Investigation of Random Copolymer Analogues of a Semi-Random Conjugated Polymer Incorporating Thieno[3,4-b]pyrazine

Abstract

Semi-random conjugated polymers based on 3-hexylthiophene have been extensively investigated within the past several years as an effective route to broadening absorption without losing desirable properties of poly(3-hexylthiophene) (P3HT). Here, we closely investigate the structural, optical, and electronic differences found in randomized analogues of poly(3-hexylthiophene–thiophene–2,3-dimethylthieno[3,4-b]pyrazine) (P3HTT-TP) semi-random polymers. Proton nuclear Overhauser effect spectroscopy is used to identify linkages within the conjugated backbone, and UV–vis, cyclic voltammetry, and grazing incidence X-ray diffraction are used to determine the influence of the subtle differences in monomer connectivities. Semi-random P3HTT-TP was found to have a stronger intramolecular charge transfer absorption band and higher thermal transitions compared to its randomized analogue. Additionally, the function of the thiophene unit in the semi-random polymers is observed and demonstrated to have key electronic effe...