Rheology of nanosized hairy grain suspensions |
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Authors: | J.-C. Castaing C. Allain P. Auroy L. Auvray |
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Affiliation: | Rh?ne-Poulenc Recherche, 52 rue de la Haie-Coq, 93308, Aubervilliers Cedex, France FAST(UMR 7608 du CNRS),Université Paris-Sud, 91405, Orsay Cedex, France Institut Curie (UMR 168 du CNRS), Section de Recherche, 11 rue Pierre et Marie Curie, 75231, Paris Cedex 05, France Laboratoire Léon Brillouin,CNRS-CEA, Centre d'études Nucléaires de Saclay, 91191, Gif-sur-Yvette Cedex, France
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Abstract: | Suspensions of nanosized hairy grains have been prepared by grafting long polydimethylsiloxane chains (molecular weight ) onto silica particles (radius ), dispersed into a good solvent of PDMS. Depending on the particle volume fraction, different rheological behaviors are observed. In the very dilute regime, the suspensions are perfectly stable and the particles behave almost as hard spheres: flow penetration inside the corona is then very weak. When the particle volume fraction goes to the close packing volume fraction, the suspension viscosity does not diverge as for hard spheres due to the increase of flow penetration inside the corona and to corona entanglements. The particles have then the same behavior as polymer stars having an intermediate number of arms (). Finally, in the concentrated regime (), the suspensions form irreversible gels. We shown that this unexpected gelation phenomenon is related to the presence of the silica cores: grafted PDMS chains can adsorb onto different particles and form irreversible bonds between the cores. The viscosity and elastic modulus evolutions during gelation are well described by the scalar percolation model of sol-gel transition. Received 23 March 1998 |
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Keywords: | PACS. 82.70.Dd Colloids - 61.41.+e Polymers elastomers and plastics - 81.05.Qk Reinforced polymers and polymer-based composites |
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