Ultrasonic Degradation and Copolymerization of Poly (Vinyl Alcohol) with Acrylonitrile

The ultrasonic degradation of poly(vinyl alcohol) (PVA) in aqueous solution and copolymerization of PVA with acrylonitrile (AN) were studied. It is confirmed that the rate of degradation of PVA follows the kinetic equation suggested by Baramboim. Both water-soluble and water-insoluble copolymer can be obtained by changing the irradiation time or the amount of AN added to the aqueous solution of PVA. The structure of the copolymer was identified by IR, MS, PGC, and x-ray diffraction. The copolymer prepared is mainly a block one. By irradiating 2% PVA/AN (1/1.6, w/w) at 20 ± 1°C and 21. 5 kHz with 490 W for 28 min, the yield of water-soluble copolymer is 25.49%, the AN content in which is 13.98%. After 100 min, with the weight ratio between PVA and AN 1/4, the yield of the water-insoluble copolymer amounted to 296.01%, the AN content in which is 75.56%.     

Characterisation of Redox Initiators for Producing Poly(Vinyl Alcohol) Hydrogels

Summary: This work focuses on the characterisation of ascorbic acid/persulphate initiating system. Three different persulphates were used (ammonium, potassium and sodium), and a range of initiator concentrations were tested. Gel time, gel quality, initiator toxicity, and cell survival upon encapsulation were measured. No significant differences were observed between the three types of persulphates. Higher concentrations of the initiators resulted in faster gel times (5min for 0.05wt% initiator) and higher quality gels (less than 20% sol fraction), although the lower initiator concentrations were better in terms of cell growth inhibition and survival upon encapsulation. Overall, this system shows great promise for use in biomedical applications, however there is a need to minimise the initiator concentration to increase cell compatibility while maintaining a high enough concentration for adequate gel formation.     

Grafting of Vinyudene Chloride. Model Studies with Poly(Vinyl Alcohol) as Substrate

The modification of coatings resins by graft polymerization of vinylidene chloride should produce a coatings binder with improved barrier properties. For superior color stability, vinylidene chloride must be copolymer-ized with other monomers such as alkyl acrylates and methacrylates. Ceric ion initiation was used to graft vinylidene chloride free-radically onto a model alcohol-containing polymer, polyvinyl alcohol. The effects of various reaction parameters on vinylidene chloride grafting were studied. Graft copolymers were characterized using selective solvent extraction, FTIR, SEM, XES, DSC, and x-ray diffraction.     

低分子物质在聚乙烯醇水凝胶中的扩散

水凝胶是指一种网络结构中含大量水,而不溶于水的高分子材料。近年来,发现聚乙烯醇(PVA)水溶液在低温冷冻一段时间,可形成强度较高的水凝胶弹性体,用这种水凝胶制得的固定化增殖细胞凝胶,在生物工程材料开发中取得了很好的效果。本文旨在研究低分子物质在PVA水凝胶中的扩散性能。     

Liposomal Encapsulation of Carvacrol to Obtain Active Poly (Vinyl Alcohol) Films

Lecithins of different origins and compositions were used for the liposomal encapsulation of carvacrol within the framework of the development of active films for food packaging. Liposomes were incorporated into aqueous polymeric solutions from fully (F) and partially (P) hydrolysed Poly (vinyl alcohol) (PVA) to obtain the films by casting. The particle size distribution and ζ-potential of the liposomal suspensions, as well as their stability over time, were evaluated. Liposomal stability during film formation was analysed through the carvacrol retention in the dried film and the film microstructure. Subtle variations in the size distributions of liposomes from different lecithins were observed. However, the absolute values of the ζ-potential were higher (−52, −57 mV) for soy lecithin (SL) liposomes, followed by those of soy lecithin enriched with phosphatidylcholine (SL-PC) (−43, −50 mV) and sunflower lecithin (SFL) (−33, −38 mV). No significant changes in the liposomal properties were observed during the study period. Lyotropic mesomorphism of lipid associations and carvacrol leakage occurred to differing extents during the film drying step, depending on the membrane lipid composition and surface charge. Liposomes obtained with SL-PC were the most effective at maintaining the stability of carvacrol emulsion during film formation, which led to the greatest carvacrol retention in the films, whereas SFL gave rise to the least stable system and the highest carvacrol losses. P-PVA was less sensitive to the emulsion destabilisation due to its greater bonding capacity with carvacrol. Therefore, P-PVA with carvacrol-loaded SL-PC liposomes has great potential to produce active films for food packaging applications.     

