Synthesis and optical properties of novel poly(p-phenylene ethynylene)s

In order to explore the influence of chemical modifications on the photophy sical properties of poly(p-phenylene ethynylene)s (PPEs), a series of PPE-c opolymers was synthesized employing Heck-type cross-coupling reactions. UV/ Vis absorption and photoluminescence experiments clearly demonstrate that t he design of PPE-copolymers which comprise conjugated segments of well-defi ned length and (aliphatic) spacers in a strictly alternating fashion allows to tune the bandgap to higher energies, and thus the absorption and emissi on maxima to shorter wavelengths. Thr derivatization of the PPE backbone wi th electron-withdrawing substituents, by contrast, is found to be significa ntly less effective and only leads to comparably small shifts in the absorp tion and emission spectra.