Rayleighhyphen;Brillouin lighthyphen;scattering studies on atactic polystrene

摘要

Rayleighhyphen;Brillouin lighthyphen;scattering studies have been carried out on atactic polystyrene thermally polmerized under vacuum from scrupulously clean styrene monomer. The ratio of the central Rayleigh intensityIRto the total Brillouin intensity 2IBappears to be a function ofTminus;1. Depolarization intensities have also been measured and, in particular, we find that rgr;H=1 for this polymeric glass. Theoretical predictions forIR/2IBare discussed in light of these results. We conclude that local isotropy due to strain fields frozen into glass is negligible or in low concentration. Annealing studies confirm this result which is in disagreement with our previous results for poly(butyl) methacrylate. In addition, we find that the change in slope of the Brillouin frequency shift ohgr; versus absolute temperatureTdefines aTg10ndash;12 K below that measured by DSC and that ohgr; (glass) increases with decreasing molecular weight, in agreement with previous results. A study of the relaxation of a few degrees belowTgfor periods of a month and more does not shiftTg(from ohgr; vsT) to lower temperatures for these highhyphen;molecularhyphen;weight polystyrene samples.