In situ complexation versus complex isolation in synthesis of ion imprinted polymers

In this study, the object is to prove that isolation of complexes made by varying the metal/ligand ratio (in situ complexation) yields similar polymer characteristics, metal binding and selectivity results as polymers synthesized by isolating the complex by precipitation. Complexation between nickel and the N-(4-vinylbenzyl)-2-(aminomethyl)pyridine (Vbamp) monomer was studied in dimethyl sulfoxide (DMSO) and in a DMSO-methanol mixture (50:50, v/v) at 80 °C using a Ni(NO3)2·6H2O salt as the nickel source. According to the results, the three nickel/Vbamp complexes could be selectively obtained using specific conditions: for [Ni(Vbamp)]2 + the Ni/Vbamp ratio in DMSO was 1.08, for [Ni(Vbamp)2]2 + the Ni/Vbamp ratio DMSO-methanol (50:50, v/v) was 0.49 and for [Ni(Vbamp)3]2 + the Ni/Vbamp ratio in DMSO was 0.3. Ion-imprinted polymers (IIPs) were prepared either with [Ni(Vbamp)](NO3)2, [Ni(Vbamp)2](NO3)2, or [Ni(Vbamp)3](NO3)2 complexes as the template. IIP with a [Ni(Vbamp)3]2 + complex, isolated by precipitation prior to polymerization, was also prepared. The results demonstrated that surface properties, nickel binding and selectivity properties were similar for both kind of IIPs - prepared by in situ complexation or isolation of the complex prior to polymer synthesis. Selectivity coefficients of nickel toward zinc for IIPs with [Ni(Vbamp)]2 +, [Ni(Vbamp)2]2 + and [Ni(Vbamp)3]2 + templates were close to 1038, 1441 and 1463, respectively.