Modeling and simulation of the water gradient within a Nafion membrane

Abstract

The perfluorinated sulfonic acid membrane (Nafion) shows among ionomers high water uptake and cationic conductivity. These properties allow Nafion to be used in nanocomposite actuators, sensors and fuel cells. In situ experiments have shown that there is a water gradient within the Nafion membrane. The water gradient causes the alteration of other physical properties within the thickness of the membrane and has a drastic impact on the performance of the devices made of the Nafion membrane. Deriving closed-form equations and using molecular dynamics (MD) simulation results, we bridge Nafion properties at the atomic scale and the macroscopic behavior of the membrane within a hierarchical multi-scale model. Multiple discrete simulation cells are selected across the thickness of the membrane with a wide range of water contents as representative volume elements (RVEs). The present framework is able to quantitatively predict the macroscopic properties of Nafion with the nanometric resolution regarding the water gradient across the membrane.

Molecular dynamics simulation study of glass transition in hydrated Nafion

“…Also, the force field parameters are obtained from Swissparam web service . More details are available in our recent study …”

Sulfonated Fluorocarbon Polymers as Proton Exchange Membranes for Fuel Cells

“…For the P(BSFA) 90 -P(PFPA) 255 membrane, the elongation-at-break increased to 35% at 5.73 MPa, which indicated that there was a close connection for 255 PFPA parts in the test of the membrane's mechanical properties. A higher degree of PFPA can cause the membrane elasticity to decline, thereby decreasing the membrane's tensile strength, and more brittle membranes can be expected (Ozmaian and Naghdabadi, 2014;Liang et al, 2015;Liu et al, 2017) While crystallization would normally make the polymer hard and brittle, the polymer PBSFA 90 -P(PFPA) 396 broke at 4.13 MPa, indicating that a greater number of PFPA block segments caused the lower intermolecular interaction to cure the curling process of the polymer chains (Wang et al, 2018). Meanwhile, the highest stress was 2.35 MPa for recast na on at a stress of 35%; this was a ected by solvent action and the entanglement of the molecular chain of recast na on was di erent from that of melt extrusion (Xiao et al, 2015).…”

“…9 e ability of water uptake of PEMs with di erent block polymers Fig. 10 Conductivities of the diblock copolymers in response to the trans-plane electric eld selectivities (Ozmaian and Naghdabadi, 2014;Liang et al, 2015;Zhao et al, 2016). As a result, there is no doubt that trans-plane measurement is more suitable for the operation of the fuel cell and that proton transport on the thin dimension of the membrane is most important.…”

Properties of Nafion Under Uniaxial Loading at Different Temperatures: A Molecular Dynamics Study

“…Besides, it has been shown that for the extruded membranes, the anisotropic morphology was found to persist and has a significant effect on its mechanical and physical properties. The physical and mechanical properties of Nafion are strongly dependent on its thermal conditions, water content and alignment [7][8][9] . Mechanical loading initially causes orientation of polymer chains and linear deformation.…”