Colloidal-rods for examining polymer dynamics in complex flows

在2022财年，完成了在稳定剪切流动下测量胶体棒在不同聚合物溶液中的排列的实验。测试不同的聚合物溶液，我们已经能够得出结论，聚合物动力学控制着剪切诱导胶体棒排列的开始。具体地说，棒对齐的控制参数是聚合物溶液的魏森伯格数，它量化了聚合物对外加流动的弹性响应。此外，我们发现，胶体棒并不将周围的聚合物溶液视为连续介质，而是类似于离散介质，并且胶体棒遵循与周围聚合物溶液无关的普遍排列趋势。这部分工作已经圆满完成，并发表在《高分子2022-55-13》上。在2022财年，我们还对蠕虫状嵌段共聚物的流动动力学进行了实验研究。我们发现剪切和拉伸流动导致了蠕虫状嵌段共聚物的取向。然而，我们发现伸展变形比剪切变形更能有效地触发蠕虫状颗粒的排列。我们根据颗粒的延展性和灵活性解释了剪切变形和拉伸变形在排列上的差异。该项目的这些部分已经成功完成，并发表在《大分子2022-55-22》上。

In FY2022, experiments were completed measuring the alignment of colloidal rods in different polymer solutions under steady shear flows. Testing different polymer solutions, we have been able to conclude that the polymer dynamics govern the onset of shear-induced alignment of colloidal rods. Specifically, the control parameter for the alignment of rods is the Weissenberg number of the polymer solution, quantifying the elastic response of the polymer to an imposed flow. Additionally, we find that the colloidal rods do not perceive the surrounding polymer solution as a continuous medium, but rather like a discrete medium and that the colloidal rods follow a universal trend of alignment that is independent of the surrounding polymer solution. These part of the project has been successfully completed and published in Macromolecules 2022-55-13.In FY2022 we have also conducted experiments on the flow dynamics of worm-like block copolymers. We show that shear and extensional flows induce the alignment of the worm-like block copolymers. However, we find that extensional deformations are more effective than shear deformations at triggering the onset of alignment of the worm-like particles. We explain the difference in alignment between shear and extensional deformations based on the particle extensibility and flexibility. These part of the project has been successfully completed and published in Macromolecules 2022-55-22.