| dc.description.abstract | Dielectric absorption studies of a variety of polar
solutes containing rotatable groups and of some analogous rigid
molecules dispersed in atactic polystyrene have been carried out.
Preparation of the solutions as solid disks, and the dielectric
measurements using a General Radio 1615-A capacitance bridge and
a Hewlett-Packard Q-meter with appropriate temperature-controllable
cells have been described. The experimental data as a function
of frequency at different temperatures were subjected to analysis
by a series of computer programmes written in the API language.
The activation energy barriers opposing the dielectric relaxation
processes were obtained by the application of the Eyring rate
equation.
Different types of polar rigid molecules have been
studied mainly to provide sources of relaxation data and activation
parameters for comparisons with those of flexible molecules of
analogous size. Attempts have also been made to correlate the
activation parameters with size, shape, and rotating volume of
the rigid molecules. Studies of some nitrogen-containing heterocyclic
rigid molecules and the comparison of their Eyring analysis
results with those of the analogous non-heterocycles showed no significant molecular interaction with the polymer matrix.
Of the flexible molecules, a wide variety of compounds
containing the carbonyl group have been studied. Intramolecular
processes involving the rotation of the polar carbonyl group with
one or more segments from the alkyl substituents have been observed
for phenyl alkyl (aryl-alkyl) and dialkyl ketones. Significantly
higher energy barriers to acetyl group rotation around the C — N
bond have been found in N-acetylimidazole in which the N atom
is involved in ring conjugation. However, this barrier appeared
to have been reduced considerably due to the effect of saturation
as in N-acetyl-4-piperidone... | |
