Seok-Bong Choi

Silicones Containing Pendant Biocides for Antifouling Coatings

The preparation of biocide-incorporated silicone coatings for antifouling/fouling release applications is described. The biocide Triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol) was modified with alkenyl moieties and incorporated into a silicone backbone through covalent bonds. The presence of the biocide on the coating surface was expected to deter fouling organisms from attaching to the surface of the coating. Allyl glycidyl ether was used to provide crosslink functionalities. Resins were cured using vinyl-terminated polydimethylsiloxane for hydrosilyl functionality and 1, 3-cyclohexane-bis (methylamine) for epoxy crosslinking functionality. Coatings were characterized by static water contact angle measurements and dynamic mechanical thermal analysis. Synthetic control over the incorporation of crosslink functionalities within the polymer resin allowed tuning of the surface of the coating and of mechanical properties. Resistance to macrofouling was tested by static immersion tests in the Indian River Lagoon at the Florida Institute of Technology from 15 October 2003 to 13 November 2003. Preliminary results showed that the coatings prepared from biocide-incorporated silicones with the appropriate bulk modulus significantly reduced macrofouling.

Synthesis and characterization of dibenzannulated silole dianions. The 1,1-dilithiosilafluorene and 1,1′-dilithiobis(silafluorene) dianions

Abstract Stirring of 1,1-dichloro-SiFl ( 1 ), (SiFl, silafluorene) in THF with excess lithium for 1 h gave a dark green solution of 1,1-dilithio-SiFl ( 2 ) in high yield. The dark red solution of the intermediate 1,1′-dilithio-(SiFl) 2 ( 3 ) was also observed from this reaction within 10 min. Treatment of 2 with excess trimethylchlorosilane gave the 1,1-bis(trimethylsilyl)-SiFl derivative ( 4 ) in 95% yield. Treatment of the dark red solution of 3 and 2 with excess methyliodide gave the 1,1′-dimethyl-bis(SiFl) ( 5 ) and 1,1-dimethyl-SiFl ( 6 ) derivatives in a 4:1 ratio. The upfield locations of the 29 Si resonances of dianions 2 and 3 (−1.09 ppm and −39.25 ppm, respectively) are consistent with π-electron localization on the silicon atoms.

Nickel catalyzed silane reductions of α, β - unsaturated ketones and nitriles

Abstract Activated nickel, produced by the ultrasound-promoted reduction of nickel iodide with lithium, catalyzes the 1,4 addition of phenylsilane to α, β-unsaturated ketones and α,β -unsaturated nitriles to give, after hydrolysis, high yields of the products of 1,2 hydrogenation.

Finite Element Analysis of Thickness Dependent Debonding Forces of Elastomer Coatings

Adhesion tests consisting of cylindrical studs to be pulled off from a soft elastomer coating on a substrate have been widely performed in the literature to characterize various biofouling and adhesive situations. These experiments have shown that the pull-off forces are strongly dependent on the coating thickness. To understand this thickness dependence on the debonding forces, a detailed analysis is performed by the finite element method, applying the virtual crack closure technique. In these simulations, coating thickness, elastic modulus, and initial geometries have been varied to study their influence on the debonding forces. The effect of these factors on the debonding forces is discussed with respect to experimental pull-off results of silicone coatings.