Abstract

Polymer dispersed liquid crystal (PDLC) films are heterogeneous composite materials consisting of micron-sized droplets of liquid crystal dispersed in a continuous polymer matrix. They are formed by a phase separation process of the LC component from the polymer. PDLC films can be switched from a light scattering off-state to a transparent on-state, when a sufficiently high electrical field is applied. Polymerization Induced Phase Separation (PIPS) using UV-light is one of the most common methods to prepare PDLC films and the polymerization is induced by decomposition of the photoinitiator in a mixture of LC with functional monomers.Polymer/liquid crystal (PDLC) films were prepared by a PIPS process of a mixture composed of the nematic LC material 4-cyano-4′-pentylbiphenyl (5CB), 2-hydroxyethylmethacrylate (HEMA) as monomer, and a photoinitiator (Darocur 1173). Ultraviolet (UV) radiation was employed to initiate the PIPS process. The electro-optical behaviour of the films obtained was investigated as function of applied voltage and frequency. Strong memory effects have been observed in the case of samples prepared from 60 weight.-% 5CB and 40 weight.-% HEMA.

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