Interchain dynamics and side-group modulation of excitons in a polydiacetylene

Abstract
Picosecond pump-probe spectroscopy has been used to investigate the interchain dynamics of excitons in the polydiacetylene poly-[2,4-Hexadiyn-1,6-diol-Bis(p-toluene sulfonate)] (PTS). At low temperatures, where neighboring chains are inequivalent, pumping either chain forms excitons that decay in a few picoseconds with no significant interchain energy transport. We observe a novel long-lived modulation of the exciton absorption which we attribute to coupling of photogenerated excitons with a dimerized antipolar lattice formed by the TS side groups. Full ground-state recovery does not occur until nanoseconds after photoexcitation.