Abstract:
High operational and maintenance costs are significant problems associated with
the fouling of marine vessels. Traditionally, fouling of such vessels was mitigated via
paints, applied below the water line, that released organometallic compounds that were
toxic to fouling species. Increased regulation of these paints has stimulated much
research in the development of environmentally benign alternatives and replacements.
Low surface energy materials, such as silicone elastomers and fluoropolymers
have shown great promise due to their ability to resist both initial microbial colonization,
as well as their “fouling release” characteristics. However, the implementation of these
materials in the form of marine coatings is problematic, and the development of a suitable
antifouling coating remains elusive. In order to maximize the efficiency of marine
coatings, the development of materials with multiple antifouling mechanisms is required.
This thesis describes a series of polymeric materials that exhibit a combination of three different approaches to fouling: low surface energy, antimicrobial activity, and
hydrolysability.
Novel polymer coatings with low surface energy domains, tethered broad
spectrum antimicrobials, and non-toxic hydrolysable linkages have been synthesized.
Low surface energy materials have shown great promise in reducing adhesion and
colonization of microbes at surfaces and remain a suitable first line of defense.
Additionally, low surface energy domains may provide the ability for materials to release
accumulated fouling via hydrodynamic/sheer forces as a ship moves through the water.
Despite reduced adhesion and fouling release properties that are well known for
low surface energy materials, microbes are still able to colonize at the surface, which
typically led to the formation of biofilms. To minimize the formation of biofilms from
adhered microbes, quaternary ammonium salts (QAS) were incorporated into the
urethane backbone to provide an effective active antimicrobial defense mechanism.
Finally, incorporating a non-toxic hydrolysable linkages provide the material with
a renewable character allowing a gradual sloughing of the coatings to continuously
provide fresh active antimicrobial interfaces. The gradual sloughing of the coatings
provides a second mechanism of fouling release due to the constant renewal of the
surface which is capable of removing any fouled portions of the coating. Synthesis,
structure-property relationships, and antifouling behavior of these materials are detailed.