In this paper, hollow nanospheres (HNSs) of metal oxides (NiO, CuO, and NiO/CuO) coated with a porous carbon shell (HNSs@C) with good structural stability were successfully prepared on the basis of the nanoscale Kirkendall effect. The formation process was based on a template-free method, and the as-prepared HNSs@C are very clean compared with products of the template process. In addition, the results of N adsorption-desorption noted that both the metal oxide HNSs and the coated carbon were mesoporous structures. Therefore, small molecules can access the inner space of the whole HNSs@C, which was expected to increase the active site area and to show better performances in applied fields, such as catalysts and sensors. As an example of the functional properties, the obtained HNSs@C were investigated as the catalyst for the hydrogenation of 4-nitrophenol (4-NP) and manifested highly catalytic activity and excellent stability. This work has opened up a novel route for the development of metal oxide HNSs nanocatalysts. This straightforward method is of significance for development of clean metal oxide HNSs with high stability and multiplied applications.
ABSTRACT:The sequential block copolymerization of styrene (St) and butadiene (Bd) was carried out with an activated rare earth catalyst composed of catalyst neodymium tricarboxylate (Nd), cocatalyst Al(i-Bu) 3 (Al), and chlorinating agent (Cl). The microstructure, composition, and morphology of the copolymer were characterized by FTIR, 1 H NMR, 13 C NMR, and TEM. The results show that styrenebutadiene diblock copolymer with high cis-1,4 microstructure of butadiene units ( 97 mol %) was synthesized. The cis-selectivity for Bd units was almost independent on the content of styrene units in the copolymer ranging from 18.1 mol % to 29.8 mol %. The phase-separated morphology of polystyrene (PS) domains of about 40 nm tethered by the elastomeric polybutadiene (PB) segments is observed. The PS-b-cis-PB copolymer could be used as an effective compatilizer for noncompatilized binary PS/cis-PB blends.
The cationic polymerizations of isobutylene (IB) initiated by the H2O/TiCl4 in dichloromethane (CH2Cl2) at −30 °C were carried out in the absence and presence of various external electron
pair donors (EDs). Controlled polymerization with a slow polymerization rate and a narrow molecular
weight distribution (MWD, M
w/M
n = 1.11−1.28) of the polymer was achieved by using certain appropriate
H2O/TiCl4/ED systems. The kinetics of the IB polymerization with the H2O/TiCl4/ED initiating system
was investigated. It indicated that the polymerization rate was first-order with respect both to monomer
and to initiator concentrations in the presence of strong or weak EDs. Polymerizations exhibited a second-order dependence on TiCl4 concentration in those cases where weak EDs, such as methyl acetate (MAC),
methyl acrylate (MA), sulfolane (HDF), or methyl benzoate (MB), were used. On the other hand, first
order in TiCl4 concentration was observed when strong EDs, such as dimethylacetamide (DMA), dimethyl
sulfoxide (DMSO), pyridine (Py), or triethylamine (TEA), were used.
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