Precise Syntheses of Alternating Cyclocopolymers via Radical Copolymerizations of Divinyl Ether with <i>N</i>‑Substituted Maleimides

Alternating cyclocopolymers having a condensed ring structure were synthesized via radical copolymerization of the divinyl ether (DVE) carrying a gem-dimethyl group on the spacer with N-substituted maleimides (MIs). The consumption behaviors of the C=C bonds in both monomers and the values of the pseudo-monomer reactivity ratios close to zero supported the alternating propagation in the order of one of the DVE double bonds, MI, another double bond of DVE, and MI, to afford the topologically unique copolymers. The cyclocopolymerization was controlled via the RAFT process, and thus, one-pot synthesis of the multiblock alternating cyclocopolymer carrying different pendant groups on the MI units was achieved via sequential addition of MIs. The series of alternating cyclocopolymers exhibited high thermal stabilities and high glass temperatures (Tgs). In particular, Tg of the N-ethyl MI-based cyclocopolymer was much higher than the predicted value by the Fox equation, which was presumably derived from the rigid backbone including the condensed ring structure

Design of <i>sec</i>-Benzyl Vinyl Ethers toward the Synthesis of Alternating Copolymers Composed of Vinyl Alcohol and Vinyl Ether Units

In this work, we designed benzyl vinyl ethers carrying alkyl substituents at the benzyl position (i.e., sec-BnVEs) as bulky, reactive, and transformable monomers to realize the alternating cationic copolymerization with an alkyl vinyl ether (VE). In particular, the isopropyl substitution caused not only the bulkiness to suppress the successive propagation but also an enhancement of the vinyl group reactivity to promote crossover propagation with a less bulky VE comonomer. The isopropyl-substituted BnVE (iPr-BnVE) underwent living cationic alternating copolymerization with n-butyl VE (nBVE), and the alternating propagation was strongly suggested by the reactivity ratios. The subsequent deprotection of the sec-benzyl pendant afforded the vinyl alcohol (VA)–nBVE alternating copolymer, and the corresponding statistical copolymer was also synthesized by using the nonsubstituted monomer (BnVE) instead of iPr-BnVE. The alternating copolymer exhibited a higher glass transition temperature, which likely stems from the uniform and efficient hydrogen-bonding formation due to the periodic sequence

Radical Cyclocopolymerization of a Transformable Divinyl Monomer with a Monovinyl Monomer and Postpolymerization Modification for the Synthesis of AAB-Type Alternating Copolymers Composed of NIPAM and Vinyl Ether

In this work, we successfully synthesized AAB sequence-controlled copolymers of acrylamide (A) and vinyl ether (VE, B) via radical cyclocopolymerization of a diacrylate monomer carrying CF3-disubstututed 2-(hydroxymethyl)­phenol as the spacer (1) with an excess of VE and subsequent postpolymerization modification with aminolysis. The rational spacer design introducing two CF3–substituents allowed an efficient cyclopropagation of the divinyl monomer, alternating copolymerization with VE, and quantitative transformation. The copolymerization with 2-methoxyethyl vinyl ether (MOVE) and an aminolysis reaction with isopropylamine gave the NIPAM–NIPAM–MOVE alternating copolymer, and the aqueous solution was transparent at ambient temperature but turned cloudy upon heating. The thermal response behaviors as well as the AAB periodic sequence were evaluated through comparison with AB alternating/statistical copolymers and an N-isopropylacrylamide (NIPAM) homopolymer by temperature-variable transmittance, 1H nuclear magnetic resonance (NMR) (in D2O) measurements, and 13C/1H–13C heteronuclear single quantum coherence (HSQC) NMR spectra

Backbone-Degradable Polymers via Radical Copolymerizations of Pentafluorophenyl Methacrylate with Cyclic Ketene Acetal: Pendant Modification and Efficient Degradation by Alternating-Rich Sequence

This work deals with syntheses of backbone-degradable polymers via the radical copolymerization of pentafluorophenyl methacrylate (PFMA) with 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), which undergoes ring-opening propagation to afford an ester-bonded backbone. The combination of the electron-deficient methacrylate with the electron-rich cyclic monomer allowed high crossover copolymerization, and the electronic effect was clarified by the comparison with the copolymerization of methyl methacrylate (MMA) and BMDO. The PFMA units of the resultant copolymer underwent quantitative alcoholysis or aminolysis transformation into methacrylate or methacrylamide units along with the pendant functionalization. The alternating-rich sequence was achieved by feeding an excess ratio of BMDO, which was supported by MALDI-TOF-MS of the copolymer obtained by the RAFT copolymerization. The methanolysis-transformed copolymer carrying MMA units was decomposed under basic condition, and the degradation efficiency was superior to that of the copolymer obtained via radical copolymerization of MMA with BMDO because of the alternating-rich sequence

Ferrocene Cocatalysis in Metal-Catalyzed Living Radical Polymerization: Concerted Redox for Highly Active Catalysis

Ferrocene (FeCp2), despite its high stability, was found, for the first time, to cocatalyze living radical polymerization in concert with a ruthenium main catalyst (RuII) that is directly responsible for generating growing radicals. FeCp2 turned out to promote the following key reactions: regeneration of RuII through a reduction of XRuIII (FeIICp2 + XRuIII → FeIIICp2+X– + RuII; X: halogen); halogen-capping reaction, or regeneration of dormant species ∼∼∼C–X, by the resultant trivalent ferrocenium cation FeIIICp2+ (∼∼∼C• + FeIIICp2+X– → ∼∼∼C–X + FeIICp2). The cocatalysis was further improved by the addition of n-Bu4NCl to allow a dramatic decrease in the initial RuII concentration without any loss of the high controllability. For example, in conjunction with FeCp2/n-Bu4NCl, only 50 ppm (for monomer) of RuII can catalyze living radical polymerization to give controlled polymers with high molecular weights and narrow molecular weight distributions (Mn ∼ 1.0 × 105; Mw/Mn ∼ 1.3). Such a concerted catalysis with ferrocene would open the door to practical applications of living radical polymerization

Correction to “Elucidating Monomer Character of an Alkenyl Boronate through Radical Copolymerization Leads to Copolymer Synthesis beyond the Limitation of Copolymerizability by Side-Chain Replacement”

Correction to “Elucidating Monomer Character of an Alkenyl Boronate through Radical Copolymerization Leads to Copolymer Synthesis beyond the Limitation of Copolymerizability by Side-Chain Replacement

Template-Assisted Selective Radical Addition toward Sequence-Regulated Polymerization: Lariat Capture of Target Monomer by Template Initiator

Surprisingly high monomer selectivity was demonstrated in competitive radical addition with two kinds of methacrylates carrying sodium and ammonium cation. Crucial is size-specific recognition by a lariat crown ether embedded close to the reactive halide in a designer template initiator. Especially, a combination with an active ruthenium catalyst led to outstanding selectivity at low temperature. This template system will open the way to unprecedented sequence-regulated polymerization

Halogen Donors in Metal-Catalyzed Living Radical Polymerization: Control of the Equilibrium between Dormant and Active Species

Halogen Donors in Metal-Catalyzed Living Radical Polymerization:  Control of the Equilibrium between Dormant and Active Specie

Terminal Umpolung in Metal-Catalyzed Living Radical Polymerization: Quantitative End-Capping of Carbon−Halogen Bond via a Modifier Monomer

Terminal Umpolung in Metal-Catalyzed Living Radical Polymerization: Quantitative End-Capping of Carbon−Halogen Bond via a Modifier Monome