Controlling the Hierarchical Porosity and Nanostructure of Polyethylene using Amphiphilic Additives

Porous polymer membranes are widely used in gas separation, air purification, desalination, and other applications. Facile, low-cost production methods will further expand their use and enhance the sustainability of this technology. Ultra-high molecular weight polyethylene (UHMWPE) and amphiphilic additives are readily available materials that can be used for this purpose. In this work, we investigate how swelling UHMWPE with different amphiphilic additives influences the formation of hierarchically porous structures through co-crystallization. Analytical techniques including scanning electron microscopy (SEM), X-ray micro-computed tomography (microCT), and X-ray scattering (SAXS and WAXS) are employed to characterize the micro- and nanoporosity and morphology of the membranes, while differential scanning calorimetry (DSC) provided insights into crystallization behavior. Changing the head group and tail of the amphiphilic additives impacts the co-crystallization and hierarchical porous structure of UHMWPE, and grafting the additives to the PE chains also leads to structural differences compared to when no grafting is used. These findings will aid in establishing design rules for tuning hierarchical porosity and nanostructure in these polyethylene membranes, which could ultimately be used in a wide range of applications.