AGGREGATION OF PYRENE IN POLY(ALKYL METHACRYLATE) FILMS REVEALED BY TIME-RESOLVED TOTAL INTERNAL-REFLECTION FLUORESCENCE SPECTROSCOPY

Fluorescence spectra and decay curves of pyrene in poly(alkyl methacry late) (methyl, n-propyl, isobutyl and cyclohexyl) films cast on sapphi re substrates were measured under total internal reflection and normal excitation conditions, and were compared with each other. On the basi s of the intensity ratio of the excimer to the monomer fluorescence an d the fluorescence decay curve under the normal condition, the degree of pyrene aggregation in these films is discussed in terms of the solu bility parameter, chain flexibility and hydrophobicity of the host pol ymers. Both the difference in the degree of pyrene aggregation and the difference in micropolarity around pyrene molecules between the vicin ity of the sapphire/polymer interface and the bulk were found to be qu ite common for these polymer films cast on sapphire plates, and are di scussed in terms of the interaction between substrate surface and poly mers. The effect of tacticity of poly(methyl methacrylate) on the degr ee of the pyrene aggregation and the effect of labelling with pyrene w ere also investigated.