NMR and DSC Observation of Thermotropic Nematic Liquid-Crystalline Polymer with Cyanobiphenyl Group in The Side Chain

Abstract

The proton NMR spectra and DSC thermograms were observed with raising temperature for side chain type thermotropic liquid-crystalline polymer, poly(6-(4′-cyanobiphenyl-4-yloxy) hexylacrylate (PCBA). A pronounced variation was found for the NMR spectra and DSC heating curve depending on the thermal history applied on PCBA before the measurements. In the case of gradual cooling from the isotropic state to the solid state, DSC heating curve showed endothermic peak at the glass transition temperature. The line widths was taken as the parameter characterizing the NMR spectra and their temperature dependence was discussed. A qualitative interpretation on the observed NMR spectra was given in relation to the orientation of mesogenic group. The obtained endothermic peak was considered to come from the change in orientational behavior caused by the gradual cooling to the solid state.

Key Words:

• liquid-crystalline polymer
• thermal properties
• DSC
• proton NMR