Green Thermochromic Materials: A Brief Review

Green thermochromic materials are of great interest in many applications. Thermochromic and phase change materials are commonly used as smart devices to facilitate temperature sensing and passive heating/cooling systems, respectively. Since most of the current thermochromic materials are nondegradable, toxic, and/or nongreen, there is great opportunity to develop greener materials with high performance considering the wide range of materials that can exhibit thermochromism. This concise review distinguishes the different forms, phases, and chemical structures of thermochromic materials. A brief history of thermochromism is reviewed and a general distinction between reversible and irreversible thermochromism is provided. A general definition of green materials is provided, recent advances in the emerging field are critically discussed as well as future applications. This review also provides brief but thorough understanding of mechanistic pathways of this phenomenon in materials and the constituent requirements of green materials such that new systems can be designed using nontoxic, biobased, and/or biodegradable materials. Such green thermochromic materials will expand their use significantly.