Biocidal polymers active by contact. III. Ageing of biocidal polyurethane coatings in water

Abstract

AbstractPolyurethane coatings prepared from hydroxytelechelic polybutadiene with pendant qua‐ternary ammonium salts (QAS) are able to kill microorganisms, these biocidal polymers were submitted to various ageing conditions. The activity remained constant after exposure to a very high number of bacteria (Escherichia coli). Nevertheless immersion in water caused a slow decrease of activity with time whatever the QAS examined (N+R2R′ with R = Me or Bu and R′ = n‐octyl to n‐hexadecyl). The phenomenon can be analysed in two stages. The first one, short (5–10 days) and limited, is due to the diffusion of a water‐soluble synthesis residue. At the end of this period, the samples are still active and the activity is only due to a contact polymer‐bacteria. The second stage is much slower and is accompanied by a transformation of QAS in amine. This is attributed to an equilibrium between QAS, amine, and alkyl bromide slowly shifted toward the formation of amine because of a weak solubility of alkyl bromide in water. Increasing the lipophilicity and bulkiness of the QAS substituents improves the durability of the biocidal activity. Some samples still exhibit a good activity after more than 1 year of ageing in harsh conditions. © 1993 John Wiley & Sons, Inc.