表面修饰纳米CdS制备中两个重要影响因素及结构表征

利用溶胶-凝胶法制备了PVP表面修饰的CdS纳米晶粒。考察了影响纳米CdS制备的两个重要因素Cd²⁺/S^2-和PVP,及其作用机理。确证表面过剩S^2-和PVP在反应体系中的作用是在较高浓度下制备纳米CdS的两个重要因素,进一步确定了PVP的最佳用量。通过TEM、ED、XRD、FT-IR等手段对合成的纳米粒子进行了结构表征,最小粒径为7～10nm,闪锌矿构型,粒子大小及形貌可通过改变Cd²⁺/S^2-及反应物浓度来控制。最后给出了CdS/PVP纳米晶粒的结构模型。     

配体保护下的Au_(20)团簇吸附和活化CO的理论研究

用密度泛函理论方法计算了CO分子吸附在有机配体聚乙烯吡咯烷酮poly(N-vinyl-2-pyrrolidone)(PVP)保护下的Au20团簇上的稳定构型的结构和性质。配体PVP通过物理吸附主要作用于Au20团簇的顶点位置。与Au20比较,配体的存在有利于CO的吸附和活化,其根本原因是PVP和CO在Au20表面分别作为供电子和吸电子基团产生的协同效应。中性及阴离子Au20团簇对配体和CO的吸附强度不同,前者对PVP吸附作用较强,后者对CO的吸附和活化作用较强。     

HPLC study of chlorin e6 and its molecular complex with polyvinylpyrrolidone

Several HPLC methods with UV detection were developed for qualitative and quantitative analysis of chlorin e(6) and photosensitizer Photolon either in the free form or upon pre-derivatization (methylation) under reversed- and normal-phase conditions. Optimum analysis conditions providing the best resolution of analytes were found at acidic pH where polar groups are completely protonated. The separation was performed by gradient elution with mobile phases of 0.08% trifluoroacetic acid and acetonitrile on an XTerra RP(18) column. The method was specific, accurate and precise, allowing the analysis of chlorin e(6) in the presence of numerous degradation products useful in the manufacturing process and quality control of chlorin e(6) and Photolon.     

高聚物负载型双金属催化剂催化氢转移有机卤化物脱卤

 以甲酸钠为氢转移试剂,以聚乙烯基吡咯烷酮负载PdCl2和其它金属盐制成双金属催化剂PVP－PdCl2－MXn,用于催化有机卤化物脱卤．与负载型单金属催化剂PVP－PdCl2相比,PVP－PdCl2－CdCl2和PVP－PdCl2－HgCl2对氯代芳烃脱氯有高得多的催化活性和脱氯选择性,且偶联副产物显著减少;以对氯苯胺为底物时,双金属催化下的反应时间缩短为单金属催化下的1／8,而脱氯产物收率提高25倍;底物为对氯甲苯时,双金属催化下的偶联副产物仅为单金属催化下的1／390．用IR和TEM技术对PVP负载型金属催化剂进行了表征,并讨论了双金属协同脱卤作用．     

关于高分子凝聚态物理学范式的思考

每门成熟科学必然都存在一个范式,体现该门学科特殊的内在结构、基本理论框架,界定研究范围.但迄今为止,发展迅猛的高分子凝聚态物理学的范式尚未形成.本文梳理、总结了近二、三十年来高分子凝聚态物理学的重要成果,阐述并强调了软凝聚态物质、自相似、分形、标度律、关联效应、溶致凝聚、熵致相变、布朗运动、多体效应和对称破缺等基本概念及其意义,指出探究和凝练高分子凝聚态物理学的范式是摆在当前高分子物理学家面前亟待解决的问题.     

