Inorganic Sulfites: Efficient Reducing Agents and Supplemental Activators for Atom Transfer Radical Polymerization

Abstract

Inorganic sulfites such as sodium dithionite (Na₂S₂O₄), sodium metabisulfite (Na₂S₂O₅), and sodium bisulfite (NaHSO₃) have been studied as reducing agents for atom transfer radical polymerization (ATRP). They act not only as very efficient reducing agents but also as supplemental activators for SARA (supplemental activator and reducing agent) ATRP of methyl acrylate in DMSO at ambient temperature. In combination with Cu(II)Br₂/Me₆TREN, they produced poly(methyl acrylate) with controlled molecular weight, low dispersity (M_w/M_n = 1.05), and well-defined chain-end functionality. Sulfites are eco-friendly, approved by FDA as food and beverage additives, and used commercially in many industrial processes.