Hydrothermally rearranged cellulose membranes for controlled size sieving

Biodegradable polymers are important for reducing pollution and promoting sustainability as they break down more easily than traditional petroleum-based polymers. One such polymer is regenerated cellulose (RC), which is widely used in water purification and pharmaceuticals due to its chemical resistance and hydrophilicity. Since its direct use of cellulose is limited by its insolubility, derivatives like cellulose acetate (CA) are first converted through a regeneration process back into RC to make use of its functional properties. During this process, however, the membrane structure may be compromised, impairing its separation performance. Here we show that simply soaking CA membranes in hot water before regeneration significantly improves the structural integrity of RC membranes, retaining the sieving properties. The pretreatment causes planar shrinkage without disrupting the general characteristics of cellulose, allowing for sole adjustment of pore size. This straightforward approach enables precise tuning of membrane pore properties to suit specific application, such as adjusting pore size for efficient sieving of materials with particular molecular masses, all while maintaining high water permeance. Our findings suggest that hydrothermal processing has the potential to enhance the filtration performance of RC membranes and broaden their range of applications.