Rapid Synthesis of Well-Defined Polyacrylamide by Aqueous Cu(0)-Mediated Reversible-Deactivation Radical Polymerization

Abstract

Atom transfer radical polymerization (ATRP) of acrylamide (AM) has proved challenging, typically exhibiting low conversions and broad molecular weight distributions (MWDs). Herein, we report the synthesis of well-defined polyacrylamide (both homo and block copolymers) via aqueous copper(0)-mediated reversible-deactivation radical polymerization (Cu(0)-RDRP), exploiting the in situ disproportionation of Cu(I)Br in the presence of Me6Tren to yield insoluble Cu(0) and Cu(II)Br2 which acts as a deactivator. Careful optimization of the levels of Cu(I)Br and Me6TREN allowed for the synthesis of polyacrylamide of a range of molecular weights (DPn = 20–640) proceeding to quantitative conversion within just a few minutes (typically full conversion is attained within 15 min of reaction time) and exhibiting narrow MWDs (Đ as low as 1.09), which represents a significant improvement over transitional-metal-mediated approaches previously reported in the literature. This optimized approach was subsequently utilized to perform in situ chain extensions and block copolymerizations with hydroxyethyl acrylamide, yielding block copolymers of low dispersity and quantitative monomer conversions in a time frame of minutes.