The effects of the preparation methods of the AlCl3/SbCl3 binary catalyst and the proton trap 2,6-ditert-butyl-4-methylpyridine (DTBMP) on the cationic polymerization of alpha-pinene 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. alpha-Pinene was hardly initiated by the simple combination of AlCl3 and SbCl3 at -78 degrees C, however, the melted binary catalyst system led to a fast polymerization even at such a low temperature, The proton trap DTBMP had 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-circle plus in nature was generated by the reaction of AlCl3 and SbCl3. Furthermore, the reaction of AlCl3 and SbCl3 was examined by Al-27 NMR spectrum, Na signal was observed in the Al-27 NMR spectrum of AlCl3 atone 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](circle plus), and the counter anion was [Al2Cl7](circle minus).
