Cationic polymerization of isobutylene by complexes of alkylaluminum dichlorides with diisopropyl ether: An activating effect of water

Abstract

The RAlCl2 3 OiPr2 -co-initiated (R 5 iBu or Et) cati-onic polymerization of isobutylene in the presence of externallyadded water (0.016–0.1 mM) in nonpolar n-hexane at 10 C andhigh monomer concentration ([IB] 5 5.8 M) has been investi-gated. It was shown that the sequence of H2 O introduction intothe system had the crucial effect on the polymerization rate,saturated monomer conversion, and, to a lesser extent, thecontent of exo-olefin end groups. Particularly, the highest poly-merization rate (>70% of monomer conversion in 10 min) andacceptable exo-olefin end groups content ( 83%) wereobserved when iBuAlCl2 3 0.8OiPr2 reacted with suspended inn-hexane H2O before the monomer addition. Better functional-ity can be obtained when H2 O is introduced into the system inthe course of the polymerization (after 3–10 min since the ini-tiation of reaction). Under these conditions, highly reactive pol-yisobutylenes (exo-olefin content is 86–89%) with desired lowmolecular weight (Mn 5 1000–2000 g mol21 ) in a high yield(75–90% of monomer conversion in 20 min) were readily syn-thesized.