Ultrathin, transparent, thermally-insulated, and energy-efficient flexible window using coatable chiral-nematic liquid crystal polymer

Transparent windows that insulate infrared (IR) light entering indoor spaces promise to reduce energy consumption. However, a long-standing challenge for an energy-efficient window is achieving compactness and flexibility simultaneously. In this paper, we report the fabrication of a transparent, flexible, ultrathin, and thermally-insulated IR reflector using a coatable chiral-nematic liquid crystal polymer and polyvinyl alcohol (PVA) as an alignment layer. PVA is transparent, biocompatible, thermostable, noncorrosive, and cost-effective. The fabricated IR reflector shows high optical transparency (∼91%) and low haze (≈9.8%) values in the visible spectrum of light. Moreover, it significantly reduces greenhouse gas emissions by preventing energy consumption for cooling systems and lighting in indoor spaces; specifically, it reduces electricity consumption in indoor spaces for lighting and cooling systems under hot weather conditions. To demonstrate the mechanical stability of the fabricated reflector, many mechanical, flexibility, and bending stability tests were conducted. The results show that our proposed IR reflector is a potential candidate for designing desirable shapes for many applications, such as anti-IR devices and energy-efficient windows, for achieving significant environmental and economic benefits.