Open AccessRadical Cations of Phenoxazine and Dihydrophenazine Photoredox Catalysts and Their Role as Deactivators in Organocatalyzed Atom Transfer Radical Polymerization
Author(s) -
Daniel A. Corbin,
Blaine G. McCarthy,
Zach van de Lindt,
Garret M. Miyake
Publication year - 2021
Publication title -
macromolecules
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.994
H-Index - 313
eISSN - 1520-5835
pISSN - 0024-9297
DOI - 10.1021/acs.macromol.1c00640
Subject(s) - chemistry , atom transfer radical polymerization , phenoxazine , cobalt mediated radical polymerization , radical polymerization , living free radical polymerization , photochemistry , radical , radical ion , polymer chemistry , nitroxide mediated radical polymerization , polymerization , photoredox catalysis , catalysis , radical initiator , polymer , organic chemistry , photocatalysis , phenothiazine , medicine , ion , pharmacology
Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, N , N -dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.