Some dielectric and spectroscopic studies on hydrogen bonding

Abstract

Dielectric relaxation studies were carried out principally on some hydroxy compounds (e.g., phenols) and some carboxylic acids in polystyrene (PS) matrices and, in some cases, in compressed solids (CS). The hydroxy compounds in PS showed at least one absorption each corresponding to the molecular relaxation. In CS and, in some cases, in PS, a second absorption process due to the O-H group relaxation was observed in some of these compounds. The relaxation parameters as well as the Eyring activation parameters for both the molecular relaxation and group relaxation were found to be significantly influenced by hydrogen bonding in several cases. In general, carboxylic acids showed two families of absorptions. The common absorption process observed for all the acid molecules was attributed to the 0-H group relaxation in cyclic acid dimers which has to be preceded by the breakage of hydrogen bonds in the cyclic structures. The other absorption process for a number of the acid molecules was attributed to the molecular relaxation and/or segmental motion. In case of ester molecules a common process due to O-R group reorientation was observed.