Insights into the morphology and gas separation characteristics of methylene diisocyanate (MDI)-functionalized nanoTiO2 polyurethane: quantum mechanics and molecular simulations studies

It is of important scientific significance to develop membranes with high gas transfer properties. The primary aim of our study was to inspect the gas separation behavior and morphological characteristics of mixed matrix membranes (MMMs) based on TiO2-polyurethane (PU) and methylene diisocyanate (MDI)-TiO2-PU using quantum mechanics (QM), Monte Carlo (MC), and molecular dynamics (MD) simulations. Frontier Molecular Orbital (FMO) based on QM approaches such as Mulliken charges, the density of states (DOS), electrostatic potential (ESP), Conductor-like screening model (COSMO), and Fukui's function and orbitals were employed to ascertain the chemical reactivity, regioselectivity, phase behaviour, and surface properties of neat and MMMs. Furthermore, the physicochemical properties of MMMs structures, including the radius of gyration (Rg), X-ray scattering, radial distribution function (RDF), the solubility parameter (δ), cohesive energy density (CED), free fractional volume (FFV), and mechanical properties were investigated using MD simulation. Based on obtained results, it can be dedicated that MMMs structures could exhibit improved physicochemical properties. Additionally, MD simulation was used to study the CO2, CH4, and N2 transport properties in neat and MMMs containing higher concentrations of nanoparticles. Consequently, MD simulation results indicated that our constructed MMM's performances were close to Robeson's upper bound.