Paramagnetic liquid-crystal side-chain polyacrylates containing Schiff base copper(II) complexes

Polymers containing Schiff base copper complexes were synthesized from thermotropic liquid-crystalline polyacrylates containing a mesogenic bidentate Schiff base as the side cain. The introduction of the copper atoms (5-65 mol%), gave rise to cross-linked polymeric chains, and the copper content of the polymers was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The liquid-crystal properties were examined by differential scanning calorimetry (DSC), polarizing microscopy and electron paramagnetic resonance (EPR) spectroscopy. The mesophases of the original polyacrylate are enantiotropic smectic A and smectic C, whereas polymers containing the bis(Schiff base)copper(II) complex in different proportions exhibit an enantiotropic smectic C mesophase. The EPR measurements of this type of copper-coordinated polymer at different temperatures indicate a restricted motion of the copper complex around the long molecular axis and provided information on the local order of the molecules in the liquid-crystal phase.