Two calorimetrically distinct parts of the dynamic glass transition
Fachbereich Physik, Universität Halle - D-06099 Halle (Saale), Germany
Accepted: 11 September 1998
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.
PACS: 64.70.Pf – Glass transitions / 05.40.+j – Fluctuation phenomena, random processes, and Brownian motion / 07.20.Fw – Calorimetry
© EDP Sciences, 1998