Living cationic polymerization of vinyl ethers with carboxylic acid/tin tetrahalide initiating systems. I. New initiating systems based on acetic acid and selection of Lewis acid and basic additive leading to living polymers with low polydispersity

Abstract

Cationic polymerization of isobutyl vinyl ether (IBVE) with acetic acid (CH3COOH)/tin tetrahalide (SnX4: X = Cl, Br, I) initiating systems in toluene solvent at 0°C was investigated, and the reaction conditions for living polymerization of IBVE with the new initiating systems were established. Among these tin tetrahalides, SnBr4 was found to be the most suitable Lewis acid to obtain living poly(IBVE) with a narrow molecular weight distribution (MWD). The polymerization with the CH3COOH/SnBr4 system, however, was accompanied with the formation of a small amount of another polymer fraction of very broad MWD, probably due to the occurrence of an uncontrolled initiation by SnBr4 coupled with protonic impurity. Addition of 1,4‐dioxane (1–1.25 vol %) or 2,6‐di‐tert‐butylpyridine (0.1–0.6mM) to the polymerization mixture completely eliminated the uncontrolled polymer to give only the living polymer with very narrow MWD (Mw/Mn ≤ 1.1; Mw, weight‐average molecular weight; Mn, number‐average molecular weight). The Mn of the polymers increased in direct proportion to monomer conversion, continued to increase upon sequential addition of a fresh monomer feed, and was in good agreement with the calculated values assuming that one CH3COOH molecule formed one polymer chain. Along with these results, kinetic study and direct 1H‐NMR observation of the living polymerization indicated that CH3COOH and SnBr4 act as so‐called “initiator” and “activator”, respectively, and the living polymerization proceeds via an activation of the acetate dormant species. The basic additives such as 1,4‐dioxane and 2,6‐di‐tert‐butylpyridine would serve mainly as a “suppressor” of the uncontrolled initiation by SnBr4. The polymers produced after quenching the living polymerization with methanol possessed the acetate dormant terminal and they induced living polymerization of IBVE in conjunction with SnBr4 in the presence of 1,4‐dioxane. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3173–3185, 1998

Cationic polymerization of p-methylstyrene using various metal chlorides: design rationale of initiating systems for controlled polymerization of styrenes

“…This is possibly attributed to the generation of a large amount of SnCl 4 (OH) − and/or the undetectable interaction between SnCl 4 and DTBP. [27][28][29][30][31] In contrast, metal trichlorides were ineffective in the present system, corresponding to the ineffectiveness of the anion effect in the cationic polymerization of St 32 and IBVE 18,33 using EtAlCl 2 , FeCl 3 and GaCl 3 in conjunction with nBu 4 NCl.…”

Living cationic polymerization of isobutyl vinyl ether using a variety of metal oxides as heterogeneous catalysts: Robust, reusable, and environmentally benign initiating systems

“…Generally, DTBP, which possesses two bulky substituents around the basic nitrogen atom, is used to trap protic impurities such as adventitious water to prevent unintended initiation reactions in living cationic polymerization 14. Complex formation with a Lewis acid catalyst40–42 and interaction with a carbocation43 are also reported as additional roles of DTBP in some studies, although others claim there is no proof of this 44, 45. In polymerization of IBVE with IBVE–AcOH/EtAlCl 2 initiating systems,46 a large amount (1.0 M) of DTBP has little effect on the rate and control of the reaction, which indicates that DTBP cannot interact with the propagating species derived from IBVE.…”

Living cationic polymerization of vinyl ethers with a urethane group

“…Cationic polymerizability of 1 was first studied in toluene or CH 2 Cl 2 at different temperatures (0 and −30 °C) with various cationic initiators including BF 3 OEt 2 , CH 3 COOH/SnBr 4 ,11 HCl/ZnCl 2 ,12 and HCl/SnBr 4 13. The latter three binary initiating systems induce living cationic polymerization of alkyl vinyl ethers 11–13. All the polymerization mixtures remained homogeneous over the range of reaction conditions used.…”