Development of permanently antimicrobial coatings

[摘要] ENGLISH ABSTRACT: Water-borne coatings often contain multiple additives including pigments, dispersing agents,rheology modifiers, UV stabilizers and biocides. Due to their low molar mass and endocrinedisruptingproperties, many of these additives, upon leaching from the substrate film, with timepollute water systems and become hazardous to the environment and to human health. In this study,I aimed to develop a facile method for the production of a polymeric biocide to serve as alternativeto low molar mass biocides used in water-borne coatings. A secondary aim was to show that,without additional modification, the polymeric species can be used in surfactant-free ab initioemulsion polymerizations.Using a two-step process, I modified a commercially available copolymer, poly(styrene-alt-maleicanhydride) (SMA 1000), with mixed amines in order to obtain latexes with inherent antimicrobialactivity. In the first step, I reacted SMA 1000 with 3-dimethylamino-1-propylamine and aqueousammonia to confer antimicrobial activity and water-solubility to the SMA copolymer. In the secondstep, the copolymer was incorporated into a film-forming styrene-butyl acrylate (STY/BuA) latex.The modified SMA was incorporated into a latex in two ways: (1) post-added to the latex, and (2)used as stabilizer in emulsion polymerization. In both cases, the latex remained stable for up to 11months, and stability was probably due to steric stabilization of the polymer particles. Antimicrobialactivity of the latex film was achieved with both methods. When the modified SMA was post-added,antimicrobial activity was restricted to specific areas on the eventual polymer film, and whenmodified SMA was used as stabilizer, antimicrobial activity was evenly distributed throughout thepolymer film.Fluorescence microscopy showed homogeneous distribution of antimicrobial activity uponinoculation in Gram positive bacteria dispersions when the modified copolymer was used aspolymeric stabilizer for the synthesis of STY/BuA latexes. No antimicrobial activity against Gramnegative bacteria was achieved. The homogeneous distribution of antimicrobial activity throughoutthe film was a result of adsorption of polymeric biocide/stabilizer to each individual latex particle.With further commercial development, high molar mass copolymers modified for antimicrobialactivity may be a feasible, environmentally-friendly and healthy alternative to be used as stabilizersin emulsion polymerizations to produce water-borne coatings.

[发布机构] Stellenbosch University