Abstract:
This thesis presents the synthesis of novel polyaniline (PANI) glycopolymers, with a focus on improving and forming new interaction points between PANI and target bacteria. An improvement in the interaction between PANI and bacteria is hypothesised to increase the inherent antimicrobial ability of PANI improving its potency. The inclusion of azide, alkyne, thiol and alkene functionality to the individual components that will make up the glycopolymer will provide the simple, green and high product yield synthesis of PANI glycopolymers bearing pendant D-mannose and D-glucose by taking advantage of the power of click chemistry. The functionalisation of aniline with a carbohydrate along with subsequent polymerization and the reaction of PANI with a carbohydrate into a PANI glycopolymer were to synthetic routes investigated. The formation of PANI glycopolymers were investigated through a suite of characterisation techniques to confirm carbohydrate attachment and investigate the chemical structures. The synthesised glycopolymers interaction and adhesion with carbohydrate binding proteins (lectins) along with their antimicrobial ability against both gram positive and gram negative bacteria was investigated. Synthesis of a novel aniline bearing D-mannose was successfully completed using an azide-alkyne click reaction. Challenges arose however, upon attempted polymerization resulting in low yields and formation of by-products. A strong interaction with Concanavalin A (ConA) was observed, however, the synthesised glycopolymer was not active at the tested dose range against either gram positive and gram negative bacteria. The reaction of PANI with sulfuric acid towards the formation of a sulfonic acid with subsequent reduction to a thiol allowed the thiol-ene reaction to be utilised with an allylic mannose. While conversion did occur and thiol functional groups were detected it was incomplete and sulfonic acid groups could also still be detected. The covalent bonding of the mannose was recognised by FTIR and XPS and the inability to remove the carbohydrate. The aromatic π structure of PANI was shown to be able to be utilised in the thiol-ene click reaction, which is quite unusual, and promises the ability to synthesise a variety of novel PANI products by reaction with thiol functionalized molecules. The thiol-ene reaction of PANI films with 1-thio-β-D-glucose showed the presence of the glucose on the PANI surface even after attempted removal and displayed enhanced binding with ConA. These films however displayed no antimicrobial ability. Deposition of silver nanoparticles to the synthesised glycopolymers resulted in an significant improvement to their biocidal properties. The nanoparticle formation was shown by a number of imaging techniques and the glycopolymers fully characterized. The current work therefore lays a solid foundation for effective routes to synthesise PANI glycopolymers. The synthesised glycopolymers showed strong interaction with carbohydrate binding proteins in all cases where inspected, however, several displayed no biocidal properties at the concentrations tested. It was shown that silver nanoparticles can be effortlessly deposited on the surface of PANI, providing an antimicrobial surface while retaining the processability of the base form of PANI.