Fenton‐Chemistry‐Mediated Radical Polymerization

Abstract

have been developed for the synthesis of polymers with diverse structures (linear, star, cyclic, etc.), compositions ( • mopolymer, gradient, alternating, block, etc.), and functionalities (thiol, amine, etc.). [11] The main mechanism of RDRP which results in controllable polymerization is the establishment of a dynamic equilibrium between the propagating radicals (active polymers) and the dormant species via a reversible activation-deactivation process with rate constants k act. and k deact. , respectively. [7,12] With the emergence of RDRP methods such as atom transfer radical polymerization (ATRP), [13][14][15] nitroxide-mediated polymerization (NMP), [16] and reversible addition-fragmentation transfer (RAFT) [11,17,18] there has been significant effort to control these techniques via different physical and chemical stimuli. [19][20][21][22][23][24][25][26][27] Of these, RAFT holds particular promise due to its compatibility with a diverse range of solvents, monomers, and operating conditions. [11,24,[28][29][30][31][32][33][34][35] Among RDRP methods, one might argue that RAFT is the most similar to traditional FRP, with the simple addition of a thiocarbonylthio-containing compound chain transfer agent (CTA, termed as RAFT agent) [36] that can mediate the polymerization, allowing the synthesis of well-defined polymers (Scheme 1). In fact, RAFT CTAs aid in achieving control of the radical polymerization via reversible addition of the thiocarbonylthio group and rapid fragmentation reactions. [37,38] Therefore, relatively analogous activation/initiation systems such as thermal, [4,11,[28][29][30][31][39][40][41] photo, [2,24,[32][33][34][42][43][44][45][46][47][48][49] enzyme, [5,23,[50][51][52][53][54] and redox [3,[55][56][57][58][59] based radical formation can be employed to initiate both FRP and RAFT processes. Despite the huge advances made in this field, new techniques that can overcome some of the drawbacks of these systems are continuously sought. For example, using a thermal initiator requires a high operating temperature, limiting the possibility for in situ FRP/RAFT methods in biological systems, where temperature control is limited. The rate of visible light-activated RAFT polymerization without using photocatalysts is relatively slow, [34,60] while photocatalysts, e.g. iridium and rutheniumbased ones, [24,61] employed in photo-activated processes are expensive. Moreover, photo-mediated polymerization faces difficulties in terms of the equipment requisite to perform photoinitiation at scale. [29] Redox-responsive polymerization systems have many advantages, including a low activation energy (40-85 kJ mol −1 ), easy and facile control over the polymerization at ambient temperatures, very short induction periods, etc. [56,62] Polymerizations initiated by a redox reaction between an oxidizing and a reducing agent are referred to as "redox polymerizations." [63] Use of Radical PolymerizationIn this review, the power of a classical chemical reaction, the Fenton reaction for initiating radical polymeriza...

The corona of a surface bubble promotes electrochemical reactions

“…We, therefore, postulated that, due to mutual destabilization of hydroxide ions by electrostatic repulsion, the one-electron oxidation of hydroxides to hydroxyls could be significantly facilitated around bubbles adhering to an electrified support. The oxidizing power of hydroxyls (HO • + e – ⇌ OH – , E 0 = +1.90 V vs. SHE) 13 could then be harvested to trigger redox chemistry 14 , 15 .…”

Polymerizations by RAFT: Developments of the Technique and Its Application in the Synthesis of Tailored (Co)polymers

“…Almost identical polymers in terms of molecular weights, dispersities, and chain‐end functionality are achieved when polymerizations are conducted in presence or absence of oxygen. [ 36,37 ]…”

“…looked into using the well‐known Fenton chemistry. [ 37 ] Described in 1894 for the first time by Fenton, the oxidation reaction of malic acid by hydrogen peroxide in the presence of ferrous ions was described where hydroxyl radicals had the role of oxidants. In 1946, Baxendale and co‐workers used the radicals produced through the Fenton reaction for free radical polymerization of vinyl monomers.…”

Oxygen tolerant RAFT polymerisation initiated by living bacteria

“…Accordingly, in this study, we present a new oxygen tolerant bacteria-initiated RAFT polymerization, by utilizing an adapted Fenton polymerisation. 27,28 Ourapproach harnesses the substantially faster reaction rate (4-5 orders of magnitude) between hydrogen peroxide and Fe 2+ than with Fe 3+ to produce hydroxyl radicals to mediate the RAFT process. While a typical Fenton polymerization procedure directly implements Fe 2+ to avoid this, we postulated that we could use the Fe 3+ reducing capabilities of C. metallidurans CH34 metabolism, which instructs the in situ formation of Fe 2+ , and accelerate the formation of hydroxyl radicals to initiate the RAFT process.…”