均相Nd(Oct)_3/Al(i-Bu)_3/AlCl_3用于异戊二烯聚合

Homogenous Nd(Oct)_3/Al(i-Bu)_3/AlCl_3 catalyst for controlled isoprene polymerization

采用Nd（Oct）3、Al（i-Bu）3、AlCl3,AlCl3溶解于Al（i-Bu）3中配制成一定浓度的溶液作为氯配体。Nd（Oct）3与AlCl3在室温（20℃）下反应后,再加入一定量的Al（i-Bu）3,可配制成均相高效催化剂体系。所得聚合物同时具备顺-1,4含量高（96%）、高分子质量（10^5）、相对较窄的分子质量分布（Mw/Mn=2.1-3.0）等特征。更重要的是,证明了一些活性聚合的特征：a）无链终止反应;b）Mn和转化率线性相关;c）＂种子＂聚合中分子质量逐渐增加。虽然与典型的＂种子＂聚合有一些偏离,比如分子质量分布稍宽,Mn-转化率曲线不过原点,但仍然可认为是可控聚合。

Nd（Oct）3,Al（i-Bu）3 and AlCl3（AlCl3 is dissolved in Al to form aqueous as cocatalyst） homogenous catalytic system was synthesized when Nd（Oct）3 and AlCl3（AlCl3is dissolved in Al（i-Bu）3 to form aqueous） were mixed at 20 ℃,followed by the addition of Al（i-Bu）3.Nd（Oct）3/ Al（i-Bu）3 / AlCl3homogenous catalytic system is highly active for isoprene polymerization in hydrogenated gasoline.The molecular weight of polyisoprenes can be controlled by variation of [Nd（Oct）3]/ ratio,[Al（i-Bu）3]/[Nd（Oct）3] ratio and polymerization temperature and time.The Nd（Oct）3/ Al（i-Bu）3/ AlCl3catalyst polymerized isoprene to afford products featuring high cis-1,4 stereospecificity（ca.96%）,high molecular weight（ca.105） and relatively narrow molecular weight distributions（Mw/Mn=2.1-3.0） simultaneously.Some living polymerization characteristics were demonstrated：（a） absence of chain termination;（b） linear correlation between Mn and polymer yield;（c） increment of molecular weight in the ＇seeding＇ polymerization.Though some deviation from the typical living polymerization such as molecular weight distribution is not narrow enough and the line of Mn and polymer yield does not extrapolate to zero,controlled polymerization with the current catalyst can still be concluded.