Aggregation-induced emission polymers via reversible-deactivation radical polymerization Special Collection:Distinguished Australian Researchers

Aggregation-induced emission(AIE)is a unique phenomenon whereby aggregation of molecules induces fluorescence emission as opposed to the more commonly known aggregation-caused quenching(ACQ).AIE has the potential to be utilized in the large-scale production of AIE-active polymeric materials because of their wide range of practical applications such as stimuli-responsive sensors,biological imaging agents,and drug delivery systems.This is evident from the increasing number of publications over the years since AIE was first discovered.In addition,the evergrowing interest in this field has led many researchers around the world to develop new and creative methods in the design of monomers,initiators and crosslinkers,with the goal of broadening the scope and utility of AIE polymers.One of the most promising approaches to the design and synthesis of AIE polymers is the use of the reversible-deactivation radical polymerization(RDRP)techniques,which enabled the production of well-controlled AIE materials that are often difficult to achieve by other methods.In this review,a summary of some recent works that utilize RDRP for AIE polymer design and synthesis is presented,including(i)the design of AIE-related monomers,initiators/crosslinkers;the achievements in preparation of AIE polymers using(ii)reversible addition–fragmentation chain transfer(RAFT)technique;(iii)atom transfer radical polymerization(ATRP)technique;(iv)other techniques such as Cu(0)-RDRP technique and nitroxide-mediated polymerization(NMP)technique;(v)the possible applications of these AIE polymers,and finally(vi)a summary/perspective and the future direction of AIE polymers.

A novel reversible-deactivation radical polymerization strategy via near-infrared light-controlled photothermal conversion dividing wall-type heat exchanger

As an effective means of utilizing light energy,photothermal conversion has excellent application in the field of polymerization.Herein,a dividing wall-type heat exchanger with the aid of photothermal conversion was designed to conduct polymerization under irradiation with near-infrared(NIR)light by utilizing the ketocyanine-type dye solution as the highly efficient activator(>83.2%photothermal conversion efficiency).Various types of reversible-deactivation radical polymerization(RDRP)methods,including reversible addition-fragmentation chain transfer,atom transfer radical polymerization,and bromine-iodine transformation RDRP,are suitable for this strategy.Well-defined polymers with excellent control over molar mass and molar mass dispersity(D<1.28)were thus synthesized within a few hours under NIR(λ_(max)=810 nm,850 nm)irradiation at room temperature.Importantly,in addition to conventional heating methods(such as electrical heating jackets),the designed dividing wall-type heat exchanger via NIR light activation has another unique advantage:it can enhance the polymerization by the synergistic effect of both heating and NIR light irradiation due to the deeper penetration of NIR light.

Persistent radical anion of perylene dianhydride:an emerging metal-free photocatalyst for near-infrared photocontrolled RAFT polymerization

Developing a new type of photocatalyst(PC) and catalytic mechanism for near-infrared(NIR) photocontrolled reversibledeactivation radical polymerization(RDRP) system is charming but challenging.Herein,a novel PC of the persistent radical anion(PRA)(possessing the properties of both radical and anion) was developed for NIR photocontrolled reversible additionfragmentation chain transfer(RAFT) polymerization,enabling successful polymerization while gaining a deep insight into the mechanism of photo-induced electron transfer RAFT(PET-RAFT) polymerization.Different from the conventional and wellaccepted reductive quenching(RQ) pathway,in which the radical anion intermediates of PCs(PCs^(·-)) must be generated in an excited state(ES),here,the PRA(3,4,9,10-perylenetetracarboxylic dianhydride radical anion(PTCDA^(·-))) could generate conveniently in situ in the ground state(GS) and subsequently serve as highly efficient PC in the NIR region(740–850 nm).The successful implementation of this strategy elucidates the peculiar role played by light and the real way of electron transfer behaviors.In fact,the transfer of a single electron from PRA to chain transfer agent(CTA) and cleavage of the C–S bonds is a process from ES to GS,rather than always from GS(PCs^(·-)) to GS(CTA) in the RQ pathway as is well known to all.In addition,the excellent spatial-temporal control and powerful penetration ability of the NIR light were also confirmed by this PRAcatalyzed polymerization system.

Molar Mass Dispersity Control by lodine-mediated Reversibledeactivation Radical Polymerization

Dispersity(D)of polymers has a great effect on the properties of polymeric materials,and therefore how to control θ is very important but still a huge challenge in polymer synthesis,especially for reversible-deactivation radical polymerization(RDRP)strategy.Herein,we successfully developed a novel strategy to adjust D of polymers by visible light-controlled reversible complexation mediated living radical polymerizatio n(RCMP)and combi nation of single-electron transfer-degenerative chain tran sfer living radical polymerization(SET-DTLRP)at room temperature.In RCMP system,2-iodo-2-methylpropionitrile(CP-I)and ethyl 2-iodo-2-phenylacetate(EIPA)were used as alkyl iodide initiators,by using methyl methacrylate(MMA)as the model monomer and n-butylacrylate(BA)as the end-capping reagent to regulate D of polymers.Subsequently,we successfully prepared the block copolymer PMMA-b-PBA with adjustable D by reactivating the polymer end-chains via SET-DTLRP in the presence of copper wire,fully dem on strati ng that it is a promising strategy that can keep the"living"feature of polymers while regulating their molar mass dispersities easily.