Three specimens from solution cast polyvinyl chloride (PVC) films

one being ice-water quenched from 120℃(Q)

one being slowly cooled from 120℃ (SC) and one being quenched and sub-Tg

annealed at 72℃ for 48h (AN)

have been studied by infrared difference spectra Q-SC and AN-Q and temperature difference spectra of T2-T1 for every 4℃ step on heating to 120℃ at 2℃/min. SC and AN showed more trans conformers than Q. It means that the PVC chain has more gauche conformers at higher temperatures and some of these are frozen during quenching through Tg The temperature difference spectra on heating through Tg showed that the conformation changes in Q are gradual while a rather abrupt change occurs in AN at 92-88℃。A kind of chain entanglement mechanism is suggested which hinders the molecular conformation changes in AN below Tg until a sudden release occurs at Tg.