The enhanced adsorption properties of molecular imprinted polymer material prepared using nitroxide-mediated Radical Deactivation Reversible Polymerization

The origin of the improved performance of Molecular Imprinted Polymers (MIPs) prepared by Nitroxide-Mediated Radical Deactivation Reversible Polymerization (NMRP) and by conventional Free Radical Polymerization (FRP) was investigated through a detailed interpretation of adsorption onto imprinted- and non-imprinted materials. MIPs designed for the adsorption of 3,5-dichlorohydroxyacetophenone (DCHA) were copolymers of methacrylic acid and styrene cross-linked by ethylene glycol dimethacrylate. Modelling the adsorption isotherms using the Langmuir–Volmer model showed that the enhanced adsorption to NMRP MIP was due to a higher density of molecular imprints rather than a higher affinity of the molecular imprints for DCHA. Adsorption was exothermic onto molecular imprints and athermal off them; adsorption caused an increase of entropy. The interactions between monomer and DCHA measured in solution and the influence of pH on adsorption pointed out hydrogen bonding between the MIP carboxylic acids and the DCHA phenol group as the main contribution to adsorption.