Copper‐Mediated Polymerization without External Deoxygenation or Oxygen Scavengers

Abstract

As a method for overcoming the challenge of rigorous deoxygenation in copper‐mediated controlled radical polymerization processes [e.g., atom‐transfer radical polymerization (ATRP)], reported here is a simple Cu0‐RDRP (RDRP=reversible deactivation radical polymerization) system in the absence of external additives (e.g., reducing agents, enzymes etc.). By simply adjusting the headspace of the reaction vessel, a wide range of monomers, namely acrylates, methacrylates, acrylamides, and styrene, can be polymerized in a controlled manner to yield polymers with low dispersities, near‐quantitative conversions, and high end‐group fidelity. Significantly, this approach is scalable (ca. 125 g), tolerant to elevated temperatures, compatible with both organic and aqueous media, and does not rely on external stimuli which may limit the monomer pool. The robustness and versatility of this methodology is further demonstrated by the applicability to other copper‐mediated techniques, including conventional ATRP and light‐mediated approaches.

An Oxygen Paradox: Catalytic Use of Oxygen in Radical Photopolymerization

“…[5] Fori nstance,t he inhibition of radical polymerizations by oxygen necessitates its removal by physical processes,such as nitrogen purging, [6] or via chemical routes such as the trapping of photosensitized singlet oxygen. [8] More sophisticated systems utilizing enzymes [9] or dye/ ascorbic acid combinations, [10] convert molecular oxygen into hydrogen peroxide,w hich may be further used for radical production. [8] More sophisticated systems utilizing enzymes [9] or dye/ ascorbic acid combinations, [10] convert molecular oxygen into hydrogen peroxide,w hich may be further used for radical production.…”

Self‐degassing SARA ATRP mediated by Na2S2O4 with no external additives

“…Previously, it was observed that the I eff values obtained for polymerizations under air were lower than the ones obtained under nitrogen atmosphere. This has also been observed by other authors when using Cu(0) as oxygen scavenger in DMSO, with results showing that initiator (EBiB) was also responsible for oxygen consumption . To better understand the behavior of the Na 2 S 2 O 4 ‐catalyzed SARA ATRP on this matter, several model experiments were conducted using a solution of MA, CuBr 2 , and Me 6 TREN in EtOH/H 2 O = 90/10 (v/v) and an optical sensor to monitor the dissolved oxygen concentration.…”

“…S1). The presence of unreacted chains, during copolymerization in the presence of air has been also observed in others studies reported in the literature . It is worth mentioning that none of the monomers added on steps 2 or 3 of chain extensions were previously degassed.…”

“…Several reducing agents have been explored for the development of oxygen‐tolerant ATRP systems, such as phenols, zerovalent metals, ascorbic acid, or tin(II) 2‐ethylhexanoate . It has been also demonstrated that the polymerization induction period required for oxygen consumption could be eliminated by decreasing the free headspace volume of the reaction vessel . Recently, a more complex bio‐inspired aqueous initiators for continuous activator regeneration (ICAR) ATRP performed in open‐air was reported, in which oxygen was continuously converted into carbon dioxide, in the presence of glucose, by glucose oxidase (GOx) catalysis .…”

Tuning Dispersity by Photoinduced Atom Transfer Radical Polymerisation: Monomodal Distributions with ppm Copper Concentration

“…Next, given the recent interest in oxygen-tolerant polymerisations, [39][40][41] we also wanted to perform an identical polymerisation in the absence of any external deoxygenation procedures while also using ppm levels of catalyst. Pleasingly, by decreasing the catalyst loading, broad and monomodal molecular weight distributions were obtained which further highlights the robustness of our approach ( Figure S11).…”