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11.
Schmidt DL Brady RF Lam K Schmidt DC Chaudhury MK 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2830-2836
Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance. 相似文献
12.
Assembly of a supramolecular cube, [(Cp*WS3Cu3)8 Cl8(CN)12Li4] from a preformed incomplete cubane-like compound [PPh4][Cp*WS3(CuCN)3 总被引:2,自引:0,他引:2
Lang JP Xu QF Chen ZN Abrahams BF 《Journal of the American Chemical Society》2003,125(42):12682-12683
A supramolecular cube has been formed by linking WS3Cu3 clusters with bidentate ligands. Eight WS3Cu3 clusters, which have an incomplete cubane-like structure, serve as the three connecting nodes of the cube, while 12 bridging cyanide anions coordinated to copper centers lie along the edges of the cube. Eight chloride anions and four lithium cations are located inside the cube. 相似文献
13.
14.
Allison M. Sikes Robert F. Brady 《Journal of polymer science. Part A, Polymer chemistry》1990,28(9):2533-2546
The diglycidyl ether of bisphenol A (DGEBA) was cured with either an aliphatic or an aromatic spirobislactone using a tertiary amine catalyst. The products were characterized by FTIR, TGA, DSC, dilatometry, and single-fiber adhesion measurements, and their performance was compared to that of DGEBA cured with acid anhydrides. Both aliphatic and aromatic bislactones are effective curing agents for DGEBA. FTIR and dilatometry confirm that both lactone rings open early in the curing reaction and initially offset shrinkage caused by polymerization. After the bislactone has been consumed, oxirane reactions proceed in a normal fashion. The final shrinkage of cured DGEBA polymers, with or without addition of bislactones, is 3.0–3.5%. Bislactone-modified materials possess superior thermal properties, when compared to those of anhydride-cured materials. 相似文献
15.
Atmospheric pressure chemical ionisation liquid chromatography/mass spectrometry (APCI-LC/MS) has been used for identification of the epimers of hydroxy, methoxy and methoxylactone allomers of chlorophyll a (13(2)-HO-chl a, 13(2)-MeO-chl a and 15(1)-MeO-lact-chl a), the hydroxy allomer of bacteriochlorophyll a (13(2)-HO-bchl a) and the hydroxy and methoxylactone allomers of bacterioviridin a (13(2)-HO-bvir a and 15(1)-MeO-lact-bvir a). The APCI mass spectra show that facile fragmentations involve the methoxyl or hydroxyl groups at the C-13(2) or C-15(1) chiral centres. Losses involving the C-13(2) or C-15(1) hydroxyl or methoxyl groups occur more easily from the S-epimer than from the R-epimer due to the greater relief of the steric strain associated with interaction with the bulky C-17 substituent. The differences in mass spectrometric fragmentation can be used as a diagnostic tool for the assignment of the stereochemical configuration at the C-13(2) or C-15(1) chiral centres. 相似文献
16.
High-resolution neutron and synchrotron X-ray powder diffraction studies are reported for the six oxides AB2O4 (A=Ca2+, Sr2+ and Ba2+ and B=Al3+ and Ga3+). These oxides all adopt a stuffed tridymite type structure, the precise nature of which depends on both the A- and B-type cations. Bond valence calculations reveal a range of values for the various A-type cations, in all cases at least one site is significantly underbonded. Conversely the tetrahedral B-type sites invariably exhibit unexceptional bond valencies. Attempts to dope the oxides with various lanthanides to the 1% level invariably resulted in some segregation into alternate phases located at the grain boundaries. The identity of the impurity phases is presented and the importance of bond valencies in understanding this segregation is highlighted. 相似文献
17.
