Efficient Synthesis\nof Ultrahigh Molecular Weight\nPoly(methyl methacrylate) via Visible Light-Induced RAFT Polymerization\nin Deep Eutectic Solvent

This work investigates the potential of deep eutectic\nsolvents\n(DES) to facilitate the synthesis of ultrahigh molecular weight (UHMW)\npoly(methyl methacrylate) (PMMA). Although several works have successfully\nsynthesized UHMW polymers (<i>M</i><sub>n</sub> ∼\n10<sup>6</sup> g/mol) by reversible addition–fragmentation\nchain-transfer (RAFT) polymerization, the polymerization of hydrophobic\nmonomers with low propagation rate constants, such as methyl methacrylate,\nremains challenging. In this study, we employ photoelectron/energy\ntransfer-RAFT (PET-RAFT) polymerization with dithiobenzoate-type chain-transfer\nagents (CTA) in DES. The increased propagation rate and stability\nof CTA in DES provide a polymerization rate significantly higher than\nthat in dimethyl sulfoxide. Furthermore, polymerization in DES exhibits\ntwo-stage polymerization kinetics. After the initial retardation stage\nof CTA, the polymerization rate is boosted by the gel effect, allowing\nthe synthesis of UHMW PMMA in a reasonable time. We also analyze the\neffect of the reaction temperature to achieve a high polymerization\nrate and low molecular weight dispersity. The chain entanglement of\nUHMW PMMA leads to the formation of highly elastic polymer gels in\nDES. In short, this work suggests that the intriguing polymerization\nkinetics of PET-RAFT polymerization in DES enables a rapid synthesis\nof well-defined UHMW PMMA through photoinduced RAFT polymerization.