DIPOLE-DIPOLE INTERACTIONS IN SIMPLE ESTERS AND IN LIQUID-CRYSTAL POLYESTERS

The C=O stretching frequencies of alkyl esters and polyesters are used as a probe to study the possible existence and the extent of dipole-dipole interactions between ester groups in these systems. The dynamics of a linear array of electric dipoles is worked out. The results account for the observed infra-red and Raman spectra of solid methyl acetate and ethyl acetate, but fail to account for the multiplet structure observed for one of the polyesters, which shows liquid-crystalline properties. Calculations show that the vibrational spectra are a good probe only of intermolecular interactions at short range.