CATIONIC POLYMERIZATION OF ALPHA-PINENE I NITIATED BY ALCL3 SBCL3 - STUDIES ON THE NATURE OF THE INITIATING SPECIES/

The effects of the preparation methods of the AlCl3/SbCl3 binary catal yst and the proton trap 2,6-ditert-butyl-4-methylpyridine (DTBMP) on t he cationic polymerization of alpha-pinene were investigated respectiv ely, The results showed that, if AlCl3 and SbCl3 were melted to form t he combined catalyst, its initiating activity was higher than that of the catalyst obtained by simply mixing of AlCl3 and SbCl3. alpha-Pinen e was hardly initiated by the simple combination of AlCl3 and SbCl3 at -78 degrees C, however, the melted binary catalyst system led to a fa st polymerization even at such a low temperature, The proton trap DTBM P had no obvious effects on the AlCl3/SbCl3 catalyzed polymerization i n term of the rate and the molecular weight distribution. These result s indicated that new initiating species which was different from proto nic species H-circle plus in nature was generated by the reaction of A lCl3 and SbCl3. Furthermore, the reaction of AlCl3 and SbCl3 was exami ned by Al-27 NMR spectrum, Na signal was observed in the Al-27 NMR spe ctrum of AlCl3 atone system because of its poor solubility in the used solvent(toluene), but there appeared a strong absorption in the spect rum of AlCl3/SbCl3 binary system, and the chemical shifts unchanged be fore and after the polymerization. These show that a new Al-containing compound, soluble in toluene, was generated by AlCl3 and SbCl3 to ini tiate the polymerization, and that the metal atom adding to the monome r Is not Al but Sb in the initiating reaction. The proposed initiating cation was[SbCl4](circle plus), and the counter anion was [Al2Cl7](ci rcle minus).