环己酮与查尔酮的无溶剂Michael加成反应

以环己酮和查尔酮为原料, 在 NaOH 存在下无溶剂室温研磨反应, 非常方便地得到Michael加成产物. 该方法具有反应条件温和、操作简单和产率较高等优点, 并通过IR, ¹H NMR和元素分析确证产物的结构.     

The Structure of Water-Swollen Poly(Vinyl Alcohol) and the Swelling Mechanism

The swelling mechanism of poly(vinyl alcohol) (PVA) in a wide range of the equilibrium swelling index, of 7–153% (with H₂O) and of 12-297% (with D₂O), was investigated by IR, Raman, and broad-band NMR spectroscopy. Analysis of the spectral data obtained confirmed the presence of hydration water (bonded with polymer-free hydroxyl groups) and condensation water (not having been bonded with polymer hydroxyl groups) in poly(vinyl alcohol) swollen samples at low (～7%) and high (>23%) equilibrium swelling indexes, respectively. Moreover, it revealed the intra- and inter-molecular hydrogen bonds breaking in the polymer swollen to higher extent (equilibrium swelling index > 85%).     

细菌视紫红质／聚乙烯醇复合膜的制备及相关功能研究

细菌视紫红质（bR)是一种独特的光敏蛋白，具有光致变色和光驱质子泵功能 。将bR蛋白包埋于聚乙烯醇（PVA）基质中，制备了bR/PVA复合膜。利用紫外－可 见分光光度计和自制的毫秒级动力学光谱仪，检测了样品的吸收光谱和光循环M中 间体在脉冲光激发下随时间的变化；同时，利用凝胶扫描成像仪及相关分析软件考 察了样品成膜后的均匀程度。实验表明：bR/PVA复合膜具有良好的均匀性、透明性 和力学性能，而且bR蛋白保持了原有的生物活性和光学性质，bR与M中间体之间能 达到一种光可控制的双稳态，M中间体的寿命也得到了显著的延长，证实了bR可以 提供一个用于信息存储的模型材料。     

Synthesis of Poly(Vinyl Alcohol) and/or Poly(Vinyl Acetate) Particles with Spherical Morphology and Core-Shell Structure and its Use in Vascular Embolization

Poly(vinyl alcohol), PVA, is the most frequently used material in embolization of tumors, aneurisms and arteriovenous malformations due to its low toxicity, good biocompatibility and desirable physical properties. It is well known that PVA particles cannot be prepared by direct polymerization of vinyl alcohol. Its synthesis is typically performed by the suspension polymerization of vinyl acetate to produce poly(vinyl acetate), PVAc, followed by the saponification of the PVAc particles. This work shows that, using the suspension polymerization technique, it is possible to obtain spherical particles with a core-shell structure of PVA/PVAc with regular morphology, instead of particles with irregular shapes and sizes, as usually found in many commercial embolization products. Therefore, this work presents the production of PVA/PVAc spherical particles that can be used to occlude blood vessels, eliminating the disadvantages of commercial PVA. In vivo clinical tests with white “New Zealand” rabbits undergoing kidney inflammation reaction have shown that these spherical particles are much more efficient for vascular embolization.     

聚乙烯醇明胶混合水溶液的静电纺丝

将聚乙烯醇与明胶混合水溶液进行静电纺丝,制备了聚乙烯醇与明胶混合超细纤维及其电纺膜,研究了混合纺丝液的组成对纺丝液的粘度、表面张力和电导率的影响,观察了纤维的微观形貌,并对电纺膜进行了差示扫描量热测定.结果表明:当混合液中明胶含量小于20 9/6时,静电纺丝可以稳定进行.随着明胶含量由5%逐渐增加至25%,混合超细纤维的平均直径先是由260nm逐渐下降至207 nm而后又逐渐增加至320 nm.明胶的含量低于15%时,不影响其混合电纺膜中PVA的结晶.     

