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Shear-induced concentration fluctuations and form factor changes in polymer solution in the good-solvent regime
1Laboratoire de spectrométrie physique, CERMO, UJF-CNRS UMR 5588, F-38402, Saint Martin d'Héres, France. isabelle.morfin@ujf-grenoble.fr
The European Physical Journal. E, Soft Matter
|October 14, 2004
Summary
Sheared polymer solutions exhibit unique flow behavior. Concentration fluctuations increase with flow, and scattering patterns saturate under high shear, aligning with advanced polymer physics models.
Area of Science:
- Polymer Physics
- Rheology
- Scattering Techniques
Background:
- Previous studies on sheared polymer solutions were primarily in the theta-solvent regime.
- Light and neutron scattering experiments in the theta regime showed different behaviors compared to the good-solvent regime.
Purpose of the Study:
- To investigate the behavior of concentration fluctuations and form factors in sheared semidilute polymer solutions in a good-solvent regime.
- To compare these findings with existing theoretical models, particularly Convective Constraint Release (CCR) models.
Main Methods:
- Small-Angle Scattering (SAS) was employed to study the polymer solution.
- The Zero Average Contrast (ZAC) technique was utilized to measure the form factor.
Main Results:
- Concentration fluctuations increased along the flow direction at low scattering vector q.
- Unlike theta-solvent results, no phase separation (demixing) was observed at higher shear rates.
- Scattering effects and the form factor showed saturation above a Weissenberg number of approximately 5, reaching a deformation ratio of 2.
- These phenomena exhibited time-temperature superposition.
Conclusions:
- The observed scattering behavior and saturation effects in the good-solvent regime are consistent with Convective Constraint Release (CCR) models.
- The findings validate theoretical extensions of CCR models that predict rheological and scattering properties in the non-Newtonian regime.