Influence of Polymer Morphology on the Capacity of Molecularly Imprinted Resins to Release or to Retain their Template

This paper deals with the specific ability of molecularly imprinted polymers (MIPs) to release and/or to retain their template. MIPs for caffeine with various MIP:porogen volume ratios were prepared by a non-covalent route. Formation of a pre-polymerization complex between the template and the functional monomer was confirmed by nuclear magnetic resonance and computer simulation. The MIP monoliths were successively grinded, sieved, and dried under vacuum. The morphology of the imprinted particles was investigated by scanning electron microscopy, swelling experiments and nitrogen adsorption. Typical release patterns of as-synthesised MIP particles in solvents can be decomposed in three fractions: initial release ([straight phi]0 ), slow release over several hours (Δ[straight phi]Release ), permanent retention/encapsulation within the MIP (Δ[straight phi]Reservoir ). The effect of MIP:porogen volume ratio (related to the MIP porosity) on the releasing/retaining profiles of the materials has been investigated. Finally, the results were critically compared with the available literature and the applicability of MIP reservoirs is briefly discussed.