Ji Jing, Shu Shi, Wang Feng, Li Zhilin, Liu Jingjun, Song Ye, Jia Yi
Beijing Key Laboratory of Electrochemical Process and Technology for Materials, Beijing University of Chemical Technology, Beijing 100029, China.
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Nanoscale Res Lett. 2014 Sep 29;9(1):534. doi: 10.1186/1556-276X-9-534. eCollection 2014.
This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles.
这项工作报道了硅溶胶作为Pickering乳液稳定剂多功能性的新证据。硅颗粒在油水界面的排列是成核模型的函数。目前的结果表明，成核模型与单体疏水性一起，可以用作改变硅颗粒在油水界面堆积密度的触发因素：疏水性较低的甲基丙烯酸甲酯更容易被硅颗粒润湿，当通过微乳液聚合制备复合颗粒（单体分批进料，即液滴成核）时，有利于形成核壳结构的复合材料。相比之下，当单体逐滴进料（均相成核）时，疏水性的丙烯酸丁酯会提高硅的包封效率。通过透射电子显微镜（TEM）和扫描电子显微镜（SEM）技术对由不同甲基丙烯酸甲酯/丙烯酸丁酯进料比（具有不同疏水性）和不同进料工艺制备的聚丙烯酸酯-纳米SiO₂复合材料的形态进行了表征。SEM和TEM的结果表明，所制备的聚丙烯酸酯/纳米SiO₂复合材料的形态可以是核壳结构或裸露的丙烯酸球体。由这些复合颗粒组成的乳液的稳定性强烈依赖于硅颗粒的表面覆盖率。硅紧密堆积的复合颗粒可提高乳液稳定性。
