Effect of Electron Beam Irradiation on the Porosity of Polysulfone Membranes Studied by Positron Annihilation Lifetime Spectroscopy

Polymer membrane modification via electron beam irradiation has emerged as a powerful technique for tailoring filtration and separation performance. However, the fundamental role of environmental conditions during irradiation, particularly hydration state, remains poorly understood despite its potential to dramatically alter energy deposition pathways and subsequent structural evolution. This study systematically investigates hydration-state-dependent modification of polysulfone membranes through electron beam irradiation. By comparing atmospheric versus aqueous environment irradiation across graded doses, we demonstrate distinct pore structure evolution mechanisms. Electrochemical impedance spectroscopy analyses consistently revealed superior charge transfer resistance in dry-state membranes relative to their hydrated counterparts under equivalent irradiation conditions. Complementary positron annihilation characterization disclosed a critical hydration effect: irradiated hydrated membranes exhibited prolonged positron lifetimes, suggesting pore expansion, whereas dry-processed samples showed enhanced annihilation intensity indicative of increased porosity. These antiparallel trends in pore dimension versus density modulation establish that the hydration state fundamentally governs electron beam energy deposition pathways. The revealed environment-dependent structural control mechanism provides a new paradigm for precisely tailoring membrane architectures through irradiation parameter-space engineering.