Molecular-Dynamics Studies on the Structures of Polymer Electrolyte Membranes and the Diffusion Mechanism of Protons and Small Molecules
نویسندگان
چکیده
We performed a series of molecular dynamics (MD) simulations on Nafion membranes which contain various quantities of water and methanol. The simulations gave a variety of nanoscale phase separated structures, such as cluster structures, channel structures, and cluster-channel structures. This is the first work that an atomistic MD simulation reproduced such nanoscale phase separations from random-phased amphipathic polymer solutions. The calculated cluster-channel structure is consistent with the experimental results of X-ray diffraction [1]. We also investigated the diffusion coefficients of water, methanol and proton in these membranes. Estimated diffusion coefficients of water in the membranes so much depend on the water contents that the largest value is about 10 times as large as the smallest one, and these values are in qualitatively good agreement with the NMR results [2]. For proton, we employed semi-classical MD approach by using empirical valence-bond (EVB) method [3]. EVB-MD approach can reproduce the hopping transfer of proton and estimate a reasonable value of diffusion coefficient of proton. Furthermore, our simulation indicated that water was rarely found in the hydrophobic domains of the Nafion membranes, whereas methanol penetrated into the hydrophilic / hydrophobic interfacial regions. We found that the methanol permeability around sulfonic groups is one-third of that in the water clusters. It means that methanol molecules are trapped by the hydrophilic groups of the membranes and the majority of methanol passes through the water clusters.
منابع مشابه
Mechanical Properties of CNT-Reinforced Polymer Nano-composites: A Molecular Dynamics Study
Understanding the mechanism underlying the behavior of polymer-based nanocomposites requires investigation at the molecular level. In the current study, an atomistic simulation based on molecular dynamics was performed to characterize the mechanical properties of polycarbonate (PC) nanocomposites reinforced with single-walled armchair carbon nanotubes (SWCNT). The stiffness matrix and elastic p...
متن کاملMolecular Dynamics Simulations on Polymeric Nanocomposite Membranes Designed to Deliver Pipobromane Anticancer Drug
Three chitosan (CS), polyethylene glycol (PEG) and polylactic acid (PLA) nanocomposite systems containing SiO2 nanoparticles and water molecules were designed by molecular dynamics (MD) simulations to deliver pipobromane (PIP) anticancer drug in order to discover the most appropriate drug delivery system (DDS) in aqueous medium which was analogous to the human body. The density for the CS matri...
متن کاملMolecular dynamics studies of straight-chain alkanes diffusion in SiO2 ceramic versus Bosanquet formula
Molecular Dynamics (MD) simulations were applied to calculate self-diffusion coefficients (Di ) and heats of adsorption for ethane, propane and n-butane. The simulations were done in temperature range of 300-525 K for various concentrations inside the pores of silicalite type zeolite. The calculated values of self-diffusion coefficients and heats of adsorption resulted from the current wo...
متن کاملMolecular Docking Based on Virtual Screening, Molecular Dynamics and Atoms in Molecules Studies to Identify the Potential Human Epidermal Receptor 2 Intracellular Domain Inhibitors
Human epidermal growth factor receptor 2 (HER2) is a member of the epidermal growth factor receptor family having tyrosine kinase activity. Overexpression of HER2 usually causes malignant transformation of cells and is responsible for the breast cancer. In this work, the virtual screening, molecular docking, quantum mechanics and molecular dynamics methods were employed to study protein–ligand ...
متن کاملRecent developments in high-temperature proton conducting polymer electrolyte membranes
Progress in the area of proton conducting polymer electrolyte membranes is intimately linked with the development of polymer electrolyte membrane fuel cells, and is today largely driven by the insufficient properties of humidified Nafion membranes at temperatures above 100 8C. Recent developments in the field include new ionomers and hybrid membranes containing inorganic nanoparticles to contro...
متن کامل