Alexander V. Neimark (Université Rutgers, New Jersey, Etats-Unis) présentera vendredi 5 mai à 14h, dans la salle des Conseils de la faculté de Chimie (32.42.101), un séminaire intitulé :
Self-Assembly and Transport in Polyelectrolyte Membranes
Résumé
Polyelectrolyte membranes composed of hydrophilic and hydrophobic fragments segregate upon solvation and form mesoscopic structures with interpenetrating hydrophilic and hydrophobic subphases. A typical example is Nafion polymer with sulfonate sidechains attached to perfluorinated backbone. Water concentrates around the sulfonate groups in nanometer size clusters, which grow and coalesce into a 3-dimentional network of water channels as the degree of hydration increases. This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electro-chemical devices, as well as permselective diffusion barriers in protective fabrics. We introduce a coarse-grained soft-core model of Nafion membrane, which accounts explicitly for polymer rigidity and electrostatic interactions, and is matched to atomistic molecular dynamics simulations. By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explore geometrical, transport, and sorption properties of hydrated membranes of various composition. A novel methodology is suggested for coarse-grained modeling of proton transport accounting for vehicular and hopping mechanisms.
Insight from the multiscale molecular modeling helps guide development of composite nanomaterials with improved properties. As an instructive example, I will show how we used a better understanding of the specifics of polyelectrolyte membrane morphology and transport to in-situ grow metal oxide nanoparticles inside the membrane and fabricate multicatalyst composite barriers for capture and detoxification of chemical warfare agents.
Selected references :
- A. Vishnyakov and A.V. Neimark, – Self-assembly in Nafion Membranes upon Hydration : Water Mobility and Adsorption Isotherms, – J. of Physical Chemistry B, 2014, 118, 11353
- M.-T Lee et al, Coarse-Grained Model of Water Diffusion and Proton Conductivity in Hydrated Polyelectrolyte Membrane, – J. of Chemical Physics, 2016, 144, 014902.
- J. Landers et al, In situ growth and characterization of metal oxide nanoparticles within polyelectrolyte membranes, Angewandte Chemie Int. Ed., 2016, 55, 11522.
For more info visit http://sol.rutgers.edu/~aneimark/
