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-chain random liquid crystalline (LC) copolymers containing cyanobiphenyl mesogenic and acrylic acid (38 mol %) groups. Heat treatment of the LC copolymer at 130 °C for 5−200 h is accompanied by formation of intra- and intermolecular anhydrides and network structures causing an increase of the glass transition and clearing temperatures. The influence of annealing on the reorientational dynamics of the copolymers was investigated by broad-band dielectric relaxation spectroscopy. The local dynamics of the side group involving spacer motion (γ relaxation) and mesogen rotation about the long axis (β relaxation) do not depend on the annealing time. At the same time a considerable (more than 2 orders of magnitude) decrease in the relaxation rates of the cooperative δ and α processes was observed due to a gradual increase in the main-chain rigidity during the annealing. The molecular mechanism of all relaxation processes detected is discussed.