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

Abstract:  This study describes the synthesis and characterization of three alpha-diimine-cobalt complexes of the type [CoCl2(R-DAB)] (R-DAB = R-N=CH-CH=N-R; R = Mes, Dipp and Dipp*) and their application as mediators for the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) using 2,2′-Azobis(2-methylpropionitrile) (AIBN) as initiator. The complexes were characterised by elemental analyses, FTIR, UV-Vis, electron paramagnetic resonance spectroscopy, cyclic voltammetry, and computational methods. The systematic variation of the reaction conditions, such as [initiator]/[Co] and [monomer]/[Co] molar ratios at 65(circle)C, affected the polymerization rates and the molecular weights, reaching a certain level of control. The VAc polymerization was initiated by AIBN in the presence of DMSO using the alpha-diiminecobalt complexes as mediators with [DMSO]/[Co] = 1 at 65 C-circle. The control over the polymer produced was not improved after the addition of DMSO. Kinetics studies and computational investigations support a tailorable cobalt complex reactivity mainly altered by steric factors of the alpha-diimine ligands. (C) 2017 Elsevier B.V. All rights reserved.

Author(s): Riga, BA; Neves, MD; Machado, AEH; Araujo, DMS; Souza, JR; Nascimento, OR; Santana, VT; Cavalheiro, CCS; Carvalho, VP; Goi, BE

INORGANICA CHIMICA ACTA

DOI: 10.1016/j.ica.2017.11.041