Coordination of Cu(II) and Ni(II) in polymers imprinted so as to optimize amine chelate formation

Molecular imprinting has become an established technique. However, little was done on direct investigation of the sorbents produced. In the present work, en ESR method was used for the investigation of the complex formation processes within the sorbents imprinted with copper(II) and nickel(II). The sorbents were synthesized from a mixture of linear low molecular weight polyethyleneimine oligomers. The composition, structure and distribution of complexes in the resin phase were investigated. The effects of the synthesis conditions, loading degree and water content were examined. The presence of certain copper complexes was found to be a convenient characteristic of the imprinting efficiency. The optimum synthesis conditions for obtaining sorbents imprinted with copper(II) or nickel(II) were identified. The imprinting results in the improvement of the stability of the complexes and the selectivity and working capacity of the sorbents. The imprinted samples are also characterized by a more even distribution of chelating sites. The synthesis conditions and loading by ions allow for the regulation of the ratio between individual complexes and magnetic associates in the resin phase. This is a critical point on the future use of the metal containing imprinted sorbents as catalysts. (C) 2003 Published by Elsevier Science Ltd

ESTIMATION OF DEPROTONATION COEFFICIENTS FOR CHELATING ION EXCHANGE RESINS. COMPARISON OF DIFFERENT THERMODYNAMIC MODEL

The deprotonation of quinolic resin P-127 and iminodiacetic resin Amberlite IRC-718 has been studied. The process of salt transfer into the resin phase is considered to be an important contributor to the deprotonation process. Estimation of the salt transfer was based on the principle of equal activity of the salt in both phases at equilibrium. Two assumptions were made: sorbed alkali metal ions are not associated with functional groups, while all hydrogen ions are associated with functional groups. The associated hydrogen ions and functional groups do not contribute to the internal ionic strength value. Two thermodynamic models, describing the deprotonation of ion-exchange resin, were used and compared: the Gibbs-Donnan-based model of Bukata and Marinsky and the model proposed by Erik Hogfeldt. Thermodynamic characteristics of the resins’ deprotonation are obtained using two different thermodynamic approaches. Ho¨gfeldt’s three-parameter model provides a better agreement with experimental data. The fitting of the data to Marinsky’s method can be improved by taking into account the influence of the resins’ macroporosity; however, this requires an additional empirical parameter to describe the resin