Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Charpentier, Paul A.

Abstract

Antimicrobial/thermochromic dual-functional coatings were successfully synthesized via UV-curing. The quaternary ammonium compound (QAC) N,N-dimethyl-N-{2-[(2-methylprop-2-enoyl)oxy]ethyl}undecane-1-aminium bromide (dMEMUABr) was synthesized and copolymerized with methyl methacrylate (MMA) for antimicrobial properties. Vanadium oxide (VO2) nanoparticles were evenly dispersed within the coating, providing thermochromic properties. The dual-functional coating showed high luminous transmittance (Tlum(25°C) =36.1 %) and solar energy modulation ( Tsol=5.8 %). 90.3 % of bacteria reduction was observed against Escherichia coli within 24 h contact. To further understand the sequence distribution of the copolymer poly(MMA-co-dMEMUABr), the reactivity ratios of MMA and dMEMUABr monomer were studied and compared under thermal and UV initiation copolymerization. In the non-polar solvent chloroform-d, the reactivity ratio of MMA (rMMA=0.06-0.46) was found lower than that of dMEMUABr (rdMEMUABr=6.64-11.51) under thermal copolymerization, which was found consistent for reactivity ratios under UV copolymerization (rMMA=0.73-0.76, rdMEMUABr=4.42-4.48). However, in the polar solvent DMSO-d6, it showed the opposite tendency (rMMA=1.65-1.73, rdMEMUABr=0.24-0.32) attributed to solvent-dMEMUABr monomer interactions.

Summary for Lay Audience

Smart window coatings are considered promising for reducing air conditioning loads to save energy, as they can intelligently regulate the solar radiation and heat transmitted through the window. A further challenge with smart windows is their tendency to foul, as bacteria accumulate on their surfaces. These factors raise health concerns while increasing cleaning costs. This thesis examined synthesizing dual functional coatings, which can both regulate light and heat flow while being antimicrobial. Vanadium dioxide (VO2) nanoparticles were used as the light/heat regulating agents (i.e. thermochromic), which can block undesired infrared light when temperature exceeds its critical temperature (~68 °C). The results showed that the synthesized VO2 nanoparticles were evenly dispersed within the polymer coating, which exhibited thermochromic behavior. The antimicrobial agent, quaternary ammonium compound (QAC) named N,N-dimethyl-N-{2-[(2-methylprop-2-enoyl)oxy]ethyl}undecane-1-aminium bromide (dMEMUABr) was polymerized with methyl methacrylate (MMA) through UV curing using the photo initiator 2-hydroxyl-2-methylpropiophenzssone (HMP). These dual-functional antimicrobial/thermochromic coatings were found to reversibly tune the transmittance of infrared solar radiation to cut the energy consumption, while simultaneously killing attached bacteria to reduce fouling and the resulting pathogenic risk.

To further investigate the copolymerization of dMEMUABr and MMA for coating film preparation, the reactivity ratios of these two monomers were measured. The reactivity ratio values of dMEMUABr and MMA can predict the sequence structure of copolymer chains, which determine the ultimate chemical and physical properties of the copolymer. Therefore, understanding the reactivity ratios is essential for designing and tailoring the copolymer structures for various applications. The reactivity ratios of MMA and dMEMUABr were investigated and compared under thermal and UV initiated copolymerization respectively. The added thermal initiator or photo initiator both produce free radicals to initiate the copolymerization. Two solvents of varying polarity were compared towards reactivity ratios using the polar solvent DMSO-d6 and non-polar solvent chloroform-d. An in-situ NMR technique and conventional low-conversion technique were compared for obtaining data for reactivity ratio calculations. In-situ NMR allows simultaneously monitoring the real-time concentration data for each monomer, providing an efficient, reliable and simple technique for measuring reactivity ratios. This study provided important clues for tailoring the copolymer structure, poly (MMA-co-dMEMUABr), for various applications.

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