    The response to relative humidity (RH) and alcohol vapors of resistive-type sensors based on nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymer poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), were investigated. Sensors based on ordered arrays of these nanostructured polymeric materials showed stable and reproducible current intensity variations in the range 10-90% of relative humidity at room temperature. Both polymers also showed sensitivity to aliphatic chain primary alcohols, and a fine tuning of the sensor response was obtained by varying the chain length of the alcohol in relation to the polarity. The nanostructured feature of polymeric-based membranes seems to have an effect on the sensing response and an enhancement of the sensitivity was observed for the response to water and alcohol vapor variations with respect to previous studies based on amorphous polyphenylacetylene. High stability of the polymeric nanostructured membranes was detected with no aging after two weeks in continuum stressing measurement conditions.

  16. Amniotic membrane immobilized poly(vinyl alcohol) hybrid polymer as an artificial cornea scaffold that supports a stratified and differentiated corneal epithelium.

    PubMed

    Uchino, Yuichi; Shimmura, Shigeto; Miyashita, Hideyuki; Taguchi, Tetsushi; Kobayashi, Hisatoshi; Shimazaki, Jun; Tanaka, Junzo; Tsubota, Kazuo

    2007-04-01

    Poly(vinyl alcohol) (PVA) is a biocompatible, transparent hydrogel with physical strength that makes it promising as a material for an artificial cornea. In our previous study, type I collagen was immobilized onto PVA (PVA-COL) as a possible artificial cornea scaffold that can sustain a functional corneal epithelium. The cellular adhesiveness of PVA in vitro was improved by collagen immobilization; however, stable epithelialization was not achieved in vivo. To improve epithelialization in vivo, we created an amniotic membrane (AM)-immobilized polyvinyl alcohol hydrogel (PVA-AM) for use as an artificial cornea material. AM was attached to PVA-COL using a tissue adhesive consisting of collagen and citric acid derivative (CAD) as a crosslinker. Rabbit corneal epithelial cells were air-lift cultured with 3T3 feeder fibroblasts to form a stratified epithelial layer on PVA-AM. The rabbit corneal epithelial cells formed 3-5 layers of keratin-3-positive epithelium on PVA-AM. Occludin-positive cells were observed lining the superficial epithelium, the gap-junctional protein connexin43-positive cells was localized to the cell membrane of the basal epithelium, while both collagen IV were observed in the basement membrane. Epithelialization over implanted PVA-AM was complete within 2 weeks, with little inflammation or opacification of the hydrogel. Corneal epithelialization on PVA-AM in rabbit corneas improved over PVA-COL, suggesting the possibility of using PVA-AM as a biocompatible hybrid material for keratoprosthesis. PMID:16924609

  17. Hysteresis mechanism and control in pentacene organic field-effect transistors with polymer dielectric

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Shi, Wei; Han, Shijiao; Yu, Junsheng

    2013-05-01

    Hysteresis mechanism of pentacene organic field-effect transistors (OFETs) with polyvinyl alcohol (PVA) and/or polymethyl methacrylate (PMMA) dielectrics is studied. Through analyzing the electrical characteristics of OFETs with various PVA/PMMA arrangements, it shows that charge, which is trapped in PVA bulk and at the interface of pentacene/PVA, is one of the origins of hysteresis. The results also show that memory window is proportional to both trap amount in PVA and charge density at the gate/PVA or PVA/pentacene interfaces. Hence, the controllable memory window of around 0 ˜ 10 V can be realized by controlling the thickness and combination of triple-layer polymer dielectrics.

  18. Memristive learning and memory functions in polyvinyl alcohol polymer memristors

    NASA Astrophysics Data System (ADS)

    Lei, Yan; Liu, Yi; Xia, Yidong; Gao, Xu; Xu, Bo; Wang, Suidong; Yin, Jiang; Liu, Zhiguo

    2014-07-01

    Polymer based memristive devices can offer simplicity in fabrication and at the same time promise functionalities for artificial neural applications. In this work, inherent learning and memory functions have been achieved in polymer memristive devices employing Polyvinyl Alcohol. The change in conduction in such polymer devices strongly depends on the pulse amplitude, duration and time interval. Through repetitive stimuli training, temporary short-term memory can transfer into consolidated long-term memory. These behaviors bear remarkable similarities to certain learning and memory functions of biological systems.

  19. Cationic-modified PVA as a dry strength additive for rice straw fibers.

    PubMed

    Fatehi, P; Tutus, A; Xiao, H

    2009-01-01

    Extensive research has shown that non-wood fibers are able to be substituted for wood fibers. The major shortcoming of non-fibers is their high silica content that causes some operational problems in mills, and hence silica should be kept in pulps. By keeping silica in pulps, however, the mechanical properties of papers are reduced, and a dry strength additive may be required. In this study, cationic polyvinyl alcohols (C-PVA) with two different molecular weights were prepared, and employed as dry strength additives. The adsorption of polymers on rice straw fibers obtained via soda-air-anthraquinone (AQ) pulping under various conditions was investigated thoroughly. Convincing results demonstrated that high molecular weight polymers performed more efficiently on dry strength enhancements of papers, while they adsorbed less than lower molecular weight polymers on fibers. However, the stiffness of fibers was increased to a larger extent by applying a higher molecular weight C-PVA. PMID:18774707

  20. Enhanced mechanical, thermal and antimicrobial properties of poly(vinyl alcohol)/graphene oxide/starch/silver nanocomposites films.

    PubMed

    Usman, Adil; Hussain, Zakir; Riaz, Asim; Khan, Ahmad Nawaz

    2016-11-20

    In the present work, synthesis of poly(vinyl alcohol)/graphene oxide/starch/silver (PVA/GO/Starch/Ag) nanocomposites films is reported. Such films have been characterized and investigated for their mechanical, thermal and antimicrobial properties. The exfoliation of GO in the PVA matrix occurs owing to the non-covalent interactions of the polymer chains of PVA and hydrophilic surface of the GO layers. Presence of GO in PVA and PVA/starch blends were found to enhance the tensile strength of the nanocomposites system. It was found that the thermal stability of PVA as well as PVA/starch blend systems increased by the incorporation of GO where strong physical bonding between GO layers and PVA/starch blends is assumed to cause thermal barrier effects. Antimicrobial properties of the prepared films were investigated against Escherichia coli and Staphylococcus aureus. Our results show enhanced antimicrobial properties of the prepared films where PVA-GO, PVA-Ag, PVA-GO-Ag and PVA-GO-Ag-Starch showed antimicrobial activity in ascending order. PMID:27561532

  1. pH- and sugar-sensitive multilayer films composed of phenylboronic acid (PBA)-modified poly(allylamine hydrochloride) (PBA-PAH) and poly(vinyl alcohol) (PVA): A significant effect of PBA content on the film stability.

    PubMed

    Seno, Masaru; Yoshida, Kentaro; Sato, Katsuhiko; Anzai, Jun-Ichi

    2016-05-01

    Multilayer thin films composed of phenylboronic acid (PBA)-modified poly(allylamine hydrochloride) (PAH), PBA-PAH, with different PBA contents were prepared to study the effect of PBA content on the stability of the films. An alternate deposition of PBA-PAH and poly(vinyl alcohol) (PVA) on the surface of a quartz slide afforded multilayer films through forming boronate ester bonds between PBA-PAH and PVA. The 10-layered (PBA-PAH/PVA)10 films constructed using PBA-PAHs containing 16% and 26% PBA residues were stable in aqueous solutions over the range of pH4.0-10.0, whereas the multilayer films composed of PBA-PAHs with 5.9% and 8.3% PBA decomposed at pH8.0 or lower. The pH-sensitive decomposition of the films was rationalized based on the destabilization of the boronate ester bonds in neutral and acidic solutions. In addition, the (PBA-PAH/PVA)10 films decomposed in glucose and fructose solutions as a result of competitive binding of sugars to PBA-PAH in the films. The sugar response of the films depended on the PBA content in PBA-PAH. The (PBA-PAH/PVA)10 films consisting of 16% and 26% PBA-substituted PBA-PAHs are sensitive to physiological relevant level of glucose at pH7.4 while stable in glucose-free solution, suggesting a potential use of the films in constructing glucose-induced delivery systems. PMID:26952449

  2. Quick setting water-compatible furfuryl alcohol polymer concretes

    DOEpatents

    Sugama, Toshifumi; Kukacka, Lawrence E.; Horn, William H.

    1982-11-30

    A novel quick setting polymer concrete composite comprising a furfuryl alcohol monomer, an aggregate containing a maximum of 8% by weight water, and about 1-10% trichlorotoluene initiator and about 20-80% powdered metal salt promoter, such as zinc chloride, based on the weight of said monomer, to initiate and promote polymerization of said monomer in the presence of said aggregate, within 1 hour after mixing at a temperature of -20.degree. C. to 40.degree. C., to produce a polymer concrete having a 1 hour compressive strength greater than 2000 psi.

  3. Properties and Applications of Polyvinyl Alcohol, Halloysite Nanotubes and Their Nanocomposites.

    PubMed

    Gaaz, Tayser Sumer; Sulong, Abu Bakar; Akhtar, Majid Niaz; Kadhum, Abdul Amir H; Mohamad, Abu Bakar; Al-Amiery, Ahmed A

    2015-01-01

    The aim of this review was to analyze/investigate the synthesis, properties, and applications of polyvinyl alcohol-halloysite nanotubes (PVA-HNT), and their nanocomposites. Different polymers with versatile properties are attractive because of their introduction and potential uses in many fields. Synthetic polymers, such as PVA, natural polymers like alginate, starch, chitosan, or any material with these components have prominent status as important and degradable materials with biocompatibility properties. These materials have been developed in the 1980s and are remarkable because of their recyclability and consideration of the natural continuation of their physical and chemical properties. The fabrication of PVA-HNT nanocomposites can be a potential way to address some of PVA's limitations. Such nanocomposites have excellent mechanical properties and thermal stability. PVA-HNT nanocomposites have been reported earlier, but without proper HNT individualization and PVA modifications. The properties of PVA-HNT for medicinal and biomedical use are attracting an increasing amount of attention for medical applications, such as wound dressings, drug delivery, targeted-tissue transportation systems, and soft biomaterial implants. The demand for alternative polymeric medical devices has also increased substantially around the world. This paper reviews individualized HNT addition along with crosslinking of PVA for various biomedical applications that have been previously reported in literature, thereby showing the attainability, modification of characteristics, and goals underlying the blending process with PVA. PMID:26703542

  4. Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix

    SciTech Connect

    Pattabi, Manjunatha . E-mail: manjupattabi@yahoo.com; Saraswathi Amma, B.; Manzoor, K.

    2007-05-03

    Photoluminescence properties of polyvinyl pyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles embedded in polyvinyl alcohol matrix (PVA) are reported. The PVP-CdS nanoparticles are prepared by non-aqueous method wherein cadmium nitrate is used as the cadmium source and hydrogen sulphide as the sulphur source. The synthesized nanoparticles are dispersed in polyvinyl alcohol (PVA) matrix and cast as self-standing flexible (PVP-CdS)-PVA films. The nanocomposites are characterized by optical absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdS particles with average size {approx}3-5 nm. Thermal studies, carried out to observe the changes in PVA matrix due to the incorporation of PVP-CdS nanoparticles show strong interaction between the polymer matrix and nanoparticles. The photoluminescence emission spectra of the nanocomposites show two peaks, at 502 and 636 nm, which are attributed to the band edge and surface defects respectively, of CdS nanoparticles. Effective surface capping with optimum concentration of polyvinyl pyrrolidone leads to the quenching of surface defect-related emission.

  5. Structural, Vibrational, Thermal And Electrical Characterization Of Gamma Radiation-Crosslinked Poly (Vinyl Alcohol)-Based Solid Polymer Electrolytes Blended With LiOH{center_dot}H{sub 2}O Salt

    SciTech Connect

    Khafagy, Rasha M.; Madani, M.; Badr, Y. A.

    2008-09-23

    Solid polymer electrolytes based on poly(vinyl alcohol)(PVA) blended with different concentrations of LiOH{center_dot}H{sub 2}O salt were prepared using casting and {gamma}-irradiation techniques. The structure and blending of the poly-electrolytes were studied by X-ray diffraction (XRD) and Fourier transform Raman spectroscopy. The thermal properties of these solid polymer electrolytes were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The XRD spectra for the electrolytes indicated that the crystalline ratio of PVA decreases with the concentration of Lithium salt. Crystallinity, isotacticity and syndiotacticity percentages were also determined from Raman spectra at different salt concentrations revealing that the crystallinity and the Isotactic regularity of PVA molecule is reduced with salt addition, while the syndiotacticity increases linearly. DSC thermograms showed good accordance with these facts by detecting two melting temperatures corresponding to the two regularities, and these melting points change with the salt content. All characterizing techniques revealed the blend formation between LiOH{center_dot}H{sub 2}O salt and the polymer matrix. To account for the performance of the prepared solid polymer electrolytes, thermally stimulated depolarization current (TSDC) studies of the prepared blends were done. Short circuit TSDC at a polarizing temperature 353 K with a polarizing field of 3 kV cm{sup -1} have been analyzed in the temperature range 300-410 K. Two peaks are evident from the global TSDC measurements on the pure PVA homopolymer. Meanwhile, in all blended samples; there is only one broad peak with a shoulder on the high temperature side due to the relaxation of the poly-blend system. The prepared solid polymer electrolytes showed good charge storage capacity, and moderate current density values near the ambient.

  6. Isothermal and non-isothermal crystallization kinetics of PVA + ionic liquid [BDMIM][BF4]-based polymeric films

    NASA Astrophysics Data System (ADS)

    Saroj, A. L.; Chaurasia, S. K.; Kataria, Shalu; Singh, R. K.

    2016-06-01

    The effect of ionic liquid (IL), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM][BF4], on crystallization behavior of poly(vinyl alcohol) (PVA) has been studied by isothermal and non-isothermal differential scanning calorimetry techniques. The PVA + IL based polymer electrolyte films have been prepared using solution casting technique. To describe the isothermal and non-isothermal crystallization kinetics, several kinetic equations have been employed on PVA + IL based films. There is strong dependence of the peak crystallization temperature (Tc), relative degree of crystallity (Xt), half-time of crystallization (t1/2), crystallization rate constants (Avrami Kt and Tobin AT), and Avrami (n) and Tobin (nT) exponents on the cooling rate and IL loading.

  7. Biobased and biodegradable polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Qiu, Kaiyan

    In this dissertation, various noncrosslinked and crosslinked biobased and biodegradable polymer nanocomposites were fabricated and characterized. The properties of these polymer nanocomposites, and their relating mechanisms and corresponding applications were studied and discussed in depth. Chapter 1 introduces the research background and objectives of the current research. Chapter 2 presents the development of a novel low cost carbon source for bacterial cellulose (BC) production and fabrication and characterization of biobased polymer nanocomposites using produced BC and soy protein based resins. The carbon source, soy flour extract (SFE), was obtained from defatted soy flour (SF) and BC yield achieved using SFE medium was high. The results of this study showed that SFE consists of five sugars and Acetobacter xylinum metabolized sugars in a specific order. Chapter 3 discusses the fabrication and characterization of biodegradable polymer nanocomposites using BC and polyvinyl alcohol (PVA). These polymer nanocomposites had excellent tensile and thermal properties. Crosslinking of PVA using glutaraldehyde (GA) not only increased the mechanical and thermal properties but the water-resistance. Chapter 4 describes the development and characterization of microfibrillated cellulose (MFC) based biodegradable polymer nanocomposites by blending MFC suspension with PVA. Chemical crosslinking of the polymer nanocomposites was carried out using glyoxal to increase the mechanical and thermal properties as well as to make the PVA partially water-insoluble. Chapter 5 reports the development and characterization of halloysite nanotube (HNT) reinforced biodegradable polymer nanocomposites utilizing HNT dispersion and PVA. Several separation techniques were used to obtain individualized HNT dispersion. The results indicated uniform dispersion of HNTs in both PVA and malonic acid (MA) crosslinked PVA resulted in excellent mechanical and thermal properties of the materials, especially

  8. Effect of PVA concentration on bond modifications in PVA-PMMA blend films

    NASA Astrophysics Data System (ADS)

    Tripathi, J.; Tripathi, S.; Sharma, A.; Bisen, R.; Shripathi, T.

    2016-05-01

    The optical properties of poly (methylmethacrylate) (PMMA) polymer are found to be modified when PVA molecules are added in the matrix of PMMA and vice versa making a blend. The concentrations studied were kept low to preserve the original properties of the host. It was seen that PMMA well protects its bonds and dominated the optical properties, while the properties of PVA are comparatively easier to modify when small amount of PMMA is inserted in PVA matrix. The results are interpreted in terms of bond modifications as seen from FTIR and absorption measurements and are useful in understanding the transparency and bandgap of the blend films.

  9. Livestock air treatment using PVA-coated powdered activated carbon biofilter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The efficacy of polyvinyl alcohol (PVA) biofilters was studied using bench-scale biofilters and air from aerobically-treated swine manure. The PVA-coated powdered activated carbon particles showed excellent properties as a biofiltration medium: water holding capacity of 1.39 g H2O/g-dry PVA; wet por...

  10. Nanosecond laser irradiation synthesis of CdS nanoparticles in a PVA system

    NASA Astrophysics Data System (ADS)

    Onwudiwe, Damian C.; Krüger, Tjaart P. J.; Oluwatobi, Oluwafemi S.; Strydom, Christien A.

    2014-01-01

    We herein report a modified, in situ photolytic process for the nucleation and growth of cadmium sulphide nanoparticles in the presence of an optically transparent and semicrystalline polyvinyl alcohol (PVA) polymer matrix. The laser causes a localized decomposition of the precursor species in the immediate vicinity of the polymer leading to highly confined nanocrystals. The as-synthesized PVA-CdS nanocomposite were characterized using UV-vis absorption and photoluminescence spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and powdered X-ray diffraction (XRD). Strong blue shift in the band gap was observed in UV visible absorption spectrum indicating the size confinement. The influence of deposition temperature (25-200 °C) on the optical properties, microstructure, and thermal stability was also investigated. Thermal decomposition behaviors of these composites exhibit decreased thermal stability as indicated by the shift in the decomposition temperature of the pure PVA. XRD patterns revealed a reduction in the crystallinity of the polymer due to the entrapped particles. The nanocomposites showed the existence of both cubic and hexagonal phases.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  12. Interfacial bonding in a CdS/PVA nanocomposite: A Raman scattering study.

    PubMed

    Rudko, Galyna Yu; Kovalchuk, Andrii O; Fediv, Volodymyr I; Chen, Weimin M; Buyanova, Irina A

    2015-08-15

    Raman spectroscopy is employed to characterize the bonding between CdS nanoparticles (NPs) and a polyvinyl alcohol (PVA) as well as structural changes in the polymeric matrix caused by incorporation of NPs. It is shown that after the formation of CdS NPs the vibrations of carbonyl groups in acetate residuals of PVA and of C-O groups at the macromolecules ends disappear. Formation of NPs also leads to an increased degree of hydrogen bonding and crystallinity of the hybrid material as compared with the unloaded polymer. The observed changes are ascribed to the formation of coordinative bonds and hydrogen between the CdS nanoparticles and polymeric macromolecules. The scheme of this interfacial bonding is also proposed. PMID:25910224

  13. Preparation and characterization of poly(vinyl alcohol)/graphene nanofibers synthesized by electrospinning

    NASA Astrophysics Data System (ADS)

    Barzegar, Farshad; Bello, Abdulhakeem; Fabiane, Mopeli; Khamlich, Saleh; Momodu, Damilola; Taghizadeh, Fatemeh; Dangbegnon, Julien; Manyala, Ncholu

    2015-02-01

    We report on the synthesis and characterization of electrospun polyvinyl alcohol (PVA)/graphene nanofibers. The samples produced were characterized by Raman spectroscopy for structural and defect density analysis, scanning electron microscopy (SEM) for morphological analysis, and thermogravimetric (TGA) for thermal analysis. SEM measurements show uniform hollow PVA fibers formation and excellent graphene dispersion within the fibers, while TGA measurements show the improved thermal stability of PVA in the presence of graphene. The synthesized polymer reinforced nanofibers have potential to serve in many different applications such as thermal management, supercapacitor electrodes and biomedical materials for drug delivery.

  14. Suppression of instability by double ablation in tungsten doped polyvinyl alcohol foils

    NASA Astrophysics Data System (ADS)

    Peedikakkandy, Leshma; Chaurasia, S.

    2012-07-01

    In Inertial fusion Energy (IFE) research stable acceleration of fusion targets is a significant problem due to hydrodynamic instabilities. This paper presents the results of the experiments done to investigate the effects of doping 20% of Tungsten (W) (by weight) in Polyvinyl Alcohol (PVA) polymer foils for suppression of instability during laser ablative acceleration. A 20J, 1.060μm, 900ps, Nd: Glass laser system with a focusable intensity of 3 to 9.6×1013W/cm2 was used in the experiment. It is observed that the doped PVA targets yielded stable and enhanced foil acceleration as compared to the undoped PVA foils.

  15. 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).

  16. 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.

  17. 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. PMID:21793217

  18. Comparison of properties of poly(vinyl alcohol) nanocomposites containing two different clays.

    PubMed

    Chang, Jin-Hae; Ham, Miran; Kim, Jeong-Cheol

    2014-11-01

    Morphologies, thermo-optical properties, and gas barriers of poly(vinyl alcohol) (PVA) hybrid films containing two different clays are compared. Saponite (SPT) and hydrophilic bentonite (BTT) were used as the reinforcing filler in the fabrication of PVA hybrid films, which were synthesized from aqueous solutions and were solvent-cast at room temperature under vacuum, yielding 20-31-μm-thick PVA hybrid films with varying clay contents. The addition of small amounts of clay is sufficient to improve the thermal properties and gas barriers of PVA hybrid films. Even polymers with a low clay content (3-10 wt%) were found to exhibit much higher transition temperature values than pure PVA. The addition of BTT was more effective than the addition of SPT for improving the thermal properties and gas barrier in the PVA matrix. The PVA hybrid films containing 5 wt% SPT were equibiaxially stretched, with stretching ratios ranging from 150% to 250%. Clay dispersion, morphology, optical transparency, and gas permeability were then examined as a function of the equibiaxial stretching ratio. PVA hybrid films with a stretching ratio of ≥ 150% displayed homogeneously dispersed clay within the polymer matrix and exfoliated nanocomposites. PMID:25958603

  19. Optical Properties of CdS/PVA Nanocomposite Films Synthesized using the Gamma-Irradiation-Induced Method

    NASA Astrophysics Data System (ADS)

    Alireza, Kharazmi; Elias, Saion; Nastaran, Faraji; Nayereh, Soltani; Arash, Dehzangi

    2013-05-01

    Monodispersed spherical CdS nanoparticles embedded into polyvinyl alcohol (PVA) films are synthesized by using an in-situ gamma-irradiation-induced method. The formation mechanism of CdS nanoparticles capped by two united cells of PVA is purposed by means of surrounding the CdS nanoparticles with OH bonds of the PVA chain. CdS nanoparticles are found to possess an unusual orthorhombic structure in monoclinic crystalline PVA. The polymer matrix affords protection from agglomeration and controls the particle size. It is found that the distribution of the prepared nanoparticles increases and a narrower size distribution is observed when the gamma radiation is varied from 10 to 50 kGy. While the average size of the nanoparticles is found to be less affected by the variation of the gamma radiation doses. The size range of the synthesized nanoparticles is 14±1 nm. The optical absorption spectra of synthesized CdS nanoparticles in a polymer matrix reveal the blue shift in the band gap energy with respect to CdS bulk materials owing to quantum confinement effect. The photoluminescence study of nanocomposite films shows the green emission arising from the crystalline defects.

  20. 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.

  1. Controllable layer-by-layer assembly of PVA and phenylboronic acid-derivatized chitosan.

    PubMed

    Zhang, Dan; Yu, Guanghua; Long, Zhu; Yang, Guihua; Wang, Bin

    2016-04-20

    Phenylboronic acid-derivatized chitosan (chitosan-PBA) were prepared by grafting small molecules bearing phenylboronic acid groups onto chitosan with N-hydroxysuccinimide (NHS) and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) as a coupling reagent pair. Self-assembly multilayer thin films of chitosan-PBA and poly(vinyl alcohol) were subsequently produced under pH control on supporting surfaces, either a silicon wafer or polystyrene latex particles. The driving force of the self-assembly was the ester formation of phenylboronic acid containing polymers with PVA, which can be "turned off" by simple pH control. PMID:26876848

  2. Surface studies of coated polymer microspheres and protein release from tissue-engineered scaffolds.

    PubMed

    Meese, Thomas M; Hu, Yunhua; Nowak, Richard W; Marra, Kacey G

    2002-01-01

    The controlled release of growth factors from porous, polymer scaffolds is being studied for potential use as tissue-engineered scaffolds. Biodegradable polymer microspheres were coated with a biocompatible polymer membrane to permit the incorporation of the microspheres into tissue-engineered scaffolds. Surface studies with poly(D,L-lactic-co-glycolic acid) [PLGA], and poly(vinyl alcohol) [PVA] were conducted. Polymer films were dip-coated onto glass slides and water contact angles were measured. The contact angles revealed an initially hydrophobic PLGA film, which became hydrophilic after PVA coating. After immersion in water, the PVA coating was removed and a hydrophobic PLGA film remained. Following optimization using these 2D contact angle studies, biodegradable PLGA microspheres were prepared, characterized, and coated with PVA. X-ray photoelectron spectroscopy was used to further characterize coated slides and microspheres. The release of the model protein bovine serum albumin from PVA-coated PLGA microspheres was studied over 8 days. The release of BSA from PVA-coated PLGA microspheres embedded in porous PLGA scaffolds over 24 days was also examined. Coating of the PLGA microspheres with PVA permitted their incorporation into tissue-engineered scaffolds and resulted in a controlled release of BSA. PMID:12022746

  3. An intensive study on the optical, rheological, and electrokinetic properties of polyvinyl alcohol-capped nanogold

    NASA Astrophysics Data System (ADS)

    Behera, Manoranjan

    2015-05-01

    Low-temperature-assisted wet chemical synthesis of nanogold (NG) using gold hydroxide, a new precursor salt in the presence of a macroscopic ligand poly(vinyl alcohol) PVA in water in the form of nanofluid, is reported for the first time in this article. In the absorption spectra, the surface Plasmon resonance absorption band in the range of 520-545 nm signifies the formation of NG via a controlled Au3+ + 3e → Au reaction grafted in small assemblies with polymer. Absorption maximum increases nonlinearly with Au-contents up to 100 µM Au in Au-PVA charge-transfer complex. Marked enhancement in the peak intensity of some of the vibration bands of PVA polymer such as C-H stretching, C=O stretching, CH2 bending, and C-C in-plane bending in the presence of NG reveals an interfacial interaction between NG and oxidized PVA via C=O group. Execution of shear thinning behavior regardless of the Au-content strongly suggests that crosslinking exists between NG and PVA in Au-PVA rheo-optical nanofluids. Hydrodynamic diameter and polydispersity index draw a nonlinear path with the Au doping with 30.0 g/L PVA in water over a wide region of 5-100 μM Au covered in this study. Enhancement in the zetapotential of Au-PVA nanofluid over bare PVA in water is ascribed to buildup of nonbonding electrons of "-C=O" moieties from the oxidized PVA on the NG surface. Displaying of lattice fringes in the microscopic image of core-shell Au-PVA nanostructure confirms that crystalline nature of NG core with inter planar spacing 0.235 nm corresponds to Au (111) plane.

  4. UV irradiated PVA-Ag nanocomposites for optical applications

    NASA Astrophysics Data System (ADS)

    Chahal, Rishi Pal; Mahendia, Suman; Tomar, A. K.; Kumar, Shyam

    2015-07-01

    The present paper is focused on the in-situ prepared Poly (vinyl alcohol)-Silver (PVA-Ag) nanocomposites and tailoring their optical properties by means of UV irradiation in such a way that these can be used for anti-reflective coatings and bandpass filters. The reflectance from these irradiated nanocomposites has been found to decrease leading to the increase in refractive index (RI), with increasing UV exposure time, in the entire visible region. Decrease in optical energy gap of PVA film from 4.92 to 4.57 eV on doping with Ag nanoparticles has been observed which reduces further to 4.1 eV on exposure to UV radiations for 300 min. This decrease in optical energy gap can be correlated to the formation of charge transfer complexes within the base polymer network on embedding Ag nanoparticles, which further enhances with increasing exposure time. Such complexes may also be responsible for increased molecular density of the composite films which corresponds to decrease in reflectance corroborating the observed results.

  5. Preparation of patterned ultrathin polymer films.

    PubMed

    Yang, Huige; Su, Meng; Li, Kaiyong; Jiang, Lei; Song, Yanlin; Doi, Masao; Wang, Jianjun

    2014-08-12

    Though patterned ultrathin polymer films (<100 nm) are of great importance in the fields of sensors and nanoelectronic devices, the fabrication of patterned ultrathin polymer films remains a great challenge. Herein, patterned ultrathin polymer films are fabricated facilely on hydrophobic substrates with different hydrophilic outline patterns by the pinning of three-phase contact lines of polymer solution on the hydrophilic outlines. This method is universal for most of the water-soluble polymers, and poly(vinyl alcohol) (PVA) has been selected as a model polymer due to its biocompatibility and good film-forming property. The results indicate that the morphologies of ultrathin polymer films can be precisely adjusted by the size of the hydrophilic outline pattern. Specifically, patterned hydrophilic outlines with sizes of 100, 60, and 40 μm lead to the formation of concave-shaped ultrathin PVA films, whereas uniform ultrathin PVA films are formed on 20 and 10 μm patterned substrates. The controllabilities of morphologies can be interpreted through the influences of the slip length and coffee ring effect. Theoretical analysis shows that when the size of the hydrophilic outline patterns is smaller than a critical value, the coffee ring effect disappears and uniform patterned ultrathin polymer films can be formed for all polymer concentrations. These results provide an effective methodology for the fabrication of patterned ultrathin polymer films and enhance the understanding of the coffee ring effect. PMID:25066958

  6. Local, real-time measurement of drying films of aqueous polymer solutions using active microrheology.

    PubMed

    Komoda, Yoshiyuki; Leal, L Gary; Squires, Todd M

    2014-05-13

    Oscillatory microdisk rheometry was applied to evaluate the evolution of the viscoelastic properties at the surface of a film of an aqueous solution of poly(vinyl alcohol) (PVA) during drying. The drying rate was measured concurrently, based upon measurements of the variation of film thickness. A fully hydrolyzed PVA solution shows a constant drying rate, while a less hydrolyzed PVA solution exhibits a decreased drying rate in the latter part of the drying process, which occurred at the same time as an increase of the elastic modulus. We suggest that this difference in behavior is a consequence of the fact that both the configuration of the PVA molecule and the strength of interaction with water depend on the degree to which the PVA is hydrolyzed. The polymer concentration at the film surface can be estimated from the measured viscosity at the surface for the fully hydrolyzed PVA solution, and this result then can be compared with two theoretical calculations: one in which the polymer concentration is assumed to remain uniform throughout the film, and the other in which the polymer concentration distribution is determined via a one-dimensional diffusion model. This comparison suggests that the polymer is first concentrated locally near the surface but later in the drying process the distribution of polymer becomes increasingly uniform, possibly due to a spontaneously generated convective flow inside the film. PMID:24725080

  7. Broadband tuning in a passively Q-switched erbium doped fiber laser (EDFL) via multiwall carbon nanotubes/polyvinyl alcohol (MWCNT/PVA) saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Hassan, S. N. M.; Ahmad, F.; Zulkifli, M. Z.; Harun, S. W.

    2016-04-01

    An MWCNT/PVA-based Q-switched erbium-doped fiber laser (EDFL) that uses a tunable bandpass filter (TBPF) as the wavelength tuning and filtering mechanism to achieve a broadband tuning range is proposed and demonstrated. The tuning range of the generated Q-switched pulses covered a wide wavelength range of 50 nm, which spanned from 1519 nm to 1569 nm and corresponded to the S- and C-band regions. In addition, the lasing and Q-switching operations had low thresholds of 8.9 mW and 22.4 mW respectively. The highest pulse energy of 52.13 nJ was obtained at an output wavelength of 1569 nm, with a corresponding repetition rate of 26.53 kHz and pulse width of 6.10 μs, at the maximum power of 114.8 mW.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  9. 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. PMID:27106077

  10. Water swelling properties of the electron beam irradiated PVA-g-AAc hydrogels

    NASA Astrophysics Data System (ADS)

    Wang, Qingguo; Zhou, Xue; Zeng, Jinxia; Wang, Jizeng

    2016-02-01

    In this paper, the electron beam irradiation technology being more suitable for the industry application is explored to fabricate the acrylic acid (AAc) monomer-grafted polyvinyl alcohol (PVA-g-AAc) hydrogels. ATR-IR spectra of the PVA-g-AAc hydrogels shows an obvious absorption peak of the sbnd Cdbnd O group at 1701 cm-1, indicating that the AAc monomers were grafted onto the PVA macromolecules. This paper also studied some effects of the mass ratio of PVA/AAc, pH of buffer solution and irradiation dosage on the water swelling properties of the electron beam irradiated PVA-g-AAc hydrogels. The water swelling ratio of PVA-g-AAc hydrogels decreases with increased irradiation dosage and mass ratio of PVA/AAc, whereas swelling ratio increases with increased pH of buffer solution and soaking time. The water-swelling behavior of PVA-g-AAc hydrogels occurred easily in an alkaline environment, particularly in a buffer solution with pH 9.2. Both PVA-g-AAc hydrogels (PVA/AAc = 1/5, w/w) irradiated with 5 kilogray (kGy) and PVA-g-AAc hydrogels (PVA/AAc = 1/1, w/w) irradiated with 15 kGy could easily absorb water and lead to high water swelling ratios (up to about 600%), which are potential candidates to meet the requirements for some biomedical applications.

  11. Linear and nonlinear optical study of pure PVA and CdSe doped PVA nanocomposite

    NASA Astrophysics Data System (ADS)

    Tyagi, Chetna; Sharma, Ambika

    2016-05-01

    This research work reports the synthesis and optical properties of CdSe/PVA polymer nanocomposite (PNC's) prepared by wet chemical co-precipitation method. The transmission spectra obtained from UV-Vis-NIR spectrophotometer has been investigated to determine the optical properties of PNC's. Absorption spectra give the information about energy band gap (Eg) and type of transition. Refractive index (n), extinction coefficient (k) was calculated using well known Swanepoel method. Wemple-Di Domenico model (WDD) has been used to calculate dispersion energy (Ed) and oscillator energy (E0). Boling formula is used to calculate nonlinear refractive index (n2) of CdSe/PVA nanocomposite.

  12. SeO II addition on PVA-based photopolymer for improving photostorage stabilities and diffraction efficiencies

    NASA Astrophysics Data System (ADS)

    Kim, Daeheum; Nam, Seungwoong; Yeo, Seungbyung; Lim, Jiyun

    2006-08-01

    Polyvinyl alcohol/Acrylamide(PVA/AA)based photopolymer systems modified with SeO II crystals were prepared and photostorage characteristics mainly including diffraction efficiencies were examined and compared with pure PVA/AA films using green laser light (532nm). The photosensitive films were composed of polymeric film-forming binder (PVA), monomer (acrylamide, AA), photoinitiator (triethanol amine, TEA), photosensitizer (Eosin YR), and SeO II crystals. The best optical recording characteristics were observed at the composition of: polymer binder (PVA) : AA : TEA : SeO II : Eosin Y = 1.0 : 0.3 : 0.225 : 0.1 : 0.0015. Diffraction efficiencies as high as 85% with energetic sensitivity of 0.5 mW/cm2 have been obtained in the photopolymer film, and the photopolymer film with SeO II showed higher diffraction efficiencies and lower initial sensitivity than the photopolymer film without SeO II. The morphology of SeO II was expected to be nano crystals since they didn't scatter optical lights and didn't show any peaks in X-ray diffraction spectra.

  13. Cell proliferation on PVA/sodium alginate and PVA/poly(γ-glutamic acid) electrospun fiber.

    PubMed

    Yang, Jen Ming; Yang, Jhe Hao; Tsou, Shu Chun; Ding, Chian Hua; Hsu, Chih Chin; Yang, Kai Chiang; Yang, Chun Chen; Chen, Ko Shao; Chen, Szi Wen; Wang, Jong Shyan

    2016-09-01

    To overcome the obstacles of easy dissolution of PVA nanofibers without crosslinking treatment and the poor electrospinnability of the PVA cross-linked nanofibers via electrospinning process, the PVA based electrospun hydrogel nanofibers are prepared with post-crosslinking method. To expect the electrospun hydrogel fibers might be a promising scaffold for cell culture and tissue engineering applications, the evaluation of cell proliferation on the post-crosslinking electrospun fibers is conducted in this study. At beginning, poly(vinyl alcohol) (PVA), PVA/sodium alginate (PVASA) and PVA/poly(γ-glutamic acid) (PVAPGA) electrospun fibers were prepared by electrospinning method. The electrospun PVA, PVASA and PVAPGA nanofibers were treated with post-cross-linking method with glutaraldehyde (Glu) as crosslinking agent. These electrospun fibers were characterized with thermogravimetry analysis (TGA) and their morphologies were observed with a scanning electron microscope (SEM). To support the evaluation and explanation of cell growth on the fiber, the study of 3T3 mouse fibroblast cell growth on the surface of pure PVA, SA, and PGA thin films is conducted. The proliferation of 3T3 on the electrospun fiber surface of PVA, PVASA, and PVAPGA was evaluated by seeding 3T3 fibroblast cells on these crosslinked electrospun fibers. The cell viability on electrospun fibers was conducted with water-soluble tetrazolium salt-1 assay (Cell Proliferation Reagent WST-1). The morphology of the cells on the fibers was also observed with SEM. The results of WST-1 assay revealed that 3T3 cells cultured on different electrospun fibers had similar viability, and the cell viability increased with time for all electrospun fibers. From the morphology of the cells on electrospun fibers, it is found that 3T3 cells attached on all electrospun fiber after 1day seeded. Cell-cell communication was noticed on day 3 for all electrospun fibers. Extracellular matrix (ECM) productions were found and

  14. Graphene nanoribbon-PVA composite as EMI shielding material in the X band.

    PubMed

    Joshi, Anupama; Bajaj, Anil; Singh, Rajvinder; Alegaonkar, P S; Balasubramanian, K; Datar, Suwarna

    2013-11-15

    A very thin graphene nanoribbon/polyvinyl alcohol (GNR/PVA) composite film has been developed which is light weight and requires a very low concentration of filler to achieve electromagnetic interference (EMI) shielding as high as 60 dB in the X band. Atomic force microscope studies show very well conjugated filler concentration in the PVA matrix for varying concentrations of GNR supported by Raman spectroscopy data. The films show 14 orders of increase in conductivity with a GNR concentration of 0.75% [corrected] in PVA. This is possible because of the interconnected GNR network providing a very low percolation threshold as observed from the electrical measurements. Local density of states study of GNR using scanning tunnelling spectroscopy shows the presence of localized states near the Fermi energy. There are multiple advantages of GNR as an EMI shielding material in a polymer matrix. It has good dispersion in water, the conductive network in the composite shows very high electrical conductivity for a very low concentration of GNR and the presence of localized density of states near Fermi energy provides the spin states required for the absorbance of radiation energy in the X band. PMID:24140728

  15. Graphene nanoribbon-PVA composite as EMI shielding material in the X band

    NASA Astrophysics Data System (ADS)

    Joshi, Anupama; Bajaj, Anil; Singh, Rajvinder; Alegaonkar, P. S.; Balasubramanian, K.; Datar, Suwarna

    2013-11-01

    A very thin graphene nanoribbon/polyvinyl alcohol (GNR/PVA) composite film has been developed which is light weight and requires a very low concentration of filler to achieve electromagnetic interference (EMI) shielding as high as 60 dB in the X band. Atomic force microscope studies show very well conjugated filler concentration in the PVA matrix for varying concentrations of GNR supported by Raman spectroscopy data. The films show 14 orders of increase in conductivity with a GNR concentration of 0.0075 wt% in PVA. This is possible because of the interconnected GNR network providing a very low percolation threshold as observed from the electrical measurements. Local density of states study of GNR using scanning tunnelling spectroscopy shows the presence of localized states near the Fermi energy. There are multiple advantages of GNR as an EMI shielding material in a polymer matrix. It has good dispersion in water, the conductive network in the composite shows very high electrical conductivity for a very low concentration of GNR and the presence of localized density of states near Fermi energy provides the spin states required for the absorbance of radiation energy in the X band.

  16. Soft X-ray induced damage in PVA-based membranes in water environment monitored by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Tzvetkov, George; Späth, Andreas; Fink, Rainer H.

    2014-10-01

    The effect of synchrotron X-ray flux in a soft X-ray scanning-transmission microspectroscope (STXM) instrument on the chemical structure of air-filled poly(vinyl alcohol) (PVA) based microbubbles and their stabilizing shell has been examined. Prolonged soft X-ray illumination of the particles in aqueous suspension leads to the breaking of the microbubbles' protective polymer shell and substantial chemical changes. The latter were clarified via a micro-spot C K-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with further respect to the absorbed X-ray doses. Our results revealed a continuous degradation of the PVA network associated with formation of carbonyl- and carboxyl-containing species as well as an increased content of unsaturated bonds. The observed effects must be taken into account in studies of micro- and nanostructured polymer materials utilizing X-rays.

  17. Electrical properties of irradiated PVA film by using ion/electron beam

    NASA Astrophysics Data System (ADS)

    Abdelrahman, M. M.; Osman, M.; Hashhash, A.

    2016-02-01

    Ion/electron beam bombardment has shown great potential for improving the surface properties of polymers. Low-energy charged (ion/electron) beam irradiation of polymers is a good technique to modify properties such as electrical conductivity, structural behavior, and their mechanical properties. This paper reports on the effect of nitrogen and electron beam irradiation on the electrical properties of polyvinyl alcohol (PVA) films. PVA films of 4 mm were exposed to a charged (ion/electron) beam for different treatment times (15, 30, and 60 minutes); the beam was produced from a dual beam source using nitrogen gas with the other ion/electron source parameters optimized. The dielectric loss tangent tan δ , electrical conductivity σ , and dielectric constant \\varepsilon ^' } in the frequency range 100 Hz-100 kHz were measured at room temperature. The variation of dielectric constant and loss tangent as a function of frequency was also studied at room temperature. The dielectric constant was found to be strongly dependent on frequency for both ion and electron beam irradiation doses. The real (\\varepsilon ^' }) and imaginary (\\varepsilon ^' ' }) parts of the dielectric constant decreased with frequency for all irradiated and non-irradiated samples. The AC conductivity showed an increase with frequency for all samples under the influence of both ion and electron irradiation for different times. Photoluminescence (PL) spectral changes were also studied. The formation of clusters and defects (which serve as non-radiative centers on the polymer surface) is confirmed by the decrease in the PL intensity.

  18. Electrical properties of irradiated PVA film by using ion/electron beam

    NASA Astrophysics Data System (ADS)

    Abdelrahman, M. M.; Osman, M.; Hashhash, A.

    2016-02-01

    Ion/electron beam bombardment has shown great potential for improving the surface properties of polymers. Low-energy charged (ion/electron) beam irradiation of polymers is a good technique to modify properties such as electrical conductivity, structural behavior, and their mechanical properties. This paper reports on the effect of nitrogen and electron beam irradiation on the electrical properties of polyvinyl alcohol (PVA) films. PVA films of 4 mm were exposed to a charged (ion/electron) beam for different treatment times (15, 30, and 60 minutes); the beam was produced from a dual beam source using nitrogen gas with the other ion/electron source parameters optimized. The dielectric loss tangent tan δ , electrical conductivity σ , and dielectric constant ɛ ^' } in the frequency range 100 Hz-100 kHz were measured at room temperature. The variation of dielectric constant and loss tangent as a function of frequency was also studied at room temperature. The dielectric constant was found to be strongly dependent on frequency for both ion and electron beam irradiation doses. The real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the dielectric constant decreased with frequency for all irradiated and non-irradiated samples. The AC conductivity showed an increase with frequency for all samples under the influence of both ion and electron irradiation for different times. Photoluminescence (PL) spectral changes were also studied. The formation of clusters and defects (which serve as non-radiative centers on the polymer surface) is confirmed by the decrease in the PL intensity.

  19. 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

    2007-03-01

    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. PMID:17295534

  20. Bioinspired design and macroscopic assembly of poly(vinyl alcohol)-coated graphene into kilometers-long fibers

    NASA Astrophysics Data System (ADS)

    Kou, Liang; Gao, Chao

    2013-05-01

    Nacre is characterized by its excellent mechanical performance due to the well-recognized ``brick and mortar'' structure. Many efforts have been applied to make nacre-mimicking materials, but it is still a big challenge to realize their continuous production. Here, we prepared sandwich-like building blocks of poly(vinyl alcohol) (PVA)-coated graphene, and achieved high-nanofiller-content kilometers-long fibers by continuous wet-spinning assembly technology. The fibers have a strict ``brick and mortar'' layered structure, with graphene sheet as rigid brick and PVA as soft mortar. The mortar thickness can be precisely tuned from 2.01 to 3.31 nm by the weight feed ratio of PVA to graphene, as demonstrated by both atomic force microscopy and X-ray diffraction measurements. The mechanical strength of the nacre-mimicking fibers increases with increasing the content of PVA, and it rises gradually from 81 MPa for the fiber with 53.1 wt% PVA to 161 MPa for the fiber with 65.8 wt% PVA. The mechanical performance of our fibers was independent of the molecular weight (MW) of PVA in the wide range of 2-100 kDa, indicating that low MW polymers can also be used to make strong nanocomposites. The tensile stress of fibers immersed in PVA 5 wt% solution reached ca. 200 MPa, surpassing the values of nacre and most of other nacre-mimicking materials. The nacre-mimicking fibers are highly electrically conductive (~350 S m-1) after immersing in hydroiodic acid, enabling them to connect a circuit to illuminate an LED lamp.Nacre is characterized by its excellent mechanical performance due to the well-recognized ``brick and mortar'' structure. Many efforts have been applied to make nacre-mimicking materials, but it is still a big challenge to realize their continuous production. Here, we prepared sandwich-like building blocks of poly(vinyl alcohol) (PVA)-coated graphene, and achieved high-nanofiller-content kilometers-long fibers by continuous wet-spinning assembly technology. The fibers

  1. Tuning optical and three photon absorption properties in graphene oxide-polyvinyl alcohol free standing films

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Udayabhaskar, R.; Hariharan, S.

    2016-07-01

    We report the optical and nonlinear optical properties of graphene oxide (GO)-polyvinyl alcohol (PVA) free standing films. The composite polymer films were prepared in ex-situ method. The variation in optical absorption spectra and optical constants with the amount of GO loading was noteworthy from the optical absorption spectroscopic studies. Nonlinear optical studies done at 532 nm using 5 ns laser pulses show three photon absorption like behaviour. Both steady state and time resolved fluorescence studies reveal that the GO was functioning as a pathway for the decay of fluorescence from PVA. This is attributed to the energy level modifications of GO through hydroxyl groups with PVA. Raman spectroscopy also supports the interaction between GO and PVA ions through OH radicals.

  2. Retardation Measurements of Infrared PVA Wave plate

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Z, H.; W, D.; D, Y.; Z, Z.; S, J.

    The wave plate made of Polyvinyl Alcohol PVA plastic film has several advantages such as its lower cost and insensitivity to temperature and incidence angle so it has been used in the Solar Multi-Channel Telescope SMCT in China But the important parameter retardations of PVA wave plates in the near infrared wavelength have never been provided In this paper a convenient and high precise instrument to get the retardations of discrete wavelengths or a continuous function of wavelength in near infrared is developed In this method the retardations of wave plates have been determined through calculating the maximum and minimum of light intensity The instrument error has been shown Additionally we can get the continuous direction of wavelength retardations in the ultraviolet visible or infrared spectral in another way

  3. Effect of pullulan/poly(vinyl alcohol) blend system on the montmorillonite structure with property characterization of electrospun pullulan/poly(vinyl alcohol)/montmorillonite nanofibers.

    PubMed

    Islam, Md Shahidul; Yeum, Jeong Hyun; Das, Ajoy Kumar

    2012-02-15

    Nanofibers of the composite of pullulan (PULL), poly(vinyl alcohol) (PVA), and montmorillonite clay (MMT) were prepared using electrospinning method in aqueous solutions. Pullulan is an interesting natural polymer for many of its merits and good properties. Because of biocompatibility and non-toxicity of PVA, it could be used in numerous fields. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were done to characterize the PULL/PVA/MMT nanofibers morphology and properties. XRD patterns and FTIR data demonstrated that there were good interactions between PULL and PVA caused by possibly hydrogen bonds. Moreover, XRD data and TEM images indicated that intercalated and exfoliated MMT nanoplatelets can be obtained within the PULL/PVA/MMT nanofibers depending on the PULL/PVA blend ratios. Furthermore, the thermal stability and mechanical property (tensile strength) of PULL/PVA/MMT nanofibers could be enhanced more by exfoliated MMT nanoplatelets than intercalated structures of that nanoplatelets. PMID:22172694

  4. Effects of PVA coated nanoparticles on human immune cells

    PubMed Central

    Strehl, Cindy; Gaber, Timo; Maurizi, Lionel; Hahne, Martin; Rauch, Roman; Hoff, Paula; Häupl, Thomas; Hofmann-Amtenbrink, Margarethe; Poole, A Robin; Hofmann, Heinrich; Buttgereit, Frank

    2015-01-01

    Nanotechnology provides new opportunities in human medicine, mainly for diagnostic and therapeutic purposes. The autoimmune disease rheumatoid arthritis (RA) is often diagnosed after irreversible joint structural damage has occurred. There is an urgent need for a very early diagnosis of RA, which can be achieved by more sensitive imaging methods. Superparamagnetic iron oxide nanoparticles (SPION) are already used in medicine and therefore represent a promising tool for early diagnosis of RA. The focus of our work was to investigate any potentially negative effects resulting from the interactions of newly developed amino-functionalized amino-polyvinyl alcohol coated (a-PVA) SPION (a-PVA-SPION), that are used for imaging, with human immune cells. We analyzed the influence of a-PVA-SPION with regard to cell survival and cell activation in human whole blood in general, and in human monocytes and macrophages representative of professional phagocytes, using flow cytometry, multiplex suspension array, and transmission electron microscopy. We found no effect of a-PVA-SPION on the viability of human immune cells, but cytokine secretion was affected. We further demonstrated that the percentage of viable macrophages increased on exposure to a-PVA-SPION. This effect was even stronger when a-PVA-SPION were added very early in the differentiation process. Additionally, transmission electron microscopy analysis revealed that both monocytes and macrophages are able to endocytose a-PVA-SPION. Our findings demonstrate an interaction between human immune cells and a-PVA-SPION which needs to be taken into account when considering the use of a-PVA-SPION in human medicine. PMID:26056442

  5. Effects of PVA coated nanoparticles on human immune cells.

    PubMed

    Strehl, Cindy; Gaber, Timo; Maurizi, Lionel; Hahne, Martin; Rauch, Roman; Hoff, Paula; Häupl, Thomas; Hofmann-Amtenbrink, Margarethe; Poole, A Robin; Hofmann, Heinrich; Buttgereit, Frank

    2015-01-01

    Nanotechnology provides new opportunities in human medicine, mainly for diagnostic and therapeutic purposes. The autoimmune disease rheumatoid arthritis (RA) is often diagnosed after irreversible joint structural damage has occurred. There is an urgent need for a very early diagnosis of RA, which can be achieved by more sensitive imaging methods. Superparamagnetic iron oxide nanoparticles (SPION) are already used in medicine and therefore represent a promising tool for early diagnosis of RA. The focus of our work was to investigate any potentially negative effects resulting from the interactions of newly developed amino-functionalized amino-polyvinyl alcohol coated (a-PVA) SPION (a-PVA-SPION), that are used for imaging, with human immune cells. We analyzed the influence of a-PVA-SPION with regard to cell survival and cell activation in human whole blood in general, and in human monocytes and macrophages representative of professional phagocytes, using flow cytometry, multiplex suspension array, and transmission electron microscopy. We found no effect of a-PVA-SPION on the viability of human immune cells, but cytokine secretion was affected. We further demonstrated that the percentage of viable macrophages increased on exposure to a-PVA-SPION. This effect was even stronger when a-PVA-SPION were added very early in the differentiation process. Additionally, transmission electron microscopy analysis revealed that both monocytes and macrophages are able to endocytose a-PVA-SPION. Our findings demonstrate an interaction between human immune cells and a-PVA-SPION which needs to be taken into account when considering the use of a-PVA-SPION in human medicine. PMID:26056442

  6. Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-10-01

    We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

  7. Covalently-layers of PVA and PAA and in situ formed Ag nanoparticles as versatile antimicrobial surfaces.

    PubMed

    Fragal, Vanessa H; Cellet, Thelma S P; Pereira, Guilherme M; Fragal, Elizângela H; Costa, Marco Antonio; Nakamura, Celso Vataru; Asefa, Tewodros; Rubira, Adley F; Silva, Rafael

    2016-10-01

    The in situ synthesis of silver nanoparticles (AgNPs) within covalently-modified poly(ethylene terephthalate) (PET) films possessing ultra-thin layer of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) is successfully demonstrated. The resulting polymeric films are shown to exhibit antimicrobial activities toward Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and fungus (Candida albicans). To make the films, first PET surfaces were subject to photo-oxidation and subsequent solid-state grafting to attach a PVA layer, followed by a PAA layer. To synthesize the AgNPs inside the films, the PVA and PAA-modified PET was soaked in AgNO3 solution and the polymeric film was modified with the Ag(+) ions via Ag(+)-carboxylate interaction, and then the Ag(+) ions-containing polymer film was subject to either photo-reduction or thermal reduction processes. The PVA and PAA thin layers attached by covalent bonds to the PET surface uniquely promoted not only the in situ synthesis but also the stabilization of AgNPs. The formation of the AgNPs was confirmed by UV-vis spectroscopy or by monitoring the surface plasmon resonance (SPR) peak associated with AgNPs. The resulting PVA and PAA ultrathin layers modified and AgNPs containing PET served as bactericide and fungicide, inhibiting the growth of bacteria and fungi on the surfaces. Given PET's versatility and common use in many commercial processes, the method can be used for producing plastic surfaces with versatile antimicrobial and antibacterial properties. PMID:27196366

  8. Polymer growth rate in a wire chamber with oxygen, water, or alcohol gas additives

    NASA Astrophysics Data System (ADS)

    Boyarski, Adam M.

    2009-06-01

    The rate of polymer growth on wires was measured in a wire chamber while the chamber was aged initially with helium:isobutane (80:20) gas, and then with either oxygen, water, or alcohol added to the gas. At the completion of the aging process for each gas mixture, the carbon content on the wires was measured in a scanning electron microscope/energy dispersive X-ray (SEM/EDX) instrument. The same physical wires were used in all the gas mixtures, allowing measurement of polymer build-up or polymer depletion by each gas additive. It is found that the rate of polymer growth is not changed by the presence of oxygen, water, or alcohol. Conjecture that oxygen reduces breakdown by removing polymer deposits on field wires is negated by these measurements. Instead, it appears that the reduced breakdown is due to lower resistance in the polymer from oxygen ions being transported into the polymer. It is also observed that field wires bombarded by the electrons in the SEM and then placed back into the chamber show an abundance of single electrons being emitted, indicating that electron charge is trapped in the polymer layer and that a high electric field is necessary to remove the charge.

