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Anharmonic versus relaxational sound damping in glasses. I. Brillouin scattering from densified silica
Auteur(s): Rat E., Foret M., Massiera G., Vialla R., Arai M., Vacher R., Courtens E.
(Article) Publié:
Physical Review B, vol. 72 p.214204 (2005)
Résumé: This series discusses the origin of sound damping and dispersion in glasses. In particular, we address the relative importance of anharmonicity versus thermally activated relaxation. In this first article, Brillouin-scattering measurements of permanently densified silica glass are presented. It is found that in this case the results are compatible with a model in which damping and dispersion are only produced by the anharmonic coupling of the sound waves with thermally excited modes. The thermal relaxation time and the unrelaxed velocity are estimated.
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Bounded step superdiffusion in an oriented hexagonal phase.
Auteur(s): Gambin Y., Massiera G., Ramos L., Ligoure C., Urbach W.
(Article) Publié:
Physical Review Letters, vol. 94 p.110602 (2005)
Résumé: Fluorescence recovery after pattern photobleaching is used to measure the self-diffusion of surfactant molecules, along cylinders and perpendicular to their main axis in an oriented hexagonal lyotropic phase. Unexpectedly, while the motion along cylinders is diffusive, a superdiffusive behavior is observed in the direction perpendicular to the cylinder axis. Moreover, varying the lattice parameter, we found that the perpendicular diffusion time is governed only by the number of cylinders to cross, providing experimental evidence for superdiffusion with a bounded step length.
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The steric polymer layer of hairy wormlike micelles
Auteur(s): Massiera G., Ramos L., Pitard E., Ligoure C.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 15 p.S225-S231 (2003)
Résumé: Hairy wormlike micelles are constituted of surfactant micelles onto which amphiphilic copolymers are adsorbed. The copolymer layer induces a steric repulsion between the micelles, which is evidenced by the emergence of a broad peak in the structure factor for semi-dilute solutions. In this paper, we propose three experimental determinations of the thickness of the copolymer layer, h. We compare the results of the different approaches and show that both the numerical values of h and its variation with the surface density of the copolymer layer are in very good agreement with simple theoretical expectations.
Commentaires: English Article Sp. Iss. SI 669HX
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Structure Factor of Polymers Interacting via a Short Range Repulsive Potential: Application to Hairy Wormlike Micelles 
Auteur(s): Massiera G., Ramos L., Ligoure C., Pitard E.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 68 p.021803 (2003)
Texte intégral en Openaccess : 
Ref HAL: hal-00338950_v1
PMID 14524997
DOI: 10.1103/PhysRevE.68.021803
WoS: 000185193900060
Exporter : BibTex | endNote
9 Citations
Résumé: We use the random phase approximation to compute the structure factor S(q) of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions.
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Hairy wormlike micelles: structure and interactions.
Auteur(s): Massiera G., Ramos L., Pitard E., Ligoure C.
Conference: 11th International Conference on Colloidal and Surface Science (Foz do Iguaçu, Brasil, FR, 2003-09-15)
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Role of the size distribution on the elasticity of a model entangled polymer solution.
Auteur(s): Massiera G., Ramos L., Ligoure C.
(Article) Publié:
Europhysics Letters (Epl), vol. 57 p.127-133 (2002)
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Hairy wormlike micelles : Structure and Interactions.
Auteur(s): Massiera G., Ramos L., Ligoure C.
(Article) Publié:
Langmuir, vol. 18 p.5687-5694 (2002)
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