Polyaniline nanofibers, netlike polyaniline nanofibers and polyaniline nanosheets were prepared by chemical oxidative polymerization. Scanning electron microscopy (SEM) was employed to characterize morphology of the polyaniline (PANI) nanoparticles. The nanocomposite membranes were prepared by blending PANI nanoparticles with polyvinylamine (PVAm) as the active layer and polysulfone (PS) as the support layer. The surface and cross-section morphology and crystallization of nanocomposite membranes were measured by SEM and XRD. The permselectivity of nanocomposite membranes was investigated by the pure CO2 and N-2 gases and gas mixture containing 20 vol.% CO2 and 80 vol.% N-2. The results demonstrate that the inclusion of the PANI nanoparticles to PVAm increases the gas permeance and selectivity of the membranes due to chain packing disruption of PVAm and N-2 barrier property of PANI nanoparticles. The influences of PANI nanoparticles, PVAm and the interaction between PANI and PVAm on gas transport properties of nanocomposite membranes have been discussed. At CO2 partial pressure of 0.02 MPa, the nanocomposite membrane containing 17 wt.% PANI nanosheets displayed a CO2 permeance of 1200 GPU and a CO2/N-2 selectivity of 120. The permeance increased about 852% and the selectivity increased about 137% compared with the PVAm/PS membrane. The separation performance stability of the PVAm/PS membrane and PANI-PVAm/PS membrane was investigated and no deterioration in membrane permselectivity was observed. (C) 2012 Elsevier B.V. All rights reserved.