New Cobalt-Mediated Radical Polymerization (CMRP) of Methyl Methacrylate Initiated by Two Single-Component Dinuclear β-Diketone Cobalt (II) Catalysts

Abstract

Two dinuclear cobalt complexes based on bis-diketonate ligands (ligand 1: 3,3′-(1,3-phenylene)bis(1-phenylpropane-1,3-dione); ligand 2: 3,3′-(1,4-phenylene)bis(1-phenylpropane-1,3-dione)) were successfully synthesized. The two neutral catalysts all showed satisfactory activities in the cobalt-mediated radical polymerization (CMRP) of methyl methacrylate (MMA) with the common initiator of azodiisobutyronitrile (AIBN). The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities. Mono- or dicomponent low polydispersity polymers could be obtained by using the two dinuclear catalysts under proper reaction conditions. All these improvements facilitate the implementation of the acrylate CMRP and open the door to the scale-up of the syntheses and applications of the multicomponent low polydispersity polymers.

Cobalt complex bearing β‐ketoamine ligand: syntheses, structure, catalytic behavior for styrene and methyl methacrylate polymerization

“…, and the crystallographic data and refinement parameters for the cobalt complex are presented in Table . Similar structure of ligands and complexes has been reported in our previous work . The four‐coordinate environment in which the two L ligands act as monoanionic bidentate N,O chelators and lie in the trans conformation creates two stable delocalized six‐membered chelating rings (CoOCCCN).…”

“…The PDI is very low (1.46 ≤ M w / M n ≤ 1.57) for all polymerizations. In many other controlled radical processes the PDI increases with monomer conversion, as a result of irreversible termination reactions and possible transfer reactions to monomer or polymer . Interestingly, here, a slight but significant decrease in PDI with monomer conversion increases is observed.…”

“…In the 1 H NMR spectra of PMMA, the peaks at δ = ~0.6–1.0 ppm correspond to ―CH 3 , and those between δ = ~1.3 and 2.0 ppm correspond to ―CH 2 . It has been reported that PMMA exhibits a band at δ = 2.8–3.6 ppm that corresponds to the methoxy ester linkage …”