Photochromic sol-gel materials

Dai S., Sigman M.E., Burch E.L. Preparation of a photochromic glass doped with methylviologen radical cation via a sol-gel process. Chem. Mater. 1995 7 2054-2057 del Monte F., Levy D. Formation of fluorescent rhodamine B J-dimers in sol-gel glasses induced by the adsorption geometry on the silica surface. J. Phys. Chem. B 1998 102 8036-8041 Dunn B., Mackenzie J.D., Zink J.I., Stafsudd O.M. Solid-state tunable lasers based on dye-doped sol-gel materials. Proc. SPIE vol. 1328 Sol-Gel Optics 1990 1328 174-182 Dunn B., Zink J.I. Probes of pore environment and molecule-matrix interactions in sol-gel materials. Chem. Mater. 1997 9 2280-2291... 

The photochromism of azobenzene probe molecules tells us furthermore that bulk materials differ distinctively from silica films.59 The pores in the sol-gel bulk materials were larger than those in the corresponding sol-gel films. The first-order kinetics of the thermal isomerization of the photogenerated Z-isomer revealed that the steric effects restricting the molecular motion increased in the order sol-gel... 

Therefore, the chemical linking of the dye molecules is only worthwhile if it results in a substantially better performance of the resulting materials. For the reasons discussed below, this is mainly expected for nonlinear optics (NLO) dyes. However, other dye-containing materials were also prepared by this approach. For example, new transparent photochromic hybrid materials were prepared by sol-gel processing of Si(OEt)4, sUanol-terminated dimethylsiloxane oligomers and triethoxysilylpropyl-substituted spirobenzopyranes, and fluorescent glasses and films from pyrene derivatives covalently tethered to RS103/2 (R = alkyl, phenyl) . 

Levy D., Einhorn S., Avnir D. Applications of the sol-gel process for the preparation of photochromic information-recording materials synthesis, properties, mechanisms. J. Non-Cryst. Solids. 1989 113 137-145... 

---