Minimization of the Auxiliary Reagent Loading for Direct Arylation Polymerization (DArP) of 2-Bromo-3-hexylthiophene

In this work, we present a powerful set of synthetic strategies aimed at minimization of auxiliary reagent loading for direct arylation polymerization (DArP) of 2-bromo-3-hexylthiophene. As such, we report efficient lowering of Pd(OAc)(2) catalyst loading as well as loading of other auxiliary reagents, such as neodecanoic acid and N,N-dimethylacetamide. Unprecedented low loadings of catalyst down to 0.0313% (313 ppm) were achieved, while producing polymer in high yield (91% after Soxhlet extraction), with a high molecular weight (24.2 kDa) and carefully controlled chemical structure thus making the optimized DArP protocol significantly more cost-effective, convenient, sustainable, and environmentally friendly. The resulting polymer samples were thoroughly investigated in terms of their chemical structure as well as optical, thermal, chain ordering and electronic properties using GPC analysis, H-1 NMR, MALDI, UV-vis, GIXRD spectroscopy, DSC, and SCLC hole mobility measurements. The results demonstrate that the reagent lowering strategies increase the polymer regioregularity from 94.6 to 96.5% as evidenced by H-1 NMR spectra and corroborated by GIXRD, DSC, and UV-vis measurements. Additionally, polymer samples obtained at low reagent loading are more uniformly proton-terminated as evidenced by H-1 NMR and MALDI end-group analysis. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1492-1499