Electrooptical properties and microstructure of polymer-dispersed liquid crystal doped with various reinforcing materials

Different types of reinforcing material, such as hydrophilic silica (Aerosil 200), (1-propylmethacrylate)-heptaisobutyl-substituted PSS (POSS-1), octavinyl-substituted PSS (POSS-8), octamethyl-substituted PSS (POSS-octa), and poly(dimethylsiloxane) (PDMS) were incorporated into a conventional polymer-dispersed liquid crystal (PDLC) system to enhance electrooptical properties by increasing phase separation, resulting from increasing the gel content and decreasing the viscosity of the mixture. The mixtures with POSS-1, POSS-octa, and Aerosil 200 show lower viscosity than the neat mixture, caused by the weak interaction of monomer molecules because of inserting these particles into the monomer chains, whereas the mixtures with POSS-8 and PDMS show an increase in viscosity. The PDLC film with POSS-1 represents the lowest off-transmittance value because the gel content is above 94% and the droplet size of the LC is optimal. However, when the gel content is decreased, the droplet size of the LC in the film becomes large because of unreactive monomer flowing into the LC, giving rise to the increase in off-transmittance value.