Molecularly Imprinted Polymer Microspheres ContainingPhotoswitchable Spiropyran-Based Binding Sites

摘要

A versatile approach for the preparation of photoswitchable molecularly imprinted polymers (MIPs) is proposed where the selective recognition and the photoresponsive function are assumed by two different monomers. As a proof of concept, MIP microspheres were synthesized by precipitation polymerization for recognizing terbutylazine, a triazine-type herbicide. Formation of the selective binding sites was based upon H-bonding interactions between the template and the functional monomer methacrylic acid, whereas a polymerizable spiropyran unit was incorporated into the polymer matrix to provide light-controllable characteristics. A trifunctional monomer, trimethylolpropane trimethacrylate, was used as a cross-linker. The imprinted particles exhibited considerable morphological differences compared to their nonimprinted counterparts as observed by scanning electron microscopy. The imprinting effect was confirmed by equilibrium rebinding studies. The photoresponsiveness of the polymer particles was visualized by fluorescence microscopy and further characterized by spectroscopy. The template binding behaviorcould be regulated by alternating UV and visible light illuminationwhen analyte release and uptake was observed, respectively. Bindingisotherms fitted by the Freundlich model revealed the photomodulationof the number of binding sites and their average affinity. This facilesynthetic approach may give an attractive starting point to endowcurrently existing highly selective MIPs with photoswitchable properties,thereby extending the scope of spiropyran-based photoresponsive smartmaterials.