| Molecular self-assembly can be used to construct advanced materials by taking cues from nature and harnessing noncovalent interactions. This bottom-up approach affords molecular level precision that can cultivate pathways to improved materials function. The graduate research presented in this thesis integrates molecular self-assembly with traditional concepts in chemistry and materials science, with the ultimate goal of developing innovative solutions in technology and medicine. In the field of polymer engineering, self-assembly was used to create supramolecular nanoribbons that, when incorporated into polystyrene, modify its microstructure and significantly enhance its toughness and ductility. In medicine, self-assembly was used to create ordered, chemically functional materials to improve interactions with cells and other constituents of the biological environment. One system that was investigated is based on a triblock molecule in which cholesterol is connected to a lysine dendron by a flexible oligo-(L-lactic acid) spacer. These molecules self-assemble into polar surface coatings on fibrous poly(L-lactic acid) scaffolds that improve the scaffold's wettability and increase its retention of cells during seeding. Another self-assembling system that was investigated for biomedical applications is a family of molecules referred to as peptide amphiphiles (PA's). PA's consist of hydrophobic alkyl tails connected to short, hydrophilic peptides that incorporate biological signaling epitopes. These molecules spontaneously assemble into networks of well-defined nanofibers in aqueous environments, with the signaling epitopes presented in high density on the nanofiber exteriors. Nanofiber assembly is triggered by charge screening on the peptides and is able to produce self-supporting gels in concentrations of less than 1.0 wt.-%. The assembly process and mechanical properties of PA gels was investigated in detail with vibrational spectroscopy and oscillatory rheology. PA nanofibers were used in conjunction with fibrous poly(L-lactic acid] fabrics to create chemically functional scaffolds to facilitate islet cell transplantation. In transplant studies in diabetic mice, the use of scaffolds for islet delivery was shown to significantly improve transplant outcomes over free islet injections. Together, these studies illustrate that molecular self-assembly can be used to create functional materials for a variety of applications. These materials utilize noncovalent interactions to produce supramolecular structures that have important impacts on properties. |
