Sedimentation studies of single and bi-component polystyrene solutions in analytical ultracentrifugation by comparison of two analysis methods: effect of polymer concentration

Sedimentation analysis with interference detection optics was carried out for pure polymer as well as 1:1 polymer mixture samples as a function of polymer concentration in analytical ultracentrifuge. The data analysis was carried out using analysis programs of Sedfit and VelXLAI to elucidate the advantages and limitations of the analysis methods. The concentration dependency of the sedimentation coefficient was observed and the distributions became narrower on increasing the polymer concentration in both the methods. The peak sedimentation coefficients at different concentrations for both pure polymer as well as polymer mixture samples were same in both the methods though the sedimentation coefficients of the components in the mixture were slightly different from the sedimentation coefficient of the same component, when measured alone. The programs were observed to generate similar information in the case of pure polymer sample; however, in more complex polymer mixture sample, the Sedfit program was observed to have significant difference in the shape of the sedimentation coefficient distributions as well as in the amount of the components detected.     

高分子结构分析方法概述(下)

高分子结构分析是利用现代分析技术,特别是仪器分析方法,测定高分子的链和聚集态结构,探讨结构与性能的关系以及在合成、加工与应用过程中聚合物结构变化规律的一门技术,是高分子科学的重要组成部分。笔者结合高分子研究领域中的一些最新研究动态,简要概述了高分子结构分析的一些主要方法。     

聚合物合成及成型过程研究的近红外光谱技术

介绍目前聚合物合成及成型过程研究的近红外光谱技术，讨论光纤传感技术的应用及光谱信息处理的数学方法，探讨光谱解析的人工神经网络模型；并总结近红外光谱技术在监测聚合物合成及成型过程，测定聚合物的化学组成与结构，以及在线监控聚合物成型过程的应用进展。     

高分子结构分析方法概述(上)

高分子结构分析是利用现代分析技术,特别是仪器分析方法,测定高分子的链结构和聚集态结构,探讨结构与性能的关系以及在合成、加工与应用过程中聚合物结构变化规律的一门技术,是高分子科学的重要组成部分。笔者结合高分子研究领域中的一些最新研究动态,简要概述了高分子结构分析的一些主要方法。     

利福平分子印迹聚合物的制备及其吸附行为

以利福平为模板分子、甲基丙烯酸为功能单体、乙二醇二甲基丙烯酸酯为交联剂,制备了利福平分子印迹聚合物. 采用平衡结合方法和Scatchard模型评价了该聚合物的结合特性,考察了其吸附行为. 结果表明,利福平分子印迹聚合物中形成了两类不同的结合位点,得到高亲和力结合位点的离解常数和最大表观结合量分别为31.5 mg/mL和23.34 mg/g,低亲和力结合位点的离解常数和最大表观结合量分别为9.22 mg/mL和12.86 mg/g. 实验结果显示,利福平分子印迹聚合物对利福平呈现出了高的选择吸附特性.     

Polymer polarity and surfactant adsorption

The effect of polymer polarity on surfactant adsorption from aqueous solution is discussed. The analysis assumes that surfactant adsorption at the polymer–water interface follows a Langmuir-type adsorption isotherm and the free energy of adsorption is controlled by the interfacial tension of the interface. Saturation adsorption given by the area per molecule of surfactant at the critical micelle concentration (CMC) of the surfactant is related to the polymer–water interfacial tension and the polarity of the polymer surface, calculated from the polar and dispersion contributions to the polymer surface energy. Available data on the area per molecule of sodium lauryl sulfate on various polymer surfaces have been used to test satisfactorily the above analysis. The analysis is used to interpret some of the observations relating to surfactant adsorption encountered in the emulsion polymerization of polar monomers and particle size determination of latexes by the soap titration method. Further, potential utility of such area per molecule data to characterize the nature of polymer surfaces is also discussed.     

Adhesion between polymer substrates and plasma films from tetramethylsilane and tetramethyltin by glow discharge polymerization

Adhesion between various polymer substrates and plasma films, which had been prepared from either tetramethylsilane or tetramethyltin by glow discharge polymerization and deposited on the surface of the polymer, was evaluated by the Scotch tape test and by lap-shear strength. It was found that the plasma films exhibited fairly good adhesion to the polymer substrates (with the exception of polypropylene). The position where failure occurred was determined by X-ray fluorescence analysis, scanning electron microscopy and energy diffractive X-ray analysis. This position was at an inner layer of the plasma film (cohesive failure of plasma film), within the polymer substrate (material failure of polymer) or at the interface between polymer substrate and plasma film (adhesive failure) depending upon the polymer substrate. These results indicate an important aspect of durability of surface modification by glow discharge polymerization.     

