Iron halide mediated atom transfer radical polymerization of methyl methacrylate with N-Alkyl-2-pyridylmethanimine as the ligand

The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA]0/[EBIB]0/[iron halide]0/[NHPMI]0 = 150/1/1/2 was better controlled in 2-butanone than in p-xylene at 90 °C. Initially added iron(III) halide improved the controllability of the reactions in terms of molecular weight control. The p-toluenesulfonyl chloride (TsC1)-initiated ATRP were uncontrolled with [MMA]0/[TsC1]0/[iron halide]0/[NHPMI]0 = 150/1/1/2 in 2-butanone at 90 °C. In contrast to the EBIB-initiated system, the initially added iron(III) halide greatly decreased the controllability of the TsC1-initiated ATRP. The ration of iron halide to NHPMI significantly influenced the controllability of both EBIB and TsC1-initiated ATRP systems. The ATRP with [MMA]0/[initiator]0/[iron halide]0/[NHPMI]0 = 150/1//1/2 provided polymers with PDIs 1.57, whereas those with [iron halide]0/[NHPMI]0 = 1 resulted in polymers with PDIs as low as 1.35. Moreover, polymers with PDIs of approximately 1.25 were obtained after their precipitation from acidified methanol. The high functionality of the halide end group in the obtained polymer was confirmed by both 1H NMR and a chain-extenstion reaction. Cyclic voltammetry was utilized to explain the differing catalytic behaviors of the in situ-formed complexes by iron halide and NHPMI with different molar ratios