A series of amphiphilic comb copolymers composed of poly(ethylene glycol) behenyl ether methacrylate (PEGBEM) and poly(oxyethylene methacrylate) (POEM) were synthesized via an economical and facile free radical polymerization. The synthesis of comb copolymers was confirmed by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), nuclear magnetic resonance (H-1 NMR) and Fourier transform infrared spectroscopy (FT-IR) spectroscopy. The microphase-separated morphology and crystalline structure of the comb copolymers were controllable by the copolymer composition, as characterized using wide-angle x-ray scattering (WAXS), differential scanning calorimetry (DSC), small-angle x-ray scattering (SAXS) and atomic force microscope (AFM). Due to good solubility in ethanol, the PEGBEM-g-POEM comb copolymers could be directly coated onto a microporous polysulfone support to prepare composite membranes. The maximum CO2/N-2 selectivity of the PEGBEM-g-POEM membrane reached 84.7, which is much higher than that of commercially available Pebax (17.0) and is one of the highest values reported for a polymer membrane under no humidified condition. The CO2 permeance through the PEGBEM-g-POEM membrane (21.9 GPU, 1 GPU=10(-6) cm(3)(STP)/(s cm(2) cmHg)) was also slightly higher than that through Pebax membrane (20.5 GPU) at similar membrane thickness. (C) 2015 Elsevier B.V. All rights reserved.