Molecular dynamics of polystyrene model molecules: Solvent effects on intramolecular excimer formation in 2,4-diphenylpentanes

Intramolecular excimer formation in 2,4-diphenylpentanes has been examined in a homologous series of alkanes, in ethanol and in mixtures of ethanol, ethylene glycol and glycerol. The ratio of the emission intensities of dimer and monomer (I_D/I_M) is not affected in low viscosity solvents but, above 4 cP, viscosity effects are discernible and a relationship of the form I_D/I_M = Aη^?2 is obeyed. In methylene chloride, only the dl molecule exhibits a decrease of the efficiency of excimer sampling. The temperature dependence of I_D/I_M in isooctane and methylene chloride has been interpreted in terms of the activation energy of the excimer sampling.