Co(acac)₂‐Mediated Radical Polymerization of Acrylonitrile: Control Over Molecular Weights and Copolymerization With Methyl Methacrylate

Abstract

The cobalt-mediated radical polymerization of acrylonitrile in DMSO using cobalt (II) acetylacetonate [Co(acac) 2 ] as mediator is studied. Both the evolution of molecular weight and conversion over time under various conditions are monitored. Molecular weights increase sharply at the beginning of the reaction and subsequently grow linearly with conversion. No branching of the polymer is observed by 13 C NMR. By a careful design of the reaction parameters, number-average molecular weights >1.2 Á 10 5 g Á mol À1 with a PDI around 2.4 together with conversions of up to 90% within 24 h are achieved. The copolymerization parameters of acrylonitrile with methyl methacrylate in DMSO at 30 8C are determined using the Kelen-Tüdõs approach giving r AN ¼ 0.33, r MMA ¼ 0.71.

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

“…30 These complexes were active for acrylate polymerisation but did not show the anticipated structure-activity relationship, leading the authors to conclude that the cobalt-carbon bond was decoupled from the ligand substituents and so inclusion of electron-withdrawing or electron-donating groups had no effect on the polymerisation behaviour. Cobalt species incorporating oxygen donors, such as bis-acetylacetonate Co(II) and related complexes, [19][20][21][22] are very efficient for the OMRP of vinyl acetate [31][32][33][34][35][36] and careful choice of reaction conditions has allowed expansion of the monomer scope to include acrylates, [37][38][39] acrylonitrile, [40][41][42][43] other vinyl ester monomers 44,45 and N-vinylpyrrolidone. 44,46 The use of mixed N,Odonor systems in cobalt-mediated OMRP is limited to reports on the β-ketoiminates, 47,48 which exert reasonable control over methyl acrylate and vinyl acetate polymerisation, and a very recent report on the highly efficient degenerative transfer OMRP of vinyl acetate and methyl acrylate mediated by cobalt (II) [N,N-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine], 49 (CoSal tBu,tBu ), which was published during the course of our study.…”

Synthesis of cobalt(II)-α-diimines complexes and their activity as mediators in organometallic mediated radical polymerization of vinyl acetate

“…CMRP of vinyl monomers in the presence of DMSO mediated by organocobalt has already been reported as a strategy to achieve better levels of control in polymerization [48][49][50][51][52]. These studies suggest that the coordination of DMSO to the Co centre exerts a trans effect to facilitate the weakening of the CACo bond in the axial plan, favoring the exchange of radicals by the reversible termination mechanism.…”

The X-ray investigation of the macro-stresses and design for its realization (laboratory practicum)

“…The main difficulty encountered in obtaining block copolymers is the poor solubility of AN in monomer and solvents, as well as the loss of functionality of the terminal groups during the synthesis.... The copolymerization of AN with methyl methacrylate in DMSO was studied using the acetylacetonate complex of divalent cobalt [Co(асас) 2 ] as a regulator [46] at 30°C, and it was found that the relative monomer activities determined by the Kelene-Tüdesh method are 0.33 and 0.71 for AN and MMA, respectively. These values differ somewhat from analogous parameters for the copolymerization of these monomers on classical radical initiators (0.15 and 1.2 for AN and MMA, respectively) [47].…”