Thermochromism thermochromic materials, applications

Typically the chromophores used are pH sensitive, i.e. acidochromic or ionochromic (see section 1.4), and the medium is one whose pH varies with temperature. A variety of pH sensitive chromophores are known that are readily synthesised and can be modified to provide a wide range of shades. Application of these pH sensitive dyes in pressure and thermally sensitive papers for digital printing, e.g. fax papers, where the whole object is for the process to be irreversible, will be covered under ionochromism. The main area of application for reversible indirect thermochromic materials is as thermochromic organic pigments, as will be described below (section 1.3.4.1). 

Bernard Mark Heron was born in Workington, England in 1965. After graduation (GRSC) from Lancashire Polytechnic (Preston) in 1987 and a brief period in industry he obtained his PhD (CNAA) in Benzothiopyran Chemistry in 1992 under the supervision of Professor John Hepworth at the University of Central Lancashire. A postdoctoral fellowship in heterocyclic chemistry (1992-95) and an industrially funded lectureship at Central Lancashire (1995-98) were followed by appointment to a James Robinson Lectureship at the University of Hull (1998-2000). Dr. Heron was appointed as a senior lecturer (2000-present) in the Department of Colour and Polymer Chemistry at the University of Leeds. His research interests include the chemistry and applications of heterocyclic compounds, color chemistry, and organic photo- and thermochromic materials. 

The second volume of this new treatise is focused on the physicochemical properties and photochromic behavior of the best known systems. We have included chapters on the most appropriate physicochemical methods by which photochromic substances can be studied (spectrokinetic studies on photostationary states, Raman spectroscopy, electron paramagnetic resonance, chemical computations and molecular modeling, and X-ray diffraction analysis). In addition, special topics such as interactions between photochromic compounds and polymer matrices, photodegradation mechanisms, and potential biological applications have been treated. A final chapter on thermochromic materials is included to emphasize the chemical similarities between photochromic and thermochromic materials. In general, the literature cited within the chapters covers publications through 1995. However, in several cases, publications from as late as 1997 are included. 

Commercial and consumer applications of thermochromic materials [all sites accessed July 2011] ... 

Major Applications Antireflective coatings, " thermochromic materials," photoresists, electrorhe-ological materials, " film patterning, " recording materials, " lithium battery, semiconductors, printing materials, " inks, " corrosion inhibitors, " adhesives,"" drugs," detecting viable cells,"" treatment of Alzheimer s disease ... 

Major Applications Thermochromic materials, cosmetics, measurement of hydrophobicity of therapeutic drugs ... 

A huge number of other applications exist, where the chemical and physical requirements are totally different. These applications include reflectors, temperature measurement with thermochromic materials, nonlinear optics, polymer materials, SAMs (self-assembled mono-layers) and LB (Langmuir-Blodgett) Aims, the use of liquid crystals in template synthesis of porous materials, drug delivery, and many more. 

The potential applications of thermochromic material include temperature tim-able light and heat radiation filters, large area displays, and temperature indicators visualizing the temperature of the surrounding medium or the temperature profile of a surface which is coated with the thermochromic material. 

Industrial Applications Liquid crystal displays fuel cells photovoltaic cells solar cells photochro-mic materials sensors thermochromic materials detergents wood ... 

Polythiophene [78] is a promising material for certain future electronic applications, due to its relatively high stability and processability in the substituted form [79-81]. Upon substitution, with e.g. alkyl side-chains [79, 80], polythiophene exhibit properties such as solvalochromism [82] and thermochromism [83]. Presently, a large variety of substituted polythiophenes with various band gaps exists (for example see Ref. [81 ]). 

In the thermochromic liquid crystal (TLC) the dominant reflected wavelength is temperature-dependent and it has been employed for full-field mapping of temperature fields for over three decades. Although it is non-intrusive and cost effective, there are some problems in applying it to micro-scale measurements, because of size (typically tens of micrometers) and time response (from a few milliseconds to several hundred milliseconds depending on the material and the form). Examples of application are micro-fabricated systems (Chaudhari et al. 1998 Liu et al. 2002) and electronic components (Azar et al. 1991). 

An interesting material with both electro- and thermochromism behavior, Lix V02 was evaluated for a "smart window" application (25). Films of Li V02 were prepared by reactive sputtering and annealing an electrolyte of LiQ04 and propylene carbonate. 

In addition, the optical properties of these materials, which include luminescence and thermochromism, are promising for optoelectronic applications, specifically the TCNQ species as a candidate for new semiconducting materials in view of the clear scanning electron microscope (SEM) image observed for crystals of this product.173... 

This survey of organic photochromic and thermochromic compounds focuses on the main families that are involved in existing commercial applications, such as variable optical transmission materials (ophthalmic glasses and lenses), or in potential uses such as optical storage (optical disks or memories). 

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