I am writing this report regarding your requested information about thermo-chromic material and how can be benefits to our company. Before I give description about above material I would like to thank you for giving me opportunity and give me enough time and source to search information about this new material. Thermochromism is the reversible change in the color of a compound when it is heated or cooled. Systematically investigated thermochromism was in 1971 at first time. The following 4 materials are used as thermochromism (1)Organic Compound (2) Inorganic Compound (3) Polymer (4) Sol-Gel 1. Organic compound thermochromism
Organic compound thermochromism occurred due to equilibrium between two molecular species, acid-base, keto-enol, lactim-lactam, or between stereoisomer or between crystal structures. This type of thermochromism has various applications for fiber optical science, photo storage instrument, optical sensor, and so on. We can divide three parts on the basis of materials (1) Variation in Crystal Structure (liquid crystal) (2) Stereoisomer (3) Molecular Rearrangement
Advantages of organic compound thermochromism are that color change takes place sharply and that there are many factors to control temperature easily. 2. Inorganic compound thermochromism
Many metals and inorganic compounds are known to exhibit thermochromic behavior either as solids or in solution. It has been suggested that such thermochromic behavior arises from one of the following mechanisms (1) phase transition (2) change in ligand geometry (3) equilibrium between different molecular structure (4) change in the number of solvent molecules in the coordination sphere Inorganic thermochromic systems have not enjoyed widespread textile application as the observed change in color often in solution or at high temperature. The majority of textile end-uses demand a reversible, solid (or encapsulated) system that is suitable for application by printing and that exhibits distinct color changes over a small temperature range. Inorganic systems have been predominately employed in heat-indicating paints and crayons that provide a warning of the development of heat spots. Transition metal systems and organometallic systems are used as inorganic thermochromism. 4. Polymer thermochromism
Polymer thermochromism arises from polymer planar-nonplanar conformation transition. Especially, polyacetylene famous for polymer thermochromic material, therefore it has been researched. Generally polyacetylene can be synthesized in solid state. Color change is happened to transform acetylene structure to butatriene structure Polymer thermochromism has one of the problems that phase change temperature is not accorded. Moreover, It’s difficult to show exact color because the materials, which are researched for polymer thermochromic material, are not so many. 5. Sol-gel thermochromism
Interactions between macromolecules fall into four categories: ionic, hydrophobic, van der waals and hydrogen bonding. Phase transitions in polymer gels provide a means of studying these interactions. Many gels will undergo reversible, discontinuous volumes changes in response to changes in, for example, temperature, gel composition or light irradiation. These transitions result from the competition between repulsive intermolecular forces, usually electrostatic in nature, that acts to expand the polymer network, and an attractive force that acts to shrink it. Volume transitions in gels have been observed that are driven by all of the above-mentioned forces except hydrogen bonding Recently, reversible thermochromism of pH-sensitive dyes embedded in hydrogels was reported by Seeboth et.al. The advantages of using hydrogels are biologically degradable, innocuous, free of organic solvent, inexpensive, available in large quantities and non-flammable. Furthermore, the hydrogels allows high transparency and transistion temperature at which color...