8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P8.35Gradient of glass transition in nanocomposites :evidence by NMR et scanning differential calorimetryAurélie Papon, 1 Helene Montes, 1 Laurent Guy, 2 Kay Saalwachter, 3 and FrancoisLequeux 11 ESPCI, 10 rue Vauquelin, 75231, PARIS, France2 Rhodia Operations, Collonges au Mont d’Or, France3 Martin Luther universitat, Halle-Wittenberg, GermanySince more than a decade, it has been noticed that the glass transition of thin polymer films dependson their thickness. However, many debates and conjectures rendered the physics of thin filmsglass transition quite unclear. In this communication, we evidence the fact that solid particlesgenerate a gradient of glass transition temperature in the polymer matrix around them. For that, wehave measured extensively the NMR relaxation signal of model nano-composite of silica colloidsembedded in a polyacrylate matrix, at various temperature and solvent concentration. We are ableto describe all the NMR data by a single value i. e. the range of the gradient of glass transitiontemperature. Moreover, the results obtained by NMR allow to predict the DSC response - evenafter aging sequences - from the one of the matrix alone. These results exhibit without any doubtthat the concept of gradient of temperature transition is able to explain quantitatively the dynamicalproperties of nano-composites.35