  9. Polymer Growth Rate in a Wire Chamber with Oxygen,Water, or Alcohol Gas Additives

    SciTech Connect

    Boyarski, Adam; /SLAC

    2008-07-02

    The rate of polymer growth on wires was measured in a wire chamber while the chamber was aged initially with helium-isobutane (80:20) gas, and then with either oxygen, water, or alcohol added to the gas. At the completion of the aging process for each gas mixture, the carbon content on the wires was measured in a SEM/EDX instrument. The same physical wires were used in all the gas mixtures, allowing measurement of polymer build up or polymer depletion by each gas additive. It is found that the rate of polymer growth is not changed by the presence of oxygen, water or alcohol. Conjecture that oxygen reduces breakdown by removing polymer deposits on field wires is negated by these measurements. Instead, it appears that the reduced breakdown is due to lower resistance in the polymer from oxygen ions being transported into the polymer. It is also observed that field wires bombarded by the electrons in the SEM and then placed back into the chamber show an abundance of single electrons being emitted, indicating that electron charge is stored in the polymer layer and that a high electric field is necessary to remove the charge.

  10. Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks for improving optrode-neural tissue interface in optogenetics.

    PubMed

    Lu, Yi; Li, Yanling; Pan, Jianqing; Wei, Pengfei; Liu, Nan; Wu, Bifeng; Cheng, Jinbo; Lu, Caiyi; Wang, Liping

    2012-01-01

    The field of optogenetics has been successfully used to understand the mechanisms of neuropsychiatric diseases through the precise spatial and temporal control of specific groups of neurons in a neural circuitry. However, it remains a great challenge to integrate optogenetic modulation with electrophysiological and behavioral read out methods as a means to explore the causal, temporally precise, and behaviorally relevant interactions of neurons in the specific circuits of freely behaving animals. In this study, an eight-channel chronically implantable optrode array was fabricated and modified with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks (PEDOT/PSS-PVA/PAA IPNs) for improving the optrode-neural tissue interface. The conducting polymer-hydrogel IPN films exhibited a significantly higher capacitance and lower electrochemical impedance at 1 kHz as compared to unmodified optrode sites and showed significantly improved mechanical and electrochemical stability as compared to pure conducting polymer films. The cell attachment and neurite outgrowth of rat pheochromocytoma (PC12) cells on the IPN films were clearly observed through calcein-AM staining. Furthermore, the optrode arrays were chronically implanted into the hippocampus of SD rats after the lentiviral expression of synapsin-ChR2-EYFP, and light-evoked, frequency-dependant action potentials were obtained in freely moving animals. The electrical recording results suggested that the modified optrode arrays showed significantly reduced impedance and RMS noise and an improved SNR as compared to unmodified sites, which may have benefited from the improved electrochemical performance and biocompatibility of the deposited IPN films. All these characteristics are greatly desired in optogenetic applications, and the fabrication method of conducting polymer-hydrogel IPNs can be easily integrated with other modification methods to build a

  11. UV-responsive polyvinyl alcohol nanofibers prepared by electrospinning

    NASA Astrophysics Data System (ADS)

    Khatri, Zeeshan; Ali, Shamshad; Khatri, Imran; Mayakrishnan, Gopiraman; Kim, Seong Hun; Kim, Ick-Soo

    2015-07-01

    We report UV-responsive polyvinyl alcohol (PVA) nanofibers for potential application for recording and erasing quick response (QR) codes. We incorporate 1‧-3‧-dihydro-8-methoxy-1‧,3‧,3‧-trimethyl-6-nitrospiro [2H-1-benzopyran-2,2‧-(2H)-indole] (indole) and,3-dihydro-1,3,3-trimethylspiro [2H-indole-2,3‧-[3H] phenanthr [9,10-b] (1,4) oxazine] (oxazine) into PVA polymer matrix via electrospinning technique. The resultant nanofibers were measured for recording-erasing, photo-coloration and thermal reversibility. The rate of photo-coloration of PVA-indole nanofibers was five times higher than the PVA-oxazine nanofibers, whereas the thermal reversibility found to be more than twice as fast as PVA-oxazine nanofibers. Results showed that the resultant nanofibers have very good capability of recording QR codes multiple times. The FTIR spectroscopy and SEM were employed to characterize the electrospun nanofibers. The UV-responsive PVA nanofibers have great potentials as a light-driven nanomaterials incorporated within sensors, sensitive displays and in optical devices such as erasable and rewritable optical storage.

  12. Self Nucleation and Crystallization of Poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Thomas, David; Cebe, Peggy

    Polyvinyl alcohol (PVA) is a hydrophilic, biodegradable, semi-crystalline polymer with uses ranging from textiles to medicine. Film samples of PVA were investigated to assess crystallization and melting behavior during self-nucleation experiments, and thermal degradation, using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis, respectively. TG results show that degradation occurred at temperatures close to the observed peak melting temperature of 223 C. Using conventional DSC, PVA was heated at a rate of 10 C/min to various self-nucleation temperatures, Ts, within its melting range, briefly annealed, cooled and reheated. Three distinct crystallization regimes were observed upon cooling, depending upon self nucleation temperature. At low values of Ts, below 227 C, PVA only partially melts; residual crystal anneals while new, less perfect crystals form during cooling. Between 228 C and 234 C, PVA was found to crystallize exclusively by self-nucleation. For Ts above 235 C the PVA melts completely. Fast scanning chip-based calorimetry was used to heat and cool at 2000 K/s, to prevent degradation. Results of self nucleation experiments using fast scanning and conventional DSC will be compared. NSF DMR-1206010.

  13. Holographic characterization of DYE-PVA films studied at 442 nm for optical elements fabrication

    NASA Astrophysics Data System (ADS)

    Couture, Jean J.

    1991-12-01

    The present work is an experimental study of the speed of hologram recording in dichromated polyvinyl alcohol films (DC-PVA) and DYE-DC-PVA films. Real-time recordings give high diffraction efficiency and low signal-to-noise ratio holograms without any chemical development. The dyes studied here are MALACHITE GREEN, EOSIN Y, and ROSE BENGAL introduced in DC-PVA films having a thickness of 60 - 62 micrometers . The best of these DYE-DC-PVA systems is a good candidate for holographic optical elements fabrication.

  14. Chemorheology of aqueous-based alumina-poly(vinyl alcohol) gelcasting suspensions

    SciTech Connect

    Morissette, S.L.; Lewis, J.A.

    1999-03-01

    A new gelcasting system based on aqueous-based alumina-poly(vinyl alcohol) (PVA) suspensions cross-linked by an organotitanate coupling agent has been developed. The chemorheological properties of this system exhibited a strong compositional dependence. A sol-gel phase diagram was established, which yielded the critical titanium concentration ([Ti]{sub c}) required for gelation at a given PVA volume fraction as well as the minimum PVA volume fraction ({Phi}{sub PVA}{sup min} = 0.0245) and titanium concentration ([Ti]{sub min} = 9.984 {times} 10{sup {minus}4} g of Ti/mL) below which gelation was not observed irrespective of solution composition. The gelation time of suspensions of constant PVA volume fraction ({Phi}{sub PVA}{sup soln}) decreased with increased cross-linking agent concentration, temperature, and solids volume fraction. The steady-state viscosity and elastic modulus of polymer solutions ({Phi}{sub PVA}{sup soln} = 0.05) of varying [Ti] were well described by the percolation model, giving scaling exponents of 0.84 and 1.79, respectively. The steady-state elastic modulus of gel-casting suspensions, which provided a measure of their handling strength in the as-gelled state, increased with increased solids volume fraction.

  15. 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

    2015-04-01

    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. PMID:25779354

  16. 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.

  17. Simple and non-toxic fabrication of poly(vinyl alcohol)-patterned polymer surface for the formation of cell patterns

    NASA Astrophysics Data System (ADS)

    Hwang, In-Tae; Jin, Yu-Ran; Oh, Min-Suk; Jung, Chan-Hee; Choi, Jae-Hak

    2014-10-01

    In this study, a facile and non-toxic method for the formation of cell-adhesive poly(vinyl alcohol) (PVA) patterns on the surface of a non-biological polystyrene substrate (NPS) is developed to control cellular micro-organization. PVA thin films spin-coated onto the NPS are selectively irradiated with 150 keV H+ ions through a pattern mask and developed with deionized water to form negative-type PVA patterns. Well-defined stripe patterns of PVA with a width of 100 μm are created on the NPS at a higher fluence than 5 × 1015 ions/cm2, and their surface chemical compositions are changed by ion irradiation without any significant morphological change. Based on the results of the protein adsorption test and in vitro cell culture, cancer cells are preferentially adhered and proliferated onto the more hydrophilic PVA regions of the PVA-patterned NPS, resulting in well-defined cell patterns.

  18. Improvement of a Si solar cell efficiency using pure and Fe3+ doped PVA films

    NASA Astrophysics Data System (ADS)

    Khalifa, N.; Kaouach, H.; Chtourou, R.

    2015-07-01

    One of the most important key driving the economic viability of solar cells is the high efficiency. This research focuses on the enhancement of commercial Si solar cell performance by deposing a pure and Fe3+ doped polyvinyl alcohol (PVA) layer on the top of the Si wafer of the considered cells. The use of such polymer to improve solar cells efficiency is actually a first. The authors will rely on the optical characteristics of the pure and doped PVA films including absorption and emission properties to justify the effect on Si cells. Commercial monocrystalline silicon solar cells of 15 cm2 (0.49 V/460 mA) are used in this work. Films of almost 80 μm of the ferric polymer are deposed on the cells. Films with the same thickness are characterized by UV-Vis spectroscopy and photoluminescent emission of the films is then investigated. The electrical properties of the cells with and without the organometallic layer are evaluated. It will be deduced an important improvement of all electrical parameters, including short-circuit current, open-circuit voltage, fill factor and spatially the conversion efficiency by almost 3%.

  19. Characterization of chitosan composites with synthetic polymers and inorganic additives.

    PubMed

    Lewandowska, Katarzyna

    2015-11-01

    In the present study, the results from thermogravimetric analysis (TGA), contact angle measurements, tensile tests, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of polymer composites containing chitosan (Ch) and montmorillonite (MMT) with and without poly(vinyl alcohol) (PVA) are presented. Measurements of the contact angles for diiodomethane (D) and glycerol (G) on the surfaces of chitosan films, Ch/MMT and Ch/PVA/MMT, were made and surface free energies were calculated. It was found that the wettability of the chitosan/MMT or Ch/PVA/MMT composite films decreased relative to the wettability of chitosan. The microstructure of unmodified polymers and their composites, as observed by SEM and AFM, showed particles that are relatively well dispersed in the polymer matrix. The TGA thermograms and mass loss percentages at different decomposition temperatures showed that the thermal stability of the binary composite slightly decreases upon the addition of PVA. The film mechanical properties such as tensile strength, Young's modulus and tensile strain at break depend on the composition and varied non-uniformly. Both composites possessed a tensile strength and Young's modulus of 27.6-94.3MPa and 1.5-3.5GPa, respectively. The addition of PVA to the composite led to a reduction in tensile strength by approximately 40%. PMID:26253510

  20. Bio-inspired carbon nanotube-polymer composite yarns with hydrogen bond-mediated lateral interactions.

    PubMed

    Beese, Allison M; Sarkar, Sourangsu; Nair, Arun; Naraghi, Mohammad; An, Zhi; Moravsky, Alexander; Loutfy, Raouf O; Buehler, Markus J; Nguyen, SonBinh T; Espinosa, Horacio D

    2013-04-23

    Polymer composite yarns containing a high loading of double-walled carbon nanotubes (DWNTs) have been developed in which the inherent acrylate-based organic coating on the surface of the DWNT bundles interacts strongly with poly(vinyl alcohol) (PVA) through an extensive hydrogen-bond network. This design takes advantage of a toughening mechanism seen in spider silk and collagen, which contain an abundance of hydrogen bonds that can break and reform, allowing for large deformation while maintaining structural stability. Similar to that observed in natural materials, unfolding of the polymeric matrix at large deformations increases ductility without sacrificing stiffness. As the PVA content in the composite increases, the stiffness and energy to failure of the composite also increases up to an optimal point, beyond which mechanical performance in tension decreases. Molecular dynamics (MD) simulations confirm this trend, showing the dominance of nonproductive hydrogen bonding between PVA molecules at high PVA contents, which lubricates the interface between DWNTs. PMID:23548065

  1. EMI shielding and conductivity of carbon nanotube-polymer composites at terahertz frequency.

    PubMed

    Polley, Debanjan; Barman, Anjan; Mitra, Rajib Kumar

    2014-03-15

    We investigate the shielding effectiveness and complex conductivity of single-walled carbon nanotubes (SWNT) distributed in a polyvinyl alcohol (PVA) matrix in the THz frequency range. SWNTs are dispersed in PVA matrices with varying SWNT content (keeping the thickness of SWNT/PVA film constant) using a slow-drying method, and terahertz time-domain spectroscopy (THz-TDS) is performed at room temperature in transmission geometry in the frequency range of 0.3-2.1 THz. The transmittance spectra show a possible application of SWNT/PVA composites as low-bandpass filters in the THz frequency region. Shielding effectiveness of all the samples is measured, and, at a particular probing frequency, they tend to follow a linear relationship with SWNT weight fraction in the polymer matrices. THz conductivity of the composite system is described in the light of a.c. hopping conduction. PMID:24690833

  2. Preparation and properties of polymer solid electrolytes using poly(vinyl alcohol) and thermally resistive poly[arylene(1,3-imidazolidine-2,4,5-trione-1,3-diyl)] as matrix polymers

    SciTech Connect

    Yamamoto, Takakazu; Inami, Minoru; Kanbara, Takaki )

    1994-01-01

    Poly(vinyl alcohol) (PVA) and heat-resistive poly[arylene(1,3-imidazolidine-2,4,5-trione-1,3-diyl)] (poly(parabanic acid), PPA) with a T[sub g] of 350 [degrees]C dissolve alkali metal salts such as Li[CF[sub 3]SO[sub 3

  3. Selective permeability of PVA membranes. I - Radiation-crosslinked membranes

    NASA Technical Reports Server (NTRS)

    Katz, M. G.; Wydeven, T., Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  4. Selective Permeability of PVA Membranes. I: Radiation-Crosslinked Membranes

    NASA Technical Reports Server (NTRS)

    Katz, Moshe G.; Wydeven, Theodore, Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  5. Synthesis and characterization of polyvinyl alcohol based multiwalled carbon nanotube nanocomposites

    NASA Astrophysics Data System (ADS)

    Malikov, E. Y.; Muradov, M. B.; Akperov, O. H.; Eyvazova, G. M.; Puskás, R.; Madarász, D.; Nagy, L.; Kukovecz, Á.; Kónya, Z.

    2014-07-01

    Multiwalled carbon nanotubes were synthesized by chemical vapor deposition over an Fe-Co/alumina catalyst. Nanotubes were then oxidized and grafted with polyvinyl alcohol (PVA). The obtained nanostructure was characterized by Raman spectroscopy, XRD, FTIR, EDX, SEM, TEM and TGA methods. FTIR confirmed the presence of the characteristic peaks of the anticipated ester group. The formation of polymer nanocomposites based on polyvinyl alcohol and multiwalled carbon nanotubes was confirmed by SEM and TEM. High resolution electron micrographs revealed that the primary binding sites for PVA grafting are the sidewall defects of the nanotubes. The novelty of this work is the use of the Fischer esterification reaction for creating the permanent link between the nanotubes and the PVA matrix.

  6. 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. PMID:26351630

  7. 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; 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. PMID:26351630

  8. Technical Note: Preliminary investigations into the use of a functionalised polymer to reduce diffusion in Fricke gel dosimeters

    SciTech Connect

    Smith, S. T. Masters, K.-S.; Hosokawa, K.; Blinco, J. P.; Trapp, J. V.; Crowe, S. B.; Kairn, T.

    2015-12-15

    Purpose: A modification of the existing PVA-FX hydrogel has been made to investigate the use of a functionalised polymer in a Fricke gel dosimetry system to decrease Fe{sup 3+} diffusion. Methods: The chelating agent, xylenol orange, was chemically bonded to the gelling agent, polyvinyl alcohol (PVA) to create xylenol orange functionalised PVA (XO-PVA). A gel was created from the XO-PVA (20% w/v) with ferrous sulfate (0.4 mM) and sulfuric acid (50 mM). Results: This resulted in an optical density dose sensitivity of 0.014 Gy{sup −1}, an auto-oxidation rate of 0.0005 h{sup −1}, and a diffusion rate of 0.129 mm{sup 2} h{sup −1}; an 8% reduction compared to the original PVA-FX gel, which in practical terms adds approximately 1 h to the time span between irradiation and accurate read-out. Conclusions: Because this initial method of chemically bonding xylenol orange to polyvinyl alcohol has inherently low conversion, the improvement on existing gel systems is minimal when compared to the drawbacks. More efficient methods of functionalising polyvinyl alcohol with xylenol orange must be developed for this system to gain clinical relevance.

  9. Rheological Analysis of Polymer Interactions and Ageing of Poly(Methylvinylether-Co-Maleic Anhydride)/Poly(Vinyl Alcohol) Binary Networks and Their Effects on Mucoadhesion.

    PubMed

    Andrews, Gavin P; Laverty, Thomas P; Jones, David S

    2015-12-01

    Polymer blends of poly(vinylalcohol, PVA) and poly(methylvinylether-co-maleic anhydride, PMVE/MA) were formulated and their viscoelastic and mucoadhesive properties characterised. The viscoelastic and mucoadhesive properties were dependent on polymer concentration, molecular weight of PVA and PVA:PMVE/MA ratio. Alteration of these properties allowed platforms to be designed to offer defined rheological and mucoadhesive properties, properties that could not be achieved using monopolymeric platforms. A strong correlation was noted between the modulus of the polymeric blends and mucoadhesion. After storage, the polymeric blends underwent rheological structuring (ageing) with an attendant enhancement of mucoadhesion. In certain blends containing the highest molecular weight of PVA (146-186 kDa), storage ultimately resulted in an increase and then a significant decrease in the rheological and mucoadhesive properties, the latter phenomenon being accredited to polymer recrystallisation. Ageing of the rheological and mucoadhesive properties was modelled using an exponential growth model, allowing predictions of the storage period associated with the maxima in viscoelastic and mucoadhesive properties. These observations highlight the possible implications whenever interactive polymeric blends are employed in drug delivery. Caution is therefore urged whenever a formulation strategy based on interactive polymer blends is employed to ensure that ageing is fully understood and mathematically characterised. PMID:26502109

  10. A Polymer Membrane Containing Fe0 as a Contaminant Barrier

    SciTech Connect

    Shimotori, Tsutomu; Nuxoll, Eric E.; Cussler, Edward L.; Arnold, William A.

    2003-11-03

    A polyvinyl alcohol (PVA) membrane containing iron (Fe0) particles was developed and tested as a model barrier for contaminant containment. Carbon tetrachloride, copper (Cu2+), nitrobenzene, 4-nitroacetophenone, and chromate (CrO4 2-) were selected as model contaminants. Compared with a pure PVA membrane, the Fe0/PVA membrane can increase the breakthrough lag time for Cu2+ and carbon tetrachloride by more than 100 fold. The increase in the lag time was smaller for nitrobenzene and 4-nitroacetophenone which stoichiometrically require more iron and for which the PVA membrane has a higher permeability. The effect of Fe0 was even smaller for CrO4 2- because of its slow reaction. Forty-five percent of the iron, based on the content in the dry membrane prior to hydration, was consumed by reaction with Cu2+ and 19% by reaction with carbon tetrachloride. Similarly, 25%, 17%, and 6% of the iron was consumed by nitrobenzene, 4-nitroacetophenone, and CrO4 2-, respectively. These percentages approximately double when the loss of iron during membrane hydration is considered. The permeability of the Fe0/PVA membrane after breakthrough was within a factor of three for that of pure PVA, consistent with theory. These results suggest that polymer membranes with embedded Fe0 have potential as practical contaminant barriers.

  11. Synthesis of wheat straw cellulose-g-poly (potassium acrylate)/PVA semi-IPNs superabsorbent resin.

    PubMed

    Liu, Jia; Li, Qian; Su, Yuan; Yue, Qinyan; Gao, Baoyu; Wang, Rui

    2013-04-15

    To better use wheat straw and minimize its negative impact on environment, a novel semi-interpenetrating polymer networks (semi-IPNs) superabsorbent resin (SAR) composed of wheat straw cellulose-g-poly (potassium acrylate) (WSC-g-PKA) network and linear polyvinyl alcohol (PVA) was prepared by polymerization in the presence of a redox initiating system. The structure and morphology of semi-IPNs SAR were characterized by means of FTIR, SEM and TGA, which confirmed that WSC and PVA participated in the graft polymerization reaction with acrylic acid (AA). The factors that can influence the water absorption of the semi-IPNs SAR were investigated and optimized, including the weight ratios of AA to WSC and PVA to WSC, the content of initiator and crosslinker, neutralization degree (ND) of AA, reaction temperature and time. The semi-IPNs SAR prepared under optimized synthesis condition gave the best water absorption of 266.82 g/g in distilled water and 34.32 g/g in 0.9 wt% NaCl solution. PMID:23544572

  12. 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. PMID:22905779

  13. Highly conductive quasi-coaxial electrospun quaternized polyvinyl alcohol nanofibers and composite as high-performance solid electrolytes

    NASA Astrophysics Data System (ADS)

    Liao, Guan-Ming; Li, Pin-Chieh; Lin, Jia-Shiun; Ma, Wei-Ting; Yu, Bor-Chern; Li, Hsieh-Yu; Liu, Ying-Ling; Yang, Chun-Chen; Shih, Chao-Ming; Lue, Shingjiang Jessie

    2016-02-01

    Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm-2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

  14. Trypsin coatings on electrospun and alcohol-dispersed polymer nanofibers for trypsin digestion column

    SciTech Connect

    Jun, Seung-Hyun; Chang, Mun Seock; Kim, Byoung Chan; An, Hyo Jin; Lopez-Ferrer, Daniel; Zhao, Rui; Smith, Richard D.; Lee, Sang-Won; Kim, Jungbae

    2010-09-15

    The construction of a trypsin reactor in a chromatography column for rapid and efficient protein digestion in proteomics is described. Electrospun and alcohol-dispersed polymer nanofibers were used for the fabrication of highly stable trypsin coating, which was prepared by a two-step process of covalent attachment and enzyme crosslinking. In a comparative study with the trypsin coatings on asspun and non-dispersed nanofibers, it has been observed that a simple step of alcohol dispersion improved not only the enzyme loading but also the performance of protein digestion. In-column digestion of enolase was successfully performed in less than twenty minutes. By applying the alcohol dispersion of polymer nanofibers, the bypass of samples was reduced by filling up the column with well-dispersed nanofibers, and subsequently, interactions between the protein and the enzymes were improved yielding more complete and reproducible digestions. Regardless of alcohol-dispersion or not, trypsin coating showed better digestion performance and improved performance stability under recycled uses than covalently-attached trypsin. The combination of highly stable trypsin coating and alcoholdispersion of polymer nanofibers has opened up a new potential to develop a trypsin column for on-line and automated protein digestion.

  15. Modification of Novel Conductive PEDOT:Sulfonated Polyimide Nano-Thin Films by Anionic Surfactant and Poly(vinyl alcohol) for Electronic Applications

    NASA Astrophysics Data System (ADS)

    Romyen, Nathavat; Thongyai, Supakanok; Praserthdam, Piyasan; Sotzing, Gregory A.

    2013-12-01

    Conductive poly(3,4-ethylenedioxythiophene):sulfonated polyimide (PEDOT: SPI) nanoscale thin films were successfully developed by addition of anionic surfactant and poly(vinyl alcohol) (PVA) for potential application in electronic devices. In this work, sodium dodecyl sulfate (SDS) surfactant was introduced into PEDOT:SPI aqueous suspensions to improve the dispersion stability of the particles in water, leading to high transparency and low contact angle of PEDOT:SPI thin films. All of the conducting polymer thin films showed high transparency of more than 85% transmission. Conductivity enhancement and good film-formation properties of PEDOT:SPI were achieved by adding various amounts of PVA to each polymer aqueous suspension because of the resulting conformational changes. The highest conductivity of 0.134 S/cm was achieved at 0.08 wt.% PVA in PEDOT:SPI2/SDS/PVA film, increased by a factor of 3.5 compared with the original material. In addition, PVA also improved the thermal stability of the conductive films, as verified by thermogravimetric analysis (TGA). The interactions between conducting polymers, PVA, and SDS surfactant affecting nano-thin film properties were revealed and investigated. Moreover, the interactions between SDS and SPI were proven to be different from those between SDS and poly(styrenesulfonate) (PSS) in conventional PEDOT:PSS solutions.

  16. Morphology and thermal studies of zinc sulfide and cadmium sulfide nanoparticles in polyvinyl alcohol matrix

    NASA Astrophysics Data System (ADS)

    Osuntokun, Jejenija; Ajibade, Peter A.

    2016-09-01

    Zn(II) and Cd(II) metal complexes of 1-cyano-1-carboethoxyethylene-2,2-dithiolato-κS,S'-bis(N,N-dimethylthiourea-κS) have been synthesized and characterized with analytical and spectroscopic techniques. The complexes were thermolysed in hexadecylamine at 200 °C to prepare ZnS and CdS nanoparticles. The nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), and powder X-ray diffraction (p-XRD). TEM images showed spherically shaped nanoparticles, whose sizes are in the range 4.33-7.21 nm for ZnS and 4.95-7.7 nm CdS respectively and XRD confirmed cubic crystalline phases for the nanoparticles. The optical band gap energy evaluated from the absorption spectra are 2.88 eV (430 nm) and 2.81 eV (440 nm) for the ZnS and CdS nanoparticles respectively. The as-prepared metal sulfide nanoparticles were further incorporated into polyvinyl alcohol (PVA) to give ZnS/PVA and CdS/PVA composites. The polymer nanocomposites were studied to investigate their morphology and thermal properties relative to the pure PVA. XRD diffractions indicated that the crystalline phases of the nanoparticles and the sizes in PVA matrices remained unaltered. Infra-red spectra studies revealed interactions between the PVA and the metal sulfide nanoparticles and TGA studies show that the ZnS/PVA and CdS/PVA nanocomposites exhibit better thermal stability than the pure PVA.

  17. Novel electroactive PVA-TOCN actuator that is extremely sensitive to low electrical inputs

    NASA Astrophysics Data System (ADS)

    Wang, Fan; Kim, Si-Seup; Kee, Chang-Doo; Shen, Yun-De; Oh, Il-Kwon

    2014-07-01

    A novel electroactive biopolymer actuator was developed based on a cross-linked ionic networking membrane of TEMPO-oxidized bacterial cellulose nanofibers (TOCNs) and polyvinyl alcohol (PVA). Ionic liquids were added to develop an air-working artificial muscle and to enhance the performance of the PVA-TOCN actuator. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) conducting layers were deposited on the top and bottom surfaces of the PVA-TOCN membrane via a simple dipping and drying method. The electroactive PVA-TOCN actuator under both step and harmonic electrical inputs shows much larger tip displacements and faster bending deformation than the pure TOCN actuator. The cross-linking reaction between PVA and TOCN was observed in the Fourier transform-near-infrared (FT-IR) spectrum of the PVA-TOCN networking membrane. Scanning electron microscopy (SEM), x-ray diffusion (XRD), thermogravimetric analysis (TGA) and tensile and ion conductivity testing results for the PVA-TOCN membrane were compared with those of pristine TOCN. Most important, the PVA-TOCN actuator shows much larger bending deformation under even extremely low input voltages, and this could be attributed to the cross-linking mechanism and the greater flexibility resulting from the synergistic effects between PVA and TOCN.

  18. Synthesis of PVA/PVP hydrogels having two-layer by radiation and their physical properties

    NASA Astrophysics Data System (ADS)

    Park, Kyoung Ran; Nho, Young Chang

    2003-06-01

    In these studies, two-layer hydrogels which consisted of polyurethane membrane and a mixture of polyvinyl alcohol(PVA)/poly- N-vinylpyrrolidone(PVP)/glycerin/chitosan were made for the wound dressing. Polyurethane was dissolved in solvent, the polyurethane solution was poured on the mould, and then dried to make the thin membrane. Hydrophilic polymer solutions were poured on the polyurethane membranes, they were exposed to gamma irradiation or two steps of 'freezing and thawing' and gamma irradiation doses to make the hydrogels. The physical properties such as gelation, water absorptivity, and gel strength were examined to evaluate the hydrogels for wound dressing. The physical properties of hydrogels such as gelation and gel strength was greatly improved when polyurethane membrane was used as a covering layer of hydrogel, and the evaporation speed of water in hydrogel was reduced.

  19. The role of free volume in the twisted intramolecular charge transfer (TICT) emission of dimethylaminobenzonitrile and related compounds in rigid polymer matrices

    NASA Astrophysics Data System (ADS)

    Al-Hassan, Khader A.; Azumi, Tohru

    1988-04-01

    The amount of free volume present in a polymer matrix represents a driving force toward twisted intramolecular charge transfer (TICT) emission of p-dimethylaminobenzonitrile (DMABN) and related compounds. The intensity of the TICT band for these compounds in PVC (poly(vinyl chloride), PVA (poly(vinyl alcohol)), PHEMA (poly(hydroxyethyl methacrylate)) and PMMA (poly(methyl methacrylate)) was found to increase in this order, which is consistent with the increased free volume present in the same sequence. This rules out specific solute-solvent interactions as being responsible for the TICT emission in PVA polymer matrices.

  20. Effects of MWNT nanofillers on structures and properties of PVA electrospun nanofibres

    NASA Astrophysics Data System (ADS)

    Naebe, Minoo; Lin, Tong; Tian, Wendy; Dai, Liming; Wang, Xungai

    2007-06-01

    In this study, we have electrospun poly(vinyl alcohol)(PVA) nanofibres and PVA composite nanofibres containing multi-wall carbon nanotubes (MWNTs) (4.5 wt%), and examined the effect of the carbon nanotubes and the PVA morphology change induced by post-spinning treatments on the tensile properties, surface hydrophilicity and thermal stability of the nanofibres. Through differential scanning calorimetry (DSC) and wide-angle x-ray diffraction (WAXD) characterizations, we have observed that the presence of the carbon nanotubes nucleated crystallization of PVA in the MWNTs/PVA composite nanofibres, and hence considerably improved the fibre tensile strength. Also, the presence of carbon nanotubes in PVA reduced the fibre diameter and the surface hydrophilicity of the nanofibre mat. The MWNTs/PVA composite nanofibres and the neat PVA nanofibres responded differently to post-spinning treatments, such as soaking in methanol and crosslinking with glutaric dialdehyde, with the purpose of increasing PVA crystallinity and establishing a crosslinked PVA network, respectively. The presence of carbon nanotubes reduced the PVA crystallization rate during the methanol treatment, but prevented the decrease of crystallinity induced by the crosslinking reaction. In comparison with the crosslinking reaction, the methanol treatment resulted in better improvement in the fibre tensile strength and less reduction in the tensile strain. In addition, the presence of carbon nanotubes reduced the onset decomposition temperature of the composite nanofibres, but stabilized the thermal degradation for the post-spinning treated nanofibres. The MWNTs/PVA composite nanofibres treated by both methanol and crosslinking reaction gave the largest improvement in the fibre tensile strength, water contact angle and thermal stability.

  1. High-Performance Carbon Nanotube/Polymer Composite Fiber from Layer-by-Layer Deposition.

    PubMed

    Wu, Min Le; Chen, Yun; Zhang, Liang; Zhan, Hang; Qiang, Lei; Wang, Jian Nong

    2016-03-30

    So far, preparation of high-performance carbon nanotube (CNT)/polymer composites still faces big challenges mainly due to the limited control of CNT dispersion, fraction, and alignment in polymers. Here, a new "layer-by-layer deposition" method is put forward for preparing CNT/polymer composite fibers using poly(vinyl alcohol) (PVA) as an exemplary polymer. This is based on the continuous production of a hollow cylindrical CNT assembly from a high temperature reactor and its shrinking by a PVA-containing solution and deposition on a removable substrate wire. The in situ mixing of the two composite components at the molecular level allows CNTs to disperse and PVA to infiltrate into the fiber efficiently. As a result, remarkable effects of the CNT reinforcement on the PVA matrix are observed, including a strength improvement from ∼50 to 1255 MPa and electrical conductivity from ∼0 to 1948 S cm(-1). The new method offers good controllability of CNT dispersion and fraction in the polymer matrix, variability for making composite fibers using different polymers, and suitability for scaled up production. This study thus provides a new research direction for preparing CNT-reinforced composites and future performance maximization. PMID:26959406

  2. Luminescent microstructures in bulk and thin films of PMMA, PDMS, PVA, and PS fabricated using femtosecond direct writing technique

    NASA Astrophysics Data System (ADS)

    Deepak, K. L. N.; Kuladeep, R.; Venugopal Rao, S.; Narayana Rao, D.

    2011-02-01

    We present here the luminescent properties of microstructures obtained through femtosecond (fs) laser direct writing (LDW) in bulk, and thin films of polymers such as poly methyl methacrylate (PMMA), poly dimethyl siloxane (PDMS), polystyrene (PS), and poly vinyl alcohol (PVA). We report the transmission, emission, excitation, laser confocal and ESR data from the modified regions acquired with the intention of understanding the fs irradiation effects in these polymers. Formation of different optical centers in the laser irradiated regions has been identified as the reason for emission characteristics which are dependent on the excitation source. Such emitting microstructures demonstrate their utility in memory based devices. ESR studies reveal the existence of peroxide type free radicals in PMMA, PDMS and PS after fs laser irradiation.

  3. Active surfaces engineered by immobilizing protein-polymer nanoreactors for selectively detecting sugar alcohols.

    PubMed

    Zhang, Xiaoyan; Lomora, Mihai; Einfalt, Tomaz; Meier, Wolfgang; Klein, Noreen; Schneider, Dirk; Palivan, Cornelia G

    2016-05-01

    We introduce active surfaces generated by immobilizing protein-polymer nanoreactors on a solid support for sensitive sugar alcohols detection. First, such selective nanoreactors were engineered in solution by simultaneous encapsulation of specific enzymes in copolymer polymersomes, and insertion of membrane proteins for selective conduct of sugar alcohols. Despite the artificial surroundings, and the thickness of the copolymer membrane, functionality of reconstituted Escherichia coli glycerol facilitator (GlpF) was preserved, and allowed selective diffusion of sugar alcohols to the inner cavity of the polymersome, where encapsulated ribitol dehydrogenase (RDH) enzymes served as biosensing entities. Ribitol, selected as a model sugar alcohol, was detected quantitatively by the RDH-nanoreactors with GlpF-mediated permeability in a concentration range of 1.5-9 mM. To obtain "active surfaces" for detecting sugar alcohols, the nanoreactors optimized in solution were then immobilized on a solid support: aldehyde groups exposed at the compartment external surface reacted via an aldehyde-amino reaction with glass surfaces chemically modified with amino groups. The nanoreactors preserved their architecture and activity after immobilization on the glass surface, and represent active biosensing surfaces for selective detection of sugar alcohols, with high sensitivity. PMID:26950167

  4. Electromechanical properties of nanotube PVA composite actuator bimorphs

    NASA Astrophysics Data System (ADS)

    Bartholome, Christèle; Derré, Alain; Roubeau, Olivier; Zakri, Cécile; Poulin, Philippe

    2008-08-01

    Oxidized multiwalled carbon nanotube (oxidized-MWNT)/polyvinyl alcohol (PVA) composite sheets have been prepared for electromechanical actuator applications. MWNT have been oxidized by nitric acid treatments. They were then dispersed in water and mixed with various amounts of PVA of high molecular weight (198 000 g mol-1). The composite sheets were then obtained through a membrane filtration process. The composition of the systems has been optimized to combine suitable mechanical and electrical properties. Thermogravimetric analysis, mechanical tensile tests and conductivity measurements show that the best compromise of mechanical and electrical properties was obtained for a PVA weight fraction of about 30 wt%. In addition, one face of the sheets was coated with gold to increase the conductivity of the sheets and promote uniform actuation. Pseudo-bimorph devices have been realized by subsequently coating the composite sheets with an inert layer of PVA. The devices have been tested electromechanically in a liquid electrolyte (tetrabutylammonium/tetrafluoroborate (TBA/TFB) in acetonitrile) at constant frequency and different applied voltages, from 2 to 10 V. Measurements of the bimorph deflections were used to determine the stress generated by the nanotube-PVA sheets. The results show that the stress generated increases with increasing amplitude of the applied voltage and can reach 1.8 MPa. This value compares well with and even exceeds the stress generated by recently obtained bimorphs made of gold nanoparticles.

  5. Thiazole yellow G dyed PVA films for optoelectronics: microstructrural, thermal and photophysical studies

    NASA Astrophysics Data System (ADS)

    Hebbar, Vidyashree; Bhajantri, R. F.; Naik, Jagadish; Rathod, Sunil G.

    2016-07-01

    In this paper, we report the microstructural, optical and fluorescence properties of poly(vinyl alcohol) (PVA)/Thiazole Yellow G (TY) dye composite prepared by solvent casting. The formation of change-transfer complex as a result of the interaction between the dye molecules and polymer chain is confirmed in FTIR, FT-Raman, XRD and DSC studies. SEM studies present the morphology of the samples. The UV-visible absorption spectra possess characteristic peaks of the TY dye corresponding to n-π* transition along with a characteristic peak of PVA. The composites exhibit the decreasing energy gap and increasing refractive index with an increase in wt.% of the TY dye. The fluorescence-quenching phenomena are observed in emission wavelength range of 391–406 nm upon excitation in the vicinity of absorption maxima (335 nm) with the quantum yield of 0.72 for lowest concentration of dye. The prepared composites bear high brightness, and improved thermal stability, which make them a promising material for sensors and optoelectronic applications.

  6. 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

  7. Nonlinear optical properties of ZnO/poly (vinyl alcohol) nanocomposite films

    NASA Astrophysics Data System (ADS)

    Jeeju, P. P.; Jayalekshmi, S.; Chandrasekharan, K.

    2014-01-01

    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

  8. Effect of polyvinyl alcohol concentration in spinning dope on diameter, beads and HHS of produced nanofibers.

    PubMed

    Khajavi, Ramin; Damerchely, Rogheih

    2007-01-15

    In this study it was aimed to produce nano fibers of poly vinyl alcohol PVA polymer via electrospinning ES method and to investigate the role of PVA concentration in the spinning dope on diameter, beads and HHS of produced fibers. Spinning dopes with different concentrations of PVA at rang of 5 to 20% (wt/wt on weight of solution) prepared. The requisite voltage for ES (30 kv) was supplied by a DC high voltage power supply and for collecting the fibers a grounded aluminum foil target placed 17 cm below the tip of capillary tube (spinning nozzle). The results showed that spinning dopes with PVA concentration between 8 to 12% (wt/wt) are capable of producing PVA fibers, but those below 8% (wt/wt) concentrations because of low viscosity formed droplets known as electrospray effect. Electrospinning suppressed at spinning dope concentrations above 12% (wt/wt) due to high viscosity of dope. According to the SEM photographs of electrospun PVA fibers it revealed that in higher concentrations produced nanofibers have larger diameter with less beads and HHS in compare with lower concentrations. PMID:19070034

  9. Growth of MgO on multi-layered graphene and Mg in PVA matrix

    NASA Astrophysics Data System (ADS)

    Marka, Sandeep K.; Mohiddon, Md. Ahamad; Prasad, Muvva D.; Srikanth, Vadali V. S. S.

    2015-07-01

    An easy and low temperature in-situ growth of MgO micro-rods on multi-layered graphene (MLG) in poly vinyl alcohol (PVA) matrix is elucidated. MLG decked with nanosized fragments of MgO and PVA are used as the starting materials to form MgO micro-rods (width = ∼1 μm and length = ∼4 μm) and MLG filled PVA composite film. Simple solution mixing, spin coating and simple drying processes are used to obtain the PVA composite. The growth mechanism of MgO micro-rods and the role of PVA in the growth of MgO micro-rods are explained on the basis of the observed morphological, structural and phase characteristics and a further controlled synthesis experiment, respectively.

  10. Lipase entrapment in PVA/Chitosan biodegradable film for reactor coatings.

    PubMed

    Batista, Karla A; Lopes, Flavio Marques; Yamashita, Fabio; Fernandes, Kátia Flávia

    2013-04-01

    This study reports the development and characterization of novel biodegradable film, based on chitosan and polyvinyl alcohol containing lipase entrapped. The films showed a thickness of 70.4 and 79 μm to PVA/Chitosan and PVA/Chitosan/Lipase, respectively. The entrapment of lipase in PVA/Chitosan film resulted in increasing of 69.4% tensile strength (TS), and 52.4% of elongation. SEM images showed the formation of a continuous film, without pores or cracks. The lipase entrapment efficiency was estimated in 92% and the films were repeatedly used for 25 hydrolytic cycles, maintaining 62% of initial activity. The PVA/Chitosan/Lipase film was used for olive oil hydrolysis of high performance. These results indicate that PVA/Chitosan/Lipase is a promising material for biotechnology applications such as triacylglycerol hydrolysis and biodiesel production. PMID:23827626

  11. Biocompatibility and hemocompatibility of polyvinyl alcohol hydrogel used for vascular grafting--In vitro and in vivo studies.

    PubMed

    Alexandre, Nuno; Ribeiro, Jorge; Gärtner, Andrea; Pereira, Tiago; Amorim, Irina; Fragoso, João; Lopes, Ascensão; Fernandes, João; Costa, Elísio; Santos-Silva, Alice; Rodrigues, Miguel; Santos, José Domingos; Maurício, Ana Colette; Luís, Ana Lúcia

    2014-12-01

    Polyvinyl alcohol hydrogel (PVA) is a synthetic polymer with an increasing application in the biomedical field that can potentially be used for vascular grafting. However, the tissue and blood-material interactions of such gels and membranes are unknown in detail. The objectives of this study were to: (a) assess the biocompatibility and (b) hemocompatibility of PVA-based membranes in order to get some insight into its potential use as a vascular graft. PVA was evaluated isolated or in copolymerization with dextran (DX), a biopolymer with known effects in blood coagulation homeostasis. The effects of the mesenchymal stem cells (MSCs) isolated from the umbilical cord Wharton's jelly in the improvement of PVA biocompatibility and in the vascular regeneration were also assessed. The biocompatibility of PVA was evaluated by the implantation of membranes in subcutaneous tissue using an animal model (sheep). Histological samples were assessed and the biological response parameters such as polymorphonuclear neutrophilic leucocytes and macrophage scoring evaluated in the implant/tissue interface by International Standards Office (ISO) Standard 10993-6 (annex E). According to the scoring system based on those parameters, a total value was obtained for each animal and for each experimental group. The in vitro hemocompatibility studies included the classic hemolysis assay and both human and sheep bloods were used. Relatively to biocompatibility results, PVA was slightly irritant to the surrounding tissues; PVA-DX or PVA plus MSCs groups presented the lowest score according to ISO Standard 10993-6. Also, PVA was considered a nonhemolytic biomaterial, presenting the lowest values for hemolysis when associated to DX. PMID:24488670

  12. Effects of PVA organic binder on electric properties of CaCu3Ti4O12 ceramics

    NASA Astrophysics Data System (ADS)

    Yuan, Wen-Xiang; Li, Z. J.

    2012-04-01

    CaCu3Ti4O12 ceramics with incorporation of polyvinyl alcohol (PVA) are prepared from the powder synthesized by a solid state reaction. Their electric and dielectric properties are investigated in this study. It is found that adding PVA can dramatically reduce the dielectric loss of CCTO in the low frequency region, and stabilize the dependence of dielectric constant on the measuring frequency. The minimum dielectric loss of 0.045 is obtained from the sample with 8 wt% PVA. The nonlinear coefficient (α) and breakdown electric field (Eb) increase with an increase of PVA binder.

  13. Alcohol

    MedlinePlus

    ... How Can I Help a Friend Who Cuts? Alcohol KidsHealth > For Teens > Alcohol Print A A A ... you can make an educated choice. What Is Alcohol? Alcohol is created when grains, fruits, or vegetables ...

  14. Evaluation of a relationship between polymer bulk hydroxyl and surface oxygen content and in vitro serum - material interaction

    SciTech Connect

    Sawada, Koji; Shimoyama, Takashi ); Malchesky, P.S.; Goldcamp, J.B.; Omokawa, Susumu )

    1993-04-01

    To evaluate serum-material interaction for six types of minimodule and to assess the relationship between the interaction and chemical composition, notably bulk polymer hydroxyl ([minus]OH) percent of polymer, or surface oxygen (SO) percent, polymeric membranes with varying [minus]OH and SO percents were evaluated with normal human serum. The membrane materials ([minus]OH percent and SO percent) evaluated included polypropylene (PP; 0% and 1.9%), polyvinyl alcohol (PVA; 23.7% and 27.3%), ethylene vinyl alcohol (EVAL 4A and D; 30.4% and 25.3%), Cuprophan (CP; 31.5% and 37.4%), and Hemophan (HP; 30.9% and 23.6%), respectively. Data from serum perfusions expressed as percent changes to sham perfusion showed that solute percent decreases were less than 10% in all materials except PVA (10-22%). PVA and CP had higher C3a, C4a, and C5a, and C3a concentration increases, and had larger suppressive effects for all three mitogen-induced mononuclear cell transformation functions (MNCTF) and concanavalin A-induced MNCTF, respectively. PVA had higher SO percent than EVAL and CP was higher than HP, despite PVA and CP having lower or comparable bulk [minus]OH percent to EVAL or HP.

  15. Fabrication of electrospun almond gum/PVA nanofibers as a thermostable delivery system for vanillin.

    PubMed

    Rezaei, Atefe; Tavanai, Hossein; Nasirpour, Ali

    2016-10-01

    In this study, the fabrication of vanillin incorporated almond gum/polyvinyl alcohol (PVA) nanofibers through electrospinning has been investigated. Electrospinning of only almond gum was proved impossible. It was found that the aqueous solution of almond gum/PVA (80:20, concentration=7% (w/w)) containing 3% (w/w) vanillin could have successfully electrospun to uniform nanofibers with diameters as low as 77nm. According to the thermal analysis, incorporated vanillin in almond gum/PVA nanofibers showed higher thermal stability than free vanillin, making this composite especially suitable for high temperature applications. XRD and FTIR analyses proved the presence of vanillin in the almond gum/PVA nanofibers. It was also found that vanillin was dispersed as big crystallites in the matrix of almond gum/PVA nanofibers. FTIR analysis showed almond gum and PVA had chemical cross-linking by etheric bonds between COH groups of almond gum and OH groups of PVA. Also, in the nanofibers, there were no major interaction between vanillin and either almond gum or PVA. PMID:27267574

  16. Construction of chitin/PVA composite hydrogels with jellyfish gel-like structure and their biocompatibility.

    PubMed

    He, Meng; Wang, Zhenggang; Cao, Yan; Zhao, Yanteng; Duan, Bo; Chen, Yun; Xu, Min; Zhang, Lina

    2014-09-01

    High strength chitin/poly(vinyl alcohol) (PVA) composite hydrogels (RCP) were constructed by adding PVA into chitin dissolved in a NaOH/urea aqueous solution, and then by cross-linking with epichlorohydrin (ECH) and freezing-thawing process. The RCP hydrogels were characterized by field emission scanning electron microscopy, FTIR, differential scanning calorimetry, solid-state (13)C NMR, wide-angle X-ray diffraction, and compressive test. The results revealed that the repeated freezing/thawing cycles induced the bicrosslinked networks consisted of chitin and PVA crystals in the composite gels. Interestingly, a jellyfish gel-like structure occurred in the RCP75 gel with 25 wt % PVA content in which the amorphous and crystalline PVA were immobilized tightly in the chitin matrix through hydrogen bonding interaction. The freezing/thawing cycles played an important role in the formation of the layered porous PVA networks and the tight combining of PVA with the pore wall of chitin. The mechanical properties of RCP75 were much higher than the other RCP gels, and the compressive strength was 20× higher than that of pure chitin gels, as a result of broadly dispersing stress caused by the orderly multilayered networks. Furthermore, the cell culture tests indicated that the chitin/PVA composite hydrogels exhibited excellent biocompatibility and safety, showing potential applications in the field of tissue engineering. PMID:25077674

  17. Novel ionically crosslinked acrylamide-grafted poly(vinyl alcohol)/sodium alginate/sodium carboxymethyl cellulose pH-sensitive microspheres for delivery of Alzheimer's drug donepezil hydrochloride: Preparation and optimization of release conditions.

    PubMed

    Bulut, Emine; Şanlı, Oya

    2016-01-01

    In this work, the graft copolymer, poly(vinyl alcohol)-grafted polyacrylamide (PVA-g-PAAm), was synthesized and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and elemental analysis. Microspheres of PVA-g-PAAm/sodium alginate (NaAlg)/sodium carboxymethyl cellulose (NaCMC) were prepared by the emulsion-crosslinking method and used for the delivery of an Alzheimer's drug, donepezil hydrochloride (DP). The release of DP increased with the increase in drug/polymer ratio (d/p) and PVA-g-PAAm/NaAlg/NaCMC ratio, while it decreased with the increase in the extent of crosslinking. The optimum DP release was obtained as 92.9% for a PVA-g-PAAm/NaAlg/NaCMC ratio of 1/2/1, d/p ratio of 1/8, and FeCl3 concentration of 7% (w/v). PMID:25301684

  18. Dancing on coke: smuggling cocaine dispersed in polyvinyl alcohol.

    PubMed

    van Nuijs, Alexander L N; Maudens, Kristof E; Lambert, Willy E; Van Calenbergh, Serge; Risseeuw, Martijn D P; Van hee, Paul; Covaci, Adrian; Neels, Hugo

    2012-01-01

    Recent trends suggest that cocaine smugglers have become more and more inventive to avoid seizures of large amounts of cocaine transported between countries. We report a case of a mail parcel containing a dance pad which was seized at the Customs Department of Brussels Airport, Belgium. After investigation, the inside of the dance pad was found to contain a thick polymer, which tested positive for cocaine. Analysis was performed using a routine colorimetric swipe test, gas chromatography coupled with mass spectrometry and nuclear magnetic resonance spectroscopy. The polymer was identified as polyvinyl alcohol (PVA) and contained 18% cocaine, corresponding to a street value of € 20,000. Laboratory experiments showed that cocaine could be easily extracted from the PVA matrix. This case report reveals a new smuggling technique for the transportation of large amounts of cocaine from one country to another. PMID:22040352

  19. Microstructure characteristics of concrete incorporating metakaolin and PVA fibers and influence on the compressive strength

    NASA Astrophysics Data System (ADS)

    Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2015-07-01

    In this paper, microstructure of concrete is investigated using metakaolin (MK) as cement replacing material and Polyvinyl Alcohol (PVA) fibers. Total ten (10) mixes of concrete are examined by varying PVA fiber aspect ratio. It was found that MK refines the pore structure, improves interfacial transition zone (ITZ) due to its pozzolanic effects, reduces portlandite (Ca(OH)2) content and bridges the gap between matrix and aggregates due to finer particle size. Due to improvement in ITZ, the compressive strength was improved. There was no indication of Ca(OH)2 around the PVA fibers in the presence of MK and the interface between the fiber and matrix was observed very narrow.

  20. Effect of soluble polymer binder on particle distribution in a drying particulate coating.

    PubMed

    Buss, Felix; Roberts, Christine C; Crawford, Kathleen S; Peters, Katharina; Francis, Lorraine F

    2011-07-01

    Soluble polymer is frequently added to inorganic particle suspensions to provide mechanical strength and adhesiveness to particulate coatings. To engineer coating microstructure, it is essential to understand how drying conditions and dispersion composition influence particle and polymer distribution in a drying coating. Here, a 1D model revealing the transient concentration profiles of particles and soluble polymer in a drying suspension is proposed. Sedimentation, evaporation and diffusion govern particle movement with the presence of soluble polymer influencing the evaporation rate and solution viscosity. Results are summarized in drying regime maps that predict particle accumulation at the free surface or near the substrate as conditions vary. Calculations and experiments based on a model system of poly(vinyl alcohol) (PVA), silica particles and water reveal that the addition of PVA slows the sedimentation and diffusion of the particles during drying such that accumulation of particles at the free surface is more likely. PMID:21497825

  1. PVA/K2Ti6O13 synthetic composite for dielectric applications

    NASA Astrophysics Data System (ADS)

    Pandey, Mayank; Joshi, Girish M.; Khutia, Moumita; Rao, N. Madhusudhana; Kaleemulla, S.; Ramesh Kumar, C.; Cuberes, M. Teresa

    2016-05-01

    We demonstrated the preparation of polyvinyl alcohol (PVA) /Potassium titanate (K2Ti6O13) synthetic composite by solution blending. The loading of K2Ti6O13 well dispersed in PVA and improved electrical performance. The dielectric constant and loss as a function of temperature were recorded under frequency (200Hz-1 kHz). The real dielectric constant value obtained is (ɛ=1000) feasible for various electronic and non-conventional energy applications.

  2. A new fabrication route for PVA/graphene platelets composites with enhanced functionalities

    NASA Astrophysics Data System (ADS)

    Lavecchia, Teresa; Tamburri, Emanuela; Angjellari, Mariglen; Savi, Damiano; Terranova, Maria Letizia

    2016-05-01

    This work deals with the synthesis and characterization of composites made of poly(vinyl alcohol) (PVA) and oxidized graphene platelets obtained from an ad hoc treatment of graphite. The composite is produced by a modified solution mixing procedure in which the in situ crosslinking of PVA with maleic anhydride has been carried out in the presence of the carbon filler. A complete characterization of the material is presented carried out by SEM, DTGA, Raman spectroscopy and I-V characteristics analysis.

  3. Development of poly(vinyl alcohol) porous scaffold with high strength and well ciprofloxacin release efficiency.

    PubMed

    Zhou, Xue-Hua; Wei, Dai-Xu; Ye, Hai-Mu; Zhang, Xiaocan; Meng, Xiaoyu; Zhou, Qiong

    2016-10-01

    Hydrophilic porous polymer scaffolds have shown great application in drug controlled release, while their mechanical properties and release efficiency still need further improvement. In the current study, the porous scaffolds of polyvinyl alcohol (PVA) prepared by quenching in liquid nitrogen and freeze drying method from different original concentration aqueous solutions were fabricated. Among different PVA scaffolds, the scaffold stemming from 18wt.% PVA aqueous solution exhibited the best mechanical properties, 10.5 and 1.54MPa tensile strengths for the dry and hydrogel states respectively. The inner morphology of such PVA scaffold was unidirectional honeycomb-like structure with average microchannel section of 0.5μm, and the scaffold showed porosity of 71% and rather low ciprofloxacin (Cip) release efficiency of 54.5%. Then poly(ethylene glycol) (PEG) was incorporated to enhance the Cip release efficiency. The release efficiency reached 89.3% after introducing 10wt.% PEG, and the mechanical properties of scaffold decreased slightly. Various characterization methods demonstrated that, adding PEG could help to enlarge the microchannel, create extra holes on the channel walls, weaken the interaction between PVA chains and Cip, and miniaturize the crystal size of Cip. All these effects benefit the dissolution and diffusion of Cip from scaffold, increasing its release capability. Moreover, based on biocompatible material composition, PVA/PEG scaffold is a non-cytotoxicity and have been verified that it can promote cell growth. And PVA/PEG scaffolds loaded with Cip can completely inhibit the growth of microorganism because of Cip sustaining release. The PVA scaffold would have a good potential application in tissue engineering, demanding high strength and well drug release capability. PMID:27287128

  4. Molecular mechanism of poly(vinyl alcohol) mediated prevention of aggregation and stabilization of insulin in nanoparticles.

