Shear-induced concentration fluctuations and form factor changes in polymer solution in the good-solvent regime.
Small-Angle Scattering from sheared semidilute polymer solution is reported in the good-solvent regime, at variance with former light and neutron measurements in the theta regime. First, concentration fluctuations are observed: the scattering increases noticeably along the flow at low q, but at variance with former results for the theta-solvent regime, no demixing is observed at higher shear. Here, instead, the effects follow a time-temperature superposition and saturate above a Weissenberg number around 5, like the stress which is known to present a plateau for these systems. Using the Zero Average Contrast technique, we have also measured the form factor, which displays the same saturation effect reaching a deformation ratio of the order of 2. These results agree with the Convective Constraint Release models (CCR) elaborated in order to predict the stress effects in the non-Newtonian regime (Marrucci-Ianniruberto) and their extension predicting also the scattering (Likhtman-Milner-McLeish).
Laboratoire de spectrométrie physique, CERMO, UJF-CNRS UMR 5588, F-38402, Saint Martin d'Héres, France. isabelle.morfin@ujf-grenoble.fr
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Morfin
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Lindner
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Boué
D001703:Biophysics / Q000379:methods*; D005583:Fourier Analysis; D009502:Neutrons; D011108:Polymers / Q000737:chemistry*; D012542:Scattering, Radiation; D012997:Solvents / Q000737:chemistry
D011108:Polymers; D012997:Solvents