Download files
Abstract
Poly(dopamine) has been actively involved in the development of a wide spectrum of applications ascribed to its chemical versatility and unique properties. This biomimetic functional polymer is generated when dopamine undergoes redox-facilitated self-polymerization, a technique which is also applicable to a range of natural occurring compounds. Polymers generated from these compounds possess functionalities and properties which poly(dopamine) cannot offer. This dissertation describes the extension of the self-polymerization chemistry onto new synthetic monomer candidates which generate polymers with similar structure but different performance to poly(dopamine).
Several heterocyclic catechol derivatives were synthesized, with 5,6-dihydroxy-1H-indazole (DHI) and 5,6-dihydroxy-1H-benzimidazole (DHBI) exhibiting the most promising self-polymerizing ability when subjected to an oxidizing environment. DHI was not able to form polymer coating. It was thus copolymerized with dopamine. The resulting copolymer inherited the low cytotoxicity and coating ability of poly(dopamine), while having pyrazole moieties integrated into the structure as ligands in addition to catechol groups. In contrast, DHBI was capable of forming polymer coatings which modified properties of the coated surface while exhibiting comparable thermal stability to poly(dopamine). Properties of DHBI-based polymer were found tailorable through the integration of desired C-2-substituent during monomer synthesis.
The potential to exploit the DHI-dopamine copolymer as a coordination platform was investigated. Through the 67Ga and 64Cu radiolabeling experiments, the copolymer was found possessing pH dependent binding and release behaviors. The release rate of metal species was also found dependent on their compatibility with the hardness of the ligands carried by the copolymer. Prototypes of nanocarriers were fabricated with the copolymer in the form of nanocapsules, which were decorated with hydrophilic poly[oligo(ethylene glycol) methyl ether acrylate] brushes via one pot in situ grafting-from RAFT polymerization. The presence of polymer brushes was found influential to the loading capacity and metal retention of the nanocapsules.
This work exemplifies the possibility to rapidly expand the range of monomers with redox-facilitated self-polymerizing ability through the synthetic route. The generated functional polymers possess the potential to be employed by a variety of applications.