Switchable optical properties

Coe, B. J., Molecular materials possessing switchable quadratic nonlinear optical properties. Chem. Eur. J. 1999, 5, 2464-2471. 

The photochemistry of LC polymers is not only interesting for fundamental reasons (vide supra) but because they can perhaps be formed into useful materials— films, fibers, rods, etc., with specifically tailored mechanical and/or optical properties. Their photochemical reactions may be used to modify these properties in an easily controlled, switchable manner. There is already a considerable body of knowledge on the possible practical applications of a few photochemical reactions of LC polymers. Such possible applications are discussed elsewhere [1-6] and are only briefly touched upon in this chapter. Furthermore, this chapter does not include an extensive compilation of information about the many types of LC polymers, the many methods used to synthesize and process these materials, their detailed properties, and the theoretical basis of their formation and properties. The reader is referred elsewhere [7,8] to capable reviews of these topics. However, a brief introductory review of the main types of LC polymers and their properties that are especially relevant to their photochemistry is given in Section II. 

H. L. 1997, Yttrium and lanthanum hydride films with switchable optical properties, J. Alloys and Compounds 253-254 44. 

A three-level switching device has been demonstrated in which photochromic properties are used to control electrical properties, and vice versa. Such a system has been realized in the form of thiophene bisphenol [90, 91]. Conversion of the open (8a) to the closed (8b) form of the thiophene was achieved by absorption of 312 nm light, and revered by absorption of 600 nm light. The bisphenol oxidation occurs at +0.735 V (vs. SCE), forming the closed-ring bisquinone, compound 8c. This species has large absorptions at 400 and 534 nm. The optical properties of the quinone phenol couple have previously been used in a bianthrone-based system [87]. The bisquinone (8c) cannot be converted to the open thiophene, and locks the system in the closed form. The thiophene has also been incorporated as a component in two-level molecular switches [99, 128] and switchable molecular wires [30]. 

In more recent times, the field has increasingly focused on topics where molecular materials have an advantage over continuous-lattice solids. Such studies can exploit the modular synthesis of molecular materials, whereby different molecules with differing functions can be combined to form a hybrid material with interacting magnetic and/or conducting and/ or optical properties. This is leading to new fields such as molecular spintronics, multifunctional and switchable materials where... 

Optical Properties of Metal Hydrides Switchable Mirrors I 275... 

The purpose of this article is to review the essential properties of switchable mirror materials with special emphasis on their optical properties. So far three generations of hydrogen-based switchable mirrors have been discovered ... 

Optical Properties of Meta Hydrides Switchable Mirrors 311... 

Finally, further research effort is worth being made on materials for recording optically switchable diffraction gratings. Optical control of optical properties, such as the diffraetion, is not only academic curiosity but required for the... 

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