Liquid crystal and polymer dispersions: morphological control

Liquid crystal and polymer dispersions (LCPD) have potential application as flat panel displays, switchable lenses, optical switches, Bragg gratings, photonic crystals, diffractive optics, hyper-spectral filters, and etc. Precise morphological control of the phase-separated morphology of LCPDs is required to meet the rigorous requirements for the numerous applications. Liquid crystal and polymer dispersions (LCPDs) are micro or nano-structured materials fabricated using one of several phase separation techniques. The micro- or nano-structured morphology of LCPDs ranges from a polymeric network suspended in a liquid crystal solvent (polymer stabilized liquid crystals [PSLC] to random or spatially periodic micron or sub-micron sized liquid crystal droplet dispersions in a solid polymer matrix of polymer dispersed liquid crystals (PDLC) and the holographically formed PDLC (H-PDLC). The goal of this investigation is to identify the material properties and processing conditions required for more precise control of the phase-separated morphology of PDLCs. The investigation entailed construction of thermal phase diagrams for liquid crystal and monomer/pre-polymer mixtures to identify the compositionally dependent phase separation temperatures. The investigation also entailed inducing phase separation of the mixtures via ultra-violent light initiated polymerization at carefully chosen cure temperatures based on the thermal phase diagrams. The phase-separated morphology was correlated with the cure temperature, liquid crystal component, and mixture composition.