    PubMed

    Rawat, Sanjay; Gupta, Pawan; Kumar, Anil; Garg, Prabha; Suri, C Raman; Sahoo, Debendra K

    2015-04-01

    It is a challenge to formulate polymer based nanoparticles of therapeutic proteins as excipients and process conditions affect stability and structural integrity of the protein. Hence, understanding the protein stability and complex aggregation phenomena is an important area of research in therapeutic protein delivery. Herein we investigated the comparative role of three kinds of surfactant systems (Tween 20:Tween 80), small molecular weight poly(vinyl alcohol) (SMW-PVA), and high molecular weight PVA (HMW-PVA) in prevention of aggregation and stabilization of hexameric insulin in poly(lactide-co-glycolide) (PLGA) based nanoparticle formulation. The nanoparticles were prepared using solid-in-oil-in-water (S/O/W) emulsification method with one of the said surfactant system in inner aqueous phase. The thermal unfolding analysis of released insulin using circular dichroism (CD) indicated thermal stability of the hexameric form. Insulin aggregation monitored by differential scanning calorimetry (DSC) suggested the importance of nuclei formation for aggregation and its prevention by HMW-PVA. Additional guanidinium hydrochloride based equilibrium unfolding and in silico (molecular docking) studies suggested maximum stability of released insulin from formulation containing HMW-PVA (F3). Furthermore, in vivo studies of insulin loaded nanoparticle formulation (F3) in diabetic rats showed its bioactivity. In conclusion, our studies highlight the importance of C-terminal residues of insulin in structural integrity and suggest that the released insulin from formulation containing HMW-PVA in inner aqueous phase was conformationally and thermodynamically stable and bioactive in vivo. PMID:25644480

  5. Adsorption of anionic and cationic dyes by activated carbons, PVA hydrogels, and PVA/AC composite.

    PubMed

    Sandeman, Susan R; Gun'ko, Vladimir M; Bakalinska, Olga M; Howell, Carol A; Zheng, Yishan; Kartel, Mykola T; Phillips, Gary J; Mikhalovsky, Sergey V

    2011-06-15

    The textural and adsorption characteristics of a series of activated carbons (ACs), porous poly(vinyl alcohol) (PVA) gels, and PVA/AC composites were studied using scanning electron microscopy, mercury porosimetry, adsorption of nitrogen (at 77.4 K), cationic methylene blue (MB), anionic methyl orange (MO), and Congo red (CR) from the aqueous solutions. Dye-PVA-AC-water interactions were modeled using the semiempirical quantum chemical method PM6. The percentage of dye removed (C(rem)) by the ACs was close to 100% at an equilibrium concentration (C(eq)) of less than 0.1 mM but decreased with increasing dye concentration. This decrease was stronger at C(eq) of less than 1 mM, and C(rem) was less than 50% at a C(eq) of 10-20 mM. For PVA and the PVA/AC composite containing C-7, the C(rem) values were minimal (<75%). The free energy distribution functions (f(ΔG)) for dye adsorption include one to three peaks in the -ΔG range of 1-60 kJ/mol, depending on the dye concentration range used and the spatial, charge symmetry of the hydrated dye ions and the structural characteristics of the adsorbents. The f(ΔG) shape is most complex for MO with the most asymmetrical geometry and charge distribution and adsorbed at concentrations over a large C(eq) range. For symmetrical CR ions, adsorbed over a narrow C(eq) range, the f(ΔG) plot includes mainly one narrow peak. MB has a minimal molecular size at a planar geometry (especially important for effective adsorption in slit-shaped pores) which explains its greater adsorptive capacity over that of MO or CR. Dye adsorption was greatest for ACs with the largest surface area but as molecular size increases adsorption depends to a greater extent on the pore size distribution in addition to total and nanopore surface areas and pore volume. PMID:21457992

  6. Evaluation of physicochemical and biological properties of chitosan/poly (vinyl alcohol) polymer blend membranes and their correlation for Vero cell growth.

    PubMed

    Sharma, Parul; Mathur, Garima; Dhakate, Sanjay R; Chand, Subhash; Goswami, Navendu; Sharma, Sanjeev K; Mathur, Ashwani

    2016-02-10

    The blend membranes with varying weight ratios of chitosan/poly (vinyl alcohol) (CS/PVA) (1:0, 1:1, 1:2.5, 1.5:1, 1.5: 2.5) were prepared using solvent casting method and were evaluated for their potential application in single-use membrane bioreactors (MBRs). The physicochemical properties of the prepared membranes were investigated for chemical interactions (FTIR), surface morphology (SEM), water uptake, protein sorption (qe), ammonia sorption and growth kinetics of Vero cells. CS/PVA blend membrane having weight ratio of 1.5:1 had shown enhanced membrane flexibility, reduced water uptake, less protein sorption and no ammonium sorption compared to CS membrane. This blend membrane also showed comparatively enhanced higher specific growth rate (0.82/day) of Vero cells. Improved physicochemical properties and growth kinetics obtrude CS/PVA (1.5:1) as a potential surface for adhesion and proliferation with possible application in single use membrane bioreactors. Additionally, new insight explaining correlation between water holding (%) of CS/PVA (1.5:1) blend membrane and doubling time (td) of Vero cells is proposed. PMID:26686166

  7. Alcohol

    MedlinePlus

    ... Text Size: A A A Listen En Español Alcohol Wondering if alcohol is off limits with diabetes? Most people with diabetes can have a moderate amount of alcohol. Research has shown that there can be some ...

  8. Alcohol

    MedlinePlus

    If you are like many Americans, you drink alcohol at least occasionally. For many people, moderate drinking ... risky. Heavy drinking can lead to alcoholism and alcohol abuse, as well as injuries, liver disease, heart ...

  9. Significantly elevated dielectric permittivity of Si-based semiconductor/polymer 2-2 composites induced by high polarity polymers

    NASA Astrophysics Data System (ADS)

    Feng, Yefeng; Gong, Honghong; Xie, Yunchuan; Wei, Xiaoyong; Zhang, Zhicheng

    2016-02-01

    To disclose the essential influence of polymer polarity on dielectric properties of polymer composites filled with semiconductive fillers, a series of Si-based semiconductor/polymer 2-2 composites in a series model was fabricated. The dielectric permittivity of composites is highly dependant on the polarity of polymer layers as well as the electron mobility in Si-based semiconductive sheets. The huge dielectric permittivity achieved in Si-based semiconductive sheets after being coated with high polarity polymer layers is inferred to originate from the strong induction of high polarity polymers. The increased mobility of the electrons in Si-based semiconductive sheets coated by high polarity polymer layers should be responsible for the significantly enhanced dielectric properties of composites. This could be facilely achieved by either increasing the polarity of polymer layers or reducing the percolative electric field of Si-based semiconductive sheets. The most promising 2-2 dielectric composite was found to be made of α-SiC with strong electron mobility and poly(vinyl alcohol) (PVA) with high polarity, and its highest permittivity was obtained as 372 at 100 Hz although the permittivity of α-SiC and PVA is 3-5 and 15, respectively. This work may help in the fabrication of high dielectric constant (high-k) composites by tailoring the induction effect of high polarity polymers to semiconductors.

  10. Experimental and numerical tribological studies of a boundary lubricant functionalized poro-viscoelastic PVA hydrogel in normal contact and sliding.

    PubMed

    Blum, Michelle M; Ovaert, Timothy C

    2012-10-01

    Hydrogels are a cross-linked network of polymers swollen with liquid and have the potential to be used as a synthetic replacement for local defects in load bearing tissues such as articular cartilage. Hydrogels display viscoelastic time dependent behavior, therefore experimental analysis of stresses at the surface and within the gel is difficult to perform. A three-dimensional model of a hydrogel was developed in the commercial finite element software ABAQUS™, implementing a poro-viscoelastic constitutive model along with a contact-dependent flow state and friction conditions. Water content measurements, sliding, and indentation experiments were performed on neat polyvinyl alcohol (PVA), and on low friction boundary lubricant functionalized (BLF-PVA) hydrogels, both manufactured by freeze-thaw processes. Modulus results from the indentation experiments and coefficient of friction values from the sliding experiments were used as material property inputs to the model, while water content was used to calculate initial flow conditions. Tangential force and normal displacement data from a three-dimensional simulation of sliding were compared with the experiments. The tangential force patterns indicated important similarities with the fabricated hydrogels that included an initially high force value due to time dependent deformation followed by a decrease in a stabile value. A similar trend was observed with the normal displacement. These comparisons rendered the model suitable as a representation and were used to analyze the development and propagation of stresses in the immediate surface region. The results showed that in a three-dimensional stress field during sliding, the maximum stress shifted to the surface and rotated closer to the leading edge of contact. This occurred because the stress field becomes dominated by an amplified compressive stress at the leading edge due to the biphasic viscoelastic response of the material during sliding. Also, the complex multi

  11. Mechanically stable antimicrobial chitosan-PVA-silver nanocomposite coatings deposited on titanium implants.

    PubMed

    Mishra, Sandeep K; Ferreira, J M F; Kannan, S

    2015-05-01

    Bionanocomposite coatings with antimicrobial activity comprising polyvinyl alcohol (PVA)-capped silver nanoparticles embedded in chitosan (CS) matrix were developed by a green soft chemistry synthesis route. Colloidal sols of PVA-capped silver nanoparticles (AgNPs) were synthesized by microwave irradiating an aqueous solution comprising silver nitrate and PVA. The bionanocomposites were prepared by adding an aqueous solution of chitosan to the synthesized PVA-capped AgNPs sols in appropriate ratios. Uniform bionanocomposite coatings with different contents of PVA-capped AgNPs were deposited onto titanium substrates by "spread casting" followed by solvent evaporation. Nanoindentation and antimicrobial activity tests performed on CS and bionanocomposites revealed that the incorporation of PVA-capped AgNPs enhanced the overall functional properties of the coatings, namely their mechanical stability and bactericidal activity against Escherichia coli and Staphylococcus aureus. The coated specimens maintained their antimicrobial activity for 8h due to the slow sustained release of silver ions. The overall benefits for the relevant functional properties of the coatings were shown increase with increasing contents of PVA-capped AgNPs in the bionanocomposites. PMID:25659669

  12. Characterization and mechanical performance study of silk/PVA cryogels: towards nucleus pulposus tissue engineering.

    PubMed

    Neo, Puay Yong; Shi, Pujiang; Goh, James Cho-Hong; Toh, Siew Lok

    2014-12-01

    Poly (vinyl) alcohol (PVA) cryogels are reported in the literature for application in nucleus pulposus (NP) replacement strategies. However, these studies are mainly limited to acellular approaches-in part due to the high hydrophilicity of PVA gels that renders cellular adhesion difficult. Silk is a versatile biomaterial with excellent biocompatibility. We hypothesize that the incorporation of silk with PVA will (i) improve the cell-hosting abilities of PVA cryogels and (ii) allow better tailoring of physical properties of the composite cryogels for an NP tissue engineering purpose. 5% (wt/vol) PVA is blended with 5% silk fibroin (wt/vol) to investigate the effect of silk : PVA ratios on the cryogels' physical properties. Results show that the addition of silk results in composite cryogels that are able to swell to more than 10 times its original dry weight and rehydrate to at least 70% of its original wet weight. Adding at least 20% silk significantly improves surface hydrophobicity and is correlated with an improvement in cell-hosting abilities. Cell-seeded cryogels also display an increment in compressive modulus and hoop stress values. In all, adding silk to PVA creates cryogels that can be potentially used as NP replacements. PMID:25329452

  13. The composite hydrogels of polyvinyl alcohol-gellan gum-Ca(2+) with improved network structure and mechanical property.

    PubMed

    Wang, Fei; Wen, Ying; Bai, Tongchun

    2016-12-01

    The composite hydrogels of polyvinyl alcohol (PVA) and gellan gum (GG) are of interesting in the biomaterials application. To improve the structure and mechanical property, in this work, Ca(2+) ion was introduced to crosslink the polymer chain, and the PVA-GG-Ca(2+) hydrogel was formed. By analyzing its structure, mechanical properties, swelling and dehydration kinetics, the effect of molecular interaction on hydrogel structure and properties have been observed. Our result indicates that, as GG is added to hydrogel network, the role of Ca(2+) ion is stand out, it reorganizes the network structure, enhances the mechanical properties, and strengthens the electrolytic and hydrogen bonding interactions in PVA-GG-Ca(2+) hydrogels. These observations will benefit the development of hydrogels in biomaterials application. PMID:27612713

  14. Ultrasound assisted green synthesis of poly(vinyl alcohol) capped silver nanoparticles for the study of its antifilarial efficacy

    NASA Astrophysics Data System (ADS)

    Saha, Swadhin Kr.; Chowdhury, Pranesh; Saini, Prasanta; Babu, Santi P. Sinha

    2014-01-01

    Poly(vinyl alcohol) (PVA) capped stable silver nanoparticles (AgNP) have been synthesized sonochemically with the help of catalytic amount of a biomolecule (tyrosine). An attempt has been made to reduce the harmfull chemical additives (like sodium borohydride, hydrazine, dimethyl formamide, etc.) used in conventional methods. Tyrosine shows excellent reducing activity in presence of PVA stabilizer. Ultra-sound increased the reaction rate and yield, and improved the quality of the AgNP in terms of regular size distribution. The synthetic route follows the principles of green chemistry. Bioactivity has been tested in the light of antifilarial efficacy through induction of apoptosis. The biocompatible polymer (PVA) capped AgNPs are suitable for the treatment of filarial nematode.

  15. Alcohol

    MedlinePlus

    ... Got Homework? Here's Help White House Lunch Recipes Alcohol KidsHealth > For Kids > Alcohol Print A A A Text Size What's in ... What Is Alcoholism? Say No en español El alcohol Getting the Right Message "Hey, who wants a ...

  16. Clay flocculation improved by cationic poly(vinyl alcohol)/anionic polymer dual-component system.

    PubMed

    Sang, Yizhou; Xiao, Huining

    2008-10-15

    The synthesis of cationically modified poly(vinyl alcohol), CPVA, by copolymerization of vinyl acetate and diallyldimethyl ammonium chloride (DADMAC), followed by alkaline hydrolysis was systematically studied. The application of the resulting polymer to the fine clay flocculation was also reported. The charge density and the structure of the resulting CPVA were characterized by polyelectrolyte titration and NMR. A photometric dispersion analyzer was used to conduct the dynamic flocculation experiments. Under fine clay experimental conditions, the CPVA alone contributed little to inducing clay flocculation. However, in conjunction with anionic polyacrylamide-based polymer with high molecular weight and low charge density, significant improvement in the flocculation of fine clay particles was achieved. The influence of factors such as pH and shear force on clay flocculation was also investigated to identify optimum application conditions for clay flocculation. The electrostatic interactions between the clay and CPVA, as well as those between the CPVA pre-treated clay and anionic polymer, were studied to explore the flocculation mechanism. PMID:18657822

  17. Surface modification of ultrafiltration membranes by grafting glycine-functionalized PVA based on polydopamine coatings

    NASA Astrophysics Data System (ADS)

    Li, Fang; Ye, Jianfeng; Yang, Linming; Deng, Chunhua; Tian, Qing; Yang, Bo

    2015-08-01

    Due to the ease of processing and stability during filtration, polydopamine (PD) coatings with grafted hydrophilic polymers have recently received significant attention. In this study, glycine-functionalized PVA was synthesized and grafted to a PD-coated ultrafiltration (UF) membrane to improve its performance during wastewater filtration. The membranes were modified by grafting PD with glycine-functionalized PVA (PD-g-PVA), and the resultant materials were characterized using surface morphology analyses, contact angle measurements, flux, oil/water emulsion separation tests, and grafted layer stability tests. The performance of the PD-g-PVA membrane was compared to that of the membrane modified with PD-g-polyethylene glycol (PEG). After grafting the PD-g-PVA, the surface roughness of the membranes decreased significantly. The grafted PVA layer, which was stable under acidic and alkaline conditions, protected the PD layer. The filtration experiments with an oil/water emulsion indicated that modifying the glycine-functionalized PVA by grafting can significantly improve the antifouling ability of membranes.

  18. Probe diffusion in polymer solutions and hydrogels using fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Michelman-Ribeiro, Ariel; Boukari, Hacene; Horkay, Ferenc; Nossal, Ralph

    2006-03-01

    We apply fluorescence correlation spectroscopy (FCS) to measure the diffusion of small fluorescent probes (TAMRA, Mw = 430 Da; dextran, Mw = 10 kDa) in poly(vinyl alcohol) (PVA) solutions and hydrogels. PVA is a linear, neutral, biocompatible polymer, whose hydrogels have many biotechnology applications, such as drug-delivery devices and tissue scaffolds. The FCS measurements indicate that the probe diffusion decreases when the polymer solution is cross-linked. Further, the more the polymer chains are cross-linked, the slower the particles diffuse. These results suggest that the cross-link density, which is often ignored in the analysis of probe diffusion data in gels, must be taken into account. Remarkably, we find that the apparent diffusion time and the elastic modulus of the gels show a linear correlation.

  19. Characterization of PbS/PVA/GQDs nanocomposite prepared by chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Tohidi, Tavakkol; Jamshidi-Ghaleh, Kazem; Mohammad-Rezaei, Rahim

    2014-10-01

    This work reports synthesis of PbS quantum dots (QDs) embedded in the poly-vinyl alcohol (PVA) in the presence of graphene quantum dots (GQDs) by the low cost and simple method of chemical bath deposition. The as-synthesized products were characterized by X-ray diffraction, transmission electron microscope and optical studies; absorption and photoluminescence measurements. Results showed that in comparison with GQDs and PbS/PVA, photoluminescence intensity of PbS/PVA/GQDs was improved and this could be attributed to rigidity of the local environment, PVA passivation and energy transformation between GQDs and PbS QDs. These analyses determined good distribution of PbS QDs on GQDs planes which is promising for practical applications in nanotechnology.

  20. Fabrication and photocatalytic performance of electrospun PVA/silk/TiO2 nanocomposite textile

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Chan, Shun-Hsiang; Lin, Ting-Han

    2015-02-01

    Many organic/inorganic nanocomposites have been fabricated into fibrous materials using electrospinning techniques, because electrospinning processes have many attractive advantages and the ability to produce relatively large-scale continuous films. In this study, the polyvinyl alcohol (PVA)/silk/titanium dioxide (TiO2) nanocomposite self-cleaning textiles were successfully produced using electrospinning technique. After optimizing electrospinning conditions, we successfully obtained the PVA/silk/TiO2 nanocomposite fibers with average diameter of ˜220 nm and TiO2 concentration can be as high as 18.0 wt.%. For the case of the PVA/silk/TiO2 nanocomposite textile, the color of brilliant green coated on the textile surface changed from the initial green color to colorless after ultraviolet (UV) irradiation. Because of its worthy photocatalytic performance, the developed PVA/silk/TiO2 nanocomposite materials in this study will be beneficial for the design and fabrication of multifunctional fibers and textiles.

  1. Influence of Al doping on optical properties of CdS/PVA nanocomposites: Theory and experiment

    SciTech Connect

    Bala, Vaneeta Tripathi, S. K. Kumar, Ranjan

    2014-04-24

    In the present work theoretical and experimental studies of aluminium doped cadmium sulphide polyvinyl alcohol (Al:CdS/PVA) nanocomposites have been carried out. Tetrahedral cluster AlCd{sub 9}S{sub 2}(SH){sub 18}]{sup 1−} has been encapsulated by small segments of polyvinyl alcohol (PVA) chains in order to simulate experimental environment of nanocomposites. Density functional theory (DFT) using local density approximation (LDA) functionals is employed to study the broadening of band gap upon ligation of nanoclusters. We have used in situ chemical route to synthesize nanocomposites. Optical band gap has been calculated from both experimental and theoretical approach.

  2. Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: a tool for investigating the role of the polymer host.

    PubMed

    Buonerba, Antonio; Noschese, Annarita; Grassi, Alfonso

    2014-04-25

    The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4-polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea = 57.8±11.5 and 62.7±16.7 kJ mol(-1) for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction. PMID:24644103

  3. Cellulose Nanocrystals/ZnO as a Bifunctional Reinforcing Nanocomposite for Poly(vinyl alcohol)/Chitosan Blend Films: Fabrication, Characterization and Properties

    PubMed Central

    Azizi, Susan; Ahmad, Mansor B.; Ibrahim, Nor Azowa; Hussein, Mohd Zobir; Namvar, Farideh

    2014-01-01

    In this study, cellulose nanocrystals/zinc oxide (CNCs/ZnO) nanocomposites were dispersed as bifunctional nano-sized fillers into poly(vinyl alcohol) (PVA) and chitosan (Cs) blend by a solvent casting method to prepare PVA/Cs/CNCs/ZnO bio-nanocomposites films. The morphology, thermal, mechanical and UV-vis absorption properties, as well antimicrobial effects of the bio-nanocomposite films were investigated. It demonstrated that CNCs/ZnO were compatible with PVA/Cs and dispersed homogeneously in the polymer blend matrix. CNCs/ZnO improved tensile strength and modulus of PVA/Cs significantly. Tensile strength and modulus of bio-nanocomposite films increased from 55.0 to 153.2 MPa and from 395 to 932 MPa, respectively with increasing nano-sized filler amount from 0 to 5.0 wt %. The thermal stability of PVA/Cs was also enhanced at 1.0 wt % CNCs/ZnO loading. UV light can be efficiently absorbed by incorporating ZnO nanoparticles into a PVA/Cs matrix, signifying that these bio-nanocomposite films show good UV-shielding effects. Moreover, the biocomposites films showed antibacterial activity toward the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The improved physical properties obtained by incorporating CNCs/ZnO can be useful in variety uses. PMID:24945313

  4. A simple green route to obtain poly(vinyl alcohol) electrospun mats with improved water stability for use as potential carriers of drugs.

    PubMed

    López-Córdoba, Alex; Castro, Guillermo R; Goyanes, Silvia

    2016-12-01

    Poly(vinyl alcohol) (PVA) is a hydrophilic, biocompatible and nontoxic polymer. However, because of its low water-resistance, some applications for PVA-based materials are limited (e.g., drug delivery systems and wound dressings). In the current work, PVA mats containing tetracycline hydrochloride (TC) were successfully developed by electrospinning. In order to improve the water stability of the systems, the cross-linking of the PVA matrix was induced by citric acid (CA) addition together with heating treatments (150°C or 190°C for 3min). TC presence led to a strong increase in the electrical conductivity of the blends and as a result, fibers with about 44% lower diameter (270nm) than that of the corresponding unloaded mats (485nm) were obtained. Laser scanning confocal microscopy images indicated that TC was well distributed along the PVA nanofibers. The mats were evaluated by FTIR, which revealed chemical interactions between PVA hydroxyl groups and CA carboxylic ones. The treatment at 150°C for 3min proved to be the more suitable for the preparation of TC-containing mats with improved water resistance, maintaining the TC antimicrobial activity against both Escherichia coli and Staphylococcus aureus almost unaltered. These mats showed a burst release of TC, giving around 95% of the drug within the first hour of immersion in water. PMID:27612766

  5. Determination of glass transition temperature of reduced graphene oxide-poly(vinyl alcohol) composites using temperature dependent Fourier transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Mahendia, Suman; Heena; Kandhol, Geeta; Deshpande, Uday P.; Kumar, Shyam

    2016-05-01

    In the present work, structural properties of reduced graphene oxide (RGO) synthesized using modified Hummer's method and its composites with Poly(vinyl alcohol) (PVA) fabricated using solution-cast method have been studied. The structural properties of prepared samples have been systematically studied through UV-Visible absorption, Raman, Fourier Transform Infrared (FTIR) and Differential Scanning Calorimeter (DSC) spectroscopy. Infrared spectroscopy indicates the grafting of PVA chains with graphene layer through the formation of H-bonding linkage in the composites. Temperature-dependent FTIR spectra of PVA-RGO composite films were recorded to obtain the glass transition temperature (Tg) and to study its molecular origin. From these spectra the values of Tg were obtained using two-dimensional (2D) mapping of the first derivative of the absorbance intensity with respect to temperature (dA/dT), over the space of wavenumber and temperature. The value of Tg obtained for pure PVA increases from 78 °C to 92 °C after loading 0.5 wt.% of RGO in PVA and can be attributed to the strong H-bonding interaction between polymer chains and grafted solid surface of RGO. These results are in good agreement with those obtained from DSC analysis. This clearly indicates that the thermal behavior of PVA gets modified with loading of RGO.

  6. 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.

  7. Removal of PCB-DNAPL from a rough-walled fracture using alcohol/polymer flooding

    NASA Astrophysics Data System (ADS)

    Gauthier, M.; Kueper, B. H.

    2006-03-01

    Phase behaviour experiments employing PCB (Aroclor 1242)/alcohol/water systems were conducted with ethanol (EtOH) and n-propanol (nPA). Both exhibited an affinity for the aqueous phase within the entire two-phase region. As much as 88% by volume (88% vol.) EtOH and 80% vol. nPA were necessary to achieve full miscibility of the PCB in the aqueous phase. DNAPL-water interfacial tension (IFT) was reduced from 38.9 dyn/cm to 4.7 dyn/cm and 2.4 dyn/cm with 80% vol. EtOH and 76% vol. nPA. The addition of alcohol brought about 41% and 54% reductions in DNAPL viscosity at maximal concentrations of EtOH and nPA. Density of the PCB-DNAPL was relatively unaffected by the presence of alcohol. A series of seven experiments were conducted where successive slugs of nPA and xanthan gum polymer solutions were injected into a fractured shale sample. A 30% vol. nPA solution injected under a hydraulic gradient of 0.36 allowed enhanced PCB removal primarily through reduction of IFT and resulted in 72% DNAPL recovery. Several pore volumes of alcohol solution were necessary to displace all the potentially mobile non-wetting phase since the high-viscosity DNAPL was mobilized at a lower flow rate than the overall fluid velocity, illustrating non-piston displacement. The injection of a 95% vol. nPA alcohol solution, theoretically at a sufficient concentration to produce fully miscible displacement of the residual DNAPL at equilibrium, resulted in non-equilibrium partitioning of the PCB into the flushing solution, likely due to the high fluid velocities in the fracture. The injection of 200 pore volumes of 95% vol. nPA solution resulted in 94% DNAPL recovery. Alcohol floods operated below the miscibility envelope appear to be a valuable source zone remedial alternative where the objective is to reduce DNAPL mobility to zero, but it should be noted that DNAPL mobility is increased during the application of the technology and steps may need to be taken to prevent unwanted vertical mobilization.

  8. Removal of PCB-DNAPL from a rough-walled fracture using alcohol/polymer flooding.

    PubMed

    Gauthier, M; Kueper, B H

    2006-03-01

    Phase behaviour experiments employing PCB (Aroclor 1242)/alcohol/water systems were conducted with ethanol (EtOH) and n-propanol (nPA). Both exhibited an affinity for the aqueous phase within the entire two-phase region. As much as 88% by volume (88% vol.) EtOH and 80% vol. nPA were necessary to achieve full miscibility of the PCB in the aqueous phase. DNAPL-water interfacial tension (IFT) was reduced from 38.9 dyn/cm to 4.7 dyn/cm and 2.4 dyn/cm with 80% vol. EtOH and 76% vol. nPA. The addition of alcohol brought about 41% and 54% reductions in DNAPL viscosity at maximal concentrations of EtOH and nPA. Density of the PCB-DNAPL was relatively unaffected by the presence of alcohol. A series of seven experiments were conducted where successive slugs of nPA and xanthan gum polymer solutions were injected into a fractured shale sample. A 30% vol. nPA solution injected under a hydraulic gradient of 0.36 allowed enhanced PCB removal primarily through reduction of IFT and resulted in 72% DNAPL recovery. Several pore volumes of alcohol solution were necessary to displace all the potentially mobile non-wetting phase since the high-viscosity DNAPL was mobilized at a lower flow rate than the overall fluid velocity, illustrating non-piston displacement. The injection of a 95% vol. nPA alcohol solution, theoretically at a sufficient concentration to produce fully miscible displacement of the residual DNAPL at equilibrium, resulted in non-equilibrium partitioning of the PCB into the flushing solution, likely due to the high fluid velocities in the fracture. The injection of 200 pore volumes of 95% vol. nPA solution resulted in 94% DNAPL recovery. Alcohol floods operated below the miscibility envelope appear to be a valuable source zone remedial alternative where the objective is to reduce DNAPL mobility to zero, but it should be noted that DNAPL mobility is increased during the application of the technology and steps may need to be taken to prevent unwanted vertical mobilization

  9. PVA/CM-chitosan/honey hydrogels prepared by using the combined technique of irradiation followed by freeze-thawing

    NASA Astrophysics Data System (ADS)

    Afshari, M. J.; Sheikh, N.; Afarideh, H.

    2015-08-01

    Hydrogels with three components, poly(vinyl alcohol) (PVA), carboxymethylate chitosan (CM-chitosan) and honey have been prepared by using radiation method and radiation followed by freeze-thawing cycles technique (combinational method). The solid concentration of the polymer solution is 15 wt% and the ratios of PVA/CM-chitosan/honey are 10/1.5/3.5, 10/2/3, 10/3/2, and 10/3.5/1.5. The applied irradiation doses are 25, 30 and 40 kGy. Various tests have been done to evaluate the hydrogel properties to produce materials to be used as wound dressing. The results show that combinational method improves the mechanical strength of hydrogels while it has no significant effect on the water evaporation rate of gels. The combinational method decreases the swelling of hydrogels significantly, albeit this parameter is still acceptable for wound dressing. Microbiological analyses show that the hydrogel prepared by both methods can protect the wound from Escherichia coli bacterial infection. The wound healing test shows the good performance of the gels in mice.

  10. Aqueous-Processed Insulating Polymer/Nanocrystal Hybrid Solar Cells.

    PubMed

    Jin, Gan; Chen, Zhaolai; Dong, Chunwei; Cheng, Zhongkai; Du, Xiaohang; Zeng, Qingsen; Liu, Fangyuan; Sun, Haizhu; Zhang, Hao; Yang, Bai

    2016-03-23

    A novel kind of hybrid solar cell (HSC) was developed by introducing water-soluble insulating polymer poly(vinyl alcohol) (PVA) into nanocrystals (NCs), which revealed that the most frequently used conjugated polymer could be replaced by an insulating one. It was realized by strategically taking advantage of the characteristic of decomposition for the polymer at annealing temperature, and it was interesting to discover that partial decomposition of PVA left behind plenty of pits on the surfaces of CdTe NC films, enlarging surface contact area between CdTe NCs and subsequently evaporated MoO3. Moreover, the residual annealed PVA filled in the voids among spherical CdTe NCs, which led to the decrease of leakage current. An improved shunt resistance (increased by ∼80%) was achieved, indicating the charge-carrier recombination was effectively overcome. As a result, the new HSCs were endowed with increased Voc, fill factor, and power conversion efficiency compared with the pure NC device. This approach can be applied to other insulating polymers (e.g., PVP) with advantages in synthesis, type, economy, stability, and so on, providing a novel universal cost-effective way to achieve higher photovoltaic performance. PMID:26931540

  11. Whole-Pattern Fitting and Positron Annihilation Studies of Magnetic PVA/α-Fe2O3 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Prashanth, K. S.; Mahesh, S. S.; Prakash, M. B. Nanda; Ningaraju, S.; Ravikumar, H. B.; Somashekar, R.; Nagabhushana, B. M.

    2016-03-01

    A low-temperature solution combustion method was used to synthesize α-Fe2O3 nanoparticles. Magnetic polyvinyl alcohol (PVA)/α-Fe2O3/NaCl nanocomposites were prepared by solvent cast method. The Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) results are in confirmation with X-ray diffraction (XRD) results indicating the formation of nanocomposites. The microcrystalline parameters, crystallite size (), lattice strain (g in %), stacking faults (α d ), and twin faults (β) of prepared polymer nanocomposites were evaluated by whole-pattern fitting technique. The refinement was carried out using the computed microstructural parameters in which the twin faults and stacking faults did not vary much and statistical deviation was less than 5 %. Positron annihilation lifetime spectroscopy (PALS) was used for microstructural characterization. PALS results show that the ortho-positronium (o-Ps) lifetime (τ3) increases gradually as a function of nanoparticle concentration and about 219 ps increase observed from1.50 to1.71 ns at 3 wt%. This indicates the increase of free volume hole size (V f ) from 54.47 to 72.18 Å3. The o-Ps intensities (I 3) decrease indicating the inhibition of o-Ps formation upon incorporation of nanoparticles into PVA. The increase in I 2 values suggests the increased annihilation at the interface region. Positron lifetime parameters, viz., o-Ps lifetime, and its intensities indicate the effect of quenching and inhibition upon incorporation of metal oxide nanoparticles and inorganic salt into PVA.

  12. Whole-Pattern Fitting and Positron Annihilation Studies of Magnetic PVA/α-Fe2O3 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Prashanth, K. S.; Mahesh, S. S.; Prakash, M. B. Nanda; Ningaraju, S.; Ravikumar, H. B.; Somashekar, R.; Nagabhushana, B. M.

    2016-06-01

    A low-temperature solution combustion method was used to synthesize α-Fe2O3 nanoparticles. Magnetic polyvinyl alcohol (PVA)/α-Fe2O3/NaCl nanocomposites were prepared by solvent cast method. The Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) results are in confirmation with X-ray diffraction (XRD) results indicating the formation of nanocomposites. The microcrystalline parameters, crystallite size ( ), lattice strain ( g in %), stacking faults ( α d ), and twin faults ( β) of prepared polymer nanocomposites were evaluated by whole-pattern fitting technique. The refinement was carried out using the computed microstructural parameters in which the twin faults and stacking faults did not vary much and statistical deviation was less than 5 %. Positron annihilation lifetime spectroscopy (PALS) was used for microstructural characterization. PALS results show that the ortho-positronium (o-Ps) lifetime (τ3) increases gradually as a function of nanoparticle concentration and about 219 ps increase observed from1.50 to1.71 ns at 3 wt%. This indicates the increase of free volume hole size ( V f ) from 54.47 to 72.18 Å3. The o-Ps intensities ( I 3) decrease indicating the inhibition of o-Ps formation upon incorporation of nanoparticles into PVA. The increase in I 2 values suggests the increased annihilation at the interface region. Positron lifetime parameters, viz., o-Ps lifetime, and its intensities indicate the effect of quenching and inhibition upon incorporation of metal oxide nanoparticles and inorganic salt into PVA.

  13. Effect of cross linking of PVA/starch and reinforcement of modified barley husk on the properties of composite films.

    PubMed

    Mittal, Aanchal; Garg, Sangeeta; Kohli, Deepak; Maiti, Mithu; Jana, Asim Kumar; Bajpai, Shailendra

    2016-10-20

    Barley husk (BH) was graft copolymerized by palmitic acid. The crystalline behavior of BH decreased after grafting. Poly vinyl alcohol (PVA)/starch (St) blend film, urea formaldehyde cross linked PVA/St films and composite films containing natural BH, grafted BH were prepared separately. The effect of urea/starch ratio, content of BH and grafted BH on the mechanical properties, water uptake (%), and biodegradability of the composite films was observed. With increase in urea: starch ratio from 0 to 0.5 in the blend, tensile strength of cross linked film increased by 40.23% compared to the PVA/St film. However, in grafted BH composite film, the tensile strength increased by 72.4% than PVA/St film. The degradation rate of natural BH composite film was faster than PVA/St film. Various films were characterized by SEM, FT-IR and thermal analysis. PMID:27474641

  14. 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. PMID:26428121

  15. Alcohol

    MedlinePlus

    ... as well as injuries, liver disease, heart disease, cancer, and other health problems. It can also cause problems at home, at work, and with friends. NIH: National Institute on Alcohol Abuse and Alcoholism

  16. Structural and biological evaluation of a multifunctional SWCNT-AgNPs-DNA/PVA bio-nanofilm.

    PubMed

    Subbiah, Ramesh P; Lee, Haisung; Veerapandian, Murugan; Sadhasivam, Sathya; Seo, Soo-Won; Yun, Kyusik

    2011-04-01

    A bio-nanofilm consisting of a tetrad nanomaterial (nanotubes, nanoparticles, DNA, polymer) was fabricated utilizing in situ reduction and noncovalent interactions and it displayed effective antibacterial activity and biocompatibility. This bio-nanofilm was composed of homogenous silver nanoparticles (AgNPs) coated on single-walled carbon nanotubes (SWCNTs), which were later hybridized with DNA and stabilized in poly(vinyl alcohol) (PVA) in the presence of a surfactant with the aid of ultrasonication. Electron microscopy and bio-AFM (atomic force microscopy) images were used to assess the morphology of the nanocomposite (NC) structure. Functionalization and fabrication were examined using FT-Raman spectroscopy by analyzing the functional changes in the bio-nanofilm before and after fabrication. UV-visible spectroscopy and X-ray powder diffraction (XRD) confirmed that AgNPs were present in the final NC on the basis of its surface plasmon resonance (370 nm) and crystal planes. Thermal gravimetric analysis was used to measure the percentage weight loss of SWCNT (17.5%) and final SWCNT-AgNPs-DNA/PVA (47.7%). The antimicrobial efficiency of the bio-nanofilm was evaluated against major pathogenic organisms. Bactericidal ratios, zone of inhibition, and minimum inhibitory concentration were examined against gram positive and gram negative bacteria. A preliminary cytotoxicity analysis was conducted using A549 lung cancer cells and IMR-90 fibroblast cells. Confocal laser microscopy, bio-AFM, and field emission scanning electron microscopy (FE-SEM) images demonstrated that the NCs were successfully taken up by the cells. These combined results indicate that this bio-nanofilm was biocompatible and displayed antimicrobial activity. Thus, this novel bio-nanofilm holds great promise for use as a multifunctional tool in burn therapy, tissue engineering, and other biomedical applications. PMID:21336791

  17. Alcoholism.

    ERIC Educational Resources Information Center

    Caliguri, Joseph P., Ed.

    This extensive annotated bibliography provides a compilation of documents retreived from a computerized search of the ERIC, Social Science Citation Index, and Med-Line databases on the topic of alcoholism. The materials address the following areas of concern: (1) attitudes toward alcohol users and abusers; (2) characteristics of alcoholics and…

  18. 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.

  19. Evaluation of the Antimicrobial Effect of Chitosan/Polyvinyl Alcohol Electrospun Nanofibers Containing Mafenide Acetate

    PubMed Central

    Abbaspour, Mohammadreza; Sharif Makhmalzadeh, Behzad; Rezaee, Behjat; Shoja, Saeed; Ahangari, Zohreh

    2015-01-01

    Background: Chitosan, an important biodegradable and biocompatible polymer, has demonstrated wound-healing and antimicrobial properties. Objectives: This study aimed to evaluate the antimicrobial properties of mafenide acetate-loaded nanofibrous films, prepared by the electrospinning technique, using chitosan and polyvinyl alcohol (PVA). Materials and Methods: A 32 full factorial design was used for formulating electrospinning solutions. The chitosan percentage in chitosan/PVA solutions (0%, 10%, and 30%) and the drug content (0%, 20%, and 40%) were chosen as independent variables. The release rate of mafenide acetate from nanofibrous films and their microbial penetration were evaluated. The antimicrobial activity of different nanofibrous film formulations against Staphylococcus aureus and Pseudomonas aeruginosa was studied. Results: The results indicated that all nanofibrous films, with and without drug, can prevent bacterial penetration. Incorporation of mafenide acetate into chitosan/PVA nanofibers enhanced their antimicrobial activity against P. aeruginosa and S. aureus. Conclusions: Overall, the results showed that chitosan/polyvinyl alcohol (PVA) nanofibrous films are applicable for use as a wound dressing with protective, healing, and antimicrobial effects. PMID:26587214

  20. Effects of compatibility of polymer binders with solvate ionic liquid electrolytes on discharge and charge reactions of lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Nakazawa, Toshitada; Ikoma, Ai; Kido, Ryosuke; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi

    2016-03-01

    Electrochemical reactions in Li-S cells with a solvate ionic liquid (SIL) electrolyte composed of tetraglyme (G4) and Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl)amide) are studied. The sulfur cathode (S cathode) comprises sulfur, carbon powder, and a polymer binder. Poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA-x) with different degrees of saponification (x%) are used as binders to prepare the composite cathodes. For the Li-S cell containing PEO binder, lithium polysulfides (Li2Sm, 2 ≤ m ≤ 8), reaction intermediates of the S cathode, dissolve into the electrolyte, and Li2Sm acts as a redox shuttle in the Li-S cell. In contrast, in the Li-S cell with PVA-x binder, the dissolution of Li2Sm is suppressed, leading to high columbic efficiencies during charge-discharge cycles. The compatibility of the PVA-x binder with the SIL electrolyte changes depending on the degree of saponification. Decreasing the degree of saponification leads to increased electrolyte uptake by the PVA-x binder, increasing the charge and discharge capacities of Li-S cell. The rate capability of Li-S cell is also enhanced by the partial swelling of the PVA-x binder. The enhanced performance of Li-S cell containing PVA-x is attributed to the lowering of resistance of Li+ ion transport in the composite cathode.

  1. Effect of beam expansion loss in a carbon nanotube-doped PVA film on passively mode-locked erbium-doped fiber lasers with different feedback ratios

    NASA Astrophysics Data System (ADS)

    Cheng, Kuang-Nan; Chi, Yu-Chieh; Cheng, Chih-Hsien; Lin, Yung-Hsiang; Lo, Jui-Yung; Lin, Gong-Ru

    2014-10-01

    The effect of beam expansion induced divergent loss in a single-wall carbon nanotube (SWCNT) doped polyvinyl alcohol (PVA) based ultrafast saturable absorber (SA) film thickness on the passive mode-locking (PML) performances of erbium-doped fiber lasers are demonstrated. The variation on the PML pulsewidth of the EDFL is discussed by changing the SWCNT-PVA SA film thicknesses, together with adjusting the pumping power and the intra-cavity feedback ratio. An almost 6 dB increment of divergent loss when enlarging the SWCNT-PVA based SA film thickness from 30-130 µm is observed. When shrinking the SA thickness to 30 µm at the largest pumping power of 52.5 mW, the optical spectrum red-shifts to 1558.8 nm with its 3 dB spectral linewidth broadening up to 2.7 nm, while the pulse has already entered the soliton regime with multi-order Kelly sidebands aside the spectral shoulder. The soliton pulsewidth is as short as 790 fs, which is much shorter than those obtained with other thicker SWCNT doped PVA polymer film based SAs; therefore, the peak power from the output of the PML-EDFL is significantly enlarged accompanied by a completely suppressed residual continuous-wave level to achieve the largest on/off extinction ratio. The main mechanism of pulse shortening with reducing thickness of SWCNT doped PVA polymer film based SA is attributed to the limited beam expansion as well as the enlarged modulation depth, which results in shortened soliton pulsewidth with a clean dc background, and broadened spectrum with enriched Kelly sidebands. The increase of total SWCNT amount in the thicker SA inevitably causes a higher linear absorption; hence, the mode-locking threshold also rises accordingly. By enlarging pumping power from 38.5-52.5 mW, the highest ascent on pulse extinction of up to 32 dB is observed among all kinds of feedback conditions. Nevertheless, the enlargement on the extinction slightly decays with increasing the feedback ratio from 30-90%, as

  2. Alcohol-soluble Star-shaped Oligofluorenes as Interlayer for High Performance Polymer Solar Cells

    PubMed Central

    Zou, Yang; He, Zhicai; Zhao, Baofeng; Liu, Yuan; Yang, Chuluo; Wu, Hongbin; Cao, Yong

    2015-01-01

    Two star-shaped oligofluorenes with hexakis(fluoren-2-yl)benzene as core are designed and sythesized for interfacial materials in polymer solar cell. Diethanolamino groups are attached to the side chain of fluorene units for T0-OH and T1-OH to enable the alcohol solubility, and additional hydrophobic n-hexyl chains are also grafted on the increased fluorene arms for T1-OH. In conventional device with PCDTBT/PC71BM as active layer, a 50% enhanced PCE is obtained by incorporating T0-OH and T1-OH as the interlayer compared with device without interlayer. By optimizing the active material with PTB7 and with the inverted device structure, a maximum PCE of 9.30% is achieved, which is among the highest efficiencies for PTB7 based polymer solar cells. The work function of modified electrode, the surface morphology and the suraface properties are systematically studied. By modifying the structures of the star-shaped molecules, a balance between the hydrophobic and hydrophilic property is finely tuned, and thus facilitate the interlayer for high performance of PSCs. PMID:26612688

  3. The states of water within poly(vinyl alcohol) thin films part 2: Investigation by differential scanning calorimetry and thermogravimetric analysis

    SciTech Connect

    Hodge, R.M.; Edward, G.H.; Simon, G.P.

    1993-12-31

    In order to utilize thermoplastic processing techniques with poly(vinyl alcohol) (PVA), the polymer must be plasticized with water. Water exists in different states within the PVA network and behaves in a manner specific to each state. This work uses Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis to investigate the nature of water within PVA thin films. A model is proposed whereby the ingression of each state of water to exist in 3 distinct states: (1) free of bulk water, (2) freezable bound (loosely bound) water, and (3) nonfreezable bound (strongly bound) water. Generally speaking, the data suggest that the various states of water are filled sequentially. The model is consistent with the results of Positron Annihilation Lifetime Spectroscopy (PALS), also to be presented at this conference.

  4. Separability of SO[sub 2] from SO[sub 2]/N[sub 2] mixture through sulfoxide-modified poly(vinyl alcohol) and cellulose membranes

    SciTech Connect

    Imai, Kiyokazu; Shiomi, Tomoo; Tezuka, Yasuyuki; Itamochi, Hiroko; Miya, Masamitsu )

    1993-06-05

    Separability of SO[sub 2] from mixtures of SO[sub 2] and N[sub 2] gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t-butyl, and phenyl vinyl sulfoxides. Of these sulfoxide-modified polymers, the phenyl vinyl sulfoxide-modified PVA membranes were found to give the best separation of SO[sub 2]. In the phenyl vinyl sulfoxide-modified PVA membranes, the permeability coefficient of SO[sub 2] increased with sulfoxide content while separability of SO[sub 2] was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO[sub 2] was about 170 at this sulfoxide content.

  5. n-Type Water/Alcohol-Soluble Naphthalene Diimide-Based Conjugated Polymers for High-Performance Polymer Solar Cells.

    PubMed

    Wu, Zhihong; Sun, Chen; Dong, Sheng; Jiang, Xiao-Fang; Wu, Siping; Wu, Hongbin; Yip, Hin-Lap; Huang, Fei; Cao, Yong

    2016-02-17

    With the demonstration of small-area, single-junction polymer solar cells (PSCs) with power conversion efficiencies (PCEs) over the 10% performance milestone, the manufacturing of high-performance large-area PSC modules is becoming the most critical issue for commercial applications. However, materials and processes that are optimized for fabricating small-area devices may not be applicable for the production of high-performance large-area PSC modules. One of the challenges is to develop new conductive interfacial materials that can be easily processed with a wide range of thicknesses without significantly affecting the performance of the PSCs. Toward this goal, we report two novel naphthalene diimide-based, self-doped, n-type water/alcohol-soluble conjugated polymers (WSCPs) that can be processed with a broad thickness range of 5 to 100 nm as efficient electron transporting layers (ETLs) for high-performance PSCs. Space charge limited current and electron spin resonance spectroscopy studies confirm that the presence of amine or ammonium bromide groups on the side chains of the WSCP can n-dope PC71BM at the bulk heterojunction (BHJ)/ETL interface, which improves the electron extraction properties at the cathode. In addition, both amino functional groups can induce self-doping to the WSCPs, although by different doping mechanisms, which leads to highly conductive ETLs with reduced ohmic loss for electron transport and extraction. Ultimately, PSCs based on the self-doped WSCP ETLs exhibit significantly improved device performance, yielding PCEs as high as 9.7% and 10.11% for PTB7-Th/PC71BM and PffBT4T-2OD/PC71BM systems, respectively. More importantly, with PffBT4T-2OD/PC71BM BHJ as an active layer, a prominent PCE of over 8% was achieved even when a thick ETL of 100 nm was used. To the best of our knowledge, this is the highest efficiency demonstrated for PSCs with a thick interlayer and light-harvesting layer, which are important criteria for eventually making

  6. A reduction of diffusion in PVA Fricke hydrogels

    NASA Astrophysics Data System (ADS)

    Smith, S. T.; Masters, K. S.; Hosokawa, K.; Blinco, J.; Crowe, S. B.; Kairn, T.; Trapp, J. V.

    2015-01-01

    A modification to the PVA-FX hydrogel whereby the chelating agent, xylenol orange, was partially bonded to the gelling agent, poly-vinyl alcohol, resulted in an 8% reduction in the post irradiation Fe3+ diffusion, adding approximately 1 hour to the useful timespan between irradiation and readout. This xylenol orange functionalised poly-vinyl alcohol hydrogel had an OD dose sensitivity of 0.014 Gy-1 and a diffusion rate of 0.133 mm2 h-1. As this partial bond yields only incremental improvement, it is proposed that more efficient methods of bonding xylenol orange to poly-vinyl alcohol be investigated to further reduce the diffusion in Fricke gels.

  7. Effects of PVA-coated nanoparticles on human T helper cell activity.

    PubMed

    Strehl, Cindy; Schellmann, Saskia; Maurizi, Lionel; Hofmann-Amtenbrink, Margarethe; Häupl, Thomas; Hofmann, Heinrich; Buttgereit, Frank; Gaber, Timo

    2016-03-14

    Superparamagnetic iron oxide nanoparticles (SPION) are used as high-sensitive enhancer for magnetic resonance imaging, where they represent a promising tool for early diagnosis of destructive diseases such as rheumatoid arthritis (RA). Since we could demonstrate that professional phagocytes are activated by amino-polyvinyl-alcohol-coated-SPION (a-PVA-SPION), the study here focuses on the influence of a-PVA-SPION on human T cells activity. Therefore, primary human CD4+ T cells from RA patients and healthy subjects were treated with varying doses of a-PVA-SPION for 20h or 72h. T cells were then analyzed for apoptosis, cellular energy, expression of the activation marker CD25 and cell proliferation. Although, we observed that T cells from RA patients are more susceptible to low-dose a-PVA-SPION-induced apoptosis than T cells from healthy subjects, in both groups a-PVA-SPION do not activate CD4+ T cells per se and do not influence mitogen-mediated T cells activation with regard to CD25 expression and cell proliferation. Nevertheless, our results demonstrate that CD4+ T cells from RA patients and healthy subjects differ in their response to mitogen stimulation and oxygen availability. We conclude from our data, that a-PVA-SPION do neither activate nor significantly influence mitogen-stimulated CD4+ T cells activation and have negligible influence on T cells apoptosis. PMID:26774940

  8. Pervaporation separation of binary organic-aqueous liquid mixtures using crosslinked PVA membranes. I. Characterization of the reaction between PVA and PAA

    SciTech Connect

    Jiwon Rhim; Kewho Lee . Membranes and Separation Lab.); Minyoung Sohn; Hyeokjong Joo . Dept. of Polymer Science and Engineering)

    1993-10-20

    For the purpose of the water-selective membrane material development for pervaporation separation, poly(vinyl alcohol) (PVA) was crosslinked with a low molecular weight of poly(acrylic acid) (PAA). The crosslinking reactions between PVA and PAA were characterized through IR spectroscopy, differential scanning calorimetry (DSC), and tensile tests when varying the reaction conditions, that is, time, temperature, amounts of cross-linking agents, PAA. It was found that the crosslinking reaction was fast: in other words, that the reaction mainly occurred at the initial step of each reaction condition. The best reaction conditions for preparing the crosslinked PVA membranes were found to be: reaction time not over 1 h, reaction temperature in the range of 150-180 C. PAA contents of 15-20 wt% were found satisfactory with respect to the application areas.

  9. Effects of the molecular level dispersion of graphene oxide on the free volume characteristics of poly(vinyl alcohol) and its impact on the thermal and mechanical properties of their nanocomposites.

    PubMed

    Sharma, S K; Prakash, J; Pujari, P K

    2015-11-21

    Poly(vinyl alcohol), PVA, reinforced with carbon nanofillers has shown drastic variations in thermal as well as mechanical properties. In order to establish structure-property correlations, these variations have been correlated with modifications in the hydrogen bonding structure as well as the crystallinity of the PVA matrix without paying much attention to molecular packing in the amorphous region of this semicrystalline polymer. In order to investigate the molecular packing in PVA-graphene oxide (GO) nanocomposites, free volume characterization of PVA-GO nanocomposites has been carried out using ortho-positronium (o-Ps) probe. The variations in free volume size, density and size distribution have been determined through o-Ps lifetime and the corresponding intensity as well as its lifetime distribution. The variation in hydrogen bonding and its effect on crystallinity has been determined by Fourier Transform Infra Red (FTIR) and X-ray diffraction (XRD) measurements. The variation in the thermal (glass transition temperature) and mechanical (Young's modulus, tensile strength and percentage strain at break) properties of the nanocomposites is explained in view of the free volume structure and crystallinity of the PVA matrix which are severely modified due to the molecular-level dispersion of GO sheets in the PVA matrix. PMID:26465337

  10. Synergistic effect of ozonation and ionizing radiation for PVA decomposition.

    PubMed

    Sun, Weihua; Chen, Lujun; Zhang, Yongming; Wang, Jianlong

    2015-08-01

    Ozonation and ionizing radiation are both advanced oxidation processes (AOPs) without chemical addition and secondary pollution. Also, the two processes' efficiency is determined by different pH conditions, which creates more possibilities for their combination. Importantly, the combined process of ozonation and ionizing radiation could be suitable for treating wastewaters with extreme pH values, i.e., textile wastewater. To find synergistic effects, the combined process of ozonation and ionizing radiation mineralization was investigated for degradation of polyvinyl alcohol (PVA) at different pH levels. A synergistic effect was found at initial pH in the range 3.0-9.4. When the initial pH was 3.0, the combined process of ozonation and ionizing radiation gave a PVA mineralization degree of 17%. This was 2.7 times the sum achieved by the two individual processes, and factors of 2.1 and 1.7 were achieved at initial pH of 7.0 and 9.4, respectively. The combined process of ozonation and ionizing radiation was demonstrated to be a feasible strategy for treatment of PVA-containing wastewater. PMID:26257347

  11. Mechanical evaluation of poly(vinyl alcohol)-based fibrous composites as biomaterials for meniscal tissue replacement.

    PubMed

    Holloway, Julianne L; Lowman, Anthony M; Palmese, Giuseppe R

    2010-12-01

    In this study, poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) and PP fibers and evaluated as potential nondegradable meniscal replacements. An investigation of hydrogel and composite mechanical properties indicates that fiber-reinforced PVA hydrogels could replicate the unique anisotropic modulus distribution present in the native meniscus; the most commonly damaged orthopedic tissue. More specifically, fibrous reinforcement successfully increased the tensile modulus of the biomaterial from 0.23±0.02MPa without any reinforcement to 258.1±40.1MPa at 29vol.% UHMWPE. Additionally, the molecular weight between cross-links, bound water and the microstructure of the PVA hydrogels were evaluated as a function of freeze-thaw cycles and polymer concentration to lend insight into the processes occurring during synthesis. These results suggest the presence of multiple mechanisms as causes for increasing hydrogel modulus with freeze-thaw cycling, including hydrogen bonding between amorphous and/or crystalline regions, and the formation of highly concentrated regions of mostly amorphous PVA chains. It is possible that the formation of regions with highly concentrated amounts of PVA increases the load-bearing ability of the hydrogels. PMID:20601243

  12. 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.

    2016-07-01

    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.

  13. Livestock Air Treatment Using PVA-Coated Powdered Activated Carbon Biofilter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ideal biofilter media provide surface for attachment of microorganisms responsible for removing air-born contaminants while facilitating passage of air. This study evaluated the efficacy of polyvinyl alcohol (PVA)-coated powdered activated carbon particles as a biofiltration medium. This material e...

  14. Adsorption of ammonium and phosphate by feather protein based semi-interpenetrating polymer networks hydrogel as a controlled-release fertilizer.

