Effect of hydrogen bonds on the order parameter and elastic constants of comb-shaped liquid-crystalline copolymers

Comb-shaped LC copolymers containing phenylbenzoate mesogenic groups and fu nctional carboxyl groups, the derivatives of alkyloxybenzoic acid, with a v ariable number n of methylene groups in a spacer (n = 3, 6, and 9) were syn thesized. The effect of hydrogen bonds on the phase state and properties of LC polymers was examined. It was established that an increase in the lengt h of a flexible fragment in the functional monomer unit (n = 6 and 9) assis ts formation of intermolecular hydrogen bonds; for a short spacer (n = 3), intramolecular hydrogen bonds are predominantly formed. The appearance of i ntra- and intermolecular hydrogen bonds affects the values and the temperat ure dependences of birefringence, the order parameter, and the orientationa l elastic constants of the LC copolymers under study.