The miscibility of binary polymer blends of polystyrene/poly (styrene-co-acrylonitrile) (PS/SAN) was predicted based on both Flory's equation of state theory (EOS) and Wolf's theory on binary polymer blends of the A/A-B type. The calculating results suggested that PS/SAN blend exhibits the upper critical solution temperature (UCST) behavior within acrylonitrile's volume fraction range of 4-20%. PS/SAN blends were studied with the Small Angle Light Scattering (SALS) method to test the theoretical prediction. It showed that PS/SAN (AN: 20vol.%) blend (49/51wt.%) displays UCST behavior and the UCST temperature was about 171 8C. The calculating and the experimental results were in accordance with each other relatively well.

The thermodynamic phase behaviour of blends composed of two random copolymers of polystyrene-co-methyl methacrylate (SMMA) and polystyrene-co-acrylonitrile (SAN) was studied using a modified Florys equation of state (EOS) theory. Light scattering measurements indicated that SMMA and SAN are miscible within certain copolymer composition ranges and exhibit lower critical solution temperature behaviour. The temperature, at which phase separation is observed, changes with the copolymer composition. The segmental interaction energy parameters XS-MMA, XS-AN and XMMA-AN were calculated using a binary interaction model by fitting the lowest temperature in the calculated spinodal boundary from EOS theory to the experimental data for several copolymer compositions. It was found that EOS theory, originally used for binary polymer solutions, could be modified and successfully extended to simulate the phase boundaries of random copolymer blends, when using Flory's mixing rule to calculate the equation of state parameters for the copolymers from those of the constituent monomer segments.

The thermal degradation of poly(phenylene sulfide sulfone) PPSS was studied by thermogravimetricanalysis to determine the reaction mechanism. Several tests were carried out at different heating rates. The influence of the heating rate in dynamic measurements (5-40Cmin) on kinetic parameters, such as activation energies, was also studied. The activation energy of the solidstate process was determined to be 214kJ/mol using Kissinger's method, which does not require knowledge of the reaction mechanism. The value of the activation energy obtained using Flynn-Wall-Ozawa method was in agreement with that using Kissinger's method. Different reaction mechanisms were used to compare with this value. Also the experimental data were compared to master curves. Analysis of the experimental results suggested that the actual reaction mechanism was a Dn deceleration type.

The phase boundaries of untreated silica-filled and unfilled poly(methyl methacrylate) (PMMA)/poly(styrene-stat-acrylonitrile) (SAN) blends were determined by dynamic shear rheology. The Flory-Huggins interaction parameter was also calculated according to the determined phase diagram after taking into account the composition change of the mixture matrix due to the incorporation of filler. It was found that, in comparison with the unfilled PMMA/SAN blends, the phase separation temperature of the filled polymer blend was increased, and the thermodynamic interaction parameter was correspondingly decreased, suggesting that the phase stability of PMMA/SAN mixtures is enhanced by the incorporation of silica. A mechanism for this phenomenon was proposed based on the selective adsorption of PMMA chains on silica particles. The adsorption of high molecular weight fraction of PMMA chains onto the surface of silica particles would decrease the average molecular weight of PMMA in the bulk matrix that would favor the miscibility of PMMA/SAN blends in the matrix, therefore leading to the increase of the phase separation temperature of blends in the bulk. In addition, the adsorption of PMMA also changed the blend composition ratio in the bulk matrix, which would cause a complicated influence on the phase separation temperature too.