Department of Mechanical Engineering, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, United States.
Department of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States.
J Colloid Interface Sci. 2019 Feb 15;536:30-41. doi: 10.1016/j.jcis.2018.10.028. Epub 2018 Oct 12.
It is possible to control the absolute and relative magnitude of repulsive and attractive interactions and hence microstructure of interfacial particles at and air/water interface by adjusting subphase composition. It should be possible to modify interfacial viscoelasticity from elastic to viscous behavior through these changes to interfacial microstructure.
Particle laden interfaces are made from micron sized polystyrene at an air/water interface. The inter-particle interactions are controlled by the subphase salt concentration and addition of both non-ionic and ionic surfactants. These interfaces are then characterized using an interfacial rheometer with a custom visualization system.
Three distinct microstructures are observed. Low repulsion and high attraction systems exhibit a soft glassy rheology with a disordered but dense microstructure. Creating high repulsion results in a dense hexagonal crystal. Finally, in systems with reduced repulsion and attraction, a hexatic phase can be observed. Each of these microstructures exhibit unique interfacial viscoelastic behavior. These results indicate that control over the properties of these interfaces, and hence Pickering emulsions, is possible through manipulation of interparticle forces.
通过调节亚相组成，可以控制界面粒子在气/水界面处的排斥和吸引相互作用的绝对值和相对大小，以及界面的微观结构。通过这些界面微观结构的变化，应该可以将界面粘弹性从弹性行为改变为粘性行为。
在气/水界面处制备了载有颗粒的界面，其颗粒尺寸为微米级聚苯乙烯。通过亚相盐浓度和添加非离子和离子表面活性剂来控制颗粒间相互作用。然后使用带有定制可视化系统的界面流变仪对这些界面进行了表征。
观察到三种不同的微观结构。低排斥和高吸引体系表现出软玻璃态流变行为，具有无序但致密的微观结构。产生高排斥力会导致形成密集的六方晶体。最后，在排斥力和吸引力降低的体系中，可以观察到准六方相。这些微观结构中的每一种都表现出独特的界面粘弹性行为。这些结果表明，通过操纵颗粒间的相互作用力，可以控制这些界面的性质，从而控制 Pickering 乳液。
