Molecular Motions and Mechanical Relaxations of Poly(Carbonate) in the Glassy State

Abstract

In order to determine the characteristics of the glassy-state relaxations of poly(bisphenol-A carbonate) which are closely overlapping each other, shear relaxation modulus was measured from 10 sec to 900 sec at temperatures ranging from ca. -180°C to 0°C. Three relaxations named β, γ and δ in the order of descending temperature were observed separately and master curves were determined by the method of reduced variables. The activation energies of the β, γ and δ relaxations were estimated to be ca. 30, 25 and 9 kcal/mol, respectively. Theoretical considerations suggest that the molecular motions for the β, γ and δ relaxations are the local-mode motion of main chain, the flip motion of a phenylene with a carbonate group, and the rotational motion of a pair of methyl groups belonging to neighboring chains and coupled by van der Waals force.