Photochromism of spirooxazines in mesoporous organosilica films

• Published in: Journal of materials chemistry Vol. 18; no. 27; pp. 3242 - 3248
• Main Authors: RABOIN, Lorraine, MATHERON, Muriel, BITEAU, John, GACOIN, Thierry, BOILOT, Jean-Pierre
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2008
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from solutions; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of crystal growth; physics of crystal growth; Methods of deposition of films and coatings; film growth and epitaxy; Other materials; Physics; Specific materials; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Photochromism; Porous materials; Organometallic compounds; Mechanical properties; Layer thickness; Mesoporosity; Optimization; Thin films; Hexagonal lattices; Composite materials; Crystal growth from solutions; Methyl compounds; Silica gel; Sol-gel process
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b802608d

In order to increase the colourability and improve the mechanical properties of sol-gel photochromic films, we present an original strategy in which spirooxazine (SO) molecules are dispersed in mesoporous organized films using the impregnation technique. Two types of SO photochromic molecules are trapped in sol-gel matrices. The first one allows optimization of the chemical and steric interactions between SO molecules and the sol-gel matrix. The second one leads to fast photochromism as previously observed in soft hydrophobic sol-gel matrices and mesostructured silica composites. The pore accessibility into the matrix and environments for spirooxazine molecules are optimized in robust 3D-hexagonal mesoporous films containing high amounts of methyl groups at the pore surface. After impregnation by a spirooxazine solution, the photochromic response is only slightly slower when compared with mesostructured or soft sol-gel matrices, showing that methyl groups offer good environments for spirooxazines. Moreover, the molecular loading in films is easily adjustable in a large range using a multi-impregnation procedure and increasing the film thickness.