Aiguo Sui,Xincui Shi,Shupeng Wu,Hongkun Tian,Yanhou Geng,Fosong Wang
A new catalyst system, i.e., nickel acetylacetonate/1,3-bis(diphenylphosphino)propane (Ni(acac)2/dppp), was explored to catalyze the Kumada catalyst transfer polycondensation (KCTP) of three fluorene monomers with different substituents at 9-position. The “living” nature of the polymerization was confirmed by polymerization kinetic studies, “monomer addition” experiment and block copolymerizations. As a result, poly(9,9-dioctylfluorene)s (PF8s) with the number-average molecular weights (Mns) in the range 2.8–62.2 kDa and polydispersity indices (PDIs) of ∼1.20 were successfully synthesized in a controlled manner. The syntheses of fluorene-fluorene and fluorene-thiophene diblock copolymers with Mns up to 46 kDa were also demonstrated. A complex, i.e. Ni(dppp)(acac)2, with an octahedral coordination geometry was isolated and confirmed by X-ray crystallographic analysis. The polymerization experiments indicated that the in situ formed Ni(dppp)(acac)2 should be the active catalyst. To the best of our knowledge, this is the first report on the controlled synthesis of polyfluorenes (PFs) via KCTP.
Antony Rajendran,Tian-You Cui,Hong-Xia Fan,Meng-Yu Wang,Wen-Ying Li
A straightforward hydrothermal synthesis of NiMoS active phases loaded on SBA-15 was attempted. We initially prepared a catalyst by impregnating metal precursors sequentially onto SBA-15 and the subsequent hydrothermal treatment with sublimed sulfur. To obtain the one-pot catalyst, we performed the hydrothermal treatment of a mechanical mixture containing metal precursors, sublimed sulfur, and SBA-15. The catalysts were characterized by powder X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, N 2 adsorption-desorption study, and high-resolution transmission emission spectroscopy . Compared to impregnation-assisted synthesis, the one-pot synthesis promoted the generation of dispersed shorter MoS 2 slabs with desirable average stacking number, i.e., increased number of edge and rim sites. Therefore, the one-pot catalyst enabled the ultra-deep sulfur removal (~100%) in the dibenzothiophene hydrodesulfurization . Unlike Ni(acac) 2 , the utilization of Ni(NO 3 ) 2 inhibits the sulfidation of molybdenum and the dispersion of MoS 2 layers, decreasing the hydrodesulfurization activity. The one-pot catalyst was able to achieve ~80% sulfur removal even after six consecutive catalytic runs under batch reactor conditions (320 °C, 6 MPa (H 2 ), 500 ppmw S, 100 mg (m cat )) due to the persistent stability of NiMoS active phases.
Jianwei Li,Wei Chu,Qiang Gao,Hongming Zhang,Xinhai He,Bin Wang
Carbon-based materials have been recognized as a promising method to eliminate electromagnetic interference (EMI) shielding and electromagnetic (EM) wave absorption. However, developing lightweight, ultrathin, and efficient EM wave-shielding and wave-absorbing materials remains a challenge. Herein, a series of magnetic porous carbon composite films with a hierarchical network structure were fabricated via pyrolysis of porous polyimide (PI) films containing magnetic metallic salts of Fe(acac)3 and Ni(acac)2. After pyrolysis, the obtained uniform porous carbon films (CFs) possess a favorable EMI-shielding efficiency (SE) of 46 dB in the X-band with a thickness of ∼0.3 mm. In addition, a higher EMI SE of 58 dB can be achieved by increasing the thickness of the porous CF-20Ni to 0.53 mm. Moreover, the CF-20Ni composites also present effective EM wave-absorbing performance of RLmin = – 30.2 dB with a loading amount of 20 wt % at 13.0 GHz owing to the hierarchically conductive carbon skeleton, magnetic Ni nanoparticles, and dielectric interlaced carbon nanotube cluster within the micropores. These novel lightweight and ultrathin porous CFs are expected to be attractive candidates for efficient EM wave absorption and EMI shielding.
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