The Living Cationic Polymerization of α-Methylstyrene with BCI3as Coinitiator

Abstract

The cationic polymerization of α-methylstyrene (αMeSt) was studied using the cumyl chloride (CumCl), (CH₃)₃C-CH₂- C(CH₃)2-CH₂-C(Ph)₂-OCH₃ (TMPDPEOMe) or (CH₃)₂C(Ph) CH₂C(CH₃)(Ph)Cl (the HCl adduct of αMeSt dimer, DiαMeStHCl)/BCl₃ initiator/coinitiator systems in the presence of proton trap in methyl chloriderhexanes (MeCl:Hex) or MeCl: methylcyclohexane (MeChx) mixtures at −80 and −60°C. While CumCl is not an efficient initiator in conjunction with BCl₃, TMPDPEOMe and Di αMeStHCl were found to be very efficient initiators. The polymerization was much faster in the MeCl:Hex mixture than in MeCl:MeChx. The polymerization rate was also higher at −80°C than at −60°C in the same solvent. The polymerization was found to be living at −80°C, as well as at −60°C, giving rise to poly(α-methylstyrene) (PαMeSt) with controlled molecular weight and narrow molecular weight distribution (M_w/M_n ∼ 1.1-1.2). The chain ends remained living for up to 40 minutes under monomer starved conditions at −80°C, but they rapidly decomposed at −60°C.