Effects of prepolymer structure in holographic polymer dispersed liquid crystal

Abstract

Three different types of polyols—poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and poly(tetramethylene glycol)—with different molecular weights (Mn) were incorporated into the prepolymer structure, and the effects were examined with regard to the morphology and performance of holographic polymer dispersed liquid crystal. Among them, PEG showing the lowest glass transition temperature (Tg) exhibited the lowest threshold voltage (Vth), lowest operating voltage (Vop), and lowest diffraction efficiency with slow grating formation owing to its high viscosity of prepolymer mixture. The Tg decreased with increasing Mn because of the decreased crosslink density and hydrogen bonding, which reduced the anchoring strength, Vth and Vop. PPG400 gave Vth and Vop of approximately 7 and 24 V, respectively, with a contrast ratio of approximately 12. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Light‐directed mesoscale phase separation via holographic polymerization

“…Hyperbranched polymers have been incorporated into HPDLC recipes to modify initial viscosity, which not only increased the DEs and moderately decrease switching voltages, but also switching response times. Substituting fluorine atoms in the acrylate monomers, 122 and increasing the molecular weight between crosslinking sites 123 have shown similar morphological effects to decrease the switching voltage of HPDLC, while simultaneously increasing the DE of the gratings.…”