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Séminaires à venir

Functional polymeric materials with various porosity scales : From design to application

Daniel Grande Institut de Chimie des Materiaux, Univ. Paris Est

Jeudi 22 juin 2017 - 14h00 - Amphi Langevin


Over the last decade, the generation of organic porous materials with tunable pore sizes and desired functionalities has been the subject of increasing attention in materials science. Interest in such porous frameworks originates from the large variety of applications in which they are involved, e.g. size/shape-selective nanoreactors, monoliths for advanced chromatographic techniques, nanofiltration membranes, high specific area catalytic supports, as well as 3-D scaffolds for tissue engineering.
This lecture examines the scope and limitations of three different approaches to porous polymers with controlled porosity and functionality at different length scales. The first approach relies on the synthesis of polystyrene-block-poly(D,L-lactide) diblock copolymers with functional groups at the junction between both blocks (e.g., COOH, SO3H, SH, CHO), followed by their macroscopic orientation, and the subsequent selective removal of the polyester block. The second strategy entails the preparation of biocompatible doubly porous crosslinked polymer materials through the use two distinct types of porogen templates, namely a macroporogen in combination with a nanoporogen. To generate the macroporosity, either CaCO3 or NaCl particles or fused PMMA beads are used, while the second porosity is obtained by using either hydroxyapatite nanoparticles or a porogenic solvent. Finally, 3-D macroporous scaffolds based on biodegradable polyesters have been engineered by electrospinning to generate nanofibrous biomaterials that mimic the extracellular matrix. The potentialities afforded by these approaches will be addressed, and some typical applications of the resulting porous materials will be illustrated.

Particles and Droplets at Nanostructured Interfaces : Metastability and Thermally Activated Dynamics

Carlos E. Colosqui Mechanical Engineering Dept., Stony Brook University

Jeudi 29 juin 2017 - 14h00 - Amphi Langevin


Our fundamental understanding of wetting, adsorption, and imbibition phenomena is embodied in classical mathematical descriptions (e.g., Young-Dupre, Young-Laplace, and Lucas-Washburn equations) that are derived under the assumption that interfaces are ideally smooth surfaces (e.g., planes, spheres, differentiable surfaces) separating perfectly homogeneous phases. Such idealization leads to the prediction of stable thermodynamic equilibrium states and neglects the presence of metastable states induced by diverse physicochemical heterogeneities. An increasing volume of experimental evidence indicates that the interplay between thermal motion and metastable states induced by nanoscale heterogeneities of solid/liquid interfaces can dominate the near-equilibrium dynamics of diverse colloidal and multiphase systems. In particular, this presentation will discuss recent experimental, theoretical, and computational studies of nano/microparticle adsorption at liquid interfaces, spontaneous droplet spreading, and nano/microcapillary imbibition. These systems exhibit a transition from dynamic regimes, dominated by hydrodynamic and capillary forces, to “kinetic” regimes governed by thermally activated transitions between metastable states. The presented results and proposed models suggest specific mechanisms by which combination of “system-level” geometry and nanoscale surface structure can alter the evolution of colloidal and multiphase systems.

Short Bio
Carlos Colosqui is an assistant professor in The Department of Mechanical Engineering and affiliated faculty in The Applied Mathematics and Statistics Department of Stony Brook University. He previously held postdoctoral positions at The Levich Institute for Physicochemical Hydrodynamics at CCNY-City University of New York and the Chemical and Biomolecular Engineering Department of Princeton University. His group currently performs theoretical, computational, and experimental research on wetting and interfacial phenomena in micro/nanoscale systems with support from the U.S. National Science Foundation and Office of Naval Research.