Influence of polymerisation parameters on the electro-optical properties of polymer-stabilised liquid crystals for smart glass application

Abstract

ABSTRACT Smart windows are an important application of liquid crystal/polymer nanocomposites. Recently, an original design has been proposed for a window that switches from a scattering to a transparent state under an electric field. By polymerisation, the topological defects of the smectic A phase under hybrid anchoring conditions are stabilised in the nematic phase, making them addressable by the field. Here, we report the impact of the polymerisation parameters on the electro-optical properties and microstructure of the nanocomposites. We have first estimated the polymerisation kinetics and then investigated the influence of the UV-light intensity, monomer concentration, and photoinitiator concentration. UV-light intensity has little effect on the electro-optical properties of the device, although microstructural changes were observed. The monomer concentration has a strong impact on the scattering power in both the on- and off-states. A model is proposed to describe the dependence of the response times on the monomer concentration. Finally, no influence of the photoinitiator concentration on the electro-optical properties was observed. Polymerisation could occur even in the absence of photoinitiator, possibly due to the presence of impurities that could generate radicals under irradiation. Our study should help optimising the formulation of polymer-stabilised liquid crystal nanocomposites for industrial applications.