Metal-free atom transfer radical polymerization (ATRP) was successfully achieved in aqueous media for the first time. Polymerization of poly(ethylene oxide) methyl ether acrylate (PEGA 480 ) was well controlled (Đ < 1.40) under visible light irradiation using tetrabromofluorescein (Eosin Y) as catalyst and pentamethyldiethylenetriamine (PMDETA) as electron donor. A validated kinetic model was developed to investigate the process of photoredox catalytic cycle via reductive quenching pathway. Experimental and simulation results showed that electron donor not only had an important influence on the ATRP activation, but also participated in the ATRP deactivation. Furthermore, the effects of water content, catalyst concentration, and degree of polymerization on the polymerization were studied thoroughly by a series of experiments. Good controllability of the polymerization regulated by light on and off confirmed the high degree of temporal control. The livingness of the chains was proved by a successful chain extension experiment. Both experimental and simulation techniques were used to study aqueous metal-free ATRP, which provided a promising method to synthesize polymers in the absence of metal and organic solvent.

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A low-ppm-level iron (Fe)-based photoinduced atom-transfer-radical polymerization (ATRP) under visible-light irradiation was developed. Various ligands, tris(4-methoxyphenyl)phosphine (TMPP), 4,4′-dinonyl-2,2′-dipyridyl (dNbpy), and tris[2-(dimethylamino)ethyl]amine (Me 6 TREN), were used to enhance the catalytic activity of Fe complexes. Activator Fe II complexes were formed by the reduction of Fe III complexes with a monomer under visible-light irradiation. Linear semilogarithmic plots and low polydispersities (M w /M n < 1.4) were achieved, indicating that low-ppm-level Fe-based photoinduced ATRP was well-controlled. The effect of the catalyst concentration on polymerization was evaluated. A reduction of catalyst loadings resulted in increased polymerization rate and molecular weight. The order of Fe complex activity for the ligand was TMPP > dNbpy > Me 6 TREN. Additionally, this polymerization could be ceased and restarted, responding to light off and light on. Retention of the chain-end functionality was analyzed by 1 H NMR and chainextension experiments. Results showed that the partial chain-end functionality of the resulting polymers was lost. Thus, there is still room for improvement of the chain-end functionality and initiation efficiency of the resulting polymers.

Controlled radical polymerization (CRP) under external field has been an attractive research area in these years. In this work, a new electron transfer mechanism, that is, sonochemically induced electron transfer (SET) was introduced to mediate polymerization for the first time. The activator Cu I X/L complex was (re)generated from Cu II X 2 /L in dimethylsulfoxide (DMSO) by the SET process in the presence of free ligand tris (2-dimethylaminoethyl)amine (Me 6 TREN). The investigation of polymerization including the mechanistic insights and effect of experimental conditions on the rate of reaction has been undertaken. Kinetics of Cu(II)-catalyzed CRPs via SET under different conditions (i.e., Me 6 TREN concentration, catalyst loading, targeted degree of polymerization, and sonication power) were conducted in an unprecedentedly controlled manner, yielding polymers with predetermined molar masses and low dispersities (Đ < 1.12). Attractively, the polymerization can be performed without the piezoelectric nanoparticles and exogenous reducing agent. Contamination by nonliving chains formed from sonochemically generated radicals is avoided as well. All of these results supported that Cu(II)-based catalyst activation enabled by ultrasonication has a promising potential in scale-up of CRP.

To control over molecular weight and its distribution in bulk controlled radical polymerization (CRP) at high conversion remains a challenge. Currently, there are few reports about bulk CRP regulated by external field. In this work, a new strategy combining external fields of light and ultrasound, namely double‐external‐field, is reported to overcome the challenge. Light irradiation directly reduces the deactivator CuIIBr2/L in the presence of free amine ligand, while ultrasonic agitation improves the homogeneity of the system and moderates the diffusional limitations on activation‐deactivation and termination processes. Bulk polymerizations of methyl acrylate (MA) were conducted in a controlled manner at conversion over 90%, producing PMA with low dispersities (Đ = 1.05–1.07) and good retention of chain‐end functionality (77%). In addition, good control over the polymerizations for methyl methacrylate (MMA) and styrene was obtained, although the chain‐end functionality of PMMA‐Br requires further improvement. It is believed that this as‐developed double‐external‐field regulation strategy is also applicable to other light induced bulk RDRP systems to improve the controllability.