Introduction
cation-exchange resin surface, as model compounds of carbon black (Scheme 1). In addition, the grafting reactions of polyIBVE with controlled molecular weight and It is well known that carbon blacks have surface acidic narrow MWD onto polystyrene-bead and cation-exfunctional groups such as carboxyl and phenolic hychange resin after the quenching of the polymerization droxyl groups, 1,2 and these functional groups undergo systems with methanol were also discussed. general chemical reactions. [3][4][5] Especially, carboxyl groups on the surface have a high acidity because of the presence of phenolic hydroxyl groups as neighboring groups of them. We have reported that carboxyl groups EXPERIMENTAL on the surface have the ability to initiate cationic polymerization of various vinyl monomers, such as N-vinylcarbazole, 6 vinyl ethers, 7 N-vinyl-2-pyrrolidone, 8 and Crosslinked polystyrene-bead used was SGP-100C obtained from Soken Chemical and Engineering Co. Ltd., a-methylstyrene. 9 During the polymerization, a part of polymer formed was grafted onto the surface through Japan. The particle size was 10-40 mm. It was washed with chloroform and dried in vacuo at 110ЊC before use. the termination reaction of propagating carbocation with counteranion, i.e., carboxylate anion on the sur-Cation-exchange resin, a copolymer of acrylic acid and divinylbenzene (high-porous type), was WK20 ob-face, but the percentage of grafting was less than 10% and molecular weight distribution (MWD) was very tained from Mitsubishi Chemical Ind., Japan. The particle size and the content of carboxyl group were 297-broad. 6 Recently, it has been reported that living cationic poly-1190 mm and 8.90 mmol/g, respectively. The cationexchange resin was dried in vacuo at 90ЊC before use. merization of isobutyl vinyl ether (IBVE) is initiated by a system consisting of protonic acid (HB) and a weak
The carboxyl type cation-exchange resin is abbreviated as PAA-COOH. Lewis acid activator (MXn) 10,11 ; typical examples are hydrogen iodide/iodine or zinc iodide (ZnI 2 ) systems 12,13 and Zinc chloride was commercially supplied as a solution (Aldrich Chemical Co., Inc., 1.0 M solution in di-carboxylic acids/zinc chloride (ZnCl 2 ) systems. 14,15 On the other hand, we have reported that carboxyl groups on ethyl ether), which was diluted with purified toluene. Isobutyl vinyl ether (IBVE) (Tokyo Kasei Kogyo Co., carbon black surface, coupled with ZnCl 2 , induced living cationic polymerization of IBVE and polyIBVE was Ltd.) was washed with 5% aqueous sodium hydroxide solution and then pure water, dried over night over grafted on the surface. 16 In the present communication, we investigated the potassium hydroxide, refluxed over sodium, and distilled twice before use. Toluene (Kanto Chemical Co., effects of ZnCl 2 as catalyst on the cationic polymerizations of IBVE initiated by carboxyl groups introduced Inc.) was washed with concentrated sulfuric acid, pure water, 5% aqueous sodium hydroxide solution, and pure onto crosslinked polystyrene-bead surface and those on water, dried overnight over calcium chloride, refluxed over sodium, and distilled twice before use.