Preparation And Applications Of High Internal Phase Emulsion Stabilized By Single-chain Polymer Nanoparticles

High internal phase Pickering emulsions(Pickering HIPE) refers to emulsions that internal phase volume fraction are more than 74% and stabilized by nanoparticles or micron particles. Because of the advantages of economy and environmental protection compared to traditional emulsion, Pickering HIPE had made great development in recent years, and were applied to the field of medicine, food, coating industry and fine chemical industry. When the external phase contains polymerizable monomers, polymer of high internal phase emulsions(PolyHIPE) with a cellular structure, termed PolyHIPE, could be obtained by first polymerizing the continuous external phase and then removing the internal dispersed. Due to its well versed in porous and controllable structure, PolyHIPE has wide application in preparation of catalysts. This study use cross-linking single chain polymer nanoparticles as stabilizer, polymerizable monomers as continues phase, prepared Pickering HIPE. Then used it as template, polymerizing the continuous external phase and get PolyHIPE. Used the PolyHIPE as carrier, made two kind of catalysts. The main contents of this study are summarized as following:(1) The preparation of styrene/divinylbenzene-based macrocellular polymers of high internal phase emulsions PolyHIPE with interconnected open-cell structure as well as their application as support for Pd nanoparticles are presented. Firstly, water in oil high internal phase emulsions HIPE were generated by adding the water stepwise to the oil phase(styrene and divinylbenzene) containing Janus polymer nanoparticles that consist of a linear poly(methyl methacrylate) “tail” and a cross-linked poly(4-vinylpyridine) “head”. The generated water in oil HIPE stabilized solely by Janus polymer nanoparticles were then converted to PolyHIPE foams by polymerizing the external continuous oil phase, followed by the extraction with methanol and the drying under the reduced press. Scanning electron microscopy observation revealed that the as-produced macrocellular PolyHIPE were foam structure with closed and/or partially open-cells. Partial cells covered by a thin polymer film were peeled off during the post-treatment. Some key factors influencing the PolyHIPE morphologies, including emulsifier particles content, the mole ratio of styrene to divinylbenzene and the internal phase volume fraction were investigated, and macrocellular PolyHIPE with interconnected open-cell morphologies could be achieved under optimal conditions. Benefited from the strong interaction between the emulsifier particles embedded in the PolyHIPE and H2PdCl4 precursor, Pd nanoparticles were facilely supported in situ within the macrocellular PolyHIPE without any functional monomers or post-functionalization requirement. The obtained Pd@macrocellular polymer hybrid foams were then applied for the heterogeneous Suzuki–Miyaura carbon–carbon coupling reactions between iodobenzene and benzeneboronic acid, and a high catalytic activity with a good recyclability were demonstrated.(2) Nitrogen- and oxygen-codoped porous carbonaceous foam templated from high internal emulsion as PtRu catalyst support for direct methanol fuel cell. Janus nanoparticles stabilized water-in-acrylonitrile/divinyl benezene high internal phase emulsion(HIPE) was firstly prepared, and the formed HIPE was then converted into PolyHIPE through a radical polymerization reaction. Subsequently, the formed acrylonitrile/divinyl benezene based PolyHIPE was hypercrosslinked via FeCl3 catalyzed Friedel-Crafts reaction in 1,2-dichloroethane. After pyrolysis of the hypercrosslinked polyHIPE at elevated temperature under N2 atmosphere, nitrogen- and oxygen-codoped porous carbonaceous foam exhibiting highly interconnected macroporous cells and a micro-/mesoporous carbon skeleton named carboHIPE was obtained. The resultant carboHIPE was further applied as the support for Pt and Ru bimetal nanoparticles. Well-dispersed PtRu bimetal nanoparticles with a smaller size were perfectly dispersed on the surface of carboHIPE in the form of alloy phase. The PtRu alloy nanoparticles decorated carboHIPE(PtRu/carboHIPE) demonstrated superior electrocatalytic performances towards the methanol electrooxidation by comparison with Pt/carboHIPE and commercial PtRu/C exhibiting almost same Pt content, such as the higher current density, the better long term stability and the improved CO-resistance.