Cationic Vinyl-Addition Research Articles

Copolymerizability Evaluation in Cationic Vinyl-Addition and Ring-Opening Copolymerization of Vinyl Ethers and Oxiranes: Effects of Bulkiness and the Number of Substituents Introduced into Oxiranes

Copolymerizability Evaluation in Cationic Vinyl-Addition and Ring-Opening Copolymerization of Vinyl Ethers and Oxiranes: Effects of Bulkiness and the Number of Substituents Introduced into Oxiranes

Design of Graft Architectures via Simultaneous Kinetic Control of Cationic Vinyl-Addition Polymerization of Vinyl Ethers, Coordination Ring-Opening Polymerization of Cyclic Esters, and Merging at the Propagating Chain End

Versatile graft architectures were synthesized in one shot via simultaneous controlled cationic vinyl-addition polymerization of vinyl ethers (VEs) and coordination ring-opening polymerization of cyclic esters (CEs). Graft copolymers were generated via independent propagation reactions and transient incorporation of a poly(CE) chain into the side chain of the poly(VE) propagating end via the exchange of alkoxy groups. In this mechanism, the grafting density and grafting length of a copolymer were designable by tuning the rates of each propagation reaction and the exchange reaction. As a result of a systematic investigation, the effects of polymerization conditions, such as the kinds and concentrations of monomers and catalysts, on the rate of each reaction were revealed and a design principle of various graft architectures was established. Notably, a copolymer with a remarkably high grafting density was obtained [max. 88% of poly(VE) side chains were substituted with poly(CE) chains] when a VE with an ethylenedioxy side chain was used with a titanium catalyst. The specific interaction of an ethylenedioxy unit and a titanium catalyst was key to the high grafting density.

ABC Pseudo-Periodic Sequence Control by Cationic Orthogonal Terpolymerization of Vinyl Ether, Oxirane, and Ketone

For the purpose of achieving ABC-type periodic terpolymers, various vinyl ethers (VEs), oxiranes, and ketones were examined in the cationic vinyl-addition, ring-opening, and carbonyl-addition terpo...

Generation of “Living” Species Using Perfluoroalkylsulfonic Acids in Concurrent Cationic Vinyl-Addition and Ring-Opening Copolymerization via Crossover Reactions

“Living” species-mediated propagation reactions were demonstrated to occur in the cationic vinyl-addition and ring-opening copolymerization of isopropyl vinyl ether and isobutylene oxide (IBO) with CF3SO3H (TfOH) as an initiator. The polymerization proceeded by the carbocations as propagating species formed by the dissociation of a terminal covalent carbon–OTf bond. Importantly, the covalent species were generated exclusively at the IBO-derived propagating end, which was indicated by both the incorporation of a quencher fragment into the ω-end of the product copolymer and 19F NMR analysis of the copolymerization reaction. The generation of reversibly dissociable covalent species, or “dormant” species, from one of the two monomers was crucial for allowing the even propagation of the propagating chains. Moreover, the reaction conditions were optimized to suppress side reactions such as chain transfer via β-proton elimination. Copolymers with molecular weights that agree relatively well with the theoretical values were produced using C4F9SO3H as an initiator in less polar solvents at lower temperature.

The influence of the substituents of oxiranes on copolymerization with vinyl ethers via concurrent cationic vinyl-addition and ring-opening mechanisms

The effects of oxirane substituents on the cationic copolymerization with vinyl ethers are discussed in terms of the reactivities of monomers and propagating species.

Concurrent Cationic Vinyl-Addition and Coordination Ring-Opening Copolymerization via Orthogonal Propagation and Transient Merging at the Propagating Chain End.

