title: Contact angle anomalies indicate that surface-active eluates from silicone coatings inhibit the adhesive mechanisms of fouling organisms.
abstract: Silicone coatings with critical surface tensions (CST) between 20 and 30 mN m-1 more easily release diverse types of biofouling than do materials of higher and lower CST. Oils added to these coatings selectively further diminish the attachment strengths of different marine fouling organisms, without significantly modifying the initial CST. In a search for the mechanisms of this improved biofouling resistance, the interfacial instabilities of four silicone coatings were characterised by comprehensive contact angle analyses, using up to 12 different diagnostic fluids selected to mimic the side chain chemistries of the common amino acids of bioadhesive proteins. The surfaces of painted steel test panels were characterised both before and after exposure to freshwater, brackish water, and seawater over periods ranging from 9 months to nearly 4 years. Contact angle measurements demonstrated significant surface activity of the oil-amended coatings both before and after long-term underwater exposure. The surface activity of the control (coating without oil) increased as a result of underwater exposure, consistent with mild surface chain scission and hydrolysis imparting a self-surfactancy to the coating and providing a weak boundary layer promoting continuing easy release of attaching foulants. Coatings with additives that most effectively reduced biofouling showed both initial and persistent contact angle anomalies for the test liquid, thiodiglycol, suggesting lower-shear biofouling release mechanisms based upon diminished bioadhesive crosslinking by interfering with hydrogen- and sulfhydryl bonds. Swelling of the silicone elastomeric coatings by hydrocarbon fluids was observed for all four coatings, before and after immersion.
authors.affiliation: Industry/University Center for Biosurfaces, University at Buffalo, Buffalo, New York 14214, USA. aemeyer@buffalo.edu
authors.forename: Anne
authors.initials: A
authors.lastname: Meyer
authors.forename: Robert
authors.initials: R
authors.lastname: Baier
authors.forename: Christina Darkangelo
authors.initials: CD
authors.lastname: Wood
authors.forename: Judith
authors.initials: J
authors.lastname: Stein
authors.forename: Kathryn
authors.initials: K
authors.lastname: Truby
authors.forename: Eric
authors.initials: E
authors.lastname: Holm
authors.forename: Jean
authors.initials: J
authors.lastname: Montemarano
authors.forename: Christopher
authors.initials: C
authors.lastname: Kavanagh
authors.forename: Brian
authors.initials: B
authors.lastname: Nedved
authors.forename: Celia
authors.initials: C
authors.lastname: Smith
authors.forename: Geoff
authors.initials: G
authors.lastname: Swain
authors.forename: Deborah
authors.initials: D
authors.lastname: Wiebe
mesh_terms: D000268:Adhesiveness / Q000187:drug effects; D000818:Animals; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005618:Fresh Water; D008422:Materials Testing; D010150:Paint / Q000032:analysis; D012623:Seawater; D012826:Silicone Elastomers / Q000737:chemistry*; D013232:Steel; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D012826:Silicone Elastomers; D013232:Steel