title: Origin of two maxima in specific heat in enthalpy relaxation under thermal history composed of cooling, annealing, and heating.
abstract: The origin of two maxima in specific heat observed at the higher and the lower temperatures in the glass-transition region in the heating process has been studied for polymethyl methacrylate and polyvinyl chloride using differential scanning calorimetry, and the calculation was done using the phenomenological model equation under a thermal history of the typical annealing experiment composed of cooling, annealing, and heating. The higher maximum is observed above the glass-transition temperature, and it remains almost unchanged independent of annealing time t_{a}, while the lower one is observed above an annealing temperature T_{a} and shifts toward the higher one, increasing its magnitude with t_{a}. The analysis by the phenomenological model equation proposed in order to interpret the memory effect in the glassy state clarifies that under a typical annealing history, two maxima in specific heat essentially appear. The shift of the lower maximum toward higher temperatures from above T_{a} is caused by an increase in the amount of relaxation during annealing with t_{a}. The annealing temperature and the amount of relaxation during annealing play a major role in the determination of the number of maxima in the specific heat.
authors.affiliation: Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Waki
authors.initials: W
authors.lastname: Sakatsuji
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Konishi
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Miyamoto