Plasma polymerized acrylic acid (AA) thin films on poly(3-hydroxybutyrate) (PHB) membranes were evaluated as composite membranes for methanol/methyl tert-butyl ether (MTBE) separation by pervaporation (PV). Composite membranes were prepared in an inductively coupled radiofrequency plasma reactor. Experiments were performed at different powers (7.2 to 29.2W) and pressures, using pure AA monomer, as well as AA/air and AA/argon mixtures. Depositions chemical characteristics were determined through FTIR spectroscopy, hydrophilic character through contact angle measurements, and SEM images were also taken to analyze surface morphology. In PV measurements, membranes were methanol selective; the separation factor exceeded that of pure PHB membranes in all cases. Fluxes were lower than the original membrane but the performance separation index (PSI) was always higher. Results presented in terms of permeability were between 660 and 4045 barrer for methanol, while for MTBE they were markedly lower, between 10.5 and 57.7 barrer. These large differences in permeabilities caused high selectivities which ranged from 24 to 79. (c) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.