Liu, Xianggeng
Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Chemistry.
DISSERTATION ABSTRACT:
Single-chain nanoparticles (SCNP) are a class of intramolecular cross-linked polymeric nanoparticles with a variety of applications including catalysis, sensors, nanomedicine, and nanoreactors. Such nanoparticles are synthesized by folding or collapsing single polymer molecules. By implementing a single-chain folding technique, the single-chain nanoparticles with uniform degrees of cross-linking are synthesized by parent polymer chains with similar chain lengths and polymer microstructure. Polymer chains that are synthesized by various controlled polymerization techniques can be converted to SCNPs through a variety of covalent chemistry and supramolecular interactions. Based on the expected cross-linking chemistry, related functional groups can be installed either during monomer synthesis or post-polymerization functionalization by utilizing a variety of methodologies. With the goal of effecting catalysis of various organic reactions in aqueous system, we developed a series of ligand functionalized SCNPs with water-soluble pendent groups. N-heterocyclic carbene (NHC) ligands were designed and synthesized to immobilize transition metal cation on SCNPs for catalysis. By employing polymer functionalization strategy, amine-ended ligands, water soluble pendent groups, and cross-linkers were installed by substitution reaction on poly xii (pentafluorophenyl acrylate) (PFPA) synthesized by reversible addition fragmentation transfer polymerization (RAFT), and the process of reaction can be monitored by F19 NMR conveniently. Moreover, to realize inverse temperature dependent controlling, the temperature sensitive watersoluble pendent groups were utilized, such as N-isopropyl amide, which can be installed by the addition of isopropylamine in the process of functionalization of poly (PFPA). Consequently, a variety of organic reactions could be possible in aqueous system catalyzed by combination of different transition metal cations and water-soluble NHC-functionalized SCNP platform.