Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University , Utrecht 3584 CH, The Netherlands.
Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University , Utrecht 3484 CC, The Netherlands.
Langmuir. 2017 Apr 4;33(13):3270-3280. doi: 10.1021/acs.langmuir.7b00014. Epub 2017 Mar 22.
In this paper, we demonstrate the stabilization of polystyrene microspheres by encapsulating them with dumbbell-shaped colloids with a sticky and a nonsticky lobe. Upon adding a depletant, an effective short ranged attraction is induced between the microspheres and the smaller, smooth lobes of the dumbbells, making those specifically sticky, whereas the interaction with the larger lobes of the dumbbells is considerably less attractive due to their rough surface, which reduces the overlap volume and leaves them nonsticky. The encapsulation of the microspheres by these rough-smooth patchy dumbbells is investigated using a combination of experiments and computer simulations, both resulting in partial coverage of the template particles. For larger microspheres, the depletion attraction is stronger, resulting in a larger fraction of dumbbells that are attached with both lobes to the surface of microspheres. We thus find a template curvature dependent orientation of the dumbbells. In the Monte Carlo simulations, the introduction of such a small, curvature dependent attraction between the rough lobes of the dumbbells resulted in an increased coverage. However, kinetic constraints imposed by the dumbbell geometry seem to prevent optimal packing of the dumbbells on the template particles under all investigated conditions in experiments and simulations. Despite the incomplete coverage, the encapsulation by dumbbell particles does prevent aggregation of the microspheres, thus acting as a colloid-sized steric stabilizer.
本文通过用两端带有粘性和非粘性叶瓣的哑铃型胶体包裹聚苯乙烯微球来实现其稳定。加入耗尽剂后，微球与哑铃较小的、光滑的叶瓣之间会产生有效的短程吸引力，使这些叶瓣具有粘性，而与哑铃较大叶瓣之间的相互作用由于其粗糙的表面而具有较小的吸引力，这会减少重叠体积并使它们不具有粘性。通过实验和计算机模拟的组合研究了这些粗糙-光滑嵌段哑铃对微球的包裹，这两种方法都导致模板颗粒的部分覆盖。对于较大的微球，耗尽吸引力更强，导致更多的哑铃以两个叶瓣附着在微球表面。因此，我们发现哑铃具有模板曲率依赖性的取向。在蒙特卡罗模拟中，在哑铃的粗糙叶瓣之间引入这种小的、曲率依赖的吸引力，导致覆盖率增加。然而，由哑铃几何形状引起的动力学限制似乎在实验和模拟中所有研究条件下都阻止了哑铃在模板颗粒上的最佳堆积。尽管覆盖不完全，但哑铃颗粒的包裹确实可以防止微球聚集，从而起到胶体尺寸的空间位阻稳定剂的作用。
