PHOTOPHYSICAL STUDY OF POLY-(METHYL METHACRYLATE) CONTAINING INDOLIC GROUPS

3-(3-indoyl)-propyl methacrylate (IPM) was prepared and subsequently c opolymerized with methylmethacrylate (MMA) in order to obtain a poly-( methyl methacrylate) containing fluorescent indolic groups (PMMI). 3-( 3-indoyl)-propyl isobutyrate (IPI), was also synthetized as a model co mpound. Characterization of the polymer gave a molecular weight of 200 ,000 and a mean average number of 2.5 indolic units per chain. The mod el compound and the polymer showed the same absorption spectra, with a maximum at 280 nm. The emission spectra for both compounds were stron gly dependent on the solvent, with a shift of the emission wavelengths towards the red in polar solvents. In a given solvent, both polymer a nd model emit at the same wavelength, the only exception for this was observed when 1-propanol was employed as solvent. This was attributed to a ''chain effect'' exerted by the strongly folded macromolecule, sh ifting the emission wavelength toward values corresponding to polariti es lower than the bulk solution. In solvent mixtures, the maximum emis sion wavelength shifts can be considered as indicative of the probe en vironment, reflecting a sort of preferential adsorption of the compone nt with the highest thermodynamic power onto the macromolecular chains . Finally, a number of quenching experiments were performed in pure so lvents and solvent mixtures, showing that the deactivation process is diffusion-controlled. The lower values found for the polymer could ind icate that the quencher finds a certain resistance to penetrate the po lymer coil, which might be due to steric effects or a higher local vis cosity within the macromolecular coil.