Abstract: The effects of the preparation methods of the AlCl₃/SbCl₃ binary catalyst and the proton trap 2,6-ditert-butyl-4-methyl pyridine(DTBMP)on the cationic polymerization of apinene were investigated respectively.The results showed that, if AlCl₃ and SbCl₃ were melted to form the combined catalyst,its initiating activity was higher than that of the catalyst obtained by simply mixing of AlCl₃ and SbCl₃.α-Pinene was hardly initiated by the simple combination of AlCl₃ and SbCl₃ at-78℃,howeve,the melted binary catalyst system led to a fast polymerization even at such a low temperature,The proton trap DTBMPhad no obvious effects on the AlCl₃/SbCl₃ catalyzed polymerization in term of the rate and the molecular weight distribution.These results indicated that new initiating species which was different from protonic species H^⊕ in nature was generated by the reaction of AlCl₃ and SbCl₃.Furthermore,the reaction of AlCl₃ and SbCl₃ was examined by ²⁷Al NMRspectrum.No signal was observed in the ²⁷Al NMRspectrum of AlCl₃ alone system because of its poor solubility in the used solvent (toluene), but there appeared a strong absorption in the spectrum of AlCl₃/ SbCl₃ binary system,and the chemical shifts unchanged before and after the polymerization.These show that a new Al-containing compound, soluble in toluene,was generated by AlCl₃ and SbCl₃ to initiate the polymerization,and that the metal atom adding to the monomer is not Al but Sb in the initiating reaction.The proposed initiating cation was[SbCl₄]^⊕,and the counter anion was[Al₂Cl₇]^Θ.

Key words: AlCl₃/SbCl₃, α-Pinene, Nature of the initiating species