Effect of ferrocene moieties on the copper-based atom transfer radical polymerization of methyl methacrylate

The atom transfer radical polymerization (ATRP) of methyl methacrylate catalyzed by copper-tripodal complexes with ferrocene moieties (CuX/TRENFclmine, where X is Br or Cl, and TRENFcImine is tris-[2-(ferrocenylmethyleneimino) ethyl]amine) was investigated to understand the effect of redox active moieties on the performance of ATRP catalysts. The Cu.Br/TRENFcImin.e system was highly active, with 82% conversion in 2 h. However, the polymerization became slower at higher molar ratios of monomer to catalyst. The polydispersity index was broad, and the initiation efficiency was relatively low. On the basis of the conformational analysis, the highly active and less controlled polymerization was probably caused by the electronic effect rather than the steric effect on the ferrocene moieties, which led to the higher and lower values in the activation and deactivation steps, respectively. The polydispersity index was improved by the addition of CuBr₂, but this led to slower rates of polymerization. The effect of halide groups on ATRP caused a faster rate in the CuBr/TRENFcImine polymerization system than in the CuCl/TRENFcImine system. The higher molar ratio of monomer to catalyst had no significant effect on the CuCl/ TRENFcImine system. Nonetheless, the trace of water in the CuCl ₂.2H₂O system accelerated the rate of propagation, which led to a higher molecular weight.