PX-MDsim: a rapid and efficient platform for large-scale construction of polyamide membranes via automated molecular dynamics simulations

Abstract

Polyamide (PA) membranes have attracted extensive attention due to their excellent separation performance in water treatment through reverse osmosis and nanofiltration processes. Although numerous molecular simulation studies attempt to explore their advantages from the microstructure, large-scale construction and simulation of PA membranes remain challenging, mainly due to the complexity and computational intensity of cross-linking reactions of polymers in molecular dynamics simulations. This paper introduces an automated platform called PX-MDsim for modeling and simulation of PA membranes. PX-MDsim is based on the PXLink framework and extends its applicability to any monomer with amino (–NH₂) and carboxyl (–COOH) groups. The platform, combined with the PXLink program, realizes the full-process automated cross-linking simulation from input preparation, initial system construction, force field generation, functional group identification, and charge distribution update. Moreover, the software was used to cross-link m-phenylenediamine and 1,4-bis(3-aminopropyl)piperazine with trimesic acid, respectively, and multiple membrane structures with different cross-linking degrees were obtained. Furthermore, the generated membrane microstructure was analyzed using methods such as pore size distribution and order parameter, and the obtained results verified the applicability and accuracy of PX-MDsim in constructing PA membrane structures. The platform is user-friendly and accessible to researchers without prior expertise in molecular dynamics simulation, and it offers new possibilities for polymer research and applications.