Materials assembly using molecular recognition and redox -modulated recognition
The integration of non-covalent interactions in materials provides a direct mechanism to customize materials properties to specific applications and create novel nanostructures. Combining self-assembly with non-covalent interactions serves as a powerful tool in the creation of complex macromolecular structures with thermodynamically reversible contacts. With a host of non-covalent interactions available (e.g. dative bonding, hydrogen bonding, electrostatic pairings, π-stacking), tailoring the size and stability of self-assembled materials can be achieved through choice of interaction. This thesis describes two distinctive areas of research employing a rational combination of self-assembly and non-covalent interactions: (1) the synthesis and self-assembly of recognition unit functionalized Polyhedral Oligomeric Silsesquioxane (POSS) units and (2) the study of redox-modulated, molecular recognition in macromolecular systems.
POSS units have long been employed as covalent additives in both polymeric and ceramic-based systems. Now, they have found alternative uses as non-covalent modifiers in multiple supramolecular systems. POSS units inherently feature a variety of attributes, which make them attractive as molecular recognition elements. These three-dimensional, nanoscale "building blocks" (∼0.6 nm inner silicate core) can easily be functionalized with a variety of recognition units. Through synthetic modification we were able to create a versatile component for non-covalent self-assembly with defined spacial orientations. To that end, recognition unit functionalized POSS units have been shown to serve as potent non-covalent modifiers for applications including surface modification, nanoparticle self-assembly, thermal enhancement in polymeric systems, and potential cellular delivery systems.
Modulating non-covalent interactions via the reduction or oxidation of a molecule serves as an effective means in tuning the formation of supramolecular assemblies. Initial solution-based studies of both non-specific (urea-quinone) and specific, three-point (flavin-diamidopyridine) hydrogen bonding systems have been successful in understanding the complex behaviors, which govern redox-modulated molecular recognition. This understanding led to the incorporation of electrochemically tunable "host-guest" interactions on polymers and surfaces. Several interesting behaviors ranging from reversible redox-modulated recognition to induced proton transfer processes were observed and the ongoing focus of this research seeks to combine materials applications and redox-modulated recognition to create responsive, electrochemically tunable polymers and surfaces.
0794: Materials science