Relaxation processes of some long chain aliphatic aldehydes

The dielectric absorption of seven aliphatic straight chain aldehydes has been examined in a polystyrene matrix between 80 and 325 K and in the 50 to 10⁵ Hz region. For each solute two sets of absorption curves were found, one around 100 K and the other in approximately the 200 – 300 K region. The relaxation data for the 100 K region has been identified with segmental rotation and probably, with rotation about the C  CHO bond as well. The higher temperature process, which involves relaxation of appreciably larger units, may well be an overlap of molecular and larger segmental rotation. n-Nonanal was examined in a polystyrene and a polypropylene matrix and in both cases gave low and high temperaure absorption curves. The parameters for the former were almost independent of the medium whereas those for the latter process exhibited considerable variation.