ELSEVIER Reactive Polymers 24 (1994) 35-39 Reactive polymers Synergistic complexation of metal ions with bifunctional interpenetrating polymer networks A.A. Kriger a, B.A. Moyer u'*, S.D. Alexandratos a,, a Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA b Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6119, USA Received 10 May 1994; accepted in revised form 24 July 1994 Abstract A vinylpyridine/acrylic acid bifunctional interpenetrating polymer network (IPN) has been synthesized and evaluated for application in metal ion separations. Monofunctional vinylpyridine and acrylic acid IPNs were also synthesized and differences between the distribution coefficients of the three systems were used as an indication of whether an enhanced (i.e., synergistic) complexation of metal ions was occurring in the bifunctional polymer. Important effects attributable to the combined action of the two functionalities in the same polymer are observed. Complexation of Eu(III), a hard Lewis acid, by the bifunctional polymer is inhibited by hydrogen bonding between the two ligands. Borderline Lewis acids are complexed with high efficiency and evidence for a synergistic effect is presented. Keywords: Polymer-supported reagent; Metal ion complexation; Interpenetrating polymer network; Synergism 1. Introduction Interpenetrating polymer networks (IPNs) are a novel class of materials which have been studied for numerous applications [1]. An IPN is defined as a combination of two or more poly- mers, at least one of which is synthesized in the presence of the other [2]. Bifunctional IPNs offer unique advantages in developing substrate- specific polymers because the ligand-containing network is woven into a preformed polymer net- work; this allows greater versatility in the prepar- ative scheme since a series of initial networks can exert different microenvironmental effects * Corresponding authors. on the functionalized network and thus yield dif- ferent substrate selectivities. The current report focuses on the complexing properties of IPNs having pyridine and/or carboxylic acid ligands. It was of special interest to determine whether the combination of these ligands in a single IPN would lead to a synergistic effect in the amount of metal ion complexed. There is considerable interest in the develop- ment and use of polymeric reagents for metal ion recovery from waste streams and the environ- ment [3-7]. Polymer-supported reagents offer advantages over solvent extraction techniques, such as elimination of incomplete phase separa- tion and solvent losses through aqueous phase solubility and entrainment. Bifunctional poly- mers and solvent-impregnated resins can provide 0923-1137/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved. SSDI 0923- 1 137(94)00066-2