Palladium-Catalyzed Synthesis of Norbornene-Based Polar-Functionalized Polyolefin Elastomers

Light, Heat, and Force-Responsive Polyolefins

Stimuli-responsive polymers have found applications as shape-memory materials, optical switches, and sensors, but the installation of these responsive properties in non-polar and inert polyolefins is challenging. In this contribution, a series of spiropyran (SP)-based comonomers are synthesized and copolymerized with ethylene or ethylene/cyclic monomers. In addition to great mechanical and surface properties, these functionalized polyolefins responded to light, heat, and force, which induced changes in the polymer structure to transmit color or mechanical signals. These interesting responsive properties are also installed in a series of commercial polyolefin materials through reactive extrusion, making the scalable production of these materials possible.

Influence of the Ethanol Content of Adduct on the Comonomer Incorporation of Related Ziegler-Natta Catalysts in Propylene (Co)polymerizations

The aim of this work is to investigate the influence of the ethanol content of adducts on the catalytic behavior of related Ziegler-Natta (ZN) catalysts in propylene homo- and copolymerizations (with 1-hexene comonomer) in terms of activity, isotacticity, H2 response, and comonomer incorporation. For this purpose, three MgCl2.nEtOH adducts with n values of 0.7, 1.2, and 2.8 were synthesized and used in the synthesis of related ZN catalysts. The catalysts were thoroughly characterized using XRD, BET, SEM, EDX, N2 adsorption-desorption, and DFT techniques. Additionally, the microstructure of the synthesized (co)polymers was distinguished via DSC, SSA, and TREF techniques. Their activity was found to enhance with the adduct's ethanol content in both homo- and copolymerization experiments, and the increase was more pronounced in homopolymerization reactions in the absence of H2. Furthermore, the catalyst with the highest ethanol content provided a copolymer with a lower isotacticity index, a shorter meso sequence length, and a more uniform distribution of comonomer within the chains. These results were attributed to the higher total surface area and Ti content of the corresponding catalyst, as well as its lower average pore diameter, a larger proportion of large pores compared to the other two catalysts, and its spherical open bud morphology. It affirms the importance of catalyst/support ethanol-content control during the preparation process. Then, molecular simulation was employed to shed light on the iso-specificity of the polypropylene produced via synthesized catalysts.

Cyclic Olefin Terpolymers with High Refractive Index and High Optical Transparency

Cyclic olefin copolymer (COC) is one of the most promising optical materials; however, the brittle COC suffers from issues including a low refractive index. In this contribution, by the introduction of high refractive index comonomers including phenoxy substituted α-olefin (C₄OAr), p-tolylthio substituted α-olefin (C₄SAr) and carbazolyl substituted α-olefins (C₄NAr, C₃NAr, and C₂NAr), the zirconocene mediated terpolymerization of ethylene (E) and tetracyclododecene (TCD) produces the preferred E-TCD-C_nNAr (n = 2, 3, and 4) cyclic olefin terpolymers (COT) with tunable compositions (TCD: 11.5- 35.8 mol %, C_nNAr: 1.2-5.0 mol %), high molecular weights and high glass transition temperatures (up to 167 °C) in high catalytic activities. Compared to the E-TCD copolymer (COC) material, these COT materials show the comparable thermal decomposition temperature (T_d,5% = 437 °C), slightly higher strain at break value (up to 7.4%) and higher tensile strength (up to 60.5 MPa). In particular, these noncrystalline optical COT materials have significantly higher refractive indices of 1.550-1.569 and are more transparent (transmittance: 93-95%), relative to the COC materials, indicative of an excellent optical material.

The synthesis and properties research of functionalized polyolefins

This work demonstrated a tandem ROMP/hydrogenation approach for the preparation of functionalized polyolefins and their properties were investigated.

Computational study of the copolymerization mechanism of ethylene with methyl 2-acetamidoacrylate catalyzed by phosphine-sulfonate palladium complexes

In this research, a computational study is carried out to describe the insertion of a vital monomer, methyl 2-acetamidoacrylate (MAAA), into catalyst A (A = [(POOMe,OMe)PdMe]) (POOMe,OMe = 2[2-MeOC6H4](2-SO3-5-MeC6H4)P).