Calabrese Vincenzo, Varchanis Stylianos, Haward Simon J, Shen Amy Q
Okinawa Institute of Science and Technology, Onna-son, Okinawa 904-0495, Japan.
Macromolecules. 2022 Jul 12;55(13):5610-5620. doi: 10.1021/acs.macromol.2c00769. Epub 2022 Jun 29.
Understanding the hydrodynamic alignment of colloidal rods in polymer solutions is pivotal for manufacturing structurally ordered materials. How polymer crowding influences the flow-induced alignment of suspended colloidal rods remains unclear when rods and polymers share similar length scales. We tackle this problem by analyzing the alignment of colloidal rods suspended in crowded polymer solutions and comparing that to the case where crowding is provided by additional colloidal rods in a pure solvent. We find that the polymer dynamics govern the onset of shear-induced alignment of colloidal rods suspended in polymer solutions, and the control parameter for the alignment of rods is the Weissenberg number, quantifying the elastic response of the polymer to an imposed flow. Moreover, we show that the increasing colloidal alignment with the shear rate follows a universal trend that is independent of the surrounding crowding environment. Our results indicate that colloidal rod alignment in polymer solutions can be predicted on the basis of the critical shear rate at which polymer coils are deformed by the flow, aiding the synthesis and design of anisotropic materials.
理解聚合物溶液中胶体棒的流体动力学排列对于制造结构有序材料至关重要。当棒和聚合物具有相似的长度尺度时，聚合物拥挤如何影响悬浮胶体棒的流动诱导排列仍不清楚。我们通过分析悬浮在拥挤聚合物溶液中的胶体棒的排列，并将其与纯溶剂中由额外胶体棒提供拥挤的情况进行比较，来解决这个问题。我们发现聚合物动力学控制着悬浮在聚合物溶液中的胶体棒的剪切诱导排列的起始，并且棒排列的控制参数是魏森贝格数，它量化了聚合物对施加流动的弹性响应。此外，我们表明胶体排列随剪切速率的增加遵循一种普遍趋势，该趋势与周围的拥挤环境无关。我们的结果表明，聚合物溶液中胶体棒的排列可以基于聚合物线圈因流动而变形的临界剪切速率来预测，这有助于各向异性材料的合成和设计。
