Time-Resolved Fluorescence Study on Liquid Oligo(ethylene oxide)s: Coumarin 153 in Poly(ethylene glycol)s and Crown Ethers

Abstract

We have investigated the solvation dynamics and reorientation of coumarin 153 (C153) in liquid poly(ethylene glycol)s with molecular weights of 150, 194, 238, 300, 400, and 600 and liquid crown ethers 12-crown-4 and 15-crown-5 using picosecond time-resolved emission spectroscopy. The observed subnanosecond solvation dynamics is characterized by a biexponential function. The faster solvation time constant is about 130 ps, and this time constant is insensitive to the molecular weight and the molecular geometric structures. The time constant for slower solvation dynamics (0.5−1.6 ns range) varies with the change of the molecular weight and the different molecular geometric structures of the macromolecules. The features of the orientational dynamics of C153 in poly(ethylene glycol)s and crown ethers are similar to those of the solvation dynamics. Both the slower solvation and reorientation time constants of coumarin 153 in poly(ethylene glycol)s are linearly correlated with the bulk viscosity.