支链分布可控新型烯烃共聚催化剂的研究

In conventional copolymer,the branch chain presents no-symmetrical distribution, which caused by the ethylene concentration in this system keeps constant while the α-olefin concentration decreased gradually and the difference of their molecular diffusion rate, the activation energy coordination to the metal center and reactivity ratios.On the other hand, the density of branch chain on unit length backbone ( 1000 carbon atoms) isn’t equal and the distance of the neighbor branch increase as the polymerization reaction extend, which affect the mechanism property of the copolymer hardly. In our plan, one ethylene oligomerization center and olefin copolymerization center will be located into one molecular by rigid ligand, when activated with cocatalyst, the α-olefin concentration in the system maintains constant just because the α-olefin will be produced with constant yield at oligomerization center. Then the α-olefin molecular will diffuse and captived by copolymerization center rapidly, and so, the copolymer with regular branch chain distribution is gained after the α-olefin molecular coordination to copolymerization center and inserting into propagation polymer chain. The branch chain density can be controlled by modifying the difference between the two center. It is can expected that the mechanical properties of the polymer material inhence greatly as the intermolecular forces increase according to the augment of the molecular contact area.The copolymer keeps higher .mechanical propertie with lower crystal.

目前的乙烯与a-烯烃共聚材料中的支链是非均匀分布的，原因在于反应器中乙烯浓度可以基本恒定而共聚单体的α-烯烃浓度逐渐下降，且它们的分子扩散速度、与中心金属配位活性能、竟聚率等都不相同，因此随着聚合进程延长，在不断增长的聚乙烯链上相邻支链之间的间隔越来越大，单位长度的碳链骨架(每1000个碳原子)上支链分布密度递减，极大影响了共聚物的力学性能。本课题以构象固定的双中心催化剂为基础，把齐聚中心与共聚中心捆绑在一起，齐聚中心以近乎恒定的速率高选择性地原位生成α-烯烃，并快速被共聚中心捕捉并与共聚中心金属进行配位并插入增长着的聚乙烯链形成支链分布均匀的共聚物，该类聚合物的微观结构可控，支链分布密度由两个活性中心的活性差值进行精确控制。与传统共聚物比较，其分子间的接触面积增大，导致分子间作用力增强，具有结晶度低、机械强度高的性质。

本项目为前一个课题的延续，立足于研制烯烃聚合催化剂，生产支链分布均匀的聚烯烃。目前的乙烯与a-烯烃共聚所得的聚烯烃材料中的支链分布是非均匀的，原因在于反应器中乙烯浓度可以维持恒定而共聚单体的α-烯烃浓度逐渐下降，且它们的分子扩散速度、与中心金属配位活性能、竟聚率等都不相同，因此随着聚合进程延长，在不断增长的聚乙烯链上相邻支链之间的间隔越来越大，单位长度的碳链骨架(每1000个碳原子)上支链分布密度逐级递减，极大影响了共聚物的力学性能。本课题设计合成了一系列的的双中心催化剂，把齐聚中心与共聚中心捆绑在一起，助催化剂MAO活化以后齐聚中心以近乎恒定的速率高选择性地原位生成α-烯烃，主要是1-己烯和1-辛烯，快速被共聚中心捕捉并并插入增长着的聚乙烯链形成支链分布均匀的共聚物，该类聚合物的微观结构可控，支链分布密度由两个活性中心的活性差值进行精确控制。与传统共聚物比较，其支链分布均匀，导致分子间作用力增强，具有结晶度低、机械强度高等性质。本项目的成果为合成高性能聚烯烃材料打下基础，具有潜在的巨大的工业价值。