在乙烯聚合/共聚化异金属-催化剂中具有非常大的合作效应
Shaofeng Liu1, Alessandro Motta, Aidan R Mouat
1Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States.
Journal of the American Chemical Society
|July 2, 2014
概括
新的异金属催化剂产生线性低密度聚乙烯 (LLDPE) 具有受控的n-butan分支. 靠近和的距离影响了olefin链接和链接传输速率.
科学领域:
- 有机金属化学 有机金属化学
- 聚合物科学 聚合物科学
- 催化剂是一种催化剂.
背景情况:
- 开发用于olefin聚合物的新型催化剂对于生产具有定制性质的聚合物至关重要.
- 不同金属复合体为催化活动提供了独特的电子和硬质环境.
- 控制聚乙烯的分支是实现所需材料特性的关键,例如密度和灵活性.
研究的目的:
- 合成和描述新型异金属-复合物.
- 评估这些复杂物作为乙烯聚合物的催化剂的性能.
- 研究催化剂结构和金属中心的接近对聚合物特性,特别是分支的影响.
主要方法:
- 包括SNS,PNP和NNN连接体系统在内的异金属复合体的合成和完整表征.
- 使用乙烯作为单体和甲基氨酸 (MAO) 作为共催化剂的烯聚合研究.
- 聚合物产品的分析,使用确定分子量,活性和分支模式的技术.
- 密度函数理论 (DFT) 计算以支持对催化剂行为的实验观测.
主要成果:
- 基于SNS的复合物 (Ti-C0-Cr ((SNS),Ti-C2-Cr ((SNS),Ti-C6-Cr ((SNS)) 产生具有独家n-butan分支的线性低密度聚乙烯 (LLDPE).
- 与Ti-C0-Cr (SNS) 和Ti-C6-Cr (SNS) 相比,Ti-C0-Cr (SNS) 的活性,分子量 (Mn) 和分支密度都更高.
- 与乙烯和1-烯的竞争实验表明,Ti-C0-Cr (SNS) 优先结合n-butanyl分支,与双重催化剂系统不同.
- DFT计算表明,密切的Ti···Cr空间近距离和弱相互作用会影响olefin链接和链传输速率.
结论:
- 合成的异金属复合物是有效的烯聚合催化剂.
- 该SNS连接体系统,特别是短链接器 (Ti-C0-Cr(SNS),可以精确控制分支,产生具有n-丁基的LLDPE.
- 和中心的近距离,以及特定的相互作用,在确定聚合结果和聚合物微观结构方面发挥着重要作用.
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