Iron-Based ICAR ATRP of Styrene with ppm Amounts of FeIIIBr3 and 1,1'-Azobis(cyclohexanecarbonitrile).

Abstract

A successful ICAR (initiators for continuous activator regeneration) ATRP (atom transfer radical polymerization) of styrene was conducted with iron(III) bromide and 1,1'-azobis(cyclohexanecarbonitrile) (ACHN) as the thermal initiator. A polymerization, started with 50 ppm of FeBr3 and 50 mol equivalents of ACHN in 33% (v/v) anisole at 90 °C, reached 70% conversion in 24 h and was well controlled, giving a polymer with a narrow molecular weight distribution (Mw/Mn = 1.15). The number average molecular weight (Mn) corresponded well to theoretical values, as conversion increased. The rate of polymerization was dependent on the amount of ACHN initially added to the reaction. A polymer with a relatively narrow molecular weight distribution, Mw/Mn = 1.29 at 65% of conversion, was obtained with 5 ppm of FeBr3 and the appropriate amount of ACHN. This procedure therefore provides an efficient controlled polymerization in addition to creating a robust, cheap, and environmentally friendly catalytic system. Control of polymerization with ACHN was better than with tert-butyl peracetate as a thermal initiator or tin(II) 2-ethylhexanoate, Fe0, or Zn0 wire as reducing agents.