    PubMed

    Su, Yuan; Liu, Jia; Yue, Qinyan; Li, Qian; Gao, Baoyu

    2014-01-01

    A new feather protein-grafted poly(potassium acrylate)/polyvinyl alcohol (FP-g-PKA/PVA) semi-interpenetrating polymer networks (semi-IPNs) hydrogel was produced through graft copolymerization with FP as a basic macromolecular skeletal material, acrylic acid as a monomer and PVA as a semi-IPNs polymer. The adsorption of ammonium and phosphate ions from aqueous solution using the new hydrogel as N and P controlled-release fertilizer with water-retention capacity was studied. The effects of pH value, concentration, contact time and ion strength on NH4+ and PO3-4 removal by FP-g-PKA/PVA semi-IPNs hydrogel were investigated using batch adsorption experiments. The results indicated that the hydrogel had high adsorption capacities and fast adsorption rates for NH4+ and PO3-4 in wide pH levels ranging from 4.0 to 9.0. Kinetic analysis presented that both NH4+ and PO3-4 removal were closely fitted with the pseudo-second-order model. Furthermore, the adsorption isotherms of hydrogel were best represented by the Freundlich model. The adsorption-desorption experimental results showed the sustainable stability of FP-g-PKA/PVA semi-IPNs hydrogel for NH4+ and PO3-4 removal. Overall, FP-g-PKA/PVA could be considered as an efficient material for the removal and recovery of nitrogen and phosphorus with the agronomic reuse as a fertilizer. PMID:24600885

  15. [Research on the treatment of wastewater containing PVA by ozonation-activated sludge process].

    PubMed

    Xing, Xiao-Qiong; Huang, Cheng-Lan; Liu, Min; Chen, Ying

    2012-11-01

    The wastewater containing polyvinyl alcohol (PVA) was characterized with poor biodegradability, and was difficult to remove. In order to find an economically reasonable and practical technology, the research on the removal efficiency of different concentration wastewater containing PVA by ozonation-activated sludge process was studied, and the result was compared with the traditional activated sludge process. The results showed that the ozonation-activated sludge process was not suitable for treating influent with COD below 500 mg x L(-1) and the wastewater PVA concentration was 10-30 mg x L(-1). When the influent COD was between 500-800 mg x L(-1) and the PVA concentration was 15-60 mg x L(-1), the system had advantages on dealing with this kind of wastewater, and the average removal efficiency of COD and PVA were 92.8% and 57.4%, which were better than the traditional activated sludge process 4.1% and 15.2% respectively. In addition, the effluent concentrations of COD could keep between 30-60 mg x L(-1). When the influent COD was 1 000-1 200 mg x L(-1) and the PVA concentration was 20-70 mg x L(-1), the average removal efficiencies of COD and PVA were 90.9% and 45.3%, which were better than the traditional activated sludge process 12.8% and 12.1% respectively, but the effluent should to be further treated. Compared with the traditional activated sludge process, ozonation-activated sludge process had high treatment efficiency, stable running effect, and effectively in dealing with industrial wastewater containing PVA. PMID:23323416

  16. Anomalous nanoinclusion effects of 2D MoS2 and WS2 nanosheets on the mechanical stiffness of polymer nanocomposites.

    PubMed

    Kim, Sung-Kon; Wie, Jeong Jae; Mahmood, Qasim; Park, Ho Seok

    2014-07-01

    Polymer inorganic nanosheet composites hold great promise in enhancing their physical and mechanical properties by increasing the interfacial area. Herein, we demonstrate the nanoinclusion effects of two-dimensional (2D) molybdenum disulfide (MoS2) and tungsten disulfide (WS2) nanosheets on the mechanical properties of the poly(vinyl alcohol) (PVA) polymer. At very small amounts of nanosheets (0.9 wt% for MoS2 and 2.0 wt% for WS2), nanocomposite films exhibit up to 65% improved mechanical properties than the neat PVA film because of strong non-covalent polymer-filler interactions by means of large contact area induced by the 2D geometry of nanosheets. As demonstrated by the decrease in the crystallinity of PVA and the increase in the glass transition temperature, 2D MoS2 is a more attractive filler than 2D WS2 in terms of reinforcing mechanical properties of PVA. These findings fit well with a modified Halpin-Tsai (H-T) model including a nanoscale interfacial layer that can support the observed reinforcements with extremely small 2D filler loadings. This study highlights the strong interplay between the polymer and inorganic nanosheets which plays an important role in greatly improving the mechanical stability of nanocomposites. PMID:24879420

  17. Methylene blue doped polymers: efficient media for optical recording

    NASA Astrophysics Data System (ADS)

    Ushamani, M.; Sreekumar, K.; Sudha Kartha, C.; Joseph, R.

    2004-05-01

    Polymer materials find application in optical storage technology, namely in the development of high information density and fast access type memories. A new polymer blend of methylene blue sensitized polyvinyl alcohol (PVA) and polyacrylic acid (PAA) in methanol is prepared and characterized and its comparison with methylene blue sensitized PVA in methanol and complexed methylene blue sensitized polyvinyl chloride (CMBPVC) is presented. The optical absorption spectra of the thin films of these polymers showed a strong and broad absorption region at 670-650 nm, matching the wavelength of the laser used. A very slow recovery of the dye on irradiation was observed when a 7:3 blend of polyvinyl alcohol/polyacrylic acid at a pH of 3.8 and a sensitizer concentration of 4.67 · 10-5 g/ml were used. A diffraction efficiency of up to 20% was observed for the MBPVA/alcohol system and an energetic sensitivity of 2000 mJ/cm2 was obtained in the photosensitive films with a spatial frequency of 588 lines/mm.

  18. Preparation and characterization of chitosan/gelatin/PVA hydrogel for wound dressings.

    PubMed

    Fan, Lihong; Yang, Huan; Yang, Jing; Peng, Min; Hu, Jin

    2016-08-01

    Chitosan (CS)/gelatin (Gel)/polyvinyl alcohol (PVA) hydrogels were prepared by the gamma irradiation method for usage in wound dressing applications. Chitosan and gelatin solution was mixed with poly(vinyl alcohol) (PVA) solution at different weight ratios of CS/Gel of 1:3, 1:2, 1:1, 2:1 and 3:1. The hydrogels irradiated at 40kGy. The structure of the hydrogels was characterized by using FT-IR and SEM. The CS/Gel/PVA hydrogels were characterized for physical properties and blood clotting activity. The tensile strength of CS/Gel/PVA hydrogel enhanced than on the basis of the Gel/PVA hydrogel. The highest tensile strength reached the 2.2Mpa. All hydrogels have shown a good coagulation effect. It takes only 5min for the BCI index to reached 0.032 only 5min when the weight ratio of CS/Gel was 1:1. It means that the hemostatic effect of hydrogels were optimal. And the hydrogrls also showed good pH-sensitivity, swelling ability and water evaporation rate. Therefore, this hydrogel showed a promising potential to be applied as wound dressing. PMID:27112893

  19. Electrooptic Kerr effect of porphyrin H-aggregates in polymer films: Polymer specific spectral blue shift

    NASA Astrophysics Data System (ADS)

    Suzuki, Masaya; Nakata, Kazuaki; Kuroda, Reiko; Kobayashi, Takayoshi; Tokunaga, Eiji

    2016-05-01

    J- and H-aggregates of porphyrin molecules (TPPS4) in spin-coated polymer films have been studied by electroabsorption and circular dichroism (CD) spectroscopy. A spectral blue shift of the H-band due to the electrooptic Kerr effect was observed for the first time. This occurs only for a polyvinylpyrrolidone (PVP) film, with negligibly small spectral shift observed in polyvinyl alcohol (PVA), polyvinyl sulfate (PVS), and polyacrylic acid (PAA) films, in contrast to the red shift of the J-band which is commonly observed for any host polymers. Accordingly, the CD activity in both of J- and H-bands is more enhanced in PVP films than in PVA films. The mechanism of the blue and red shifts of the respective H- and J-bands is discussed by invoking a helical structure in micro-aggregates, which is compatible with the CD spectra, based on the molecular rearrangement model. It is proved that blue- and red-shifts occur evenly to cancel each other in the H-band if a simple helical structure is assumed, in good agreement with no spectral shifts in the H-band in PVA, PVS, and PAA films.

  20. The Effect of Elongational Flow on the Placement and Orientation of Nanorods in Polymer: Modeling and Experiments

    NASA Astrophysics Data System (ADS)

    Park, Jay; Kalra, Vibha; Joo, Yong

    2012-02-01

    Nanorods are often incorporated into a polymer to enhance its functionality. Gaining control over the placement of nanorods in polymer is important to improve the desired nanocomposite material property and for application like solar cell. First, we used coarse-grained molecular dynamics (CGMD) simulation to quantitatively examine the effect of elongational flow on the placement of model nanorods in homopolymer matrix. We have investigated how flow strength, concentration, interaction, and aspect ratio of nanorods affect its placement in homopolymer. As an analogous experiment, we have electrospun polyvinyl alcohol (PVA) in water with Au nanorods. The experimental result showed dispersion and alignment of Au nanorods, as predicted by the simulation. We also demonstrated selective placement of nanorods along the outer layer of fiber by co-axially electrospinning PVA/Au nanorods and pure PVA as shell and core, respectively. The material properties of the PVA/Au nanocomposite fiber are tested to show its potential application such as electromagnetic interference (EMI) shielding. The good agreements between simulation and experiment suggest that CGMD simulation can be used as a predictive tool for controlling nanorod placement in a polymer under extensional flow.

  1. Water/alcohol soluble conjugated polymers as highly efficient electron transporting/injection layer in optoelectronic devices.

    PubMed

    Huang, Fei; Wu, Hongbin; Cao, Yong

    2010-07-01

    Water/alcohol soluble conjugated polymers (WSCPs) can be processed from water or other polar solvents, which offer good opportunities to avoid interfacial mixing upon fabrication of multilayer polymer optoelectronic devices by solution processing, and can dramatically improve charge injection from high work-function metal cathode resulting in greatly enhancement of the device performance. In this critical review, the authors provide a brief review of recent developments in this field, including the materials design, functional principles, and their unique applications as interface modification layer in solution-processable multilayer optoelectronic devices (135 references). PMID:20571672

  2. Assembly of poly(dopamine) films mixed with a nonionic polymer.

    PubMed

    Zhang, Yan; Thingholm, Bo; Goldie, Kenneth N; Ogaki, Ryosuke; Städler, Brigitte

    2012-12-21

    Poly(dopamine) (PDA) coatings have recently attracted considerable interest for a variety of applications. Here, we investigate the film deposition of dopamine mixed with a nonionic polymer (i.e., poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA), and poly(N-vinyl pyrrolidone) (PVP)) onto silica substrates using X-ray photoelectron spectroscopy and quartz crystal microbalance. Furthermore, we assess the possibility of coating silica colloids to yield polymer capsules and liposomes with these mixtures. We found that mixed PDA/PEG and PDA/PVA films are deposited without the need for a covalent linker such as an amine or thiol. We also discovered the first material, namely, PVP, that can suppress PDA film assembly. These fundamental findings give further insight into PDA film properties and contribute to establish PDA as a widely applicable coating. PMID:23205620

  3. Microstructure Changes of Copper Nano Particles via Polymer Solution and Reduction Firing Processes.

    PubMed

    Han, Young-Min; Jung, Choong-Hwan; Lee, Sang-Jin

    2016-02-01

    Cu nano particles were fabricated at a very low temperature via polymer solution and reduction firing processes using a polyvinyl alcohol (PVA) and Ar-4%H2 gas mixture. In the process, copper nitrate and 5 wt% PVA solution were dissolved in D.I. water and the organic-inorganic precursor sols were dried to porous gels. The precursor gels were calcined in an air atmosphere, and then refired at 250 degrees C-300 degrees C under an Ar-4%H2 atmosphere for the reduction of CuO. The morphology of precursor gels and CuO and Cu powders was strongly dependent on the PVA content, and the as- calcined CuO readily deoxidized to Cu with minimal residual carbon. The polymer also contributed to an atomic-scale copper cation distribution, which resulted in nano-sized CuO and Cu powders. The Cu powder synthesized with PVA content in a 4:1 ratio showed a crystallite size of about 20 nm or less. In this paper, the microstructure changes of Cu nano particles at each set of processing conditions were examined by SEM and TEM observations. PMID:27433717

  4. Comparison of the performances of four hydrophilic polymers as supports for lipase immobilisation

    PubMed Central

    Toscano, Lydia; Montero, Gisela; Stoytcheva, Margarita; Cervantes, Lourdes; Gochev, Velizar

    2014-01-01

    Four hydrophilic polymers in the form of beads – chitosan, alginate, alginate/polyvinyl alcohol (PVA), and chitosan-coated alginate – were used as supports for lipase immobilisation. Hydrogel beads were characterised by bead-size-distribution estimation, surface morphology studies, and polymer interactions assessment. Matrix performances – loading efficiency, immobilisation yield, enzyme activity, and stability retention – were evaluated and compared. Although the loading efficiency of the chitosan-coated Ca-alginate beads (79.8%) was inferior to that of the Ca-alginate (87%) and of the Ca-alginate/PVA beads (81.3%), their enzyme immobilisation yield (63.96%) was the most important. Moreover, lipase encapsulated in chitosan-coated Ca-alginate beads demonstrated better pH, thermal, and storage (89% residual activity after 30 days) stabilities. Immobilised lipase activity also increased in the order: alginate/PVA > chitosan > alginate > alginate/chitosan, and displayed a maximum at pH 8 and at temperatures of 45 °C (chitosan and Ca-alginate/PVA beads) and 50 °C (Ca-alginate and chitosan-coated Ca-alginate beads). Thus, chitosan-coated Ca-alginate beads could be considered as a suitable support for lipase immobilisation. PMID:26019488

  5. 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.

  6. Cellulose nanofibers reinforced sodium alginate-polyvinyl alcohol hydrogels: Core-shell structure formation and property characterization.

    PubMed

    Yue, Yiying; Han, Jingquan; Han, Guangping; French, Alfred D; Qi, Yadong; Wu, Qinglin

    2016-08-20

    Core-shell structured hydrogels consisting of a flexible interpenetrating polymer network (IPN) core and a rigid semi-IPN shell were prepared through chemical crosslinking of polyvinyl alcohol (PVA) and sodium alginate (SA) with Ca(2+) and glutaraldehyde. Short cellulose nanofibers (CNFs) extracted from energycane bagasse were incorporated in the hydrogel. The shell was micro-porous and the core was macro-porous. The hydrogels could be used in multiple adsorption-desorption cycles for dyes, and the maximum methyl blue adsorption capacity had a 10% increase after incorporating CNFs. The homogeneous distribution of CNFs in PVA-SA matrix generated additional hydrogen bonds among the polymer molecular chains, resulting in enhanced density, viscoelasticity, and mechanical strength for the hydrogel. Specifically, the compressive strength of the hydrogel reached 79.5kPa, 3.2 times higher than that of the neat hydrogel. PMID:27178920

  7. Synthesis of size-selected Pt nanoparticles supported on sulfonated graphene with polyvinyl alcohol for methanol oxidation in alkaline solutions

    NASA Astrophysics Data System (ADS)

    Yang, Jen-Ming; Wang, Sheng-An; Sun, Chia-Liang; Ger, Ming-Der

    2014-05-01

    In this study, the size-selected platinum (Pt) nanoparticles are loaded on sulfonated graphene with polyvinyl alcohol (PVA) as the conductive polymer for fuel-cell applications. Methanol oxidation reactions and reliability of various catalysts based on carbon black, graphene, and sulfonated graphene catalyst supports are compared under alkaline conditions. When PVA is used as the conductive polymer in place of Nafion, both the electrochemical active surface area (ECSA) and the methanol oxidation property were superior, irrespective of the catalyst and support. On the other hand, the catalyst with Pt on sulfonated graphene (Pt/sG) outperforms those on other supports. For methanol oxidation, the catalyst decay occurs with a decay of only 9.06% for Pt/sG. It is suggested that the sulfonate functional group on graphene not only improves catalytic activity but can also enhance catalyst reliability.

  8. Hydrothermal growth of NiSe 2 tubular microcrystals assisted by PVA

    NASA Astrophysics Data System (ADS)

    Fan, Hai; Zhang, Maofeng; Zhang, Xianwen; Qian, Yitai

    2009-10-01

    NiSe 2 tubular microcrystals assembled of nanoparticles have been prepared via a hydrothermal method in an ethanolamine and water mixed solution assisted by polyvinyl alcohol (PVA). The prepared tubular crystals with hexagonal structure are composed of nanoparticles with average diameter of 30 nm. It was found that the phase of the products could be adjusted by the molar ratio of the reactants (Ni/Se), and the morphology of the products could be greatly influenced by the quantity of surfactant PVA. Based on the experimental results, the possible formation mechanism of NiSe 2 tubular microcrystals is also discussed.

  9. Synthesis, characterization and nonlinear optical properties of silver/PVA nanocomposites

    NASA Astrophysics Data System (ADS)

    Faraji, N.; Mahmood Mat Younus, W.; Kharazmi, A.; Saion, E.; Shahmiri, M.; Tamchek, N.

    2012-09-01

    Silver/polyvinyl alcohol (PVA) nanocomposites are prepared via quick precipitation method, using hydrazine as a reducing agent. Preparing of silver/PVA nanocomposites by this method is done for the first time. The samples are characterized by Uv-Visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM). Nonlinear optical properties are carried out by Z-scan technique using a blue CW laser beam operated at wavelength 405 nm. It is shown that the synthesized samples have negative nonlinear refractive index and the magnitude is in the order of 10^-8. The nonlinear refractive index increases as amount of reducing agent increases.

  10. Alcohol-soluble interfacial fluorenes for inverted polymer solar cells: sequence induced spatial conformation dipole moment.

    PubMed

    Chen, Lie; Liu, Xiangfu; Wei, Yingkai; Wu, Feiyan; Chen, Yiwang

    2016-01-21

    Three fluorene-based alcohol-soluble organic small molecule electrolytes (SMEs) with different conjugated backbones, namely, TFTN-Br, FTFN-Br and FTTFN-Br, were designed as cathode interfacial layers for inverted polymer solar cells (i-PSCs). The insertion of SMEs to the ITO/active layer interfaces effectively lowered the energy barrier for electron transport and improved the inherent compatibility between the hydrophilic ITO and hydrophobic active layers. Due to these advantages, the device based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61 butyric acid methyl ester (PC61BM) with TFTN-Br as the cathode interfacial layer achieved an improved power conversion efficiency (PCE) of 3.8%, which is a 26% improvement when compared to the standard device comprising ZnO cathode interfacial layers (PCE = 3.0%). Devices with FTFN-Br and FTTFN-Br also showed an improved PCE of 3.1% and 3.5%, respectively. The variation in device performance enhancement was found to be primarily correlated with the different conformation of their assembly onto the electrode caused by the joint sequence of the polar group of the SMEs, consequently impacting the dipole moment and interface morphology. In addition, introducing SMEs as the cathode interfacial layer also produced devices with long-term stability. PMID:26694627

  11. Feasibility study for the production of ethyl alcohol and xanthan polymer from barley fermentation. Final report

    SciTech Connect

    Not Available

    1982-11-01

    Feasibility study results indicate that the project meets most criteria for economic and technical viability. The final process selected will produce an aftertax discounted cash flow rate of return between 33 and 41%. This level of return will occur over the range of raw material, energy and product unit prices that are probable over the next decade. In a typical year, using present day costs, the plant will produce gross revenue of $11,531,000 against production costs of $6,836,000. Pretax cash flow will be $5,947,000. This appears adequate to service acceptable levels of debt required to finance the $12,521,000 anticipated construction cost. The first year total cost including an initial three-month working capital reserve will be $13,620,000. The plant is designed to produce three major products: ethyl alcohol, distiller's dried grains and solubles and xanthan polymer. The individual process steps chosen to produce these products have all been demonstrated at the commercial level at other facilities. A pilot program has been in operation for nine months at the RBI facility to develop fermentation and recovery data on the xanthan process and to provide samples for customer comment and evaluation.

  12. Oxidative Mineralization and Characterization of Polyvinyl Alcohol Solutions for Wastewater Treatment

    SciTech Connect

    Oji, L.N.

    1999-08-31

    The principal objectives of this study are to identify an appropriate polyvinyl alcohol (PVA) oxidative mineralization technique, perform compatibility and evaporation fate tests for neat and mineralized PVA, and determine potential for PVA chemical interferences which may affect ion exchange utilization for radioactive wastewater processing in the nuclear industry.

  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. Alcohol.

    ERIC Educational Resources Information Center

    Schibeci, Renato

    1996-01-01

    Describes the manufacturing of ethanol, the effects of ethanol on the body, the composition of alcoholic drinks, and some properties of ethanol. Presents some classroom experiments using ethanol. (JRH)

  15. Synthesis and characterization of polyvinyl alcohol copolymer/phosphomolybdic acid-based crosslinked composite polymer electrolyte membranes

    NASA Astrophysics Data System (ADS)

    Anis, Arfat; Banthia, A. K.; Bandyopadhyay, S.

    Polymer electrolyte membrane fuel cells (PEMFCs) are very promising as future energy source due to their high-energy conversion efficiency and will help to solve the environmental concerns of energy production. Polymer electrolyte membrane (PEM) is recognised as the key element for an efficient PEMFC. Chemically crosslinked composite membranes consisting of a poly(vinyl alcohol-co-vinyl acetate-co-itaconic acid) (PVACO) and phosphomolybdic acid (PMA) have been prepared by solution casting and evaluated as proton conducting polymer electrolytes. The proton conductivity of the membranes is investigated as a function of PMA composition, crosslinking density and temperature. The membranes have also been characterized by FTIR spectroscopy, TGA, AFM and TEM. The proton conductivity of the composite membranes is of the order of 10 -3 S cm -1 and shows better resistance to methanol permeability than Nafion 117 under similar measurement conditions.

  16. Crystal growth of ZnO bulk by CVT method using PVA

    NASA Astrophysics Data System (ADS)

    Udono, H.; Sumi, Y.; Yamada, S.; Kikuma, I.

    2008-04-01

    Seeded crystal growth of Zinc oxide (ZnO) by the closed ampoule chemical vapor transport (CVT) is carried out using polyvinyl alcohol (PVA) as a transport agent. Under the conditions of TS=1100 °C, Δ T=10 K and the amount of PVA=0.13-0.91 mg/cm 3, single-crystalline ZnO was grown continuously on the ZnO seed-crystal, of which the surface was (0 0 0 1) Zn-face. The grown crystals had well-marked growth facets belonged to {1 0 1¯0} and {1 0 1¯ 1} faces. The color of the crystals was changed from pale yellow to dark orange-red depending on the amount of PVA. Typical electron density and the Hall mobility of the crystals were 1×10 17 cm -3 and 2×10 2 cm 2/V s at 300 K, respectively.

  17. 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.

  18. Coupled electron beam radiation and MBR treatment of textile wastewater containing polyvinyl alcohol.

    PubMed

    Sun, Weihua; Chen, Jun; Chen, Lujun; Wang, Jianlong; Zhang, Yongming

    2016-07-01

    Advanced oxidation processes (AOP) can be combined with biological treatments for recalcitrant organic pollutant decomposition. However, there has been no thorough investigation on the coupling of AOPs and membrane bioreactors (MBR) to treat polymer organic pollutants. This study proposes a new AOP that couples electron beam (EB) radiation and MBR treatment. This method was applied to treat real textile effluents containing polyvinyl alcohol (PVA). During the stable operation stage, 31 ± 7% (n = 28) COD was removed by the EB-MBR process. COD removal was enhanced to 45% at the end of the research period without process optimization. In addition, both the membrane flux and activated sludge system exhibited good stability. Only a 2% membrane flux decreased was observed after a 46 d operation period. PVA radiolysis and biofacies analysis mechanisms are also discussed. By contrast, PVA degradation using only the MBR treatment was ineffective in this study. This ineffectiveness was caused by membrane interception and floccule formation by PVA and activated sludge. PMID:27107385

  19. Low doping concentration studies of doped PVA-Coumarin nanocomposite films

    NASA Astrophysics Data System (ADS)

    Tripathi, J.; Tripathi, S.; Bisen, R.; Sharma, A.; Choudhary, A.; Shripathi, T.

    2016-05-01

    The observations of combination of Poly (vinyl) alcohol and Coumarin properties in nanocmposite films are reported. The X-ray diffraction measurements reveal nanocrystalline nature of PVA film, which remains nanocrystalline after doping Coumarin but along with PVA peaks, additional peak due to dopant crystallinity is seen. The absorption edge shows a double edge feature, where distinct bandgaps for PVA host and dopant Coumarin are obtained. However at a higher doping wt % of 1 and 2, the absorption is mainly dominated by Coumarin and single absorption edge is observed giving a bandgap equal to that of bulk Coumarin (3.3 eV). The composite formation affects the bonding of host drastically and is seen through the bond modification in FTIR spectra. The results suggest that doping below 2 wt% is advantageous as combination of PVA and Coumarin properties are obtained but at 2 wt %, the properties are dominated by mainly Coumarin and the signature of PVA from optical properties is completely lost.

  20. Synthesis and characterization of CdSe quantum dots dispersed in PVA matrix by chemical route

    NASA Astrophysics Data System (ADS)

    Khan, Zubair M. S. H.; Ganaie, Mohsin; Khan, Shamshad A.; Husain, M.; Zulfequar, M.

    2016-05-01

    CdSe quantum dots using polyvinyl alcohol as a capping agent have been synthesized via a simple heat induced thermolysis technique. The structural analysis of CdSe/PVA thin film was studied by X-ray diffraction, which confirms crystalline nature of the prepared film. The surface morphology and particle size of the prepared sample was studied by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The SEM studies of CdSe/PVA thin film shows the average size of particles in the form of clusters of several quantum dots in the range of 10-20 nm. The morphology of CdSe/PVA thin film was further examined by TEM. The TEM image shows the fringes of tiny dots with average sizes of 4-7 nm. The optical properties of CdSe/PVA thin film were studied by UV-VIS absorption spectroscopy. The CdSe/PVA quantum dots follow the role of direct transition and the optical band gap is found to be 4.03 eV. From dc conductivity measurement, the observed value of activation energy was found to be 0.71 eV.

  1. Natural polysaccharides promote chondrocyte adhesion and proliferation on magnetic nanoparticle/PVA composite hydrogels.

    PubMed

    Hou, Ruixia; Nie, Lei; Du, Gaolai; Xiong, Xiaopeng; Fu, Jun

    2015-08-01

    This paper aims to investigate the synergistic effects of natural polysaccharides and inorganic nanoparticles on cell adhesion and growth on intrinsically cell non-adhesive polyvinyl alcohol (PVA) hydrogels. Previously, we have demonstrated that Fe2O3 and hydroxyapatite (nHAP) nanoparticles are effective in increasing osteoblast growth on PVA hydrogels. Herein, we blended hyaluronic acid (HA) and chondroitin sulfate (CS), two important components of cartilage extracellular matrix (ECM), with Fe2O3/nHAP/PVA hydrogels. The presence of these natural polyelectrolytes dramatically increased the pore size and the equilibrium swelling ratio (ESR) while maintaining excellent compressive strength of hydrogels. Chondrocytes were seeded and cultured on composite PVA hydrogels containing Fe2O3, nHAP and Fe2O3/nHAP hybrids and Fe2O3/nHAP with HA or CS. Confocal laser scanning microscopy (CLSM) and cell counting kit-8 (CCK-8) assay consistently confirmed that the addition of HA or CS promotes chondrocyte adhesion and growth on PVA and composite hydrogels. Particularly, the combination of HA and CS exhibited further promotion to cell adhesion and proliferation compared with any single polysaccharide. The results demonstrated that the magnetic composite nanoparticles and polysaccharides provided synergistic promotion to cell adhesion and growth. Such polysaccharide-augmented composite hydrogels may have potentials in biomedical applications. PMID:26037704

  2. Synthesis, characterization and antibacterial activity of biodegradable starch/PVA composite films reinforced with cellulosic fibre.

    PubMed

    Priya, Bhanu; Gupta, Vinod Kumar; Pathania, Deepak; Singha, Amar Singh

    2014-08-30

    Cellulosic fibres reinforced composite blend films of starch/poly(vinyl alcohol) (PVA) were prepared by using citric acid as plasticizer and glutaraldehyde as the cross-linker. The mechanical properties of cellulosic fibres reinforced composite blend were compared with starch/PVA crossed linked blend films. The increase in the tensile strength, elongation percentage, degree of swelling and biodegradability of blend films was evaluated as compared to starch/PVA crosslinked blend films. The value of different evaluated parameters such as citric acid, glutaraldehyde and reinforced fibre to starch/PVA (5:5) was found to be 25 wt.%, 0.100 wt.% and 20 wt.%, respectively. The blend films were characterized using Fourier transform-infrared spectrophotometry (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG). Scanning electron microscopy illustrated a good adhesion between starch/PVA blend and fibres. The blend films were also explored for antimicrobial activities against pathogenic bacteria like Staphylococcus aureus and Escherichia coli. The results confirmed that the blended films may be used as exceptional material for food packaging. PMID:24815414

  3. SHI irradiated PVA/Ag nanocomposites and possibility of UV blocking

    NASA Astrophysics Data System (ADS)

    Chahal, Rishi Pal; Mahendia, Suman; Tomar, A. K.; Kumar, Shyam

    2016-02-01

    The polyvinyl alcohol-silver (PVA/Ag) nanocomposites were prepared by in-situ chemical reduction method. The appearance of surface plasmon resonance (SPR) in the absorption spectrum of PVA/Ag nanocomposite films around 425 nm, confirmed the presence of Ag in the form of nanoparticles in host PVA matrix. In order to study the effect of swift heavy ions (SHI) irradiation on the optical and structural properties of these nanocomposites, the prepared films were irradiated to 90 MeV O6+ ion beam at two different fluence of 3 × 1010 and 1 × 1011 ions/cm2. The optical energy gap is found to be reduced from 4.57 eV (for PVA/Ag nanocomposite without irradiation) to 3.05 eV after irradiation at fluence of 1 × 1011 ions/cm2. The decline in the transmission of PVA/Ag nanocomposites in ultraviolet region, as a result of SHI irradiation, leads to their possible application in UV blocking devices. The induced structural re-arrangements, as a result of SHI irradiation, were revealed through the FTIR & Raman spectroscopy and found to be in strong association with the changes in optical behavior of these nanocomposites.

  4. Preparation and properties of polyvinyl alcohol microspheres

    SciTech Connect

    Campbell, J.H.; Grens, J.Z.; Poco, J.F.; Ives, B.H.

    1986-06-01

    Polyvinyl alcohol (PVA) microspheres, having a size range of approx.150- to 250-..mu..m diameter with 1- to 5-..mu..m wall thickness, have been fabricated using a solution droplet technique. The spheres were developed for possible use on the Lawrence Livermore National Laboratory (LLNL) Inertial Confinement Fusion (ICF) Program. PVA, a polymer chosen based on earlier survey work carried out at KMS Fusion, Inc., has good strength, low hydrogen permeability, is optically transparent, and water soluble. The latter property makes it safe and easy to use in our droplet generator system. A unique dual-orifice droplet generator was used to prepare the spheres. The droplet generator operating conditions and the column processing parameters were chosen using results from our 1-D model calculations as a guide. The polymer microsphere model is an extension of the model we developed to support the glass sphere production. After preparation, the spheres were physically characterized for surface quality, sphericity, wall thickness (and uniformity), and size. We also determined the buckling pressure for both uncoated and CH-coated spheres. Radiation stability to beta decay (from tritium) was evaluated by exposing the spheres to a 7-keV electron beam. The results from these and other physical property measurements are presented in this report.

  5. Detection of ethanol in alcoholic beverages or vapor phase using fluorescent molecules embedded in a nanofibrous polymer.

    PubMed

    Akamatsu, Masaaki; Mori, Taizo; Okamoto, Ken; Komatsu, Hirokazu; Kumagai, Ken; Shiratori, Seimei; Yamamura, Masaki; Nabeshima, Tatsuya; Sakai, Hideki; Abe, Masahiko; Hill, Jonathan P; Ariga, Katsuhiko

    2015-03-25

    An alcohol sensor was developed using the solid-state fluorescence emission of terphenyl-ol (TPhOH) derivatives. Admixtures of TPhOH and sodium carbonate exhibited bright sky-blue fluorescence in the solid state upon addition of small quantities of ethanol. A series of terphenol derivatives was synthesized, and the effects of solvent polarities and the structures of these π-conjugated systems on their fluorescence were systematically investigated by using fluorescence spectroscopy. In particular, π-extended TPhOHs and TPhOHs containing electron-withdrawing groups exhibited significant solvatochromism, and fluorescence colors varied from blue to red. Detection of ethanol contents in alcohol beverages (detection limit ∼ 5 v/v %) was demonstrated using different TPhOHs revealing the effect of molecular structure on sensing properties. Ethanol contents in alcoholic beverages could be estimated from the intensity of the fluorescence elicited from the TPhOHs. Moreover, when terphenol and Na2CO3 were combined with a water-absorbent polymer, ethanol could be detected at lower concentrations. Detection of ethanol vapor (8 v/v % in air) was also accomplished using a nanofibrous polymer scaffold as the immobilized sensing film. PMID:25756646

  6. Solid state self-healing system: Effects of using PDGEBA, PVC and PVA as linear healing agents

    NASA Astrophysics Data System (ADS)

    Muhamad, Noor Nabilah; Jamil, Mohd. Suzeren Md.; Abdullah, Shahrum

    2014-09-01

    The solid state self-healing system was obtained by employing a thermosetting epoxy resin, into which a thermoplastic is dissolved. In this study, the effect of healing efficiency was investigated by using different thermoplastic polymers which are poly(bisphenol-A-co-epichlorohydrin), polyvinyl chloride and polyvinyl alcohol as healing agents. Healing was achieved by heating the fractured resins to a specific temperature i.e. above their glass transition temperature (Tg) which obtained from dynamic mechanical analysis (DMA) to mobilize the polymeric chains of the healing agent. The curing reaction in the epoxy resins were characterized by means of Fourier transform infrared spectroscopy (FTIR). Izod impact test was been performed to demonstrate self-healing of the different specimens. Under test, it was found that healable resin with PDGEBA has highest healing efficiency followed by PVC and PVA, with 63%, 35% and 18% of average percentage healing efficiencies respectively. These results are due to the different solubility parameters of the thermoset/network and thermoplastic polymer which led to the phase separation. Morphological studies prove the fracture-healing process and morphological properties of the resins.

  7. 40 CFR 721.10316 - Dicyclopentadiene polymer with maleic anhydride and alkyl alcohols (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Dicyclopentadiene polymer with maleic... Significant New Uses for Specific Chemical Substances § 721.10316 Dicyclopentadiene polymer with maleic.... (1) The chemical substance identified generically as dicyclopentadiene polymer with maleic...

  8. 40 CFR 721.10316 - Dicyclopentadiene polymer with maleic anhydride and alkyl alcohols (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Dicyclopentadiene polymer with maleic... Significant New Uses for Specific Chemical Substances § 721.10316 Dicyclopentadiene polymer with maleic.... (1) The chemical substance identified generically as dicyclopentadiene polymer with maleic...

  9. 40 CFR 721.10316 - Dicyclopentadiene polymer with maleic anhydride and alkyl alcohols (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Dicyclopentadiene polymer with maleic... Significant New Uses for Specific Chemical Substances § 721.10316 Dicyclopentadiene polymer with maleic.... (1) The chemical substance identified generically as dicyclopentadiene polymer with maleic...

  10. Effects of PVA, agar contents, and irradiation doses on properties of PVA/ws-chitosan/glycerol hydrogels made by γ-irradiation followed by freeze-thawing

    NASA Astrophysics Data System (ADS)

    Yang, Xiaomin; Zhu, Zhiyong; Liu, Qi; Chen, Xiliang; Ma, Mingwang

    2008-08-01

    Poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan)/glycerol hydrogels were prepared by γ-irradiation and γ-irradiation followed by freeze-thawing, respectively. The effects of irradiation dose and the contents of PVA and agar on the swelling, rheological, and thermal properties of these hydrogels were investigated. The swelling capacity decreases while the mechanical strength increases with increasing PVA or agar content. Increasing the irradiation dose leads to an increase in chemical crosslinking density but a decrease in physical crosslinking density. Hydrogels made by irradiation followed by freeze-thawing own smaller swelling capacity but larger mechanical strength than those made by pure irradiation. The storage modulus of the former hydrogels decreases above 50 °C and above 70 °C it comes to the same value as that prepared by irradiation. The ordered association of PVA is influenced by both chemical and physical crosslinkings and by the presence of ws-chitosan and glycerol. These hydrogels are high sensitive to pH and ionic strength, indicating that they may be useful in stimuli-responsive drug release system.

  11. In vitro and in vivo evaluation of blood coagulation activation of polyvinyl alcohol hydrogel plus dextran-based vascular grafts.

    PubMed

    Alexandre, Nuno; Costa, Elísio; Coimbra, Susana; Silva, Alice; Lopes, Ascensão; Rodrigues, Miguel; Santos, Marta; Maurício, Ana Colette; Santos, José Domingos; Luís, Ana Lúcia

    2015-04-01

    Polyvinyl alcohol hydrogel (PVA) is a water-soluble synthetic polymer that is commonly used in biomedical applications including vascular grafting. It was argued that the copolymerization of PVA with dextran (Dx) can result in improvement of blood-biomaterial interactions. The focus of this experimental study was to assess that interaction through an in vivo and in vitro evaluation of the coagulation system activation. The thrombogenicity of the copolymer was determined by quantification of platelet adhesion through the lactate dehydrogenase assay, determination of whole blood clotting time, and by quantification of platelet activation by flow cytometry. The thrombin-antithrombin complex blood levels were also determined. The obtained results for the in vitro assays suggested a non-thrombogenic profile for PVA/Dx. Additionally in vivo coagulation and hematological parameters were determined in an animal model after PVA/Dx vascular graft implantation. For coagulation homeostasis assessment, the intrinsic and extrinsic pathway's activation was determined by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). Other markers of coagulation and inflammation activation including d-dimers, interleukin-6, and C-reactive protein were also assessed. The PVA/Dx copolymer tended to inhibit platelet adhesion/activation process and the contact activation process for coagulation. These results were also confirmed with the in vivo experiments where the measurements for APTT, interleukin-6, and C-reactive protein parameters were normal considering the species normal range of values. The response to those events is an indicator of the in vitro and in vivo hemocompatibility of PVA/Dx and it allows us to select this biomaterial for further preclinical trials in vascular reconstruction. PMID:25044790

  12. Conjugated polymer dots-on-electrospun fibers as a fluorescent nanofibrous sensor for nerve gas stimulant.

    PubMed

    Jo, Seonyoung; Kim, Jongho; Noh, Jaeguk; Kim, Daigeun; Jang, Geunseok; Lee, Naeun; Lee, Eunji; Lee, Taek Seung

    2014-12-24

    A novel chemical warfare agent sensor based on conjugated polymer dots (CPdots) immobilized on the surface of poly(vinyl alcohol) (PVA)-silica nanofibers was prepared with a dots-on-fibers (DoF) hybrid nanostructure via simple electrospinning and subsequent immobilization processes. We synthesized a polyquinoxaline (PQ)-based CP as a highly emissive sensing probe and employed PVA-silica as a host polymer for the elctrospun fibers. It was demonstrated that the CPdots and amine-functionalized electrospun PVA-silica nanofibers interacted via an electrostatic interaction, which was stable under prolonged mechanical force. Because the CPdots were located on the surface of the nanofibers, the highly emissive properties of the CPdots could be maintained and even enhanced, leading to a sensitive turn-off detection protocol for chemical warfare agents. The prepared fluorescent DoF hybrid was quenched in the presence of a chemical warfare agent simulant, due to the electron transfer between the quinoxaline group in the polymer and the organophosphorous simulant. The detection time was almost instantaneous, and a very low limit of detection was observed (∼1.25 × 10(-6) M) with selectivity over other organophosphorous compounds. The DoF hybrid nanomaterial can be developed as a rapid, practical, portable, and stable chemical warfare agent-detecting system and, moreover, can find further applications in other sensing systems simply by changing the probe dots immobilized on the surface of nanofibers. PMID:25431844

  13. Do the cations in clay and the polymer matrix affect quantum dot fluorescent properties?

    PubMed

    Wei, Wenjun; Liu, Cui; Liu, Jiyan; Liu, Xueqing; Zou, Linling; Cai, Shaojun; Shi, Hong; Cao, Yuan-Cheng

    2016-06-01

    This paper studied the effects of cations and polymer matrix on the fluorescent properties of quantum dots (QDs). The results indicated that temperature has a greater impact on fluorescence intensity than clay cations (mainly K(+) and Na(+) ). Combined fluorescence lifetime and steady-state spectrometer tests showed that QD lifetimes all decreased when the cation concentration was increased, but the quantum yields were steady at various cation concentrations of 0, 0.05, 0.5 and 1 M. Poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and diepoxy resin were used to study the effects of polymers on QD lifetime and quantum yield. The results showed that the lifetime for QDs 550 nm in PEO and PVA was 17.33 and 17.12 ns, respectively; for the epoxy resin, the lifetime was 0.74 ns, a sharp decrease from 24.47 ns. The quantum yield for QDs 550 nm changed from 34.22% to 7.45% and 7.81% in PEO and PVA, respectively; for the epoxy resin the quantum yield was 2.25%. QDs 580 nm and 620 nm showed the same results as QDs 550 nm. This study provides useful information on the design, synthesis and application of QDs-polymer luminescent materials. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26663530

  14. PMMA-Etching-Free Transfer of Wafer-scale Chemical Vapor Deposition Two-dimensional Atomic Crystal by a Water Soluble Polyvinyl Alcohol Polymer Method.

    PubMed

    Van Ngoc, Huynh; Qian, Yongteng; Han, Suk Kil; Kang, Dae Joon

    2016-01-01

    We have explored a facile technique to transfer large area 2-Dimensional (2D) materials grown by chemical vapor deposition method onto various substrates by adding a water-soluble Polyvinyl Alcohol (PVA) layer between the polymethyl-methacrylate (PMMA) and the 2D material film. This technique not only allows the effective transfer to an arbitrary target substrate with a high degree of freedom, but also avoids PMMA etching thereby maintaining the high quality of the transferred 2D materials with minimum contamination. We applied this method to transfer various 2D materials grown on different rigid substrates of general interest, such as graphene on copper foil, h-BN on platinum and MoS2 on SiO2/Si. This facile transfer technique has great potential for future research towards the application of 2D materials in high performance optical, mechanical and electronic devices. PMID:27616038

  15. Biomaterial characteristics and application of silicone rubber and PVA hydrogels mimicked in organ groups for prostate brachytherapy.

    PubMed

    Li, Pan; Jiang, Shan; Yu, Yan; Yang, Jun; Yang, Zhiyong

    2015-09-01

    It is definite that transparent material with similar structural characteristics and mechanical properties to human tissue is favorable for experimental study of prostate brachytherapy. In this paper, a kind of transparent polyvinyl alcohol (PVA) hydrogel and silicone rubber are developed as suitable substitutions for human soft tissue. Segmentation and 3D reconstruction of medical image are performed to manufacture the mould of organ groups through rapid prototyping technology. Micro-structure observation, force test and CCD deformation test have been conducted to investigate the structure and mechanical properties of PVA hydrogel used in organ group mockup. Scanning electron microscope (SEM) image comparison results show that PVA hydrogel consisting of 3 g PVA, 17 g de-ionized water, 80 g dimethyl-sulfoxide (DMSO), 4 g NaCl, 1.5 g NaOH, 3 g epichlorohydrin (ECH) and 7 freeze/thaw cycles reveals similar micro-structure to human prostate tissue. Through the insertion force comparison between organ group mockup and clinical prostate brachytherapy, PVA hydrogel and silicone rubber are found to have the same mechanical properties as prostate tissue and muscle. CCD deformation test results show that insertion force suffers a sharp decrease and a relaxation of tissue deformation appears when needle punctures the capsule of prostate model. The results exhibit that organ group mockup consisting of PVA hydrogel, silicone rubber, membrane and agarose satisfies the needs of prostate brachytherapy simulation in general and can be used to mimic the soft tissues in pelvic structure. PMID:26042767

  16. Engineering a Highly Hydrophilic PVDF Membrane via Binding TiO₂Nanoparticles and a PVA Layer onto a Membrane Surface.

    PubMed

    Qin, Aiwen; Li, Xiang; Zhao, Xinzhen; Liu, Dapeng; He, Chunju

    2015-04-29

    A highly hydrophilic PVDF membrane was fabricated through chemically binding TiO2 nanoparticles and a poly(vinyl alcohol) (PVA) layer onto a membrane surface simultaneously. The chemical composition of the modified membrane surface was determined by X-ray photoelectron spectroscopy, and the binding performance of TiO2 nanoparticles and the PVA layer was investigated by a rinsing test. The results indicated that the TiO2 nanoparticles were uniformly and strongly tailored onto the membrane surface, while the PVA layer was firmly attached onto the surface of TiO2 nanoparticles and the membrane by adsorption-cross-linking. The possible mechanisms during the modification process and filtration performance, i.e., water permeability and bovine serum albumin (BSA) rejection, were investigated as well. Furthermore, antifouling property was discussed through multicycles of BSA solution filtration tests, where the flux recovery ratio was significantly increased from 20.0% for pristine PVDF membrane to 80.5% for PVDF/TiO2/PVA-modified membrane. This remarkable promotion is mainly ascribed to the improvement of surface hydrophilicity, where the water contact angle of the membrane surface was decreased from 84° for pristine membrane to 24° for PVDF/TiO2/PVA membrane. This study presents a novel and varied strategy for immobilization of nanoparticles and PVA layer on substrate surface, which could be easily adapted for a variety of materials for surface modification. PMID:25806418

  17. 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

  18. 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

  19. Initiation of atomic layer deposition of metal oxides on polymer substrates by water plasma pretreatment

    SciTech Connect

    Steven Brandt, E.; Grace, Jeremy M.

    2012-01-15

    The role of surface hydroxyl content in atomic layer deposition (ALD) of aluminum oxide (AO) on polymers is demonstrated by performing an atomic layer deposition of AO onto a variety of polymer types, before and after pretreatment in a plasma struck in water vapor. The treatment and deposition reactions are performed in situ in a high vacuum chamber that is interfaced to an x-ray photoelectron spectrometer to prevent adventitious exposure to atmospheric contaminants. X-ray photoelectron spectroscopy is used to follow the surface chemistries of the polymers, including theformation of surface hydroxyls and subsequent growth of AO by ALD. Using dimethyl aluminum isopropoxide and water as reactants, ALD is obtained for water-plasma-treated poly(styrene) (PS), poly(propylene) (PP), poly(vinyl alcohol) (PVA), and poly(ethylene naphthalate) (PEN). For PS, PP, and PEN, initial growth rates of AO on the native (untreated) polymers are at least an order of magnitude lower than on the same polymer surface following the plasma treatment. By contrast, native PVA is shown to initiate ALD of AO as a result of the presence of intrinsic surface hydroxyls that are derived from the repeat unit of this polymer.

  20. Effect of ethylene carbonate as a plasticizer on CuI/PVA nanocomposite: Structure, optical and electrical properties

    PubMed Central

    Mohamed, Shaimaa A.; Al-Ghamdi, A.A.; Sharma, G.D.; El Mansy, M.K.

    2013-01-01

    Layers of ethylene carbonate (EC) modified CuI/PVA polymer composites were prepared by growth of CuI nano-particles in an aqueous solution of PVA followed by casting at room temperature. The structural, thermal, optical, electrical and di-electrical characterization of polymer composites was investigated using different techniques. These investigations confirm the growth of CuI nano-particles and reduction of PVA crystallinity by increasing ethylene carbonate concentration. These results show that energy band gap and bulk conductivity increase while activation energy reduces with the increase of EC concentration in the composite. Moreover, the variation of the dielectric permittivity and dielectric loss with EC content are found to obey Debye dispersion relations. PMID:25685474

  1. A polyvinyl alcohol/ p-sulfonate phenolic resin composite proton conducting membrane

    NASA Astrophysics Data System (ADS)

    Wu, Chien-Shun; Lin, Fan-Yen; Chen, Chih-Yuan; Chu, Peter P.

    Membranes composed of poly(vinyl alcohol) (PVA) and a proton source polymer, sulfonated phenolic resin (s-Ph) displayed good proton conductivity of the order of 10 -2 S cm -1 at ambient temperatures. Upon cross-linking above 110 °C, covalent links between the sulfonate groups of the phenolic resin and the hydroxyl groups of the PVA were established. Although this sacrificed certain sulfonate groups, the conductivity value was still preserved at the 10 -2 S cm -1 level. In sharp contrast to Nafion, the current membrane (both before and after cross-linking) was also effective in reducing the methanol uptake where the swelling ratio decreased with increase of methanol concentration. Although both the methanol permeation and the proton conductivity were lower compared to Nafion, the conductivity/permeability ratio of 0.97 for the PVA/s-Ph is higher than that determined for Nafion. The results suggested the effectiveness of proton transport in the polymer-complex structure and the possibility that a high proton conductivity can be realized with less water.

  2. Barrier properties of poly(vinyl alcohol) membranes containing carbon nanotubes or activated carbon.

    PubMed

    Surdo, Erin M; Khan, Iftheker A; Choudhury, Atif A; Saleh, Navid B; Arnold, William A

    2011-04-15

    Carbon nanotube addition has been shown to improve the mechanical properties of some polymers. Because of their unique adsorptive properties, carbon nanotubes may also improve the barrier performance of polymers used in contaminant containment. This study compares the barrier performance of poly(vinyl alcohol) (PVA) membranes containing single-walled carbon nanotubes (SWCNTs) to that for PVA containing powdered activated carbon (PAC). Raw and surface-functionalized versions of each sorbent were tested for their abilities to adsorb 1,2,4-trichlorobenzene and Cu(2+), representing the important hydrophobic organic and heavy metal contaminant classes, as they diffused across the PVA. In both cases, PAC (for 1,2,4-trichlorobenzene) and functionalized PAC (for Cu(2+)) outperformed SWCNTs on a per mass basis by trapping more of the contaminants within the barrier membrane. Kinetics of sorption are important in evaluating barrier properties, and poor performance of SWCNT-containing membranes as 1,2,4-TCB barriers is attributed to kinetic limitations. PMID:21349636

  3. Electrospun polylactic acid and polyvinyl alcohol fibers as efficient and stable nanomaterials for immobilization of lipases.

    PubMed

    Sóti, Péter Lajos; Weiser, Diana; Vigh, Tamás; Nagy, Zsombor Kristóf; Poppe, László; Marosi, György

    2016-03-01

    Electrospinning was applied to create easy-to-handle and high-surface-area membranes from continuous nanofibers of polyvinyl alcohol (PVA) or polylactic acid (PLA). Lipase PS from Burkholderia cepacia and Lipase B from Candida antarctica (CaLB) could be immobilized effectively by adsorption onto the fibrous material as well as by entrapment within the electrospun nanofibers. The biocatalytic performance of the resulting membrane biocatalysts was evaluated in the kinetic resolution of racemic 1-phenylethanol (rac-1) and 1-phenylethyl acetate (rac-2). Fine dispersion of the enzymes in the polymer matrix and large surface area of the nanofibers resulted in an enormous increase in the activity of the membrane biocatalyst compared to the non-immobilized crude powder forms of the lipases. PLA as fiber-forming polymer for lipase immobilization performed better than PVA in all aspects. Recycling studies with the various forms of electrospun membrane biocatalysts in ten cycles of the acylation and hydrolysis reactions indicated excellent stability of this forms of immobilized lipases. PLA-entrapped lipases could preserve lipase activity and enantiomer selectivity much better than the PVA-entrapped forms. The electrospun membrane forms of CaLB showed high mechanical stability in the repeated acylations and hydrolyses than commercial forms of CaLB immobilized on polyacrylamide beads (Novozyme 435 and IMMCALB-T2-150). PMID:26724947

  4. 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. PMID:26900879

  5. Modification of structural and optical properties of polyvinyl alcohol/polyethylene glycol thin film by laser irradiation

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Benthami, K.; Abutalib, M. M.

    2016-02-01

    The effect of infrared laser irradiation on the structural and the optical properties of polyvinyl alcohol/polyethylene glycol (PVA/PEG) co-polymer has been investigated. Thin films of PVA/PEG (nearly 50 µm thickness) were irradiated up to 15 J/cm2 of Ga-As laser pulses of 904 nm, 5 W power, and 200-ns pulse duration. The resultant effect of laser irradiation on the structural properties of PVA/PEG has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Further, the refractive index and the color difference between the exposed samples and the pristine have been studied. FTIR spectroscopy showed that the PVA/PEG samples exhibited degradation under the effect of laser irradiation up to 9 J/cm2, where crosslinking started and continued until 15 J/cm2. The refractive index had a minimum value of 1.5020 at 9 J/cm2, accompanied by a high degree of ordering and maximum value of 1.5640 at 15 J/cm2, with an increase in disordering character due to the degradation and crosslinking formation inside the sample, respectively. Moreover, the color intensity ΔE was greatly increased with increasing the laser fluence, accompanied by a significant increase in the yellow color component.

  6. Electrical transport properties and current density - voltage characteristic of PVA-Ag nanocomposite film

    NASA Astrophysics Data System (ADS)

    Das, A. K.; Dutta, B.; Sinha, S.; Mukherjee, A.; Basu, S.; Meikap, A. K.

    2016-05-01

    Silver (Ag) nanoparticle and Polyvinyl alcohol (PVA) - Silver (Ag) composite have been prepared and its dielectric constant, ac conductivity, and current density-voltage characteristics have been studied, at and above room temperature. Here correlated barrier hopping found to be the dominant charge transport mechanism with maximum barrier height of 0.11 eV. The sample, under ±5 V applied voltage, show back to back Schottky diode behaviour.

  7. ZnS/PVA nanocomposites for nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Ozga, K.; Michel, J.; Nechyporuk, B. D.; Ebothé, J.; Kityk, I. V.; Albassam, A. A.; El-Naggar, A. M.; Fedorchuk, A. O.

    2016-07-01

    We have found a correlation between ZnS nanocomposite nonlinear optical features and technological processing using electrolytic method. In the earlier researches this factor was neglected. However, it may open a new stage for operation by photovoltaic features of the well known semiconductors within a wide range of magnitudes. The titled nanostructured zinc sulfide (ZnS) was synthesized by electrolytic method. The obtained ZnS nano-crystallites possessed nano-particles sizes varying within 1.6 nm…1.8 nm. The titled samples were analyzed by XRD, HR-TEM, STEM, and nonlinear optical methods such as photo-induced two-photon absorption (TPA) and second harmonic generation (SHG). For this reason the nano-powders were embedded into the photopolymer poly(vinyl) alcohol (PVA) matrices. Role of aggregation in the mentioned properties is discussed. Possible origin of the such correlations are discussed.

