Sommaire:

The way the dynamics of glass forming systems is modified by confinement, i.e. in systems with large interface, has been the subject of intense research in recent years. This seminar is intended to present an overview of the results obtained in our group on the glassy dynamics of glass forming polymers subjected to different kind of confinement, especially nanocomposites and thin films [1-6]. The segmental dynamics is probed by broadband dielectric spectroscopy (BDS), a technique able to probe the spontaneous fluctuations at equilibrium. The temperature marking the equilibrium to out-of equilibrium transition of the glass former, namely the glass transition temperature (Tg), and the physical aging, namely the slow evolution of disordered glassy material towards thermodynamic equilibrium occurring below Tg, are probed by differential scanning calorimetry (DSC). As a general important conclusion, we show that the out-of-equilibrium dynamics, in terms of Tg and physical aging, is decoupled from the equilibrium dynamics. This result markedly contrasts with the general view that the out-of-equilibrium dynamics is solely related to the molecular mobility of the glass former. This means that, apart from the intrinsic molecular mobility, geometrical factors are also important in determining the Tg and physical aging behavior of the glass former under confinement. Possible explanations to these results are discussed. [1] V. M. Boucher, D. Cangialosi, A. Alegría, J. Colmenero, J. Gonzalez-Irun, L. M. Liz-Marzan, Soft Matter 6, 3306 (2010). [2] V. M. Boucher, D. Cangialosi, A. Alegría, J. Colmenero, Macromolecules 43, 7594-7603 (2010). [3] V. M. Boucher, D. Cangialosi, A. Alegría, J. Colmenero, J. Gonzalez-Irun, L. M. Liz-Marzan, Soft Matter 7, 3607 (2011). [4] D. Cangialosi, V. M. Boucher, A. Alegría, J. Colmenero, J. Chem. Phys. 135, 014901 (2011). [5] D. Cangialosi, V. M. Boucher, A. Alegría, J. Colmenero, Polymer 53, 1362 (2012). [6] V. M. Boucher, D. Cangialosi, H. Yin, A. Schönhals A. Alegría, J. Colmenero, Soft Matter DOI: 10.1039/C2SM25419K.

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