FLUORESCENCE PROBES AS A TOOL FOR STUDYING MICROENVIRONMENT OF SUPPORTED SPECIES .2. NONRADIATIVE ENERGY-TRANSFER AND SITE ACCESSIBILITY

Non-radiative fluorescence energy transfer measurements have been used to characterize solvent penetrability and site accessibility of labelled copolymers. These polymers were either soluble, crosslinked or grafted on porous silica. Carbazole chromophore, involved as an energy-transfer donor, has been introduced in different polymer structures mainly in the form of a styryl derivative. The anthracene probe has been generally dispersed in the solvent phase. Application of Stern-Volmer theory allows obtaining of the overall energy transfer constant K. Since these K values depend strongly on solvent and polymer structure, they give good information on the investigated system. The hydrophilic silica surface induces an extended chain conformation. As a consequence, coil expansion is more sensitive to solvent nature than in the case of an organic support.