High-Performance Reverse-Mode Liquid Crystal Smart Windows via Co-Optimization of a Phosphate Self-Assembled Interface, a Polyurethane Acrylate Polymer Network, and a Patterned Microstructure

Abstract Reverse-mode polymer-stabilized liquid crystal (RPSLC) smart windows exhibit voltage off transparency and voltage on scattering, which are well aligned with the requirements of daylighting and solar heat insulation in buildings. These characteristics make RPSLC smart windows promising energy-saving light-modulating devices for building applications. Existing RPSLC devices suffer from uneven interfacial alignment, the mutual restriction between electro-optical properties, and poor cyclic stability. To address these problems, this work carries out an integrated collaborative optimization from three dimensions of interface, polymer components, and microstructure. A self-assembled monolayer (SAM) is constructed using a mixed system of octadecyl phosphate and bis(2-(methacryloyloxy)ethyl) phosphate. The resulting SAM enables uniform vertical alignment of the liquid crystals and strengthens interfacial coupling stability through chemical bonding. Flexible polyurethane acrylate is then introduced to optimize the internal polymer network structure and alleviate the trade-off in the electro-optical performance of the devices. In addition, a two-step exposure method is used to construct periodic polymer-wall microstructures and enhance the electro-optical properties and cyclic stability of the devices. The experimental results show that the saturation voltage of the prepared reverse-mode polymer-wall stabilized liquid crystal smart windows is only 7.2 V, the contrast ratio can reach 178, and they simultaneously possess excellent long-term cyclic stability. This strategy provides useful guidance for the design of RPSLC smart windows with improved electro-optical performance and cyclic stability for building-related applications.