Balancing dehumidification efficiency and mechanical strength in SPEEK/PES membranes via microstructure engineering

Membrane-based dehumidification offers an energy-efficient alternative to conventional methods but requires membranes that concurrently exhibit high water vapor permeability and robust mechanical strength, a combination that is challenging to achieve. While sulfonated polyether ether ketone (SPEEK) provides excellent hydrophilicity for vapor transport, its high swelling tendency often compromises mechanical integrity. This work aims to optimize this critical performance–strength balance through microstructure engineering of SPEEK/polyethersulfone (PES) blend membranes fabricated via non-solvent induced phase separation (NIPS). By modulating the coagulation bath and the SPEEK/PES blending ratio, precise control over membrane morphology is demonstrated, enabling a tailored transition from finger-like to sponge-like pore structures. This structural evolution directly governs the key membrane properties: reducing the SPEEK content enhances mechanical strength but diminishes hydrophilicity and dehumidification efficiency. The optimal dehumidification performance of the 4:6 SPEEK/PES blend arises from the synergistic effect of enhanced hydrophilicity and optimized asymmetric microstructure, where morphological regulation via skin layer thinning plays a dominant role in mass transfer enhancement. The findings establish a rational design strategy for polymer blend membranes, demonstrating that synergistic microstructural control enables effective optimization of the performance–strength balance within the inherent trade-off framework for air dehumidification applications.