That is, particles are able to irreversibly attach to the oil–water interface, leading to a more efficient stabilization than surfactant adsorption. Theories that demonstrate the mechanism of stabilization in Pickering emulsions have been proposed, and the commonly accepted one is based on the formation of a steric barrier by solid particles adsorbing at the oil–water interface ( Monegier du Sorbier et al., 2015). It has been demonstrated by many researches that numerous types of inorganic particles including silica, clay, and hydroxyapatite (Hap), as well as some organic particles, can effectively serve as Pickering emulsifiers. It was discovered a century ago, but has recently drawn significant research interests as templates in many fields due to the following advantages: (i) solid particles reduce the possibility of coalescence, bringing about higher stability to emulsions (ii) many solid particles can endow as-prepared materials useful characteristics such as conductivity, responsiveness, porosity, and so on (iii) some food-grade solid particles have lower toxicity, thus leading to higher safety for in vivo usage. Pickering emulsion ( Pickering, 1907) utilizes solid particles alone as stabilizers, which accumulate at the interface between two immiscible liquids (typically denoted as oil and water phase) and stabilize droplets against coalescence. It is commonly known that emulsions can be stabilized by small molecular emulsifiers and some macromolecules, yet some of them may cause allergy-like reactions and carcinogenicity. In this article, we give an overview of Pickering emulsions, focusing on some kinds of solid particles commonly serving as emulsifiers, three main types of products from Pickering emulsions, morphology of solid particles and as-prepared materials, as well as applications in different fields.Įmulsions are widely used in many different fields including pharmaceutics, drug delivery, cosmetics, food industry, and so on, especially after the advancement of methods for preparing various kinds of emulsions. Pickering emulsions can be applied in a wide range of fields, such as biomedicine, food, fine chemical synthesis, cosmetics, and so on, by properly tuning types and properties of solid emulsifiers. Besides, they are more biocompatible when solid particles employed are relatively safe in vivo. Substituting solid particles for traditional surfactants, Pickering emulsions are more stable against coalescence and can obtain many useful properties. Pickering emulsion, a kind of emulsion stabilized only by solid particles locating at oil–water interface, has been discovered a century ago, while being extensively studied in recent decades. 4Department of Neurology, Jinshan Hospital, Fudan University, Shanghai, China.3Zhiyuan College, Shanghai Jiao Tong University, Shanghai, China.2School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.1Department of Neurology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.We report the occurrence of a catastrophic coagulation phenomenon for Pickering emulsion polymerizations carried out at a low initiator (ammonium persulfate) flux at 60 ☌, for a small window of concentrations of Laponite clay discs.Yunqi Yang 1,2,3 Zhiwei Fang 2 Xuan Chen 2 Weiwang Zhang 2 Yangmei Xie 4 Yinghui Chen 4* Zhenguo Liu 1* Weien Yuan 2* Use of increasing amounts leads to smaller average particle sizes but inflicts longer nucleation periods, thereby broadening the particle size distributions. The Laponite clay discs play a crucial role in the particle formation (nucleation) stage of the Pickering emulsion polymerization process. Detailed kinetic studies at both 60 and 80 ☌ of the Pickering emulsion copolymerization of styrene and n-butyl acrylate (Sty:BA = 0.67 w/w) are reported, with varying amounts of Pickering stabilizer. The use of small amounts of methacrylic acid as auxiliary monomer promotes clay adhesion to the surface of the particles in the Pickering emulsion (co)polymerization of hydrophobic monomers. The use of monomers that have high water solubility and are prone to hydrolyze under basic conditions, for example methyl methacrylate, should be restricted. Key mechanistic aspects of the Pickering emulsion polymerization process are discussed. Overall solids contents of the hybrid latexes in complete absence of coagulation of up to 24 wt % are reported under batch conditions. Laponite clay XLS is used as stabilizer in the Pickering emulsion polymerization of a variety of monomer mixtures, that is, methyl methacrylate and n-butyl acrylate, styrene and n-butyl acrylate, and styrene and 2-ethylhexyl acrylate. The fabrication of “soft” nanocomposite clay armored polymer latexes is described.
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