Towards more controlled poly(n-butyl methacrylate) by atom transfer radical polymerization

The homogeneous controlled/‘living’ free radical polymerization of n-butyl methacrylate in toluene or o-xylene at 90 °C, in bulk and in solution, using the novel combination of the catalyst bis-triphenylphosphine iron(II)chloride tetrahydrate (FeCl₂ · 4H₂O(PPh₃)₂) with ethyl 2-bromoisobutyrate ((CH₃)₂CBrCO₂Et)) and α,α-dichloroacetophenone (CHCl₂COPh) as initiators has been investigated. The rate of polymerization initiated by the two initiators exhibited first-order kinetic with respect to the monomer. A linear increase of the number-average molecular weight (M_n) versus monomer conversion was observed for these systems. Among the two initiation systems, ethyl 2-bromoisobutyrate gave the fastest polymerization rate. A system with Fe³⁺ added at the beginning of the polymerization was examined and the lowest polydispersity (M_w/M_n∼1.2) was found when 10% Fe³⁺, relative to Fe²⁺ was added.