Cu(I) stabilizing polymers for marine anti-fouling applications

Doctoral thesis, 2015

The growth of marine organisms on immersed surfaces in seawater is known as biofouling and causes several problems for marine transportation. The need to combat fouling is thus of great importance. Copper has to be used in extreme amounts to act as an efficient biocide. Consequently, several countries have restricted the use of copper based paints due to the adverse effect of high copper concentration on the environment.Both Cu(I) and Cu(II) ions are considered to be toxic for marine foulers, although Cu(I)is generally accepted to be the form of Cu that passes through the biological membranes. At the same time, Cu(I) is unstable in the marine environment and rapidly oxidizes to Cu(II). The stability of Cu(I) ions may however be increased by using Cu(I)-stabilizing coordinating ligands in the coating. The idea behind this project is to have a coating that can absorb the abundant Cu(II) ions in the seawater with the ability to stabilize the Cu(I)oxidation state in the presence of naturally occurring reducing agents with the aim of improving the anti-fouling effect at the coating interface with the seawater. As the first phase of this project, in this thesis, we present several synthetic routes to prepare different variants of polymers based on triazole ligands for further use in marine applications. To do so, we have used robust and high performance chemical reactions such as the Cu-catalyzed alkyne-azide cycloaddition, epoxy ring opening, and reductive amination to modify commercially available polymers in order to increase their affinity to stabilize Cu(I). The synthetic methods employed, the physical and chemical properties of the polymers, as well as their performance upon interaction with Cu ions in solution, is described. The different triazole-containing coordinating polymers which are introduced in this work not only absorb relatively high levels of Cu(II) ions from a Cu(II) solution (5 to 12 wt%), but can also effectively stabilize Cu(I) ions which are produced in the presence of a mild reducing agent such as sodium ascorbate.