Selective Photoactivation: From a Single Unit Monomer Insertion Reaction to Controlled Polymer Architectures

• Published in: Journal of the American Chemical Society Vol. 138; no. 9; pp. 3094 - 3106
• Main Authors: Xu, Jiangtao, Shanmugam, Sivaprakash, Fu, Changkui, Aguey-Zinsou, Kondo-Francois, Boyer, Cyrille
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.03.2016
• Subjects: acrylates; catalysts; composite polymers; energy; green light; irradiation; polymerization; red light; redox reactions; zinc
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.5b12408

Here, we exploit the selectivity of photoactivation of thiocarbonylthio compounds to implement two distinct organic and polymer synthetic methodologies: (1) a single unit monomer insertion (SUMI) reaction and (2) selective, controlled radical polymerization via a visible-light-mediated photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) process. In the first method, precise single unit monomer insertion into a dithiobenzoate with a high reaction yield (>97%) is reported using an organic photoredox catalyst, pheophorbide a (PheoA), under red light irradiation (λmax = 635 nm, 0.4 mW/cm2). The exceptional selectivity of PheoA toward dithiobenzoate was utilized in combination with another catalyst, zinc tetraphenylporphine (ZnTPP), for the preparation of a complex macromolecular architecture. PheoA was first employed to selectively activate a dithiobenzoate, 4-cyanopentanoic acid dithiobenzoate, for the polymerization of a methacrylate backbone under red light irradiation. Subsequently, metalloporphyrin ZnTPP was utilized to selectively activate pendant trithiocarbonate moieties for the polymerization of acrylates under green light (λmax = 530 nm, 0.6 mW/cm2) to yield well-defined graft co-polymers.