Structure and Mechanical Properties of Chitosan/Poly(Vinyl Alcohol) Blend Films

Summary: The origins of the thermal and mechanical properties of chitosan and poly(vinyl alcohol) (PVA) with inter- and intra-hydrogen bonds were investigated systematically by using X-ray, DSC, positron annihilation and viscoelastic measurements. Based on their individual properties, the characteristics of the blend films were estimated in relation to their morphology and mechanical properties as a function of chitosan content. The characteristics of the blend films were also analyzed in terms of the deviation from a simple additive rule of chitosan and PVA content. These results suggested that the miscibility of chitosan and PVA could be ensured by entanglement of the amorphous chain segments of chitosan and PVA. Further detailed analysis revealed that the chitosan content on the film surface is higher than that of the admixture content of chitosan after elongation, although the chitosan and PVA chains were crystallized independently. The elongation could be achieved for the blend films whose PVA content was higher than 50% and the drawn blend films were transparent. Thus, it may be expected that sufficiently entangled meshes formed between chitosan and PVA amorphous chains within the film, the PVA content being higher than 50%, were maintained under the elongation process.     

Irradiation of Crosslinked, Poly(Vinyl Alcohol) Blended Hydrogel for Wound Dressing

In order to obtain a more ideal hydrogel wound dressing, crosslinked hydrogel films blended with polyvinyl alcohol (PVA), polyvinyl pyrrolidone, kappa-carrageenan (KC), and powder silk were prepared by electron beam, and their physiochemical properties were investigated as a combination of function factors. The experimental results showed that the gel fraction of the hydrogel films depended mainly on irradiation dose and the monomer concentration of the polymers, the properties of hydrogel could be greatly extended or improved by blending homopolymers. The rate of gel formation of the hydrogel was raised, and the water evaporation from hydrogel could be retarded after mixing with KC, while the tensile strength of hydrogel films were obviously increased after mixing with silk. Toxicity and healing effect of PVA/PVP/KC/silk blended hydrogel films as wound dressings were evaluated. The irradiated blended hydrogel showed satisfactory properties for wound dressing, the hydrogel did not induceany acute general toxic effects, and it is effective for fast healing of wound.     

Immobilized Laccase on Activated Poly(Vinyl Alcohol) Microspheres For Enzyme Thermistor Application

Poly(vinyl alcohol) (PVA) microspheres were prepared by inverse suspension crosslinked method, with glutaraldehyde as a crosslinking agent. PVA microspheres activated with aldehyde groups were employed for Trametes versicolor laccase immobilization. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the activated PVA microspheres and PVA microspheres with immobilized laccase (Lac/PVA microspheres), which show that laccase was successfully immobilized on the PVA microspheres. The optimum pH and temperature coupling conditions for the immobilized laccase were determined to be 3.3 and 30 °C, respectively. Residual activity was also investigated by soaking the immobilized laccase in organic solvents at different concentrations, proving it chemically stable. Immobilized laccase exhibited good storage stability at 4 °C. The enzyme biosensor showed good performance in 2,2-azinobis(3-ethylthiazoline-6-sulfonate) and bisphenol A, with concentration ranges of 2 to 8 mM and 0.05 to 0.25 mM, respectively. Therefore, PVA microspheres may have high potential as support for enzyme thermistor applications.     

Michael Addition Reaction of Fluorinated Nitro Compounds

The Michael addition reactions of fluorinated nitro compounds with electron deficient olefins to give γ‐fluoro‐γ‐nitro‐esters, nitriles and ketones which bear a fluorinated quaternary carbon center were reported. The reactions were promoted by TMG, affording the desired adducts in acceptable to good yields.     

Preparation and Characterization of Blend Films of Poly(Vinyl Alcohol) and Sodium Alginate

Blend films of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. This blend films were characterized by tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The miscibility in the blends of PVA and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition‐dependent glass transition temperatures (T_gs), indicating that the blends are miscible. FT‐IR studies indicate that there is the intermolecular hydrogen bonding interactions, i.e. –OH…^?OOC– in PVA/NaAlg blends. The blend films also exhibited the higher thermal stability and their mechanical properties improved compared to those of homopolymers.     

