Open Source Program Office
Open Sourcing the Wisconsin Idea
Ying Li, yli2562@wisc.edu
Water transport through polymeric membranes is a fundamental process critical to various applications, from seawater desalination to wastewater remediation. For over a century, the dominant theory in the field has been the solution-diffusion mechanism, where water is assumed to dissolve into the polymer matrix and diffuse across it under a constant pressure profile. However, recent advancements in atomistic molecular simulations have challenged this long-held assumption, suggesting that the traditional view may not fully capture the underlying transport phenomena (Science Advances 2023, 9, eadf8488). The simulation data indicates a linear pressure gradient across the membrane and evidence of water transport via nanoscopic porous structures that spans the polymeric membrane. These findings align more closely with a pore-flow mechanism, fundamentally different from solution-diffusion and requiring a revaluation of existing theoretical models. This project will utilize state-of-the-art molecular simulations to further investigate these observations and test their implications.
In addition to revisiting the transport dynamics across polymeric membranes, the project will explore water transport across organic solvent films, traditionally expected to adhere to solution-diffusion due to their incompressible nature. This will be a key test to validate the applicability of molecular simulations to study non-equilibrium solvent transport phenomena. If monomers of a polymeric membrane do not polymerize, they would behave similar to a organic solvent film and transport mechanism is expected to follow the solution-diffusion mechanism. However, once fully polymerized the transport mechanism is expected to transition to a pore-flow mechanism. Therefore, a central research question arises: How does the degree of polymerization, branching, and crosslinking influence the transport mechanism in polymeric membranes? We aim to determine whether these chemical structural variations in polymers lead to a gradual transition between solution-diffusion and pore-flow mechanisms, or if the shift is abrupt and dependent on specific structural properties of a polymer.
This project will address fundamental and open questions about the mechanisms governing water transport in polymers, with the potential for improving the design principles of next-generation membrane materials. By bridging the gap between theoretical models and simulation-based evidence, our research aims to provide novel insights that could redefine how we understand and engineer polymeric membranes for enhanced performance in industrial applications. Postdoctorates Dr. Subhamoy Mahajan and Dr. Hengyu Xu in our group would guide and mentor the interns during the time on the project.
BASH scripting, Basic knowledge of LAMMPS molecular dynamics package.