  8. Studies on PVA pectin cryogels containing crosslinked enzyme aggregates of keratinase.

    PubMed

    Martínez, Yanina N; Cavello, Ivana; Cavalitto, Sebastián; Illanes, Andres; Castro, Guillermo R

    2014-05-01

    Polyvinyl alcohol-pectin (PVA-P) films containing enrofloxacin and keratinase were developed to treat wounds and scars produced by burns and skin injuries. However, in order to prevent enzyme inactivation at the interface between the patch and the scars, crosslinked enzyme aggregates (CLEAs) from a crude extract of keratinase produced by Paecilomyces lilacinus (LPSC#876) were synthesized by precipitation with acetone and crosslinking with glutaraldehyde. Soluble vs. CLEA keratinase (K-CLEA) activities were tested in 59% (v/v) hydrophobic (isobutanol and n-hexane) and hydrophilic (acetone and dimethylsulfoxide) solvents mixtures. K-CLEA activity was 1.4, 1.7 and 6.6 times higher in acetone, n-hexane and isobutanol than the soluble enzyme at 37 °C after 1 h of incubation, respectively. K-CLEA showed at least 45% of enzyme residual activity in the 40-65 °C range, meanwhile the soluble biocatalyst was fully inactivated at 65 °C after 1h incubation. Also, the soluble enzyme was completely inactivated after 12 h at pH 7.4 and 45 °C, even though K-CLEA retained full activity. The soluble keratinase was completely inactivated at 37 °C after storage in buffer solution (pH 7.4) for 2 months, meanwhile K-CLEAs kept 51% of their activity. K-CLEA loaded into polyvinyl alcohol (PVA) and PVA-P cryogels showed six times lower release rate compared to the soluble keratinase at skin pH (5.5). Small angle X-ray scattering (SAXS) analysis showed that K-CLEA bound to pectin rather than to PVA in the PVA-P matrix. PMID:24657614

  9. 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.

  10. Polymer Organic Light-Emitting Devices with Cathodes Transferred under Ambient Conditions

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Hyun; Liu, Yan-Peng; Jung, Eun; Seo, Seung-Woo; Chae, Heeyeop; Cho, Sung M.

    2011-11-01

    We fabricated polymer organic light-emitting devices (OLEDs) with an aluminum cathode transferred under ambient conditions from a separately prepared transfer film in order to achieve complete, vacuum-free fabrication of polymer OLEDs. Transfer of aluminum (Al) and lithium fluoride on aluminum (LiF/Al) onto polymer OLEDs as a cathode revealed problems in device performance due to native aluminum oxide and the stability of the LiF layer under ambient conditions, respectively. In contrast, the device fabricated with the transfer of cesium carbonate (Cs2CO3)-doped poly(vinyl alcohol) (PVA) on aluminum as a cathode showed lower turn-on voltage, and enhanced efficiency and stability. This method may provide an easy way to fabricate low-cost polymer OLEDs using complete, vacuum-free processes.

  11. An organic dye-polymer (phenol red-poly (vinyl alcohol)) composite architecture towards tunable -optical and -saturable absorption characteristics

    NASA Astrophysics Data System (ADS)

    Sreedhar, Sreeja; Illyaskutty, Navas; Sreedhanya, S.; Philip, Reji; Muneera, C. I.

    2016-05-01

    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.

  12. Electron beam crosslinked PEO and PEO/PVA hydrogels for wound dressing

    NASA Astrophysics Data System (ADS)

    Yoshii, F.; Zhanshan, Y.; Isobe, K.; Shinozaki, K.; Makuuchi, K.

    1999-06-01

    In order to prepare polyethylene oxide (PEO) hydrogel for wound dressing, different molecular weight PEO and PEO/poly(vinyl alcohol), PVA blend hydrogels were obtained with electron beam irradiation. Gel formation of PEO in aqueous solution was saturated at 40 kGy and the achieved gel fraction was 60-70%. The PEO hydrogel obtained was very fragile, hence PVA was added at 10-30% to give toughness to the PEO hydrogel. The PEO/PVA hydrogel blend showed satisfactory properties for wound dressing. To evaluate the healing effect of PEO/PVA hydrogel blend for dressing, the hydrogel covered a wound formed on the back of marmots. Healing under the wet environment of the hydrogel dressing had some advantages compared with that of gauze dressing which gives a dry environment: (1) the healing rate is faster, (2) easier to change the dressing, i.e. the hydrogel can be peeled off without any damage to the regenerated surface, and (3) no dressing material remains on the wound.

  13. Temperature-sensitive PVA/PNIPAAm semi-IPN hydrogels with enhanced responsive properties.

    PubMed

    Zhang, Jian-Tao; Bhat, Rahila; Jandt, Klaus D

    2009-01-01

    A series of temperature-sensitive hydrogels of semi-interpenetrating polymeric networks (semi-IPN) composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly(vinyl alcohol) (PVA) were prepared by radical polymerization. The PNIPAAm networks were cross-linked by N,N'-methylenebisacrylamide in the presence of linear PVA. The reaction processes were investigated by rheometry using oscillatory deformation tests. It was found that gelations were very fast and the modulus reached equilibrium within about 12.5min. The prepared semi-IPN hydrogels were characterized for their morphologies and thermal behaviors by scanning electron microscopy and differential scanning calorimetry, respectively. The interior network structures of the semi-IPN matrix became more porous with increasing PVA. In comparison to the conventional PNIPAAm gel, the newly reported semi-IPN hydrogels exhibited the same lower critical solution temperature. Their swelling properties, such as temperature dependence of equilibrium swelling ratio, shrinking kinetics and reswelling kinetics in water, were also studied. Experimental data indicated that the shrinking and reswelling rates of the semi-IPN hydrogels were much faster than those of the conventional PNIPAAm hydrogels. With this novel approach, water absorption and response properties could be adjusted by tuning the feed ratio of NIPAAm and PVA. These fast responsive hydrogels exhibited improved temperature sensitivity and swelling properties compared to the conventional PNIPAAm hydrogel, which would be critical and desirable for a gel to find potential applications in biomedical fields, such as drug delivery systems and sensors. PMID:18656431

  14. Synthesis, characterisation and antibacterial activity of PVA/TEOS/Ag-Np hybrid thin films.

    PubMed

    Bryaskova, Rayna; Pencheva, Daniela; Kale, Girish M; Lad, Umesh; Kantardjiev, T

    2010-09-01

    Novel hybrid material thin films based on polyvinyl alcohol (PVA)/tetraethyl orthosilicate (TEOS) with embedded silver nanoparticles (AgNps) were synthesized using sol-gel method. Two different strategies for the synthesis of silver nanoparticles in PVA/TEOS matrix were applied based on reduction of the silver ions by thermal annealing of the films or by preliminary preparation of silver nanoparticles using PVA as a reducing agent. The successful incorporation of silver nanoparticles ranging from 5 to 7nm in PVA/TEOS matrix was confirmed by TEM and EDX analysis, UV-Vis spectroscopy and XRD analysis. The antibacterial activity of the synthesized hybrid materials against etalon strains of three different groups of bacteria -Staphylococcus aureus (gram-positive bacteria), Escherichia coli (gram-negative bacteria), Pseudomonas aeruginosa (non-ferment gram-negative bacteria) has been studied as they are commonly found in hospital environment. The hybrid materials showed a strong bactericidal effect against E. coli, S. aureus and P. aeruginosa and therefore have potential applications in biotechnology and biomedical science. PMID:20557895

  15. Development and evaluation of polyvinyl-alcohol blend polymer films as battery separators

    NASA Technical Reports Server (NTRS)

    Manzo, M. A.

    1982-01-01

    Several dialdehydes and epoxies were evaluated for their suitability as cross-linkers. Optium concentrations of several cross-linking reagents were determined. A two-step method of cross-linking, which involves treatment of the film in an acid or acid periodate bath, was investigated and dropped in favor of a one-step method in which the acid catalyst, which initiates cross-linking, is added to the PVA - cross-linker solution before casting. The cross-linking was thus achieved during the drying step. This one-step method was much more adaptable to commercial processing. Cross-linked films were characterized as alkaline battery separators. Films were prepared in the lab and tested in cells in order to evaluate the effect of film composition and a number of processing parameters on cell performance. These tests were conducted in order to provide a broader data base from which to select optimum processing parameters. Results of the separator screening tests and the cell tests are discussed.

  16. Study of polyvinyl alcohol nanofibrous membrane by electrospinning as a magnetic nanoparticle delivery approach

    NASA Astrophysics Data System (ADS)

    Ger, Tzong-Rong; Huang, Hao-Ting; Huang, Chen-Yu; Hu, Keng-Shiang; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

    2014-05-01

    Electrospinning technique was used to fabricate polyvinyl alcohol (PVA)-based magnetic biodegradable nanofibers. PVA solution was mixed with ferrofluid or magnetic nanoparticles (MNPs) powder and formed two individual nanofibrous membranes (PVA/ferrofluid and PVA/MNPs powder) by electrospinning. The surface morphology of the nanofibrous membrane was characterized by scanning electron microscopy and the magnetic properties were measured by vibrating sample magnetometer. Macrophages (RAW 264.7) were co-cultured with the nanofibrous membranes for 12, 24, and 48 h and exhibited good cell viability (>95%). Results showed that the PVA fibers would be degraded and the embedded Fe3O4 nanoparticles would be released and delivered to cells.

  17. Determination of the water-soluble synthetic polymers polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone

    SciTech Connect

    Skripchuk, V.G.; Kozubovskii, A.I.

    1987-08-20

    The title polymers are used widely in drilling and displacement fluids in petroleum and natural gas recovery as well as flocculants for the purification of waste and drinking water. This paper collects, reviews, and provides a bibliography of the literature covering the last fifteen years dealing with analytical techniques for the determination of this polymers. Those techniques include optical methods such as photometry, spectrophotometry, and fluorimetry as well as chromatographic, thermal, and electrochemical methods.

  18. Enhanced photoluminescence of porous silicon nanoparticles coated by bioresorbable polymers

    NASA Astrophysics Data System (ADS)

    Gongalsky, Maxim B.; Kharin, Alexander Yu; Osminkina, Liubov A.; Timoshenko, Victor Yu; Jeong, Jinyoung; Lee, Han; Chung, Bong Hyun

    2012-08-01

    A significant enhancement of the photoluminescence (PL) efficiency is observed for aqueous suspensions of porous silicon nanoparticles (PSiNPs) coated by bioresorbable polymers, i.e., polylactic-co-glycolic acid (PLGA) and polyvinyl alcohol (PVA). PSiNPs with average size about 100 nm prepared by mechanical grinding of electrochemically etched porous silicon were dispersed in water to prepare the stable suspension. The inner hydrophobic PLGA layer prevents the PSiNPs from the dissolution in water, while the outer PVA layer makes the PSiNPs hydrophilic. The PL quantum yield of PLGA/PVA-coated PSiNPs was found to increase by three times for 2 weeks of the storage in water. The observed effect is explained by taking into account both suppression of the dissolution of PSiNPs in water and a process of the passivation of nonradiative defects in PSiNPs. The obtained results are interesting in view of the potential applications of PSiNPs in bioimaging.

  19. Fabrication of novel high performance ductile poly(lactic acid) nanofiber scaffold coated with poly(vinyl alcohol) for tissue engineering applications.

    PubMed

    Abdal-Hay, Abdalla; Hussein, Kamal Hany; Casettari, Luca; Khalil, Khalil Abdelrazek; Hamdy, Abdel Salam

    2016-03-01

    Poly(lactic acid) (PLA) nanofiber scaffold has received increasing interest as a promising material for potential application in the field of regenerative medicine. However, the low hydrophilicity and poor ductility restrict its practical application. Integration of hydrophilic elastic polymer onto the surface of the nanofiber scaffold may help to overcome the drawbacks of PLA material. Herein, we successfully optimized the parameters for in situ deposition of poly(vinyl alcohol), (PVA) onto post-electrospun PLA nanofibers using a simple hydrothermal approach. Our results showed that the average fiber diameter of coated nanofiber mat is about 1265±222 nm, which is remarkably higher than its pristine counterpart (650±180 nm). The hydrophilicity of PLA nanofiber scaffold coated with a PVA thin layer improved dramatically (36.11±1.5°) compared to that of pristine PLA (119.7±1.5°) scaffold. The mechanical testing showed that the PLA nanofiber scaffold could be converted from rigid to ductile with enhanced tensile strength, due to maximizing the hydrogen bond interaction during the heat treatment and in the presence of PVA. Cytocompatibility performance of the pristine and coated PLA fibers with PVA was observed through an in vitro experiment based on cell attachment and the MTT assay by EA.hy926 human endothelial cells. The cytocompatibility results showed that human cells induced more favorable attachment and proliferation behavior on hydrophilic PLA composite scaffold than that of pristine PLA. Hence, PVA coating resulted in an increase in initial human cell attachment and proliferation. We believe that the novel PVA-coated PLA nanofiber scaffold developed in this study, could be a promising high performance biomaterial in regeneration medicine. PMID:26706517

  20. Femtosecond laser microfabrication in polymers towards memory devices and microfluidic applications

    NASA Astrophysics Data System (ADS)

    Deepak, K. L. N.; Venugopal Rao, S.; Narayana Rao, D.

    2011-12-01

    We have investigated femtosecond laser induced microstructures, gratings, and craters in four different polymers: poly methyl methacrylate (PMMA), poly dimethyl siloxane (PDMS), polystyrene (PS) and poly vinyl alcohol (PVA) using Ti:sapphire laser delivering 800 nm, 100 femtosecond (fs) pulses at 1 kHz repetition rate with a maximum pulse energy of 1 mJ. Local chemical modifications leading to the formation of optical centers and peroxide radicals which were studied using UV-Visible absorption and emission, confocal micro-Raman and Electron Spin Resonance (ESR) spectroscopic techniques.

  1. Fabrication of superhydrophobic polymer films with hierarchical silver microbowl array structures.

    PubMed

    Xu, Miaojun; Lu, Nan; Qi, Dianpeng; Xu, Hongbo; Wang, Yandong; Shi, Shoulei; Chi, Lifeng

    2011-08-01

    Flexible superhydrophobic polyvinyl alcohol (PVA) films with silver bowl-like array structure are fabricated based on the thermal evaporation with sphere monolayer as templates and the modification of 1H, 1H, 2H, 2H-perfluorodecanethiol on silver surface. The silver microbowl arrays were composed of silver nanoparticles with an average diameter size of ca. 10 nm. The polymer films exhibit excellent stability and remarkable superhydrophobicity with a high water contact angle (CA) of about 163° and a low sliding angle (SA) of less than 3°. PMID:21549389

  2. Sequential design of a novel PVA-based crosslinked ethylenic homopolymer for extended drug delivery.

    PubMed

    Pillay, Viness; Sibanda, Wilbert; Danckwerts, Michael P

    2005-09-14

    A Box-Behnken Design was employed to study the influence of boric acid, sodium sulfate, ammonia and n-propanol in the formulation of crosslinked ethylenic homopolymeric (CEH) gelispheres from native polyvinyl alcohol (PVA). The dependent variables studied included the size of the spherical gelispheres, drug encapsulation efficiency, in vitro dissolution after 30 min and textural parameters, namely fracture force and matrix rupture energy. Based on these responses, an optimized CEH gelisphere matrix was formulated and thereafter incorporated as a powder into a candidate crosslinked zinc-pectinate multiple-unit device to assess its effect on modifying drug release. In the case of the CEH-loaded zinc-pectinate gelispheres, it was determined via constrained optimization that a maximum drug encapsulation efficiency of 28.63% could be obtained under the conditions of 0% (w/v) CEH, 13 h of crosslinking and drying temperature of 60 degrees C. On the other hand, initial drug release could be significantly retarded when 0.10% (w/v) of CEH was included in the formulation and crosslinked for 24 h at 40 degrees C. In this regard, CEH induced a 4 h lag phase. Furthermore, zero-order drug release was produced and could be maintained over several weeks. Kinetic analysis of drug release further supported that CEH inhibits polymer relaxation (k2

  3. Electrospinning of agar/PVA aqueous solutions and its relation with rheological properties.

    PubMed

    Sousa, Ana M M; Souza, Hiléia K S; Uknalis, Joseph; Liu, Shih-Chuan; Gonçalves, Maria P; Liu, LinShu

    2015-01-22

    In this work, we report the successful fabrication of agar-based nanofibers by electrospinning technique, using water as solvent media. A tubeless spinneret was attached inside the electrospinning chamber, operating at 50°C, to avoid agar gelation. Agar pure solution (1 wt%) showed inadequate spinnability regardless of the used electrospinning conditions. The addition of a co-blending polymer such as PVA (10 wt% starting solution) improved the solutions viscoelasticity and hence, the solutions spinnability. Agar/PVA solutions were prepared with different mass ratios (100/0, 50/50, 40/60, 30/70, 20/80 and 0/100) and electrospun at various sets of electrospinning conditions. Best nanofibers were obtained with 30/70 and 20/80 agar/PVA blends while samples with higher agar contents (50/50 and 40/60 agar/PVA) were harder to process and led to discontinuous fibrous mats. This first set of encouraging results can open a new window of opportunities for agar-based biomaterials in the form of nanofibers. PMID:25439904

  4. ZnO-PVA nanocomposite films for low threshold optical limiting applications

    NASA Astrophysics Data System (ADS)

    Viswanath, Varsha; Beenakumari, C.; Muneera, C. I.

    2014-10-01

    Zinc oxide-PVA nanocomposite films were fabricated adopting a simple method based on solution-casting, incorporating small weight percentages (<1.2 wt%) of ZnO in PVA (˜0.625×10-3M to 7×10-3M), and their structure, morphology, linear and low threshold nonlinear optical properties were investigated. The films were characterized as nanostructured ZnO encapsulated between the molecules/chains of the semicrystalline host polymer PVA. The samples exhibited low threshold nonlinear absorption and negative nonlinear refraction, as studied using the Z-scan technique. A switchover from SA to RSA was observed as the concentration of ZnO was increased. The optical limiting of 632.8 nm CW laser light displayed by these nanocomposite films is also demonstrated. The estimated values of the effective coefficients of nonlinear absorption, nonlinear refraction and third-order nonlinear susceptibility, |χ(3)|, compared to those reported for continuous wave laser light excitation, measure up to the highest among them. The results show that the ZnO-PVA nanocomposite films have great potential applications in future optical and photonic devices.

  5. ZnO-PVA nanocomposite films for low threshold optical limiting applications

    SciTech Connect

    Viswanath, Varsha; Beenakumari, C.; Muneera, C. I.

    2014-10-15

    Zinc oxide-PVA nanocomposite films were fabricated adopting a simple method based on solution-casting, incorporating small weight percentages (<1.2 wt%) of ZnO in PVA (∼0.625×10{sup −3}M to 7×10{sup −3}M), and their structure, morphology, linear and low threshold nonlinear optical properties were investigated. The films were characterized as nanostructured ZnO encapsulated between the molecules/chains of the semicrystalline host polymer PVA. The samples exhibited low threshold nonlinear absorption and negative nonlinear refraction, as studied using the Z-scan technique. A switchover from SA to RSA was observed as the concentration of ZnO was increased. The optical limiting of 632.8 nm CW laser light displayed by these nanocomposite films is also demonstrated. The estimated values of the effective coefficients of nonlinear absorption, nonlinear refraction and third-order nonlinear susceptibility, |χ{sup (3)}|, compared to those reported for continuous wave laser light excitation, measure up to the highest among them. The results show that the ZnO-PVA nanocomposite films have great potential applications in future optical and photonic devices.

  6. Nano-anisotropic surface coating based on drug immobilized pendant polymer to suppress macrophage adhesion response.

    PubMed

    Kaladhar, K; Renz, H; Sharma, C P

    2015-04-01

    Exploring drug molecules for material design, to harness concepts of nano-anisotropy and ligand-receptor interactions, are rather elusive. The aim of this study is to demonstrate the bottom-up design of a single-step and bio-interactive polymeric surface coating, based on drug based pendant polymer. This can be applied on to polystyrene (PS) substrates, to suppress macrophage adhesion and spreading. The drug molecule is used in this coating for two purposes. The first one is drug as a "pendant" group, to produce nano-anisotropic properties that can enable adhesion of the coatings to the substrate. The second purpose is to use the drug as a "ligand", to produce ligand-receptor interaction, between the bound ligand and receptors of albumin, to develop a self-albumin coat over the surface, by the preferential binding of albumin in biological environment, to reduce macrophage adhesion. Our in silico studies show that, diclofenac (DIC) is an ideal drug based "ligand" for albumin. This can also act as a "pendant" group with planar aryl groups. The combination of these two factors can help to harness, both nano-anisotropic properties and biological functions to the polymeric coating. Further, the drug, diclofenac (DIC) is immobilized to the polyvinyl alcohol (PVA), to develop the pendant polymer (PVA-DIC). The interaction of bound DIC with the albumin is a ligand-receptor based interaction, as per the studies by circular dichroism, differential scanning calorimetry, and SDS-PAGE. The non-polar π-π* interactions are regulating; the interactions between PVA bound DIC-DIC interactions, leading to "nano-anisotropic condensation" to form distinct "nano-anisotropic segments" inside the polymeric coating. This is evident from, the thermo-responsiveness and uniform size of nanoparticles, as well as regular roughness in the surface coating, with similar properties as that of nanoparticles. In addition, the hydrophobic DIC-polystyrene (PS) interactions, between the PVA

  7. Fabrication, biocompatibility, and tissue engineering substrate analysis of polyvinyl alcohol-gelatin core-shell electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Merkle, Valerie Marie

    Cardiovascular disease is the leading cause of death in the United States with approximately 49% of the cardiovascular related deaths attributed to coronary heart disease (CHD). CHD is the accumulation of plaque resulting in the narrowing of the vessel lumen and a decrease in blood flow to the downstream heart muscle. In order to restore blood flow, arterial by-pass procedures can be undertaken. However, the patient's own arteries/veins may not be suitable for use as a vessel replacement, and synthetic grafts lack the compliancy and durability needed for these small diameter locations (< 5 mm). Therefore, the goal of this research is to develop a nanofibrous material that can be used in vascular applications such as this. In this study, we fabricate coaxial electrospun nanofibers with gelatin in the shell and polyvinyl alcohol (PVA) in the core using 1 Gelatin: 1 PVA and 3 Gelatin: 1 PVA mass ratios. Gelatin, derived from collagen, is highly bioactive while PVA, a synthetic polymer, has appealing mechanical properties. Therefore, by combining these materials in a core-shell structure, we hypothesize that the resulting nanofibers will have enhanced mechanical properties, cellular growth and migration, as well as minimal platelet deposition and activation compared to scaffolds composed solely of gelatin or PVA. First, the coaxial scaffolds exhibited an enhanced Young's modulus and ultimate strength compared to scaffolds composed of PVA or gelatin alone. Endothelial cells had high proliferation and migration on the coaxial electrospun scaffolds with higher migration seen on the stiffer, coaxial scaffolds. The smooth muscle cells had less proliferation and lower migration rates on the coaxial scaffolds than the endothelial cells. Using a modified prothrombinase assay, the coaxial scaffolds had minimal platelet activation. Lastly, when pre-seeding the coaxial scaffolds with endothelial cells or smooth muscle cells, the platelet deposition decreased in comparison to

  8. Polymers All Around You!

    ERIC Educational Resources Information Center

    Gertz, Susan

    Background information on natural polymers, synthetic polymers, and the properties of polymers is presented as an introduction to this curriculum guide. Details are provided on the use of polymer products in consumer goods, polymer recycling, polymer densities, the making of a polymer such as GLUEP, polyvinyl alcohol, dissolving plastics, polymers…

  9. Effect of interfibrillar PVA bridging on water stability and mechanical properties of TEMPO/NaClO2 oxidized cellulosic nanofibril films.

    PubMed

    Hakalahti, Minna; Salminen, Arto; Seppälä, Jukka; Tammelin, Tekla; Hänninen, Tuomas

    2015-08-01

    TEMPO/NaClO2 oxidized cellulosic nanofibrils (TCNF) were covalently bonded with poly(vinyl alcohol) (PVA) to render water stable films. Pure TCNF films and TCNF-PVA films in dry state showed similar humidity dependent behavior in the elastic region. However, in wet films PVA had a significant effect on stability and mechanical characteristics of the films. When soaked in water, pure TCNF films exhibited strong swelling behavior and poor wet strength, whereas covalently bridged TCNF-PVA composite films remained intact and could easily be handled even after 24h of soaking. Wet tensile strength of the films was considerably enhanced with only 10 wt% PVA addition. At 25% PVA concentration wet tensile strengths were decreased and films were more yielding. This behavior is attributed to the ability of PVA to reinforce and plasticize TCNF-based films. The developed approach is a simple and straightforward method to produce TCNF films that are stable in wet conditions. PMID:25933525

  10. Thermal and transport properties of the polymer electrolyte based on poly(vinyl alcohol)-LiOH-H2O

    NASA Astrophysics Data System (ADS)

    Fernández, M. E.; Delgado, I.; Diosa, J. E.; Vargas, R. A.

    2005-08-01

    Alkaline solid electrolyte membranes, based on the poly(vinyl alcohol) (PVAL), lithium hydroxide (LiOH) and water with various salt concentrations have been synthesized. These systems have anhydridous ionic conductivity () as high as 2,9 × 10-4 Scm-1 at room temperature and show a linear dependence of ln() with 1/T below 80 °C. The thermal analysis indicated three transformations in the blends: at 205, 150 and -125 °C, associated with decompositions, melting point and glass transition of the polymer blends, respectively. The X-ray spectra for the samples at room temperature show a peak at about 2 = 20° for all salt concentrations and whose intensity depends on the amorphous character of the system. The results are discussed in terms of the high mobility of the Li+ ions in the amorphous phase of the complex.

  11. EXPLORING THE BIOTRANSFORMATION POTENTIAL OF FLUOROTELOMER ALCOHOL-BASED POLYMER FORMULATIONS DURING AEROBIC BIOLOGICAL WASTEWATER TREATMENT

    EPA Science Inventory

    Fluorotelomer alcohols have been widely used over the past 50 years in surface protection products for paper, packaging, textile, and carpet goods; in industrial surfactant mixtures; in aqueous fire-fighting foams, and as processing aids during the production of fluoropolymer pla...

  12. Role of single-walled carbon nanotubes on ester hydrolysis and topography of electrospun bovine serum albumin/poly(vinyl alcohol) membranes.

    PubMed

    Ford, Ericka N J; Suthiwangcharoen, Nisaraporn; D'Angelo, Paola A; Nagarajan, Ramanathan

    2014-07-23

    Electrospun membranes were studied for the chemical deactivation of threat agents by means of enzymatic proteins. Protein loading and the surface chemistry of hybrid nanofibers influenced the efficacy by which embedded enzymes could digest the substrate of interest. Bovine serum albumin (BSA), selected as a model protein, was electrospun into biologically active fibers of poly(vinyl alcohol), PVA. Single-walled carbon nanotubes (SWNTs) were blended within these mixtures to promote protein assembly during the process of electrospinning and subsequently the ester hydrolysis of the substrates. The SWNT incorporation was shown to influence the topography of PVA/BSA nanofibers and enzymatic activity against paraoxon, a simulant for organophosphate agents and a phosphorus analogue of p-nitrophenyl acetate (PNA). The esterase activity of BSA against PNA was uncompromised upon its inclusion within nanofibrous membranes because similar amounts of PNA were hydrolyzed by BSA in solution and the electrospun BSA. However, the availability of BSA along the fiber surface was shown to affect the ester hydrolysis of paraoxon. Atomic force microscopy images of nanofibers implicated the surface migration of BSA during the electrospinning of SWNT filled dispersions, especially as greater weight fractions of protein were added to the spinning mixtures. In turn, the PVA/SWNT/BSA nanofibers outperformed the nanotube free PVA/BSA membranes in terms of paraoxon digestion. The results support the development of electrospun polymer nanofiber platforms, modulated by SWNTs for enzyme catalytic applications relevant to soldier protective ensembles. PMID:25007411

  13. Polypyrrole/poly(vinyl alcohol-co-ethylene) quasi-solid gel electrolyte for iodine-free dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Jung, Mi-Hee

    2014-12-01

    Conducting polymer gel electrolyte is synthesized using the Cl- doped polypyrrole (PPy)/1-buty-2,3-dimethylimidazolium iodide (BDI)/poly(vinyl alcohol-co-ethylene)(PVA-EL), which yield an overall energy-conversion efficiency of about 4.72% comparable to the liquid electrolyte 4.69% under irradiation at 100 mW cm-2 AM 1.5. The introduction of PPy and PVA-EL into the BDI (which dissolves in the dimethylsulfoxide) increases the ion conductivity and effectively decreases the charge transfer resistance in the PPy gel electrolyte/TiO2/dye interfaces. With the change of the PVA-EL composition, PPy gel electrolyte exhibits independence of the content of PVA-EL, which means ion conductivity of PPy gel electrolyte as a dominant role for the contribution of cell performance. Employing intensity-modulated photo-voltage spectroscopy, intensity-modulated photo-current spectroscopy, and charge-extraction measurement, it demonstrate that the effective charge collection in PPy gel electrolyte devices rather than liquid electrolyte one is occurred due to the larger diffusion coefficient and long electron lifetime, resulting in the higher-efficiency solar cell.

  14. Poly(vinyl alcohol)-Poly(ethylene glycol) Double-Network Hydrogel: A General Approach to Shape Memory and Self-Healing Functionalities.

    PubMed

    Li, Guo; Zhang, Hongji; Fortin, Daniel; Xia, Hesheng; Zhao, Yue

    2015-10-27

    A double-network polymer hydrogel composed of chemically cross-linked poly(ethylene glycol) (PEG) and physically cross-linked poly(vinyl alcohol) (PVA) was prepared. When the hydrogel (70 wt % of water) is subjected to freezing/thawing treatment under strain, the enhanced physical network as a result of crystallization of PVA chains can stabilize the hydrogel deformation after removal of the external force at room temperature. Subsequent disruption of the physical network of PVA by heating allows for the recovery of the initial shape of the hydrogel. Moreover, the double-network hydrogel exhibits self-healing capability stemming from the physical network of PVA by virtue of the extensive interchain hydrogen bonding between the hydroxyl side groups. This study thus demonstrates a general approach to imparting both the shape memory and self-healing properties to chemically cross-linked hydrogels that otherwise do not have such functionalities. Moreover, by making use of the fixed hydrogel elongation, the effect of anisotropy arising from chain orientation on the self-healing was also observed. PMID:26442631

  15. Uniaxial Drawing of Graphene-PVA Nanocomposites: Improvement in Mechanical Characteristics via Strain-Induced Exfoliation of Graphene.

    PubMed

    Jan, Rahim; Habib, Amir; Akram, Muhammad Aftab; Zia, Tanveer-Ul-Haq; Khan, Ahmad Nawaz

    2016-12-01

    Polyvinyl alcohol (PVA)-stabilized graphene nanosheets (GNS) of lateral dimension (L) ~1 μm are obtained via liquid phase exfoliation technique to prepare its composites in the PVA matrix. These composites show low levels of reinforcements due to poor alignment of GNS within the matrix as predicted by the modified Halpin-Tsai model. Drawing these composites up to 200 % strain, a significant improvement in mechanical properties is observed. Maximum values for Young's modulus and strength are ~×4 and ~×2 higher respectively than that of neat PVA. Moreover, the rate of increase of the modulus with GNS volume fraction is up to 700 GPa, higher than the values predicted using the Halpin-Tsai theory. However, alignment along with strain-induced de-aggregation of GNS within composites accounts well for the obtained results as confirmed by X-ray diffraction (XRD) characterization. PMID:27558496

  16. Structure and rheology of semisolid o/w creams containing cetyl alcohol/non-ionic surfactant mixed emulsifier and different polymers.

    PubMed

    Ribeiro, H M; Morais, J A; Eccleston, G M

    2004-04-01

    Oil-in-water (o/w) emulsions for cosmetic use, such as lotions and creams, are complex multiple-phase systems, which may contain a number of interacting surfactants, fatty amphiphiles, polymers and other excipients. This study investigates the influence of two synthetic cationic polymers, Polyquaternium-7 and Polyquaternium-11, and the natural anionic polymer, gum of acacia, on the rheology and microstructure of creams prepared with a non-ionic mixed emulsifier (cetyl stearyl alcohol-12EO/cetyl alcohol) using rheology (continuous shear, and viscoelastic creep and oscillation), microscopy and differential scanning calorimetry (DSC). A control cream containing no polymer was also investigated. The semisolid control cream was structured by a swollen lamellar gel network phase formed from the interaction of cetyl alcohol and the POE surfactant, in excess of that required to stabilize oil droplets, with continuous phase water. Endothermic transitions between 25 and 100 degrees C were identified as components of this phase. Incorporation of cationic polymer into the formulation caused significant loss of structure to produce a mobile semisolid containing larger oil droplets. The microscopical and thermal data implied that the cationic polymer caused the swollen lamellar gel network phase to transform into non-swollen crystals of cetyl alcohol. In contrast, incorporation of gum of acacia produced a thicker cream than the control, with smaller droplet sizes and little evidence of the gel network. Microscopical and thermal data implied that although there were also interactions between gum of acacia and both the surfactant and the swollen gel network phase, the semisolid properties were probably because of the ability of the gum of acacia to stabilize and thicken the emulsion in the absence of the swollen lamellar network. PMID:18494913

  17. Effect of hydroxypropyl-β-cyclodextrin and coadjuvants on the sorption capacity of hydrophilic polymer films for monoterpene alcohols.

    PubMed

    Higueras, Laura; López-Carballo, Gracia; Gavara, Rafael; Hernández-Muñoz, Pilar

    2016-10-20

    Chitosan films filled with hydroxypropyl-β-cyclodextrin at a 1:1 weight ratio and plasticized with 35 or 50% glycerol or 35% propylene glycol were prepared by casting and conditioned at different relative humidities to achieve a similar water content. Sorption properties of the films for various monoterpene compounds with phenolic, or with linear or cyclohexyl alcohol structures were studied after their immersion in the volatile liquids. In general, the films presented a considerable capacity to retain monophenolic compounds, with sorption values ranging from 455% for meta-cumenol to 193% for guaiacol, for chitosan films with the same formulation. These values were two orders of magnitude higher than those of compounds without the phenol group. The affinity for monophenolic compounds decreased in films plasticized with hydrophilic propylene glycol, whereas no changes were observed in the retention of non-phenolic monoterpenes. Replacement of chitosan with polyvinyl alcohol polymer considerably decreased the retention of monophenolic compounds, with the exception of isoeugenol. Finally, the antimicrobial activity of monoterpenes and films loaded with them was evaluated in vitro by the microatmosphere test against Escherichia coli and Staphylococcus aureus. The present study shows that hydroxypropyl-β-cyclodextrin and the plasticization level achieved by hydrophilic films can be used to regulate loading capacity and sorption selectivity of naturally occurring antimicrobial compounds. PMID:27474670

  18. Silk Nanospheres and Microspheres from Silk/PVA Blend Films for Drug Delivery

    PubMed Central

    Wang, Xiaoqin; Yucel, Tuna; Lu, Qiang; Hu, Xiao; Kaplan, David L.

    2009-01-01

    Silk fibroin protein-based micro- and nanospheres provide new options for drug delivery due to their biocompatibility, biodegradability and their tunable drug loading and release properties. In the present study, we report a new aqueous-based preparation method for silk spheres with controllable sphere size and shape. The preparation was based on phase separation between silk fibroin and polyvinyl alcohol (PVA) at a weight ratio of 1/1 and 1/4. Water-insoluble silk spheres were easily obtained from the blend in a three step process: (1) air-drying the blend solution into a film, (2) film dissolution in water and (3) removal of residual PVA by subsequent centrifugation. In both cases, the spheres had approximately 30% beta-sheet content and less than 5% residual PVA. Spindle-shaped silk particles, as opposed to the spherical particles formed above, were obtained by stretching the blend films before dissolving in water. Compared to the 1/1 ratio sample, the silk spheres prepared from the 1/4 ratio sample showed a more homogeneous size distribution ranging from 300 nm up to 20 μm. Further studies showed that sphere size and polydispersity could be controlled either by changing the concentration of silk and PVA or by applying ultrasonication on the blend solution. Drug loading was achieved by mixing model drugs in the original silk solution. The distribution and loading efficiency of the drug molecules in silk spheres depended on their hydrophobicity and charge, resulting in different drug release profiles. The entire fabrication procedure could be completed within one day. The only chemical used in the preparation except water was PVA, an FDA-approved ingredient in drug formulations. Silk micro- and nanospheres reported have potential as drug delivery carriers in a variety of biomedical applications. PMID:19945157

  19. Use of Polyvinyl Alcohol as a Solubility-Enhancing Polymer for Poorly Water Soluble Drug Delivery (Part 1).

    PubMed

    Brough, Chris; Miller, Dave A; Keen, Justin M; Kucera, Shawn A; Lubda, Dieter; Williams, Robert O

    2016-02-01

    Polyvinyl alcohol (PVAL) has not been investigated in a binary formulation as a concentration-enhancing polymer owing to its high melting point/high viscosity and poor organic solubility. Due to the unique attributes of the KinetiSol® dispersing (KSD) technology, PVAL has been enabled for this application and it is the aim of this paper to investigate various grades for improvement of the solubility and bioavailability of poorly water soluble active pharmaceutical ingredients. Solid amorphous dispersions were created with the model drug, itraconazole (ITZ), at a selected drug loading of 20%. Polymer grades were chosen with variation in molecular weight and degree of hydroxylation to determine the effects on performance. Differential scanning calorimetry, powder X-ray diffraction, polarized light microscopy, size exclusion chromatography, and dissolution testing were used to characterize the amorphous dispersions. An in vivo pharmacokinetic study in rats was also conducted to compare the selected formulation to current market formulations of ITZ. The 4-88 grade of PVAL was determined to be effective at enhancing solubility and bioavailability of itraconazole. PMID:26637232

  20. Gel spinning of PVA composite fibers with high content of multi-walled carbon nanotubes and graphene oxide hybrids

    NASA Astrophysics Data System (ADS)

    Wei, Yizhe; Lai, Dengpan; Zou, Liming; Ling, Xinlong; Lu, Hongwei; Xu, Yongjing

    2015-07-01

    In this report, poly (vinyl alcohol) (PVA) composite fibers with high content of multi-walled carbon nanotubes and graphene oxide (MWCNTs-GO) hybrids were prepared by gel spinning, and were characterized by TGA, DSC, SEM, XL-2 yarn strength tester and electrical conductivity measurement. The total content of MWCNTs-GO hybrids in the PVA composite fibers, which is up to 25 wt%, was confirmed by TGA analysis. The DSC measurement shows that the melting and crystallization peaks decreased after the addition of nano-fillers. This is due to the reason that the motion of PVA chains is completely confined by strong hydrogen bonding interaction between PVA and nano-fillers. After the addtion of GO, the dispersibility of MWCNTs in composite fibers improved slightly. And the tensile strength and Young's modulus increased by 38% and 67%, respectively. This is caused by the increased hydrogen bonding interaction and synergistic effect through hybridization of MWCNTs and GO. More significantly, the electrical conductivity of PVA/MWCNTs/GO composite fibers enhanced by three orders of magnitude with the addition of GO.

  1. Ternary PVA nanocomposites containing cellulose nanocrystals from different sources and silver particles: part II.

    PubMed

    Fortunati, E; Luzi, F; Puglia, D; Terenzi, A; Vercellino, M; Visai, L; Santulli, C; Torre, L; Kenny, J M

    2013-09-12

    Cellulose nanocrystals (CNC) extracted from three different sources, namely flax, phormium, and commercial microcrystalline cellulose (MCC) have been used in a polyvinyl alcohol (PVA) matrix to produce anti-bacterial films using two different amounts of silver nanoparticles (0.1 wt% and 0.5 wt%). In general, CNC confer an effect of reinforcement to PVA film, the best values of stiffness being offered by composites produced using phormium fibres, whilst for strength those produced using flax are slightly superior. This was obtained without inducing any particular modification in transition temperatures and in the thermal degradation patterns. As regards antibacterial properties, systems with CNC from flax proved slightly better than those with CNC from phormium and substantially better than those including commercial MCC. Dynamic mechanical thermal analysis (DMTA) has only been performed on the ternary composite containing 0.1 wt% Ag, which yielded higher values of Young's modulus, and as a whole confirmed the above results. PMID:23911522

  2. In Vitro Sustained Release Study of Gallic Acid Coated with Magnetite-PEG and Magnetite-PVA for Drug Delivery System

    PubMed Central

    Kura, Aminu Umar; Hussein-Al-Ali, Samer Hasan; Bin Hussein, Mohd Zobir; Fakurazi, Sharida; Shaari, Abdul Halim; Ahmad, Zalinah

    2014-01-01

    The efficacy of two nanocarriers polyethylene glycol and polyvinyl alcohol magnetic nanoparticles coated with gallic acid (GA) was accomplished via X-ray diffraction, infrared spectroscopy, magnetic measurements, thermal analysis, and TEM. X-ray diffraction and TEM results showed that Fe3O4 nanoparticles were pure iron oxide having spherical shape with the average diameter of 9 nm, compared with 31 nm and 35 nm after coating with polyethylene glycol-GA (FPEGG) and polyvinyl alcohol-GA (FPVAG), respectively. Thermogravimetric analyses proved that after coating the thermal stability was markedly enhanced. Magnetic measurements and Fourier transform infrared (FTIR) revealed that superparamagnetic iron oxide nanoparticles could be successfully coated with two polymers (PEG and PVA) and gallic acid as an active drug. Release behavior of gallic acid from two nanocomposites showed that FPEGG and FPVAG nanocomposites were found to be sustained and governed by pseudo-second-order kinetics. Anticancer activity of the two nanocomposites shows that the FPEGG demonstrated higher anticancer effect on the breast cancer cell lines in almost all concentrations tested compared to FPVAG. PMID:24737969

  3. Selective transport of Fe(III) using ionic imprinted polymer (IIP) membrane particle

    NASA Astrophysics Data System (ADS)

    Djunaidi, Muhammad Cholid; Jumina, Siswanta, Dwi; Ulbricht, Mathias

    2015-12-01

    The membrane particles was prepared from polyvinyl alcohol (PVA) and polymer IIP with weight ratios of 1: 2 and 1: 1 using different adsorbent templates and casting thickness. The permeability of membrane towards Fe(III) and also mecanism of transport were studied. The selectivity of the membrane for Fe(III) was studied by performing adsorption experiments also with Cr(III) separately. In this study, the preparation of Ionic Imprinted Polymer (IIP) membrane particles for selective transport of Fe (III) had been done using polyeugenol as functional polymer. Polyeugenol was then imprinted with Fe (III) and then crosslinked with PEGDE under alkaline condition to produce polyeugenol-Fe-PEGDE polymer aggregates. The agrregates was then crushed and sieved using mesh size of 80 and the powder was then used to prepare the membrane particles by mixing it with PVA (Mr 125,000) solution in 1-Methyl-2-pyrrolidone (NMP) solvent. The membrane was obtained after casting at a speed of 25 m/s and soaking in NaOH solution overnight. The membrane sheet was then cut and Fe(III) was removed by acid to produce IIP membrane particles. Analysis of the membrane and its constituent was done by XRD, SEM and size selectivity test. Experimental results showed the transport of Fe(III) was faster with the decrease of membrane thickness, while the higher concentration of template ion correlates with higher Fe(III) being transported. However, the transport of Fe(III) was slower for higher concentration of PVA in the membrane. IImparticles works through retarded permeation mechanism, where Fe(III) was bind to the active side of IIP. The active side of IIP membrane was dominated by the -OH groups. The selectivity of all IIP membranes was confirmed as they were all unable to transport Cr (III), while NIP (Non-imprinted Polymer) membrane was able transport Cr (III).

  4. Multifunctional electroactive electrospun nanofiber structures from water solution blends of PVA/ODA–MMT and poly(maleic acid-alt-acrylic acid): effects of Ag, organoclay, structural rearrangement and NaOH doping factors

    NASA Astrophysics Data System (ADS)

    Şimşek, Murat; Rzayev, Zakir M. O.; Bunyatova, Ulviya

    2016-06-01

    Novel multifunctional colloidal polymer nanofiber electrolytes were fabricated by green reactive electrospinning nanotechnology from various water solution/dispersed blends of poly (vinyl alcohol-co-vinyl acetate) (PVA)/octadecyl amine-montmorillonite (ODA–MMT) as matrix polymer nanocomposite and poly(maleic acid-alt-acrylic acid) (poly(MAc-alt-AA) and/or its Ag-carrying complex as partner copolymers. Polymer nanofiber electrolytes were characterized using FTIR, XRD, thermal (DSC, TGA–DTG), SEM, and electrical analysis methods. Effects of partner copolymers, organoclay, in situ generated silver nanoparticles (AgNPs), and annealing procedure on physical and chemical properties of polymer composite nanofibers were investigated. The electrical properties (resistance, conductivity, activation energy) of nanofibers with/without NaOH doping agent were also evaluated. This work presented a structural rearrangement of nanofiber mats by annealing via decarboxylation of anhydride units with the formation of new conjugated double bond sites onto partner copolymer main chains. It was also found that the semiconductor behaviors of nanofiber structures were essentially improved with increasing temperature and fraction of partner copolymers as well as presence of organoclay and AgNPs in nanofiber composite.

  5. Copper-containing polyvinyl alcohol composite systems: Preparation, characterization and biological activity

    NASA Astrophysics Data System (ADS)

    Reza Hajipour, Abdol; Mohammadsaleh, Fatemeh; Reza Sabzalian, Mohammad

    2015-08-01

    The present investigation reports, the complex formation of Cu(II) with polyvinyl alcohol (PVA) and the synthesis of PVA-stabilized Cu2O particles. This PVA-Cu2O composite has been prepared via chemical reduction method using PVA-Cu(II) complex as precursor. At first, Cu(II) ions were stabilized in PVA matrix via complex formation with OH groups; subsequently, this PVA-Cu(II) macromolecular complex as precursor reacted with ascorbic acid as reducing agent at pH=12 to prepare PVA-Cu2O composite. The products were characterized by FTIR, XRD, FE-SEM, HRTEM, Visible Spectroscopy and atomic absorption. In the following, the antibacterial properties of as-prepared composites were examined against Gram-positive (Bacillus thuringiensis) and Gram-negative bacteria (Escherichia coli), and the results showed excellent antibacterial activity of these materials.

  6. Biodegradation of polyvinyl alcohol by a brown-rot fungus, Fomitopsis pinicola.

    PubMed

    Tsujiyama, S; Okada, A

    2013-11-01

    A brown-rot fungus, Fomitopsis pinicola, degraded polyvinyl alcohol (PVA) in quartz sand but not in liquid culture. From gel permeation chromatography analysis, the high-molecular-weight fraction of PVA was decreased by the action of F. pinicola but the coloration of the culture filtrate with I2 solution increased. The reason for the increase in coloration was assumed to be the increase in the low-molecular-weight fraction in degraded PVA. Diffuse reflectance infrared Fourier transform spectral analysis showed that spectral changes of the fungally degraded PVA were similar to those of PVA treated with Fenton's reagent suggesting that PVA degradation by F. pinicola was via the Fenton reaction. F. pinicola can thus be used to degrade PVA in woody wastes. PMID:23881320

  7. 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.

  8. 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.

  9. 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.

  10. Thermal effects on the electrical properties of (methyl orange)/ (polyvinyl alcohol) composites

    NASA Astrophysics Data System (ADS)

    de Oliveira, Helinando P.; de Melo, Celso P.

    2007-04-01

    We have used electrical impedance spectroscopy to determine the dielectric characteristics of polymeric films prepared by incorporating varying amounts of methyl orange (MO), an azobenzene dye, into solid films of polyvinyl alcohol (PVA), an insulating polymer. By mapping the variation of relevant parameters such as the dielectric relaxation time, we have analyzed how thermal effects would affect the charge transport and polarization processes in the MO/PVA composite samples as the frequency of an applied external field and the temperature were varied in a controlled manner. We interpret the results in terms of number and size of the dye aggregates in the polymeric matrix, by correlating thermal and polarization effects to the temperature and the relative amount of MO in the composite films. Finally, we show that the electrical characteristics of the MO/PVA samples can be modified by light incidence, a fact that confirms the possibility of using these composites in (light written)-(electrically read) solid-state memory devices.

  11. Antimicrobial activity of poly(vinyl alcohol)-poly(acrylic acid) electrospun nanofibers.

    PubMed

    Santiago-Morales, Javier; Amariei, Georgiana; Letón, Pedro; Rosal, Roberto

    2016-10-01

    Electrospun nanofibers were prepared from blends of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA). The fibers were stabilized by heat curing at 140°C via anhydride and ketone formation and crosslinking esterification. The antimicrobial effect was assessed using strains of Escherichia coli and Staphylococcus aureus by tracking their capacity to form colonies and their metabolic impairment upon contact with PAA/PVA membranes. Membranes containing >35wt.% PAA displayed significant antibacterial activity, which was particularly high for the gram-positive S. aureus. All membranes were negatively charged, with surface ζ-potential in the (-34.5)-(-45.6)mV range, but the electrostatic interaction with the negatively charged cells was not the reason for the antimicrobial effect. Neither pH reduction nor the passing of non-crosslinked polymers to the solution affected microbial growth. The antibacterial activity was attributed to the chelation of the divalent cations stabilizing the outer cell membrane. The effect on gram-positive bacteria was attributed to the destabilization of the peptidoglycan layer. The sequestration of divalent cations was demonstrated with experiments in which calcium and a chelating agent were added to the cultures in contact with membranes. The damage to bacterial cells was tracked by measuring their surface charge and the evolution of intracellular calcium during the early stages after contact with PAA/PVA membranes. PMID:27318959

  12. PIV measurements of flow in drying polymer solutions during solvent casting

    NASA Astrophysics Data System (ADS)

    Mansoor, Iman; Stoeber, Boris

    2011-05-01

    An experimental method based on confocal microscopy and particle image velocimetry (PIV) is used to characterize the flow in a polymer solution during solvent casting. The flow inside a 200-μm-thick film of a poly(vinyl alcohol) (PVA) solution is visualized near a vertical wall of a mold using confocal microscopy of seed particles during solvent evaporation at 25, 35, and 45°C, and the corresponding velocity vector fields are determined from projections of the confocal images. Flow toward the vertical wall is observed inside the film as well as a slower Marangoni-type counter flow at the film surface during the initial phase of solvent evaporation, resulting from a polymer concentration gradient along the film due to a local variation in evaporation rate. Total volume of the polymer solution in the observation volume as well as solvent evaporation rate are determined as a function of time, both revealing close correlation to average horizontal velocity data from PIV. The PIV measurements show significant differences in the flow velocity fields at different temperatures. The PIV measurements correlate with the solvent evaporation rates as well as the final polymer thicknesses on the vertical wall of the mold. Surface tension and viscosity measurements are taken for different concentrations of PVA solution.

  13. Polymer Assisted Core-shell Ag-C nanoparticles Synthesis via Green hydrothermal Technique

    NASA Astrophysics Data System (ADS)

    Williams, James; Mishra, Sanjay

    2009-03-01

    Core-Shell Ag-C nanoparticles were synthesized in the presence of glucose through a one-pot green hydrothermal wet chemical process. An aqueous solution of glucose and Ag nitrate was hydrothermally treated to produce porous carbonaceous shell over silver core nanoparticles. The growth of carbon shells was regulated by either of the polymers (poly) vinyl pyrrolidone (PVP) or poly vinyl alcohol (PVA). The two polymers were compared to take a measure of different tunable sizes of cores, and shells. The effects of hydrothermal temperature, time, and concentration of reagents on the final formation of nanostructures were studied using UV-vis extinction spectra, transmission electron microscope, and Raman spectroscopy. The polymer molecules were found to be incorporated into carbonaceous shell. The resulting opacity of the shell was found to be hydrothermal time and temperature dependent. The shell structure was found to be more uniform with PVP than PVA. Furthermore, the polymer concentration was found to influence size and shape of the core-silver particles as well. The core-shelled nanoparticles have surfaces with organic groups capable of assembling with different reagents that could be useful in drug-delivery, optical nanodevices or biochemistry.

  14. Magnetic Properties of Polyvinyl Alcohol and Doxorubicine Loaded Iron Oxide Nanoparticles for Anticancer Drug Delivery Applications

    PubMed Central

    Nadeem, Muhammad; Ahmad, Munir; Akhtar, Muhammad Saeed; Shaari, Amiruddin; Riaz, Saira; Naseem, Shahzad; Masood, Misbah; Saeed, M. A.

    2016-01-01

    The current study emphasizes the synthesis of iron oxide nanoparticles (IONPs) and impact of hydrophilic polymer polyvinyl alcohol (PVA) coating concentration as well as anticancer drug doxorubicin (DOX) loading on saturation magnetization for target drug delivery applications. Iron oxide nanoparticles particles were synthesized by a reformed version of the co-precipitation method. The coating of polyvinyl alcohol along with doxorubicin loading was carried out by the physical immobilization method. X-ray diffraction confirmed the magnetite (Fe3O4) structure of particles that remained unchanged before and after polyvinyl alcohol coating and drug loading. Microstructure and morphological analysis was carried out by transmission electron microscopy revealing the formation of nanoparticles with an average size of 10 nm with slight variation after coating and drug loading. Transmission electron microscopy, energy dispersive, and Fourier transform infrared spectra further confirmed the conjugation of polymer and doxorubicin with iron oxide nanoparticles. The room temperature superparamagnetic behavior of polymer-coated and drug-loaded magnetite nanoparticles were studied by vibrating sample magnetometer. The variation in saturation magnetization after coating evaluated that a sufficient amount of polyvinyl alcohol would be 3 wt. % regarding the externally controlled movement of IONPs in blood under the influence of applied magnetic field for in-vivo target drug delivery. PMID:27348436

  15. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  16. Conducting polymer blends: Polypyrrole and polythiophene blends with polystyrene, polycarbonate resin, poly(vinyl alcohol) and poly(vinyl methyl ketone)

    SciTech Connect

    Wang, H.L.

    1992-01-01

    Various aromatic compounds can be polymerized by electrochemical oxidation in solution containing a supporting electrolyte. Most studies have been devoted to polypyrrole and polythiophene. In situ doping during electrochemical polymerization yields free standing conductive polymer film. One major approach to making conducting polymer blends is electrochemical synthesis after coating the host polymer on a platinum electrode. In the electrolysis of pyrrole or thiophene monomer, using (t-Bu[sub 4]N)BF[sub 4] as supporting electrolyte, and acetonitrile as solvent, monomer can diffuse through the polymer film, to produce a polypyrrole or polythiophene blend in the film. Doping occurs along with polymerization to form a conducting polymer alloy. The strongest molecular interaction in polymers, and one that is central to phase behavior, is hydrogen bonding. This mixing at the molecular level enhances the degree of miscibility between two polymers and results in macroscopic properties indicative of single phase behavior. In this dissertation, the authors describes the syntheses of conducting polymer blends: polypyrrole and polythiophene blends with polystyrene, poly(bisphenol-A-carbonate), polyvinyl alcohol and poly(vinyl methyl ketone). The syntheses are performed both electrochemically and chemically. Characterization of these blends was carried out by Fourier Transform Infrared spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis, Scanning Electron Microscopy, and X-ray diffraction. Percolating threshold conductivities occur from 7% to 20% for different polymer blends. The low threshold conductivity is attributed to blend homogeneity enhanced by hydrogen bonding between the carbonyl group in the insulating polymer and the N-H group in polypyrrole. Thermal stability, environmental stability, mechanical properties, crystallinity and morphological structure are also discussed. The authors have also engaged in the polymerization of imidazoles.

  17. Structural changes of water in poly(vinyl alcohol) hydrogel during dehydration

    NASA Astrophysics Data System (ADS)

    Kudo, Kushi; Ishida, Junichi; Syuu, Gika; Sekine, Yurina; Ikeda-Fukazawa, Tomoko

    2014-01-01

    To investigate the mechanism of structural changes of water and polymer networks with drying and swelling, we measured the Raman spectra of a physically cross-linked poly(vinyl alcohol) (PVA) hydrogel synthesized using the freezing-thawing method. The results show that the vibrational frequencies of the O-H and C-H stretching modes decrease with dehydration. The frequency shifts observed are attributed to reduction of free water inside the polymer network. The C-H bonds elongate as the water density decreases, and the average length of the O-H bonds increases with increasing proportion of bound water to the total amount of water. On the basis of the dependence of the frequency shifts on the PVA concentration of the original solution, it was found that the structure of the polymer network in the reswollen hydrogel becomes inhomogeneous due to shrinkage of the polymer network with drying. Furthermore, to investigate the effects of the cross-linking structure on the drying process, these results were compared with those of a chemically cross-linked PVA hydrogel synthesized using glutaraldehyde as a cross-linker. The result shows that the vibrational frequency of the O-H stretching mode for the chemically cross-linked hydrogel increases with dehydration, whereas that of the C-H stretching mode decreases. The opposite trend observed in the O-H stretching mode between the physically and chemically cross-linked hydrogels is due to the difference in the shrinkage rate of the polymer network. Because the rate of shrinking is slow compared with that of dehydration in the chemically cross-linked hydrogel, water density in the polymer network decreases. For the physically cross-linked hydrogel, the polymer network structure can be easily shrunken, and the average strength of hydrogen bonds increases with dehydration. The results show that the structures of the polymer network and water change with the gel preparation process, cross-linking method, and drying and reswelling

  18. Optimizing the tensile properties of polyvinyl alcohol hydrogel for the construction of a bioprosthetic heart valve stent.

