Living carbocationic polymerization

Abstract

The synthesis of α,ω-di-tert-chloropolyisobutylenes $({}^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{t} }Cl - PIB - Cl^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{t} } )$with up to M_n ∼25,000 has been accomplished by the living polymerization of isobutylene (IB) using aliphatic di-tert-dichloroacetate initiators in conjunction with BCl₃ coinitiator in CH₃Cl and C₂H₅Cl solvents at −30°C. In comparison with the corresponding di-tert-diacetates, both rates and initiator efficiencies (I_eff) are greatly increased. Thus polymerizations are rapid and give 50–75 and 100% I_effs with 2,5-dichloroacetoxy-2,5-dimethylhexane (D(Cl₂AcO)DMeH₆) and trans-2,5-dichloroacetoxy-2,5-dimethyl-3-hexene (D(Cl₂AcO)DMeH ⁼₆ ), respectively. With 2,5-dichloroacetoxy-2,5-dimethyl-3-hexyne (D(Cl₂AcO)DMeH ^≡₆ ) the rates are relatively slower but the I_effs are ∼100%. The number average end functionalities ¯F_n were found to be 2.0 ± 0.1 by ¹H NMR spectroscopy.