Thermal properties of polymer networks used in light control liquid crystal sheets for cars

Abstract

In this study, we investigated the thermal stability of polymer networks, which plays an important role in the function of polymer network-liquid crystal composite films. A glass transition temperature of the polymer network was found to be 87 °C. The thermal expansion coefficient of the polymer network was 1.05×10–4/K from room temperature to 120 °C, which resembled that of polyethylene terephthalate. The polymer network had 0.5-1.4 µm pore diameter where the liquid crystal continuous phase exists, and 52 % of the pores had the diameters of 0.9-1.0 µm. The heat treatment of the polymer network was performed at 40, 60, 80, and 100 °C for 1 h. The pore size of the polymer network was almost unchanged by heat treatment, indicating excellent thermal stability.