Synthesis And Study Of Functionalized Polydimethylsiloxane Block Copolymers: Control Of Surface Properties And Use In Antibiofouling Coatings
Marine biofouling, the settlement of marine organisms on surfaces, is a major problem affecting naval operations and industries including shipping, manufacturing, and water purification. For marine vessels in particular, biofouling leads to increased drag, additional fuel consumption, hull damage, and added maintenance costs. Biocidal coatings containing copper, arsenic, tin, lead, organic biocides, and other are highly effective, and have been used extensively, though these materials are facing increased scrutiny and regulation of coatings. Settlement and adhesion of marine fouling organisms can be effectively controlled using environmentally benign siloxane based coatings. The first study of this work investigates amphiphilic surface active block copolymer additives designed to be incorporated in polydimethylsiloxane (PDMS) network materials. Subsequent work focuses on di- and triblock copolymers of polystyrene-block-poly(methyl polystyrene-block-poly(methyl vinylsiloxane-random-dimethylsiloxane) and vinylsiloxane-random-dimethylsiloxane)-block- polystyrene (PS-b-P(MVS-ran-DMS)-b-PS) that were designed as hydrophobic, low surface energy backbone materials capable of being functionalized via thiol-ene "click" chemistry. This backbone provides a highly customizable platform for screening a wide array of functional groups for antifouling performance. Thiols of hydrophilic chemical groups such as PEG as well as fluoroalkyl and stable radical groups were synthesized and attached to the polymer to control surface chemistry and antifouling performance. Amphiphilic block copolymers, combining both hydrophilic and hydrophobic components, were shown to be very effective in reducing settlement of marine organisms. Additionally, redox active stable radical groups were introduced and shown to disrupt settlement and adhesion of hard foulers such as barnacles which use oxidative adhesive curing. Block copolymer design can control the surface chemistry and was studied using multiple X-ray spectroscopy methods including near-edge Xray absorption fine structure (NEXAFS). Stratification and self-ordering of these films was examined under water using neutron reflectivity. Because of the dynamic nature of these surfaces, the kinetics of surface rearrangement in aqueous environments can be studied by bubble contact angle under water. The antifouling performance of these materials was investigated through collaborative study of settlement, attachment, and removal of fouling organisms such as algae, diatoms, and barnacles. Highly effective coatings were developed by correlating polymer structure, surface chemistry, surface rearrangement characteristics, and antifouling performance.
Disalvo,Francis J; Dichtel,William Robert
Chemistry and Chemical Biology
Ph. D., Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis