PROBING THE MICROENVIRONMENT OF POLYMER-IMPREGNATED COMPOSITE GLASS USING SOLVATOCHROMIC DYE

Poly(methyl methacrylate) (PMMA)-impregnated silica composite glasses are hosts for organics in advanced optics applications. The advantages of composite glasses are their high optical quality and mechanical strength. Composite glasses are composed of a silica skeleton which contains narrow channels. Organic polymeric chains such as longitudinal PMMA chains fill these channels to form an inorganic:organic composite glass. Using 6-propionyl-2-(dimethylamino)naphthalene (PRODAN), a solvent-sensitive dye, we probed the local microenvironment in these PMMA/silica composite glasses using steady-state and time-resolved fluorescence. The steady-state fluorescence results clearly demonstrate that the Stokes shifts (Delta nu) obtained for PRODAN in solid matrices (composite glass, pure PMMA, and pure silica-gel glass) are in good agreement with the expected dependence in orientational polarizability (Delta f) obtained for liquid solvents. These results also demonstrate that the dye molecules are primarily surrounded by a PMMA-like environment, but there is a distinct influence of the silica skeleton and the hydrogen bonds which connect the silica matrix and PMMA. The time-resolved fluorescence results also suggest a multidomain microenvironment for the PRODAN molecules within the composite glass.