Surface anchoring polymer glass transition and polymer-dispersed liquid crystal electro-optics

摘要

Abstract: We studied the electro-optic properties as a function of temperature of a PDLC film composed of either E7 or E43 dispersed as droplets in a polyvinylformal (PVFM) matrix. The dissolved liquid crystal lowers the glass transition temperature, T$-g$/, of the PVFM matrix to about 30 - 35$DGR@C. The electro-optics of these PDLC films change abruptly at the polymer matrix T$-g$/. In general the drive voltage decreases and the turn off time increases rapidly as the temperature is raised above T$-g$/. Also, the shutter has essentially no hysteresis below, and significant hysteresis above T$-g$/. These temperature effects are completely reversible. The rapid change in electro-optic properties cannot be entirely explained by changes in the polymer dielectric properties or droplet size and shape. We have therefore postulated that changes in the surface anchoring energy of the liquid crystal are primarily responsible for the abrupt changes in the electro-optic response at the matrix T$-g$/. !5