Powerful Ring-Closure Method for Preparing Varied Cyclic Polymers

Abstract

A powerful ring-closure method was developed for the formation of cyclic polymers by combining reversible addition–fragmentation chain transfer polymerization (RAFT) and light-induced Diels–Alder click reaction. The outstanding features of this novel method were demonstrated from the following four aspects. This convenient and efficient technique could produce cyclic polymers in air at room temperature without any other catalyst or stimulus requirements other than a mild UV irradiation. The universality of this method was demonstrated by successfully producing five different types of cyclic homopolymers including polystyrene, poly(methyl methacrylate), poly(tert-butyl acrylate), poly( N , N -dimethylacrylamide), and poly(2-vinylpyridine) and two kinds of block copolymers of poly(methyl methacrylate)-block-polystyrene and poly(methyl methacrylate)-block-poly(tert-butyl acrylate). This is the first time to report a one-pot ring-closure method for the formation of cyclic polymers, in which the crude monomer polymerization solution was directly diluted as precursors and no more requirements were needed to purify and postfunctionalize the linear polymer intermediates. When combing with a batchwise operation, this novel light-induced ring-closure method could significantly improve the notorious disadvantage of low cyclic polymer yield accompanied by the ring-closure strategy.

Cyclic Polymers by Ring‐Closure Strategies

“…Mechanistically,w hen the o-methylbenzaldehyde moiety is irradiated by UV light (l % 315 nm), intramolecular hydrogen abstraction followed by ab ond reorganization occurs to generate an o-quinodimethane (photoenol) intermediate. [79] Polymerization of arange of styrenic, vinylic,and acrylic monomers led to alibrary of linear precursors with well-defined molecular parameters,w hich were subsequently ring-closed upon irradiation at an appropriate wavelength to generate the diene (Scheme 21). [89] Interestingly,t his RC reaction is also characterized by quantitative recovery yields,s ince only the polymer is present in the solution.…”

A ring-closure method for preparing cyclic polymers from unconjugated vinyl monomers

“…RAFT/Diels-Alder reaction 21 , ring opening polymerization (ROP)/Diels-Alder reaction 22 , ROP/CuAAC 23 , and ROP/thiolene reaction 24 . Based on these combinations, a variety of cyclic polymers has been prepared including polystyrenics 8,10,13,15,[17][18][19]21 , polymethacrylates 11,16,21 , polyacrylates 14,21 , polyacrylamides 12,20,21 and polyesters [22][23][24] .…”

Advanced Developments in Cyclic Polymers: Synthesis, Applications, and Perspectives

“…Intramolecular [4+2] reaction of a linear α‐maleimide‐ω‐cyclopentadienyl‐functionalized polymer results in a well‐defined highly pure cyclic polymer upon heating at high dilution . The more convenient UV‐induced [4+2] cycloaddition between end groups of photoenol and dithioester has also been reported, as shown in Figure . The method combined a reversible addition–fragmentation chain transfer (RAFT) polymerization and UV‐induced Diels–Alder addition .…”