Radical–radical coupling of polystyrene chains using AGET ATRC

Abstract

AbstractActivators generated by electron transfer (AGET) was integrated into atom transfer radical coupling (ATRC) systems to drastically reduce the amount of copper catalyst required to achieve dimerization of monohalogenated polystyrene (PStX) precursors. PStCl or PStBr, prepared by ATRP, were activated and coupled in ATRC systems with varying equivalents of the reducing agent tin(II) ethyl hexanoate (Sn(EH)2) with ligand‐bound copper(I) and/or copper(II) present. Effective coupling was only observed in PStBr systems, with total copper content in the reaction mixture able to be reduced into the range of 10–25% of what is typically reported in traditional ATRC reactions of PSt while maintaining coupling yields of >50%. Additional reducing agents, glucose and ascorbic acid, were also studied and were found to be even more effective in some AGET ATRC reactions compared with Sn(EH)2. Best results were achieved with ascorbic acid as the reducing agent (>80% coupled product) with total copper content 25% of what was used for a traditional ATRC. Using an activators regenerated by electron transfer ATRP–AGET ATRC sequence resulted in an overall reduction of total copper down to 0.1–0.25% for the overall reaction sequence (compared with a traditional ATRP–ATRC sequence). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010