In order to improve the permselectivity of poly(dimethylsiloxane)(PDMS) membrane without much reduction in permeability value, a new type of poly(dimethylsiloxane) membranes containing different concentrations of non-ionic and cationic amino-hydroxy functionalities has been prepared. IR, H-1 NMR and C-13 NMR. GPC, DSC, TGA and WAXD techniques were used to characterize the prepared membranes. The gas transport properties, viz., permeability, solubility and diffusivity of the prepared membranes were determined for N-2, O-2, CH4 and CO2 gases. The fractional free volume present in the PDMS membrane was found to decrease with increasing amino-hydroxy functionality. The permselectivity values for O-2/N, and CO2/CH4 gas pairs were found to increase with increasing concentrations of amino-hydroxy functionalized siloxane. The effect of temperature on gas permeabilities was studied and activation energy was determined for the studied gases. © 2005 Elsevier B.V. All rights reserved.