Glass transition temperature of cyclic polystyrene and the linear counterpart contamination effect

We present here a systematic investigation on the glass transition temperature (T-g) for a series of highly purified cyclic polystyrene (c-PS) samples with molecular weight (MW) varying from 3300 to 13,400. Compared with their linear counterparts, c-PS samples show much higher T-g and exhibit weak Tg-MW dependence. By blending linear polystyrenes with c-PS, the linear polymer contamination effect on the T-g of c-PS was systematically investigated. It was found that the measured T-g of the mixtures increases with the decrease of linear polymer content and the relationship is consistent with Fox equation. These results are helpful to understand the origin of previously reported different T-g -MW relationship for c-PS.