Abstract: The fluorescence of polyethylene glycol bis-2-naphthoates (Pn) in different solvents were measured under stationary and nonstationary conditions at various temperatures. Contrary to that in good solvents such as tetrahydrofuran, Pn show strong excimer emission in methanol, suggesting that hydrophobic interactions bring the two chromophores of Pn in proximity. The activation energy and enthalpy change for excimer formation were obtained to be 8.5 kJ/mol and -20 kJ/mol respectively. The rates for excimer formation and dissociation were also calculated to be 4.5×10⁸s^-1 and 3.1×10⁸s^-1 respectively by means of time-resolved fluorescence measurement.

Key words: conformation of molecules, intramolecular excimer, hydrophobia and lipo-phobic interaction, polyethylene glycol, dynamics of excimer formation