Highly Reactive Polyisobutylenes via AlCl 3 OBu 2 -Coinitiated Cationic Polymerization of Isobutylene: Effect of Solvent Polarity, Temperature, and Initiator Irina V. Vasilenko, Dmitriy I. Shiman, Sergei V. Kostjuk Research Institute for Physical Chemical Problems of the Belarusian State University, 14 Leningradskaya St., 220030 Minsk, Belarus Correspondence to: S. V. Kostjuk (E-mail: kostjuks@bsu.by or kostjuks@rambler.ru) Received 7 September 2011; accepted 27 October 2011; published online 26 November 2011 DOI: 10.1002/pola.25830 ABSTRACT: The cationic polymerization of isobutylene using 2- phenyl-2-propanol (CumOH)/AlCl 3 OBu 2 and H 2 O/AlCl 3 OBu 2 ini- tiating systems in nonpolar solvents (toluene, n-hexane) at ele- vated temperatures (20 to 30  C) is reported. With CumOH/ AlCl 3 OBu 2 initiating system, the reaction proceeded by controlled initiation via CumOH, followed by b-H abstraction and then irre- versible termination, thus, affording polymers (M n ¼ 1000–2000 g mol 1 ) with high content of vinylidene end groups (85–91%), although the monomer conversion was low (35%) and poly- mers exhibited relatively broad molecular weight distribution (MWD; M w /M n ¼ 2.3–3.5). H 2 O/AlCl 3 OBu 2 initiating system induced chain-transfer dominated cationic polymerization of iso- butylene via a selective b-H abstraction by free base (Bu 2 O). Under these conditions, polymers with very high content of desired exo-olefin terminal groups (89–94%) in high yield (>85%) were obtained in 10 min. It was shown that the molecular weight of polyisobutylenes obtained with H 2 O/AlCl 3 OBu 2 initiating sys- tem could be easily controlled in a range 1000–10,000 g mol 1 by changing the reaction temperature from 40 to 30  C. The MWD was rather broad (M w /M n ¼ 2.5–3.5) at low reaction temperatures (from 40 to 10  C), but became narrower (M w /M n  2.1) at tem- peratures higher than 10  C. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 750–758, 2012 KEYWORDS: catalysis; catalysts; cationic polymerization; highly reactive polyisobutylene; isobutylene INTRODUCTION Polyisobutylene (PIB) is one of the most commercially important polymers synthesized by cationic mechanism possessing such unique properties as high ther- mal and chemical stability, low gas permeability and good flexibility. Depending on their molecular weight (M n ), com- mercially available PIBs can be divided into three main groups: (i) high- (M n > 100,000 g mol 1 ), (ii) medium- (M n ¼ 40,000–120,000 g mol 1 ), and (iii) low-molecular weight polymers (M n < 5000 g mol 1 ). Among them, the low-molec- ular weight PIBs with high content of the vinylidene end groups, that is, so-called highly reactive PIBs (HR PIBs), repre- sent the most important industrial class of isobutylene poly- mers due to their use as a raw material for manufacturing of lubricants and fuel additives. Recently, BASF, the worldwide leader in the production of HR PIBs, increased the capacity for the production of HR PIBs mainly due to the new market requirements. 1 These PIBs under trademark Glissopal V R with a number-average molecular weight (M n ) ranging between 550 and 2300 g mol 1 , molecular weight distribution (MWD) less than 2.0 and containing 75–85% of exo-olefin end groups are produced by a single-step process via cationic polymerization of isobutylene using modified BF 3 -based initiating systems. The precision synthesis of functional PIBs with controlled molecular weight and narrow MWD 2 was made possible after the discovery of controlled cationic polymerization 3 in the middle of 1980s by Higashimura and Kennedy teams. 4,5 The mono- or difunctional exo-olefin-terminated PIBs with 95–100% of exo-olefin groups were synthesized in a two steps process including TiCl 4 -coinitiated controlled cationic polymerization of isobutylene at 78  C followed by the reaction of tert-chloride-terminated PIB with isobutenyl- trimethylsilane 6 or dehydrochlorination of isolated tert- chloride-terminated PIBs with potassium tert-butoxide. 7 Exo-olefin-terminated PIBs (69–100%) could be also obtained through end-quenching of TiCl 4 -coinitiated con- trolled isobutylene polymerization with hindered bases (2,5- dimethylpyrrole, 1,2,2,6,6-pentamethylpiperidine) 8 or sul- fides 9 at 60  C. In the last case, the decomposition of sulfide adduct with PIB chain by excess of nucleophile (methanol and triethylamine) is required. 9 The main advan- tages of utilization the controlled cationic polymerization technique in preparation of HR PIBs are the possibilities to synthesize polymers with precisely controlled M n and very narrow MWD (M w /M n  1.2). However, the low reaction Additional Supporting Information may be found in the online version of this article. V C 2011 Wiley Periodicals, Inc. 750 JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 750–758 ARTICLE WWW.POLYMERCHEMISTRY.ORG JOURNAL OF POLYMER SCIENCE