The effect of solvents on the morphology and properties of styrene-butadiene-styrene（SBS, \{Mn=\}99 575, Mw/Mn=1.3, S/B=3∶7） triblock copolymer films was studied in this paper. The solvents used in the study are: ethylmethylketone, a preferential solvent for the PS block; toluene, a non-preferential solvent for both the PS and the PB blocks; and mixed hexane/cyclohexane（2/5, in volume ratio）, a preferential solvent for the PB block. The morphology of samples cast from solutions from different solvents and then stained by RuO4 was observed by TEM. Moreover, the tensile properties and deformation recovery behavior for these samples were measured and the results are explained according to the microstructures observed.
The effects of physical ageing on the crazing of polyphenylquinoxaline(PPQ E) films were studied. The DSC endothermic peak at the glass transition region of the samples was interpreted in terms of the cohesional entanglement theory. The free volume cavity size and free volume intensity of the samples were characterized by positron annihilation life spectroscopy. The difference in free volume cavity size and free volume intensity between two samples reflect the strength and density of cohensional entanglement point. The critical strain for craze initiation and craze stability depended on physical ageing of the samples. The relationships between physical ageing and crazing were interpreted initially.
The morphology of poly(styrene ethylene/butylene styrene)(SEBS) triblock copolymer cast from heptane and toluene was studied by combining atomic force microscopy(AFM) with transmission electronics microscopy(TEM). The quantitative agreement of the results of AFM and TEM plays a key role in determining the phase attribution for the AFM images. It is confirmed that under the moderate tapping condition, the hills in AFM height images correspond to the polystyrene phase and the valleys to the rubbery phase.
Atactic polystyrene ( a PS) films cast from solutions of different concentrations in dichloromethane under vacuum conditions were prepared.Their tensile mechanical behavior has been studied.It was found that the tensile strength of films cast in vacuum increases significantly with the solution concentration when the solution concentration is above 0.02?g/mL.The existence of a critical concentration value in the region of 0 01～0 02?g/mL is in agreement with the results of previous experiments.The critical concentration has been identified as c e for coil entanglement.
