Intramolecular excimer formation and energy migration in head-to-head polystyrene

Abstract Head-to-head polystyrene (HH-PS), in which the phenyl rings are separated by either two or four carbon atoms, displays predominantly fluorescence from monomeric units. No excimer emission is observable even when the polymer is dissolved in increasingly thermodynamically poorer solvents. This is strongly suggestive that excimer formation in normal head-to-tail polystyrene (HT-PS) occurs primarily between nearest-neighbouring chromophores. Intramolecular energy migration is shown to be negligible in both fluid and solid solutions of HH-PS. This is in direct contrast to the case with HT-PS in fluid solutions in which an energy migration coefficient of 7.5 × 10 −5 cm 2 s −1 and an energy migration frequency of 4.1 × 10 11 s −1 were determined.