Thermal stability of the ­spironaphthoxazine colored form in ­polymeric siloxanes

Abstract

In order to improve the thermal stability of colored merocyanine formed by the photochromic reaction of spironaphthoxazine, the spiro compound was incorporated in polymeric siloxanes. They are liquid poly-(methylphenylsiloxane) and solid methyl-or phenylsiloxane resins prepared by the hydrolysis and condensation reactions of the corresponding di-or tri-ethoxysilane. To the polymers the spirooxazine moiety is bonded covalently. Higher stability of the colored form was not observed in the liquid polysiloxane, but in the solid resins. The phenyl substituent in the resin is more effective than the methyl one for stabilization, suggesting that the bulky substituent in the vicinity of the spirooxazine moiety is important as well as stiff polymer matrices. The phenylsiloxane resin with the spirooxazine moiety was enclosed in rigid sol±gel silica, but a further improvement of the thermal stability was not observed.

A Photochromic Copolymer Hydrogel Contact Lens: From Synthesis to Application

“…The relaxation life of hydrogel made by polymerization method was 289 s which was longer than that made by immersing method (199 s); this could be assigned to the participation of SPO in polymerization reaction. As had been reported by earlier work [34], in solid resins, the bulky substituent in the vicinity of the spirooxazine moiety was benefit to the thermal fading stability of MC. For SPO in hydrogel made by polymerization method, the volume of substituent group on 9 -C is bigger than that made by immersing method, which depressed the large conformational change more effectively in the photochromic reaction.…”

Fast response photochromic textiles from hybrid silica surface coating

“…As a result, the photochromic molecules in the OctSi matrix showed higher speed in both optical response and colour fading than that in the MeSi matrix. In contrast, phenyl groups normally form rigid pores, and the pores are enlarged because of the steric effect of phenyl plane (Scheme 3) [49,50]. The quick response speed confirms that the pores in the PhSi matrix have a relatively large volume.…”

Preparation and Photochromic Performance of Homogeneous Phase Nitrocellulose Membrane Grafting Spirooxazine Moieties

“…Most of the MC forms of spiropyrans and spirooxazine are thermally unstable at room temperature, hindering further commercial applications [11,12]. As a rule, incorporating them in the polymer matrices not only makes it easier for the processing device but also improves the thermal stability of their MC form by retarding the chemical reaction because of steric hindrance [13][14][15].…”