Pressure-dependent glass-transition temperatures of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The pressure-dependent glass-transition temperatures (T-g's) of poly(methyl methacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were determined by pressure-volume-temperature (PVT) dilatometry via an isobaric cooling procedure. The Gordon-Taylor and Fox equations were used to evaluate the relationships between the T-g's and compositions of the PMMA/SAN system at different pressures. The relationships were well fitted by the Gordon-Taylor equation, and the experimental data for T-g positively deviated from the values calculated with the Fox equation. Also, the influence of the cooling rate (during the PVT measurements) on T-g was examined.

Effects of molecular weight and interaction parameter on the glass transition temperature of polystyrene mixtures and its blends with polystyrene/poly(2,6-dimethyl-p-phenylene oxide)

The glass transition temperature (T-g) of mixtures of polystyrene (PS) with different molecular weight and of blends of poly(2,6-dimethyl-p-phenylene oxide) (PPO) and polystyrene with different molecular weight (DMWPS) was studied by a DSC method. For the whole range of composition, the curves of T-g vs composition obtained by experiment were compared with predictions from the Fox, Gordon-Taylor, Couchman and Lu-Weiss, equations. It was found that the experimental results were not in agreement with those from the Fox, Gordon-TayIor and Couchman equations for the binary mixtures of DMWPS, where the interaction parameter chi was approximately zero. However, for the blends PPO/DMWPS (chi < 0), with an increase of molecular weight of PS, it was shown that the experimental results fitted well with those obtained from the Couchman, Gordon-Taylor and Fox equations, respectively. Furthermore, the Gordon-Taylor equation was nearly identical to the Lu-Weiss equation when \chi\ was not very large. Further, the dependence of the change of heat capacity associated with the glass transition (Delta C-p) on the molecular weight of PS was investigated and an empirical equation was presented. (C) 1997 Elsevier Science Ltd.

MISCIBILITY OF POLY(N-VINYL-2-PYRROLIDONE) WITH POLY(ETHER SULFONE) AND 2 PHENOLPHTHALEIN-BASED POLYMERS

Blends of poly(N-vinyl-2-pyrrolidone) (PVP) with poly(ether sulphone) and two phenolphthalein-based polymers, viz. phenolphthalein poly(ether ether sulphone) and phenolphthalein poly(ether ether ketone) were prepared by casting from a common solvent and studied by differential scanning calorimetry. It was found that all the PVP blends are miscible and show a single, composition-dependent glass transition temperature (T(g)). The T(g)-composition dependence has been analysed by the use of the Gordon-Taylor equation. The values of the k parameter in the Gordon-Taylor equation obtained are all not high for the three pairs, in accordance with the fact that there is no strongly specific interaction between PVP and any of the other polymers.

激光热透镜光度分析方法(综述)

激光热透镜效应是1964年Gordon等人首次报道的。他们在研究分子拉曼散射时发现了这一现象,并预言可用于测量溶液中痕量物质的微弱吸收。经过Fang、Swoffod、及Hu等人的努力,使得激光热透镜效应的理论得到了充实和发展,为其在分析领域中的应用打下了基础。1979年Dovichi和Harris首次发表了应用激光热透镜效应进行定量分析,用He-Ne激光为光源建立了单光束实验装置,对Cu-EDTA体系进行了测定。Imasaka等人于1980年采用双光束