Characterization of the Network Structure of Molecularly Imprinted Polymers by Determination of Kinetic Chain Length Distribution
Vishal D. Salian and Mark E. Byrne. Biomimetic & Biohybrid Materials, Biomedical Devices, and Drug Delivery Laboratories, Department of Chemical Engineering, Auburn University, Auburn, AL 36849-5127
Living/controlled polymerization has been reported to enhance the binding characteristics of imprinted polymer networks, which has been hypothesized to be due to improved structural homogeneity of the binding sites and a global energy minimum of the spatial arrangement of polymer chains. Macromolecular memory within imprinted networks are due to two synergistic effects: (i) shape specific cavities that match the template molecule, which provide stabilization of the chemistry in a crosslinked matrix, and (ii) chemical groups oriented to form multiple non-covalent complexation points with the template. Increased potential for the growing polymer network and template binding complexes to reach a global energy minimum can lead to further memorization of the chain conformation and enhance binding parameters in both highly crosslinked and weakly crosslinked polymers. This work demonstrates the effect of template molecules that non-covalently interact with functional monomers on the distribution of the resulting linear polymer chains in both conventional free-radical polymerization and living/controlled polymerization. Kinetic chain length distributions were studied in both conventional and living/controlled free-radical polymerization reactions by varying functional monomer/template and iniferter/conventional photoinitiator ratios. Results highlight as the strength of the monomer template interaction and the monomer/template ratio increase, there is a more pronounced effect on the distribution of polymer chains. In addition, binding studies performed on the imprinted polymer networks yielded the imprinting efficiency of the polymer. The results confirm that improved structural homogeneity of the binding sites and a global energy minimum of the spatial arrangement of polymer chains lead to enhanced binding parameters.