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| Home > Publications database > Low Ionic Strength Equilibria of Charged DNA-Rods and Their Bulk Response to Shear Flow |
| Home > Publications database > Low Ionic Strength Equilibria of Charged DNA-Rods and Their Bulk Response to Shear Flow |
| Conference Presentation (After Call) | FZJ-2022-04516 |
2022
Abstract: At sufficiently low ionic strengths (below 1 mM Tris/HCl buffer), long and thin, highly charged colloidal rods (fd-virus particles) exhibit various chiral-mesophases consisting of different orientations of chiral-nematic domains and helical domains, well above the isotropic-nematic coexistence concentration [1,2]. In addition, a glass transition has been observed, where the particle dynamics within nematic domains as well as the dynamics of the domain texture are dynamically arrested at the same glass-transition concentration [3-5]. Such a glass transition only occurs for sufficiently low ionic strengths, and is therefore attributed to caging of particles due to relatively long-ranged electrostatic interactions. After a short discussion of low ionic strength equilibria of suspensions of charged DNA-Rods (fd), experiments on the bulk response of such rod-glasses of charged DNA-rods to shear flow will be presented. Depending on the applied shear rate, various inhomogeneous flow profiles are observed, where the flow velocity varies along the gradient direction and/or the vorticity direction. Fracture and plug flow as observed at low shear rates, gradient-shear-banding at intermediate shear rates, and a linear profile at sufficiently high shear rates [6]. There is a shear rate-rate range where these flow profiles coexist with Taylor vorticity bands [6-8]. Plug flow is most probably due to the brittle nature of the sample, consisting of elastic glassy nematic domains. The mechanism for gradient-shear-banding in these systems with a soft, long-ranged repulsive inter-particle potential, is shown to be due to the classic gradient-banding scenario related to strong shear-thinning behaviour [7]. There is a subtle interplay between the stress originating from inter-particle interactions within the domains and the texture stress due to inter-domain interactions [7]. References: [1] Scientific Reports 11, 3472 (2021), [2] J. Phys. Commun, 6, 015001 (2022) [3] Phys. Rev. Lett. 110, 015901 (2013) [4] Soft Matter 9, 4401 (2013) [5] Soft Matter 10, 3311 (2014) [6] Phys. Rev. Fluids 2, 043301 (2017) [7] J. Rheol. 66, 2, March 1st (2022) [8] J. Phys. Commun. 5, 045011 (2021)
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