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

Abstract

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 terpolymerization and suitable reaction conditions were identified. When the appropriate monomers are employed, the terpolymerization proceeds via a one-way cycle of crossover reactions, similar to “rock-paper-scissors”. Homopropagation reactions of VE and oxirane need to be completely suppressed while attaining highly selective crossover reactions to achieve ABC-type periodic sequence control. By screening various monomers, VEs and oxiranes with moderate but sufficiently high reactivities were found to be appropriate for both the frequent crossover reactions and the polymerization itself. Appropriate ketones were also important for achieving efficient terpolymerization. In addition, more frequent crossover reactions occurred in the terpolymerizations conducted in less polar solvents at lower temperatures. Under the optimized conditions, the cationic terpolymerization of ethyl VE, 4-vinyl-1,2-cyclohexene oxide, and methyl ethyl ketone proceeded via frequent crossover reactions, and this process yielded an ABC pseudo-periodic terpolymer with averages of 1.2, 1.4, and 1.0 monomer units per block, respectively.

Unzipping and scrambling reaction‐induced sequence control of copolymer chains via temperature changes during cationic ring‐opening copolymerization of cyclic acetals and cyclic esters

“…In synthetic polymers, various kinds of well-defined diblock (or triblock) copolymers have been synthesized owing to the development of precision polymerization techniques and have been utilized for many applications, such as drug delivery systems, 1 thermoplastic elastomers, 2 and lithography. 3 By contrast, there are limited examples of copolymers with more complex sequences, for example, AB-, [4][5][6] ABB-, 7,8 or ABC-type [9][10][11] alternating structures, despite the potential high functionalities of these molecules. Sequenceregulated copolymers have been synthesized via several methods.…”

“…[14][15][16][17] Polymerization of monomers with specific reactivities is the most practical method, although the need for very high selectivity during the propagation reactions limits the monomers that can be used. [4][5][6][7][8][9][10][11]18,19 A new strategy and/or hybridization of existing methods are required for the synthesis of a much wider variety of sequence-regulated copolymers in a practical manner.…”

Cationic Copolymerization of o-Phthalaldehyde and Vinyl Monomers with Various Substituents on the Vinyl Group or in the Pendant: Effects of the Structure and Reactivity of Vinyl Monomers on Copolymerization Behavior

“…This result is due to the unstable ketal structure derived from the crossover reaction from the VE-derived carbocation to OPA (Scheme ). Ketal structures with cyclic moieties are known to be relatively stable compared with their acyclic counterparts; however, copolymerization of MeDHF and OPA did not proceed (entry 9). In addition, homopolymers of MPE or MeDHF were not obtained in copolymerization with OPA, although both MPE and MeDHF exhibit homopolymerizability. , This phenomenon is possibly because OPA behaved as a Lewis base and suppressed the homopropagation of MPE or MeDHF via strong interaction between the propagating carbocation and OPA.…”

Importance of Nucleophilicity of Chain-Transfer Agents for Controlled Cationic Degenerative Chain-Transfer Polymerization

“…Studies on controlled chain-growth polymerizations have strayed away from ionic-centered living polymerizations (i.e., anionic and cationic) − since the dawn of reversible-deactivation-radical polymerization methodologies that are radical-centered. − However, a resurgence in cationic-centered polymerization has recently occurred . Typically, cationic polymerization has been largely limited to electron-rich vinyl monomers such as vinyl ethers (VEs) and para -methoxystyrene ( p MOS) that are difficult to polymerize through a radical-based process. , To further expand the scope of accessible polymer compositions, recent advancements have enabled copolymerizations of these monomers with a variety of radical monomers. − Additionally, the incorporation of renewable feedstock as monomers − and degradable building blocks have also been made possible through cationic polymerizations. − Furthermore, the nature of the propagating cation can serve to control the sequence in terpolymerization . More recently, an unprecedented discoverycatalyst-controlled stereoselective cationic polymerization of VEshas been demonstrated by Teator and Leibfarth, , where poly­(vinyl ether)­s of high isotacticity show distinctive physical properties.…”

“…23−25 Furthermore, the nature of the propagating cation can serve to control the sequence in terpolymerization. 26 More recently, an unprecedented discoverycatalyst-controlled stereoselective cationic polymerization of VEshas been demonstrated by Teator and Leibfarth, 27,28 where poly(vinyl ether)s of high isotacticity show distinctive physical properties. All these exciting discoveries call for further exploration of cationic polymerizations for precise control over molecular weight and complex architectures.…”