Abstract
Polymer-dispersed liquid crystals (PDLCs) were synthesized via the radical photopolymerization of isotropic mixtures comprising a cyanobiphenyl nematic liquid-crystalline mixture and monomers. The optical and switching properties of the PDLCs depended on the polymerization initiators and thiol monomers used. The polymerization initiators used were 1-hydroxycyclohexyl phenyl ketone (CPK) and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (PPO), while the thiol monomers used were 1,4 bis(3 mercaptobutyroyloxy)butane (B2), trimethylolpropane tris(3-mercaptobutylate) (T3), and pentaerythritol tetrakis(3 mercaptobutylate) (T4). The PDLCs prepared using PPO exhibited superior optical switching performance compared with those prepared using CPK. Particularly, the PDLCs fabricated with PPO and B2 exhibited a high initial haze value of 94.2 % at 0 V, which decreased to 11.0 % upon the application of an electric field of 100 V. The initial haze values of the PDLCs containing B2, T3, and T4 followed the order B2 > T3 > T4. At 100 V, the haze values of the PDLCs containing B2, T3, and T4 were nearly identical and in the range from 11.0 % to 12.6 %. These results indicate that the optical and switching properties of PDLCs are strongly influenced by small amounts of thiol monomers and the type of polymerization initiator used.
