Infrared spectroscopic study of a phenyl benzoate side group—methacrylate main chain polymeric liquid crystal

Abstract

The temperature dependence of the infrared dichroism of a side chain polymeric liquid crystal was investigated for two homogeneously oriented samples, one aligned with a PVA coating and the other aligned by a magnetic field. From the apparent order parameters, it was found that the rotation of the mesogenic side group was restricted. Not only the rigid part of the side group, but also the alkyl chains were found to be partly ordered. Realignment of the side groups was observed in the case of the magnetically aligned sample at the smectic-nematic transition temperature. Unlike the other absorption bands, the C˭O bond vibration band shifted to higher wavenumbers with increasing temperature. This behaviour was explained by the influence of the neighbouring mesogenic groups on the conjugation existing between the π-electron cloud of the benzene rings and the π-electrons of the C˭O bond.