Synthesis of cationic cyclic polymers

• Main Author: Yue, Wendy
• Other Authors: Duan Hongwei
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/68193
• Institution: Nanyang Technological University

Microbial infections threaten the health of people worldwide and cause various illnesses such as diarrhea and urinary tract infections among many others. One big concern is the rise of resistant bacteria due to their ability to mutate-and adapt fast following the introduction of new antimicrobials, making it difficult for their eradication. To counter this problem, extensive studies have been done to develop vastly efficient antimicrobials that have lower susceptibility to bacterial resistance. One such antimicrobial material that is shown to be promising is Poly-(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). This project reports the successful synthesis of cationic cyclic polymers and its antimicrobial activity on Staphylococcus aureus (S. aureus) bacteria cells. Cationic cyclic PDMAEMA was synthesized via intra-chain click cyclization of linear PDMAEMA prepared by atom transfer radical polymerization (ATRP). Synthesized polymers were characterized by 1H NMR, FTIR spectroscopy and GPC. It was shown that synthesis of well-defined cationic PDMAEMA with low polydispersity indices (PDI) via ATRP and intra-chain click cyclization was feasible and successful. Minimum Inhibitory Concentrations (MIC) of both polymers were obtained by microdilution broth dilution test and it was found that cyclic PDMAEMA had lower MIC value (1.25 mg mL-1) than linear PDMAEMA (2.5 mg mL-1), showing that cyclic PDMAEMA has greater antimicrobial activity. This could be due to the smaller hydrodynamic radius of cyclic PDMAEMA which creates a higher concentration of local charges, increases electrostatic interactions between polymer and bacterial cell wall, causing cytoplasmic leakage and eventual cell death.