增塑型锂离子电池聚合物电解质

从组成聚合物电解质的聚合物基材和电解液两方面进行分析,介绍了最近几年凝胶型、微孔型和复合型聚合物电解质的研究现状,比较了它们的制备方法、性能和特点,探讨了锂盐、增塑剂、离子液体和单离子导体等对聚合物电解质性能的影响,并简要评述了聚合物锂离子电池未来发展的前景趋势。     

药物柳胺酚分子印迹聚合物的制备及识别性能研究

采用分子印迹技术合成了对药物柳胺酚有高选择性的印迹聚合物,通过平衡吸附及高效液相色谱的方法对聚合物进行了评价。结果表明,制备的印迹聚合物对模板分子有很强的吸附能力和良好的选择性,可以很好的分离模板分子及其结构类似物。     

Pyrolysis-GLC applied to composition analysis,general characterisation and the detailed specification of polymers

Since its inception in the late 1950s, pyrolysis gas-liquid chromatography has rapidly become an important tool for the polymer chemist. Applications range from polymer characterisation to the elucidation of polymer degradation mechanism. Typical analytical applications include the characterisation of complex polymer mixtures, the assessment of copolymer composition and microstructure, structural analysis and the assignment of polymer tacticity. Recent advances in the technique are reviewed and examples of results are given. Most current GLC equipment is perfectly adequate for polymer/copolymer analysis provided that certain basic requirements are satisfied. For polymer characterisation, furnace and Curie-Point methods are not the most appropriate and even simple filament methods are preferable to these. Refined filament techniques are the most suitable methods for studying degradation kinetics, and can provide a highly precise specification of polymer structure. For example, studies on the dependence of the specific rate of pyrolysis can distinguish anionic and free-radical polymers. Analysis of the energetics of the degradation may indicate the activation energy for end initiation; this may be compared with bond-strengths of possible end-group structures. A similar process can be used to elucidate the nature of possible ‘weak-links’ within the polymer backbone. The effects of polymer modification, for example oxidation, may also be assessed. Examples are quoted for these situations and the requirements of the technique are stressed.     

Role of Different Plasticizers in Li-Ion Conducting Poly(Acrylonitrile)-Poly(Methyl Methacrylate) Hybrid Polymer Electrolyte

In this work, polymer electrolytes composed of PAN/PMMA/LiClO₄ with different plasticizers are prepared using solvent casting technique. Ionic conductivity of the electrolytes is evaluated with the help of ac impedance study at various temperatures. Structural and the complexation of the prepared electrolytes are studied by XRD and FTIR analysis, respectively. Thermogravimetric/differential thermal analysis (TG/DTA) is used to find the thermal stability of the polymer electrolytes. PAN/PMMA/EC/LiClO₄-based plasticized polymer electrolyte is found to possess optimal properties in terms of conductivity and thermal stability. Porous nature of the polymer gel electrolytes is also confirmed by SEM analysis.     

Structure,interaction and thermal study in electrolyte of polyethylene oxide/silica/ammonium thiocynate nanocomposites

Composite polymer electrolyte consisting of polymer (polyethylene oxide, PEO) and nanosized ceramic filler with different concentrations of salt have been synthesized and characterized. X‐ray diffraction analysis shows that polymer salt complex has been intercalated into the naometric silicate layers. IR spectra reveal that the polymer structure in the ceramic interlayer is similar to that of polymer salt complexes and there is a strong interaction between PEO:SiO₂ and polymer‐salt complexes. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

POLYFLOW在高分子成型加工中的应用研究进展

在聚合物制品外形控制和性能调控过程中,高分子熔体的流动分析对于研究高分子成型工艺至关重要.POLYFLOW软件在高分子成型加工中的应用日渐广泛.本文深入分析了POLYFLOW在挤出、吹塑和热成型等方面的应用,重点介绍了挤出过程中的正向流动仿真和逆向口模设计,最后对POLYFLOW在高分子成型加工中的应用研究方向进行展望...     

