Comments on “some evidence against the existence of the liquid–liquid transition. III. The evaluation of the TLL event by differential scanning calorimetry”

Abstract

AbstractThe volatile‐component evaporation mechanism proposed by Chen et al. to explain molecular‐weight‐dependent endothermic peaks found at temperatures above Tg in anionically prepared polystyrenes (PSs) on first heating in open DSC pans is inconsistent with several bodies of literature data which were overlooked, including similar data with closed DSC pans. Moreover, this mechanism appears deficient in explaining details of the dependence of the endothermic peak temperature on M̄n both below and above the entanglement molecular weight Mc, with a sharp increase in slope at Mc. The original fusion–flow mechanism of Stadnicki et al. is compatible with all other known literature data including results on thermal PS and PMMA fractions. Hot‐stage microscope examination of powdered anionic PSs supports the Stadnicki mechanism from M̄n = 1900 to at least M̄n = 350,000. Addition of small amounts (ca. 1 wt %) of benzene or ethylbenzene to PS results in open‐pan DSC traces without endothermic peaks but with an endothermic slope change indicating gradual loss of diluent at decreasing rate as the temperature is increased from below Tg up through the TLL region.