Optimization of Narrow Band-Gap Propylenedioxythiophene:Cyanovinylene Copolymers for Optoelectronic Applications

Four analogues of the narrow band gap poly(3,4-propylenedioxythiophenedialkyl)cyano-p-phenylenevinylene (PProDOT−R2:CNPPV) polymer family have been designed with the goal of improving the film forming ability and utility of this family of polymers when applied in redox switchable and optoelectronic devices. These polymers were synthesized via Knoevenagel condensation with yields ranging from 40 to 80%. Number-average molecular weights between 9000 and 24 000 g mol-1 were estimated using size exclusion chromatography, and the polymer repeat unit structures and end groups were confirmed by MALDI mass spectrometry. Linear and branched alkoxy substituents were introduced along the polymer backbone to yield materials highly soluble in chloroform, THF, and toluene, and homogeneous films were prepared by spin-coating or spray-casting from organic solutions. The identity of the substituents has a significant effect on the optical properties of the polymer solutions. A blue-shift in the absorption was observed by ...