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

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