Controlled cationic vinyl-addition polymerization of an alkyl vinyl ether (VE) and ring-opening polymerization of ε-caprolactone (CL) simultaneously proceeded using HfCl4/Hf(OBu)4 as a dual-role catalyst for both mechanisms, yielding a graft copolymer consisting of a poly(VE) main chain and several poly(CL) side chains. The copolymer of conventionally incompatible monomers was generated via the unprecedented mechanisms consisting of orthogonal propagating reactions and transient merging. Specifically, the poly(CL) chains were incorporated into a poly(VE) chain through an exchange reaction between the VE-derived alkoxy group and the propagating poly(CL) chain at the acetal moiety of the propagating end of the poly(VE) chain. An appropriate ratio of HfCl4 and Hf(OBu)4 was indispensable for both the simultaneous vinyl-addition and ring-opening polymerizations and the alkoxy group exchange reaction.

Concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers and oxiranes

Our recent results in the concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers (VEs) and oxiranes are summarized with particular emphasis on the strategies required to generate crossover reactions between different types of monomers. Most importantly, carbocation generation via the ring-opening reaction of the oxonium ion is indispensable for the crossover reaction from oxirane to VE. This article also summarizes concurrent cationic vinyl-addition, ring-opening and carbonyl-addition terpolymerization, the copolymerization using an alkoxyoxirane through the alkoxy group transfer mechanism and the long-lived species-mediated polymerization using cyclic formals.

ビニル付加・開環同時カチオン共重合：ビニルエーテルとオキシラン間の交差生長反応を伴う共重合系の開発

ビニル付加・開環同時カチオン共重合：ビニルエーテルとオキシラン間の交差生長反応を伴う共重合系の開発

Frequency control of crossover reactions in concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers and oxiranes: specific roles of weak Lewis bases and solvent polarity

Weak Lewis bases and solvent polarity affected the frequency of the crossover reactions in the concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers and oxiranes.

Rational Design of Oxirane Monomers for Efficient Crossover Reactions in Concurrent Cationic Vinyl-Addition and Ring-Opening Copolymerization with Vinyl Ethers

Rational structural design of oxirane monomers is demonstrated here to be highly conducive to crossover reactions in the concurrent cationic vinyl-addition and ring-opening copolymerization of alkyl vinyl ethers and oxiranes. The key to the efficient crossover reactions was the smooth transformation of the once-formed oxirane-derived oxonium ion into the ring-opened carbocation, which then reacted with a vinyl monomer. For example, oxiranes that form resonance-stabilized, allyl-type carbocations (i.e., isoprene monoxide and butadiene monoxide) were polymerized through efficient crossover reactions in copolymerization with isopropyl vinyl ether, yielding copolymers composed of relatively short monomer sequences. In particular, the copolymerization of isoprene monoxide and isopropyl vinyl ether generated random or alternating-rich copolymers. The reaction using an oxirane that forms tertiary carbocations (isobutylene oxide) also proceeded via crossover reactions; however, the crossover frequency was lower, which resulted in a multiblock-like copolymer. In contrast to the three oxiranes that yielded copolymers, oxiranes that possibly result in secondary carbocations from their ring-opening (3,3-dimethyl-1,2-butylene oxide and 1,2-butylene oxide) hardly induced crossover reactions. In addition to the ease of carbocation generation via ring-opening, the nucleophilicity of the monomer and the reactivity of the oxirane-derived carbocations were shown to substantially affect the copolymerization behavior. These factors are discussed on the basis of the monomer reactivity ratios that were determined for the copolymerization systems using vinyl ethers with different reactivities, i.e., isopropyl vinyl ether or ethyl vinyl ether, toward oxiranes.

Concurrent Cationic Vinyl-Addition and Ring-Opening Copolymerization Using B(C6F5)3 as a Catalyst: Copolymerization of Vinyl Ethers and Isobutylene Oxide via Crossover Propagation Reactions

Alkyl vinyl ethers and isobutylene oxide were concurrently copolymerized through cationic vinyl addition and ring opening using B(C6F5)3 as a catalyst. NMR analyses and acid hydrolysis of the products demonstrated that the copolymerization successfully proceeded through crossover reactions between vinyl and cyclic monomers to yield multiblock-like copolymers. Appropriate catalyst and monomer combinations with suitable reactivities were key for copolymerization.