Green Thermochromic Materials: A Brief Review

Abstract

common thermochromic systems studied are leuco dyes and pigments, liquid crystalline polymers, and transition metal inorganic complexes. [2,15,[16][17][18][19][20][21][22][23] However, finished thermochromic materials commonly consist of or are incorporated into media that are or contain toxic, hazardous, or nondegradable components. [8,15,24] This limits their usage in applications that can pose the risk of cytotoxicity to the human body, such as food packaging or body temperature sensing devices for infants. Further, such hazardous and nondegradable materials exhibit high levels of persistence in soil as well as water systems and can pollute and disrupt these critical ecological systems. [24][25][26] "Green" thermochromic materials is a new and emerging field of research. Breakthroughs in this field will seek to replace toxic or inorganic materials which dominate the current thermochromic literature and applications with newly developed greener ones. Being a field in its infancy, there has yet to be a body of work that accumulates the current state of research in this field. This brief review seeks to explore and identify the constituent requirements for green materials as well as equip researchers to design thermochromic systems utilizing green chemistry. The history of thermochromism is reviewed in this paper. The mechanisms of thermochromism in common solids, liquids, and mesophases are considered as well as how the mechanistic pathway translates into their current applications. A general distinction between reversible and irreversible thermochromism is also discussed. Recent advances in the emerging field of green thermochromic materials are discussed critically and future applications mentioned.

Multiscale photoacoustic tomography using reversibly switchable thermochromics

“…We envision that thermochromic materials can be further engineered to satisfy fine-tuned temperature transition for different life science applications. For example, we can choose Leuco dyes to achieve color-to-colorless transition in thermochromic microcapsules 30 . The transition temperature of RSTMs can be fine-tuned by altering the crystallization/melting temperature of the dispersion solvent, as the crystallization and melting temperatures of the solvent determine the temperature in which the color transformation happens.…”

“…In comparison, thermochromic materials undergo color transitions during heating and cooling cycles within a specific temperature range by different mechanisms 27 – 32 Inorganic thermochromic compounds change their colors by phase-dependent crystal structure change of the entity, exhibiting thermochromic behavior at temperatures ranging from 70°C to 500°C. By contrast, the molecular structure variations and interconversion of stereoisomeric forms are responsible for the color changes of organic and polymeric thermochromic materials, showing mild and tunable color-changing temperatures.…”

4D Printing: Technology Overview and Smart Materials Utilized

“…These materials are typically made of inorganic or organic compounds that exhibit a reversible change in color or opacity when the temperature changes. The color change is typically caused by a change in the crystal structure of the material or the movement of ions within the material (Hakami et al, 2022;Crosby and Netravali, 2022).…”

Preparation of novel authentication film by screen printing of anthocyanin biomolecular extract: Thermochromism and vapochromism

“…A simple method of authentication is the use of thermochromic designs to be monitored by increasing temperature. Protecting contents on the surface of documents with thermochromic materials is a simple, efficient and reliable authentication method [18]. The thermochromic compounds can be used as security agents to prevent the manipulation of vital information since they are destroyed when peeled off or scraped.…”