Photophysical properties of PPP and PPV derivatives bearing polystyrene or polycaprolactone as side groups

Abstract

The photophys. properties were studied of poly(p-phenylene) (PPP) and poly(p-phenylene-vinylene) (PPV) derivs. laterally decorated with polystyrene (PPV-PSt) or poly(e-caprolactone) (PPP-PCL, PPP- alt PCL, PPV-PCL and PPV-PCL-Br). The polymers emit blue light and exhibit high relative and abs. photoluminescence quantum yield (Ff), in dil. soln., thin film (spin-coated and inkjet-printed), and bulk state. These parameters are ascribed to the side groups, which suppress the strong pi-pi interactions and, consequently, excimer formation. Lower Ff was obsd. for PPV-PCL-Br and its corresponding model compd. dibromo-distyrylbenzene Br2-DSB, which was ascribed to heavy atom effect enabling intersystem crossing from S1 to T1. However, studies at 77 K did not reveal phosphorescence; in contrast, an enhancement of the fluorescence intensity with respect to room temp. measurements was obsd.