Synthesis of a Novel Diblock Copolymer and Preparation of Highly Selective Molecularly Imprinted Polymer Nanospheres from It
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Crosslinking monomers or a polymer around template molecules and the subsequent removal of the templates yield a polymer matrix containing cavities that resemble the shape of the templates and bear binding groups that complement those on the template molecules. However, a key challenge facing those molecularly imprinted polymers (MIPs) is the infidelity of the pores generated to the original templates and thus non-specific binding of the pores to analytes other than the template. I report in this thesis a method to improve the selectivity of MIP particles. I prepared an MIP for a chiral analyte relying not only on the traditional H-bonding interactions between the polymer matrix and the template but also on the - stacking interactions. Specifically, I synthesized a novel diblock copolymer poly(ethylene oxide)226-block-poly[(2-pentafluorocinnamoyloxyethyl methacrylate)75%-ran-[2-(2’-carboxybenzoyloxy)ethyl methacrylate]25%]100 or PEO226-b-P(FEMA75%-r-CA25%)100. While the CA groups were introduced because of their H-bond interactions with carbonyl oxygen and amino group of the chiral template D-phenylalanine anilide, the FEMA units were introduced for their ability to crosslink under the UV irradiation and also for the π-π stacking interactions of the fluorinated FEMA phenyl rings with the phenyl rings of D-phenylalanine anilide. To prepare MIP nanoparticles, I first dispersed the diblock copolymer and D-phenylalanine anilide in chloroform/methanol at 95 vol% of methanol to prepare micelles that bore PEO coronal chains and a P(FEMA-r-CA) core that complexed with D-phenylalanine anilide. I then photocrosslinked the micellar core and locked the FEMA and CA units around the template molecules. In a third step, I extracted out D-phenylalanine anilide using a solvent. I discovered that these crosslinked MIP nanoparticles had a selectivity of 6.3 towards the binding of D-phenylalanine anilide over L-phenylalanine anilide. This represented a 70% increase in selectivity of MIP nanoparticles prepared from an analogous approach by replacing PEO226-b-P(FEMA75%-r-CA25%)100 with PEO226-b-P(CEMA75%-r-CA25%)100, where CEMA is the hydrogenated version of FEMA. I believe that my work pinpoints the opportunity for using π-π stacking interactions between fluorinated and hydrogenated aromatic rings for improving the selectivity of MIPs and the potential of using this interaction in future for developing highly selective MIPs.