화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.367, 3055-3063, 2001
Evolution of electro-optical properties of polymer dispersed liquid crystal materials during processing
Polymer dispersed liquid crystal (PDLC) films are interesting materials particulary for optical devices. The initial mixture was composed of diglycidyl ether of bisphenol A (DGEBA), polypropylene oxide diamine (Jeffamine D-400), and the nematic low molecular weight liquid crystal E7. PDLC films were obtained by combined thermally and polymerization induced phase separation processes initiated by the temperature controlled polycondensation reaction of DGEBA and Jeffamine D-400. The electro-optical curves of the obtained films strongly depend on the monomer conversion. It was found that both the transmission in the off-state as well as in the on-state decrease with the extent of cure. In addition, threshold and saturation voltages increase for PDLC films characterized by higher monomer conversion values. The electro-optical curves obtained for a conversion of approximately 80% exhibit an unusual behavior. At monomer conversions approaching 100% the transmission versus voltage curves show the expected normal mode.