Rational Design of Photocatalysts for Controlled Polymerization: Effect of Structures on Photocatalytic Activities

Abstract

Over the past decade, the use of photocatalysts (PCs) in controlled polymerization has brought new opportunities in sophisticated macromolecular synthesis. However, the selection of PCs in these systems has been typically based on laborious trialand-error strategies. To tackle this limitation, computer-guided rational design of PCs based on knowledge of structure-property-performance relationships has emerged. These rational strategies provide rapid and economic methodologies for tuning the performance and functionality of a polymerization system, thus providing further opportunities for polymer science. This review provides an overview of PCs employed in photocontrolled polymerization systems and summarizes their progression from early systems to the current state-of-the-art. Background theories on electronic transitions are also introduced to establish the structure-property-performance relationships from a perspective of quantum chemistry. Typical examples for each type of structure-property relationships are then presented to enlighten future design of PCs for photocontrolled polymerization. CONTENTS Glossary 5512 References 5513

Open-air green-light-driven ATRP enabled by dual photoredox/copper catalysis

“…66 In the PET-RAFT, an excited PC can transfer energy/electrons to a chain transfer agent (CTA), generating propagating radicals. [67][68][69] As in the conventional RAFT process, control over polymerization is provided by a CTA via a degenerative chain transfer mechanism. 3 PET-RAFT can be used to polymerize a wide range of monomers, is oxygen tolerant, and exhibits perfect temporal control.…”

Atom Transfer Radical Polymerization: A Mechanistic Perspective

“…The reduction potentials of PC •+ /PC species range between 0 and 0.8 V vs SCE. For moderately oxidizing organophotocatalysts, the deactivation reaction likely proceeds through a bimolecular concerted mechanism via the formation of the PC •+ /X – ion-pair deactivator (Scheme a). , This pathway is much less favorable for Cl – ions due to the much weaker interactions with radical cations and the higher tendency to undergo side reactions (e.g., H atom abstraction by Cl • ). , Within this range of oxidation potentials, more oxidizing PC •+ provided faster deactivation. The strength of ion-pairing in PC •+ /Br – is affected by the solvent nature with ethyl acetate and THF enhancing the association more than dimethylacetamide. , The solvent nature also impacts the quantum yield of intersystem crossing and the lifetime of the excited state activator …”

A Water‐Soluble Organic Photocatalyst Discovered for Highly Efficient Additive‐Free Visible‐Light‐Driven Grafting of Polymers from Proteins at Ambient and Aqueous Environments

“…To achieve this, water-soluble and weakly electron-donating sulfonate moiety was introduced in one of four donor groups of "4DP-IPN" with a strongly twisted donor-acceptor structure that has been known for highly efficient organic PC for various organic reactions and poly merizations. [43][44][45][46][47][48][49][50][51] Most excitingly, the discovered PC exhibited unique "oxygen-acceleration" behavior in PET-RAFT polymerizations of a variety of acrylates and acrylamides in both DMSO and aqueous conditions without any additives, which is apparently distinct from previously reported systems. [30,31] Combined experimental and theoretical studies suggested that molecular oxygen acts as an electron shuttle to catalyze the electron transfer between the PC in the excited state and the chain-transfer agent (CTA) (Figure 1d).…”