Selective and Rapid Light‐Induced RAFT Single Unit Monomer Insertion in Aqueous Solution

Abstract

We report on the property of an added photocatalyst, specifically, Zn(II) meso-tetra(4sulfonatophenyl)porphyrin (ZnTPPS), to accelerate visible light-initiated (red, yellow, green light), single-unit-monomer-insertion (SUMI) of N,N-dimethylacrylamide into a reversible additionfragmentation chain transfer (RAFT) agent, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4cyanopentanoic acid (RAFT 1), in aqueous solution. Thus, under irradiation with red (633 nm) or yellow (593 nm) light with 50 mpm (moles per million mole of monomer) ZnTPPS at 30 °C, the rate enhancement provided by photo or energy electron transfer (PET) is ~7-fold enhancement over the rate of direct photoRAFT-SUMI (without catalyst), which corresponds to achieving full and selective This article is protected by copyright. All rights reserved. reaction in hours vs. days. Importantly, the selectivity, as judged by the absence of oligomers, is retained. Under green light at similar power, higher rates of SUMI are also observed. However, the degree of enhancement provided by PET-RAFT-SUMI over direct photoRAFT-SUMI as a function of catalyst concentration is less and some oligomers are formed.

Selective Bond Cleavage in RAFT Agents Promoted by Low‐Energy Electron Attachment

“…While DMTTC is a poor RAFT agent, it is likely to be a good SET‐RDRP initiator (methyl radical will add rapidly to monomer) and the product dormant species after some propagation (propagating radical‐TTC) should likely be a good RAFT agent. In addition, we anticipate that these results will be also relevant to initiation in photoinduced electron/energy transfer (PET‐RAFT) that involves electron transfer to the RAFT agent [32, 33] . Moreover, ionizing radiation may offer the release of low‐energy electrons and subsequent DEA in solution [34] …”

“…In addition, we anticipate that these results will be also relevant to initiation in photoinduced electron/energy transfer (PET‐RAFT) that involves electron transfer to the RAFT agent. [ 32 , 33 ] Moreover, ionizing radiation may offer the release of low‐energy electrons and subsequent DEA in solution. [34] …”

Progress and Perspectives Beyond Traditional RAFT Polymerization

“…In tandem with monomers possessing slow polymerization rates or an inability to homopolymerize, the iterative insertion of vinyl monomers can be achieved without the need for a solid support or template. [141][142][143][144][145] In work by Boyer and coworkers, a styrenic monomer was first inserted into a trithiocarbonate species under green light irradiation, whereby selective activation of the tertiary R-group, and not the secondary C-S bond of the product, ensured the absence of polymerization. Subsequently, staged irradiation of orthogonal photoredox catalysts Ir(ppy) 3 and ZnTPP under blue and red light, respectively, afforded the sequential insertion of a maleimide monomer, then vinyl acetate or limonene with great precision.…”

Selektive Bindungsspaltung in RAFT Agenzien durch niederenergetische Elektronenanlagerung

“…Während DMTTC ein schlechtes RAFT‐Mittel ist, ist es wahrscheinlich ein guter SET‐RDRP‐Initiator (das Methylradikal wird sich schnell an das Monomer addieren) und die gebildete ruhende Spezies nach einiger Vermehrung (propagierendes Radikal‐TTC) sollte wahrscheinlich ein gutes RAFT‐Mittel sein. Darüber hinaus gehen wir davon aus, dass diese Ergebnisse auch für die Initiierung beim photoinduzierten Elektronen‐/Energietransfer (PET‐RAFT) relevant sind, bei dem der Elektronentransfer zum RAFT‐Agens stattfindet [32, 33] . Darüber hinaus kann ionisierende Strahlung die Freisetzung von niederenergetischen Elektronen und damit DEA in Lösung bieten [34] …”