Syntheses of quaternary 1-alkyl-3-perfluoroalkyl-4,5-dimethyl-1,2,4-triazolium iodides have led to a variety of new quaternary salts via metathesis reactions. 1,4,5-Trimethyl-3-trifluoro-methyl-1,2,4-triazolium iodide (6) with LiN(SO(2)CF(3))(2), KSO(3)CF(3), AgClO(4), AgBF(4); 1-(3-fluoropropyl)-3-trifluoromethyl-4,5-dimethyl-1,2,4-triazolium iodide (7) with LiN(SO(2)CF(3))(2); and 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium iodide (8) with LiN(SO(2)CF(3))(2), AgClO(4), AgBF(4) gave excellent yields of new thermally stable and relatively low melting quaternary salts. The structure of 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium tetrafluoroborate (11c) was confirmed by single-crystal X-ray analysis. Although the molecular weight of 11c (cation) is 3-fold greater than that of the 3-trifluoromethyl derivative 9d, its melting point is 32 degrees C lower. 相似文献
18.
Eduardo Prez-Cordero Rosanna Buigas Nancy Brady Luis Echegoyen Claudia Arana Jean-Marie Lehn 《Helvetica chimica acta》1994,77(5):1222-1228
Reductive electrocrystallization at a constant current density (11.0–11.5 μA/cm2) of millimolar solutions of [M(bpy)3](PF6)2, where M = Fe, Ru, or Os, and bpy = 2,2′-bipyridine in acetonitrile containing 0.1M Bu4NPF6 results in the formation of dark crystals on the Pt cathode. The crystals grow as long, thin, and shiny needles having a hexagonal cross section of 0.1–0.5 mm in diameter. Combustion microanalyses results are consistent with the composition for [Fe(bpy)3], [Ru(bpy)3], and [Os(bpy)3]. In addition, the chromophores are conserved, as confirmed by recording both the electronic and the 1H-NMR spectra after reoxidation of the electrocrystals in humid air. The spectra are identical to those for authentic samples of [Fe(bpy)3]2+, [Ru(bpy)3]2+, and [Os(bpy)3]2+. A ratio of 2.0 ± 0.1 e?/molecule is observed upon completion of the controlled potential electrolysis of a solution of [M(bpy)3]2+, which results in the precipitation of a dark solid and the almost complete fading of the color of the original solution. Unexpectedly, the crystals do not exhibit an ESR signal. These data indicate the formation of novel materials, crystalline [Fe(bpy)3], [Ru(bpy)3], and [Os(bpy)3]. 相似文献
19.
20.
Although very bulky ligands e.g.(o-MeC6H4)3E or (μ-C10H7)3E (E = P or As) are inert, the normal photochemical or thermal reaction of tertiary phosphines or arsines, L, with [Mn2(CO)10] is CO substitution with the formation of [Mn2(CO)8(L)2] derivatives (I). At elevated temperatures some triarylarsines, R3As, undergo Lambert's reaction with ligand fragmentation to give [Mn2(CO)8(μ-AsR2)2] complexes (II) (R = Ph, p-MeOC6H4, p-FC6H4, or p-CIC6H4) even though, in the absence of [Mn2(CO)10] R3As are stable under the same conditions. Exceptional behaviour is exhibited by (p-Me2NC6H4)3- As which forms a product of type I; by some HN(C6H4)2AsR which give a product of type II as a result of loss of the non-aryl groups R = PhCH2, cyclo-C6H11, or MeO; and by Ph(α-C10H72P which is the only phosphine to form a product of type II, albeit in trace amounts only. The thermal decomposition of a n-butanol solution of [Mn2(CO)8(AsPh3)2] in a sealed tube gives C6H6 and [Mn2(CO)8(α-AsPh2)2], whilst in an open system in the presence of various tertiary phosphines, L, [Mn(H)(CO)3(L)2] are obtained. It is suggested that Lambert's reaction is a thermal fragmentation of [Mn(CO)4(AsR3]* radicals, the first to be recognised. They lose the radical R* which abstracts hydrogen from the solvent. The resulting [Mn(CO)4(AsR2)] moiety dimerises to [Mn2(CO)8-(α-AsR2)2]. the reaction is facilitated by the stability of the departing radical (e.g. PhCH2 or MeO) and, as the crowding about As is relieved, by its size (e.g. Ph, cyclo-C6H11, o-MeC6H4, or α-C10H7). In general, phosphine-substituted radicals [Mn(CO)4(PR)3]* do not undergo this decomposition, probably because the PC bonds are much stronger than AsC. 相似文献