Iron-Based ICAR ATRP of Styrene with ppm Amounts of Fe^IIIBr₃ and 1,1′-Azobis(cyclohexanecarbonitrile)

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 (<i>M</i>_w/<i>M</i>_n = 1.15). The number average molecular weight (<i>M</i>_n) 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, <i>M</i>_w/<i>M</i>_n = 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 <i>tert</i>-butyl peracetate as a thermal initiator or tin­(II) 2-ethylhexanoate, Fe⁰, or Zn⁰ wire as reducing agents