Dielectric and IR spectroscopy of the macromolecular reaction of anhydridization in a functionalized side-chain liquid crystalline copolymer containing acrylic acid groups

The anhydrization reaction has been investigated in functionalized side-cha in random liquid crystalline (LC) copolymers containing cyanobiphenyl mesog enic and acrylic acid (38 mol %) groups. Heat treatment of the LC copolymer at 130 degreesC for 5-200 h is accompanied by formation of intra- and inte rmolecular anhydrides and network structures causing an increase of the gla ss transition and clearing temperatures. The influence of annealing on the reorientational dynamics of the copolymers was investigated by broad-band d ielectric relaxation spectroscopy. The local dynamics of the side group inv olving spacer motion (gamma relaxation) and mesogen rotation about the long axis (beta relaxation) do not depend on the annealing time. At the same ti me a considerable (more than 2 orders of magnitude) decrease in the relaxat ion rates of the cooperative delta and alpha processes was observed due to a gradual increase in the main-chain rigidity during the annealing. The mol ecular mechanism of all relaxation processes detected is discussed.