(143f) Self-Cleaning and Anti-Microbial Polyurethane Coatings

A. F. Lotus, Y. Tang, K. Azhie, and P. A. Charpentier*

Department of Chemical and Biochemical Engineering, Faculty of Engineering,

Western University, London, Ontario Canada, N6A5B9

Abstract

Tremendous interest exists for self-cleaning and anti-microbial coatings due to their wide range of potential applications, spanning from surface coatings to textiles. This work has devoloped a new synthesis method for preparing self-cleaning hydrophilic coatings using nano-titanium dioxide (TiO₂) with step-growth polyurethane polymers. The photocatalytic activity of the coatings is attained from a transparent layer of TiO₂ which is made using a ‘grafting from’ polymerization technique with various bi-functional molecules that are coordinated to nano-TiO₂ while providing functionalities for subsequent “grafting from” polymerization. 2,2-bis (hydroxymethyl) propionic acid (DMPA) was chosen for the functionalization with nTiO₂, which is a bifunctional agent with one carboxyl group that can coordinate to nTiO₂,and twohydroxyl groups that can react with diisocyanate terminated pre-polyurethane through step-growth polymerization to obtain functionalized nTiO₂/polyurethane composite coatings. Different physico-chemical characterization techniques were used to verify the coordination reaction between DMPA and nTiO₂ including SEM, TGA, ATR-FTIR, and EDX. The nTiO₂/PU coatings can chemically break down organic dirt and microbes by photocatalysis when exposed to solar irradiation. The antimicrobial behavior was investigated using both gram negative (E. coli) and gram positive (M. luteus) bacteria at different exposure time using a UV lamp and Solar Simulator. The self cleaning property was evaluated by water contact angle measurements on the coating surfaces. The self-cleaning property was also examined using stearic acid and excess DMPA as model compounds for organic dirts, and monitoring the degradation of "dirt" on the surfaces using FTIR spectroscopy analysis. The functionalized nTiO₂-polyurethane composite coatings showed promising self-cleaning property and antibacterial activity against both gram-positive and gram-negative bacteria under UV and solar irradiation.

*To whom it all correspondence should be addressed: Email: pcharpentier@eng.uwo.ca;

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