Influence of the multi-functional epoxy monomers structure on the electro-optical properties and morphology of polymer-dispersed liquid crystal films

Polymer dispersed liquid crystal (PDLC) films were prepared by polymerization-induced phase separation method with nematic LC content as low as 40 wt%, and the electro-optical properties were carefully investigated. To accomplish this, the structure of multi-functional curable epoxy monomers with different composition feed ratios and the weight percentages of the two groups were examined in this study. The combined effects of heat-curable monomers’ structure on the conspicuous morphology of polymer network of PDLC films formed small holes and suitably distributed coin-like networks in both groups A and B, respectively. The detailed characteristics and morphology of polymer network of PDLC films were analyzed by employing liquid crystal device parameter tester, UV-Vis-NIR spectrophotometer and scanning electron microscope. Meanwhile, the enhanced curing temperature effects on the alkyl chain length, short flexible chain length, and rigid chain segment containing epoxy monomers structure on the increasing morphology of polymer network as well as electro-optical properties of PDLC films were also studied. It was found that the LC domain size of the polymer network could be regulated by adjusting the structure and composition ratio of curable epoxy monomers, and then the electro-optics of the PDLC films could be optimized, which is beneficial for decreasing the total LC content in PDLC devices.