热重分析技术及其在高分子材料领域的应用

简要介绍热重分析技术发展史、热重分析技术基本原理,以及热重分析在高分子材料领域的应用。热分析是研究物质的物理化学性质随温度变化的一类技术,随着计算机在线分析和反馈控制技术的发展及多种手段联用技术的发展,热分析技术也得到了显著的发展。热分析是高分子的常规表征手段,可用于表征结构相变,分析残余单体和溶剂含量,添加剂的检测,热降解的研究;同时被用于产品质量的检测,生产过程的优化及考察外因对高分子性质的影响等。     

沉淀聚合法制备Boc-L-苯丙氨酸印迹聚合物

以Boc-L-苯丙氨酸为模板分子,应用沉淀聚合法制备了对Boc-L-苯丙氨酸具有特异性吸附的分子印迹聚合物。通过平衡吸附和高效液相色谱的方法对印迹聚合物进行评价,结果表明印迹聚合物具有高吸附效率和选择性,实现了消旋混和物的快速基线分离。     

Effects of alkali halides on the thermal decompositions of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate)

The effects of alkali halides on the nonoxidative thermal degradations of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate) are described. The magnitudes of the effects of various alkali halides on polymer thermal degradation were found to depend on the salt and the polymer. Mass spectrometric analysis of volatiles evolved during polymer degradation detected alkyl halides formed by reactions between the salts and polymers. Compared to poly(methyl methacrylate), more alkyl halide was evolved from samples containing alkali halides and poly(2-hydroxy ethyl methacrylate). To varying degrees, salts also catalyzed ester decomposition reactions for this polymer. Infrared spectroscopic analysis results showed that carboxylate salts, carbonate, and carbon monoxide were formed by heating polymer/salt mixtures. © 1996 John Wiley & Sons, Inc.     

Creep analysis of polymer structures

One of the important aspects in designing polymer structures and predicting their lifetime is the computation of time-dependent deformation. A tensile creep law for constant uniaxial stress was developed using talc-filled polypropylene as an example. A simplified finite-element creep analysis technique for polymer structures was developed with only one time step, an isochronous stress-stress formulation, and a deformation plasticity-type analysis, With an elastic analysis and this one-step nonlinear analysis for a given time and temperature, the displacement of a critical location in the polymer structure can be calculated for any time and temperature without further finite-element analysis. Comparisons of calculations with this one-step analysis and with the standard time-stepping analysis and experimental results for a beam in bending and a plate with a hole demonstrate the usefulness of this approach.     

Analysis of bisphenol A sulfonate–carboxylate polymer

The method of analysis for a polycondensation polymer containing the carboxylate and sulfonate functional groups has been devised. A combination of infrared spectroscopy and combustion analysis provides a simple and accurate determination of the monomeric units and their molar distribution in the polymer.     

Synthesis and properties of a new crosslinkable polymer containing benzoxazine moiety in the main chain

Using difunctional phenolic and amine compounds, a new polymer with benzoxazine groups in the main chain has been synthesized through the Mannich reaction of a phenol, formaldehyde, and an amine. ¹H and ¹³C nuclear magnetic resonance spectroscopies, Fourier transform infrared spectroscopy, size exclusion chromatography, and elemental analysis are used to characterize the resulting polymer. Polymer with molecular weight of approximately 10,000 Da is obtained. The resultant polymer has a moderately broad polydispersity index. The thermal properties of the polymer have also been studied by differential scanning calorimetry and thermogravimetric analysis.     

Studies on structural,dielectric and charge transport properties of PVA:LiBr solid polymer electrolyte films

In the present study, solid polymer electrolytes (SPEs) based on poly (vinyl alcohol) (PVA) doped with lithium bromide (LiBr) were prepared by solution casting method. Fourier transform infrared spectroscopy results affirm the complexation of LiBr with PVA. X-ray diffraction results exhibit the increase of amorphous nature of the polymer electrolytes, which is also observed in scanning electron microscopy images and atomic force microscopy topographs. Thermogravimetric analysis thermographs endorse the increase of thermal stability of the polymer due to doping. Dielectric studies exhibit non-Debye nature of the polymer electrolytes. Conductivity spectra reveal the maximum ionic conductivity (1.15 × 10⁻⁴ S/cm) for 20 wt% LiBr/PVA electrolyte at ambient temperature. Impedance analysis reveals the decrease of ionic relaxation in the polymer electrolytes and the studied transport properties of the electrolyte show that the major contribution to the conduction in this polymer electrolyte is ions.