Molecular Crystals and Liquid Crystals, Vol.500, 10-22, 2009
High Contrast Reverse Mode PDLC Films: A Morphologic and Electro-Optical Analysis
Reverse Mode Polymer Dispersed Liquid Crystal films obtained by the photo polymerization of homeotropically aligned Liquid crystal solutions, have been investigated in order to optimise their optical contrast with the aim of their application as windows able to be switched from an high transparent state into a very opaque state by an appropriate electric field. An excellent optical contrast has been obtained by varying the amounts of two different liquid crystal diacrylate monomers in the starting solutions as precursors of the final polymer matrix. Morphology of the film has been investigated to account for the electric threshold field needed to operate the film. A simple model has been proposed to describe the threshold field and the behaviours of the dynamic response times as a function of the polymer composition. A novel type of morphology which opens the field for deeper investigation, has been found, where two different segregations of the liquid crystal into the polymer matrix coexist.