Application of Crosslinked Ionic Poly(Vinyl Alcohol) Nanogel as Adsorbents for Water Treatment

Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu²⁺) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu²⁺ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb²⁺) and cadmium (Cd²⁺) were tested. The maximum of Cu²⁺ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents.     

The Synthesis of Poly(Vinyl Alcohol) Grafted with Fluorinated Protic Ionic Liquids Containing Sulfo Functional Groups

There has been an ongoing need to develop polymer materials with increased performance as proton exchange membranes (PEMs) for middle- and high-temperature fuel cells. Poly(vinyl alcohol) (PVA) is a highly hydrophilic and chemically stable polymer bearing hydroxyl groups, which can be further altered. Protic ionic liquids (proticILs) have been found to be an effective modifying polymer agent used as a proton carrier providing PEMs’ desirable proton conductivity at high temperatures and under anhydrous conditions. In this study, the novel synthesis route of PVA grafted with fluorinated protic ionic liquids bearing sulfo groups (–SO₃H) was elaborated. The polymer functionalization with fluorinated proticILs was achieved by the following approaches: (i) the PVA acylation and subsequent reaction with fluorinated sultones and (ii) free-radical polymerization reaction of vinyl acetate derivatives modified with 1-methylimidazole and sultones. These modifications resulted in the PVA being chemically modified with ionic liquids of protic character. The successfully grafted PVA has been characterized using ¹H, ¹⁹F, and ¹³C-NMR and FTIR-ATR. The presented synthesis route is a novel approach to PVA functionalization with imidazole-based fluorinated ionic liquids with sulfo groups.     

Preparation of a Rapidly Forming Poly(ferrocenylsilane)‐Poly(ethylene glycol)‐based Hydrogel by a Thiol‐Michael Addition Click Reaction

The synthesis of a rapidly forming redox responsive poly(ferrocenylsilane)‐poly(ethylene glycol) (PFS‐PEG)‐based hydrogel is described, achieved by a thiol‐Michael addition click reaction. PFS bearing acrylate side groups (PFS‐acryl) was synthesized by side group modification of poly(ferrocenyl(3‐iodopropyl)methylsilane) (PFS‐I) and characterized by ¹H NMR, ¹³C NMR, and FT‐IR spectroscopy. The equilibrium swelling ratio, morphology, rheology, and redox responsive properties of the PFS‐PEG‐based hydrogel are reported.

     

Syntheses of Vinyl Sulfoxide/Vinyl Acetate-Type Copolymers

The homopolymerization of a series of alkyl vinyl sulfoxides (CH₂[dbnd]CHSOR; R = CH₃ (MVSO), C₂H₅ (EVSO), t-C₄H₉ (BVSO)) and their copolymerization with vinyl acetate (VAc) with 2,2′-azobisisobutyronitrile (AIBN) as initiator at 60°C was attempted. MVSO was found to homopolymerize radically, but EVSO and BVSO were not. Poly-MVSO is soluble in chloroform, methanol, DMSO, and water, but insoluble in acetone and benzene. MVSO and EVSO were found to copolymerize with VAc, but BVSO was not. The copolymerization parameters obtained for both systems were as follows; r₁(MVSO) = 2.23, r₂ (VAc) = 0.09, and r₁(EVSO) = 3.40, r₂ (VAc) = 0.11, respectively. MVSO/vinyl alcohol (VA) copolymers were obtained through the saponification of MVSO/VAc copolymers by sodium hydroxide in methanol. The solubility of MVSO/VAc and of MVSO/VA copolymers toward various solvents was examined, and it was observed that the sulfoxide comonomer has a tendency to give amphiphilicit to poly(vinyl acetate) and poly(vinyl alcohol). The 24 mol% MVSO containing VAc copolymer is soluble in both benzene and water.     

Modification of Nano-alumina Surface by Michael Addition Reaction

With recent interest in polymer-based nanocomposites, nano-alumina has receivedconsiderable attention because of their high hardness, high strength and good wearresistance. Improvements in mechanical, tribological, conductive and barrier propertiesof some…