    PubMed

    Wan, W K; Campbell, G; Zhang, Z F; Hui, A J; Boughner, D R

    2002-01-01

    Although bioprosthetic heart valves offer the benefits of a natural opening and closing, better hemodynamics, and avoidance of life-long anticoagulant therapy, they nevertheless tend to fail in 10-15 years from tears and calcification. Several authors, including the present ones, have identified the rigid stent as a factor contributing to these failures. The ultimate solution is an artificial heart valve that has mechanical properties that allow it to move in conformity with the aortic root during the cardiac cycle, has superior hemodynamics, is nonthrombogenic, will last more than 20 years, and mitigates the need for anticoagulants. We have identified a polymer, polyvinyl alcohol (PVA) hydrogel, that has mechanical properties similar to soft tissue. The purpose of this research is to match the tensile properties of PVA to the porcine aortic root and to fabricate a stent prototype for a bioprosthetic heart valve with the use of the PVA hydrogel. Specimens of 15% w/w PVA were prepared by processing through 1-6 cycles of freezing (-20 degrees C) at 0.2 degrees C/min freeze rate and thawing (+20 degrees C) at different thawing rates (0.2 degrees C/min and 1 degrees C/min), for different holding times (1 and 6 h) at -20 degrees C. Subsequently tensile tests and stress-relaxation tests were conducted on the specimens. The different holding times at -20 degrees C demonstrated no difference in the result. The slower thawing rate improved the tensile properties but did not produce significant changes on the stress-relaxation properties. The nonlinear stress-strain curve for the PVA after the fourth freeze-thaw cycle matched the porcine aortic root within the physiological pressure range. The stress-relaxation curve for PVA also approximated the shape of the aortic root. The complex geometry of an artificial heart valve stent was successfully injection molded. These results, in combination with other preliminary findings for biocompatibility and fatigue behavior, suggest

  19. The plasticizing mechanism and effect of calcium chloride on starch/poly(vinyl alcohol) films.

    PubMed

    Jiang, Xiancai; Jiang, Ting; Gan, Lingling; Zhang, Xiaofei; Dai, Hua; Zhang, Xi

    2012-11-01

    Starch/poly(vinyl alcohol) (PVA) films were prepared with calcium chloride (CaCl(2)) as the plasticizer. The micro morphology of pure starch/PVA film and CaCl(2) plasticized starch/PVA film was observed by scanning electron microscope. The interaction between CaCl(2) and starch/PVA molecules was investigated by Fourier transform infrared spectroscopy. The influence of CaCl(2) on the crystalline, thermal and mechanical properties of starch/PVA films was studied by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and tensile testing, respectively. The results indicated that CaCl(2) could interact with starch and PVA molecules and then effectively destroy the crystals of starch and PVA. Starch/PVA films plasticized with CaCl(2) became soft and ductile, with lower tensile strength and higher elongation at break compared with pure starch/PVA film. The water content of starch/PVA film would increase with the addition of CaCl(2). This is an important cause of the plasticization of CaCl(2) on starch/PVA film. PMID:22944433

  20. Unzipped multiwalled carbon nanotube oxide/multiwalled carbon nanotube hybrids for polymer reinforcement.

    PubMed

    Fan, Jinchen; Shi, Zixing; Tian, Ming; Wang, Jialiang; Yin, Jie

    2012-11-01

    Multiwalled carbon nanotubes (MWNTs) have been widely used as nanofillers for polymer reinforcement. However, it has been restricted by the limited available interface area of MWNTs in the polymer matrices. Oxidation unzipping of MWNTs is an effective way to solve this problem. The unzipped multiwalled carbon nanotube oxides (UMCNOs) exhibit excellent enhancement effect with low weight fractions, but agglomeration of UMCNOs at a relatively higher loading still hampered the mechanical reinforcement of polymer composites. In this paper, we interestingly found that the dispersion of UMCNOs in polymer matrices can be significantly improved with the combination of pristine MWNTs. The hybrids of MWNTs and UMCNOs (U/Ms) can be easily obtained by adding the pristine MWNTs into the UMCNOs aqueous dispersion, followed by sonication. With a π-stacking interaction, the UMCNOs were attached onto the outwalls of MWNTs. The morphologies and structure of the U/Ms were characterized by several measurements. The mechanical testing of the resultant poly(vinyl alcohol) (PVA)-based composites demonstrated that the U/Ms can be used as ideal reinforcing fillers. Compared to PVA, the yield strength and Young's modulus of U/M-PVA composites with a loading of 0.7 wt % of the U/Ms approached ∼145.8 MPa and 6.9 GPa, respectively, which are increases of ∼107.4% and ∼122.5%, respectively. The results of tensile tests demonstrated that the reinforcement effect of U/Ms is superior to the individual UMCNOs and MWNTs, because of the synergistic interaction of UMCNOs and MWNTs. PMID:23121120

  1. Development of a complex hydrogel of hyaluronan and PVA embedded with silver nanoparticles and its facile studies on Escherichia coli.

    PubMed

    Zhang, Fei; Wu, Juan; Kang, Ding; Zhang, Hongbin

    2013-01-01

    Novel nanocomposite hydrogels composed of hyaluronan (HA), poly(vinyl alcohol) (PVA) and silver nanoparticles were prepared by several cycles of freezing and thawing. The nanocomposite was then characterised using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and scanning electron microscopy (SEM). The complex hydrogels consisted of semi-interpenetrating network structures, with PVA microcrystallines as junction zones. By increasing the HA content, the crystallinity and melting temperature of the complex hydrogels decreased, whereas the glass transition temperatures of these materials increased because of the steric hindrance of HA and the occurrence of intermolecular interactions through hydrogen bonding between HA and PVA in the complex hydrogels. Swelling studies showed that in comparison with the swelling properties of the cryogels from PVA alone, those of the complex hydrogels can be significantly improved and presented in a pH-sensitive manner. In addition, silver nanoparticles were synthesised through UV-initiated photoreduction with HA functioning as a reducing agent and stabiliser. The silver nanoparticles were then incorporated in situ into the HA/PVA complex hydrogel matrix. The size and morphology of the as-prepared Ag nanoparticles were investigated through ultraviolet-visible light spectroscopy, transmission electron microscopy, XRD and thermogravimetric analysis. The experimental results indicated that silver nanoparticles 20-50 nm in size were uniformly dispersed in the hydrogel matrix. The antibacterial effects of the HA/PVA/Ag nanocomposite hydrogel against Escherichia coli were evaluated. The results show that this nanocomposite hydrogel possesses high antibacterial property and has a potential application as a wound dressing material. PMID:23829455

  2. Preparation of antibacterial PVA and PEO nanofibers containing Lawsonia Inermis (henna) leaf extracts.

    PubMed

    Avci, H; Monticello, R; Kotek, R

    2013-01-01

    Concerns about health issues and environmental pollution stimulate research to find new health and hygiene related products with healing properties and minimum negative effect on the environment. Development of new, natural antibacterial agents has become one of the most important research areas to combat some pathogens such as Gram- positive and Gram-negative bacteria, fungi, algae, yeast, and some microorganisms which cause serious human infections. Lawsonia Inermis (henna) leaf extracts for preparation of antibacterial poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) nanofibers via electrospinning technique were investigated. PEO and PVA based electrospun fibers containing henna extract were verified by the appearance of FTIR peaks corresponding to the pure extract. Our study demonstrates that 2.793 wt.% Li in PVA and PEO based solutions showed bactericidal effects against Staphylococcus aureus and bacteriostatic action to Escherichia coli. Concentrations of henna leaf extract strongly impacted antibacterial activities against both bacteria. Henna leaves have a great potential to be used as a source of a potent eco-friendly antimicrobial agent. PMID:23758488

  3. Effect of UV irradiation on optical, mechanical and microstructural properties of PVA/NaAlg blends

    NASA Astrophysics Data System (ADS)

    Sheela, T.; Bhajantri, R. F.; Ravindrachary, V.; Rathod, Sunil G.; Pujari, P. K.; Poojary, Boja; Somashekar, R.

    2014-10-01

    Poly(vinyl alcohol) (PVA)/Sodium alginate (NaAlg) blend films with 60:40 wt% were prepared by solution casting method and subjected to UV irradiation for different intervals of time. The optical, mechanical and morphological properties of the blend films were modified after UV irradiation. The FTIR and FT-Raman results show the chemical interaction between PVA and NaAlg. The UV-vis absorption peak at 278 nm shifts slightly towards longer wavelength and the absorption increases with irradiation time, indicate the increase in crosslinking network. The XRD results show an increase in amorphous nature with increase in UV irradiation time. The DSC/TGA results show a single glass transition temperature (Tg), which confirm that the blends are completely miscible and thermally stable up to 250 °C. The Young's modulus, tensile strength and stiffness of the blend films increase with increase in UV irradiation time. The SEM images confirm that the surface of 48 h UV irradiated PVA:NaAlg blend is more photo-resistant than unirradiated blend.

  4. A novel gellan-PVA nanofibrous scaffold for skin tissue regeneration: Fabrication and characterization.

    PubMed

    Vashisth, Priya; Nikhil, Kumar; Roy, Partha; Pruthi, Parul A; Singh, Rajesh P; Pruthi, Vikas

    2016-01-20

    In this investigation, we have introduced novel electrospun gellan based nanofibers as a hydrophilic scaffolding material for skin tissue regeneration. These nanofibers were fabricated using a blend mixture of gellan with polyvinyl alcohol (PVA). PVA reduced the repulsive force of resulting solution and lead to formation of uniform fibers with improved nanostructure. Field emission scanning electron microscopy (FESEM) confirmed the average diameter of nanofibers down to 50 nm. The infrared spectra (IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis evaluated the crosslinking, thermal stability and highly crystalline nature of gellan-PVA nanofibers, respectively. Furthermore, the cell culture studies using human dermal fibroblast (3T3L1) cells established that these gellan based nanofibrous scaffold could induce improved cell adhesion and enhanced cell growth than conventionally proposed gellan based hydrogels and dry films. Importantly, the nanofibrous scaffold are biodegradable and could be potentially used as a temporary substrate/or biomedical graft to induce skin tissue regeneration. PMID:26572421

  5. Processing and characterization of chitosan/PVA and methylcellulose porous scaffolds for tissue engineering.

    PubMed

    Kanimozhi, K; Khaleel Basha, S; Sugantha Kumari, V

    2016-04-01

    Biomimetic porous scaffold chitosan/poly(vinyl alcohol) CS/PVA containing various amounts of methylcellulose (MC) (25%, 50% and 75%) incorporated in CS/PVA blend was successfully produced by a freeze drying method in the present study. The composite porous scaffold membranes were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), swelling degree, porosity, degradation of films in Hank's solution and the mechanical properties. Besides these characterizations, the antibacterial activity of the prepared scaffolds was tested, toward the bacterial species Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli). FTIR, XRD and DSC demonstrated that there was strong intermolecular hydrogen bonding between the molecules of CS/PVA and MC. The crystalline microstructure of the scaffold membranes was not well developed. SEM images showed that the morphology and diameter of the scaffolds were mainly affected by the weight ratio of MC. By increasing the MC content in the hybrid scaffolds, their swelling capacity and porosity increased. The mechanical properties of these scaffolds in dry and swollen state were greatly improved with high swelling ratio. The elasticity of films was also significantly improved by the incorporation of MC, and the scaffolds could also bear a relative high tensile strength. These findings suggested that the developed scaffold possess the prerequisites and can be used as a scaffold for tissue engineering. PMID:26838875

  6. Preparation and characterization of electrical conductive PVA based materials for peripheral nerve tube-guides.

    PubMed

    Gonçalves, C; Ribeiro, J; Pereira, T; Luís, A L; Mauricio, A C; Santos, J D; Lopes, M A

    2016-08-01

    Peripheral nerve regeneration is a serious clinical problem. Presently, there are several nerve tube-guides available in the market, however with some limitations. The goal of this work was the development of a biomaterial with high electrical conductivity to produce tube-guides for nerve regeneration after neurotmesis injuries whenrver an end-to-end suture without tension is not possible. A matrix of poly(vinyl alcohol) (PVA) was used loaded with the following electrical conductive materials: COOH-functionalized multiwall carbon nanotubes (MWCNTs), poly(pyrrole) (PPy), magnesium chloride (MgCl2 ), and silver nitrate (AgNO3 ). The tube-guide production was carried out by a freezing/thawing process (physical crosslinking) with a final annealing treatment. After producing the tube-guide for nerve regeneration, the physicochemical characterization was performed. The most interesting results were achieved by loading PVA with 0.05% of PPy or COOH- functionalized CNTs. These tubes combined the electrical conductivity of carbon nanotubes (CNTs) and PPy with the biocompatibility of PVA matrix, with potential clinical application for nerve regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1981-1987, 2016. PMID:27027727

  7. Interface investigation of the alcohol-/water-soluble conjugated polymer PFN as cathode interfacial layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shu; Wang, Rui; Ying Mao, Hong; He, Zhicai; Wu, Hongbin; Chen, Wei; Cao, Yong

    2013-09-01

    In this work, in situ ultraviolet photoelectron spectroscopy measurements were used to investigate the working mechanism of an alcohol-/water-soluble conjugated polymer poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode interfacial layer in organic solar cells from the view of interfacial energy level alignment. Fullerene (C60) was chosen as the model acceptor material in contact with PFN as well as two other cathode interfacial layers ZnO and TiO2 in the configuration of an inverted solar cell structure. Significant charge transfer between PFN modified ITO (indium tin oxide) electrode and C60 is observed due to the low work function of PFN. This results in the Fermi level of the substrate pinned very close to the lowest unoccupied molecular orbital of C60 as well as an additional electric field at the cathode/acceptor interface. Both of them facilitate the electron extraction from the acceptor C60 to the ITO cathode, as confirmed by the electrical measurements of the electron-only devices with PFN modification. The better electron extraction originated from the Fermi level pinning and the additional interface electric field are believed to contribute to the efficiency enhancement of the inverted organic solar cells employing PFN as cathode interfacial layer.

  8. Poly(vinyl Alcohol) Borate Gel Polymer Electrolytes Prepared by Electrodeposition and Their Application in Electrochemical Supercapacitors.

    PubMed

    Jiang, Mengjin; Zhu, Jiadeng; Chen, Chen; Lu, Yao; Ge, Yeqian; Zhang, Xiangwu

    2016-02-10

    Gel polymer electrolytes (GPEs) have been studied for preparing flexible and compact electrochemical energy storage devices. However, the preparation and use of GPEs are complex, and most GPEs prepared through traditional methods do not have good wettability with the electrodes, which retard them from achieving their performance potential. In this study, these problems are addressed by conceiving and implementing a simple, but effective, method of electrodepositing poly(vinyl alcohol) potassium borate (PVAPB) GPEs directly onto the surfaces of active carbon electrodes for electrochemical supercapacitors. PVAPB GPEs serve as both the electrolyte and the separator in the assembled supercapacitors, and their scale and shape are determined solely by the geometry of the electrodes. PVAPB GPEs have good bonding to the active electrode materials, leading to excellent and stable electrochemical performance of the supercapacitors. The electrochemical performance of PVAPB GPEs and supercapacitors can be manipulated simply by adjusting the concentration of KCl salt used during the electrodeposition process. With a 0.9 M KCl concentration, the as-prepared supercapacitors deliver a specific capacitance of 65.9 F g(-1) at a current density of 0.1 A g(-1) and retain more than 95% capacitance after 2000 charge/discharge cycles at a current density of 1 A g(-1). These supercapacitors also exhibit intelligent high voltage self-protection function due to the electrolysis-induced cross-linking effect of PVAPB GPEs. PMID:26788748

  9. Proton-conducting membrane based on epoxy resin-poly(vinyl alcohol)-sulfosuccinic acid blend and its nanocomposite with sulfonated multiwall carbon nanotubes for fuel-cell application

    NASA Astrophysics Data System (ADS)

    Kakati, Nitul; Das, Gautam; Yoon, Young Soo

    2016-01-01

    A blend of poly(vinyl alcohol) (PVA) with diglycidyl ether of bisphenol-A (DGB) in the presence of sulfosuccinic acid (SSA) was investigated as hydrolytically-stable proton-conducting membrane. The PVA modification was carried out by varying the DGB:SSA ratio (20:20, 10:20, and 5:20). A nanocomposite of the blend (20:20) was prepared with sulfonated multiwall carbon nanotubes (viz., 1, 3 and 5 wt%). The water uptake behavior and the proton conductivity of the prepared membranes were evaluated. The ionic conductivity of the membranes and the water uptake behavior depended on the s-MWCNT and the DGB contents. The ionic conductivity showed an enhancement for the blend and for the nanocomposite membrane as compared to the pristine polymer.

  10. On the Development of Thermally Stable Semi-IPNs of PVA and PAN using IR, DSC and XRD Studies

    NASA Astrophysics Data System (ADS)

    Deshpande, Deepti S.; Bajpai, R.; Bajpai, A. K.

    2011-07-01

    A novel biopolymer based Semi-IPN of polyvinyl alcohol (PVA) and polycrylonitrile (PAN) were synthesized in various proportions by redox polymerization and analyzed thermally by differential scanning calorimetry (DSC). DSC thermograms shows good thermal stability, as a result of incorporation of acrylonitrile as the second network. The structural and morphological study of these semi-IPNs by FTIR and XRD technique, respectively, were correlated. The approach seems to be beneficial for various biomedical applications.

  11. Studies on PVA based nanocomposite Proton Exchange Membrane for Direct methanol fuel cell (DMFC) applications

    NASA Astrophysics Data System (ADS)

    Bahavan Palani, P.; Kannan, R.; Rajashabala, S.; Rajendran, S.; Velraj, G.

    2015-02-01

    Different concentrations of Poly (vinyl alcohol)/Montmorillonite (PVA/MMT) based proton exchange membranes (PEMs) have been prepared by solution casting method. The structural and electrical properties of these composite membranes have been characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopic (FTIR) and AC impedance spectroscopic methods. The conductivity of the PEMs has been estimated for the different concentration of MMT. Water/Methanol uptake measurement were also analyzed for the prepared PEMs and presented. The proton conductivity studies were carried out at room temperature with 100% of humidity.

  12. Characterization of solid dispersions of Patchouli alcohol with different polymers: effects on the inhibition of reprecipitation and the improvement of dissolution rate.

    PubMed

    Chen, Yun Long; Liao, Jin Bin; Liang, Yong Zhuo; Xie, Jian Hui; Wu, Qiong; Lai, Xiao Ping; Chen, Jian Nan; Su, Zi Ren; Lin, Zhi Xiu

    2015-03-01

    Solid dispersion technique is known to be an effective approach for the polymer to keep drugs stable in the solid state, thereby improving the dissolution rate and oral bioavailability through inhibiting reprecipitation in supersaturated solution. In this study, to evaluate the inhibitory effect of polyethylene glycol-6000 (PEG), Polyvinylpyrrolidone K30 (PVP) and Aminoalkyl methacrylate copolymer (Eudragit), the reprecipitation profiles were observed from supersaturated solutions of Patchouli alcohol (PA) in the presence and absence of the polymers. Furthermore, the dissolution profiles of PA solid dispersions formulated with PEG, PVP or Eudragit were compared for investigating the effect on improving dissolution of each polymer. Solid dispersions formulated with Eudragit were found to result in solution with the highest extent of supersaturation. By contrast, PEG and PVP were less effective. At equivalent supersaturation, all three polymers are capable of mitigating reprecipitation relative to that of PA alone. In addition, in the PA solid dispersion with Eudragit (E-SD (1/3)), the highest concentration of supersaturation of PA was maintained for prolonged time. These results unambiguously indicate that it is imperative to select the appropriate polymer and drug/polymer ratio in addition to considering the stability of the supersaturated solution, which was generated following dissolution of amorphous solid dispersion. PMID:24410045

  13. Cylindrical diffractive lenses recorded on PVA/AA photopolymers

    NASA Astrophysics Data System (ADS)

    Fernández, R.; Gallego, S.; Márquez, A.; Navarro-Fuster, V.; Francés, J.; Neipp, C.; Beléndez, A.; Pascual, I.

    2016-04-01

    Photopolymers are optical recording materials appealing for many different applications such as holography, data storage, interconnectors, solar concentrations, or wave-guides fabrication. Recently the capacity of photopolymers to record diffractive optical elements (DOE's) has been investigated. Different authors have reported proposes to record DOE like fork gratings, photonics structures, lenses, sinusoidal, blazed or fork gratings. In these experiments there are different experimental set-ups and different photopolymers. In this work due to the improvement in the spatial light modulation technology together with the photopolymer science we propose a recording experimental system of DOE using a Liquid Cristal based on Silicon (LCoS) display as a master to store complex DOE like cylindrical lenses. This technology permits us an accurate control of the phase and the amplitude of the recording beam, with a very small pixel size. The main advantage of this display is that permit us to modify the DOE automatically, we use the software of the LCoS to send the voltage to each pixel In this work we use a photopolymer composed by acrylamide (AA) as polymerizable monomer and polyvinyl alcohol (PVA). We use a coverplated and index matched photopolymer to avoid the influence of the thickness variation on the transmitted light. In order to reproduce the material behaviour during polymerization, we have designed our model to simulate cylindrical lenses and used Fresnel propagation to simulate the light propagation through the DOE and analyze the focal plane and the properties of the recorded lenses.

  14. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants. PMID:22138171

  15. Apatite coating of electrospun PLGA fibers using a PVA vehicle system carrying calcium ions.

    PubMed

    Kim, In Ae; Rhee, Sang-Hoon

    2010-01-01

    A novel method to coat electrospun poly(D,L-lactic-co-glycolic acid) (PLGA) fiber surfaces evenly and efficiently with low-crystalline carbonate apatite crystals using a poly(vinyl alcohol) (PVA) vehicle system carrying calcium ions was presented. A non-woven PLGA fabric was prepared by electrospinning: a 10 wt% PLGA solution was prepared using 1,1,3,3-hexafluoro-2-propanol as a solvent and electrospun under a electrical field of 1 kV/cm using a syringe pump with a flowing rate of 3 ml/h. The non-woven PLGA fabric, 12 mm in diameter and 1 mm in thickness, was cut and then coated with a PVA solution containing calcium chloride dihydrate (specimen PPC). As controls, pure non-woven PLGA fabric (specimen P) and fabric coated with a calcium chloride dihydrate solution without PVA (specimen PC) were also prepared. Three specimens were exposed to simulated body fluid for 1 week and this exposure led to form uniform and complete apatite coating layer on the fiber surfaces of specimen PPC. However, no apatite had formed to the fiber surfaces of specimen P and only inhomogeneous coating occurred on the fiber surfaces of specimen PC. These results were explained in terms of the calcium chelating and adhesive properties of PVA vehicle system. The practical implication of the results is that this method provides a simple but efficient technique for coating the fiber surface of an initially non-bioactive material with low-crystalline carbonate apatite. PMID:20507712

  16. 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...

  17. Boronic acid as an efficient anchor group for surface modification of solid polyvinyl alcohol.

    PubMed

    Nishiyabu, Ryuhei; Shimizu, Ai

    2016-07-28

    We report the use of boronic acid as an anchor group for surface modification of solid polyvinyl alcohol (PVA); the surfaces of PVA microparticles, films, and nanofibers were chemically modified with boronic acid-appended fluorescent dyes through boronate esterification using a simple soaking technique in a short time under ambient conditions. PMID:27311634

  18. Compatibility of Polyvinyl Alcohol with the 241-F/H Tank Farm Liquid Waste

    SciTech Connect

    Oji, L.N.

    1998-11-25

    This report describes results from laboratory-scale oxidative mineralization of polyvinyl alcohol (PVA), and the evaluation of the F/H Tank Farms as a storage/disposal option for PVA waste solution generated in the Canyons and B-line decontamination operations.

  19. Oxidative mineralization and characterization of polyvinyl alcohol for compatibility with tank farm processing chemistry

    SciTech Connect

    Oji, L.N.

    2000-01-04

    Polyvinyl alcohol (PVA) material has been evaluated for use as a cost-effective substitute for conventional cellulose-based disposal materials (decontamination mops and wipes), plastic bags, and disposable personal protection clothing, that are currently used at Savannah River Site. This study also provides process design criteria for ultraviolet/ultrasonic/hydrogen peroxide PVA reactor system.

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

    PubMed

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

    2013-06-01

    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. PMID:23618287

  1. Mechanical properties of hybrid polymer nanotube systems

    NASA Astrophysics Data System (ADS)

    Coleman, Jonathan N.; Cadek, Martin; Dalton, Alan B.; Munoz, Edgar; Razal, Joselito; Baughman, Ray H.; Blau, Werner J.

    2003-04-01

    In this work, mechanical properties of hybrid materials fabricated from nanotubes and commercially available polymers were investigated. It was found that, by adding various concentrations of arc discharge multiwall nanotubes, both Young"s modulus and hardness increased by factors of 1.8 and 1.6 at 1wt% in PVA and 2.8 and 2.0 at 8wt% in PVK, in reasonable agreement with the Halpin-Tsai theory. Furthermore, the presence of the nanotubes was found to nucleate crystallization of the PVA. This crystal growth is thought to enhance matrix-nanotube stress transfer. In addition, microscopy studies suggest extremely strong interfacial bonding in the PVA-based composite. This is manifested by the fracture of the polymer rather that the polymer-nanotube interface. The dependence of the polymer nanotube interfacial interaction on host polymer was studied by intercalating various polymers (PVA, PVP and PS) into single wall nanotube buckypaper. Even for short soak times, significant polymer intercalation into existing free volume was observed. Depending on the polymer and the level of intercalation tensile tests on intercalated sheets showed that the Young"s modulus, strength and toughness increased by factors of 3, 9 and 28, respectively. This indicates that the intercalated polymer enhances load transmission between nanotubes due the significant stress transfer. The level of stress transfer was observed to scale with polymer hydrophobicity as expected.

  2. 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.

  3. 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.

  4. XPS study of Rhodamine B doped PVA nanocomposite films as a function of annealing

    NASA Astrophysics Data System (ADS)

    Tripathi, J.; Tripathi, S.; Sharma, A.; Bisen, R.; Singh, J.

    2016-05-01

    The bonding properties of PVA thin films are explored as a function of annealing in pure and Rhodamine B doped self-standing films. X-ray photoelectron spectroscopy measurements have shown high quality, impurity free films, where the bonding is found between C and O elements in agreement with the standard data of polymers. Upon annealing, the bonds break and signals come only from elemental carbon and oxygen at their respective binding energy positions. The experiments are able to show that upon annealing at 65° C, all the bonds break and hence electronic properties are completely modified.

  5. Improving wet and dry strength properties of recycled old corrugated carton (OCC) pulp using various polymers.

    PubMed

    Hamzeh, Yahya; Sabbaghi, Sanaz; Ashori, Alireza; Abdulkhani, Ali; Soltani, Farshid

    2013-04-15

    In this study, the application of different dosages of low and high molecular weights (MW) of chitosan (Ch), cationic starch (CS) and poly vinyl alcohol (PVA) were systematically investigated using old corrugated carton (OCC) furnishes. Various sequences of above-mentioned polymeric additives were also examined to find out the optimal combination for improving both wet and dry tensile strength. For each treatment, 4 handsheets, each having basis weight of 100 g/m(2), were made. In general, the tensile strength of handsheets was significantly affected by the addition of polymeric agents. The enhancing effect of additives on dry tensile property was much higher than wet condition. The results also showed that the tensile strength of the samples made from OCC furnishes were improved upon the addition of high molecular weight chitosan (ChI) compared to the untreated ones (control). The low MW chitosan did not change the properties of handsheets dramatically. Application of polymeric agents moderately decreased the stretch to rupture, however with increasing dosage the stretch was improved. Sequential addition of used polymers showed that triple application of polymers was beneficial to both dry and wet tensile strength, although the effect was larger for dry. The best results in wet and dry tensile strengths were achieved using sequential of PVA-ChI-CS. Sequential addition of oppositely charged polymers forms a macromolecular layered structure of polyelectrolytes. PMID:23544577

  6. Enzyme-polymers conjugated to quantum-dots for sensing applications.

    PubMed

    Mansur, Alexandra; Mansur, Herman; González, Juan

    2011-01-01

    In the present research, the concept of developing a novel system based on polymer-enzyme macromolecules was tested by coupling carboxylic acid functionalized poly(vinyl alcohol) (PVA-COOH) to glucose oxidase (GOx) followed by the bioconjugation with CdS quantum-dots (QD). The resulting organic-inorganic nanohybrids were characterized by UV-visible spectroscopy, infrared spectroscopy, Photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The spectroscopy results have clearly shown that the polymer-enzyme macromolecules (PVA-COOH/GOx) were synthesized by the proposed zero-length linker route. Moreover, they have performed as successful capping agents for the nucleation and constrained growth of CdS quantum-dots via aqueous colloidal chemistry. The TEM images associated with the optical absorption results have indicated the formation of CdS nanocrystals with estimated diameters of about 3.0 nm. The "blue-shift" in the visible absorption spectra and the PL values have provided strong evidence that the fluorescent CdS nanoparticles were produced in the quantum-size confinement regime. Finally, the hybrid system was biochemically assayed by injecting the glucose substrate and detecting the formation of peroxide with the enzyme horseradish peroxidase (HRP). Thus, the polymer-enzyme-QD hybrid has behaved as a nanostructured sensor for glucose detecting. PMID:22163736

  7. Enzyme-Polymers Conjugated to Quantum-Dots for Sensing Applications

    PubMed Central

    Mansur, Alexandra; Mansur, Herman; González, Juan

    2011-01-01

    In the present research, the concept of developing a novel system based on polymer-enzyme macromolecules was tested by coupling carboxylic acid functionalized poly(vinyl alcohol) (PVA-COOH) to glucose oxidase (GOx) followed by the bioconjugation with CdS quantum-dots (QD). The resulting organic-inorganic nanohybrids were characterized by UV-visible spectroscopy, infrared spectroscopy, Photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The spectroscopy results have clearly shown that the polymer-enzyme macromolecules (PVA-COOH/GOx) were synthesized by the proposed zero-length linker route. Moreover, they have performed as successful capping agents for the nucleation and constrained growth of CdS quantum-dots via aqueous colloidal chemistry. The TEM images associated with the optical absorption results have indicated the formation of CdS nanocrystals with estimated diameters of about 3.0 nm. The “blue-shift” in the visible absorption spectra and the PL values have provided strong evidence that the fluorescent CdS nanoparticles were produced in the quantum-size confinement regime. Finally, the hybrid system was biochemically assayed by injecting the glucose substrate and detecting the formation of peroxide with the enzyme horseradish peroxidase (HRP). Thus, the polymer-enzyme-QD hybrid has behaved as a nanostructured sensor for glucose detecting. PMID:22163736

  8. Immobilization of Firefly Luciferase on PVA-co-PE Nanofibers Membrane as Biosensor for Bioluminescent Detection of ATP.

    PubMed

    Wang, Wenwen; Zhao, Qinghua; Luo, Mengying; Li, Mufang; Wang, Dong; Wang, Yuedan; Liu, Qiongzhen

    2015-09-16

    The bioluminescent reaction catalyzed by firefly luciferase has become widely established as an outstanding analytical system for assay of adenosine triphosphate (ATP). When in solution, the luciferase is unstable and cannot be reused. The problem can be partially solved by immobilizing the luciferase on solid substrates. The poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers membrane has abundant active hydroxyl groups on the surface. The PVA-co-PE nanofibers membrane was first activated by cyanuric chloride with triazinyl group. Then the activated PVA-co-PE nanofibers membrane was subsequently reacted with 1,3-propanediamine and biotin. The firefly luciferase was immobilized onto the surface of 1,3-propanediamine- and biotin-functionalized membranes. The surface chemical structure and morphologies of nanofibers membranes were characterized by FTIR-ATR spectra and SEM. The hydrophilicity of membranes was tested by water contact angle measurements. The detection of fluorescence intensity displayed that the firefly-luciferase-immobilized PVA-co-PE nanofibers membranes indicated high catalytic activity and efficiency. Especially, the firefly-luciferase-immobilized nanofiber membrane which was functionalized by biotin can be a promising candidate as biosensor for bioluminescent detection of ATP because of its high detection sensitivity. PMID:26275118

  9. Ectopic osteochondral formation of biomimetic porous PVA-n-HA/PA6 bilayered scaffold and BMSCs construct in rabbit.

    PubMed

    Qu, Dan; Li, Jihua; Li, Yubao; Khadka, Ashish; Zuo, Yi; Wang, Hang; Liu, Yiming; Cheng, Lin

    2011-01-01

    In this work, the novel poly vinyl alcohol/gelatin-nano-hydroxyapatite/polyamide6 (PVA-n-HA/PA6) bilayered scaffold with biomimetic properties for articular cartilage and subchondral bone is developed. Furthermore, when these osteochondral scaffolds were seeded with induced bone mesenchymal stem cells (BMSCs) and implanted at ectopic sites, showed the potential for an engineered cartilage tissue and the corresponding subchondral bone. BMSCs were expanded in vitro and induced to chondrogenic or osteogenic potential by culturing in suitable media for 14 days. Subsequently, these induced cells were seeded into PVA-n-HA/PA6 separately, and the constructs were implanted into the rabbit muscle pouch for upto 12 weeks. Ectopic neocartilage formation in the PVA layer and reconstitution of the subchondral bone which remained confined within the n-HA/PA6 layer with the alteration of the cellular phenotype were identified with Masson's trichrome stain. Simultaneously, the RT-PCR results confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous tissue, such as collagen type II (Col-II), or alternatively, markers for osteoid tissue, such as collagen type I (Col-I) at the corresponding layers. During ectopic implantation, the underlying subchondral bone layer was completely integrated with the cartilage layer. The result from the ectopic osteochondral scaffolds implantation suggests that PVA-n-HA/PA6 with induced BMSCs is a possible substitute with potential in cartilage repair strategies. PMID:20967773

  10. Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors

    PubMed Central

    Li, Dongsheng; Cao, Hai

    2012-01-01

    The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

  11. Preparation and characterisation of ZnFe 2O 4/ZnO polymer nanocomposite sensors for the detection of alcohol vapours

    NASA Astrophysics Data System (ADS)

    Arshak, K.; Moore, E.; Cunniffe, C.; Nicholson, M.; Arshak, A.

    2007-07-01

    During the last 10 years, a large interest has developed in the preparation of nanocomposite structures by embedding inorganic nanoparticles into polymeric materials. These materials combine the properties of the inorganic fillers with the processability and flexibility of polymers. The versatility of polymer nanocomposite systems is of special interest to the gas sensor industry where arrays of polymer/carbon black composites have been used to identify gases and odours. These polymer gas sensors provide selectivity based on their chemical structures and operate at room temperature, which provide advantages over thick-film metal oxide gas sensors. ZnFe 2O 4 and ZnO have excellent stability, high sensitivity, low fabrication complexity and moderate operating temperatures, which are ideal properties for a gas sensing material. In this work, the development of a thick-film ZnFe 2O 4/ZnO sensor, which operates at room temperature and a drop-coated conducting polymer composite sensor containing 30 w/w% ZnFe 2O 4/ZnO nanoparticles is discussed. The sensors were tested in a fully automated test rig and showed promising results for the detection of alcohol vapours.

  12. An experimental investigation of enzyme release from poly(vinyl alcohol) crosslinked microspheres.

    PubMed

    Bachtsi, A R; Kiparissides, C

    1995-01-01

    Crosslinked poly(vinyl alcohol) particles were prepared by the addition of glutaraldehyde into a PVA methanol/water solution in the presence of 0.2 N sulphuric acid. The polymer solution was dispersed in mineral oil in a jacketed vessel, with the aid of a six-blade impeller. Spherical crosslinked particles in the size range 30-80 microns were obtained by varying the degree of agitation or/and the amount of suspending agent. The crosslinked particles, after washing and drying, were placed into a protease enzyme solution for loading. The enzyme-containing water-swollen particles were subsequently removed from the solution and the enzyme release kinetics determined by a UV spectrophotometer. The influence of the degree of crosslinking, ionic strength, pH, particle size, and degree of hydrophilicity of the polymer on the enzyme activity was retained during the adsorption-desorption studies. The release behaviour of enzymes from crosslinked PVA particles exhibited a biphasic kinetic model, with an initial fast release followed by a much slower release rate. PMID:7730954

  13. Development of potentiometric urea biosensor based on urease immobilized in PVA-PAA composite matrix for estimation of blood urea nitrogen (BUN).

    PubMed

    Jha, Sandeep Kumar; Topkar, Anita; D'Souza, Stanislaus F

    2008-04-24

    A urea biosensor was developed using the urease entrapped in polyvinyl alcohol (PVA) and polyacrylamide (PAA) composite polymer membrane. The membrane was prepared on the cheesecloth support by gamma-irradiation induced free radical polymerization. The performance of the biosensor was monitored using a flow-through cell, where the membrane was kept in conjugation with the ammonia selective electrode and urea was added as substrate in phosphate buffer medium. The ammonia produced as a result of enzymatic reaction was monitored potentiometrically. The potential of the system was amplified using an electronic circuit incorporating operational amplifiers. Automated data acquisition was carried by connecting the output to a 12-bit analog to digital converter card. The sensor working range was 1-1000 mM urea with a response time of 120 s. The enzyme membranes could be reused 8 times with more than 90% accuracy. The biosensor was tested for blood urea nitrogen (BUN) estimation in clinical serum samples. The biosensor showed good correlation with commercial Infinitytrade mark BUN reagent method using a clinical chemistry autoanalyzer. The membranes could be preserved in phosphate buffer containing dithiothreitol, beta-mercaptoethanol and glycerol for a period of two months without significant loss of enzyme activity. PMID:18329719

  14. Water transport in cement-in-polymer dispersions at variable temperature studied by magnetic resonance imaging

    SciTech Connect

    Olaru, A.M. Bluemich, B.; Adams, A.

    2013-02-15

    The hydration of recently developed cement-in-polymer dispersions (c/p) containing 30% and 40% poly (vinyl acetate) [PVAc] and 30% poly(vinyl alcohol) [PVA] was monitored on-line at various temperatures using {sup 1}H Single Point Imaging (SPI). The physical changes undergone by the materials as well as the complex manner in which the absorption process takes place and the evolution of the spin density were characterized and were found to be strongly dependent on the nature and amount of polymer and on the temperature. Based on the results obtained we propose a simple mathematical model which can be used to characterize the behaviour of the c/p dispersions exposed to hydration at variable temperature.

  15. Optical memory using localized photoinduced anisotropy in a synthetic dye-polymer

    NASA Astrophysics Data System (ADS)

    Kuo, Chai-Pei

    1991-07-01

    We present a read/write/erase all-optical memory that fully utilizes local photoinduced birefringence in a synthetic dye-polymer. Memory reading is based on an optical vector-matrix inner product. The intrinsic chromatic characteristics of the proposed memory storage medium is the key to a novel form of nonmechanical parallel memory storage. Green light at 514.5 nm writes a spatial pattern and read light at 632 nm reads it. The dynamic memory material is an improved polyvinyl-alcohol (PVA) polymer film doped with Azo dye. Unique to this material is low optical power, no significant memory degradation after the recording process, and local information erasure or rewrite at any time. The material operates at room temperature with no sealing requirements.

  16. Mechanical and electromagnetic interference shielding Properties of poly(vinyl alcohol)/graphene and poly(vinyl alcohol)/multi-walled carbon nanotube composite nanofiber mats and the effect of Cu top-layer coating.

    PubMed

    Fujimori, Kazushige; Gopiraman, Mayakrishnan; Kim, Han-Ki; Kim, Byoung-Suhk; Kim, Ick-Soo

    2013-03-01

    We report the mechanical property and electromagnetic interference shielding effectiveness (EMI SE) of poly(vinyl alcohol) (PVA)/graphene and PVA/multi-walled carbon nanotube (MWCNT) composite nanofibers prepared by electrospinning. The metal (Cu) was deposited on the resultant PVA composite nanofibers using metal deposition technique in order to improve the mechanical properties and EMI shielding properties. The resulting PVA composite nanofibers and Cu-deposited corresponding nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD). Tensile tests were performed on the PVA/graphene and PVA/MWCNT composite nanofibers. The tensile strength of the PVA/graphene and PVA/MWCNT composite nanofibers was found to be 19.2 +/- 0.3 MPa at graphene content - 6.0 wt% and 12.2 +/- 0.2 MPa at MWCNT content - 3.0 wt%, respectively. The EMI SE of the Cu-deposited PVA/graphene composite nanofibers was significantly improved compared to pure PVA/graphene composite nanofibers, and also depended on the thickness of Cu metal layer deposited on the PVA composite nanofibers. PMID:23755586

  17. Preparation and characterization of wet spun silk fibroin/poly(vinyl alcohol) blend filaments.

    PubMed

    Lee, Ki Hoon; Baek, Doo Hyun; Ki, Chang Seok; Park, Young Hwan

    2007-07-01

    Silk fibroin (SF)/poly(vinyl alcohol) (PVA) blend filaments were prepared by a wet spinning process. Regenerated SF and PVA were dissolved in formic acid and the dope solution exhibited good fiber formation in a methanol coagulation bath. Due to the miscibility of SF/PVA in formic acid, the filament had a smooth surface and dense structure with a circular cross-section. The crystalline structure and thermal properties were varied with different SF/PVA ratios. The mechanical properties of the filament were also controlled by blending PVA with SF. Especially, the knot strength of the SF filament, which is a very important suture property, could be significantly improved by blending with PVA. PMID:17324454

  18. Radiolytic formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix

    NASA Astrophysics Data System (ADS)

    Kumar, Manmohan; Varshney, Lalit; Francis, Sanju

    2005-05-01

    Ag+ ions, in aqueous polyvinyl alcohol (PVA) solution and in PVA hydrogel matrix have been gamma radiolytically reduced to produce Ag clusters. UV-visible absorption spectral characteristics of Ag clusters obtained under different gamma dose, Ag+ concentration, PVA concentration and crosslinking density of the gel used have been studied. The effect of Ag+ ions on the radiation crosslinking of the PVA chains, have also been investigated by viscosity measurements. The radiation-induced Ag+ ion reduction was followed by crosslinking of the PVA chains. PVA was found to be a very efficient stabilizer to prevent aggregation of Ag clusters. The clusters produced in the hydrogel matrix were expected to be smaller than the pore size (∼2-20 nm) of the gels used in the study. These Ag clusters were unable to reduce methyl viologen (MV2+) chloride and were stable in air.

  19. Effect of Al2O3 on crystallinity and conductivity of PVA-PEO-EC-LiCF3SO3 blend electrolyte system

    NASA Astrophysics Data System (ADS)

    Joge, Prajakta N.; Kanchan, D. K.; Sharma, Poonam L.

    2014-04-01

    In the present study, the PVA-PEO-EC-LiCF3SO3 polymer electrolytes are prepared using solution cast technique for different concentrations of Al2O3 ranging from 2 to 10 wt%. The study deals with the investigation of the influence of Al2O3 concentration on the electrical properties and crystallinity of the polymer electrolytes. The conductivity studies are carried out using impedance spectroscopic analysis and the variation in crystallinity is investigated using XRD technique.

  20. Oxidative Mineralization and Characterization of Polyvinyl Alcohol Solutions for Wastewater Treatment

    SciTech Connect

    Oji, L.N.

    2003-08-07

    Photochemical and ultrasonic treatment of polyvinyl alcohol (PVA), derived from PVA fabric material, with hydrogen peroxide was evaluated as a primary method for PVA mineralization into simpler organic molecules. PVA-based waste streams have been found to be compatible with nuclear process wastewater treatment facilities only when solubilized PVA is more than 90 percent mineralized with hydrogen peroxide. No undesirable solid particles are formed with other nuclear process liquid waste when they are mixed, pH adjusted, evaporated and blended with this type of oxidized PVA waste streams. The presence of oxidized PVA in a typical nuclear process wastewater has been found to have no detrimental effect on the efficiency of ion exchange resins, inorganic, and precipitation agents used for the removal of radionuclides from nuclear waste streams. The disappearance of PVA solution in hydrogen peroxide with ultrasonic/ ultraviolet irradiation treatment was characterized by pseudo-first-order reaction kinetics. Radioactive waste contaminated PVA fabric can be solubilized and mineralized to produce processible liquid waste, hence, no bulky solid waste disposal cost can be incurred and the radionuclides can be effectively recovered. Therefore, PVA fabric materials can be considered as an effective substitute for cellulose fabrics that are currently used in radioactive waste decontamination processes.

  1. DIELECTRIC PROPERTIES OF POLYVINYL ALCOHOL, POLY(METHYL METHACRYLATE), POLYVINYL BUTYRAL RESIN AND POLYIMIDE AT LOW TEMPERATURES

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R

    2008-01-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI--Kapton\\textregistered). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45K to 350K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and \\pmma\\ dissolved in toluene have the lowest dielectric losses for temperatures lower than $100\\ \\kelvin$. \\Blx\\ and PI have the smallest spread in their breakdown strength data.

  2. Surface studies of microcrystalline chitosan/poly(vinyl alcohol) mixtures

    NASA Astrophysics Data System (ADS)

    Lewandowska, Katarzyna

    2012-12-01

    In the present study, the surface properties of microcrystalline chitosan (MCCh), poly(vinyl alcohol) (PVA) and MCCh/PVA blends (made from acetic acid solutions with the MCCh concentration ranging from 20% to 80%) have been studied by the tapping-mode atomic force microscopy (AFM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The changes of topography images are considered by determining the root mean square (RMS, Rq) deviation in the image data. For PVA samples, the transition between adjacent lamellae occurs through holes, islands, and bicontinuous structures. The AFM images showed also the lamellar structure of PVA in the blend. The crystalline topography of MCCh/PVA film surface suggests the presence of PVA on the top surface. The FTIR spectra of film blends, in the amide I and II region of MCCh and the hydroxyl stretching bands of PVA have been analyzed. FTIR analysis showed the existence of a weak interaction of the hydroxyl or amino groups of microcrystalline chitosan with hydroxyl groups of PVA.

  3. Facile synthesis of silver nanoparticles-modified PVA/H4SiW12O40 nanofibers-based electrospinning to enhance photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Sui, Chunhong; Li, Chao; Guo, Xiaohong; Cheng, Tiexin; Gao, Yukun; Zhou, Guangdong; Gong, Jian; Du, Jianshi

    2012-07-01

    Regarding poly(vinyl alcohol)/silicotungstic acid (PVA/H4SiW12O40) gel as precursor, the silver nanoparticles (NPs) were selectively deposited on the surface of the PVA/H4SiW12O40 nanofibers by using electrospinning and photoreduction methods. X-ray photoelectron spectroscopy, Fourier transformation infrared spectroscopy, and UV-vis diffuse reflectance spectroscopy were used to affirm the structure and formation of tri-component nanohybrids. Field environmental scanning electron microscope and transmission electron microscopy indicate that the average diameter of silver NPs was changed from 25 nm to 50 nm, with decreasing the relative concentration of SiW12 in the as-electrospun nanofibers. The nanocomposites exhibit excellent photocatalytic activity in degradation of Rhodamine B. This result arises from the synergistic effects and the large specific surface areas of Ag/PVA/H4SiW12O40 tri-component nanohybrids.

  4. Synthesis, characterization, and cytotoxicity of TMC-graft-poly(vinyl alcohol) copolymers.

    PubMed

    Martins, Alessandro F; Bueno, Pedro V A; Follmann, Heveline D M; Nocchi, Samara R; Nakamura, Celso V; Rubira, Adley F; Muniz, Edvani C

    2013-11-15

    N-trimethyl chitosan-graft-poly(vinyl alcohol) (TMC-g-PVA) copolymers were prepared. The grafting reactions were conducted in water changing the feed ratios of poly(vinyl alcohol)/6-O-succinate-N-trimethyl chitosan (PVA/STMC). The structure of TMC-g-PVA copolymers was characterized through (1)H NMR spectroscopy, thermogravimetric analysis (TGA/DTG), wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). The quaternization degree (DQ) and substitution degree (DS) of N-trimethyl chitosan (TMC) and 6-O-succinate-N-trimethyl chitosan (STMC) were determined by (1)H NMR, being the spectroscopy 14.0 and 5.5mol-% found, respectively. The viability of HCT-116 cancerous cells was investigated at different concentrations. The effect of PVA/STMC ratios on the cytotoxicity of the TMC-g-PVA copolymers was examined and the CC50 values determined for every case. PMID:23290305

  5. Interfacial Behavior of Polymer Coated Nanoparticle

    NASA Astrophysics Data System (ADS)

    Qi, Luqing; Shamsijazeyi, Hadi; Mann, Jason; Verduzco, Rafael; Hirasaki, George; Rice University Team

    2015-03-01

    Oxidized carbon black (OCB) nanoparticle is functionalized with different coatings, i.e. alkyl group, polyvinyl alcohol (PVA) and partially sulfonated polyvinyl alcohol (sPVA). In oil and water systems, the functionalized nanoparticle is found to have a versatile dispersion i.e. in lower aqueous phase, in upper oil phase, or in middle phase microemulsion. Oil substitute n-octane and commercial oil IOSPAR have been test as oil phase; series of commercially available surfactant, C12-4,5 orthoxylene sulfonate(OXS), i-C13-(PO)7 -SO4Na (S13B), surfactant blend of anionic Alfoterra with nonionic Tergitol have been test as additive to help with the OCB dispersion. It is found that the OCB with sulfonated polyvinyl alcohol attachment (sPVA-OCB) stays in microemulsion; with the increase of salinity, it follows the microemulsion to go from lower phase, to middle phase, and to upper phase. The dispersion of sPVA and alkyl functionalized OCB (Cn-OCB-sPVA) is the balance of the length of alkyl and sPVA and the degree of sulfonation of PVA, depending on which, it can either disperse into microemulsion or form a separate layer. The sPVA-OCB also indicates a tolerance of high salinity; this is shown by the stable dispersion of it in blend surfactant solution of anionic Alfoterra and nonionic Tergitol at high salinity API brine(8% NaCl and 2% CaCl2). The study of different functionality on OCB dispersion can help design appropriate modified nanoparticle as additive for enhanced oil recovery either to reduce the interfacial tension between oil and water, or to stabilize microemulsion.

  6. Synthesis of fast response crosslinked PVA-g-NIPAAm nanohydrogels by very low radiation dose in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Fathi, Marziyeh; Reza Farajollahi, Ali; Akbar Entezami, Ali

    2013-05-01

    Nanohydrogels of poly(vinyl alcohol)-g-N-isopropylacrylamide (PVA-g-NIPAAm) are synthesized by PVA and NIPAAm dilute aqueous solution using much less radiation dose of 1-20 Gy via intramolecular crosslinking at ambient temperature. The radiation synthesis of nanohydrogels is performed in the presence of tetrakis (hydroxymethyl) phosphonium chloride (THPC) due to its rapid oxygen scavenging abilities and hydrogen peroxide (H2O2) as a source of hydroxyl radicals. The effect of radiation dose, feed composition ratio of PVA and H2O2 is investigated on swelling properties such as temperature and pH dependence of equilibrium swelling ratio as well as deswelling kinetics. Experimental data exhibit high equilibrium swelling ratio and fast response time for the synthesized nanohydrogels. The average molecular weight between crosslinks (Mc) and crosslinking density (ρx) of the obtained nanohydrogels are calculated from swelling data as a function of radiation dose, H2O2 and PVA amount. Fourier transform infrared spectroscopy (FT-IR), elemental analysis of nitrogen content and thermogravimetric analysis (TGA) are used to confirm the grafting reaction. Lower critical solution temperature (LCST) is measured around 33 °C by differential scanning calorimetry (DSC) for PVA-g-NIPAAm nanohydrogels. Dynamic light scattering (DLS) data demonstrate that the increase of radiation dose leads to the decreasing in dimension of nanohydrogels. Also, rheological studies are confirmed an improvement in the mechanical properties of the nanohydrogels with increasing the radiation dose. A cytotoxicity study exhibits a good biocompatibility for the obtained nanohydrogels. The prepared nanohydrogels show fast swelling/deswelling behavior, high swelling ratio, dual sensitivity and good cytocompatibility, which may find potential applications as biomaterial.

  7. Controllable promotion of chondrocyte adhesion and growth on PVA hydrogels by controlled release of TGF-β1 from porous PLGA microspheres.

    PubMed

    Nie, Lei; Zhang, Guohua; Hou, Ruixia; Xu, Haiping; Li, Yaping; Fu, Jun

    2015-01-01

    Poly(vinyl alcohol) (PVA) hydrogels have been candidate materials for cartilage tissue engineering. However, the cell non-adhesive nature of PVA hydrogels has been a limit. In this paper, the cell adhesion and growth on PVA hydrogels were promoted by compositing with transform growth factor-β1 (TGF-β1) loaded porous poly(D,L-lactide-co-glycolide) (PLGA) microspheres. The porous microspheres were fabricated by a modified double emulsion method with bovine serum albumin (BSA) as porogen. The average pore size of microspheres was manipulated by changing the BSA/PLGA ratio. Such controllable porous structures effectively influenced the encapsulation efficiency (Eencaps) and release profile of TGF-β1. By compositing PVA hydrogels with such TGF-β1-loaded PLGA microspheres, chondrocyte adhesion and proliferation were significantly promoted in a controllable manner, as confirmed by fluorescent imaging and quantitative CCK-8 assay. That is, the chondrocyte proliferation was favored by using PLGA microspheres with high Eencaps of TGF-β1 or by increasing the PLGA microsphere content in the hydrogels. These results demonstrated a facile method to improve the cell adhesion and growth on the intrinsically cell non-adhesive PVA hydrogels, which may find applications in cartilage substitution. PMID:25437063

  8. Fabrication of Li2TiO3 pebbles using PVA-boric acid reaction for solid breeding materials

    NASA Astrophysics Data System (ADS)

    Park, Yi-Hyun; Cho, Seungyon; Ahn, Mu-Young

    2014-12-01

    Lithium metatitanate (Li2TiO3) is a candidate breeding material of the Helium Cooled Ceramic Reflector (HCCR) Test Blanket Module (TBM). The breeding material is used in pebble-bed form to reduce the uncertainty of the interface thermal conductance. In this study, Li2TiO3 pebbles were successfully fabricated by the slurry droplet wetting method using the cross-linking reaction between polyvinyl alcohol (PVA) and boric acid. The effects of fabrication parameters on the shaping of Li2TiO3 green body were investigated. In addition, the basic characteristics of the sintered pebble were also evaluated. The shape of Li2TiO3 green bodies was affected by slurry viscosity, PVA content and boric acid content. The grain size and average crush load of sintered Li2TiO3 pebble were controlled by the sintering time. The boron was completely removed during the final sintering process.

  9. Application of argon laser beam diffraction for determination of the properties of photoinduced processes in dyed PVA foils

    NASA Astrophysics Data System (ADS)

    Planner, Alfons; Runka, Tomasz; Skrzypczak, A.; Hara, M.; Miyake, J.

