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(60) Production(s) de l'année 2019
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Coupling Space-Resolved Dynamic Light Scattering and Rheometry to Investigate Heterogeneous Flow and Nonaffine Dynamics in Glassy and Jammed Soft Matter
Auteur(s): Pommella A., Philippe A. M., Phou T., Ramos L., Cipelletti L.
(Article) Publié:
Physical Review Applied, vol. 11 p.034073 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-03029048_v1
Ref Arxiv: 1809.00506
DOI: 10.1103/PhysRevApplied.11.034073
WoS: 000462959200003
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
2 Citations
Résumé: We present a new light scattering setup coupled to a commercial rheometer operated in the plate-plate geometry. The apparatus allows the microscopic dynamics to be measured, discriminating between the contribution due to the affine deformation and additional mechanisms, such as plasticity. Light backscattered by the sample is collected using an imaging optical layout, thereby allowing the average flow velocity and the microscopic dynamics to be probed with both spatial and temporal resolution. We successfully test the setup by measuring the Brownian diffusion and flow velocity of diluted colloidal suspensions, both at rest and under shear. The potentiality of the apparatus are explored in the startup shear of a biogel. For small shear deformations, $\gamma \le 2\%$, the rheological response of the gel is linear. However, striking deviations from affine flow are seen from the very onset of deformation, due to temporally and spatially heterogeneous rearrangements bearing intriguing similarities with a stick-slip process.
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Introduction to the determination of nanostructures by small-angle scattering
Auteur(s): Oberdisse J.
Conférence invité: Dodynet advanced module (DSM) (Kasteel Vaalsbroek, NL, 2019-01-30)
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Deuteration-Induced Volume Phase Transition Temperature Shift of PNIPMAM Microgels
Auteur(s): Cors M., Wiehemeier Lars, Oberdisse J., Hellweg Thomas
(Article) Publié:
Polymers, vol. 11 p.620 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02092623_v1
DOI: 10.3390/polym11040620
WoS: 000467312900049
Exporter : BibTex | endNote
5 Citations
Résumé: The effect of deuteration on the volume phase transition (VPT) temperature of poly (N-isopropylmethacrylamide) (pNIPMAM) microgels in aqueous suspension is determined via IR spectroscopy and size measurements by photon correlation spectroscopy (PCS). We study the effect of a hydrogenated and a deuterated solvent ($H_{2}O/D_{2}O), and of the hydrogenated and (partially) deuterated monomer. Deuteration of the monomer or copolymerization with deuterated monomers shifts the volume phase transition temperature (VPTT) by up to 8.4 K to higher temperatures, in good agreement with known results for pNIPAM microgels. Moreover, the shape of the swelling curve is found to depend on deuteration, with the highest deuteration leading to the sharpest VPT. Finally, the quantitative agreement between FTIR spectroscopy and PCS evidences the spatial homogeneity of the microgel particles. Our results are rationalized in terms of the effect of deuteration on hydrogen bonding. They shall be of primary importance for any experimental measurements close to the VPT involving isotopic substitution, and in particular contrast variation small angle neutron scattering.
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Mucus Microrheology Measured on Human Bronchial Epithelium Culture
Auteur(s): Jory M., Bellouma Karim, Blanc C., Casanellas Vilageliu L., Petit Aurelie, Reynaud Paul, Vernisse Charlotte, Vachier Isabelle, Bourdin Arnaud, Massiera G.
(Article) Publié:
Frontiers In Physics, vol. 7 p.19 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02025486_v1
DOI: 10.3389/fphy.2019.00019
WoS: WOS:000459130800002
Exporter : BibTex | endNote
1 Citation
Résumé: We describe an original method to measure mucus microrheology on human bronchial epithelium culture using optical tweezers. We probed rheology on the whole thickness of mucus above the epithelium and showed that mucus gradually varies in rheological response, from an elastic behavior close to the epithelium to a viscous one far away. Microrheology was also performed on mucus collected on the culture, on ex vivo mucus collected by bronchoscopy, and on another epithelium model. Differences are discussed and are related to mucus heterogeneity, adhesiveness and collection method.
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Rotational diffusion of partially wetted colloids at fluid interfaces
Auteur(s): Stocco A., Chollet B., Wang X., Blanc C., Nobili M.
(Article) Publié:
Journal Of Colloid And Interface Science, vol. 542 p.363-369 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02024615_v1
DOI: 10.1016/j.jcis.2019.02.017
WoS: 000461536400040
Exporter : BibTex | endNote
10 Citations
Résumé: Hypothesis: Rotational Brownian diffusions of colloidal particles at a fluid interface play important roles in particle self-assembly and in surface microrheology. Recent experiments on translational Brownian motion of spherical particles at the air-water interface show a significant slowing down of the translational diffusion with respect to the hydrodynamic predictions (Boniello et al., 2015). For the rotational diffusions of partially wetted colloids, slowing down of the particle dynamics can be also expected.Experiments: Here, the rotational dynamics of Janus colloids at the air-water interface have been experimentally investigated using optical microscopy. Bright field and fluorescent microscopies have been used to measure the in-plane and out-of-plane particle rotational diffusions exploiting the Janus geometry of the colloids we fabricated.Findings: Our results show a severe slowing down of the rotational diffusion Dr,⊥ connected to the contact line motion and wetting-dewetting dynamics occurring on particle regions located at opposite liquid wedges. A slowing down of the particle rotational diffusion about an axis parallel to the interfacial normal Dr,|| was also observed. Contact line fluctuations due to partial wetting dynamics lead to a rotational line friction that we have modelled in order to describe our results.
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