Photochromic performance

Figure 2.10. Photochromic performance of a Transitions lens. (Reprinted from Ref. 45 with permission of copyright owner Chapman Hall Ltd.)...

A. Tomoda, A. Kaneko, H. Tsuboi, and R. Matsushima, Photochromism of heterocyclic fulgides. IV. Relationship between chemical structure and photochromic performance, Bull. Chem. Soc. Jpn., 66, 330-333 (1993). 

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. 

Photochromism of diarylethene single crystals Crystal structures and photochromic performance. Chem. Commun., 3895-3905. 

Photochromic performance was enhanced when the naphthopyran moiety was located in the middle rather than at the terminus. A middle disposition of the naphthopyran provides better encapsulation by the polymeric arms giving improved coloration and decoloration rates and higher optical density in the colored open-state [26]. 

Thermal treatment of photochromic glasses is generally possible, but the tempering process must be very closely controlled. The thermal stability depends on the type of the glass. If photochromic glasses are thermally overheated they may become distorted and have a degraded photochromic performance. It is therefore recommended to keep the temperature below about 200°C and to use only short durations of tempering. 

When foiu thiophene rings are connected to all four carbons of a central alkene, as illustrated with compounds 67 and 68 [136], photochromic performance is sacrificed and only minor amounts of the ring-closed isomers are observed in the photostationary states when solutions of the compounds are irradiated with UV light. In fact, in the case of derivative 67, no new absorption peaks appear in the visible region of the... 

Cheng T, Lin T, Brady R, Wang X (2008) Photoehromic fabrics with improved durability and photochromic performance. Fibers Polym 9 521-526... 

Ercole E, Malic N, Davis TP, Evans RA (2009) Optimizing the photochromic performance of naphthopyrans in a rigid host matrix using poly(dimethylsiloxane) conjugation. J Mater Chem 19 5612-5623... 

IV. Relationship between chemical structure and photochromic performance. Bull. Chem. Soc. Jpn., 66, 330-333. 

Diarylethenes with heterocyclic aryl groups are newcomers to the photochromic field. They belong to the thermally irreversible (P-type) photochromic compounds. The most striking feature of the compounds is their fatigue resistance. The coloration/decoloration cycle can be repeated more than 10 times while retaining the photochromic performance. Both properties, thermal stability of both isomers and fatigue resistance, are indispensable for application to optoelectronic devices, such as devices for memory and switches. In this chapter, recent research on diarylethene derivatives will be described. 

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