Prediction and characterization of the charge/size exclusion properties of over-oxidized poly(pyrrole) films

Over-oxidation of poly(pyrrole) films has been shown to result in permselective films favoring cation transport and excluding anions. The exclusion principal depends on both the size of the analyte and electrostatic interactions between the analyte and the polymer film. The size of the polymer dopant anion and hence the resulting pore size of the polymer has been varied and the size exclusion studied. Molecules just larger than the size of the original dopant anion can pass through the membrane, thought to be due to solvation of the incorporated anion in the initial polymer preparation. The pH of the sample analyte has been varied to test the permselective properties of the prepared polymer. A range of substituted pyrroles were polymerized, over-oxidized and compared for selectivity. The nature and position of substituents on the pyrrole monomer were observed to change the morphological structure of the polymer and hence the resulting selectivity of the membrane. Molecular modeling of both the analytes and the dopant ions has allowed size/charge density profiles of the analytes to be compared with the predicted size of the polymer pores.