α and β relaxation dynamics of a fragile plastic crystal

We present a thorough dielectric investigation of the relaxation dynamics of plastic crystalline Freon112, which exhibits freezing of the orientational degrees of freedom into a glassy crystal below 90 K . Among other plastic crystals, Freon112 stands out by being relatively fragile within Angell's [ Relaxations in Complex Systems , edited by K. L. Ngai and G. B. Wright ( NRL , Washington, DC , 1985 ), p. 3 ] classification scheme and by showing an unusually strong β relaxation. Comparing the results to those on Freon112a, having only a single molecular conformation, points to the importance of the presence of two molecular conformations in Freon112 for the explanation of its unusual properties.