AlCl3/SbCl3引发α-蒎烯阳离子聚合反应──引发活性种本质研究

Abstract

摘要 考察 了复合 催 化剂 AlCl3/SbCl3的不 同配 制方法 和 质子 捕 捉 剂2,6-二 异 丁 基-4-甲基 毗 吮(DTBMP)对 α-企 旅烯 阳 离子 聚合反应 的影 响 结果表 明,AlCl3 和 SbCl3加 热熔 融 复合 比简单 复合的引发 聚合活性更高, DTBMP对该复合催化剂 的聚合反 应速 率及其产 物分子 量分 布 均 无 明 显 影响, 证 明 该 复 合 催 化 剂 形 成 的 活 性 种 本 质 上 与 质 子 H⊕ 活 性 种 不 同, 是 新 型 活 性 种 .根 据 27Al NMR 对 该体系 活性种分析结果 , 认为 引发 阳 离子是[SbCl4]⊕,抗衡 阴 离子是[Al2Cl7]Θ.

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 α-pinene were investigated respectively. The results showed that, if A1C13 and SbCl3 were melted to form the combined catalyst, its initiating activity was higher than that of the catalyst obtained by simply mixing of A1C13 and SbCl3. α-Pinene was hardly initiated by the simple combination of A1C13 and SbCl3 at - 78 °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⊕ in nature was generated by the reaction of A1C13 and SbCl3. Furthermore, the reaction of A1C13 and SbCl3 was examined by 27Al NMR spectrum. No signal was observed in the 27Al NMR spectrum of A1C13 alone system because of its poor solubility in the used solvent (toluene), but there appeared a strong absorption in the spectrum of A1C13/ 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 A1C13 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 [AI2Cl7]⊖.