Enhanced gas selectivity in thin film composite membranes of poly(3-(2-acetoxyethyl)thiophene)

The gas transport properties of surface-treated poly(3-(2-acetoxyethyl)thio phene) (P3AcET) membranes are reported. Base or acid catalyzed hydrolysis o f the ester group of P3AcET yields poly(3-(2-hydroxyethyl)thiophene) (P3HET ), a highly permselective conducting polymer. Permeability coefficients wer e determined for as-cast P3AcET membranes (P-CO2 = 1.42, P-O2 = 0.24, P-N2 = 0.05, P-CH4 = 0.08 Barrers) and selectivity values were calculated (O-2/N -2 = 5.1, CO2/CH4 = 18.5). Formation of a chin selective P3HET surface laye r resulted in an overall decrease in permeance (P11) accompanied by a drama tic increase in selectivity for both the base-treated (O-2/N-2 = 12.9, CO2/ CH4 = 20.0) and acid-treated (O-2/N-2 = 11.7, CO2/CH4 = 45.0) composites. M icroscopic (AFM, SEM) and spectroscopic (ATR-FTIR) characterization of the thin film composites confirmed the surface specificity of the hydrolysis re action. (C) 2002 Elsevier Science BN. All rights reserved.