Explorations of delamination and irregular structure in poly(amide-imide)-polyethersulfone dual layer hollow fiber membranes

► Dual layer PAI/PES hollow fibers are made via simultaneous extrusion technique. ► The chemistry of the polymer dopes and spinning parameters were carefully tailored. ► The evolutions of the membrane morphology and structure were investigated. ► Accumulated water in the interface probably leads to a delamination of two layers. ► This study provides a foundation to develop inter-penetrating dual layer membranes.