Multilayer thin films of poly(ethylene oxide) (PEO) and poly(methacrylic acid) (PMAA), deposited via layer-by-layer (LbL) assembly from aqueous solutions, are investigated for CO2/N-2 separation. Eight and ten bilayer (217 and 389 nm thick, respectively) PEO/PMAA thin films deposited on a 25 mu m polystyrene substrate exhibit CO2/N-2 selectivities of 142 and 136, respectively. These are the highest reported to-date for this gas pair separation using a homogeneous polymer film. While further work remains to improve CO2 permeability, these results indicate the potential of LbL assemblies as standalone CO2 separation membranes for low-flux/high-purity applications, or as part of a composite and/or mixed-matrix membrane for high-flux applications. (C) 2017 Wiley Periodicals, Inc.