Stabilization of spirooxazines

Indolinospirooxazines are inherently more fatigue resistant than the spiropyr-ans. As measured by the quantum yield for photodegradation, the spironaphthox-azines are two or three orders of magnitude more photostable than the spirobenzopyrans. 37 From the point of view of industrial applications, spirooxazines are reported to be stabilized even further by various protective methods. 

Kawasaki et al.40 disclosed the use of hindered phenols such as 2,6-di(tert-butyl)phenol as stabilizers for spirooxazines in poly (vinyl butyral). The hindered phenols not only improved photochromic durability but also photochromic response, besides accelerating the thermal recovery rate. 

The thermal fading of spirooxazines has been shown to be dependent on the matrix. Tateoka et al. 42 reported that the fading rate for the colored form could be increased by adding a plasticizer, for example, dibutyl phthalate to poly(vinyl 

Malatesta 43 investigated the photochromism and thermochromism of spirooxazines in cationic (CTAB, hexadecyltrimethylammonium bromide) and nonionic (TX-100) micellar solutions, and in sodium bis-2-ethylhexylsulfosuccinate (AOT) toluene-water inverted micelles. The thermo- and photocolorability increased in TX-100 and CTAB micelles and decreased in inverted micelles. 

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