Visible light-induced radical polymerization of vinyl acetate mediated by organo-nickel N2O2 Schiff-base complexes

• Autor(a) principal: Pesqueira, Naralyne M. [UNESP]
• Data de Publicação: 2023
• Outros Autores: Bignardi, Camila [UNESP], Oliveira, Larissa F. [UNESP], Machado, Antonio E.H., Carvalho-Jr, Valdemiro P. [UNESP], Goi, Beatriz E. [UNESP]
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1016/j.jphotochem.2022.114443; http://hdl.handle.net/11449/246386
• topic: Copolymer; LED irradiation; Photo-OMRP; Radical polymerization

Four nickel(II) complexes with symmetrically substituted N2O2 tetradentate Schiff-base ligands, prepared from the 2:1 condensation of 3-tert-butyl-salicylaldehyde, and ethylenediamine (1), o-phenylenediamine (2), 1,2-cis,trans-cyclohexyldiamine (3), or 1,3-diaminepropane (4), were synthesized. These NiII Schiff-base complexes (1–4) were used as control agents for the polymerization of vinyl acetate (VAc) photoinitiated by diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) according to a photoinduced organometallic-mediated radical polymerization (photo-OMRP) mechanism. All complexes presented good control ability, although the polymerization mediated by 3 showed the best control over molecular weight (Mn matching Mn,th) and dispersity (Ð < 1.50). The livingness of the polymers has been confirmed by LED on and LED off experiments, the polymerization stopped immediately, and no monomer conversion was observed during the light-off period, indicating a negligible concentration of the active radical in the dark. Further, to demonstrate the living nature of this system, block copolymers of poly(vinyl acetate)-b-poly(methyl acrylate) were synthesized using the sequential visible-light-induced process. Kinetic results and computational investigations supported the activation/deactivation equilibrium exerted by complexes 1–4, which occurred on only one face of the complexes via reversible deactivation (RD) mechanism.