Molecularly Imprinted Polymer Microspheres And Recognition Performance

Molecularly imprinted polymer (MIP) is a kind of synthetic polymer with specific recognition properties. A template that can interact with the polymerizable functional monomer is employed in order to facilitate recognition site formation during the crosslinking polymerization, with subsequent removal of some or all of the templates being necessary for recognition to occur in the spaces vacated by the templating species. MIP has an extensive application in chromatography separation and purification, solid extrusion, biological and chemical sensors, catalysts and relevant fields for its predetermination, specificity and practicability of molecularly recognition.MIP prepared by traditional bulk polymerization need to be ground and sieved to obtain appropriate particle size. This procedure is labor and time consuming and the obtained copolymer particles with irregular shape have low binding capacity and poor site accessibility for the template molecules. Polymer microspheres prepared by emulsion polymerization and suspension polymerization have low binding ability and narrow application fields because of the surfacants which need sophisticated operation to remove. In this thesis, TNT was used as template, EDMA was used as crosslinking agent, acetonitrile was used as solvent and porogen and AIBN was used as initiatives. TNT molecularly imprinted microspheres were prepared first time by precipitation polymerization without any other additives.The synthetic conditions of the precipitation polymerization were studied extensively. SEM was utilized to observe the morphology of the microspheres. The results showed that the morphology was affected by the amount of solvent, template, cross-linker and initiative used in the polymerization process. The species of the functional monomer also have an impact on the morphology of the microspheres. The optimum synthetic conditions were found as follow: Using AM as functional monomer, the ratio of the template, functional monomer and the crosslinking agent was 1:4:20, the synthesized polymer particles were regularly spheres and the diameter of the particles 1μm～2μm.The interaction between the templates and the functional monomers was determined by UV adsorption spectrum. The structure of the synthesized microspheres was investigated by FTIR, TGA and BET method. The results showed that the templates can interact with the functional monomers to form stable complexes and the binding sites and molecularly caves were constructed in the microspheres.The recognition capability was studied by equilibrium binding experiment. The result showed that the speed of the molecularly imprinted polymer microspheres binding templates was twice faster as the traditional bulk MIP, and the MIP showed specific binding property. The equilibrium binding capacity of the microspheres in TNT/alcohol solution with the concentration of 5mmol/L was 100.59mmol/kg, while the binding capacity of NMIP was 43.66mmol/kg. MIP showed recognition property in the selective bingding experiment. The selective coefficient of MIP binding TNT in contrast to o-MNT was 2.30.We tried to introduce magnetic susceptibility to MIP in order to facilitate MIP with the ability to sediment faster in magnetic fields. Molecularly imprinted polymer microspheres with magnetic susceptibility were prepared first time by adding modified magnetic particles in the process of the polymerization. The sedimentation speed of the synthesized magnetic microsphere was improved remarkably in the external 0.52T magnetic field. The binding capacity and the recognition ability of the magnetic MIP microspheres were slightly reduced in contrast to that of ordinary MIP paritcles. The equilibrium binding capacity of the magnetic MIP in TNT/alcohol solution with the concentration of 5mmol/L was 93.02mmol/kg and the selective recognition coefficient of magnetic MIP binding TNT and o-MNT was 2.06.