Ann E. Mera

Novel non-toxic coatings designed to resist marine fouling

Abstract Coatings designed for applications as non-toxic non-fouling coatings have been prepared. Conventional coatings used in this application suffer from lack of adhesion to the substrate and lack of mechanical strength. Both of these detriments were overcome in this work by using a two-coat system: a basecoat which provides adhesion to the substrate, mechanical strength, and reactivity with the topcoat, and a topcoat which provides a non-toxic antiadhesive surface to discourage attachment of marine organisms. Five examples of such two-coat systems are described, in which the basecoat is a polybutadiene or urethane, and the topcoat is a silicone or hydrocarbon.

Hydrosilation in Supercritical CO2: Synthesis of Fluorinated Polysiloxanes

Hydrosilation of poly(methylhydrosiloxane) with a fluorinated olefin in supercritical CO2 (scCO 2 ) using Karstedts Pt catalyst has been successfully demonstrated; results were compared with those obtained in a subcritical conventional solvent, i.e. toluene. Rates of hydrosilation were found to be dependent on solvent, reactant concentration, and reaction temperature. Levels of hydrosilation were 40-50%, depending on reaction conditions. Gel formation, which was not observed under any conditions in subcritical toluene, occurred in all reactions done in scCO 2 and accounted for up to 20 wt.-% of the final product mix.

Development of a model system to study fuel autoxidation in supercritical media : Decomposition kinetics of 2,2'-azobis(isobutyronitrile) in supercritical carbon dioxide

Abstract A high pressure reactor has been constructed and used for in situ spectroscopic measurements of reaction kinetics in supercritical fluids. The thermal decomposition of 2,2′-azobis(isobutyronitrile) (AIBN) in supercritical carbon dioxide (SC-CO2) was studied as part of an effort to characterize free-radical autoxidation of hydrocarbon fuels under supercritical conditions. The findings show that AIBN decomposes both thermally and photochemically in SC-CO2 to form the 2-cyano-2-propyl free radical which dimerizes to form tetramethylsuccinic dinitrile and dimethyl-N-(2-cyano-2-propyl) ketenimine. Examination of the decomposition kinetics of the ketenimine revealed that it was photochemically stable in the kinetic reactor, but decomposed thermally to form the dinitrile.

Melt condensation and solution polymerization of highly fluorinated aliphatic polyesters

Abstract Highly fluorinated aliphatic polyesters were synthesized from a fluorodiol [HOCH2CH2(CF2)8CH2CH2OH] and both sebacoyl chloride and adipoyl chloride. Melt condensation polymerization followed by fractionation resulted in polymer samples with number average molecular weights in excess of 10 000. The use of solution polymerization yielded inferior results - with sebacoyl chloride the resultant polymers were of lower molecular weight, and with adipoyl chloride no polymer was formed. The fluoropolyesters have been characterized by 1H NMR and FT-IR spectroscopies, solubility, water contact angle, DSC and TGA. Crosslinking via peroxide of the polyester derived from sebacoyl chloride was successful; however, the resultant elastomeric-type material possessed residual crystallinity (from the parent polymer) and a low melting point.

Synthesis of Reactive Fluoroaliphatic Diamines

Abstract The synthesis of “reactive” ( i.e. aminoacylated) fluoroaliphatic diamines [H2N(CH2)3C(O)NHCH2CH2(CF2)nCH2CH2NHC(O)(CH2)3NH2; n=4,8] has been accomplished through the use of peptide blocking group and coupling techniques. Also, the synthetic route to these diamines and their dihydrobromide salts has been improved over that of a recently published procedure.

Analysis of volatiles evolved during high-temperature treatment of thermally stable polymers. II. Polybutadiyne

Polybutadiyne samples were heated at 20°C/min up to 1200°C in a pyroprobe attached to a gas chromatograph/mass spectrometer (GC/MS). Analysis of the volatiles evolved during heating identified carbon dioxide (adsorbed on polymer surface), methane, ethylene, benzene, toluene, and traces of higher aromatics. Correlations have been made between sample temperature and evolution (onset, maximum, and end temperatures) of each of the five listed volatiles. Average polybutadiyne weight loss at 1200°C was 14 ± 2%. Two cure studies were performed in the pyroprobe, and it was shown that both weight loss and volatile evolution were affected. The results were consistent with a higher degree of polymer cross-linking as cure time and temperature increased.

Cure studies and thermal stability of an acetylene-functionalized polyphenylene resin

SummarySamples of an acetylene-functionalized polyphenylene resin have been thermally cured to determine the effects on char yield and thermooxidative stability. The materials lack of a processing window led to difficulties in handling; it was found that quickly heating small samples above the melting point resulted in complete polymer melting prior to resolidification due to cure. Curing in air and in an inert atmosphere led to decreases and increases in char yields, respectively, at 900°C. Char yields in excess of 90 weight % were obtained at 900°C. The thermooxidative stability of the cured polymer was slightly better than that of the uncured resin, with the biggest improvement being in the 200–400°C range.

Polymerization of reactive fluoroaliphatic diamines with sebacoyl chloride to give fluorinated aliphatic polyamides (Nylons)

Abstract Both aminoacylated fluoroaliphatic diamines (‘reactive’ diamines) [H2N(CH2)3- C(O)NHCH2CH2(CF2)nCH2CH2NHC(O)(CH2)3NH2; n=4,8] and their tetrahydrobromide salts have been polymerized interfacially with sebacoyl chloride to give fluoroaliphatic polyamides. The polymers have been characterized by solution viscometry, DSC, TGA, water contact angle measurements, equilibrium water absorption and solubility, and compared to Nylon 6,10. The effects of using free diamine versus diamine salt as the monomer and of amount of fluorine in the monomer on polymer molecular weight are discussed. Also, the synthesis of the tetrahydrobromide salts is included since previous preliminary reports had identified the products as dihydrobromide salts.