End‐group composition of poly(3‐hexylthiophene)s prepared by in situ quenching of the grignard metathesis polymerization: Influence of additives and reaction conditions

The ability to prepare well‐defined semiconducting polymers is essential for understanding the link between structure and function in organic photovoltaic devices. A general, one‐pot method for altering the degree of functionality of end‐functionalized poly(3‐hexylthiophene)s (P3HT) prepared by Grignard metathesis (GRIM) polymerization has been developed. In the absence of additives, the degree of functionality of end‐functional P3HTs prepared by quenching of the GRIM polymerization with a Grignard reagent is dependent on the Grignard reagent utilized. In this study, additives such as styrene and 1‐pentene are shown to alter the end‐group composition of tolyl‐functionalized P3HTs as determined by Matrix‐assisted Laser Desorption Ionization Time‐of‐flight Mass Spectrometry. In particular, when quenching the GRIM polymerization with tolylmagnesium bromide, a modest decrease in the difunctional product is observed, and the yield of the monofunctional product increases significantly. Temperature and lithium chloride (LiCl) addition also play impactful roles. Monofunctional P3HT is found to be the major product (72% abundance) when the functionalization is done in the presence of LiCl and styrene at 0 °C, whereas in the absence of additives the monofunctional product is present at only 11% abundance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012