IMPROVEMENT FOR CONTROL THE STOICHIOMETRY OF TEMPLATE ION OR MOLECULE/LIGAND COMPLEXES IN SYNTHESIS OF ION AND MOLECULAR IMPRINTED POLYMERS
2Laboratoire Chimie de l'Environnement, Aix-Marseille University
3Laboratory of MIO, University of Toulon
4Laboratory of Separation Technology, Lappeenranta University of Technology
5Laboratory of MAPIEM, University of Toulon
The aim of this study is to propose In situ complexation method as a simple way to control the stoichiometry of template ion or molecule//ligand complexes.1 In this method, absorption spectra at different template ion or molecule/ligand ratio are first measured by UV/vis spectrophotometer in water or specific solvent mixture. Then stability and extinction coefficients are calculated by commercial HypSpec program based on the least-squares minimization scheme.2 Stoichiometry of template ion or molecule/ligand complexes can be calculated at different template/ligand ratios and under some conditions (solution, temperature) different complex structures can be isolated. Finally IIPs/MIPs can be synthesized via normal procedures. In this study, 1-(pyridin-2-yl)-N-(4-vinylbenzyl)methanamine (Vbamp) monomer3 was used as chelating ligand and nickel as the template ion. Relative amounts of 1:1, 1:2, and 1:3 complexes in the prepolymerization medium were adjusted by changing the Ni/Vbamp ratio, the counter-anion and the solvent composition at the polymerization temperature. After characterization of the complex distribution by UV/vis spectroscopy, IIPs were synthesized by inverse suspension polymerization with EDMA as the crosslinking agent. For the sake of comparison, 1:3 Ni/Vbamp complexes were also isolated using precipitation method and used for the preparation of control IIPs. The results showed that using In situ complexation method, selectivity of IIPs for nickel was as high as by isolating the complexes using precipitation method. The results of this study are step-forward in imprinting technique development. As complex adjustment can be quite easily performed, it simplifies IIP/MIPs preparation process when complicated complex isolation methods (crystallization, precipitation) are not possible or necessary. Furthermore, in the case of IIPs selectivity is also dependent on the solvent used in the polymerization. This work gives therefore more options to adapt the solvents because redissolution of isolated complexes is not problematic anymore. The only limitation is that this method is only suitable for the complexes which can be detected by UV-vis spectrophotometer.
References
[1] Laatikainen, K Branger, C, Coulumb, B., Lenoble,V., Sainio, T. (2018) In situ Complexation versus Complex Isolation in Synthesis of Ion Imprinted Polymers, Reactive and Functional Polymers 122: 1-8,
[2] Gans, P, Sabatini, A, Vacca, A (1985) SUPERQUAD: An improved general program for computation of formation constants from potentiometric data. Journal of Chemical Society Dalton Transactions: 1195-1200.
[3] Laatikainen, K, Udomsap, D, Sirén, H, Brisset, H, Sainio, T, Branger, C (2015) Effect of template ion-ligand complex stoichiometry on selectivity of ion-imprinted polymers Talanta 134: 538-545.
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