LAUSR

The fabrication and scale‐up of pervaporation composite membranes are often challenged by pore penetration into microporous substrate. This study presents an innovative composite membrane featuring an intermediate poly(ether‐block‐amide) (PEBA) layer formed at a liquid–liquid interface, effectively preventing pore penetration and enabling uniform deposition of the selective polydimethylsiloxane (PDMS) layer. The PDMS layer was precisely controlled through dynamic monitoring of the membrane solution droplets spreading, optimizing the PDMS spreading thermodynamic and kinetic parameters involved. SEM confirmed the dense top‐layer structure of the PDMS‐PEBA/polytetrafluoroethylene (PTFE) membrane, with controllable thicknesses of individual layers. The appropriate thicknesses for the PEBA and PDMS layers were investigated through both the resistance model analysis and pervaporation test results. Based on this trilayer structure, a scale‐up 600 cm2 PDMS‐PEBA/PTFE membrane demonstrated a separation factor of 22.4 and a flux of 1.9 kg/m2/h for concentrating n‐butanol (60°C, 1 wt.% n‐butanol/water), highlighting its potential for industrial applications.