Kinetic features of ethylene copolymerization with 1-hexene over titanium-magnesium Ziegler–Natta catalysts: Effect of comonomer on the number of active centers and the propagation rate constant

Synthesis of Weakly Entangled Ultra-High-Molecular-Weight Polyethylene with a Fine Particle Size

“…This observation agrees well with the previous DFT calculations, which demonstrate that POSS molecules shows a clear preference to bind on the (110) plane rather than on the (104) and edge planes . Considering the Mg sites on the (110) plane as the most active position for hosting TiCl 4 , , it is therefore reasonable to deduce that the in situ embedding of POSS serving to block nearby Ti sites on the (110) plane will lead to more isolated active sites.…”

Reduced Entanglement Density of Ultrahigh-Molecular-Weight Polyethylene Favored by the Isolated Immobilization on the MgCl2 (110) Plane

“…The location and chemical structure of the active sites are the key for revealing the relationship between catalytic performances and catalyst structures in the olefin production and conversion processes (e.g., olefins homologation, propylene epoxidation, alkanes dehydrogenation, and olefin polymerization). , For olefin polymerization, the MgCl 2 -based Ziegler–Natta catalysts, which host TiCl 4 on the (104) and (110) faces of MgCl 2 , dominate olefin polymerization in today’s industry. − Numerous studies have been devoted to disclosing the structure of the catalytic species using the spectra investigation, − structural characterization, , and molecular modeling. − However, there are still many controversies on how the location and chemical structure of active species tailor the catalytic performances and the propagated chains, which is crucial for rationally designing more efficient catalysts and developing high-performance polyolefin. − …”

“…It is well known that most of TiCl 4 dispersed on the support are spectators. , Isolating the active species is one of the essential methods of acquiring more numbers of active species, so as to improve the catalytic activity and tailor the microstructure of the synthesized polymers (e.g., molecular weight and its distribution, stereoregularity, and entanglement density). − ,− In particular, for the tailored microstructure, a reduced entanglement density of the nascent polymer is inevitably necessary for enhancing the processability and mechanical property of the ultrahigh-molecular-weight polyethylene (UHMWPE). This synthesized weakly entangled UHMWPE presents an amorphous phase with a heterogeneous and metastable structure, where the entangled points are mainly distributed on the boundary of crystals. , Upon heating, the less entangled chains undergo chain explosion and reputation process in succession, which usually takes a long time to reach the thermally stable state. , The chain explosion of the less entangled UHMWPE facilitated the interfacial chain diffusion across the adjacent UHMWPE grains during the sintering process .…”

Integrated Effect of Comonomer and Catalyst on Copolymerization of Ethylene with Allylcyclopentane or Allylcyclohexane by Using Metallocene Catalysts

“…Comonomer effect is an important aspect in the study of coordination polymerization of olefin, and usually refers to the influence of the introduction of comonomer on the polymerization activity. [17][18][19][20][21] Although comonomers have a very significant effect on polymers, there are few reports on the study of polymer composition, structure and properties from the point of view of polymerization. [22,23] Previously, we studied the comonomer effects for olefin copolymerization by using metallocene and half-metallocene catalyst systems.…”

“…The polymerization behavior of catalyst is influenced by the introduction of comonomer. Comonomer effect is an important aspect in the study of coordination polymerization of olefin, and usually refers to the influence of the introduction of comonomer on the polymerization activity . Although comonomers have a very significant effect on polymers, there are few reports on the study of polymer composition, structure and properties from the point of view of polymerization .…”