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Title: Novel biocidal formulations : the effect of polymer structure on antibacterial activity and aqueous solutions behaviour
Author: Alzahrani, Fatimah
ISNI:       0000 0004 7657 5548
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2017
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New strains of bacteria have developed resistance to many of the limited number of antibiotics currently available in the market. The use of conventional antimicrobial agents is also increasingly subject to restrictions because of the environmental damage arising from the toxicity of their residues. These factors strongly justify research into ways of fighting these microorganisms physically rather than chemically, reducing the quantities of antibacterial agents used while maintaining antibacterial activity for longer. This study is in three main parts. The first involves the synthesis of four series of quaternary ammonium compounds whose main constituent is a cationic monomer, poly [2-(methacryloyloxy) ethyl trimethylammonium chloride] (MADQUAT). Two types of cationic polymer were synthesized: a) statistical copolymers of MADQUAT and either methyl methacrylate (MMA) or poly (ethyleneglycol) methyl ether methacrylate (PEGMA) and b) amphiphilic di-block polymers. The statistical copolymers poly (MADQUATx-s-MMAy) and poly (MADQUATx-s-PEGMAy) were prepared by the one-pot method of a modified conventional free-radical polymerization using 2,2'-azobis (2-methyl butyronitrile) as initiator. The amphiphilic di-block polymers were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The resultant products were characterized by several techniques: aqueous GPC, 1H NMR, Zeta potential and DLS. The behaviour of aqueous solutions of both types of cationic polymer was investigated by studying surface tension, pyrene fluorescence and viscosity; the results indicate that these polymers are not surface active. The behaviour and critical aggregation concentration of both di-block and statistical cationic polymers in aqueous solution were significantly affected by polymer structure and the molar ratio of MADQUAT to MMA. The second part of the study investigates the interactions between like-charged cationic surfactant didecyl dimethyl ammonium chloride (DDAC) and polyelectrolytes: a homopolymer, poly MADQUAT, statistical copolymers poly (MADQUATx-s-MMAy) and di-block polymers poly (MADQUATx-b-MMAy). In each case the system separates into a lower polyelectrolyte-rich and an upper surfactant-rich phase with different phase separation boundaries, confirmed by 1H NMR. The third part of the study measures minimum inhibitory concentrations of these polymers against both gram-positive and gram-negative bacterial strains, finding that these polymers have an interesting antibacterial activity. However, the structures of cationic polymers have an insignificant impact on antibacterial activity.
Supervisor: Yeates, Stephen ; Webb, Michelle Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Polymers ; Antibacterial Material ; Phase Separation ; Quaternary Ammonium Compounds