3-Aminopropyltriethoxysilane-aided cross-linked chitosan membranes for gas separation: grand canonical Monte Carlo and molecular dynamics simulations

Molecular simulations were performed to consider the structural and transport properties of chitosan/3-aminopropyltriethoxysilane (APTEOS) mixed matrix membranes (MMMs). In order to consider the presence of APTEOS content on the performances of membrane, various amounts of APTEOS were added to the polymeric matrix as a cross-linker. Structural characterizations such as radial distribution function (RDF), fractional free volume (FFV) and X-ray diffraction (XRD) were carried out on the simulated cells. Self-diffusivity and solubility of membranes were calculated using mean square displacement (MSD) and adsorption isotherms, respectively. Additionally, permeability and permselectivity of CO2 and N-2 gases were calculated by grand canonical Monte Carlo and molecular dynamics methods. The system temperature was set to 298K using a Nose-Hoover thermostat. According to the results, upon increasing APTEOS loading, CO2 permeability increases until 10wt.% loading. Then, by adding 20wt.% of APTEOS, CO2 permeability decreases, which could be related to higher crystallinity. XRD graphs indicated that the crystallinity decreased when adding 10wt.% APTEOS, while higher APTEOS content (up to 20wt.%) led to higher crystallinity percentage, consistent with permeability results. Compared to literature reports, the present simulation indicated higher accuracy for defining the structural and transport properties of APTEOS cross-linked chitosan MMMs.