Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) as a compatibilizer for cellulose acetate/poly(ε‐caprolactone) blends

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) (PVPVAc‐g‐PCL) was synthesized by radical copolymerization of N‐vinyl‐2‐pyrrolidone (VP)/vinyl acetate (VAc) comonomer and PCL macromonomer containing a reactive 2‐hydroxyethyl methacrylate terminal. The graft copolymer was designed in order to improve the interfacial adhesiveness of an immiscible blend system composed of cellulose acetate/poly(ε‐caprolactone) (CA/PCL). Adequate selections of preparation conditions led to successful acquisition of a series of graft copolymer samples with different values of molecular weight ( ), number of grafts (n), and segmental molecular weight of PVPVAc between adjacent grafts (M_n (between grafts)). Differential scanning calorimetry measurements gave a still immiscible indication for all of the ternary blends of CA/PCL/PVPVAc‐g‐PCL (72 : 18 : 10 in weight) that were prepared by using any of the copolymer samples as a compatibilizer. However, the incorporation enabled the CA/PCL (4 : 1) blend to be easily melt‐molded to give a visually homogeneous film sheet. This compatibilizing effect was found to be drastically enhanced when PVPVAc‐g‐PCLs of higher and M_n (between grafts) and lower n were employed. Scanning electron microscopy revealed that a uniform dispersion of the respective ingredients in the ternary blends was attainable with an assurance of the mixing scale of several hundreds of nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of the concentration of capping agent on synthesizing and analyses of Ceria nano-filler using modified co-precipitation technique

The pure crystalline cerium oxide (CeO₂) nanoparticles were synthesized using optimized content of Ce(NO₃)₃. 6H₂O with varying concentrations of sodium hydroxide (NaOH) (0.5, 1, 1.5, and 2 M) as a precipitation agent in presence of 2.5 wt% poly(vinylpyrrolidone) PVP. All the samples are prepared via the modified coprecipitation technique. The synthesized materials have been analyzed using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), laser Raman, high-resolution scanning electron microscope (HR-SEM), and photo luminescence (PL) analyses. The optimized sample was identified with the help of the above studies that could be analyzed through transverse electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) studies. The cubic structure with the Fm-3 m space group has been confirmed through XRD (JCPDS: 81-0792) and Raman analyses. The FT-IR and energy dispersive X-ray spectroscopy (EDX) analyses ascertain the occurrence of Ce and O species. The as-prepared CeO₂ filler (0, 3, 6, 9, and 12 wt%) is dispersed through the optimized polymer electrolyte Poly (styrene-co-methyl methacrylate) P(S-MMA) (27 wt%)–lithium perchloride (LiClO₄) (8 wt%)–ethylene carbonate + propylene carbonate (EC + PC) (1;1 of 65 wt%) complex system using solution casting technique. P(S-MMA) (27 wt%)–LiClO₄ (8 wt%)–EC + PC (1;1 of 65 wt%)–6 wt% of CeO₂ shows the high ionic conductivity 8.13 × 10⁻⁴ S cm⁻¹.     

Advances in three-dimensional nanofibrous macrostructures via electrospinning

Compared with other nanofiber fabrication processes, electrospinning is versatile and superior in production and construction of ordered or more complex nanofibrous assemblies. Besides traditional two-dimensional (2D) nanofibrous structures, electrospinning is powerful in fabrication of three-dimensional (3D) fibrous macrostructures, especially for tissue engineering applications. This article summarizes and reviews recent advances in various promising and cutting-edge electrospinning techniques, including multilayering electrospinning, post-processing after electrospinning, liquid-assisted collection, template-assisted collection, porogen-added electrospinning, and self-assembly. And their formation mechanisms, features, and the challenges of electrospinning have also been discussed. Furthermore, these 3D nanofibrous macrostructures have been demonstrated to have potential applications in tissue engineering, energy harvesting and storage, and filtration.     

Modification of polymers for cardiovascular applications—some routes to bioactive hydrophilic polymers

This paper is concerned with the activation of platelets by polymers, a key-process in the behaviour of prosthetic devices in contact with blood. Platelets are activated by contact with many different types of polymer surfaces, which must therefore be regarded as thrombogenic. Two procedures for reducing thrombogenicity are discussed: (i) the chemical attachment of inhibitors of platelet aggregation and (ii) gross modification of the nature of the surface, e.g. by making it more hydrophilic. For purposes of (i) the potent prostaglandin analogue BW 245C has been used, while for (ii) grafting of poly(ethylene glycol) (PEG) has been explored. Both methods give greatly reduced platelet adhesion inin vitro tests. The second part of the paper deals with the properties of adducts of inhibitors of platelet aggregation (BW 245C, dipyridamole) with water-soluble macromolecules [poly(N-vinyl pyrrolidone), PEG, dextran]. Adducts have been synthesized with terminal and side-chain coupling. On adduction the two inhibitors mentioned show opposite types of behaviour: the molar activity of BW 245C is dramatically reduced, but that of dipyridamole is significantly increased. Remarkable synergistic effects have been recorded for BW 245C adducts. These observations are interpreted in terms of differences in stereochemistry in the drug-receptor interactions. Appropriate chemical techniques for coupling are outlined, attention being drawn to the special uses of haloalkyl- and haloacyl-isocyanates and 2-isocyanatoethyl methacrylate as reagents.     

