Relationship between optical properties and polymerization initiators used in PDLC preparation

Polymer dispersed liquid crystals (PDLCs), which consist of a polymer network and liquid crystal material, are used in building materials and automotive windows (so-called smart windows, light-controlling liquid crystal devices, etc.). PDLCs have been researched to improve their optical properties and electric field response. In general, PDLCs are prepared by phase separation method via photopolymerization. In this study, the effects of polymerization initiators for the haze value were investigated. An alkylphenone (1-hydroxycyclohexyl-phenyl ketone (I-1)) and two types of acylphosphine oxides (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (I-2) and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (I-3)) were used as the initiators. I-3 increased the haze value in the initial state (0 V) and decreased the haze value when an electric field was applied. The combination of I-3 and a thiol cross-linking agent further reduced the haze value under the electric field.