Boost the formation of active species in the constrained-geometry catalyst by the intermolecular TiO non-covalent interactions

Intermolecular Ti O non-covalent interactions regulate CGC polymerization behavior. • POSS forms a Ti-O-Si-Cl ring, enhancing activity. • D3 promotes ligand rearrangement and 1-octene incorporation. • Non-covalent Ti O modification enables tailored POE microstructures. When metallocene catalysts are modified by changing the chemical structures of their ligands and bridges, the intrinsic coupling of electronic and steric effects leads to performance trade-offs, making it challenging to simultaneously optimize catalytic activity, thermal stability, and comonomer incorporation capability. Herein, we present an intermolecular non-covalent interaction strategy for regulating the polymerization behavior of constrained-geometry catalysts (CGCs). By physically blending CGC with siloxanes featuring distinct spatial architectures, namely cage-like polyhedral oligomeric silsesquioxane (POSS) and cyclic hexamethylcyclotrisiloxane (D3), two catalytic systems with similar chemical compositions but markedly different polymerization behaviors and product chain microstructures were constructed. The CGC/POSS system exhibits an increase in catalytic activity, whereas the CGC/D3 system significantly enhances 1-octene incorporation in the resulting copolymer. Comprehensive characterizations, including XPS, EXAFS, UV–vis, and EPR spectroscopy, elucidate the Ti O non-covalent interaction mechanism and the evolution of active centers during catalyst activation. POSS and D3 both induce structural distortion of the CGC molecule through Ti O non-covalent interactions, but they impose distinct electronic effects on the Ti active center. This work provides a facile intermolecular non-covalent modification strategy for polyolefin catalysis, enabling enhanced catalytic performance of CGC catalysts and effective control over POE chain microstructure. Download: Download high-res image (48KB) Download: Download full-size image