Nd(OR)_3催化异戊二烯聚合动力学及聚合物结构

Polymerization Kinetics and Structure of Polyisoprene Synthesized with Nd(OR)~3 Catalyst Systems

研究了Nd(OR)_3—A1(i—Bu)_3一A1Et_2Cl体系催化异戊二烯聚合的动力学和所得聚异戊二烯的分子结构。结果表明,本体系的有效利用率为6％左右。在Al(i—Bu)_3用量较高时,主要发生活性中心向A1的链转移;在A1/Nd≤20,聚合温度低于室温条件下可获得“活的”聚合物。聚合物分子量高、分布宽,主要受A1(i—Bu)_3用量和聚合温度影响。分子量分布宽与其GPC图呈双峰有关。催化剂的相分离实验表明,体系中有两种不同的活性种存在:高活性生成高分子量聚合物的固相活性种和低活性生成低分子的可溶性活性种。聚异戊二烯的顺1,4—链节含量在95％左右,其余为3,4—链节。

The kinetics of isoprene polymerization and molecular weight(MW), molecular weight distribution (MWD), molecular microstructure (MM S) of the polyisoprene synthesized with Nd(OR)_3 Al(i Bu)_3 AlEt_2Cl catalyst system have been studied. The results showed that effective active centre percentage of the catalysts was about 6% and that at lower Al/Nd and below room temperature the polymerization system had some 'active polymerization' characteristics. The GPC graph, in which it was found that MWD had bi-peak distribution, and the experiment, in which a pre-formed catalyst was separated into precipitate and solution phase, showed that two kinds of active centres existed in the systems: high active solid centres which produce high MW PIp and low active solution centres which produced low MW PIp. The MMS of the PIp was characterized be IR and ^(13)C NMR. It was confirmed that the synthesized PIp had about 95% cis-1, 4 units, the rest being 3, 4-adding products.