Carbon-centered radical based dynamic covalent chemistry for stimuli-responsive chromic materials

As an essential smart material, stimuli-responsive chromic materials have received increasing research attention because of their visualization effects induced by external stimuli, including temperature, light, and mechanical stress. According to the types of stimuli, they can be categorized as thermochromic, photochromic, and mechanochromic materials, respectively. In recent studies, organic radical-based dynamic covalent chemistry (DCC) has demonstrated great potential to serve as a prototype for the preparation of stimuli-responsive chromic materials because the process is facilitated by simple radical-radical coupling reactions without the addition of catalysts or the generation of by-products and is usually accompanied by a distinct color change. This review aims to highlight carbon-centered radicals that can associate and dissociate reversibly with external stimuli and explore their potential as building blocks for the preparation of stimuli-responsive chromic materials.