The relaxation processes of several long-chain aliphatic ketones and amines in glassy media

Abstract

The dielectric absorption of 2-alkanones (CH 3(CH 2) n COCH 3) (where n = 4, 5, 6, 7, 8, 10, 12, 14 and 16) and 1-aminoalkanes (CH 3(CH 2) n NH 2) (where n = 2, 3, 5, 7, 8, 9, 10 and 11) has been studied in a polystyrene matrix between 80 and 300 K in the frequency range 10–10 5 Hz. 2-alkanone with n = 8 has also been examined in polyphenylether, glassy o-terphenyl and a polypropylene matrix. For both series two sets of absorption peaks were obtained, one around 80–150 K and the other in approximately the 170–300 K region. The lower-temperature absorption can be accounted for by a model involving segmental motion about the CC bonds with consequent displacement of the polar end group. The enthalpy of activation for this intramolecular motion is independent of whether the polar end group is -CH 2Br, -COCH 3, or -CH 2NH 2. The higher-temperature absorption may be ascribed to a molecular relaxation process.