Colloidal-rods for examining polymer dynamics in complex flows

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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.