![]() ![]() ![]() Sol-gel transition of cellulose/tetrabutylammonium acetate/dimethyl sulfoxide solutions with different water concentrations.īacterial suspensions-a premier example of active fluids-show an unusual response to shear stresses. Meanwhile, a mechanism of cellulose aggregation and the sol–gel transitions have been proposed: water can effectively break the cellulose–Ac⁻ H-bonds and lead to the formation of cellulose–cellulose H-bonds, which grow the aggregation of cellulose, form a network structure in the whole sample and then result in gelation. We explain the sol–gel transformation in cellulose/TBAA/DMSO/water solutions by percolation theory. The Cox–Merz rule and Cross model have been used to fit the rheological data. With the water concentrations increased, a sol–gel transition had been detected. Specifically, the rheological behaviours of distinct phases formed in 6–8%(w/w) cellulose/TBAA/DMSO solutions due to the addition of water was investigated. A non-solvent (water) post-added to the cellulose/TBAA/DMSO solutions caused significant changes in flow properties. However, if water or other hydrogen bond donors are present, the solvent's ability to dissolve cellulose is greatly reduced. Tetrabutylammonium acetate (TBAA) solution in dimethyl sulfoxide (DMSO) can dissolve cellulose efficient at a mild condition and it seems to have favorable properties for cellulose molding applications, e.g. We hypothesize that the unusual particle dynamics arise from localized shear-induced chain disentanglement. ![]() We further characterize the length and time scales associated with the abnormal dynamics of tracer particles. The probability distribution functions of particle displacements follow a power-law scaling at large displacements, indicating a Levy-walk-type motion, reminiscent of tracer dynamics in entangled wormlike micelle solutions and sheared colloidal glasses. Surprisingly, tracer particles in the shear frame exhibit transient super-diffusivity and strong dynamic heterogeneity. To investigate the microscopic origin of the observed shear banding, we study the dynamics of micron-sized tracers embedded in DNA solutions. With increasing Weissenberg number (Wi), we observe successive transitions from normal Newtonian linear shear profiles to wall-slip dominant shear profiles and finally to shear-banding profiles at high Wi. Using high-resolution confocal rheometry, we study the shear profiles of well-entangled DNA solutions under large amplitude oscillatory shear (LAOS) in a rectilinear planar shear cell. ![]()
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