Anomalous electro-optical response of NCAP-type nematic/polymer dispersions

We have experimentally investigated the mechanism of switching a composite film consisted of a dispersion of micron-sized nematic droplets in a polyvinyl. alcohol matrix. Principal transmittances of the film and the phase shift between principal components were measured ellipsometrically as functions of applied electric field and incidence angle. It is found that in the region of low fields the transmission curves often exhibit a pronounces local minimum, while the phase shift curves have a local maximum. With increasing the incidence angle, the transmittance for light polarized in the incidence plane starts to oscillate, whereas the transmission curve for orthogonal component becomes monotone. The obtained results are discussed in terms of the phenomenological model which takes into account the non-uniform realignment of the local director in the bulk of nematic droplets and the surface orientation effects at LC/polymer interface.