Dielectric relaxation and infrared studies of strongly sterically hindered alcohols in a polystyrene matrix

Abstract

Dielectric loss measurements have been made between 10 and 10⁵ Hz on eight strongly sterically hindered alcohols in a polystyrene matrix from 80 to 300 K. One alcohol has also been studied in glassy o-terphenyl and santovac. The infrared spectra of all the alcohols in polystyrene matrices at appropriate temperatures have also been obtained. In the plot of ε″vs. temperature at a fixed frequency two alcohols have each shown three well resolved dielectric absorption processes, whereas the remainder exhibit either two well separated peaks or the sign of two absorptions, except for one alcohol which gave only a single peak. All the alcohols except di-t-butyl carbinol exhibit dielectric absorption somewhere in the 200–270 K region. The infrared spectra of the corresponding alcohols helped in assigning the dielectric absorption obtained in the temperature range 200–270 K to the presence of polymerized H-bonded species (obtained for all the alcohols except one), with ΔH_E values of a similar order of magnitude. The dielectric absorption(s) obtained between 80 and 190 K in a polystyrene matrix are ascribed either to merged molecular/intramolecular processes or to the separated molecular and intramolecular processes. Comparisons are made of ΔH_E for the sterically hindered alcohols in a polystyrene matrix with those of sterically hindered alcohols in the pure liquid phase where the two sets of data are of a similar order of magnitude. The simplest interpretation of the absorption in the 200–270 K region is in terms of a dissociation process involving the breaking on average of about three H-bonds. However, it seems likely that this dissociation process alone cannot fully account for the absorption found relating to the presence of polymerized alcohol molecules.