    2000-11-01

    It is shown that far field patterns of argon laser beam interacting with dyed foil of polyvinyl alcohol (PVA) provide information on the mechanism of local foil discoloration or at least on a few properties of this process. In particular far field patterns observations allow discernment if the process is reversible (or a superposition of reversible and irreversible processes), photothermal, photochemical or produce a stretching in sample (photoizomerisation). The effect was studied in PVA foil containing methyl red, photosynthetic bacteria, their fragments and pigments. Apart from indicating the possibility of using the far field patterns for discernment of the foil discoloration mechanisms, the results reported point to the perspectives of using the foil for laser beam modification, shift or modulation, as well as elements of optical memory.

  10. Facile synthesis of acid-labile polymers with pendent ortho esters.

    PubMed

    Cheng, Jing; Ji, Ran; Gao, Shi-Juan; Du, Fu-Sheng; Li, Zi-Chen

    2012-01-01

    This work presents a facile approach for preparation of acid-labile and biocompatible polymers with pendent cyclic ortho esters, which is based on the efficient and mild reactions between cyclic ketene acetal (CKA) and hydroxyl groups. Three CKAs, 2-ethylidene-1,3-dioxane (EDO), 2-ethylidene-1,3-dioxolane (EDL), and 2-ethylidene-4- methyl-1,3-dioxolane (EMD) were prepared from the corresponding cyclic vinyl acetals by catalytic isomerization of the double bond. The reaction of CKAs with different alcohols and diols was examined using trace of p-toluenesulfonic acid as a catalyst. For the monohydroxyl alcohols, cyclic ortho esters were formed by simple addition of the hydroxyl group toward CKAs with ethanol showing a much greater reactivity than iso-propanol. When 1,2- or 1,3-diols were used to react with the CKAs, we observed the isomerized cyclic ortho esters besides the simple addition products. Biocompatible polyols, that is, poly(2-hydroxyethyl acrylate) (PHEA) and poly(vinyl alcohol) (PVA) were then modified with CKAs, and the degree of substitution of the pendent ortho esters can be easily tuned by changing feed ratio. Both the small molecule ortho esters and the CKA-modified polymers demonstrate the pH-dependent hydrolysis profiles, which depend also on the chemical structure of the ortho esters as well as the polymer hydrophobicity. PMID:22176024

  11. Isothermal Dendritic Growth Experiment - PVA Dendrites

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Isothermal Dendritic Growth Experiment (IDGE), flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relevant metal and alloy forming operations. IDGE used transparent organic liquids that form dendrites (treelike structures) similar to those inside metal alloys. Comparing Earth-based and space-based dendrite growth velocity, tip size and shape provides a better understanding of the fundamentals of dentritic growth, including gravity's effects. Shalowgraphic images of pivalic acid (PVA) dendrites forming from the melt show the subtle but distinct effects of gravity-driven heat convection on dentritic growth. In orbit, the dendrite grows as its latent heat is liberated by heat conduction. This yields a blunt dendrite tip. On Earth, heat is carried away by both conduction and gravity-driven convection. This yields a sharper dendrite tip. In addition, under terrestrial conditions, the sidebranches growing in the direction of gravity are augmented as gravity helps carry heat out of the way of the growing sidebranches as opposed to microgravity conditions where no augmentation takes place. IDGE was developed by Rensselaer Polytechnic Institute and NASA/Glenn Research Center. Advanced follow-on experiments are being developed for flight on the International Space Station. Photo Credit: NASA/Glenn Research Center

  12. Macroporous molecularly imprinted polymer/cryogel composite systems for the removal of endocrine disrupting trace contaminants.

    PubMed

    Le Noir, Mathieu; Plieva, Fatima; Hey, Tobias; Guieysse, Benoit; Mattiasson, Bo

    2007-06-22

    A new concept for the preparation of selective sorbents with high flow path properties is presented by embedding molecularly imprinted polymers (MIPs) into various macroporous gels (MGs). A MIP was first synthetized with 17beta-estradiol (E2) as template for the selective adsorption of this endocrine disrupter. The composite macroporous gel/MIP (MG/MIP) monoliths were then prepared at subzero temperatures. Complete recovery of E2 from a 2 microg/L aqueous solution was achieved using the polyvinyl alcohol (PVA) MG/MIP monoliths whereas only 49-74% was removed with non-imprinted polymers (when no template was used). The PVA MG/MIP monolith columns were operated at almost 10 times higher flow rate (50 mL/min) compared to the MIP columns with operation flow rate of 1-5 mL/min. The possibility for processing the particulate containing wastewater effluents at high flow rates with selectivity on E2 removal, as well as the easy preparation of the monoliths, make the macroporous MG/MIP systems attractive and robust sorbents for the clean up of water from endocrine disrupting trace contaminants. PMID:17449053

  13. Thermoporometry and impedance analysis to study dynamics of water and polymer present in hydrogel.

    PubMed

    Selestin Raja, I; Nishad Fathima, Nishter

    2015-01-01

    Though various conventional methods are available to explore hydrogels, they have drawbacks such as analysis in solid state and failure to give insights into individual components of hydrogel viz. water (dispersion medium) and hydrophilic polymers (dispersed phase). The combined study of porosity and dielectric nature of hydrogel succeeds, in this context, as it investigates both the components individually. In this study, we have taken well-known hydrogel system gelatin-polyvinyl alcohol (PVA) cross linked with genipin. Thermoporometry has been used to investigate the state of water and porosity whereas Alternative Current (AC) impedance analysis has been used to study about nature of polymers through dielectric properties in hydrogel. The influence of physic-chemical properties was examined with SEM and in vitro drug release using catechin. The study revealed that increasing concentration of PVA to gelatin has retained excessive bound water molecules exhibiting high polarity in each polymeric component. Further, it is shown that reduction in pore size and high reactivity with drug molecules have led to lower initial release and increase total amount of release. We conclude that non-conventional methods such as thermoporometry and AC impedance analysis yield more valuable information about hydrogel, which can aid in designing appropriate biomaterial for intended drug release. PMID:25199869

  14. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions.

    PubMed

    Zhou, Ling; He, Hui; Li, Mei-Chun; Song, Kunlin; Cheng, H N; Wu, Qinglin

    2016-11-20

    The present work describes the isolation of cellulose nanoparticles (CNs) with different morphologies and their influence on rheological properties of CN and CN-poly (vinyl alcohol) (PVA) suspensions. Cottonseed hulls were used for the first time to extract three types of CNs, including fibrous cellulose nanofibers, rod-like cellulose nanocrystals and spherical cellulose nanoparticles through mechanical and chemical methods. Rheology results showed that the rheological behavior of the CN suspensions was strongly dependent on CN concentration and particle morphology. For PVA/CN systems, concentration of PVA/CN suspension, morphology of CNs, and weight ratio of CN to PVA were three main factors that influenced their rheology behaviors. This research reveals the importance of CN morphology and composition concentration on the rheological properties of PVA/CN, providing new insight in preparing high performance hydrogels, fibers and films base on PVA/CN suspension systems. PMID:27561516

  15. X-ray photoelectron spectroscopy studies of bond structure between polyvinyl alcohol and a titanate cross-coupling agent

    SciTech Connect

    Guelguen, M.A.; Popoola, O.O.; Kriven, W.M.

    1995-06-01

    Chemical interactions between polyvinyl alcohol (PVA) and triethanol amine titanate chelate were studied using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The titanate chelate cross coupled the PVA solution and produced a viscous gel. The gel had a three- dimensional network structure containing --C{sub PVA}--O--Ti--O--C{sub PVA}--organic complexes. A new C(1{ital s}) signature at 285.7 eV and an O(1{ital s}) signature at 531.25 eV were associated with the formation of these complexes. The water of the PVA solution was physically retained in the gelled structure and was readily available for chemical reactions. The removal of this entrapped water was irreversible and lead to a collapsed film of Ti-cross-linked PVA.

  16. Production of polyvinyl alcohol-degrading enzyme with Janthinobacterium sp. and its application in cotton fabric desizing.

    PubMed

    Du, Guocheng; Liu, Liming; Song, Zhaoxia; Hua, Zhaozhe; Zhu, Yang; Chen, Jian

    2007-06-01

    A strain capable of using polyvinyl alcohol (PVA) as sole carbon source was isolated from soil samples of a textile factory. The 16S rDNA sequence analysis cell morphology, physiology and biochemistry showed that it belonged to Janthinobacterium sp. This is the first report to show that the screened Janthinobacterium sp. could degrade PVA. The optimum nutritional and environmental conditions for PVA-degrading enzyme production by Janthinobacterium sp. were investigated by single-factor tests. Under optimized nutritional and environmental condition in shake flasks, PVA-degrading enzyme reached 5.12 U/mL at 21 h. With PVA-degrading enzyme produced by Janthinobacterium sp. WSH04-01, 80% of PVA could be degraded from cotton fabrics in 3 h. PMID:17345576

  17. Structure evolution and optimization in the fabrication of PVA-based activated carbon fibers.

    PubMed

    Zhang, Shu-Juan; Feng, Hui-Min; Wang, Jian-Ping; Yu, Han-Qing

    2008-05-01

    The structure and composition evolution of polyvinyl alcohol (PVA) fibers during the fabrication of activated carbon fibers (ACF) by a newly developed method were systematically elucidated. The pore structure of the fibers was significantly influenced by the carbonization and activation conditions. The elemental composition and chemical structure evolution of the fibers during the heat treatment processes were evaluated by elemental analysis, Fourier transform infrared spectrophotometry (FTIR), and X-ray photoelectron spectroscopy (XPS). Crystal structure evolution of the fibers during the heat treatment processes was elucidated by X-ray diffraction (XRD) analysis. Based on these understandings, the process conditions were optimized using an L(9)(3)(4) orthogonal array design matrix. Appropriate process parameters for the fabrication of PVA-ACFs were established as carbonizing the dehydrated fiber at 300 degrees C for 60 min, and then lifting the temperature to 900 degrees C with a heating speed of 10 degrees C/min in an inert atmosphere, thereafter keeping the fiber at 900 degrees C for 60 min in an oxidizing atmosphere. PMID:18261741

  18. Preparation and rheological studies of uncoated and PVA-coated magnetite nanofluid

    NASA Astrophysics Data System (ADS)

    Khosroshahi, M. E.; Ghazanfari, L.

    2012-12-01

    Experimental studies of rheological behavior of uncoated magnetite nanoparticles (MNPs)U and polyvinyl alcohol (PVA) coated magnetite nanoparticles (MNPs)C were performed. A Co-precipitation technique under N2 gas was used to prevent undesirable critical oxidation of Fe2+. The results showed that smaller particles can be synthesized in both cases by decreasing the NaOH concentration which in our case this corresponded to 35 nm and 7 nm using 0.9 M NaOH at 750 rpm for (MNPs)U and (MNPs)C. The stable magnetic fluid contained well-dispersed Fe3O4/PVA nanocomposites which indicated fast magnetic response. The rheological measurement of magnetic fluid indicated an apparent viscosity range (0.1-1.2) pa s at constant shear rate of 20 s-1 with a minimum value in the case of (MNPs)U at 0 T and a maximum value for (MNPs)C at 0.5 T. Also, as the shear rate increased from 20 s-1 to 150 s-1 at constant magnetic field, the apparent viscosity also decreased correspondingly. The water-based ferrofluid exhibited the non-Newtonian behavior of shear thinning under magnetic field.

  19. Development of composite membranes of PVA-TEOS doped KOH for alkaline membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Haryadi, Sugianto, D.; Ristopan, E.

    2015-12-01

    Anion exchange membranes (AEMs) play an important role in separating fuel and oxygen (or air) in the Alkaline Membrane Fuel Cells. Preparation of hybrid organic inorganic materials of Polyvinylalcohol (PVA) - Tetraethylorthosilicate (TEOS) composite membrane doped KOH for direct alcohol alkaline fuel cell application has been investigated. The sol-gel method has been used to prepare the composite membrane of PVA-TEOS through crosslinking step and catalyzed by concentrated of hydrochloric acid. The gel solution was cast on the membrane plastic plate to obtain membrane sheets. The dry membranes were then doped by immersing in various concentrations of KOH solutions for about 4 hours. Investigations of the cross-linking process and the presence of hydroxyl group were conducted by FTIR as shown for frequency at about 1600 cm-1 and 3300 cm-1 respectively. The degree of swelling in ethanol decreased as the KOH concentration for membrane soaking process increased. The ion exchange capacity (IEC) of the membrane was 0.25meq/g. This composite membranes display significant ionic conductivity of 3.23 x 10-2 S/cm in deionized water at room temperature. In addition, the morphology observation by scanning electron microscope (SEM) of the membrane indicates that soaking process of membrane in KOH increased thermal resistant.

  20. Development of composite membranes of PVA-TEOS doped KOH for alkaline membrane fuel cell

    SciTech Connect

    Haryadi, Sugianto, D.; Ristopan, E.

    2015-12-29

    Anion exchange membranes (AEMs) play an important role in separating fuel and oxygen (or air) in the Alkaline Membrane Fuel Cells. Preparation of hybrid organic inorganic materials of Polyvinylalcohol (PVA) - Tetraethylorthosilicate (TEOS) composite membrane doped KOH for direct alcohol alkaline fuel cell application has been investigated. The sol-gel method has been used to prepare the composite membrane of PVA-TEOS through crosslinking step and catalyzed by concentrated of hydrochloric acid. The gel solution was cast on the membrane plastic plate to obtain membrane sheets. The dry membranes were then doped by immersing in various concentrations of KOH solutions for about 4 hours. Investigations of the cross-linking process and the presence of hydroxyl group were conducted by FTIR as shown for frequency at about 1600 cm{sup −1} and 3300 cm{sup −1} respectively. The degree of swelling in ethanol decreased as the KOH concentration for membrane soaking process increased. The ion exchange capacity (IEC) of the membrane was 0.25meq/g. This composite membranes display significant ionic conductivity of 3.23 x 10{sup −2} S/cm in deionized water at room temperature. In addition, the morphology observation by scanning electron microscope (SEM) of the membrane indicates that soaking process of membrane in KOH increased thermal resistant.

  1. Swelling, mechanical and friction properties of PVA/PVP hydrogels after swelling in osmotic pressure solution.

    PubMed

    Shi, Yan; Xiong, Dangsheng; Liu, Yuntong; Wang, Nan; Zhao, Xiaoduo

    2016-08-01

    The potential of polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) hydrogels as articular cartilage replacements was in vitro evaluated by using a macromolecule-based solution to mimic the osmotic environment of cartilage tissue. The effects of osmotic pressure solution on the morphology, crystallinity, swelling, mechanical and friction properties of PVA/PVP hydrogels were investigated by swelling them in non-osmotic and osmotic pressure solutions. The results demonstrated that swelling ratio and equilibrium water content were greatly reduced by swelling in osmotic solution, and the swelling process was found to present pseudo-Fickian diffusion character. The crystallization degree of hydrogels after swelling in osmotic solution increased more significantly when it compared with that in non-osmotic solution. After swelling in osmotic solution for 28days, the compressive tangent modulus and storage modulus of hydrogels were significantly increased, and the low friction coefficient was reduced. However, after swelling in the non-osmotic solution, the compressive tangent modulus and friction coefficient of hydrogels were comparable with those of as-prepared hydrogels. The better material properties of hydrogels in vivo than in vitro evaluation demonstrated their potential application in cartilage replacement. PMID:27157740

  2. Preparation of silver-hydroyapatite/PVA nanocomposites: Giant dielectric material for industrial and clinical applications

    NASA Astrophysics Data System (ADS)

    Uddin, Md Jamal; Middya, T. R.; Chaudhuri, B. K.

    2015-02-01

    Pure hydroxyappatite Ca10(PO4)6(OH)2 (or HAP) was prepared from eggshell and potassium dihydrogen phosphate (KH2PO4) by a simple self-chemical reaction method. The clean eggshell was heated at 800 °C in air giving the source of CaO. Appropriate amount of CaO was dissolved in KH2PO4 solution at 37°C for few days. The PH value decreases with increasing the duration of preparation of HAP. Silver nanoparticles derived from silver nitrate solution using black tea leaf extract had been introduced to hydroxyapatite due to its biocompatibility. The unique size- dependent properties of nanomaterials make them superior and indispensable. In this work, hydroxyapatite-silver nanoparticles/polyvinyl alcohol (PVA) composites with 4 different concentrations of hydroxyapatite (1-4 wt %) were prepared by bio-reduction method. Several techniques like XRD and SEM were used to characterize the prepared samples. Frequency dependent capacitance and conductance of the samples were measured using an impedance analyzer. The results showed a remarkable increase in dielectric permittivity (~5117) with low loss (~0.23) at1000 HZ and room temperature (300K) for 4wt% Hydroxapatie-Silver/PVA nanocomposite. Such nanocomposite might be directly applied in manufacturing clinical devices and also for embedding capacitor applications.

  3. Electrospinning of PVA/chitosan nanocomposite nanofibers containing gelatin nanoparticles as a dual drug delivery system.

    PubMed

    Fathollahipour, Shahrzad; Abouei Mehrizi, Ali; Ghaee, Azadeh; Koosha, Mojtaba

    2015-12-01

    Nanofibrous core-sheath nanocomposite dual drug delivery system based on poly(vinyl alcohol) (PVA)/chitosan/lidocaine hydrochloride loaded with gelatin nanoparticles were successfully prepared by the electrospinning method. Gelatin nanoparticles were prepared by nanoprecipitation and were then loaded with erythromycin antibiotic agent with the average particle size of ∼175 nm. The morphology of gelatin nanoparticles observed by field emission scanning electron microscopy (FE-SEM) was shown to be optimal at the concentration of 1.25 wt % of gelatin in aqueous phase by addition of 20 µL of glutaraldehyde 5% as the crosslinking agent. The nanoparticles were also characterized by dynamic light scattering, zeta potential measurement, and Fourier transform infrared spectroscopy (FTIR). The best bead free morphology for the PVA/chitosan nanofibrous mats were obtained at the solution weight ratio of 96/4. The nanofibrous mats were analyzed by swelling studies, FTIR and antibacterial tests. In vitro dual release profile of the core-sheath nanofibers was also studied within 72 h and showed the release efficiency equal to 84.69 and 75.13% for lidocaine hydrochloride and erythromycin, respectively. According to release exponent n, the release of lidocaine hydrochloride from the sheath part of the matrix is quasi-Fickian diffusion mechanism, while the release of erythromycin is based on anomalous or non-Fickian mechanisms. PMID:26112829

  4. PVA bio-nanocomposites: a new take-off using cellulose nanocrystals and PLGA nanoparticles.

    PubMed

    Rescignano, N; Fortunati, E; Montesano, S; Emiliani, C; Kenny, J M; Martino, S; Armentano, I

    2014-01-01

    The formation of a new generation of hybrid bio-nanocomposites is reported: these are intended at modulating the mechanical, thermal and biocompatibility properties of the poly(vinyl alcohol) (PVA) by the combination of cellulose nanocrystals (CNC) and poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) loaded with bovine serum albumin fluorescein isothiocynate conjugate (FITC-BSA). CNC were synthesized from microcrystalline cellulose by hydrolysis, while PLGA nanoparticles were produced by a double emulsion with subsequent solvent evaporation. Firstly, binary bio-nanocomposites with different CNC amounts were developed in order to select the right content of CNC. Next, ternary PVA/CNC/NPs bio-nanocomposites were developed. The addition of CNC increased the elongation properties without compromising the other mechanical responses. Thermal analysis underlined the nucleation effect of the synergic presence of cellulose and nanoparticles. Remarkably, bio-nanocomposite films are suitable to vehiculate biopolymeric nanoparticles to adult bone marrow mesenchymal stem cells successfully, thus representing a new tool for drug delivery strategies. PMID:24274478

  5. Preparation and Thermal Analysis of Ferric Doped PVA-PVP-PPy Composite Films

    NASA Astrophysics Data System (ADS)

    Patil, Ravikumar V.; Ranganath, M. R.; Lobo, Blaise

    2011-12-01

    The preparation and thermal analysis of flexible blend films of pyrrole (Py) polymerized in aqueous solution of poly (vinyl alcohol) (PVA) and poly (vinyl pyrrolidone) (PVP) is described. In-situ polymerization of pyrrole in aqueous solution of PVA and PVP containing ferric chloride (FeCl3) was achieved through vapor sorption, and the films obtained were studied using Differential Scanning Calorimetry (DSC), Thermo-Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA). No melting endotherm is seen in the DSC and DTA scans of the composite films, indicating that the sample is amorphous. Degradation of the sample is found to occur at lower temperatures, with increase in doping level (wt% of FeCl3). DSC study was performed between 40 °C and 400 °C. Below 1.2 wt % DL, degradation of the sample occurs in two stages, the first at 310 °C and the second at 440 °C, as seen from DTA and TGA scans. The broad endotherm between 80 °C and 120 °C is due to volatization of moisture (water) absorbed by the sample. Multiple endotherms are observed in DSC and DTA scans of the composite films, for FeCl3 doping levels above 3.8 wt %, and the sample degrades in many different stages at lower temperature, with increase in doping level, as revealed by weight losses in the TGA curve.

  6. Design of freeze-dried Soluplus/polyvinyl alcohol-based film for the oral delivery of an insoluble drug for the pediatric use.

    PubMed

    Shamma, Rehab; Elkasabgy, Nermeen

    2016-01-01

    Spironolactone (SL) is a poorly water-soluble drug. Being poorly soluble affects its dissolution rate which in turn affects its oral bioavailability. This work aimed to prepare freeze-dried SL-Soluplus/polyvinyl alcohol (PVA) oral thin film in an attempt to enhance the drug solubility on one hand and at the same time prepare a solid dosage form convenient for the pediatric use. SL-Soluplus/PVA films were prepared using polyethylene glycol 400 (PEG 400) as a plasticizer applying the solvent-casting technique. The prepared films were evaluated for their thickness, tensile strength, and in vitro dissolution studies. Box-Behnken design (17 runs) was applied to optimize the effects of the formulation variables on the film properties. The optimized film formulation was freeze-dried after casting so as to enhance the drug dissolution. Moreover, the optimized freeze-dried film was re-characterized in vitro and evaluated in vivo in human volunteers to investigate its palatability and satisfaction. The results showed that the optimized formulation composed of 10% polymer concentration containing Soluplus:PVA (0.33:0.66) and plasticized with 30% PEG 400 possessed the highest desirability value (0.836). Freeze-drying of the optimized formulation succeeded to improve SL in vitro dissolution due to the preparation of a more porous film compared to the non-freeze-dried one. In vivo evaluation of the optimized freeze-dried film showed high satisfaction among the participating volunteers concerning the ease of administration and sensation thereafter, where all the film specimens dissolved without the need for water and no film residues remained in the mouth following film dissolution. In conclusion, freeze-dried Soluplus®/PVA-based oral thin film proved to be a successful carrier for the oral delivery of insoluble drugs like SL for pediatrics. PMID:24892631

  7. Electrospun chitosan/polyvinyl alcohol nanofibre mats for wound healing.

    PubMed

    Charernsriwilaiwat, Natthan; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Opanasopit, Praneet

    2014-04-01

    Chitosan (CS) aqueous salt blended with polyvinyl alcohol (PVA) nanofibre mats was prepared by electrospinning. CS was dissolved with hydroxybenzotriazole (HOBt), thiamine pyrophosphate (TPP) and ethylenediaminetetraacetic acid (EDTA) in distilled water without the use of toxic or hazardous solvents. The CS aqueous salts were blended with PVA at different weight ratios, and the effect of the solution ratios was investigated. The morphologies and mechanical and swelling properties of the generated fibres were analysed. Indirect cytotoxicity studies indicated that the CS/PVA nanofibre mats were non-toxic to normal human fibroblast cells. The CS-HOBt/PVA and CS-EDTA/PVA nanofibre mats demonstrated satisfactory antibacterial activity against both gram-positive and gram-negative bacteria, and an in vivo wound healing test showed that the CS-EDTA/PVA nanofibre mats performed better than gauze in decreasing acute wound size during the first week after tissue damage. In conclusion, the biodegradable, biocompatible and antibacterial CS-EDTA/PVA nanofibre mats have potential for use as wound dressing materials. PMID:22925275

  8. Functionalized graphene oxide quantum dot-PVA hydrogel: a colorimetric sensor for Fe2+, Co2+ and Cu2+ ions

    NASA Astrophysics Data System (ADS)

    Baruah, Upama; Chowdhury, Devasish

    2016-04-01

    Functionalized graphene oxide quantum dots (GOQDs)-poly(vinyl alcohol) (PVA) hybrid hydrogels were prepared using a simple, facile and cost-effective strategy. GOQDs bearing different surface functional groups were introduced as the cross-linking agent into the PVA matrix thereby resulting in gelation. The four different types of hybrid hydrogels were prepared using graphene oxide, reduced graphene oxide, ester functionalized graphene oxide and amine functionalized GOQDs as cross-linking agents. It was observed that the hybrid hydrogel prepared with amine functionalized GOQDs was the most stable. The potential applicability of using this solid sensing platform has been subsequently explored in an easy, simple, effective and sensitive method for optical detection of M2+ (Fe2+, Co2+ and Cu2+) in aqueous media involving colorimetric detection. Amine functionalized GOQDs-PVA hybrid hydrogel when put into the corresponding solution of Fe2+, Co2+ and Cu2+ renders brown, orange and blue coloration respectively of the solution detecting the presence of Fe2+, Co2+ and Cu2+ ions in the solution. The minimum detection limit observed was 1 × 10-7 M using UV-visible spectroscopy. Further, the applicability of the sensing material was also tested for a mixture of co-existing ions in solution to demonstrate the practical applicability of the system. Insight into the probable mechanistic pathway involved in the detection process is also being discussed.

  9. Amperometric catechol biosensor based on laccase immobilized on nitrogen-doped ordered mesoporous carbon (N-OMC)/PVA matrix

    NASA Astrophysics Data System (ADS)

    Guo, Meiqing; Wang, Hefeng; Huang, Di; Han, Zhijun; Li, Qiang; Wang, Xiaojun; Chen, Jing

    2014-06-01

    A functionalized nitrogen-containing ordered mesoporous carbon (N-OMC), which shows good electrical properties, was synthesized by the carbonization of polyaniline inside a SBA-15 mesoporous silica template. Based on this, through entrapping laccase onto the N-OMC/polyvinyl alcohol (PVA) film a facilely fabricated amperometric biosensor was developed. Laccase from Trametes versicolor was assembled on a composite film of a N-OMC/PVA modified Au electrode and the electrochemical behavior was investigated. The results indicated that the N-OMC modified electrode exhibits electrical properties towards catechol. The optimum experimental conditions of a biosensor for the detection of catechol were studied in detail. Under the optimal conditions, the sensitivity of the biosensor was 0.29 A*M-1 with a detection limit of 0.31 μM and a linear detection range from 0.39 μM to 8.98 μM for catechol. The calibration curve followed the Michaelis-Menten kinetics and the apparent Michaelis-Menten \\left( K_{M}^{app} \\right) was 6.28 μM. This work demonstrated that the N-OMC/PVA composite provides a suitable support for laccase immobilization and the construction of a biosensor.

  10. Encapsulation and immobilization of papain in electrospun nanofibrous membranes of PVA cross-linked with glutaraldehyde vapor.

    PubMed

    Moreno-Cortez, Iván E; Romero-García, Jorge; González-González, Virgilio; García-Gutierrez, Domingo I; Garza-Navarro, Marco A; Cruz-Silva, Rodolfo

    2015-01-01

    In this paper, papain enzyme (E.C. 3.4.22.2, 1.6 U/mg) was successfully immobilized in poly(vinyl alcohol) (PVA) nanofibers prepared by electrospinning. The morphology of the electrospun nanofibers was characterized by scanning electron microscopy (SEM) and the diameter distribution was in the range of 80 to 170 nm. The presence of the enzyme within the PVA nanofibers was confirmed by infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS) analyses. The maximum catalytic activity was reached when the enzyme loading was 13%. The immobilization of papain in the nanofiber membrane was achieved by chemical crosslinking with a glutaraldehyde vapor treatment (GAvt). The catalytic activity of the immobilized papain was 88% with respect to the free enzyme. The crosslinking time by GAvt to immobilize the enzyme onto the nanofiber mat was 24h, and the enzyme retained its catalytic activity after six cycles. The crosslinked samples maintained 40% of their initial activity after being stored for 14 days. PVA electrospun nanofibers are excellent matrices for the immobilization of enzymes due to their high surface area and their nanoporous structure. PMID:25953572

  11. 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...

  12. Alcoholism and Alcohol Abuse

    MedlinePlus

    ... This means that their drinking causes distress and harm. It includes alcoholism and alcohol abuse. Alcoholism, or ... brain, and other organs. Drinking during pregnancy can harm your baby. Alcohol also increases the risk of ...

  13. Diffraction efficiency improvement in high spatial frequency holographic gratings stored in PVA/AA photopolymers: several ACPA concentrations

    NASA Astrophysics Data System (ADS)

    Fernandez, Elena; Fuentes, Rosa; Ortuño, Manuel; Beléndez, Augusto; Pascual, Inmaculada

    2015-01-01

    High spatial frequency in holographic gratings is difficult to obtain due to limitations of the recording material. In this paper, the results obtained after storing holographic transmission gratings with a spatial frequency of 2656 lines/mm in a material based on polyvinyl alcohol and acrylamide (PVA/AA) are presented. A chain transfer agent, 4, 4‧-azobis (4-cyanopentanoic acid) (ACPA) was incorporated in the composition of the material to improve the response of the material at a high spatial frequency. Different concentrations of ACPA were used in order to find the optimal concentration giving maximum diffraction efficiency for high spatial frequencies.

  14. 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. PMID:23399282

  15. Mechanisms of diphylline release from dual-solute loaded poly(vinyl alcohol) matrices.

    PubMed

    Hasimi, Albana; Papadokostaki, Kyriaki G; Sanopoulou, Merope

    2014-01-01

    The release kinetics of the model hydrophilic drug, diphylline (DPL), from physically crosslinked poly(vinyl alcohol) (PVA) matrices, is studied in relation to the drug load and the presence of a second solute incorporated in the matrix. The second solute, a gadolinium (III) complex (Gd-DTPA), is a commonly used MRI contrast agent. The water uptake kinetics by the glassy PVA matrix was found to deviate from t(1/2) law and to occur on time scales comparable to those of diphylline release. The corresponding rate of diphylline release was found to be substantially stabilized as compared to a purely diffusion-controlled release process, in line with theoretical predictions under conditions of relaxation-controlled water uptake kinetics. The release rate of DPL was found (i) to increase with increasing DPL load and (ii) for a particular DPL load, to increase in the presence of Gd-DTPA, incorporated in the matrix. The results were interpreted on the basis of the diphylline-induced plasticization of the polymer (evidenced by the depression of Tg) and of the excess hydration of the matrix at high solute loads. The latter effect was found to be additive in the case of dual-solute loaded matrices. PMID:24268271

  16. Preparation and characterization of antimicrobial wound dressings based on silver, gellan, PVA and borax.

    PubMed

    Cencetti, C; Bellini, D; Pavesio, A; Senigaglia, D; Passariello, C; Virga, A; Matricardi, P

    2012-10-15

    Silver-loaded dressings are designed to provide the same antimicrobial activity of topical silver, with the advantages of a sustained silver release and a reduced number of dressing changes. Moreover, such type of dressing must provide a moist environment, avoiding fiber shedding, dehydration and adherence to the wound site. Here we describe the preparation of a novel silver-loaded dressing based on a Gellan/Hyaff(®) (Ge-H) non woven, treated with a polyvinyl alcohol (PVA)/borax system capable to enhance the entrapment of silver in the dressing and to modulate its release. The new hydrophilic non woven dressings show enhanced water uptake capability and slow dehydration rates. A sustained silver release is also achieved. The antibacterial activity was confirmed on Staphylococcus aureus and Pseudomonas aeruginosa. PMID:22939352

  17. Fabrication of a New Type of Double-Shell Target Having a PVA Inner Layer

    SciTech Connect

    Steinman, D.A.; Wallace, R.; Grant, S.; Hoppe, M.C.; Smith, J.N. Jr.

    2004-03-15

    The General Atomics Target Fabrication team was tasked in FY03, under its ICF Target Support contract, to make a new type of double-shell target. Its specifications called for the outer shell to have an inner lining of PVA (poly(vinyl alcohol)) that would keep the xenon gas fill from occupying the target wall. The inner shell consisted of a glass shell coated with 2000 Angst of silver and filled with 9 atm of deuterium. Furthermore, the delivery deadline was less than seven weeks away. This paper describes the fielding of this double-shell target, made possible through the combined efforts of Lawrence Livermore National Laboratory and General Atomics target fabrication specialists.

  18. Immobilization of a Plant Lipase from Pachira aquatica in Alginate and Alginate/PVA Beads

    PubMed Central

    Bonine, Bárbara M.; Polizelli, Patricia Peres; Bonilla-Rodriguez, Gustavo O.

    2014-01-01

    This study reports the immobilization of a new lipase isolated from oleaginous seeds of Pachira aquatica, using beads of calcium alginate (Alg) and poly(vinyl alcohol) (PVA). We evaluated the morphology, number of cycles of reuse, optimum temperature, and temperature stability of both immobilization methods compared to the free enzyme. The immobilized enzymes were more stable than the free enzyme, keeping 60% of the original activity after 4 h at 50°C. The immobilized lipase was reused several times, with activity decreasing to approximately 50% after 5 cycles. Both the free and immobilized enzymes were found to be optimally active between 30 and 40°C. PMID:24818012

  19. FABRICATION OF A NEW TYPE OF DOUBLE SHELL TARGET HAVING A PVA INNER LAYER

    SciTech Connect

    STEINMAN,D.A; WALLACE,R; GRANT,S.E; HOPPE,M.L; SMITH,JR.J.N

    2003-06-01

    OAK-B135 The General Atomics Target Fabrication team was tasked in FY03, under its ICF Target Support contract, to make a new type of double-shell target. its specifications called for the outer shell to have an inner lining of PVA (poly(vinyl alcohol)) that would keep the xenon gas fill from occupying the target wall. The inner shell consisted of a glass shell coated with 2000 {angstrom} of silver and filled with 9 atm of deuterium. Furthermore, the delivery deadline was less than seven weeks away. This paper describes the fielding of this double-shell target, made possible through the combined efforts of Lawrence Livermore National Laboratory and General Atomics target fabrication specialists.

  20. Preparation and in vivo investigation of artificial cornea made of nano-hydroxyapatite/poly (vinyl alcohol) hydrogel composite.

    PubMed

    Fenglan, Xu; Yubao, Li; Xiaoming, Yao; Hongbing, Liao; Li, Zhang

    2007-04-01

    An artificial cornea consisted of a porous nano-hydroxyapatite/poly (vinyl alcohol) hydrogel (n-HA/PVA-H) skirt and a transparent center poly (vinyl alcohol) hydrogel (PVA-H) were prepared. The n-HA/PVA-H skirt was homogeneously porous and these pores were interconnected. Inter-penetrating network was observed along the interface between the core and the skirt. Artificial corneas were implanted in eyes of rabbit. The corneal tissues were evaluated histological. The results displayed that a good biocompatibility and interlocking had happened between artificial cornea and host tissues. This novel cornea prepared here is potential to be used clinically. PMID:17546425

  1. The adsorption of methyl methacrylate and vinyl acetate polymers on α-quartz surface: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Yan, Lijing; Yang, Yan; Jiang, Hui; Zhang, Bingjian; Zhang, Hui

    2016-01-01

    The molecular dynamics simulation was used to investigate the adsorption of polymethyl methacrylate (PMMA) and polyvinyl acetate (PVA), the commonly used surface coating materials, on α-quartz surface. The objective is to understand the interactions between quartz surface and polymers. The results clearly show adsorption of both polymers onto the quartz surface. Carbonyl group plays a significant role in the adsorption process. The adsorption energies of PMMA and PVA on α-quartz surface did not show significant difference, however, more hydrogen bonds were observed on the PVA/quartz system than PMMA/quartz. These observations might offer some insights on the polymer-quartz adhesion and its failure mechanism.

  2. Biodegradable poly(ethylene-g-vinyl alcohol) copolymer

    SciTech Connect

    Watanabe, T.; Huang, S.J.

    1993-12-31

    A graft reaction of poly(vinyl alcohol), PVA, and polyethylene grafted width maleic anhydride has been carried out in order to add hydrophobicity to PVA. Biodegradabilities of PVA and the polyethylene derivative are well-known. The graft reaction product that was prepared by a simple procedure was characterized with FTIR, DSC, and TGA. The FTIR spectra indicated that ester bonds were formed in the product. It was also found from the thermal analysis that the graft compound was less crystalline that raw PVA and the thermal properties of the graft copolymer remarkably depended on molar ratio of succinic anhydride group in the polyethylene derivative that was used in the graft reaction. The degradation of the material will be discussed.

  3. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1982-01-01

    Cross-linking methods were investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. The pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide - zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  4. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1983-01-01

    Cross-linking methods have been investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. Then pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide-zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  5. Linear and nonlinear optical properties of nanostructured Zn(1-x)SrxO-PVA composite thin films

    NASA Astrophysics Data System (ADS)

    Tamgadge, Y. S.; Sunatkari, A. L.; Talwatkar, S. S.; Pahurkar, V. G.; Muley, G. G.

    2014-11-01

    We investigate the effect of strontium doping on the linear and third order nonlinear optical properties of ZnO-polyvinyl alcohol (PVA) nano-composite thin films. Strontium doped ZnO nanoparticles capped with L-arginine were synthesized by low cost soft chemical route. These nanoparticles were characterized by X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy for its crystal structure and surface morphology studies. Linear optical responses of these samples were studied by using ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Presence of excitonic peaks for doped and undoped ZnO was revealed by UV-vis data and shift of excitonic peaks towards lower energy with increase in dopant concentration was observed. Rotational and vibrational signatures of capping agent and ZnO were confirmed by FT-IR spectroscopy. Third order nonlinearity (nonlinear refraction and absorption) of Zn(1-x)SrxO-PVA thin films, deposited on the good optical quality glass substrate, were studied by z-scan technique using He-Ne laser (wavelength 632.8 nm) in continuous wavelength regime which shows negative nonlinearity with self-defocusing effect. The large value of n2 (10-4 cm2/W) is obtained for 5 wt% strontium doped ZnO-PVA thin film and is attributed to the thermal effect. Enhanced nonlinear absorption due to reverse saturable absorption and weak free carrier absorption is observed for all undoped and doped ZnO-PVA thin films and is prominent for 5 wt% doping of strontium. Third order nonlinear susceptibility χeff(3) is calculated for all samples.

  6. Alcohol- and water-soluble bis(tpy)quaterthiophenes with phosphonium side groups: new conjugated units for metallo-supramolecular polymers.

    PubMed

    Štenclová, P; Šichová, K; Šloufová, I; Zedník, J; Vohlídal, J; Svoboda, J

    2016-01-21

    Bis(tpy)quaterthiophenes with symmetrically distributed two and four 6-bromohexyl side groups were prepared and modified by the reaction with triethylphosphine to give the corresponding ionic species. Both ionic and non-ionic bis(tpy)quaterthiophenes (unimers) were assembled with Zn(2+) and Fe(2+) ions to conjugated metallo-supramolecular polymers (MSPs), of which the ionic ones are soluble in alcohols and those derived from tetrasubstituted unimers are soluble even in water. The differences in assembly are specified between systems with (i) ionic and non-ionic unimers, (ii) Zn(2+) and Fe(2+) ion couplers, and (iii) methanol and water solvents. A substantial decrease in the stability of Fe-MSPs and a surprisingly high red shift of the luminescence band of Zn-MSPs were observed on going from methanol to aqueous solutions. PMID:26667325

  7. Effect of Chemical Structure on Polymer-Templated Growth of Graphitic Nanoribbons.

    PubMed

    Liu, Nan; Kim, Kwanpyo; Jeong, Hu Young; Hsu, Po-Chun; Cui, Yi; Bao, Zhenan

    2015-09-22

    Graphene nanoribbon (GNR) is an important candidate for future nanoelectronics due to its high carrier mobility and dimension-controlled band gap. Polymer-templated growth is a promising method toward high quality and massive production of GNRs. However, the obtained GNRs so far are still quite defective. In order to rationally control the crystallinity of the synthesized GNRs, herein we systematically investigate the effect of polymer chemical structure on their templated growth of GNRs. We studied the morphology/dimensions, composition, graphitization degree, and electrical conductivity of GNRs derived from four different types of electrospun polymers. The four polymers polystyrene (PS), poly(vinyl alcohol) (PVA), polyvinylphenol (PVP), and Novolac (a phenolic resin) are chosen to investigate the effect of metal binding and the effect of aromatic moieties. We found that metal-binding functional groups are crucial for obtaining uniform and continuous GNRs. On the other hand, a polymer with aromatic moieties leads to a higher sp(2) percentage in the resulting GNRs, showing a higher graphitization degree and electrical conductivity. PMID:26267798

  8. Photon assisted conducting polymer polymerization process for storage information and microelectronic device development

    NASA Astrophysics Data System (ADS)

    de Azevedo, W. M.; de Barros, R. A.; da Silva, E. F., Jr.

    2006-02-01

    In this work, we use the photon polymerization process to prepare conducting polymer patterns and optical memory devices (CPROM). For the CPROM and image development, polyvinyl alcohol (PVA) is used as a solid support doped with the aniline monomer and transition metals, whereas for the patterns development, the ink, of a conventional DeskJet printer is substituted by a solution of transition metal ions that is used to print the desired pattern on substrates previously treated, in an aqueous solution of conducting polymer monomer. Both processes use photons and transition metals instead of conventional oxidants to promote polymerization of the aniline monomer inside the host medium, or on a flat surface, such as glossy paper. The SEM analysis of the CPROM shows that the metal particles grow in form of wire with diameter of 100 nm and lengths up to 4μm long. The conductivity of the printed conducting polymer patterns on glossy paper is about 2 × 10 -2 S/cm. These results strongly suggest that this new, fast and low cost technology can be used to produce conducting polymer structures for all polymer electronic devices applications.

  9. Comparison of porous poly (vinyl alcohol)/hydroxyapatite composite cryogels and cryogels immobilized on poly (vinyl alcohol) and polyurethane foams for removal of cadmium.

    PubMed

    Wang, Xiao; Min, Byung Gil

    2008-08-15

    Three novel adsorbents of hydroxyapatite/poly (vinyl alcohol) (HAp/PVA) cryogel, HAp/PVA cryogel immobilized on PVA foam and HAp/PVA cryogel immobilized on polyurethane (PU) foam have been investigated to compare the morphology and sorption performances for removal of cadmium. The adsorption kinetics was interpreted by double-exponential model, pseudo-first-order model and pseudo-second-order models. The equilibrium time was found to be 36, 24, and 12 h for cryogel, cryogel immobilized on PVA foam and PU foam, respectively. The adsorption was found to follow Langmuir isotherm model and the maximum sorption capacity was estimated to be 53.3, 53.1 and 47.7 mg g(-1) for cryogel, cryogel immobilized on PVA foam and PU foam. The effects of HAp/PVA ratio and drying method on cadmium sorption were also studied. The difference of adsorption kinetics model and equilibrium time among the three adsorbents was suggested to be ascribed to different pore size. Oven-dried HAp/PVA cryogel immobilized on PU foam was preferable due to short equilibrium time and good sorption ability. PMID:18262348

  10. 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.

  11. Study of polyvinyl alcohol nanofibrous membrane by electrospinning as a magnetic nanoparticle delivery approach

    SciTech Connect

    Ger, Tzong-Rong; Huang, Hao-Ting; Hu, Keng-Shiang; Huang, Chen-Yu; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

    2014-05-07

    Electrospinning technique was used to fabricate polyvinyl alcohol (PVA)-based magnetic biodegradable nanofibers. PVA solution was mixed with ferrofluid or magnetic nanoparticles (MNPs) powder and formed two individual nanofibrous membranes (PVA/ferrofluid and PVA/MNPs powder) by electrospinning. The surface morphology of the nanofibrous membrane was characterized by scanning electron microscopy and the magnetic properties were measured by vibrating sample magnetometer. Macrophages (RAW 264.7) were co-cultured with the nanofibrous membranes for 12, 24, and 48 h and exhibited good cell viability (>95%). Results showed that the PVA fibers would be degraded and the embedded Fe{sub 3}O{sub 4} nanoparticles would be released and delivered to cells.

  12. Fabrication of porous polymer microparticles with tunable pore size and density through the combination of phase separation and emulsion-solvent evaporation approach

    NASA Astrophysics Data System (ADS)

    Liu, Shanqin; Cai, Mingle; Deng, Renhua; Wang, Jianying; Liang, Ruijing; Zhu, Jintao

    2014-02-01

    A facile and versatile route to prepare porous polymer microparticles with tunable pore size and density through the combination of phase separation and emulsion-solvent evaporation method is demonstrated. When volatile organic solvent ( e.g., chloroform) diffuses through the aqueous phase containing poly(vinyl alcohol) (PVA) and evaporates, n-hexadecane (HD) and polystyrene (PS) in oil-in-water emulsion droplets occur to phase separate due to the incompatibility between PS and HD, ultimately yielding microparticles with porous structures. Interestingly, density of the pores (pore number) on the shell of microparticles can be tailored from one to hundreds by simply varying the HD concentration and/ or the rate of solvent evaporation. Moreover, this versatile approach for preparing porous microparticles with tunable pore size and density can be applied to other types of hydrophobic polymers, organic solvents, and alkanes, which will find potential applications in the fields of pharmaceutical, catalyst carrier, separation, and diagnostics.

  13. The relationship between the adhesion work, the wettability and composition of the surface layer in the systems polymer/aqueous solution of anionic surfactants and alcohol mixtures

    NASA Astrophysics Data System (ADS)

    Zdziennicka, Anna; Jańczuk, Bronisław

    2010-11-01

    Measurements of advancing contact angle ( θ) were carried out on polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) for aqueous solution of sodium dodecyl sulfate (SDDS) mixtures with methanol, ethanol and propanol in the range of SDDS concentration from 10 -5 to 10 -2 M, and for sodium hexadecyl sulfonate (SHS) with the same alcohols at the SHS concentration ranging from 10 -5 to 8 × 10 -4 M at 293 K. The concentration of methanol, ethanol and propanol used for measurements varied from 0 to 21.1, 11.97 and 6.67 M, respectively. On the basis of the contact angles the critical surface tension of PTFE and PMMA wetting was determined by using for this purpose the relationship between the adhesion and the surface tension and cos θ and surface tension both at constant alcohol and surfactant concentration, respectively. The obtained contact angles were also used in the Young Dupre' equation for calculations of the adhesion work of aqueous solution of mixtures of anionic surfactants and short chain alcohols to PTFE and PMMA surface. The adhesion work calculated in this way was compared to that of the particular components of aqueous solution to these surfaces determined on the basis of the surface tension components and parameters of the surface tension of the surface active agents, water, PTFE and PMMA from van Oss et al. equation. The calculated adhesion work was discussed in the light of the concentration of surface active agents at polymer-water and water-air interface determined from Lucassen-Reynders, Gibbs and Guggenheim-Adam equations.

  14. Light-induced switching of the wettability of novel asymmetrical poly(vinyl alcohol)-co-ethylene membranes blended with azobenzene polymers.

    PubMed

    Tylkowski, Bartosz; Peris, Sergio; Giamberini, Marta; Garcia-Valls, Ricard; Reina, José A; Ronda, Joan C

    2010-09-21

    Novel composite asymmetrical membranes based on poly(vinyl alcohol)-co-ethylene (EVAL) as the host material and new polyethers that contain azobenzene moieties in the side chain were prepared by dry-cast phase inversion after dissolving the azo polymers in tetrahydrofuran and EVAL in dimethylsulfoxide and subsequently mixing the resulting solutions. By taking advantage of the proper temperature variation in the oven used for solvent evaporation, asymmetrical membranes that exhibited a dense, crystalline layer on the bottom and a porous, mainly amorphous layer on the top were obtained. Remarkable changes in the surface morphology and the contact angle with water were observed on the top surfaces of the composite membranes. This was ascribed not only to the enhanced concentration of azo polymer on the top surface but mostly to a conformational change in EVAL induced by the photoisomerization of the guest azo groups, as shown by HRMAS (1)H NMR. The morphological and structural changes in EVAL could be reversed on exposing the membrane to visible light for 24 h. PMID:20799708

  15. Nonlinear optical studies of liquid crystals and polymers

    NASA Astrophysics Data System (ADS)

    Hong, Seok-Cheol

    Polymers are indispensable in our life. A life is a continuous event maintained by many complex processes in which biological polymers participate. It also gets help from a variety of natural and synthetic polymers with useful functions. Such functions depend on the chemical and conformational structures of polymers and often largely on the surface structures and properties of polymers. We used second order nonlinear optical techniques (sum frequency vibrational spectroscopy (SFVS) and second harmonic generation (SHG)) to obtain structural information on polymers. We also studied liquid crystal molecules deposited on polymer surfaces. The first part of the thesis is aimed at understanding liquid crystal (LC) alignment on rubbed polymer surfaces by determining the molecular orientations of LC adsorbates and surface polymer chains. The alignment of LCs by rubbed polymers is not only of fundamental interest but also of practical importance because it is a technique enabling production of commercial liquid crystal displays. We observed that rubbing induces alignment of surface polymer chains along the rubbing direction, and there is a strong correlation between the molecular orientations of LC adsorbates and the surface chains of rubbed polymers such as polyvinyl alcohol (PVA) and polyimide (6FDA-6CBO). The latter revealed a relatively large but negative pretilt angle, which is highly unusual. On a rubbed polystyrene (PS) surface, we found that the phenyl side groups of PS are oriented perpendicularly to the rubbing direction at the surface, rendering an LC alignment also perpendicular to the rubbing direction. The second part of the thesis is our discovery of rubbing-induced polar ordering on nylon 11 surfaces. Nylon 11 is known to be ferroelectric. We found that mechanical rubbing can induce strong ferroelectric polarization on an initially amorphous film of nylon 11. The surface chains of rubbed nylon 11 are aligned along the rubbing direction while the induced

  16. Study of dielectric and piezoelectric properties of CNT reinforced PZT-PVA 0-3 composite

    NASA Astrophysics Data System (ADS)

    Vyas, Prince; Prajapat, Rampratap; Manmeeta, Saxena, Dhiraj

    2016-05-01

    Ferroelectric ceramic/polymer composites have the compliance of polymers which overcome the problems of brittleness in ceramics. By imbedding piezoelectric ceramic powder into a polymer matrix, 0-3 composites with good mechanical properties and high dielectric breakdown strength can be developed. The obtained composites of 0-3 connectivity exhibit the piezoelectric properties of ceramics and flexibility, strength and lightness of polymer. These composites can be used in vibration sensing and transducer applications specially as piezoelectric sensors. A potential way to improve piezoelectric& dielectric properties of theses composites is by inclusion of another conductive phase in these composites as reported in the literature. In present work, we prepared PZT-PVA 0-3 composites with 60% ceramic volume fraction reinforced with CNTs with volume ranging from 0 to 1.5 vol%. These CNT reinforced composites were obtained using hot press method with thickness of 200 µm having 0-3 conductivity. These composites were poled applying DC voltage. Dielectric properties of these samples were obtained in a wide frequency range (100 Hz to 1 Mhz) at room temperature. The piezoelectric properties of these composites were analyzed by measuring piezoelectric charge constants (d33). The dielectric and piezoelectric properties of these composites were studied as a function of CNT volume content. In these reinforced composites, CNTs act as a conductive filler dispersed in the matrix which in turn facilitates poling and results in an increase of the piezoelectric properties of the composite due to formation of percolation path through the composites. With a CNT content of 0.3 vol.% in PZT/PVA/CNTs, an increase of 61.3 % was observed in piezoelectric strain factors (d33). In these CNT reinforced composites, a substantial increase (approx. 67%) was also observed in dielectric constant and approximately 89% increase was observed in dielectric loss factor. Results so obtained are in the good

  17. Titanium carbide nanocube core induced interfacial growth of crystalline polypyrrole/polyvinyl alcohol lamellar shell for wide-temperature range supercapacitors

    NASA Astrophysics Data System (ADS)

    Weng, Yu-Ting; Pan, Hsiao-An; Wu, Nae-Lih; Chen, Geroge Zheng

    2015-01-01

    This is the first investigation on electrically conducting polymers-based supercapacitor electrodes over a wide temperature range, from -18 °C to 60 °C. A high-performance supercapacitor electrode material consisting of TiC nanocube core and conformal crystalline polypyrrole (PPy)/poly-vinyl-alcohol (PVA) lamellar shell has been synthesized by heterogeneous nucleation-induced interfacial crystallization. PPy is induced to crystallize on the negatively charged TiC nanocube surfaces via strong interfacial interactions. In this organic-inorganic hybrid nanocomposite, the long chain PVA enables enhanced cycle life due to improved mechanical properties, and the TiC nanocube not only contributes to electron conduction, but also dictates the PPy morphology/crystallinity for maximizing the charging-discharging performance. The crystalline PPy/PAV layer on the TiC nanocube offers unprecedented high capacity (>350 F g-1-PPy at 300 mV s-1 with ΔV = 1.6 V) and cycling stability in a temperature range from -18 °C to 60 °C. The presented hybrid-filler and interfacial crystallization strategies can be applied to the exploration of new-generation high-power conducting polymer-based supercapacitor materials.

  18. Non-cytotoxic silver nanoparticle-polyvinyl alcohol hydrogels with anti-biofilm activity: designed as coatings for endotracheal tube materials.

    PubMed

    Loo, Ching-Yee; Young, Paul M; Lee, Wing-Hin; Cavaliere, Rosalia; Whitchurch, Cynthia B; Rohanizadeh, Ramin

    2014-01-01

    Endotracheal intubation is commonly associated with hospital-acquired infections as the intubation device acts as reservoir for bacterial colonization in the lungs. To reduce the incidence of bacterial colonization on the tubes, hydrogel coatings loaded with antimicrobial agents are gaining popularity. The aim of this study was to incorporate silver nanoparticles (AgNPs) into polyvinyl alcohol (PVA) to form stable hydrogels. Embedding AgNPs into PVA resulted in a decreased elongation at break and an increased tensile strength compared to PVA alone. The Ag release profile varied as a function of the degree of hydrolysis of PVA: the higher degree of hydrolysis demonstrated a lower release rate. Fourier infrared transform spectroscopy demonstrated that AgNPs interacted exclusively with the -OH groups of PVA. AgNP-loaded PVA was non-toxic against human normal bronchial epithelial cells while effective against the attachment of Pseudomonas aeruginosa and Staphylococcus aureus with a greater effect on P. aeruginosa. PMID:24963686

  19. 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

  20. Nanoscale Mechanical Characterization of Graphene/Polymer Nanocomposites using Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Cai, Minzhen

    Graphene materials, exhibiting outstanding mechanical properties, are excellent candidates as reinforcement in high-performance polymer nanocomposites. In this dissertation, advanced atomic force microscopy (AFM) techniques are applied to study the nanomechanics of graphene/polymer nanocomposites, specifically the graphene/polymer interfacial strength and the stress transfer at the interface. Two novel methods to directly characterize the interfacial strength between individual graphene sheets and polymers using AFM are presented and applied to a series of polymers and graphene sheets. The interfacial strength of graphene/polymer varies greatly for different combinations. The strongest interaction is found between graphene oxide (GO) and polyvinyl alcohol (PVA), a strongly polar, water-based polymer. On the other hand, polystyrene, a non polar polymer, has the weakest interaction with GO. The interfacial bond strength is attributed to hydrogen bonding and physical adsorption. Further, the stress transfer in GO/PVA nanocomposites is studied quantitatively by monitoring the strain in individual GO sheet inside the polymer via AFM and Raman spectroscopy. For the first time, the strains of individual GO sheets in nanocomposites are imaged and quantified as a function of the applied external strains. The matrix strain is directly transferred to GO sheets for strains up to 8%. At higher strain levels, the onset of the nanocomposite failure and a stick-slip behavior is observed. This study reveals that GO is superior to pure graphene as reinforcement in nanocomposites. These results also imply the potential to make a new generation of nanocomposites with exceptional high strength and toughness. In the second part of this dissertation, AFM is used to study the structure of silk proteins and the morphology of spider silks. For the first time, shear-induced self-assembly of native silk fibroin is observed. The morphology of the Brown Recluse spider silk is investigated and a

  1. Remediation of environmental pollution by substituting poly(vinyl alcohol) with biodegradable warp size from wheat gluten.

