Transport of Water In Soft confinemenT – TWIST
The aim of this project is to provide a predictive description of water transport in soft porous materials. Soft matter is indeed subjected to several interplaying effects that influence transport at the nanoscale: surface heterogeneities due to hydrophilicity/hydrophobicity of the confining surface, diffuse boundary since the penetration depth of water at the surface of the confining matrix is ill-defined, and deformations or mechanical effects such as swelling which are inherent to the soft nature of the host medium and depend on the thermodynamic state of confined water. A correct description of water transport in soft confinement has therefore to consider adsorption and confinement effects, microscopic diffusion mechanisms, and local as well as global host deformations. We therefore propose to develop a unifying framework for water transport in soft porous materials which accounts for coupling between adsorption and deformation.
Our strategy combines well-established experimental, molecular simulation, and theoretical tools to reach this ambitious objective at all relevant length and time scales. Thanks to a multiscale approach, we will gain insights into the fundamental microscopic mechanisms while understanding how each scale (from the nm scale to the macroscopic scale) affects water transport in such environments. The experimental program is based on the complementarity in time and length scales of Neutrons or X-ray scattering (micro scale), NMR (meso scale) and macroscopic permeance measurements. Transport will be characterized on each scale under relevant conditions of stress or strain and pressure gradient of flowing water. The theoretical description will establish two constitutive equations: a first relationship connecting the structural parameters of the membrane (porosity, surface area, pore size) to the mechanical deformation (stress, strain) and a second relationship connecting the structural parameters of the membrane to water transport (permeability). In so doing, we will establish a double structure/property relationship which allows describing the coupling between transport and mechanics through the same common structural parameters of the membrane.
Using prototypical samples that are simple yet representative examples of soft porous materials in terms of porosity, pore morphology, surface chemistry and elasticity, our aim is to establish a framework which will provide a robust expression for the permeance K(µ,T,s), i.e. the response of the flow rate to a pressure gradient ?P, as a function of temperature T, water chemical potential µ, and external stresses s. In this perspective, we have gathered a team of experts that master the different parts of the 4-years project: (1) synthesis of prototypical soft matter membranes, (2) structure and dynamics from the atomic to the micron-scale, (3) theory and molecular simulation of transport and poromechanics of fluids in nanoconfined environments, and (4) transport experiments of water in porous media under constant stress or strain.
In summary, our project will provide a rigorous upscaling strategy from atom-scale coefficients to predict the coupling between transport and mechanics without using empirical laws. Such a tool will directly benefit to the continuously growing industrial sector taking advantages of polymeric porous materials, but also to many others, as for example wood based materials or food processing. On a more fundamental basis, it will also give new insights for understanding many biological processes.
Madame Marie PLAZANET (Laboratoire Interdisciplinaire de Physique)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
I.E.M. Institut Européen des Membranes
LIPhy Laboratoire Interdisciplinaire de Physique
Phenix PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
Laboratoire Navier Centre Laboratoire Navier Centre
Help of the ANR 420,876 euros
Beginning and duration of the scientific project: September 2017 - 48 Months