Arylene-ethynylene/arylene-vinylene copolymers: Synthesis and structure-property relationships

Poly(arylene-ethynylene)-alt-poly(arylene-vinylene)s (PAE-PAVs) are a new class of conjugated compounds combining the intrinsic properties of both poly(arylene-ethynylene) (PAE) and poly(arylene-vinylene) (PAV) into a single polymeric backbone with additional structure-specific properties. On the one hand, they exhibit red-shifted absorption and emission spectra as well as an enhanced solid state photoluminescence quantum yield as compared to PAEs and, on the other hand, they show enhanced electron affinity as compared to PAVs, which is reflected by low turn-on voltages of light-emitting diodes and higher open circuit voltages of organic solar cells manufactured with the help of these new materials. This article reviews the various synthetic paths and establishes structure-property relationships of so far reported PAE-PAV systems. Properties in solution, thin film (drop casted, spin-casted, inkjet printed) and in bulk (as polymerized and as extruded) and theoretical photophysical aspects are presented and discussed. For a better understanding of the photophysical properties so far unpublished results from low temperature investigation have been included. In general the properties of PAE-PAVs are governed by the combined effects of (i) backbone conjugation pattern, i.e. triple bond/double bond ratio and ortho- or para-linkages between the phenylene units, and (ii) nature (linear or branched), number, position, and length of the solubilising alkyl and/or alkoxy side groups.