Mixed matrix type filled copolymer membranes were prepared by in situ incorporation of nano sized sodium montmorilonite (NaMMT) clay into the matrix of the copolymer during emulsion radical polymerization of acrylonitrile (AN) and acrylic acid (AA) at three different molar ratios of AN: AA of 5:1, 10:1 and 15:1. The structure of the copolymer and filler-polymer compatibility was characterized by FTIR, XRD, SEM and mechanical properties. These membranes were used for dehydration of ethyl alcohol in the concentration range of 76-99.5 wt% alcohol including azeotropic composition (95.6 wt% of alcohol in water at atmospheric pressure). The effect of copolymer composition, wt% of nano clay and feed concentration on sorption, flux, separation factor, membrane permeability and intrinsic membrane selectivity were studied. The effect of feed temperature on solvent flux and membrane permeability were also studied. The interactive effects of the synthesis and process parameters were optimized by Box-Behnken design (BBD) of response surface methodology (RSM). The long term stability of the membranes was also evaluated by studying flux and selectivity over a long period of time. (C) 2017 Elsevier B.V. All rights reserved.