Enhancing H2-permselectivity of high-flux hollow fiber membrane via in-situ layer-by-layer surface treatment

This manuscript presents the first application of a layer-by-layer (LbL) permselective all-polymer coating to a Torlon© polyamide imide (PAI) hollow fiber substrate to realize a new class of manufacturable, highly selective, composite polymer membrane for hydrogen separation from carbon dioxide and nitrogen light gases. Sub-micron, defect-free conformal coatings of [PEI10/PAA4] polymeric pair were successfully deposited on both PEI-functionalized and untreated hollow fiber substrates. Surface functionalization was found to provide twofold benefits of introducing a positively charged surface to aid LbL deposition while enhancing selective transport of hydrogen through the membrane achieving high selectivities of H2:CO2 (>200:1) and H2:N2 (>2000:1) at 40 Barrers of H2 permeability exceeding the Robeson upper bound for homogenous polymer films. The deposition of low-cost, water-based polymers and easy to fabricate LbL membranes on conventional hollow fiber has potential use at industrial scale for hydrogen separation.