Preparation and property optimization of bistable electrochromic microcapsules

Abstract

In the improvement of stability and lifetime of bistable electrochromic (EC) materials, the microcapsule technique was used to protect the EC materials in a polymer shell, which was named bistable EC microcapsules (BEC-Ms). However, the particle size and shell thickness of microcapsules will affect their properties, such as response time, coloration efficiency, and bistable property. In this study, BEC-Ms was prepared via solvent evaporation method filled with PMMA as the shell and the mixture of crystal violet lactone (CVL), tetrabutylammonium perchlorate (TBAP), and phase change material (PCM) as the core. The particle size and shell thickness of microcapsules were adjusted and systematically investigated by controlling the emulsification rate and mass ratio of polymer shell to core. The optimized BEC-Ms with 2 μm size and 22.94 nm thickness showed excellent performance including fast response time (about 1 s), far lower than the safety of human body drive voltage (2 V), coloration efficiency (932 cm2 C−1), and good bistability (216 h). This approach provides a viable and alternative to flexible energy-efficient wearable display-related devices and smart textiles.