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(254) Production(s) de RAMOS L.
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Investigation of the Slow Dynamic of a Soft Glass by Light Microscopy
Auteur(s): Ramos L.
(Séminaires)
Levich Institute, City College of New-York (New-York, USA, FR), 2008-06-04 |
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Etude dans l'espace direct de la dynamique lente et non stationnaire d'un verre mou
Auteur(s): Ramos L.
(Séminaires)
Laboratoire de physique Lyon (Lyon, France, FR), 2008-12-09 |
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Swollen Hexagonal Phases: From the Physics of Yield Stress Fluids to the Chemistry of Materials
Auteur(s): Ramos L.
(Séminaires)
New-York (New-York, US), 2007-06-21 |
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Linear viscoelasticity of entangled wormlike micelles bridged by telechelic polymers : an experimental model for a double transient network 
Auteur(s): Nakaya Kaori, Ramos L., Tabuteau Hervé, Ligoure C.
(Article) Publié:
Journal Of Rheology / Transactions Of The Society Of Rheology; Society Of Rheology -- Transactions, vol. 52 p.359-377 (2008)
Texte intégral en Openaccess : 
Ref HAL: hal-00129044_v1
Ref Arxiv: cond-mat/0702102
DOI: 10.1122/1.2828645
WoS: 000253761800002
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
34 Citations
Résumé: We survey the linear viscoelasticity of a new type of transient network: bridged wormlike micelles, whose structure has been characterized recently [Ramos and Ligoure, (2007)]. This composite material is obtained by adding telechelic copolymers (water-soluble chains with hydrophobic stickers at each extremity) to a solution of entangled wormlike micelles (WM). For comparison, naked WM and WM decorated by amphiphilic copolymers are also investigated. While these latter systems exhibit almost a same single ideal Maxwell behavior, solutions of bridged WM can be described as two Maxwell fluids components blends, characterized by two markedly different characteristic times, t_fast and t_slow, and two elastic moduli, G_fast and G_slow, with G_fast >> G_slow. We show that the slow mode is related to the viscoelasticity of the transient network of entangled WM, and the fast mode to the network of telechelic active chains (i.e. chains that do not form loops but bridge two micelles). The dependence of the viscoelasticity with the surfactant concentration, phi, and the sticker-to-surfactant molar ratio, beta, is discussed. In particular, we show that G_fast is proportional to the number of active chains in the material, phi beta. Simple theoretical expectations allow then to evaluate the bridges/loops ratio for the telechelic polymers.
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Investigation of $q$-dependent dynamical heterogeneity in a colloidal gel by x-ray photon correlation spectroscopy
Auteur(s): Trappe Veronique, Pitard E., Ramos L., Robert Aymeric, Bissig Hugo, Cipelletti L.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 76 p.051404 (2007)
Texte intégral en Openaccess :
Ref HAL: hal-00133792_v3
PMID 18233656
Ref Arxiv: cond-mat/0702646
DOI: 10.1103/PhysRevE.76.051404
WoS: 000251326100047
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
73 Citations
Résumé: We use time-resolved X-Photon Correlation Spectroscopy to investigate the slow dynamics of colloidal gels made of moderately attractive carbon black particles. We show that the slow dynamics is temporally heterogeneous and quantify its fluctuations by measuring the variance $\chi$ of the instantaneous intensity correlation function. The amplitude of dynamical fluctuations has a non-monotonic dependence on scattering vector $q$, in stark contrast with recent experiments on strongly attractive colloidal gels [Duri and Cipelletti, \textit{Europhys. Lett.} \textbf{76}, 972 (2006)]. We propose a simple scaling argument for the $q$-dependence of fluctuations in glassy systems that rationalizes these findings.
Commentaires: Final version published in PRE
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Synthesis of porous platinum nanoballs in soft templates
Auteur(s): Surendran G., Ramos L., Pansu B., Prouzet E., Beaunier P., Audonnet F., Remita H.
(Article) Publié:
Chemistry Of Materials, vol. 19 p.5045-5048 (2007)
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Electrostatic interactions between polyelectrolyte and amphiphiles in two-and threee-dimensional systems
Auteur(s): Ramos L., Schönhoff M., Luan Y., Möhwald H., Brezesinski G.
(Article) Publié:
Colloids And Surfaces A: Physicochemical And Engineering Aspects, vol. 303 p.79-88 (2007)
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