Arihiro Kanazawa 교수

Cationic polymerization of isobutyl vinyl ether (IBVE) was examined using a variety of metal halides. In the presence of an appropriate added base, ester or ether, the living polymerization of IBVE proceeded for almost all Lewis acids (MCln; M: Fe, Ga, Sn, In, Zn, Al, Hf, Zr, Bi, Ti, Si, Ge, Sb) used in conjunction with an IBVE−HCl adduct in toluene at 0 °C. The difference in the polymerization activity of these Lewis acids was significant. As examples, polymerization with some acids, such as Fe

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.

Abstract Recent advancements in living cationic polymerization of vinyl ethers are reviewed, especially focusing on newly developed initiating systems using various Lewis acid catalysts. In concert with the diversification of efficient metal halide catalysts, several types of initiators (cationogens) have been shown to mediate living polymerization, in which the nature of the central metals is responsible for the polymerization behavior. Other types of initiating systems, e.g., living cationic p

Heterogeneously catalyzed living cationic polymerization of isobutyl vinyl ether (IBVE) with Fe2O3 in the presence of an added base is described. Cationic polymerization of IBVE using Fe2O3 in conjunction with ethyl acetate or 1,4-dioxane and IBVE−HCl, a suitable cationogen, proceeded smoothly in a heterogeneous system to produce polymers with very narrow molecular weight distributions (Mw/Mn ≤ 1.1). The living polymerization was also achieved under unfavorable conditions: at higher temperature

A Lewis acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis acid catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer rea

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

The fast living cationic polymerization of isobutyl vinyl ether was demonstrated with FeCl3 as a Lewis acid catalyst in the presence of a cyclic ether. The reaction was completed in 15 s even under mild conditions and was 5 or 1000 times faster than the reaction with SnCl4 or EtAlCl2, respectively, in the presence of 1,4-dioxane. The faster reaction was attributed to the superior ability of FeCl3 to extract Cl− in comparison with the other two acids. In addition, the molecular weight distributio

Cationic terpolymerization of vinyl ether (VE), oxirane, and ketone successfully proceeded via unprecedented concurrent vinyl-addition, ring-opening, and carbonyl-addition mechanisms. In particular, the use of cyclohexene oxide as an oxirane resulted in terpolymerization via an exclusive one-way cycle, i.e., the reactions occurred only in the VE → oxirane, oxirane → ketone, and ketone → VE directions. Terpolymers that have repeating units of (VE_∼2-oxirane_∼2-ketone)<sub><i>n

A new design perspective on initiating systems for living cationic polymerization was gained by thorough examination of various metal chlorides as catalysts in conjunction with a weak Lewis base in the cationic polymerization of p-methoxystyrene. The Lewis acids clearly differed in controllability, in contrast to the findings of a previous report on the polymerization of isobutyl vinyl ether (IBVE) using various catalysts (all the metal chlorides used in the present study induced the controlled

Cationic polymerization of vinyl ether (VE) was examined with methanol/metal chloride initiating systems instead of those with the conventionally used VE−protonic acid adduct initiators. With MoCl5, a highly oxophilic metal halide, the polymerization of isobutyl VE (IBVE) using methanol proceeded in a living fashion in the presence of ethyl acetate, although the reaction was not controlled in conjunction with IBVE−HCl adduct. Furthermore, in the methanol-initiated polymerization, the Lewis acids

Stereospecific cationic polymerization of vinyl ethers (VEs) was investigated using iron(II) sulfate as a catalyst under various conditions, focusing on the improvement of stereoregulation ability and the dual control of stereoregularity and molecular weight. In conjunction with tBuOH, polymerization of isobutyl VE proceeded in relatively controlled fashion, indicating the production of long-lived species. In addition, the molecular weight of the stereoregulated portion, obtained as a methyl eth

Lactic acid-derived 1,3-dioxolan-4-ones (DOLOs), which do not undergo cationic homopolymerization, were demonstrated to yield copolymers with oxiranes through a cationic copolymerization via frequent crossover reactions. Acetal and ester moieties were generated in the main chain of the copolymers via crossover reactions from DOLO to oxirane and from oxirane to DOLO, respectively, which is in contrast to the unsuccessful generation of hemiacetal ester moieties in the homopropagation of DOLO. In a

Heterogeneous systems using iron oxides with low-valent Fe(II) components, FeO and Fe3O4, were designed for controlled/living radical polymerization of styrene and methyl methacrylate. The polymerizations with FeO in conjunction with an alkyl halide initiator bearing a C−Br bond such as ethyl α-bromophenylacetate proceeded in controlled fashions in the solvent mixtures of N,N-dimethylformamide/toluene or acetonitrile/toluene to yield polymers with predetermined molecular weights. The controllabi

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 atta

Abstract Cationic polymerization of isobutyl vinyl ether (IBVE) was examined using a variety of metal oxides in conjunction with IBVE–HCl adduct as a cationogen in toluene at 0 °C. Iron oxides (α‐Fe 2 O 3 , γ‐Fe 2 O 3 , and Fe 3 O 4 ) induced living polymerization in the presence of an added base, ethyl acetate or 1,4‐dioxane, to give polymers with very narrow molecular weight distributions (MWDs). Conversely, with other metal oxides such as Ga 2 O 3 , In 2 O 3 , ZnO, Co 3 O 4 , and Bi 2 O 3 , p