The synthesis and thermal properties of polyepichlorohydrin side-chain liquid crystal polymers

The synthesis and characterization of a new series of side-chain liquid crystal polyepichlorohydrin (PECH) polymers are described. The structures and thermal properties of the synthesized polymers were investigated using IR, NMR, polarized optical microscopy and differential scanning calorimetry. A substantial increase of the glass transition temperature with the degree of substitution of side-chain groups was observed. Polymers with a degree of substitution of side groups, of at least 60%, exhibited thermotropic liquid crystalline behaviour. The polymers present thermal liquid crystalline behaviour and form Schlieren and thread texture upon cooling from the isotropic phase, after annealing for 120 min at different temperatures. In addition, the thermal decomposition of PECHOPhPhCN was studied by thermogravimetry under both nitrogen and air environments. The temperature of the maximum decomposition rate was about 340 °C. Weight loss decreased considerably after 350 °C and was approximately 98% at 700 °C. Chemical modification of functional polymers offers a simple method for obtaining liquid crystalline polymers whose transition temperature can be tailored by varying the amount of substitution, however complete substitution cannot be achieved.