Living carbocationic polymerization of isobutyl vinyl ether and the synthesis of poly[isobutylene‐b‐(isobutyl vinyl ether)

Abstract

AbstractThe MeCH(O‐i‐Bu)Cl/TiCl4/MeCONMe2 initiating system was found to induce the rapid living carbocationic polymerization (LC⊕Pzn) of isobutyl vinyl ether (IBuVE) at −100°C. Degradation by dealcoholation which usually accompanies the polymerization of alkyl vinyl ethers by strong Lewis acids is “frozen out” at this low temperature and poly(isobutyl vinyl ether)s (PIBuVEs) with theoretical molecular weights up to ca. 40,000 g/mol (calculated from the initiator/monomer input) and narrow molecular weight distributions (M̄w/M̄n ≤ 1.2) are readily obtained. According to 13C‐NMR spectroscopy, PIBuVEs prepared by living polymerization at −100°C are not stereoregular. The MeCH(O‐i‐Bu)Cl/TiCl4 combination induces the rapid LC⊕Pzn of IBuVE even in the absence of N,N‐dimethylacetamide (DMA). The addition of the common ion salt, n‐Bu4NCl to the latter system retards the polymerization and meaningful kinetic information can be obtained. The kinetic findings have been explained in terms of TiCl4. IBuVE and TiCl4 · IBuVE and TiCl4 · PIBuVE complexes. The HCl (formal initiator)/TiCl4/DMA combination is the first initiating system that can be regarded to induce the LC⊕Pzn of both isobutylene (IB) and IBuVE. Polyisobutylene (PIB)–PIBuVE diblocks were prepared by sequential monomer addition in “one pot” by the 2‐chloro‐2,4,4‐trimethylpentane (TMP‐Cl)/TiCl4/DMA initiating system. Crossover efficiencies are, however, below 35% because the PIB⊕ + IBuVE → PIB‐b‐PIBuVE⊕ crossover is slow. © 1993 John Wiley & Sons, Inc.