Thermomechanical analysis of <i>T</i>_<i>g</i> and <i>T</i> &gt; <i>T</i>_<i>g</i> transitions in polystyrene

Abstract

Abstract Phenomenological softening points were measured on a series of 13 anionic, nearly monodisperse, atactic polystyrenes using a DuPont 943 thermomechanical analyzer (TMA) in a penetration mode. Although TMA cannot identify the nature of the “transition” observed as such, the results obtained support the evidence for the T g , T ll , and T ′ ll transition in polystyrene discussed in recent literature. T g and T ll were found to vary with molecular weight in a systematic manner, while T ′ ll could only be observed at very high molecular weight. The technique appears to be quite useful in offering rapid and reproducible information on the various transitions in the liquid state of polystyrene.