Zero-valent Iron/RAFT Agent-Mediated Polymerization of Methyl Methacrylate at Ambient Temperature

Abstract

In this work, zero-valent iron powder (Fe(0)) was used to catalyze the polymerization of methyl methacrylate (MMA) in the presence of a reversible addition−fragmentation chain transfer (RAFT) agent, 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) without any ligand at ambient temperature. The polymerization behavior complied with the features of typical “living”/controlled radical polymerizations. The number-average molecular weights of poly(methyl methacrylate) increased linearly with monomer conversion, while maintaining narrow molecular weight distributions (Mw/Mn < 1.50). Even at low concentration of Fe(0), such as at [MMA]0:[CPDN]0:[Fe(0)]0 = 200:1:0.2, the polymerization was also controllable; however, it presented a depressed polymerization rate and a prolonged induction period (about 12 h). The polymerization rate also decreased with increasing of CPDN concentration. From experimental results, it was deduced that the initiating species were derived from the cooperative reaction of Fe(0) and CPDN, in which CPDN acted as a pseudohalide alkyl initiator. The control process was supposed to proceed via a synactic mechanism. One mechanism was the synergic mediation by Fe(0) and CPDN, in which Fe(III) formed in situ acted as an deactivator, however, this deactivation was supposed to be ineffective. The other was the RAFT mechanism with CPDN as the RAFT agent, which may dominate the whole control.