From Thermochromic Phenomena in Polymers

Another way to obtain thermochromic polymers is to incorporate a thermochromic material into a polymer matrix. Both components build separate phases and do not influence the phase structure of the other component. Microencapsulated leuco dye-developer-solvent systems, inorganic pigments and conjugated polymers are suitable candidates for this purpose. Leuco dye-developer complexes are by far the most important systems to achieve thermochromic properties for different polymer materials by realising a separate phase of the thermochromic system in a non- thermochromic polymer matrix. With regard to their importance for the development of thermochromic materials the properties of these complexes are discussed in much more detail than those of inorganic thermochromic pigments or thermochromic conjugated polymers.

3.1 Leuco Dye-Developer-Solvent Systems

Leuco dye-developer-solvent systems consist of an electron- donating chromogenic compound (leuco dye), an electron acceptor (developer) and a matrix component (solvent) [1]. The most common electron-donating chromogenic compounds are phenylmethane and fluoran derivatives bearing a lactone ring moiety. In the lactone ring-closed state these so-called leuco dyes or colour formers [2] are either colourless or weakly yellow coloured. On reaction with an electron-accepting developer an opening of the lactone ring occurs resulting in the formation of a zwitterionic structure. As a result of this reaction the conjugated ?-electron system of the dye is extended and the longest wavelength absorption peak shifts from the UV to the visible range. Thus the dye becomes coloured. The addition of an appropriate solvent component enables the colour-forming reaction to be reversible with temperature. Leuco dye-developer-solvent systems are...

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Temperature Indicating Coatings and Materials
Temperature indicating paints and materials include labels, paints, crayons, or other markers that change color or shape when exposed to a certain temperature.  These products are typically non-reversible and are designed for one-time use.
Industrial pigments are finely ground powdery substances that are one of the basic components of paint or caulk.
Industrial Dyes
Industrial dyes are colorants consisting of single molecules that are able to absorb certain parts of the spectrum of visible light and reflect others.
Adhesive Tapes
Adhesive tapes are used to assemble materials or parts together using a sticky chemical bond. Adhesive tapes are made by coating a backing or carrier (paper, plastic film, cloth, foam or foil) with an adhesive on a web or roll coater.
Mounting Compounds
Mounting compounds are used to encapsulate specimens of a metal, ceramic, minerals, biomaterials or other material to allow grinding, polishing and other sample preparation for analysis using microscopes, hardness testers or spectrometers. Mounting compounds are in the form of compression mounting resins (powders, pellets or preforms) or liquid resins.

Topics of Interest

3.2 Inorganic Pigments In contrast to the thermochromic effect of organic composites, thermochromism of inorganic materials, such as metal salts and metal oxides, has been well known for a long time...

3.6 Applications Thermosensitive recording paper was launched onto the market by the National Cash Register Company in 1968. It consists of a paper sheet coated with a single thermosensitive layer...

Overview Chromogenic polymers change their visible optical properties in response to an external stimulus [1]. In terms of the specific stimulus they are subclassified as thermochromic (temperature),...

The intention of the project was to evaluate aesthetic and technical performance of thermochromic dyes in conjunction with integrated heating mechanisms. Thermochromic dyes change color with...

3.4 Comparison Between the Three Different Classes of Thermochromic Additives A comparison between the classes of thermochromic additives presented in Sections 3.1 3.3 is given in Table 3.2. The...