Journal of Polymer Science Part A: Polymer Chemistry, Vol.57, No.20, 2113-2120, 2019
Atom Transfer Coupling Reactions Performed With Benign Reducing Agents and Radical Traps
Monobrominated polystyrene (PSBr) was prepared by ATRP, and the resulting chain ends were activated in the presence of radical traps to induce chain end-coupling. In atom transfer radical coupling (ATRC) with radical trap assistance, to achieve significant coupling requires excess metal catalyst, ligand, and a reducing agent that is often additional metal. In this work, activators generated by electron transfer (AGET) and radical trap assistance are used in the ATRC sequence to successfully lead to chain-end coupling without the need for the oxidatively unstable copper (I) and with environmentally friendlier agents in place of copper metal. High extents of coupling (Xc) were achieved using ascorbic acid (AA) as the reducing agent and copper(II) bromide as the oxidized version of the catalyst, and when combined with AGET ATRP to prepare the PSBr precursor, only a fraction of the total metal was required compared to traditional atom transfer reactions, while still retaining similar Xc values. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019
Keywords:atom transfer radical coupling;atom transfer radical polymerization;polystyrene;green chemistry