pH responsive properties of non-fouling mixed-charge polymer brushes based on quaternary amine and carboxylic acid monomers

In this work, we report a tunable mixed-charge copolymer surface containing positively charged quaternary amine monomers ([2-(Acryloyloxy)ethyl] trimethyl ammonium chloride, TMA) and negatively-charged carboxylic acid monomers (2-carboxy ethyl acrylate, CAA). The non-fouling properties of this copolymer coating depend on environmental pH. The surface has charge neutrality under neutral and basic conditions, and is positively charged under acidic conditions due to the protonation of the carboxylic acid group. This transition in surface charge with respect to pH allows the surface to be switched from bacteria-adhesive to bacteria-resistant. We demonstrate that the bacteria adhered to the surface under acidic conditions can be easily released as bulk pH increases. This tunable surface can be used to collect a contaminant and then be externally stimulated to release the contaminant, to allow for analysis of its composition. Its bacteria attraction and release property makes it very promising for decontamination and biomedical applications.