Small molecular amines (SMAs) (ethanecliamine (EDA), piperazine (PIP), monoethanolamine (MEA) and diethanol amine (DEA)) were separately used to modify the polyvinylamine (PVAm). ATR-FTIR, elemental analyzer, XRD and SEM were employed to characterize the SMA interacted PVAm. The PVAm-SMA/polysullone (PS) membranes were developed by coating PVAm-SMA mixed solutions on the PS ultrafiltration membrane. CO2 permeance and CO2/H-2 selectivity of the PVAm-SMAIPS membranes were investigated. Among different PVAm-SMA/PS membranes, the PVAm-MEA/PS membrane shows the highest CO2/H-2 separation performance. Moreover, the effect of the selective layer thickness on the CO2/H-2 separation performance of the PVAm-MEA/PS membrane was studied. With increasing the PVAm-MEA selective layer thickness, the CO2/H-2 separation performance of the membrane apparently decreases. Finally, the CO2/H-2 separation performance stability of the PVAm-MEA/PS membranes was investigated and no deterioration in the membrane permselectivity was observed. (C) 2014 Elsevier B.V. All rights reserved