The Role of Functional Monomer–Template Complexation on the Performance of Atrazine Molecularly Imprinted Polymers

Abstract

The extent of functional monomer–template complexation in noncovalent molecularly imprinted polymer (MIP) prepolymerization mixtures have been examined using 1H‐NMR spectroscopy, and observed complex stabilities have been correlated to polymer–template recognition. The triazine herbicide atrazine was used as a template in molecular imprinting studies using the functional monomers methacrylic acid (MAA), 4‐vinyl pyridine (4‐VP), and an equimolar mixture of the two. Nuclear magnetic resonance (NMR) titration studies using acetic acid, an analogue for MAA, yielded an average apparent dissociation constant (app K diss) of 65 ± 7 mM for atrazine complexation in chloroform (293 K). Studies using pyridine, an analogue for 4‐VP, demonstrated no significant complex formation over the concentration range studied. Atrazine MIPs, and corresponding nonimprinted reference polymers, were synthesized using MAA, 4‐VP, or an equimolar mixture of the two, and were evaluated using high‐performance liquid chromatography (HPLC) and radio ligand binding studies. Importantly, the recognition characteristics of the polymers reflected the observed complex stabilities in the prepolymerization mixtures; thus, MAA MIPs displayed superior recognition and binding capacity compared to polymers prepared with 4‐VP. MIPs synthesized using a combination of MAA and 4‐VP demonstrated intermediate recognition. These results suggest that NMR spectroscopy may be used as a predictive tool for the screening of functional monomers for use in molecular imprinting protocols. Financial support [Swedish Science Council (VR), Carl Trygger's foundation, KK‐foundation, the Graninge Foundation, and the University of Kalmar] is most gratefully acknowledged. We also thank Anna Lilja for excellent technical assistance.