Sequence-specific association in a hydrogen binding directed molecular recognition system in aqueous media---The mechanism and application
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This thesis describes a hydrogen-bonding directed associating system that is capable of specific pairing based on the recognition of hydrogen bonding sequence of individual oligoamide strands in aqueous solution. The sequence specific association in aqueous media was achieved by integrating the specificity of multiple hydrogen bonding and the strength of dynamic covalent interactions (disulfide bonds). Experiments were designed to systematically probe the mechanism behind the specific formation of the sequence-matched products, which revealed a thermodymically controlled process. In addition, a length-dependent selectivity was also observed. As few as two hydrogen bonds were sufficient to bias the specific formation of the crosslinked product in aqueous media. The combination of hydrogen bonding and dynamic covalent interactions represents a new, generalizable strategy for developing highly specific molecular associating units that are stable in a wide variety of media. These associating units will greatly facilitate the construction of various structures with many applications. Preliminary results on the synthesis and characterization of polymer networks formed by duplex-mediated disulfide crosslinking are presented. Our studies suggested that the turning points of the specific viscosity (η sp ) -concentration curve was probably not very reliable indications of significant composition change of a solution as proposed by well accepted critical polymerization concentration (CPC) model for supramolecular polymeric assembly processes. Instead, it is more likely that slope change of the η sp - concentration curve reflects the different aggregation status of supramolecular polymeric assemblies in the solution. Elucidating the mechanism behind these supramolecular ii polymeric assemblies would be of fundamental significance to the design of new adaptive materials.