A new procedure for chemical modification of poly(vinyl alcohol) (PVA) was established by a glycosidation reaction of hydroxyl groups in PVA with triacetylated sugar oxazoline 1 . 1H and 13C NMR analyses indicated that triacetylated N‐acetyl‐D‐glucosamine (GlcNAc) was introduced onto a PVA backbone selectively via a β‐O‐glycoside linkage. Deacetylation of triacetylated GlcNAc‐substituted PVA 2 resulted in GlcNAc‐substituted PVA 3 in good yield. These modified PVAs 2 and 3 exhibited solubilities and thermal properties different from the original PVA. 相似文献
A novel type of sol‐gel inorganic‐organic hybrid material coated on glassy carbon electrode used for immobilization of double‐stranded DNA (dsDNA) and study of dsDNA with redox‐active molecules was developed. The hybrid material coating was produced by sol‐gel method with nano hydroxyapatite (HAp)‐polyvinyl alcohol (PVA). The optimum composition of the hybrid material was first examined, and the morphology of the nano HAp‐PVA coatings was investigated with the help of Scanning Electron Microscope (SEM). DsDNA was immobilized in/on the nano HAp‐PVA hybrid coatings by adsorption and the characteristics of the dsDNA/HAp‐PVA/GCE were studied by cyclic voltammetry (CV) using the probes of Co(phen) and Fe(CN) . The results indicate that the dsDNA can be immobilized on the nano porous HAp‐PVA coating effectively and its stability can satisfy the necessity of study on the interactions of dsDNA with redox‐active molecules on the electrode surface. Co(bpy) and Co(phen) were used as the model molecule to study the interactions of dsDNA with redox‐active molecules. Information such as ratio (KOx/KRed) of the binding constant for the oxidized and reduced forms of a bound species, interaction mode, including change in the mode of interaction, and “limiting” ratio K /K at zero ionic strength (μ) can be obtained using dsDNA/HAp‐PVA/GCE with about 2 μg of DNA samples. 相似文献
In this investigation, characterization of the micro structure of three different PVA samples in terms of their degrees of blockiness were performed via 125 MHz 13C‐NMR and 500 MHz ¹H‐NMR measurements. Differences between these PVAs were also discernable by using a high‐performance liquid chromatographic technique employing a reverse‐phase separation mechanism. The results obtained from these studies reveal small but significant differences between the PVAs, which allow a better understanding of the role of these PVAs in the grafting reactions occurring during the emulsion polymerization of vinyl acetate (VAc) using PVA as emulsifier. 相似文献
Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag+ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.
TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. 相似文献
Poly(vinyl alcohol) (PVA) physical hydrogels were prepared by repeated freeze–thawing cycles using aqueous solutions of two PVA samples having different degrees of syndiotacticity, a‐PVA and s‐PVA with 55% and 61% of syndiotactic diads, respectively. The hydrogels were prepared in the presence of different amounts of lactosilated chitosan derivatives (LC) of different molecular weight. The PVA stereoregularity was found to have a dramatic effect on the amount of PVA incorporated into the hydrogels, leading to remarkable differences in the swelling degree and porosity of a‐PVA and s‐PVA hydrogels. A significant amount of LC was retained in the hydrogels after equilibrium swelling. The swelling of the a‐PVA hydrogels was found to increase significantly by increasing the amount of LC while it was only slightly increased in the case of s‐PVA hydrogels. The amount of LC released after equilibrium swelling was lower when chitosan derivatives with higher molecular weights were used. Increased initial concentrations of LC resulted in much higher porosity of the hydrogels. TGA and DSC studies showed that LC is stabilized by the incorporation in the PVA hydrogels. The melting temperature of the crystalline regions of PVA was not significantly influenced by LC. Conversely, the extension of the crystalline domains increased in the presence of LC. The retention of a chitosan derivative bearing β‐D ‐galactose side chain residues makes these hydrogels potentially useful as scaffolds for hepatocytes culture.
Scanning electron micrographs of PVA‐LC hydrogels: (a) a‐PVA; (b) a‐PVA/LC150 80:20; (c) a‐PVA/LC150 50:50. 相似文献
Poly(vinyl alcohol) (PVA) is a promising biocompatible polymer, whose applicability is limited by its narrow processing window. Here, we adopted a facile approach to broaden the processing windows of PVA based on phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (NP‐10P). Thermal analysis shows that both the melting temperature (Tm) and the glass transition temperature (Tg) of PVA decrease noticeably as NP‐10P content increases, indicating good miscibility of NP‐10P with PVA. The thermal degradation kinetics suggests composites display excellent thermal stability compared with neat PVA. The pyrolysis mechanism of PVA before and after modification with NP‐10P varies from chain unzipping degradation followed by chain random scission to chain random scission. The processing window of PVA is broadened from 9°C to 98°C with low content NP‐10P (5 wt%). Moreover, the composites maintain significant mechanical performance and transparency. This work provides an environmentally friendly and economical method to improve the possibility of thermal melt processing for PVA. 相似文献
In this paper we report results of both, material preparation and magnetic characterisation, on CoFe2O4 particles of nanometric size formed by in‐situ precipitation within polymer gels. The size of the particles was controlled within a very narrow volume distribution and its average value was shifted from 2 to 10 nm. The existence of nanoparticles showing, at room temperature, coercive field values between 500 and 900 Oe and saturation magnetisations of about 500 emu/cm3, suggest to use these systems to get magnetic recording media with ultra high density. Poly(vinyl alcohol) (PVA) and Polystyrene (PS) films were prepared from this nanocomposite material. After a magnetic field treatment nanoparticles within the PVA films are free to rotate in response to an applied magnetic field. This PVA based nanocomposite film portends a new class of magnetic material with very little or no electrical and magnetic loss. 相似文献