Living cationic polymerization of isobutyl vinyl ether

Since the discovery of the first controlled/living cationic polymerization of isobutyl vinyl ether [IBVE CH2=CH OCH2CH(CH3)2 ] with the HI/... 

Table 4 shows typical reaction conditions and results of the living cationic polymerization of isobutyl vinyl ether (IBVE) with the HCl/ZnCh [127] and the CFjCC H/ZnCL [227] initiating systems. The former system is now among the most convenient for the synthesis of poly(alkyl vinyl... 

S. Kwon, H. Chun, and S. Mah, Photo-induced living cationic polymerization of isobutyl vinyl ether in the presence of various combinations of halides of diphenyliodonium and zinc salts in methylene chloride. Fibers Polymers, 2004, 5(4), 253-258. 

S. Kwon, et al., Living cationic polymerization of isobutyl vinyl ether (II) Photoinduced living cationic polymerization in a mixed solvent of toluene and diethyl ether. J. Appl. Polym. Sci. 2006, 101(6), 3581-3586. 

M.U. Kahveci, M.A. Tasdelen, and Y. Yagci, Photochemically initiated free radical promoted living cationic polymerization of isobutyl vinyl ether. Polymer 2007, 48(8), 2199-2202. 

M. Kamigaito, M. Sawamoto, and T. Higashimura, Living cationic polymerization of vinyl ethers by electophile lewis acid initiating systems. 6. Living cationic polymerization of isobutyl vinyl ether by RCOOH/lewis acid initiating systems effects of carboxylate ions and lewis acid activators. Macromolecules 1991, 24(14), 3988-3992. 

KAM 92b] Kamigaito M., Yamaoka K., Sawamoto M. et al, Living cationic polymerization of isobutyl vinyl ether by benzoic acid deiivatives/zinc chloride initiating systems slow interconversion between dormant and activated growing spQciQS , Macromolecules, vol. 25, pp. 6400-6406, 1992. 

Kojima, K., Sawamoto, M. and Higashimura, T. (1989) Living cationic polymerization of isobutyl vinyl ether by hydrogen iodide/Lewis acid initiating systems effects of Lewis acid activators and polymerization kinetics. Macromolecules, 22,1552-1557, doi 10.1021/ma00194a008. 

Based on this methodology, this first study employs triftmctional compounds 26 and 27, which were prepared from CF3COOH and trifrinctional vinyl ethers, as trifrinctional initiators for living cationic polymerization of isobutyl vinyl ether (Scheme 9). 

All previously discussed examples of living cationic polymerization of vinyl ethers were based on homogeneous polymerization media. In 2007, Oashima and coworkers demonstrated the living polymerization of isobutyl vinyl ether in the presence of iron(III) oxide as heterogeneous catalyst and ethyl acetate or dioxane as base [58]. The major advantage of this heterogeneous catalytic system is the easy removal of the metal oxide catalyst. In addition, it was demonstrated that the iron(III) oxide could be reused for at least five times without a decrease in activity. 

Aoshima S, Higashimura T (1989) Living cationic polymerization of vinyl monomers by organoaluminum halides. Living polymerization of isobutyl vinyl ether by EtAlCl2 in the presence of ester additives. Macromolecules 22 1009-1013... 

Heterogeneous conditions, due to poor solubility of heteropoly acid, in polymerization of isobutyl vinyl ether with H3PW12O40 in CH2CI2 were also studied. When bases like 1,4-dioxane or tetrahy-drofuran were present the molecular weight distributions were very broad. By contrast, polymerizations in the presence of dimethyl sulfide at —30°C yielded living polymerizations of the ether. Here too, the product had very narrow molecular weight distribution [139]. In summary, some typical features of living cationic polymerizations are ... 

The observation in 1949 (4) that isobutyl vinyl ether (IBVE) can be polymerized with stereoregularity ushered in the stereochemical study of polymers, eventually leading to the development of stereoregular polypropylene. In fact, vinyl ethers were key monomers in the early polymer Hterature. Eor example, ethyl vinyl ether (EVE) was first polymerized in the presence of iodine in 1878 and the overall polymerization was systematically studied during the 1920s (5). There has been much academic interest in living cationic polymerization of vinyl ethers and in the unusual compatibiUty of poly(MVE) with polystyrene. 

The first synthesis of star polymers with a microgel core was reported by Sa-wamoto et al. for poly(isobutyl vinyl ether) (poly(IBVE)) [3,4]. In the first step, living cationic polymerization of IBVE was carried out with the HI/ZnI2 initiating system in toluene at -40 °C. Subsequent coupling of the living ends was performed with the various divinyl ethers 1-4. 

Three arm amphiphilic star-block copolymers of isobutyl vinyl ether (IBVE) and 2-hydroxyethyl vinyl ethers were also prepared by Higashimura et al. [23]. The synthetic strategy involved the sequential living cationic polymerization of IBVE and 2-acetoxyethyl vinyl ether, initiated by the trifunctional initiator system composed of tris(trifluoroacetate) and ethylaluminum dichloride, with excess of 1,4-dioxane as a carbocation-stabilizing Lewis base (Scheme 8). 

Living cationic polymerization of vinyl ethers initiated by an SnCU/RCl catalytic system can be carried out in a continuous microflow system, which consists of a mutilamination micromixer M (channel width = 40 pm, IMM) and a microtube reactor R (Figure 14.1). A solution of a monomer and RCI is mixed with a solution of SnCU using the micromixer at —78 °C and the resulting mixture was allowed to react in the microtube reactor at the same temperature. For example, isobutyl vinyl ether (IBVE) was polymerized using functionalized initiators to obtain end-functionalized polymers of narrow molecular weight distribution (Mw/M < 1.2) (Scheme 14.4). 

Figure 17 MWDs of poly(isobutyl vinyl ether) to illustrate the three general methods for living cationic polymerizations at -15° C [M]0 = 0.38 Af [HCI]0 = [ZnCl2]0 = rSnCL(]0 = 5.0 mA/ conversion = ca.100%. Initiating systems and reaction conditions (a) HCl/ZnCl2, in toluene without additive (b) HCl/SnCU, in toluene without additive (c) HCl/SnCLt, in toluene with added tetrahydrofuran (100 mM) (d) HCl/SnCU, in CH2C12 without additive (e) HCl/SnCU, in CH2C12 with added Bu4NCl (2.0 mM). (From Refs. 73 and 105.)...

Propenyl Ethers and Unsaturated Cyclic Ethers Propenyl ethers (CH3—CH=CH—OR R = ethyl, isobutyl, etc. cis- and trans-isomers) and 3,4-dihydrofuran are linear and cyclic a,/3-unsaturated ethers, that can be regarded as / -substituted vinyl ether derivatives. For these monomers a few controlled/living cationic polymerizations have been reported. The HI/I2 system is generally effective for both linear and cyclic monomers [181,182,183], whereas a recent study by Nuyken indicates that the IBVE-HI adduct coupled with nBu4NC104 is suited for 3,4-dihydrofuran (see Section V.A.4) [184]. A variety of mono- and bifunctional propenyl ethers can readily be prepared by the ruthenium complex-catalyzed isomerization of corresponding allyl ethers [185]. 

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