Polymer Stabilized Liquid Crystal Smart Window with Flexible Substrates Based on Low-Temperature Treatment of Polyamide Acid Technology.

Yang Zhang,Xiulan Yang,Xiaowen Hu,Dong Yuan,Weiping Yang,Wei Zhao,Pengrong Lv,Jialin He,Xiao Wang,Yi Zhang,Ming Li,Guofu Zhou,Changrui Wang

doi:10.3390/polym11111869

Abstract

Polymer stabilized liquid crystal (PSLC) devices can be used as smart privacy windows that switch between transparent and opaque states. The polyimide alignment layer of a PSLC device is usually obtained by the treatment of polyamide acid (PAA) with temperatures over 200 °C. This hinders the fabrication of PSLC devices on flexible substrates, which melt at these high temperatures. In this work, the fabrication of a PSLC alignment layer using a lower temperature that is compatible with most flexible substrates, is demonstrated. It was found that the treatment of PAA at 150 °C could generate the same alignment for liquid crystals. Based on this, a PSLC device was successfully fabricated on a flexible polyethylene terephthalate (PET) substrate, demonstrating excellent electro-optic performances.

Highlights

In modern buildings, windows can be seen everywhere
To ensure full evaporation of solvent in the Differential scanning calorimetry (DSC) sample, and DSC signal was not interfered by solvent evaporation, and the pre-treatment of polyamide acid (PAA) solution was conducted before DSC test
We performed long-term stability experiments on fabricated Polymer stabilized liquid crystal (PSLC) devices, including high temperature (Figure S3), high humidity (Figure S4), and switching tests (Figure S5). These results showed that the PSLC devices with low-temperature-treated PAA layers have a similar stability

Summary

Introduction

The current function of a window is relatively simple. A number of recent innovations about electrically switchable windows and flexible windows have provided new properties for windows, such as privacy windows, energy-saving windows, and smart windows [1–7]. Among various types of electrically switchable windows, liquid-crystal-based (LC) windows have attracted great attention due to their fast response, low cost, and simple structure [8–12]. The development of LC windows can be mainly categorized into polymer dispersed liquid crystals (PDLCs) and polymer stabilized liquid crystals (PSLCs) [13,14].

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Results

Conclusion