Femtosecond fluorescence dynamics and molecular interactions in a water-soluble nonlinear optical polymeric dye

The excited state dynamics of a water-soluble polymeric dye poly(S-119) was investigated using femtosecond time-resolved fluorescence upconversion. Mu lti-exponential relaxation of fluorescence was observed for poly(S-119) in picosecond and sub-picosecond time ranges. The azo-chromophore of the funct ionalized polymeric dye Sunset Yellow was used as a model compound for deta iled investigations of intermolecular interactions. Excited slate decay of this ate-dye can be described by a two-exponential decay law with time-cons tants of similar to 0.48 ps and 1 ps. Fluorescence anisotropy decay was inv estigated for both systems. The difference in excited state dynamics betwee n the polymeric dye and the azo-chromophore is explained in terms of inter- molecular interactions resulting in intra-chain aggregate formation. (C) 20 00 Elsevier Science B.V. All rights reserved.