Dispersion polymerization of methyl methacrylate: Mechanism of particle formation

The mechanism for the formation of micron-size polymer particles in the dispersion polymerization of methyl methacrylate was investigated by applying dynamic light scattering to monitor the evolution of the average particle size in the early stages of the polymerization. In addition, the contributions of physically adsorbed stabilizer and graft copolymer were evaluated by measuring the bound, unbound (adsorbed), and free stabilizer, and by determining the amount of added stabilizer required in seeded dispersion polymerizations. Twenty nanometer particles (termed nuclei) were the smallest particles detected and are considered to be formed by aggregation of growing polymer chains precipitating from solution as they exceed their critical chain length. Aggregation of these nuclei with themselves and their aggregates continues until mature and stable particles are formed. This occurs when sufficient stabilizer occupies the particle surface which includes both the polymeric stabilizer [poly(vinylpyrrolidone)] and its graft copolymer which is created in situ. The effects of process variables are discussed based on this mechanistic picture of the dispersion polymerization process. © 1994 John Wiley & Sons, Inc.     

Preparation and Characterization of Poly Vinyl Alcohol/Poly Vinyl Pyrrolidone/Clay Based Nanocomposite by Gamma Irradiation

A series of PVA/PVP/clay nanocomposite were prepared by gamma irradiation with different clay contents of (0.15, 0.3, 1, 1.5, 3 and 5 wt%). The gelation content and swelling behavior were investigated. The morphology and structure of PVA/PVP/clay nanocomposite and dispersion of the clay nanoparticles in the polymeric matrix were examined by infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The introduction of clay into polymeric matrix was investigated by X-ray diffraction pattern (XRD) and Transmission electron microscope (TEM). It is observed that, the increase of the clay content causes a decrease in the swelling percent. The thermal stability studies confirmed that the introduction of clay lead to an increase in the thermal stability. The TEM results showed that the clay nanoparticles are interchelated or exfoliated in the polymeric matrix. Some desirable characteristics such as relatively good swelling and excellent barrier capability against microbe penetration suggested that PVA/PVP/clay nanocomposite can be a good candidate as a wound dressing.     

Synthesis and in vitro degradation of poly(N‐vinyl‐2‐pyrrolidone)‐based graft copolymers for biomedical applications

This work is devoted to the design of a novel family of hydrosoluble biomaterials: poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐based graft copolymers. A synthesis route has been elaborated in which ω‐functionalized PVP is prepared via chain‐transfer radical polymerization, end‐group modified, and subsequently grafted onto a polyhydroxylated backbone, typically dextran or poly(vinyl alcohol). The resulting graft copolymer biomaterials are designed for use in various biomedical applications, particularly as materials with a stronger potential for plasma expansion than already existing products have. The graft copolymers are potentially degradable because the PVP grafts are connected to the polyol backbone via a hydrolytically labile carbonate or ester linkage. The degradation of the graft copolymers was performed in vitro over a period of 6 weeks. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3652–3661, 2002     

PREPARATION OF PERFLUOROOCTANOYL-MODIFIED POLY(VINYL-ALCOHOL)S AND THEIR ADSORPTION AT AN AIR-WATER INTERFACE

Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility inwater. It was shown by experimental measurement at 30.0±0.1℃ that the surface tension of the aqueous solution of thehighest substituted FPVA decreased to 16.6 mN/In at a higher concentration, e.g about 0.1 g/mL. Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobicperfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.     

链式钴微米六方片的溶剂热合成及磁性

以十二硫醇和聚乙烯吡咯烷酮（PVP）为结构导向剂、乙二醇和乙二胺为混合溶剂,利用溶剂热技术成功地制备了Co粒子,并用XRD、SEM、TEM、HRTEM及SQUID对材料的晶体结构、形貌及磁性进行研究. 结果表明：Co粒子属hcp相,呈六方片状,直径约为2 μm,厚度约为80 nm,大量的六方片相互交叉连接成链式结构,并且六方薄片由更为细小的丝带状的纳米片（厚度约为10 nm）构成;室温下样品表现出良好的铁磁性特征,其饱和磁化强度Ms、剩余磁化强度Mr及矫顽力分别为126.6 emu/g、13.7 emu/g和163.4 Oe.