Mixed Alkyl‐ and Alkoxy‐Substituted Poly[(phenylene ethynylene)‐<i>alt</i>‐(phenylene vinylene)] Hybrid Polymers: Synthesis and Photophysical Properties

Abstract

Abstract Summary: We report the synthesis, characterisation and photophysical properties of mixed alkyl‐ and alkoxy‐substituted poly[(phenylene ethynylene)‐ alt ‐(phenylene vinylene)] hybrid polymers with the general constitutional unit: (PhCCPhCCPhCHCHPhCHCH) n ( 7 ). The polymers were obtained through the Horner‐Wadsworth‐Emmons olefination reaction of alkyl‐substituted luminophoric dialdehydes, 5a–b , and alkoxy‐substituted bisphosphonates. Contrary to their alkoxy‐substituted congeners, 10a–b , which exhibit solution fluorescence quantum yields close to unity, dialdehydes ( 5a–b ) fluoresce poorly at room temperature, but show phosphorescence at 77 K. High molecular weight polymers were obtained showing poor solubility compared to solely alkoxy‐substituted polymers ( 11 ) of the same backbone constitutional units. The presence of alkyl side groups in 7 leads to a 15 nm blue shift of their absorption spectra relative to 11 . Both types of polymers show however identical emission spectra with only a slight blue shift (3–4 nm) of the emission peak of 7 relative to 11 . This clearly proves that the chromophore system responsible for the emission in both types of compounds is located around the lower‐energy, alkoxy‐substituted phenylene‐vinylene portion of the polymers as confirmed by fluorescence kinetics investigations. magnified image