Pressure-Sensitive Supported FI Catalyst for the Precise Synthesis of Uni- and Bimodal Polyethylene

Abstract

Pressure-sensitive phenoxy-imine titanium catalyst (FI-catalyst) was successfully synthesized by covalently immobilizing it on the surface of functionalized polystyrene (PS) nanoparticles, which acted as a support and a giant ligand simultaneously. The supported catalyst shows high catalytic activities in ethylene polymerization. Utilizing this catalyst, a serious of unimodal polyethylenes with tailored molecular weights ranging from 2 000 000 to 300 000 were produced under various reaction pressures and temperatures. Particularly, when the polymerization pressure was shifted during the reaction, the ethylene polymer with bimodal molecular weight distribution was successfully synthesized in only a single reactor. Differential scanning calorimetry analysis of the resultant polyethylene revealed a large difference between crystallinities at the first and second heating cycles, indicating that the synthesized polyethylene is of low entanglement.

Molecular Bottlebrush Supported Mono(phenoxy–imine) Metal Complexes: Synthesis and Ethylene Polymerization

“…Synthesis of norbornenyl macromonomer and the MB, postmodification of MBs, and preparation of MB supported catalysts and molecular catalysts were performed according to the literatures with some modifications. Details on the synthesis and the characterization data are provided in the Supporting Information.…”

“…In our recent work, we obtained bimodal PEs by using a pressure-sensitive phenoxy− imine titanium catalyst supported by polystyrene nanoparticles. 29 Herein we report a poly(norbornene-graf t-styrene) (PNB-g-PS) immobilizing mono(phenoxy−imine) catalysts (FI catalysts) for ethylene polymerization. The MB has a tunable elongated shape and can be easily controlled over the characteristics of the bottlebrush structure and side-chain functionality (Figure 1).…”

“…They uncovered the mechanism of cooperative catalysis among multiple Ti centers that were confined in a nanosized random coil of PNB chains. In our recent work, we obtained bimodal PEs by using a pressure-sensitive phenoxy–imine titanium catalyst supported by polystyrene nanoparticles …”

Straightforward Design for Phenoxy-Imine Catalytic Activity in Ethylene Polymerization: Theoretical Prediction

“…2 4 0 activity (4) where M(C2H4) and p(C2H4) denote the molecular weight and the pressure of ethylene, respectively; CTi is the initial concentration of a catalyst, τ is polymerization time, and Wp(t) is the propagation rate given by:…”

“…As an inexpensive material, polyethylene (PE) has drawn significant attention due to its excellent physical properties, such as high mechanical strength, high elasticity and high resistivity towards corrosion, light weightness, and reusability [1][2][3][4]. Normally, the polyethylene materials are prepared via the coordination polymerization using different categories of catalysts, among which metallocenes are very promising candidates that provide high activity and selectivity [5][6][7][8][9][10][11].…”