Grafted thermo- and pH responsive co-polymers: Surface-properties and bacterial adsorption

A series of responsive polymers displaying pH and temperature-mediated phase changes were prepared from N-isopropylacrylamide and ω-carboxylic acid functionalised acrylamides. These polymers were grafted to surfaces and their characteristics probed by atomic force microscopy in aqueous solutions. The effects of pH and temperature induced phase transitions on the short-term adsorption of the bacteria Salmonella typhimurium and Bacillus cereus from pure cultures were assessed. Contact angle studies indicated that pH and temperature-dependent surface properties were exhibited by the graft polymer surfaces. Temperature-dependent surface morphology changes occurred through polymer graft phase transitions as observed in AFM and accompanying changes in adhesion forces underwater were found to correlate with surface properties obtained from contact angle measurements. Adsorption of S. typhimurium and B. cereus was not significantly altered as a function of pH, but attachment of both bacterial strains increased at temperatures above the polymer coil-globule transition indicating the importance of switching surface hydrophobicity in controlling short-term bacterial adsorption.