Preparation and characterization of polymer-dispersed liquid crystal films using poly(bornyl methacrylate)

Chiral (+)-bornyl methacrylate and achiral (±)-bornyl methacrylate were synthesized from (+)-camphor and (±)-camphor, respectively. To investigate the influence of the steric environment of the chiral polymers on the electro-optical characteristics of polymer-dispersed liquid crystal (PDLC) films, a commercially available positive nematic liquid crystal E7 was dispersed in the chiral and achiral polymer matrices. The electro-optical characteristics and the microstructures of the PDLC films with chiral and achiral racemized polymers were investigated. It was found that PDLC films with chiral polymers have relatively high contrast ratio and fast falling speed, but there exists a transient damping response when a square pulse of 20 ms and 60 V is applied. Two distinct morphologies were observed: (1) a `continual channel' with the chiral polymer matrix, and (2) an `isolated ball' with the achiral racemized polymer matrix. The reversible turbid and transparent changes with an applied a.c. electric field were also investigated.