Dual-Site Polymeric Heterogeneous α-Diimine Ni Catalysts with Tailored Spatial Distribution for Ethylene Polymerization
Jie Li, Yu Wang, Wen Cai, Gang Yang, Qiuhui Tian, Yongshuang Huang, Dan Peng, Chen Zou, Chen Tan
Abstract
Dual-site molecular heterogeneous catalysts for synthesizing polyolefin in-reactor blends have received increasing attention in academia and industry. It is hypothesized that the mesoscopic spatial distribution of different catalyst molecules in dual-site catalyst particles will have significant impacts on the superstructures and properties of polyolefin in-reactor blending products. It is difficult for typical heterogenization to tune the spatial distribution of different molecular catalyst components in the particles. In this contribution, a self-supporting strategy based on nickel-catalyzed precipitation coordination polymerization of a polar monomer was used to achieve not only heterogenization of the catalysts but also spatial distribution tuning of different catalytic components in the polymeric particles. These polymeric heterogeneous dual-site catalysts led to higher activities compared with homogeneous molecular catalysts. Moreover, they resulted in high molecular weights, good morphological control, and improved compatibility with polar materials. The composition and physical properties of the blend can be controlled by the molar ratio of the two catalytic components. Interestingly, it was shown that the different spatial distribution types can result in great differences in thermal, mechanical, and rheological properties and applications of the obtained blends.