Cationic polymerization of isobutylene catalyzed by iBuAlCl2 in the presence of ethers: Effect of catalyst pre-activation and mixture of two ethers. (2nd September 2016)

• Record Type: Journal Article
• Authors: Shiman, Dmitriy I.; Vasilenko, Irina V.; Kostjuk, Sergei V.
• Is Part Of: Polymer. Volume 99(2016)
• Page Start: 633
• Page End: 641
• Publication Date: 2016-09-02
• Subjects: Cationic polymerization -- Isobutylene -- Highly reactive polyisobutylene; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2016.07.014
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: The cationic polymerization of isobutylene using pre-activated by the wet argon or salts hydrates i BuAlCl2 as catalyst in the presence of diisopropyl ether in n -hexane at 10 °C as a starting temperature and high monomer concentration ([IB] = 5.8 M) has been investigated. It was shown that pre-activated i BuAlCl2 possessed high activity (>90% of monomer conversion in 10 min) and unexpectedly high regioselectivity of β-H abstraction at rather low ether to Lewis acid ratio ( i Pr2 O/ i BuAlCl2 = 0.4). The use of pre-activated i BuAlCl2 as a co-initiator leads to formation of more uniform active species that results in narrowing of molecular weight distribution as compared to polyisobutylenes synthesized with non-pre-activated i BuAlCl2 . Much better control over polydispersity can be achieved by using of mixture of two ethers of different basicity and steric structure (diethyl and diisopropyl ethers) as additive instead of one (diisopropyl ether) during IB polymerization co-initiated by pre-activated i BuAlCl2 . Under optimized conditions ([ i BuAlCl2 pre-act. ] = 38 mM, [Et2 O] = [ i Pr2 O] = 7.6 mM, [H2 O] = 0.033 M, time: 15 min), desired low molecular weight (Mn ∼ 1000 g mol −1 ) highly reactive polyisobutylenes in high yield (>90%) with high content of exo -olefin end groups (>80%) and relatively low polydispersity (Mw /Mn = 2.4–2.7) were readily synthesized at high reaction temperature (10 °C) and monomer concentration ([IB] = 5.8 M). Graphical abstract: Highlights: Pre-activation of iBuAlCl2 by salt hydrates gives highly active catalysts for synthesis of HR PIB. Pre-activated i BuAlCl2 showed high activity and high regioselectivity of β-H abstraction at i Pr2 O/ i BuAlCl2 = 0.4. Pre-activated i BuAlCl2 in conjunction with mixture of iPr2 O and Et2 O affords polyisobutylene with low polydispersit. Proposed initiating systems have a great industrial importance.