Light‐Regulated Polymerization under Near‐Infrared/Far‐Red Irradiation Catalyzed by Bacteriochlorophyll a

Abstract

Photoregulated polymerizations are typically conducted using high-energy (UV and blue) light, which may lead to undesired side reactions. Furthermore, as the penetration of visible light is rather limited, the range of applications with such wavelengths is likewise limited. We herein report the first living radical polymerization that can be activated and deactivated by irradiation with near-infrared (NIR) and far-red light. Bacteriochlorophyll a (Bachl a) was employed as a photoredox catalyst for photoinduced electron transfer/reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Well-defined polymers were thus synthesized within a few hours under NIR (λ=850 nm) and far-red (λ=780 nm) irradiation with excellent control over the molecular weight (M(n)/M(w)<1.25). Taking advantage of the good penetration of NIR light, we showed that the polymerization also proceeded smoothly when a translucent barrier was placed between light source and reaction vessel.

Unraveling Photocatalytic Mechanism and Selectivity in PET‐RAFT Polymerization

“…This is usually done through complex photoredox and energy transfer processes and has offered a profound challenge to researchers [1][2][3] who tried to model this natural phenomenon. [4][5][6][7][8][9][10][11] As the name suggests, these photoredox catalysts harnesses the energy of visible light to accelerate a chemical reaction through electron transfer processes. Over the subsequent century, interest has grown in finding new systems that are capable of absorbing light and mediating chemical reactions for the production of fine chemicals and advanced materials.…”

“…[4][5][6][7][8][9][10][11] As the name suggests, these photoredox catalysts harnesses the energy of visible light to accelerate a chemical reaction through electron transfer processes. [5,[14][15][16][17][18][19][20][21][22][23] Inspired by this, Boyer and co-workers have recently utilized photoredox catalysts, [4,8,17,18] such as pheophorbide a (PheoA) and zinc tetraphenylporphine (ZnTPP), to mediate photoinduced electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization (Scheme 1). [12] The property of compatibility has led to some recent developments in the field of visible-light photocatalysis, where different catalysts are utilized to perform complex organic reactions in a single pot.…”

Investigation into the photolytic stability of RAFT agents and the implications for photopolymerization reactions

“…RDRPs act by minimizing the time the chain end spends in its 'active' (i.e. Many examples of photochemically-mediated RDRP variants have emerged, including photo-ATRP, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] photo-NMP, 30 and photo-RAFT (both photoinitiated [31][32][33][34][35][36][37][38] and photo-catalysed [39][40][41][42][43][44][45][46][47] ) with much success. 12 This can be achieved through two fundamental mechanisms: (1) the reversible activation/deactivation end-capping from a dormant to active state, and (2) a degenerative chain transfer mechanism.…”

Heteroatom‐Doped Carbon Dots (CDs) as a Class of Metal‐Free Photocatalysts for PET‐RAFT Polymerization under Visible Light and Sunlight

“…[1] Recently,t he integration of photo-mediated synthesis with reversible-deactivation radical polymerization (RDRP), including nitroxide-mediated polymerization (NMP), atom-transfer radical polymerization (ATRP), and reversible addition-fragmentation chain-transfer (RAFT) polymerization, is as ignificant advancement in this field. [3] So far, in this field, great progress has been made in the groups led by Hawker and Fors, [4] Matyjaszewski, [5] Yagci, [6] Miyake, [7] Boyer, [8][9][10] Qiao, [11] Haddleton and Anastasaki, [12] Johnson, [13,14] Boydston, [15] Egap, [16] and many others. [3] So far, in this field, great progress has been made in the groups led by Hawker and Fors, [4] Matyjaszewski, [5] Yagci, [6] Miyake, [7] Boyer, [8][9][10] Qiao, [11] Haddleton and Anastasaki, [12] Johnson, [13,14] Boydston, [15] Egap, [16] and many others.…”

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Ak ey challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts.Now carbon dots (CDs) have been exploited for the first time as metal-free photocatalysts for visible-light-regulated reversible addition-fragmentation chain-transfer (RAFT) polymerization. [3] So far, in this field, great progress has been made in the groups led by Hawker and Fors, [4] Matyjaszewski, [5] Yagci, [6] Miyake, [7] Boyer, [8][9][10] Qiao, [11] Haddleton and Anastasaki, [12] Johnson, [13,14] Boydston, [15] Egap, [16] and many others. PET-RAFT polymerization of various monomers with temporal control, narrowdispersity ( % 1.04), and chain-endfidelity was achieved.Besides,itwas demonstrated that the CD-catalyzed PET-RAFT polymerization was effectively performed under natural solar irradiation.

Inspired by the solar-driven biosynthesis of proteins with high chain end fidelity and sequence control, macromolecular research has been focused on the exploitation of light to regulate modern polymer synthesis for ab etter control over the polymerization process.

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