Polymer surface-induced order of liquid crystalline molecular alignment based on nematic-isotropic phase transition behavior

Alignment order of liquid crystal (LC) molecules at the (polymer/LC) interface was evaluated by comparing nematic-isotropic phase transition temperatures (T_NI) at the interface with T_NI in the bulk. The thickness dependence of T_NI was measured using the LC cell in which an LC thin layer was sandwiched between polymer surfaces without surface treatment. The order of LC molecular alignment at the (polymer/LC) interface increased with surface free energy of the polymer substrate. The surface of crystalline polymer provided higher order of LC molecular alignment. Hydrophobic intermolecular interactions at the (polymer/LC) interface may be more responsible for increase in the interfacial molecular alignment order of LC in comparison with the hydrophilic one.