Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany.
Langmuir. 2012 Nov 13;28(45):15770-6. doi: 10.1021/la302974j. Epub 2012 Aug 29.
Responsive microgels are deformable submicrometer cross-linked polymeric hydrogel particles that are used as a novel class of emulsion stabilizers. Their flexibility and the triggering of conformational changes by external stimuli lead to several advantages compared to rigid particles used in conventional Pickering emulsions. Despite their rapidly increasing use, several key aspects relating to microgel microstructure and localization at liquid interfaces are still unexplored. We present here a novel characterization that employs freeze-fracture shadow-casting cryo-SEM to disclose quantitative 3D information on the deformation and protrusion of microgels at water/oil interfaces. Despite the bulk pH response (swelling), we report here the unexpected absence of size and vertical position changes as a function of pH at liquid interfaces and interpret the results using simple arguments that link the particle interfacial activity, solvation, and internal deformation. These results pave the way to a deeper understanding of a novel class of soft materials.
响应性微凝胶是可变形的亚微米交联聚合物水凝胶颗粒，可用作新型乳液稳定剂。与传统 Pickering 乳液中使用的刚性颗粒相比，其灵活性和对外界刺激的构象变化的触发具有几个优势。尽管它们的使用迅速增加，但与微凝胶微观结构和在液体界面处的定位相关的几个关键方面仍未得到探索。我们在这里提出了一种新的表征方法，该方法采用冷冻断裂阴影投射冷冻扫描电子显微镜来揭示水/油界面处微凝胶变形和突出的定量 3D 信息。尽管存在体相 pH 响应（溶胀），但我们在这里报告了在液体界面处，微凝胶的尺寸和垂直位置不会随 pH 变化，并且使用简单的论点来解释结果，这些论点将颗粒的界面活性、溶剂化和内部变形联系起来。这些结果为深入了解一类新型软物质铺平了道路。
