Influence of the Metal Cross-Linking on the Dielectric, Mechanical, and Thermal Properties of a Liquid Crystalline Polyazomethine

Cross-linked polymeric materials have been synthesized by copper(II) complexation of a semiflexible main-chain liquid crystalline polyazomethine. The influence of the copper(II) cross-linking density on the thermal properties has been studied by DSC. The relaxation behavior of both the parent polymer and the complexed polymers has been investigated by dielectric spectroscopy and dynamic mechanical measurements. The parent compound exhibits three relaxations (denoted by α, β, and γ), together with a conductive process at low frequency. The relaxations have been associated with the glass transition (α), rotational motions located in the rigid mesogenic core (β), and local motions of the decamethylene flexible spacer (γ). Semiempirical calculations have been carried out in order to evaluate the rotational energy barriers which can account for the β process. The influence of the degree of cross-linking on the activation energies and on the strength and shape parameters has also been studied in the copper(II)-complexed polymers.