Novel approaches to the controlled release of Quaternary ammoniun-based biocides

The major economic and environmental consequences of unfettered growth of marine organisms (fouling) on any substrate immersed in the marine environment have a global reach. Currently biocidal antifouling coatings are the most widely employed method to control this growth on vessels. These coatings are under increasing legislative scrutiny because they release primarily metal-based biologically active agents (biocides) to deter the fouling, and hence have the potential to persist in some form in the environment. This thesis explores the potential use of organic salt-based biocides, quaternary ammonium compounds (quats), as new marine biocides which are considered to be environmentally benign due to their short environmental half-lives. Detailed are methodologies to control the release of the quats as well as a new liquid chromatography (LC) mass spectroscopy (MS) analytical method to quantify the quats in seawater. The primary focus of the controlled release research has been the development of novel quat-polymer systems, which hydrolyze in the presence of seawater to generate biocidal quats in-situ. The quat-polymers are synthesised via a free radical polymerisation from different monomers, which are a blend of commercial available film forming monomers and a novel quat-monomer. The preparation of the quat-monomer is also detailed within this thesis. The quat-polymers have been shown to be stable in a prototype antifouling paint formulation and several coatings have been developed which exhibit significantly better antifouling performance than a current commercial product, Intersmooth 460, even after over 1 year with the testing continuing. The developed LC-MS method utilizes a sample pre-treatment solid phase extraction (SPE) process and is capable of quantifying quats to low parts-per-trillion (ppt) levels in seawater. The method is exceptionally flexible and able to detect a range of commercially available quats simultaneously. The application of this method to the determination of the release rates of the quats from antifouling coatings under standard laboratory conditions is also outlined.