Concentration regimes in salt-free aqueous xanthan solutions under shear
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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2026
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| author | Menayyir, Ammar El Neuner, Markus Fuks, Polina Alashloo, Vahid A. Z. Altuntas, Halim Luo, Zehau Özgül, Melike Seeberger, Claudia Pan, Sharadwata Wierschem, Andreas |
| author_facet | Menayyir, Ammar El Neuner, Markus Fuks, Polina Alashloo, Vahid A. Z. Altuntas, Halim Luo, Zehau Özgül, Melike Seeberger, Claudia Pan, Sharadwata Wierschem, Andreas |
| contents | Concentration regimes in polymer and polyelectrolyte solutions can be identified by scaling laws for the relation between specific zero-shear viscosity and concentration. Recently, we have shown that the same is true for the infinite-shear viscosity plateau. The shear-thinning range is usually accessed by focusing on the viscosity functions for the respective concentration regime. For salt-free aqueous xanthan solutions, we find power-law dependencies of the specific viscosity on concentration throughout the entire shear-rate range. We distinguish six different concentration regimes. Apart from those already known for the zero-shear viscosity of polyelectrolyte solutions, i.e. dilute, semidilute unentangled, semidilute entangled and neutral semidilute entangled, we identify a linear regime for low shear rates at high concentrations, where the solution gels and a regime at both, higher concentrations and higher shear rates. Within some regimes, the power-law exponents change smoothly with shear rate, particularly, when deviating from the zero-shear viscosity plateau before the power-law of the viscosity function. Some regimes merge as their power-law exponents approach each other. The fact that the regimes extend smoothly from the zero-shear regime into finite shear rates, i.e. away from thermodynamic equilibrium, shows that indicators such as critical concentrations remain valid at finite shear rates. This motivates us to interpret the data in the light of existing scaling laws and current knowledge about shear-rate dependent interaction mechanisms in polyelectrolyte solutions, particularly in xanthan solutions. It allows to follow the shift of relevant interaction mechanisms with shear rate. We think that the consideration of scaling laws under shear can be particularly helpful for identifying, for instance, thresholds for shear-induced disentanglement or disaggregation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_10211 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Concentration regimes in salt-free aqueous xanthan solutions under shear Menayyir, Ammar El Neuner, Markus Fuks, Polina Alashloo, Vahid A. Z. Altuntas, Halim Luo, Zehau Özgül, Melike Seeberger, Claudia Pan, Sharadwata Wierschem, Andreas Soft Condensed Matter Fluid Dynamics Fluid Mechanics Concentration regimes in polymer and polyelectrolyte solutions can be identified by scaling laws for the relation between specific zero-shear viscosity and concentration. Recently, we have shown that the same is true for the infinite-shear viscosity plateau. The shear-thinning range is usually accessed by focusing on the viscosity functions for the respective concentration regime. For salt-free aqueous xanthan solutions, we find power-law dependencies of the specific viscosity on concentration throughout the entire shear-rate range. We distinguish six different concentration regimes. Apart from those already known for the zero-shear viscosity of polyelectrolyte solutions, i.e. dilute, semidilute unentangled, semidilute entangled and neutral semidilute entangled, we identify a linear regime for low shear rates at high concentrations, where the solution gels and a regime at both, higher concentrations and higher shear rates. Within some regimes, the power-law exponents change smoothly with shear rate, particularly, when deviating from the zero-shear viscosity plateau before the power-law of the viscosity function. Some regimes merge as their power-law exponents approach each other. The fact that the regimes extend smoothly from the zero-shear regime into finite shear rates, i.e. away from thermodynamic equilibrium, shows that indicators such as critical concentrations remain valid at finite shear rates. This motivates us to interpret the data in the light of existing scaling laws and current knowledge about shear-rate dependent interaction mechanisms in polyelectrolyte solutions, particularly in xanthan solutions. It allows to follow the shift of relevant interaction mechanisms with shear rate. We think that the consideration of scaling laws under shear can be particularly helpful for identifying, for instance, thresholds for shear-induced disentanglement or disaggregation. |
| title | Concentration regimes in salt-free aqueous xanthan solutions under shear |
| topic | Soft Condensed Matter Fluid Dynamics Fluid Mechanics |
| url | https://arxiv.org/abs/2604.10211 |