Highly efficient dual photoredox/copper catalyzed atom transfer radical polymerization achieved through mechanism-driven photocatalyst design

• Published in: Nature communications Vol. 15; no. 1; pp. 5160 - 13
• Main Authors: Jeon, Woojin, Kwon, Yonghwan, Kwon, Min Sang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17-06-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/131; 639/301/923/1028; 639/638/455/941; 639/638/455/959; Catalysis; Copper; Design; Electrode potentials; Excitation; Ground state; Humanities and Social Sciences; Molecular weight; Molecular weight distribution; multidisciplinary; Oxidation; Photocatalysts; Polymerization; Polymethyl methacrylate; Radicals; Regeneration; Science; Science (multidisciplinary); Side reactions
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-49509-1

Atom transfer radical polymerization (ATRP) with dual photoredox/copper catalysis combines the advantages of photo-ATRP and photoredox-mediated ATRP, utilizing visible light and ensuring broad monomer scope and solvent compatibility while minimizing side reactions. Despite its popularity, challenges include high photocatalyst (PC) loadings (10 to 1000 ppm), requiring additional purification and increasing costs. In this study, we discover a PC that functions at the sub-ppm level for ATRP through mechanism-driven PC design. Through studying polymerization mechanisms, we find that the efficient polymerizations are driven by PCs whose ground state oxidation potential—responsible for PC regeneration—play a more important role than their excited state reducing power, responsible for initiation. This is verified by screening PCs with varying redox potentials and triplet excited state generation capabilities. Based on these findings, we identify a highly efficient PC, 4DCDP-IPN, featuring moderate excited state reducing power and a maximized ground state oxidation potential. Employing this PC at 50 ppb, we synthesize poly(methyl methacrylate) with high conversion, narrow molecular weight distribution, and high chain-end fidelity. This system exhibits oxygen tolerance and supports large-scale reactions under ambient conditions. Our findings, driven by the systematic PC design, offer meaningful insights for controlled radical polymerizations and metallaphotoredox-mediated syntheses beyond ATRP.
Atom transfer radical polymerization with dual photoredox/copper catalysis often requires high photocatalyst loadings. Herein the authors report a photocatalyst that functions at the sub-ppm level for controlled radical polymerizations, focusing on a design strategy aimed at photocatalyst regeneration.