The preparation and characterisation of the cation complexation properties of a series of polyamic acid and polyimides containing crown ether units are presented. It is found that the complexing power of the amic acid form of the polymers is significantly higher than that of the imide form; implying the ability of the carboxylic acid grouping to exhibit lariat behaviour. The carboxylic acid group enters into coordination with the cation, increasing the binding energy and hence the binding constant. Computer modelling has been used to provide insight into the various factors that influence the binding energy of the cation to the crown ether segment of the polymer chain. The complexation characteristics in aqueous and non-aqueous media are examined and the results are discussed in the context of changes in the contribution of the solvent to solvation sheath of the cation, (C) 2000 Elsevier Science Ltd. All rights reserved.