Organic photochromic material

H. G. Heller, New fatigue-resistant organic photochromic materials, in Fine Chemicals for the Electronics Industry (P. Bamfield, ed.), pp. 120-135, Royal Soc. Chem., London (1986). 

V. V Belov, V. A. Barachevsky, N. I. Bolondaeva, V.M. Kozenkov, N. T. Poteleshenko, A. A. Yastrebov, and P. P. Kisilitsa, Organic photochromic materials with nondestructive read-out information, in Abstracts of Papers on II All-Union Conference on Holography, 1975, Part I, pp. 50-51 (Russ.). 

Organic photochromic materials are typically prepared as a solution in an inert rigid matrix (such as a polymer) or a pure crystal. For materials in a matrix, the achievable concentrations... 

To the best of our knowledge, most of the work on refractive-index recording in organic photochromic materials has been directed toward systems for holographic recording. Furthermore, this work has been concerned with reading out the stored... 

Aryl-substituted fulgides are the products of condensation of aromatic ketones with succinic anhydride, and form one of the oldest and most important groups of organic photochromic materials. First discovered in the early part of the last century by Slobbe- ", they are now well known to owe their photochromic behavior to reversible (comotatory)... 

Shumburo A, Biewer MC (2002) Stabilization of an organic photochromic material by incorporation in an organogel. Chem Mater 14 3745—3750... 

Photochromism, which refers to the reversible color change of a compound with light irradiation, is attracting much attention for the construction of molecular devices. During the past decade there has been a growing interest in the synthesis, properties, and applications of organic photochromic materials [1-5],... 

Many organic and inorganic materials have photochromic properties, such as metal oxides, titanates, copper components, mercury components, transition metal oxides for inorganic photochromic materials, and spiropyranes, spirooxazines, chromenes, fulgides, flumigides and diarylethenes for organic photochromic materials. 

Photochromic dyes, 20 516 Photochromic glass silver in, 22 658, 686 as a solar energy material, 23 5 Photochromic lenses, 6 588, 601-602 Photochromic materials, 6 587-606 inorganic, 6 589-592 organic, 6 592-601 polyoxometalates, 6 591-592 silver halide-containing glasses, 6 589-590... 

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). 

A highly efficient photochromic process is essential for organic photochromic compounds used as optical recording materials.39,40 That means that the quantum yields for the photocoloring and bleaching reactions should be high, but the quantum yield for the side reactions should be as low as possible. In order to solve the problems mentioned earlier, extensive studies have been carried out, and some promising results have been obtained so far. 

Photochromic compounds functioning by an oxidation-reduction mechanism (electron transfer), especially a photoreduction mechanism, are known in inorganic materials such as silver halides, which are utilized in eyewear lenses. Although the number of organic photochromic compounds operating via electron transfer is fewer than those by isomerization, heterolytic (or homolytic) cleavage, and pericyclic reactions, several classes of compounds have been reported, such as thiazines,1 viologens,2 and polycyclic quinones.3... 

Organic photochromic systems have actual applications in variable transmission optical materials, authentication systems and novelty items. In addition, they offer great potential in erasable optical memories and many other fields where reversible changes of physical properties other than color are wanted. The domain is interdisciplinary and expanding. 

In 1899, Marckwald discovered that two separate organic compounds, 2, 3, 4, 4-tetrachloro-1 -(4//)-naphthalenone and benzo [c]-l, 8-naphthpyridine hydrochloride, developed color in sunlight and lost this color when placed in the dark. The study of photochromic materials had begun. 

When we intend to apply organic molecular materials, especially photochromic dyes, to optical memory media, the indispensable condition is stability, both thermal and photochemical. The photogenerated isomers are required never to return to the initial isomers in the dark, even at elevated temperatures, e.g., 80 °C. In addition, the coloration/decoloration can be cycled many times while the photochromic performance is maintained, and the memory media are provided with nondestructive readout capability. Although several molecules which fulfill the former condition have been developed, some problems still remain to gain access to molecules and systems which fully satisfy the latter condition. 

Chapter 2 (Photodegradation of Organic Photochromes). This chapter deals with the crucial problem of photodegradation of photochromic materials, largely... 

Photochromism proceeds, in general, in condensed phases and is affected markedly by the nature of the matrix. Polymeric materials play a very crucial role in studies on photochromism, in particular from a practical viewpoint since various applications require photochromic materials in the form of films, sheets, plates, fibers, beads, and so on. Photochromic molecules have usually been incorporated into polymer matrices by binding them covalently to polymer backbones or by dissolving or suspending them in polymer solids. The photochemical as well as thermal behavior of organic photochromic molecules is influenced in various ways by the characteristics of the polymeric media so that photochromic polymers have attracted extensive interest, leading to interdisciplinary research.1,2... 

Photochromic materials based on different classes of spiropyrans (SPs) are widely used in various fields of science and technology, such as in the production of light filters regulating luminous fluxes, as photochromic organic media for processing optical information, for photochromic optics, and in the production of nonlinear optical materials. In recent years, the study of new SPs has been conducted mainly in two directions, namely, the search for new classes of SPs and structural modification of the known systems to improve their basic characteristics (quantum yield of photoconversion, the stability of the photoisomer produced, the number of cycles of operations). Only a profound comprehension of mechanisms of photoinitiated rupture of the Cspiro—O bond, structural isomerization, ways of stabilizing the photoisomer, routes of its breakdown, and influence of the structure of SPs on their properties can provide the basis for purposeful research in this area. Despite the vast number of investigations in this area, the mechanisms of the photochromic conversion of SPs and the influence of structural features on their photochemical properties are not well understood. This complicates the search for and synthesis of new SP classes. 

It is clear that this volume is truly different from the preceding accounts. Photochemists will appreciate Volume 2 as a nice complement to Volume 1, although it can be read independently. Organic photochromic systems are known for their applications in variable-transmission optical materials, ophthalmic lenses, authentification devices (photochromic inks), and novelty items, but they also have great potential in any domain where reversible physical properties are desired (optical memories, gradation masking, optoelectronic systems, nonlinear optical devices, etc.). This book is thus strongly recommended to anyone interested in materials science. 

Recent advances in organic photochromic storage materials, and photochromic switching, have also been described. 

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