Screening RAFT agents and photocatalysts to mediate PET-RAFT polymerization using a high throughput approach

Abstract

We report a high throughput approach for the screening of RAFT agents and photocatalysts to mediate photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization. Ten different RAFT agents, including trithiocarbonates, dithioesters, xanthates and dithiocarbamates, were investigated to mediate PET-RAFT polymerization under aerobic conditions using green LED light (λ_max = 530 nm, 5.5 mW cm⁻²) in combination with four different porphyrins as photocatalysts. These photocatalysts possess different substituents, including carboxylic acid groups and halogen atoms. Our screening approach reveals the structure and performance relationships between the RAFT agents, metalloporphyrin photocatalysts and monomers (acrylamide, acrylate, methacrylate and methacrylamide) employed to conduct PET-RAFT polymerization. Quantum chemical calculations were also employed to elucidate the results of the polymerization kinetics. Apart from the influence of Z and R groups of the RAFT agents, free-base porphyrin catalysts also showed significant deviation in polymerization kinetics and control.