earticle

영어

Mechanochromism is a stress-induced color change of materials and motivates smart applications such as stress-sensing, material damage-reporting, and information security. The principles to give mechanochromism include mechanophore, aggregation-induced emission, and structural colors. Cholesteric liquid crystal (ChLC) exhibits a structural color based on its selective reflection of circularly polarized light (CPL). Several cellulose derivatives are capable of expressing ChLC and can be a key component to produce mechanochromic materials. We have recently found that polymerized composites of ChLC solution of ethyl cellulose in acrylic acid demonstrated not only wide-ranging color change but also circular dichroic inversion upon mechanical stimulus at >120°C. Their original color and circular dichroism were recovered by post-thermal treatment. For propionylated hydroxypropyl cellulose, ChLC structure could be immobilized with various monomers, to which the contribution of hydrogen bonding and moderate compatibility was confirmed spectroscopically [Polymer 2019]. The extension of applicable monomers led to wide-ranging control of temperature and stress for mechanochromism expression. Most recently, we have succeeded in elucidating the effect of birefringence to the inversion of CPL handedness and simulating the mechanochromism. Cellulose-based ChLC is thus a promising material for smart mechanochromic material design.