The Impact of Curing Temperature and UV Light Intensity on the Performance of Polymer-Dispersed Liquid Crystal Devices Exhibiting a Permanent Memory Effect

Abstract

PDLC films, synthesized via polymerization-induced phase separation (PIPS) utilizing both temperature and UV monochromatic radiation, were derived from a blend of E7 nematic liquid crystal (LC) and PolyEGDMA875 (polyethyleneglycoldimethacrylate) oligomers, serving as the precursor for the polymeric matrix. The influence of the curing temperature on thermal polymerization, UV light intensity on photochemical polymerization, and exposure time during these processes on the electro-optical characteristics of PDLC films was thoroughly examined. Observations revealed that employing thermal polymerization during device preparation notably enhanced the permanent memory effect of the PDLC films. Sustained high transparency (TOFF = 45%) over an extended duration at room temperature, even subsequent to voltage cessation, was achieved. This transition initiated from an opaque state (T0 = 0%) through to a transparent state (TMAX = 65%), resulting in a substantial 70% permanent memory effect.

Keywords

• polymer-dispersed liquid crystal (PDLC)
• liquid crystal
• permanent memory effect
• photochemical polymerization
• thermal polymerization