POSS@TiCl4 nanoparticles: A minimalism styled Ziegler-Natta catalytic system

A robust immobilization strategy is proposed by the self-assembly of POSS and TiCl4 molecules, where a flexible double-Ti structure shows the most reduced energy barrier for ethylene insertion. [Display omitted] •A highly active molecular catalyst toward ethylene polymerization was synthesized according to the self-assembly of POSS and TiCl4.•A flexible double-Ti structure coordinated to Si-O-Si shows the most reduced energy barrier for ethylene insertion.•Catalytic nanoparticles show robust resistance to H2, enhanced incorporation of comonomer, and reduced entanglements of the synthesized polymer. Heterogeneous catalysis plays a crucial role in industrial olefin polymerization. Mechanistic understanding and optimization of Ziegler-Natta (ZN) catalyst are limited by the considerable complexity resulting from the multiple ingredients and complicated structures. Re-designing ZN catalytic systems with reduced complexity and adequate performance is of great interest. Here, we show that self-assembled polyhedral oligomeric silsesquioxane (POSS)@TiCl4 nanoparticles can effectively immobilize TiCl4 molecules in n-heptane solution, achieving the exceptional utilization of active centres. This uncomplicated system exhibits heterogeneous-like catalytic performance in ethylene polymerization, featured by high activities, fouling-free polymerization and a series of desirable properties of the nascent polymers such as reduced entanglement and spherical morphology. In addition, these catalytic nanoparticles show robust resistance to H2, and enhanced incorporation of comonomer towards ethylene/1-hexene copolymerization. By using DFT calculations the possible structures of the Ti active centres are proposed, of which a flexible double-Ti structure coordinated to Si-O-Si shows the most reduced energy barrier for ethylene insertion.