Two calorimetrically distinct parts of the dynamic glass transition

Fachbereich Physik, Universität Halle - D-06099 Halle (Saale), Germany

Received: 3 July 1998
Accepted: 11 September 1998

Abstract

Although known for more than thirty years, the physical nature of the glass-transition crossover region is still an open question. Heat capacity spectroscopy experiments in the crossover region of poly(n-hexyl methacrylate) are presented which indicate, for the first time, that the dynamic glass transition consists of two separate parts in series: A thermorheologically rather simple high-temperature part (called a-process) and a low-temperature part with increasing molecular cooperativity on the nanometer scale (-process). The calorimetric experiments show, surprisingly, a decline of the a process and a separate onset of the α-process.