Photochemically Induced ATRP of (Meth)Acrylates in the Presence of Air: The Effect of Light Intensity, Ligand, and Oxygen Concentration

Abstract

and reducing agent" ATRP. [4] It was also demonstrated that these systems are tolerant to molecular oxygen. [5] The limitation of all above mentioned ATRP variations working with ppm amounts of catalyst is that additional chemicals, used as reducing agents or radical precursors, and usually also quite expensive ligands, have to be added commonly at least tenfold excess related to catalyst. These chemicals and/or their oxidation products can participate in side reactions, even though the extent of the side reactions is significantly lower than that in "normal" ATRP.A photoATRP system, in which the copper(II) catalyst was reduced by light without necessity of using additional reducing agent, was reported for the first time by Yagci and co-workers. [6] In that work, however, equimolar amount of catalyst to initiator was used. In order to diminish the catalyst amount and at the same time to avoid using chemicals as reducing agents, our group reported for the first time a photoATRP system using Well-defined poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) are prepared via photochemically induced atom transfer radical polymerization (photoATRP) using ppm amounts of CuBr 2 /tris(2-pyridylmethyl)amine and CuBr 2 /tris[2-(dimethylamino)ethyl]amine catalyst complexes, respectively, without degassing of polymerization mixture and with no need to introduce an external reducing agent to the system. The effect of ligand to CuBr 2 ratio on kinetic and induction period during the polymerization of MMA and MA is investigated. The induction period is influenced also by the amount of oxygen in the polymerization system. Both the kinetics of MA polymerization and the induction period are affected by light intensity. Finally, the high livingness and initiation efficiency of the photoATRP system in the presence of air are proved by chain extension polymerizations. The presented system is valuable from an industrial point of view, since after optimization, well-defined and high-molarmass poly(meth)acrylates can be prepared without the necessity of degassing the system, while the polymerization can be proceeded quickly and without an induction period.

Ultra-low volume oxygen tolerant photoinduced Cu-RDRP

“…39 However, examples of oxygen tolerant photoinduced ATRP are very limited. 33,[48][49][50][51] To the best of our knowledge, there is no report on the use of any copper-mediated controlled radical polymerization method to afford the controlled synthesis of polymeric materials at very low volumes. This is a significant oversight given the high efficiency of Cu-RDRP to synthesize a wide range of complex polymeric materials with controlled functionality, dispersity and architecture (e.g.…”

Unravelling an oxygen-mediated reductive quenching pathway for photopolymerisation under long wavelengths

“…P hotoredox catalysis has proven to be a powerful strategy in organic transformations 1 and macromolecular syntheses [2][3][4][5][6][7][8][9] , especially for reversible-deactivation radical polymerisation (RDRP) [10][11][12] . In a photo-RDRP system 5,8,[12][13][14][15] , a specific quenching pathway describes how the photoexcitation energy is converted to chemically activate the polymerisation through a series of single electron transfer (SET) or energy transfer reactions.…”

Photocontrolled Living Polymerization Systems with Reversible Deactivations through Electron and Energy Transfer

“…[26a,32] In addition, by using excess TPMA relative to CuBr 2 (fourfold excess), oxygen tolerance was made possible to promote polymerization with no addition of reducing agents. Upon irradiation, the excess ligand was believed to be oxidized by CuBr 2 through single‐electron transfer (SET) to form a cation radical ligand that then reacted with molecular oxygen . As complete quenching of oxygen is needed before commencement of polymerization, a long inhibition period was observed.…”