    PubMed

    Chen, Lihong; Reddy, Narendra; Yang, Yiqi

    2013-05-01

    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. PMID:23551198

  2. Controlling the phase structures of polymer/surfactant complexes by changing macromolecular architecture and adding n-alcohols.

    PubMed

    Percebom, Ana Maria; Loh, Watson

    2016-03-15

    Phase behavior of complex salts formed by a cationic surfactant and different ethoxylated polyions was investigated in water and with addition of two n-alcohols of different chain lengths: n-butanol and n-decanol. The polyion possesses a main chain of methacrylic acid randomly grafted with oligo(ethylene oxide) chains. Strong electrostatic interaction between the anionic main chain and the cationic surfactant hexadecyltrimethylammonium (C16TA) leads to the formation of C16TAP(MA-MAEO(n)) x:y complex salts. Modifications in polyion structure, such as changes in the proportion of grafted comonomers and in the side chain length caused differences in the overall balance of interactions with water and n-alcohols, altering the complex salt solubility and, consequently, the formed liquid-crystalline structures. The role of n-decanol as a cosurfactant was verified, but the hydrophilic side chains expanded the capacity of the formed liquid crystalline phases to incorporate water. Additionally, a novel structure, probably cubic bicontinuous (Pn3m), was observed coexisting with lamellar phases at low water concentration. Because n-butanol is known for being a good solvent for poly(ethylene oxide), these side chains intensified the role of this short chain n-alcohol as cosolvent for C16TAP(MA-MAEO(n)) x:y complex salts, favoring the formation of disordered solutions, including a bicontinuous microemulsion. PMID:26752433

  3. An experimental study for syndiotactic polyvinyl alcohol spheres as an embolic agent: can it maintain spherical shape in vivo?

    PubMed

    Chun, Ho Jong; Lee, Hae Giu; Lyoo, Won Seok; Lee, Ji Youl; Kim, Jina

    2014-01-01

    Syndiotactic polyvinyl alcohol (PVA) had been developed to overcome the drawbacks of atactic PVA spheres that deform easily, which can lead to non-target embolization. This study was performed to evaluate the in vivo stability of spherical shape of the syndiotactic PVA spheres. Selective arteriography and transarterial embolization (TAE) were performed in the main renal arteries of eight New Zealand white rabbits using syndiotactic PVA sphere that consisted of syndiotactic PVA skin and a copolymer core of vinyl acetate/vinyl pivalate. The size of the syndiotactic PVA spheres used for the TAE was 212-355 μm. The rabbits were sacrificed 12-14 days after TAE. Gross and microscopic examinations of each kidney were performed. The microscopic examination showed infarction of all embolized kidneys. Syndiotactic PVA spheres were seen uniformly within the arterial lumen and appeared as round ring-like structures without any deformity. The syndiotactic PVA spheres exclusively occupied the arterial lumen. As a conclusion, syndiotactic PVA spheres maintained their spherical shape without significant deformation in this in vivo short-term experimental study. Further investigation is necessary for evaluation of detailed effects of physical stability in tumor embolization. PMID:24948458

  4. Coding coarse grained polymer model for LAMMPS and its application to polymer crystallization

    NASA Astrophysics Data System (ADS)

    Luo, Chuanfu; Sommer, Jens-Uwe

    2009-08-01

    We present a patch code for LAMMPS to implement a coarse grained (CG) model of poly(vinyl alcohol) (PVA). LAMMPS is a powerful molecular dynamics (MD) simulator developed at Sandia National Laboratories. Our patch code implements tabulated angular potential and Lennard-Jones-9-6 (LJ96) style interaction for PVA. Benefited from the excellent parallel efficiency of LAMMPS, our patch code is suitable for large-scale simulations. This CG-PVA code is used to study polymer crystallization, which is a long-standing unsolved problem in polymer physics. By using parallel computing, cooling and heating processes for long chains are simulated. The results show that chain-folded structures resembling the lamellae of polymer crystals are formed during the cooling process. The evolution of the static structure factor during the crystallization transition indicates that long-range density order appears before local crystalline packing. This is consistent with some experimental observations by small/wide angle X-ray scattering (SAXS/WAXS). During the heating process, it is found that the crystalline regions are still growing until they are fully melted, which can be confirmed by the evolution both of the static structure factor and average stem length formed by the chains. This two-stage behavior indicates that melting of polymer crystals is far from thermodynamic equilibrium. Our results concur with various experiments. It is the first time that such growth/reorganization behavior is clearly observed by MD simulations. Our code can be easily used to model other type of polymers by providing a file containing the tabulated angle potential data and a set of appropriate parameters. Program summaryProgram title: lammps-cgpva Catalogue identifier: AEDE_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDE_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU's GPL No. of lines in distributed program

  5. 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.

  6. Poly(vinyl alcohol) Modified Porous Graphitic Carbon Stationary Phase for Hydrophilic Interaction Liquid Chromatography.

    PubMed

    Hou, Yanjie; Zhang, Feifang; Liang, Xinmiao; Yang, Bingcheng; Liu, Xiaodong; Dasgupta, Purnendu K

    2016-05-01

    We report a poly(vinyl alcohol) (PVA)-coated porous graphitic carbon (PGC, Hypercarb) packing as a novel stationary phase for hydrophilic interaction liquid chromatography (HILIC). The exterior and the pores of the PGC particles are coated with a thin layer of PVA by soaking the particles in a PVA solution, filtering, and thermally cross-linking the PVA. Such PVA coated PGC particles (5.7 μm diameter), hereinafter called PVA-PGC are stable at least through pH 1.0-12.7, can be made in <2 h, and exhibit different selectivity relative to six commercial HILIC phases and bare PGC. To our knowledge, this is the first fully pH-stable, completely neutral HILIC phase. Excellent efficiency stable is observed for polar analytes (∼70 000 and 118 000 plates/m for cytosine and resorcinol, respectively). Retention closely resembles standard HILIC behavior. Other substances can also be easily incorporated in the PVA layer; an anion exchange column can be readily made by incorporating diallyldimethylammonium chloride in the PVA coating solution. The ease of preparation without the requirement of synthetic skills or paraphernalia and the possibility of incorporating a variety of modifiers makes this a particularly versatile approach. PMID:27053418

  7. Vitamin C hinders radiation cross-linking in aqueous poly(vinyl alcohol) solutions

    NASA Astrophysics Data System (ADS)

    Oral, Ebru; Bodugoz-Senturk, Hatice; Macias, Celia; Muratoglu, Orhun K.

    2007-12-01

    Poly(vinyl alcohol) (PVA) is a promising semi-crystalline material for biomedical applications. It is soluble in water and can be formed into hydrogels by freezing and thawing or crystallizing from an aqueous theta solution such as that of polyethylene glycol (PEG). Radiation cross-linking caused by sterilization or high dose irradiation of concentrated PVA solutions could compromise some properties of these hydrogels. Therefore, we hypothesized that radiation cross-linking of PVA solutions and PVA-PEG theta gels could be prevented by using the antioxidant vitamin C as an anticross-linking agent. Our hypothesis tested positive. Vitamin C concentrations of 0.75 and 4.5 mol/mol of PVA repeating unit could prevent cross-linking in 17.5 wt/v% PVA solutions made with PVA molecular weight of 115,000 g/mol irradiated to 25 and 100 kGy, respectively. Vitamin C also prevented cross-linking in 25 kGy irradiated PVA-PEG theta gels containing up to 5 wt% PEG and decreased the viscosity of those up to 39 wt%.

  8. Plasma functionalization of poly(vinyl alcohol) hydrogel for cell adhesion enhancement

    PubMed Central

    Ino, Julia M.; Chevallier, Pascale; Letourneur, Didier; Mantovani, Diego; Le Visage, Catherine

    2013-01-01

    Tailoring the interface interactions between a biomaterial and the surrounding tissue is a capital aspect to consider for the design of medical devices. Poly(vinyl alcohol) (PVA) hydrogels present suitable mechanical properties for various biological substitutes, however the lack of cell adhesion on their surface is often a problem. The common approach is to incorporate biomolecules, either by blending or coupling. But these modifications disrupt PVA intra- and intermolecular interactions leading therefore to a loss of its original mechanical properties. In this work, surface modification by glow discharge plasma, technique known to modify only the surface without altering the bulk properties, has been investigated to promote cell attachment on PVA substrates. N2/H2 microwave plasma treatment has been performed, and the chemical composition of PVA surface has been investigated. X-ray photoelectron and Fourier transform infrared analyses on the plasma-treated films revealed the presence of carbonyl and nitrogen species, including amine and amide groups, while the main structure of PVA was unchanged. Plasma modification induced an increase in the PVA surface wettability with no significant change in surface roughness. In contrast to untreated PVA, plasma-modified films allowed successful culture of mouse fibroblasts and human endothelial cells. These results evidenced that the grafting was stable after rehydration and that it displayed cell adhesive properties. Thus plasma amination of PVA is a promising approach to improve cell behavior on contact with synthetic hydrogels for tissue engineering. PMID:23989063

  9. 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. PMID:26369028

  10. Wound healing modulation by a latex protein-containing polyvinyl alcohol biomembrane.

    PubMed

    Ramos, Márcio V; de Alencar, Nylane Maria N; de Oliveira, Raquel S B; Freitas, Lyara B N; Aragão, Karoline S; de Andrade, Thiago Antônio M; Frade, Marco Andrey C; Brito, Gerly Anne C; de Figueiredo, Ingrid Samantha T

    2016-07-01

    In a previous study, we performed the chemical characterization of a polyvinyl alcohol (PVA) membrane supplemented with latex proteins (LP) displaying wound healing activity, and its efficacy as a delivery system was demonstrated. Here, we report on aspects of the mechanism underlying the performance of the PVA-latex protein biomembrane on wound healing. LP-PVA, but not PVA, induced more intense leukocyte (neutrophil) migration and mast cell degranulation during the inflammatory phase of the cicatricial process. Likewise, LP-PVA induced an increase in key markers and mediators of the inflammatory response (myeloperoxidase activity, nitric oxide, TNF, and IL-1β). These results demonstrated that LP-PVA significantly accelerates the early phase of the inflammatory process by upregulating cytokine release. This remarkable effect improves the subsequent phases of the healing process. The polyvinyl alcohol membrane was fully absorbed as an inert support while LP was shown to be active. It is therefore concluded that the LP-PVA is a suitable bioresource for biomedical engineering. PMID:27037828

  11. Molecular vibrational dynamics in polyvinyl alcohol studied by femtosecond coherent anti-stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Kozai, T.; Yamashita, S.; Hirochi, K.; Miyagawa, H.; Tsurumachi, N.; Koshiba, S.; Nakanishi, S.; Itoh, H.

    2012-11-01

    We have performed femtosecond time-resolved coherent anti-stokes Raman spectroscopy (CARS) to study the vibrational dynamics in polyvinyl alcohol (PVA) film. We observed femtosecond coherent vibrational relaxation and CARS signal beats in PVA at room temperature. We found that the coherent vibrational relaxation of anti-symmetric CH2 stretching modes in PVA is faster than that of symmetric modes, probably due to faster vibrational energy transfer. The coherent vibrational relaxation of OH stretching modes was observed to be slower than that of CH2 modes, because OH stretching modes have less resonant energy transfer rate compared to CH2 modes.

  12. Scalable production of controllable dermal papilla spheroids on PVA surfaces and the effects of spheroid size on hair follicle regeneration.

    PubMed

    Huang, Yi-Ching; Chan, Chih-Chieh; Lin, Wei-Ting; Chiu, Hsien-Yi; Tsai, Ren-Yeu; Tsai, Tsung-Hua; Chan, Jung-Yi; Lin, Sung-Jan

    2013-01-01

    Organ size and numbers are vital issues in bioengineering for hair follicle (HF) regeneration. Murine HF dermal papilla (DP) cells are able to induce HF neogenesis when transplanted as aggregates. However, how the preparation of murine and human DP aggregates affects HF inductivity and the size of regenerated HF is yet to be determined. Here we report a scalable method for production of controllable human and rat DP spheroids in general labs for reproducible experiments. Compared with more hydrophobic polyethylene and poly(ethylene-co-vinyl alcohol), DP cells are poorly adhesive to hydrophilic polyvinyl alcohol (PVA). Seeded in PVA-coated 96-welled commercial PCR tube arrays, DP cells quickly aggregate into single spheroids with progressive compaction. Varying seeded cell numbers and culture periods enables us to control the size and cell number of the spheroids. The spheroids obtained have high viability and preserve DP characters. A proof of principle experiment was conducted to examine the size effect on the efficiency and efficacy of HF regeneration. We found that both human and rat DP spheroids are able to induce HF neogenesis and larger DP spheroids exhibit higher HF inductivity. However, the average diameter of regenerated hair fiber did not significantly change with the increasing size of transplanted DP spheroids. The result suggests that an appropriate size of DP spheroid is essential for HF inductivity, but its size cannot be directly translated to a thicker regenerated hair. Our results also have implications on the efficiency and efficacy in the regeneration of other epithelial organs. PMID:23092862

  13. Preparation of the poly(vinyl alcohol)/layered double hydroxide nanocomposite

    SciTech Connect

    Li Baoguang; Hu Yuan; Zhang Rui; Chen Zuyao; Fan Weicheng

    2003-10-01

    Intercalated nanocomposite based on Mg, Al layered double hydroxide (LDH) and poly(vinyl alcohol) (PVA) was prepared using exfoliation-adsorption technique, and characterized by X-ray diffraction and thermal gravimetric analysis. The results suggest that the intercalated species are formed via the re-aggregation of the delaminated LDH lamellar with the interlayer spacing 14.5 A, and the thermal stability of the nanocomposite improved compared with the original PVA.

  14. Tuning the SERS Response with Ag-Au Nanoparticle-Embedded Polymer Thin Film Substrates.

    PubMed

    Rao, V Kesava; Radhakrishnan, T P

    2015-06-17

    Development of facile routes to the fabrication of thin film substrates with tunable surface enhanced Raman scattering (SERS) efficiency and identification of the optimal conditions for maximizing the enhancement factor (EF) are significant in terms of both fundamental and application aspects of SERS. In the present work, polymer thin films with embedded bimetallic nanoparticles of Ag-Au are fabricated by a simple two-stage protocol. Ag nanoparticles are formed in the first stage, by the in situ reduction of silver nitrate by the poly(vinyl alcohol) (PVA) film through mild thermal annealing, without any additional reducing agent. In the second stage, aqueous solutions of chloroauric acid spread on the Ag-PVA thin film under ambient conditions, lead to the galvanic displacement of Ag by Au in situ inside the film, and the formation of Ag-Au particles. Evolution of the morphology of the bimetallic nanoparticles into hollow cage structures and the distribution of Au on the nanoparticles are revealed through electron microscopy and energy dispersive X-ray spectroscopy. The localized surface plasmon resonance (LSPR) extinction of the nanocomposite thin film evolves with the Ag-Au composition; theoretical simulation of the extinction spectra provides insight into the observed trends. The Ag-Au-PVA thin films are found to be efficient substrates for SERS. The EF follows the variation of the LSPR extinction vis-à-vis the excitation laser wavelength, but with an offset, and the maximum SERS effect is obtained at very low Au content; experiments with Rhodamine 6G showed EFs on the order of 10(8) and a limit of detection of 0.6 pmol. The present study describes a facile and simple fabrication of a nanocomposite thin film that can be conveniently deployed in SERS investigations, and the utility of the bimetallic system to tune and maximize the EF. PMID:26035249

  15. Synthesis and characterization of a stable dispersion of multifunctional Gd2O3:Er,Yb in polyvinyl alcohol.

    PubMed

    Kaur, Gagandeep; Rai, S B

    2013-01-01

    A stable dispersion of multifunctional Gd2O3:Er,Yb phosphor in polyvinyl alcohol (PVA) was synthesized by varying the concentration of Yb(3+) ions. It had a strong ultraviolet-visible-near infrared (UV-vis) upconversion emission and applications in temperature and magnetic field sensors (e.g., nano-heaters), as well as potential use in bioleveling and bioimaging. Stability of the dispersion was found to strongly depend on the mixing process of the powder in the polymer solution. Spherical shaped nanoparticles in cubic phase of ~ 43 nm diameter were synthesized and characterized by X-ray diffraction; results were confirmed by scanning electron microscopy (SEM). Fourier transform infrared sspectroscopy (FT-IR) and thermal analysis supported the presence of PVA. NIR pumping produced strong UC emission bands in the red and green regions extending up to very high UV (240 nm). This method provides an alternative for synthesizing a highly UC-efficient non-agglomerated pure transparent dispersion from various efficient phosphors for biological applications. PMID:22354467

  16. Ca3(PO4)2 precipitated layering of an in situ hybridized PVA/Ca2O4Si nanofibrous antibacterial wound dressing.

    PubMed

    Mabrouk, Mostafa; Choonara, Yahya E; Marimuthu, Thashree; Kumar, Pradeep; du Toit, Lisa C; van Vuuren, Sandy; Pillay, Viness

    2016-06-30

    The aim of this study was to develop an in situ hybridized poly(vinyl alcohol)/calcium silicate (PVA/Ca2OSi) nanofibrous antibacterial wound dressing with calcium phosphate [Ca3(PO4)2] surface precipitation for enhanced bioactivity. This was achieved by hybridizing the antibacterial ions Zn(2+) and/or Ag(+) in a Ca2O4Si composite. The hybridization effect on the thermal behavior, physicochemical, morphological, and physicomechanical properties of the nanofibers was studied using Differential Scanning calorimetric (DSC), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Textural Analysis, respectively. In vitro bioactivity, biodegradation and pH variations of the nanofiber composite were evaluated in Simulated Body Fluid (SBF). The antibacterial activity was assessed against Staphylococcus aureus and Pseudomonas aeruginosa. Hybridization of Zn(2+) and/or Ag(+) into the PVA/Ca2O4Si nanofiber composite was confirmed by DSC, XRD and FTIR. The thickness of the nanofibers was dependent on the presence of Zn(2+) and Ag(+) as confirmed by SEM. The nanofibers displayed enhanced tensile strength (19-115.73MPa) compared to native PVA. Zn(2+) and/or Ag(+) hybridized nanofibers showed relatively enhanced in vitro bioactivity, biodegradation (90%) and antibacterial activity compared with the native PVA/Ca2O4Si nanofiber composite. Results of this study has shown that the PVA/Ca2O4Si composite hybridized with both Zn(2+) and Ag(+) may be promising as an antibacterial wound dressing with a nanofibrous archetype with enhanced bioactivity. PMID:27154257

  17. Synthesis, characterization and optical properties of polymer-based ZnS nanocomposites.

    PubMed

    Tiwari, A; Khan, S A; Kher, R S; Dhoble, S J; Chandel, A L S

    2016-03-01

    Nanostructured polymer-semiconductor hybrid materials such as ZnS-poly(vinyl alcohol) (ZnS-PVA), ZnS-starch and ZnS-hydroxypropylmethyl cellulose (Zns-HPMC) are synthesized by a facile aqueous route. The obtained nanocomposites are characterized using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy and photoluminescence (PL). XRD studies confirm the zinc blende phase of the nanocomposites and indicate the high purity of the samples. SEM studies indicate small nanoparticles clinging to the surface of a bigger particle. The Energy Dispersive Analysis by X-rays (EDAX) spectrum reveals that the elemental composition of the nanocomposites consists primarily of Zn:S. FTIR studies indicate that the polymer matrix is closely associated with ZnS nanoparticles. The large number of hydroxyl groups in the polymer matrix facilitates the complexation of metal ions. The absorption spectra of the specimens show a blue shift in the absorption edge. The spectrum reveals an absorption edge at 320, 310 and 325 nm, respectively. PL of nanocomposites shows broad peaks in the violet-blue region (420-450 nm). The emission intensity changes with the nature of capping agent. The PL intensity of ZnS-HPMC nanocomposites is found to be highest among the studied nanocomposites. The results clearly indicate that hydroxyl-functionalized HPMC is much more effective at nucleating and stabilizing colloidal ZnS nanoparticles in aqueous suspensions compared with PVA and starch. PMID:26334003

  18. 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.

  19. 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.

  20. 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.

  1. Rainfastness of Poly(vinyl alcohol) Deposits on Vicia faba Leaf Surfaces: From Laboratory-Scale Washing to Simulated Rain.

    PubMed

    Symonds, Brett L; Thomson, Niall R; Lindsay, Christopher I; Khutoryanskiy, Vitaliy V

    2016-06-01

    Rainfastness is the ability of agrochemical deposits to resist wash-off by rain and other related environmental phenomena. This work reports laboratory-scale and raintower studies of the rainfastness of fluorescently labeled poly(vinyl alcohol) (PVA) using fluorescent microscopy combined with image analysis. Samples of hydrolyzed PVA exhibit improved rainfastness over a threshold molecular weight, which correlates with PVA film dissolution, swelling, and crystalline properties. It was also established that the rainfastness of PVA scaled with the molecular weight over this threshold. These PVA samples were further characterized in order to determine the effect of the crystallinity on rainfastness. The quantification of rainfastness is of great interest to the field of agrochemical formulation development in order to improve the efficacy of pesticides and their adjuvants. PMID:27070864

  2. 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.

  3. 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.

  4. Environmentally friendly Zn0.75Cd0.25S/PVA heterosystem nanocomposite: UV-stimulated emission and absorption spectra

    NASA Astrophysics Data System (ADS)

    Imam, N. G.; Mohamed, Mohamed Bakr

    2016-02-01

    Zn0.75Cd0.25S nanoparticles prepared at different temperatures were composited with polyvinyl alcohol for functionalization it in wide spectrum of applications such as in photocatalysis. The nanostructure of the Zn0.75Cd0.25S mother phase is confirmed by X-ray diffraction in addition to absorption and fluorescence spectra. UV/VIS. measurements show that, the transmittance coefficient of Zn0.75Cd0.25S/PVA nanocomposite is lesser than that of pure PVA by 0.33% and varies upon increasing the preparation temperature; reaching a maximum value for the sample prepared at 300 °C. It was found that the optical band gap tunes with annealing temperature which, in turns, with particle size. The refractive index of the Zn0.75Cd0.25S/PVA nanocomposite films decrease with increasing wavelength and saturates at high wavelengths. The optical conductivity increases with increasing photon energy which may be due to the excitation of electrons by photon energy. The optical conductivity of Zn0.75Cd0.25S/PVA nanocomposite is lesser than that of pure PVA and it decreases as the preparation temperature of Zn0.75Cd0.25S nanoparticles in PVA matrix increases which could be related to the decrease in the extinction coefficient and the density of localized states in the gap. Abroad peak deconvoluted, by Gaussian fitting function, into two violet and blue colors was observed in the fluorescence spectra under UV light irradiation. The two emission bands are attributed to band edge emission and neutral oxygen vacancies respectively. Analysis of fluorescence (FL) spectra reveals quenching in FL intensity and a peak shifting towards the lower wavelength side with increasing the preparation temperature of the mother phase. The results suggest that the 200 °C Zn0.75Cd0.25S/PVA nanocomposites have been regarded as a promising candidate in many technical fields, such as photocatalytic hydrogen production and/or photocatalytic degradation of organic dyes under UV irradiation due to its high optical

  5. Polyvinyl alcohol membranes as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Gonzalez-Sanabria, O.; Manzo, M. A.

    1982-01-01

    Polyvinly alcohol (PVA) cross-linked with aldehyde reagents yields membranes that demonstrate properties that make them suitable for use as alkaline battery separators. Film properties can be controlled by the choice of cross-linker, cross-link density and the method of cross-linking. Three methods of cross-linking and their effects on film properties are discussed. Film properties can also be modified by using a copolymer of vinyl alcohol and acrylic acid as the base for the separator and cross-linking it similarly to the PVA. Fillers can be incorporated into the films to further modify film properties. Results of separator screening tests and cell tests for several variations of PBA films are discussed.

  6. 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. PMID:23536274

  7. Microcrystalline Zinc Coordination Polymers as Single-site Heterogeneous Catalysts for the Selective Synthesis of Mono-oxazolines from Amino Alcohol and Dinitriles.

    PubMed

    Wang, Junning; Huang, Chao; Gao, Kuan; Wang, Xiaolu; Liu, Mengjia; Ma, Haoran; Wu, Jie; Hou, Hongwei

    2016-06-21

    In our effort to develop coordination polymers (CPs)-based single-site catalysts for the selective synthesis of mono-oxazolines, two Zn-based CPs, [{Zn6 (idbt)4 (phen)4 } ⋅3 H2 O]n  (1) and [{Zn3 (idbt)2 (H2 O)4 }⋅2 H2 O]n  (2) (H3 idbt= 5,5'-(1H-imidazole-4,5-diyl)-bis-(2H-tetrazole), phen=1,10-phenanthroline) have been synthesized. They exhibit two-dimensional structure and contain isolated and accessible catalytically active sites, mimicking the site isolation of many catalytic enzymes. Micro CPs 1 and 2 are obtained by using surfactant-mediated hydrothermal methods, and an investigation is conducted to explore how different surfactants affect their morphologies and particle sizes. Furthermore, micro 1 and 2 have shown to be effective heterogeneous catalysts for the reaction of amino alcohols and aromatic dinitriles, and exerted a significant influence on the selectivity of the catalytic reactions, yielding mono-oxazolines as the major reaction product. PMID:27136746

  8. An electrochromic film device to teach polymer electrochemical physics

    NASA Astrophysics Data System (ADS)

    Huang, Mei-Rong; Tao, Tao; Li, Xin-Gui; Gong, Qian-Cheng

    2007-09-01

    We discuss the background associated with an electrochromic device that can reversibly change its color and optical density at a specific potential. We discuss the underlying science needed to make a new polyaniline (PAN)/polyvinyl alcohol(PVA) electrochromic composite film on an indium-tin oxide (ITO) conducting glass by electropolymerization and describe a reversible redox transition of the PAN. The experiment gives students an opportunity to fabricate an electrochromic device containing PAN, one of the most important conducting polymers. The experimental conditions are flexible so that each group of students can construct their own electrochromic device with particular behavior. Two techniques for polymerizing the PAN and three methods of demonstrating the electrochromism are given, depending on the available apparatus. A sophisticated three-electrode potentiostat or a crude apparatus containing a battery, wire, a variable resistor, and a voltage meter is used to synthesize the PAN deposit. The electrochromic property is repetitively observed by reversibly changing the applied potentials on the device. A potentiostatic apparatus, a single flashlight battery, or a flashlight battery accompanied by a variable resistor allows students to observe multicolor electrochromism. The experiments significantly enhance students' understanding of polymer chemicophysics principles and their appreciation of novel variable colorful films. The experiments are safe and easy to perform, provided that appropriate precautions are taken.

  9. Preparation of a Nanoscaled Poly(vinyl alcohol)/Hydroxyapatite/DNA Complex Using High Hydrostatic Pressure Technology for In Vitro and In Vivo Gene Delivery

    PubMed Central

    Kimura, Tsuyoshi; Nibe, Yoichi; Funamoto, Seiichi; Okada, Masahiro; Furuzono, Tsutomu; Ono, Tsutomu; Yoshizawa, Hidekazu; Fujisato, Toshiya; Nam, Kwangwoo; Kishida, Akio

    2011-01-01

    Our previous research showed that poly(vinyl alcohol) (PVA) nanoparticles incorporating DNA with hydrogen bonds obtained by high hydrostatic pressurization are able to deliver DNA without any significant cytotoxicity. To enhance transfection efficiency of PVA/DNA nanoparticles, we describe a novel method to prepare PVA/DNA nanoparticles encapsulating nanoscaled hydroxyapatites (HAps) prepared by high hydrostatic pressurization (980 MPa), which is designed to facilitate endosomal escape induced by dissolving HAps in an endosome. Scanning electron microscopic observation and dynamic light scattering measurement revealed that HAps were significantly encapsulated in PVA/HAp/DNA nanoparticles. The cytotoxicity, cellular uptake, and transgene expression of PVA/HAp/DNA nanoparticles were investigated using COS-7 cells. It was found that, in contrast to PVA/DNA nanoparticles, their internalization and transgene expression increased without cytotoxicity occurring. Furthermore, a similar level of transgene expression between plasmid DNA and PVA/HAp/DNA nanoparticles was achieved using in vivo hydrodynamic injection. Our results show a novel method of preparing PVA/DNA nanoparticles encapsulating HAp nano-crystals by using high hydrostatic pressure technology and the potential use of HAps as an enhancer of the transfection efficiency of PVA/DNA nanoparticles without significant cytotoxicity. PMID:21773048

  10. Reinforcement of semicrystalline polymers with collagen-modified single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Sanjib; Salvetat, Jean-Paul; Saboungi, Marie-Louise

    2006-06-01

    We report on the enhancement of the mechanical properties of single wall carbon nanotube (SWNT)-polyvinyl alcohol (PVA) composites through functionalization of SWNTs with denatured collagen. In addition to improving compatibility with the matrix, the denatured collagen layer was found to increase the PVA matrix crystallinity, which results in a dramatic enhancement of the Young's modulus (260%), tensile strength (300%), and toughness (700%) well above what can be expected with the classical rule of mixture. A supramolecular organization at the interface is associated with an increase of PVA crystallinity as shown by the x-ray diffraction and differential scanning calorimetry.

  11. Evaluation and modeling of thermal kinetic degradation for PVA doped PbS quantum dot

    SciTech Connect

    Mahmoud, Waleed E.; Al-Heniti, S.H.

    2011-09-15

    Highlights: {yields} Synthesis of PVA doped PbS quantum dots. {yields} Data fitting using integral and differential thermal kinetic models for calculating activation energy. {yields} Prediction of thermal degradation using iso-conversion model. -- Abstract: The kinetic analysis of the thermogravimetric curves for the thermal decomposition processes of PVA/PbS was performed. The samples were heated in nitrogen, with three different heating rates: 10, 20 and 30 {sup o}C min{sup -1}. Various forms of non-isothermal methods of analysis for determining the kinetic parameters were used. The differential and integral models were used to calculate the activation energies. Comparing with pure PVA, the results showed that the maximum activation energy of thermal degradation is achieved for PVA/PbS nanocomposite. Isoconversion model is used for predicting the thermal degradation acceleration. The results showed that the acceleration of thermal degradation for pure PVA was faster than PVA/PbS nanocomposite.

  12. Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

    PubMed Central

    Nuruddin, Muhammad Fadhil; Shafiq, Nasir

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

  13. Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.

    PubMed

    Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

  14. Development of polyvinyl alcohol and apple pomace bio-composite film with antioxidant properties for active food packaging application.

    PubMed

    Gaikwad, Kirtiraj K; Lee, Jin Yong; Lee, Youn Suk

    2016-03-01

    Active antioxidant food packaging films were developed by incorporation of apple pomace (AP) with 1, 5, 10, and 30 % (w/w) into polyvinyl alcohol (PVA) matrix. A complete thermal, structural, mechanical and functional characterization was carried out. The findings of this study showed that the incorporation of AP into PVA films enhanced the total phenolic content and antioxidant properties. As regards the physical properties, higher AP content incorporated into PVA films revealed significantly lower tensile strength, elongation at break and increase in thickness. PVA-AP films exhibited lower transparency value compared to control film. The thermal stability of PVA-AP films was improved and grew with the increasing concentration of AP. FTIR spectra indicated that protein-polyphenol interactions were involved in the PVA-AP films. Rough surface and compact-structure were observed in PVA-AP films. The storage study of soybean oil at 60 °C in PVA-AP pouch showed the antioxidant activity and the effectiveness for delaying its lipid oxidation. PMID:27570286

  15. Alcohol Alert

    MedlinePlus

    ... main content National Institute on Alcohol Abuse and Alcoholism (NIAAA) Main Menu Search Search form Search Alcohol & ... on a single aspect of alcohol abuse and alcoholism. Please click on the desired publication for full ...

  16. 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.

  17. 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. PMID:24299821

  18. Mechanical properties and in vitro characterization of polyvinyl alcohol-nano-silver hydrogel wound dressings

    PubMed Central

    Oliveira, R. N.; Rouzé, R.; Quilty, B.; Alves, G. G.; Soares, G. D. A.; Thiré, R. M. S. M.; McGuinness, G. B.

    2014-01-01

    Polyvinyl alcohol (PVA) hydrogels are materials for potential use in burn healing. Silver nanoparticles can be synthesized within PVA hydrogels giving antimicrobial hydrogels. Hydrogels have to be swollen prior to their application, and the common medium available for that in hospitals is saline solution, but the hydrogel could also take up some of the wound's fluid. This work developed gamma-irradiated PVA/nano-Ag hydrogels for potential use in burn dressing applications. Silver nitrate (AgNO3) was used as nano-Ag precursor agent. Saline solution, phosphate-buffered solution (PBS) pH 7.4 and solution pH 4.0 were used as swelling media. Microstructural evaluation revealed an effect of the nanoparticles on PVA crystallization. The swelling of the PVA-Ag samples in solution pH 4.0 was low, as was their silver delivery, compared with the equivalent samples swollen in the other media. The highest swelling and silver delivery were related to samples prepared with 0.50% AgNO3, and they also presented lower strength in PBS pH 7.4 and solution pH 4.0. Both PVA-Ag samples were also non-toxic and presented antimicrobial activity, confirming that 0.25% AgNO3 concentration is sufficient to establish an antimicrobial effect. Both PVA-Ag samples presented suitable mechanical and swelling properties in all media, representative of potential burn site conditions. PMID:24501677

  19. Nonvolatile memory devices based on poly(vinyl alcohol) + graphene oxide hybrid composites.

    PubMed

    Sun, Yanmei; Lu, Junguo; Ai, Chunpeng; Wen, Dianzhong

    2016-04-20

    Nonvolatile memory devices based on active layers of poly(vinyl alcohol) (PVA) + graphene oxide (GO) hybrid composites have been fabricated. The performance of the ITO/PVA + GO/Al device was compared with that of the ITO/PVA/Al device. The ITO/PVA + GO/Al device showed excellent performance compared to the ITO/PVA/Al device (an ON/OFF resistance ratio of 1.2 × 10(2) at 1 V, VSET ∼ -1.45 V and VRESET ∼ 3.6 V), with a higher ON/OFF resistance ratio of 3 × 10(4) at 1 V and lower operating voltages of VSET ∼ -0.75 V and VRESET ∼ 3.0 V. Furthermore, endurance performance and write-read-erase-reread (WRER) cycle tests manifest that the presence of GO in ITO/PVA + GO/Al devices makes them have better stability and repeatability. The results show that the performance of hybrid devices can be effectively enhanced by the introduction of GO into the PVA matrix. PMID:27056548

  20. Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films

    NASA Astrophysics Data System (ADS)

    Hanafy, Taha A.

    2012-08-01

    Fourier transform infrared (FTIR) spectrum dielectric constant, ɛ', loss tangent, tan(δ), electric modulus, M*, and ac conductivity, σac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ρ and α were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, α-relaxation process splits into αa and αc. This splitting is due to the segmental motion in the amorphous (αa) and crystalline (αc) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

  1. Electrospun Polyvinyl Alcohol/ Pluronic F127 Blended Nanofibers Containing Titanium Dioxide for Antibacterial Wound Dressing.

    PubMed

    El-Aassar, M R; El Fawal, G F; El-Deeb, Nehal M; Hassan, H Shokry; Mo, Xiumei

    2016-04-01

    In this study, an antibacterial electrospun nanofibers for wound dressing application was successfully prepared from polyvinyl alcohol (PVA), Pluronic F127 (Plur), polyethyleneimine (PEI) blend solution with titanium dioxide nanoparticles (TiO2 NPs). PVA-Plur-PEI nanofibers containing various ratios of TiO2 NPs were obtained. The formation and presence of TiO2 in the PVA-Plu-PEI/ TiO2 composite was confirmed by X-ray diffraction (XRD). Transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), mechanical measurement, and antibacterial activity were undertaken in order to characterize the PVA-Plur-PEI/TiO2 nanofiber morphology and properties. The PVA-Plu-PEI nanofibers had a mean diameter of 220 nm, and PVA-Plur-PEI/TiO2 nanofibers had 255 nm. Moreover, the antimicrobial properties of the composite were studied by zone inhibition against Gram-negative bacteria, and the result indicates high antibacterial activity. Results of this antibacterial testing suggest that PVA-Plur-PEI/TiO2 nanofiber may be effective in topical antibacterial treatment in wound care; thus, they are very promising in the application of wound dressings. PMID:26686499

  2. Magnetic hydrogel beads based on PVA/sodium alginate/laponite RD and studying their BSA adsorption.

    PubMed

    Mahdavinia, Gholam Reza; Mousanezhad, Sedigheh; Hosseinzadeh, Hamed; Darvishi, Farshad; Sabzi, Mohammad

    2016-08-20

    In this study double physically crosslinked magnetic hydrogel beads were developed by a simple method including solution mixing of sodium alginate and poly(vinyl alcohol) (PVA) containing magnetic laponite RD (Rapid Dispersion). Sodium alginate and PVA were physically crosslinked by Ca(2+) and freezing-thawing cycles, respectively. Magnetic laponite RD nanoparticles were incorporated into the system to create magnetic response and strengthen the hydrogels. All hybrids double physically crosslinked hydrogel beads were stable under different pH values without any disintegration. Furthermore, adsorption of bovine serum albumin (BSA) on the hydrogel beads was investigated on the subject of pH, ion strength, initial BSA concentration, and temperature. Nanocomposite beads exhibited maximum adsorption capacity for BSA at pH=4.5. The experimental adsorption isotherm data were well followed Langmuir model and based on this model the maximum adsorption capacity was obtained 127.3mgg(-1) at 308K. Thermodynamic parameters revealed spontaneous and monolayer adsorption of BSA on magnetic nanocomposites beads. PMID:27178944

  3. Effect of incorporation of different modified Al2O3 nanoparticles on holographic characteristics of PVA/AA photopolymer composites.

    PubMed

    Li, Yunxi; Wang, Chunhui; Li, Hailong; Wang, Xiaoyi; Han, Junhe; Huang, Mingju

    2015-11-20

    Al2O3 nanoparticles modified with different chemical reagents, prepared by using three chemical dispersants [high definition (HD), sodium dodecyl benzene sulfonate, and cetyl trimethyl ammonium chloride], were doped into photopolymer films in a polyvinyl alcohol/acrylamide (PVA/AA) system, respectively. A 647 nm Ar-Kr laser was used to expose and study the holographic properties of the samples. The research shows that doping Al2O3 nanoparticles into PVA/AA photopolymer film leads to different levels of improvement of the holographic characteristics. The diffraction efficiency of the sample can be raised to 93.8%, the maximum refractive index modulation increased to 2.28×10(-3), the shrinkage can be depressed to 0.8%, and the Bragg mismatch is 0.04°, while the concentration of 10 nm Al2O3 nanoparticles modified by HD dispersant is 1.02×10(-3)  mol·L(-1). PMID:26836540

  4. Studies on photo- and thermal stability of PVA-encapsulated Mn-doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Venkataramana, Savadana; Ramanaiah, K.; Sarcar, M. M. M.

    2016-04-01

    In this study, an aqueous-based synthesis route has been developed to prepare highly luminescent polyvinyl alcohol (PVA)-capped manganese-doped ZnS quantum dots (QDs). The QDs showed markedly blue shift in their optical absorbance, indicating strong quantum size effect and the average diameter of the QDs calculated ~3 nm. The QDs showed high-intensity Mn2+-related orange luminescence at 585 nm with a very low-intensity peak at 430 nm for the surface defect states. X-ray powder diffraction, transmission electron microscopy, UV-visible spectroscopy and spectrofluorometry have been used to characterize the doped QDs. Studies on the thermal and photochemical stability of the photoluminescence properties are carried out, which showed that after 5 h of photoexcitation and 30 min of 70 °C treatments, the nanoparticles retain almost 40 % of their initial quantum yield. Our systematic investigation shows that these PVA-capped Mn:ZnS QDs may be used as fluorescent labels in biological applications.

  5. Properties of novel polyvinyl alcohol/cellulose nanocrystals/silver nanoparticles blend membranes.

    PubMed

    Xu, Xu; Yang, Yi-Qin; Xing, Ying-Ying; Yang, Jiu-Fang; Wang, Shi-Fa

    2013-11-01

    Novel polyvinyl alcohol (PVA) blend membranes containing cellulose nanocrystals (CNs) and silver nanoparticles (AgNPs) were prepared via a simple method. CNs were prepared by sulfuric acid treatment of microcrystalline cellulose. AgNO3 aqueous solution mixed with the CNs aqueous suspension and was reduced by NaBH4 at room temperature. Purified CNs/AgNPs nanocomposites as functional fillers mixed with polyvinyl alcohol to prepare blend membrane. The morphology, mechanical properties, and antibacterial activities of PVA/CNs/AgNPs composite films were investigated. The PVA/CNs/AgNPs composite films were stable and homogeneous. The tensile strength of PVA was increased from 57.02 MPa to 81.21 MPa when filled with CNs/AgNPs. Antibacterial ratio of PVA/CNs/AgNPs composite against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was 96.9% and 88.2%, respectively. The CNs/AgNPs nanocomposites could be applied as bi-functional nanofillers within PVA to improve the mechanical properties and antibacterial activities. PMID:24053842

  6. Heat resistance poly(vinyl alcohol) hydrogel

    NASA Astrophysics Data System (ADS)

    Yoshii, F.; Makuuchi, K.; Darwis, D.; Iriawan, T.; Razzak, M. T.; Rosiak, Janusz M.

    1995-08-01

    Six methods were used to evaluate the heat resistance of poly(vinyl alcohol) (PVA) hydrogel prepared by a combination of electron beam irradiation and acetalization of PVA. The physical properties of the hydrogel depended on the degree of acetilization which was affected by content of water in PVA sheet of acetalization in formaldehyde solution at 60°C. It was found that the optimum water content was 20-30%. The acetalized PVA sheet gave maximum tensile strength in electron beams irradiation at 100 kGy. The tensile strength of the hydrogel film increased to 20 MPa from 14 MPa by the irradiation. Heat resistance of the hydrogel was evaluated by measuring the mechanical properties after sterilization in a steam autoclave at 121°C for 90 min. The tensile strength decreased to 10 MPa whereas the elongation at break increased to 300%. The tackiness of the hydrogel was improved by radiation grafting of acrylic acid. Wholesomeness of the hydrogel as a wound dressing was evaluated by attaching to a burn or wound of the back skin of marmots. Advantages of the hydrogel over a gauze dressing were homogeneous adhesion to the affected parts, easy removal without damage to renewed skin and slightly faster rate of reconstruction of the injured skin.

  7. Alcoholism, Alcohol, and Drugs

    ERIC Educational Resources Information Center

    Rubin, Emanuel; Lieber, Charles S.

    1971-01-01

    Describes research on synergistic effects of alcohol and other drugs, particularly barbiturates. Proposes biochemical mechanisms to explain alcoholics' tolerance of other drugs when sober, and increased sensitivity when drunk. (AL)

  8. Differentiation of Chemical Components in a Binary Solvent Vapor Mixture Using Carbon/Polymer Composite-Based Chemiresistors

    SciTech Connect

    Patel, Sanjay V.; Jenkins, Mark W.; Hughes, Robert C.; Yelton, W. Graham; Ricco, Antonio J.

    1999-07-19

    We demonstrate a ''universal solvent sensor'' constructed from a small array of carbon/polymer composite chemiresistors that respond to solvents spanning a wide range of Hildebrand volubility parameters. Conductive carbon particles provide electrical continuity in these composite films. When the polymer matrix absorbs solvent vapors, the composite film swells, the average separation between carbon particles increases, and an increase in film resistance results, as some of the conduction pathways are broken. The adverse effects of contact resistance at high solvent concentrations are reported. Solvent vapors including isooctane, ethanol, dlisopropyhnethylphosphonate (DIMP), and water are correctly identified (''classified'') using three chemiresistors, their composite coatings chosen to span the full range of volubility parameters. With the same three sensors, binary mixtures of solvent vapor and water vapor are correctly classified, following classification, two sensors suffice to determine the concentrations of both vapor components. Polyethylene vinylacetate and polyvinyl alcohol (PVA) are two such polymers that are used to classify binary mixtures of DIMP with water vapor; the PVA/carbon-particle-composite films are sensitive to less than 0.25{degree}A relative humidity. The Sandia-developed VERI (Visual-Empirical Region of Influence) technique is used as a method of pattern recognition to classify the solvents and mixtures and to distinguish them from water vapor. In many cases, the response of a given composite sensing film to a binary mixture deviates significantly from the sum of the responses to the isolated vapor components at the same concentrations. While these nonlinearities pose significant difficulty for (primarily) linear methods such as principal components analysis, VERI handles both linear and nonlinear data with equal ease. In the present study the maximum speciation accuracy is achieved by an array containing three or four sensor elements, with

  9. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications. PMID:24007370

  10. 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

  11. X-ray analysis and molecular modeling of physical order in chemically disordered polymers

    NASA Astrophysics Data System (ADS)

    Cho, Jaedong

    1999-10-01

    This thesis describes X-ray analysis and molecular modeling of crystal structure of three different polymers; copoly(ester-imide), poly(vinyl alcohol), and poly(2,5-benzimidazole). These polymers form three dimensionally ordered structure despite their considerable chemical diversity as copolymers or solvent complexes. The unifying theme of this work is to advance methods for analysis of disordered structures. The structure of a thermotropic liquid crystalline copoly(ester-imide) has been investigated by X-ray diffraction. X-ray fiber diagrams of as-spun and annealed fibers contain a series of aperiodic layer lines reminiscent to those seen for fibers of other copolymers that have extended chain conformations and completely random monomer sequences. Wide angle X-ray methods have been used to compare the structures of poly(vinyl alcohol) (PVA) with syndiotactic diad (S-diad) contents in the range 51-63%. The fiber diagram of a PVA with 51.2% S-diad content (essentially atactic) is indexed by a monoclinic unit cell with dimensions a = 7.82 +/- 0.03 Å, b = 2.53 +/- 0.01Å (chain axis), c = 5.52 +/- 0.01 Å and β = 91.5 +/- 0.2°. For syndiotacticity-rich PVA with a S-diad content of 63.1%, the unit cell dimensions are a = 7.63 +/- 0.02 Å, b = 2.54 +/- 0.01 Å, c = 5.41 +/- 0.01 Å, and β = 91.2 +/- 0.1°. The latter structure has a theoretical density of 1.40g/mL, which is ~5% higher than the value of 1.34g/mL predicted for atactic polymer. NVT calculations show that the larger unit cell is favored for the atactic polymer, while the smaller unit cell is favored for the 65% syndiotactic polymer. A NPT assembly for the atactic model starting in the contracted unit cell expanded and equilibrated close to the observed, lower density structure. Likewise, a starting model for the 65% syndiotactic polymer packed with the dimensions for the atactic polymer was found to adjust to the observed contracted structure. As-cast films of poly-2,5-benzimidazole (ABPBI) exhibit

  12. Chitosan functionalized poly(vinyl alcohol) for prospects biomedical and industrial applications: A review.

    PubMed

    Rafique, Ammara; Mahmood Zia, Khalid; Zuber, Mohammad; Tabasum, Shazia; Rehman, Saima

    2016-06-01

    Chitin and chitosan are amino polysaccharides having multidimensional properties, such as biocompatibility, biodegradability, antibacterial properties and non-toxicity, muco-adhesivity, adsorption properties, etc., and thus they can be widely used in variety of areas. Although human history mainly relies on the biopolymers, however synthetic materials like polyvinyl alcohol (PVA) have good mechanical, chemical and physical properties. Functionalization of PVA with chitin and chitosan is considered very appropriate for the development of well-designed biomaterials such as biodegradable films, for membrane separation, for tissue engineering, for food packaging, for wound healing and dressing, hydro gels formation, gels formation, etc. Considering versatile properties of the chitin and chitosan, and wide industrial and biomedical applications of PVA, this review sheds a light on chitin and chitosan based PVA materials with their potential applications especially focusing the bio-medical field. All the technical scientific issues have been addressed highlighting the recent advancement. PMID:26893051

  13. A stimuli-responsive and bioactive film based on blended polyvinyl alcohol and cashew gum polysaccharide.

    PubMed

    Silva, Fábio E F; Batista, Karla A; Di-Medeiros, Maria C B; Silva, Cassio N S; Moreira, Bruna R; Fernandes, Kátia F

    2016-01-01

    In this study, a stimuli-responsive, biodegradable and bioactive film was produced by blending cashew gum polysaccharide (CGP) and polyvinyl alcohol (PVA). The film presented malleability and mechanical properties enabling an easy handling. Wetting the film changed the optical property from opacity to levels of transparency higher than 70% and resulted in up to 2-fold increase in its superficial area. Different swelling indexes were obtained varying the pH of solvent, which allows classifying the CGP/PVA film as pH sensitive stimuli-responsive material. The bioactivity was achieved through covalent immobilization of papain, which remained active after storage of CGP/PVA-papain film for 24h in the presence of buffer or in a dry form. These results evidenced that CGP/PVA-papain film is a very promising material for biomedical applications. PMID:26478388

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

    PubMed

    Jensen, Bettina E B; Dávila, Izaskun; Zelikin, Alexander N

    2016-07-01

    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

  15. Synthesis of coprecipitated strontium hexaferrite nanoparticles in the presence of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Davoodi, A.; Hashemi, B.; Yousefi, M. H.

    2011-12-01

    Strontium hexaferrite (SrFe12O19) nanoparticles were synthesized by the chemical coprecipitation method and using polyvinyl alcohol (PVA) as a protective agent. The synthesized samples were characterized by differential thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, particle size analyzer, sedimentation test and vibrating sample magnetometer. In the presence of PVA, the single-phase SrFe12O19 nanoparticles were obtained at low temperature of 650 °C. The average particle size of SrFe12O19 precursor was 15 nm, which increased to 61 nm after calcination at 650 °C. The magnetic measurements indicated that PVA decreased coercivity from 4711 to 3216 Oe with particle size reduction. The results showed that PVA as a protective agent could be effective in decreasing the particle size, calcination temperature and coercivity of SrFe12O19 nanoparticles.

  16. 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

  17. Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells

    NASA Astrophysics Data System (ADS)

    Song, Wei; Markel, David C.; Wang, Sunxi; Shi, Tong; Mao, Guangzhao; Ren, Weiping

    2012-03-01

    The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

  18. Effects of the ZnSe concentration on the structural and optical properties of ZnSe/PVA nanocomposite thin film

    NASA Astrophysics Data System (ADS)

    Halajan, M.; Torkamany, M. J.; Dorranian, D.

    2014-11-01

    This study investigated the effects of ZnSe nanoparticles (NPs) on the structural and (linear and nonlinear) optical properties of polyvinyl alcohol (PVA) thin film. Three samples of ZnSe NP-doped PVA thin films with different concentrations of ZnSe were produced on a glass substrate. The ZnSe NPs were synthesized by pulsed laser ablation of the ZnSe bulk target immersed in distilled water using a 1064 nm wavelength and a high frequency pulsed Nd:YAG laser. The optical bandgap energies of the films were extracted from their UV-Vis-NIR absorption spectra. The corresponding energy bandgaps of the nanocomposite films declined as the ZnSe NPs doping concentration increased. X-ray diffraction analysis was used to characterize the crystalline phases of the ZnSe/PVA nanocomposite films. The concentration-dependent nonlinear optical absorption and nonlinear refraction behaviors of the films after exposure to 532-nm nanosecond laser pulses were investigated using the Z-scan technique. The nonlinear absorption response of the films was positive when measured using an open aperture scheme, which was attributed to the two-photon absorption mechanism. In addition, the nonlinear refraction indices had a negative value and they increased as the concentration of ZnSe NPs in the films increased.

  19. Improvement of water barrier property of paperboard by coating application with biodegradable polymers.

    PubMed

    Han, Jaejoon; Salmieri, Stéphane; Le Tien, Canh; Lacroix, Monique

    2010-03-10

    Biopolymeric coatings were prepared and applied onto paperboard to improve its water barrier property. To prepare whey protein isolate (WPI)/cellulose-based films, WPI and glycerol were dissolved in water with glutaraldehyde (cross-linking agent) and cellulose xanthate. The solution was cast, dried, and insolubilized by entrapment of WPI in regenerated cellulose. Films were combined with beeswax (BW) into a bilayer coating system and then applied onto paperboard by heating compression. Another coating solution consisting of poly(vinyl butyral) (PVB)/zein was prepared by dissolving poly(vinyl alcohol) (PVA) and zein in 70% ethanol with glutaraldehyde and butyraldehyde (functionalization agent). The PVB/zein solution was applied onto paperboard after BW was sprayed. The structure of the PVB/zein-based coatings was analyzed by Fourier transform infrared spectroscopy (FTIR). The water vapor barrier property of coated paperboards was evaluated by water vapor transmission rate (WVTR) measurements. From the FTIR spectra, PVA functionalization after cross-linking and efficient acetalization into PVB were confirmed. WPI/cellulose and PVB/zein coating treatments improved the water barrier properties of paperboard by decreasing the WVTR by 77-78%. Although the BW coating was more efficient (decrease of WVTR by 89%), bilayer coatings composed of BW and polymer coatings had a stronger barrier effect with a decrease of WVTR to 92-95%, hence approaching commercial attributes required to ensure water vapor barrier in paperboard-based food containers (10 g/m(2).day). These results suggest that surface coating by biodegradable polymers may be utilized for the manufacture of paperboard containers in industrial applications. PMID:20155911

  20. A study of the microstructural and diffusion properties of poly(vinyl alcohol) cryogels containing surfactant supramolecular aggregates.

    PubMed

    Tedeschi, Annamaria; Auriemma, Finizia; Ricciardi, Rosa; Mangiapia, Gaetano; Trifuoggi, Marco; Franco, Lorenzo; Rosa, Claudio De; Heenan, Richard K; Paduano, Luigi; D'Errico, Gerardino

    2006-11-23

    Surfactant-containing poly(vinyl alcohol) (PVA) cryogels have been prepared by drying and reswelling hydrogel patches, previously obtained by the freeze/thaw procedure, in decyltrimethylammonium bromide (C10TAB) aqueous solutions. The microstructural and diffusive properties of the resulting material have been characterized by a combined experimental strategy. Gravimetric measurements show that the cryogel maximum swelling is not affected by the surfactant. The surfactant concentration within the cryogel, measured by ion chromatography, is the same as that in the rehydrating surfactant solution. Electron paramagnetic resonance (EPR) spin-probe and small-angle neutron scattering (SANS) measurements show that surfactant self-aggregation in the gel is similar to that in water, occurring at the same critical concentration and resulting in the formation of micellar aggregates whose structure is not affected by the cryogel polymeric scaffold. However, both the micelle intradiffusion coefficients, measured by PGSE-NMR, and the spin-probe correlation times, measured by EPR, indicate that dynamic processes in the hydrogel are much slower than in bulk water. A quantitative analysis of these results suggests that the cryogel polymer-poor domains, in which surfactant molecules are solubilized, have an average dimension of approximately 0.1 microm. Interestingly the experimental data also show that the polymer-poor phase contains more polymer than expected, suggesting that the spinodal decomposition, which occurs during the freezing step of cryogel preparation, is not complete or prevented by ice formation. PMID:17107141