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

Author(s)

Pesqueira, Naralyne M. ; Bignardi, Camila ; Oliveira, Larissa F. ; Machado, Antonio E. H. ; Carvalho-Jr, Valdemiro P. ; Goi, Beatriz E.

• Document type: Journal article
• Source: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY; v. 437, p. 11-pg., 2023-03-01.

Abstract

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 poly-merization (photo-OMRP) mechanism. All complexes presented good control ability, although the polymeriza-tion mediated by 3 showed the best control over molecular weight (Mn matching Mn,th) and dispersity (D < 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 deac-tivation (RD) mechanism. (AU)

• FAPESP's process: 18/19395-9 - Synthesis of new organometallic complexes of Fe (III), Co (III) and Ni (III) coordinated to asymmetric Schiff bases to mediate photo-OMRP
• Grantee: Beatriz Eleutério Goi Carvalho
• Support Opportunities: Regular Research Grants
• FAPESP's process: 21/11741-8 - Ni(II) complexes for controlled radical photopolymerization reactions (photo-OMRP and CRP2) and application in 3D printing
• Grantee: Naralyne Martins Pesqueira
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 18/06340-1 - Bimetallic complexes of ruthenium(II) and nickel(II): coupling of mechanistically-incompatible reactions using multifunctional catalysts via tandem catalysis
• Grantee: Valdemiro Pereira de Carvalho Júnior
• Support Opportunities: Regular Research Grants