壳聚糖/聚乙烯吡咯烷酮共混膜的自由体积特性及物性研究

采用正电子湮没技术对壳聚糖/聚乙烯吡咯烷酮(CS/PVP)溶液共混膜的自由体积特性进行了研究,根据3τ计算了其自由体积平均孔穴半径R,当聚乙烯吡咯烷酮组分加入量较少时,R随PVP在共混物中的含量增加开始略有减小,然后逐渐有所增加,PVP含量少于20%时,自由体积孔穴半径小于纯的CS本身,扫描电镜发现共混膜没有发生相分离,PVP与CS相容性好。另外,PVP的加入可以提高膜在湿态环境中的柔软性,共混膜在林格氏液中的降解性能优于纯CS膜。     

改性Y分子筛催化γ-丁内酯气相胺化反应

研究了改性Y分子筛对γ-丁内酯与乙醇胺气相反应合成N-羟乙基吡咯烷酮(NHP)的催化活性,考察了NHP收率与改性阳离子静电场强度的关系,实验结果表明,改性Y分子筛的催化活性与改性阳离子(碱金属、碱土金属、过渡金属等同族金属阳离子)静电场强度呈近似的正相关关系。分析了两种反应物在改性Y分子筛表面的吸附、活化与反应的情况,结果表明,γ-丁内酯与乙醇胺在改性Y分子筛上的气相催化反应符合双功能催化反应机理,副反应主要起因于改性Y分子筛的酸性、反应体系中存在的NHP及反应温度过高等。     

Effect of Impregnation of Iodine Complex on Friction of Anodic Oxide of Aluminum

Polyvinyl pyrrolidone-Iodine complex (PVP-I) molecules were impregnated into the anodic oxide of an aluminum disk specimen. It was rubbed against a silicon nitride ball specimen using a ball-on-disk type friction test rig. Over the limited range of parameters studied (load: 0.2-1.0 N, sliding velocity: 0.6 mm/s, and sliding distance: 1-7 m), the coefficient of friction decreased to a value as low as 0.01 from values of 0.3 to 0.7 for the anodic oxide surface. Single-crystal iodine rubbed against silicon nitride showed a coefficient of friction of 0.1. The low coefficient of friction is attributed to the thin PVP-I film on the relatively hard anodic oxide. The mechanism of coefficient of friction reduction is the same as that of a thin soft film on a hard substrate.     

Hydrothermal synthesis and photoluminescence behavior of CeO2 nanowires with the aid of surfactant PVP

Well-crystalline CeO_2 nanowires were prepared via a surfactant-assisted hydrothermal process.Reaction temperature and reaction time were changed for the determination of optimal synthesis parameters.The as-obtained products were characterized by X-ray diffraction (XRD),high-resolution transmission electron microscopy(HRTEM),and field emission scanning electron microscopy(FESEM).The results show that single crystal CeO_2 nanowires with high yield and good uniformity can be obtained hydrothermally at 180℃...     

Microstructure analysis of N‐vinyl‐2‐pyrrolidone/vinyl acetate copolymers by NMR spectroscopy

N‐Vinyl‐2‐pyrrolidone (V) and vinyl acetate (A) copolymers of different compositions were synthesized by free radical bulk polymerization. The copolymer composition of these copolymers was determined using quantitative ¹³C{¹H} NMR spectra. The reactivity ratios for these comonomers were determined using the Kelen–Tudos (KT) and non‐linear least‐square error‐in‐variable (EVM) methods. The reactivity ratios calculated from the KT and EVM methods are r_V = 2.86 ± 0.16, r_A = 0.36 ± 0.09 and r_V = 2.56, r_A = 0.33, respectively. ¹H, ¹³C{¹H} and ¹H–¹³C heteronuclear shift correlation spectroscopy (HSQC) and ¹H–¹H homonuclear total correlation spectroscopy (TOCSY) were used for the compositional and configurational assignments of V/A copolymers. The ¹³C distortionless enhancement by polarization transfer (DEPT) technique was used to resolve the methine, methylene and methyl resonance signals in the V/A copolymers. © 2002 Society of Chemical Industry     

Thermal and dynamic mechanical behavior of bionanocomposites: Fumed silica nanoparticles dispersed in poly(vinyl pyrrolidone), chitosan,and poly(vinyl alcohol)

Various bionanocomposites were prepared by dispersing fumed silica (SiO₂) nanoparticles in biocompatible polymers like poly(vinyl pyrrolidone) (PVP), chitosan (Chi), or poly(vinyl alcohol) (PVA). For the bionanocomposites preparation, a solvent evaporation method was followed. SEM micrographs verified fine dispersion of silica nanoparticles in all used polymer matrices of composites with low silica content. Sufficient interactions between the functional groups of the polymers and the surface hydroxyl groups of SiO₂ were revealed by FTIR measurements. These interactions favored fine dispersion of silica. Mechanical properties such as tensile strength and Young's modulus substantially increased with increasing the silica content in the bionanocomposites. Thermogravimetric analysis (TGA) showed that the polymer matrices were stabilized against thermal decomposition with the addition of fumed silica due to shielding effect, because for all bionanocomposites the temperature, corresponding to the maximum decomposition rate, progressively shifted to higher values with increasing the silica content. Finally, dynamic thermomechanical analysis (DMA) tests showed that for Chi/SiO₂ and PVA/SiO₂ nanocomposites the temperature of β‐relaxation observed in tanδ curves, corresponding to the glass transition temperature T_g, shifted to higher values with increasing the SiO₂ content. This fact indicates that because of the reported interactions, a nanoparticle/matrix interphase was formed in the surroundings of the filler, where the macromolecules showed limited segmental mobility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008