Philip Boudjouk

Combinatorial materials research applied to the development of new surface coatings IX: An investigation of novel antifouling/fouling-release coatings containing quaternary ammonium salt groups

Polysiloxane coatings containing chemically-bound (“tethered”) quaternary ammonium salt (QAS) moieties were investigated for potential application as environmental-friendly coatings to control marine biofouling. A combinatorial/high-throughput approach was applied to the investigation to enable multiple variables to be probed simultaneously and efficiently. The variables investigated for the moisture-curable coatings included QAS composition, ie alkyl chain length, and concentration as well as silanol-terminated polysiloxane molecular weight. A total of 75 compositionally unique coatings were prepared and characterized using surface characterization techniques and biological assays. Biological assays were based on two different marine microorganisms, a bacterium, Cellulophaga lytica and a diatom, Navicula incerta, as well as a macrofouling alga, Ulva. The results of the study showed that all three variables influenced coating surface properties as well as antifouling (AF) and fouling-release (FR) characteristics. The incorporation of QAS moieties into a polysiloxane matrix generally resulted in an increase in coating surface hydrophobicity. Characterization of coating surface morphology revealed a heterogeneous, two-phase morphology for many of the coatings investigated. A correlation was found between water contact angle and coating surface roughness, with the contact angle increasing with increasing surface roughness. Coatings based on the QAS moiety containing the longest alkyl chain (18 carbons) displayed the highest micro-roughness and, thus, the most hydrophobic surfaces. With regard to AF and FR properties, coatings based on the 18 carbon QAS moieties were very effective at inhibiting C. lytica biofilm formation and enabling easy removal of Ulva sporelings (young plants) while coatings based on the 14 carbon QAS moities were very effective at inhibiting biofilm growth of N. incerta.

Hydrosilylation of alkynes catalyzed by platinum on carbon

Hydrosilylation of terminal and internal alkynes with chlorosilanes, alkylsilanes, and alkoxysilanes catalyzed by platinum on carbon are discussed. The yields of the isolated vinylsilanes are high and the selectivity of the product depends on the silane used. Hydrosilylation of alkynes with chlorosilanes produced the β-trans vinylsilanes, while alkyl and alkoxysilanes produced two or three vinylsilane isomers. The selectivity of the catalyst platinum on carbon is similar to Karstedts catalyst in the reaction of phenylacetylene with triethylsilane or triethoxysilane. High resolution electron microscopy showed colloidal platinum to be present in these reactions.

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.

Palladium-catalyzed and sonically accelerated hydrogenations of olefins using formic acid as a hydrogen transfer agent

The formic acid/palladium-on-carbon couple was found to be an effective hydrogenating system. Ten olefins, including terminal and internal alkenes, a diene, a vinyl ether, and an α,β-unsaturated ketone, were hydrogenated in high yields at room temperature and atmospheric pressure. Sonication of the reaction mixtures accelerated the reactions as did heating to reflux. Cyclopropylbenzene and diphenylacetylene were reduced quantitatively to n-propylbenzene and bibenzyl, respectively.

Organic sonochemistry. Ultrasound promoted coupling of chlorosilanes in the presence of lithium wire

Abstract Triorganometal chlorides, R 3 MCl (R = alkyl, aryl, M = Si, Sn) are readily coupled to form bimetallics in 42–95% yields using Li wire and ultrasound. Dihalosilanes give good yields of cyclic polysilanes.

Organic sonochemistry. Ultrasound-promoted coupling of organic halides in the presence of lithium wire

Abstract Alkyl, aromatic, benzylic and benzoyl halides have been successfully coupled in good yields using lithium wire suspended in tetrahydrofuran and ultrasound.

Organic Sonochemistry, ultrasonic acceleration of the reduction of simple and deactivated aryl halides using lithium aluminum hydride

Abstract Eleven aromatic halides are reduced in very high yields in the presence of LiAlH4 and sonic waves at 35°.

Flattening a puckered cyclohexasilane ring by suppression of the pseudo-Jahn–Teller effect

We report the experimental and theoretical characterization of neutral Si(6)X(12) (X = Cl, Br) molecules that contain D(3d) distorted six-member silicon rings due to a pseudo-Jahn-Teller (PJT) effect. Calculations show that filling the intervenient molecular orbitals with electron pairs of adduct suppresses the PJT effect in Si(6)X(12), with the Si(6) ring becoming planar (D(6h)) upon complex formation. The stabilizing role of electrostatic and covalent interactions between positively charged silicon atoms and chlorine atoms of the subject [Si(6)Cl(14)](2-) dianionic complexes is discussed. The reaction of Si(6)Cl(12) with a Lewis base (e.g., Cl(-)) to give planar [Si(6)Cl(14)](2-) dianionic complexes presents an experimental proof that suppression of the PJT effect is an effective strategy in restoring high Si(6) ring symmetry. Additionally, the proposed pathway for the PJT suppression has been proved by the synthesis and characterization of novel compounds containing planar Si(6) ring, namely, [(n)Bu(4)N](2)[Si(6)Cl(12)I(2)], [(n)Bu(4)N](2)[Si(6)Br(14)], and [(n)Bu(4)N](2)[Si(6)Br(12)I(2)]. This work represents the first demonstration that PJT effect suppression is useful in the rational design of materials with novel properties.

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.

NEW NEUTRAL CARRIER-TYPE ION SENSORS. CROWN ETHER DERIVATIVES OF POLY(METHYLHYDROSILOXANE)

Abstract A facile one step synthesis of poly(methylalkoxy-crownether)siloxanes has been achieved by dehydrogenative alkoholysis of PMHS (polymethylhydrosiloxane) catalyzed by a Rh(I) complex.