Investigation of the Precipitation Behavior of Asphaltenes in the Presence of Naphthenic Acids Using Light Scattering and Molecular Modeling Techniques

A delay in the onset of flocculation is observed for asphaltenes in the presence of several naphthenic acids: methyl abietate, hydrogenated methyl abietate, 5β-cholanic acid, and 5β-cholanic acid-3-one. This flocculation behavior is monitored as a function of the added precipitant (n-heptane) to solutions of suspended asphaltenes and naphthenic acids in model solutions of toluene/n-heptane, using a combination of dynamic light scattering (DLS) and near-infrared (NIR) spectroscopic techniques. DLS and NIR show very good correlation in indentifying the onsets of flocculation, which varied among the series of naphthenic acids. Specific interaction energies and equilibrium intermolecular distances of asphaltenes and naphthenic acids are calculated using molecular mechanics. The results from molecular mechanics calculations support the experimental results of the titrations, and structure–property relationships are defined. Structure–property relationships are established for naphthenic acids, defining the relative contributions and importance of various functional groups: C═C, C═O, COOR, and COOH. The additive effects of naphthenic acids, defined by an increase in the precipitation onset, increase in the order of 5β-cholanic acid-3-one \u3c hydrogenated methyl abietate \u3c methyl abietate \u3c 5β-cholanic acid, with experiments containing 5β-cholanic acid-3-one containing unexpected and interesting results

Effect of Water and Solvent Selection on the SAFA Purification Times for Metallic Nitride Fullerenes

This paper addresses two key parameters in the SAFA purification method for isolating endohedral metallofullerenes. The percent water content in the reactive aminosilica significantly affects the time needed to isolate Sc3N@Ih-C80 metallic nitride fullerene (MNF). The role of solvent selection in the SAFA process is also discussed. The SAFA purification time needed for isolating Sc3N@Ih-C80 metallofullerene is influenced by the identity of the electron donating/accepting group on the aromatic solvent

Investigation of the Precipitation Behavior of Asphaltenes in the Presence of Naphthenic Acids Using Light Scattering and Molecular Modeling Techniques

A delay in the onset of flocculation is observed for asphaltenes in the presence of several naphthenic acids: methyl abietate, hydrogenated methyl abietate, 5β-cholanic acid, and 5β-cholanic acid-3-one. This flocculation behavior is monitored as a function of the added precipitant (<i>n</i>-heptane) to solutions of suspended asphaltenes and naphthenic acids in model solutions of toluene/<i>n</i>-heptane, using a combination of dynamic light scattering (DLS) and near-infrared (NIR) spectroscopic techniques. DLS and NIR show very good correlation in indentifying the onsets of flocculation, which varied among the series of naphthenic acids. Specific interaction energies and equilibrium intermolecular distances of asphaltenes and naphthenic acids are calculated using molecular mechanics. The results from molecular mechanics calculations support the experimental results of the titrations, and structure–property relationships are defined. Structure–property relationships are established for naphthenic acids, defining the relative contributions and importance of various functional groups: CC, CO, COOR, and COOH. The additive effects of naphthenic acids, defined by an increase in the precipitation onset, increase in the order of 5β-cholanic acid-3-one < hydrogenated methyl abietate < methyl abietate < 5β-cholanic acid, with experiments containing 5β-cholanic acid-3-one containing unexpected and interesting results

Singlet Oxygen Generation and Adhesive Loss in Stimuli-Responsive, Fullerene-polymer Blends, Containing Polystyrene-block-polybutadiene-block-polystyrene and Polystyrene-block-polyisoprene-block-polystyrene Rubber-Based Adhesives

The adhesive properties, as measured by bulk tack and peel strength analysis, were found to decrease in polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) and polystyrene‐block‐polyisoprene‐block‐polystyrene (SIS) PSA films containing common singlet oxygen generators, acridine, rose bengal, and C60 fullerene, when irradiated with a tungsten halogen light in air. The addition of the singlet oxygen quencher, β‐carotene, to the C60 fullerene samples was found to significantly deter the rate of adhesive loss in the fullerene‐SBS and ‐SIS PSA nanocomposites. The presence of oxygen was essential to the mechanism of adhesive loss and, in combination with the effects of singlet oxygen generators and a singlet oxygen scavenger, strongly supports a singlet‐oxygen mediated process. FTIR investigations of fullerene‐SBS and ‐SIS systems suggest the initial formation of peroxides which, upon further irradiation, lead to the generation of carbonyl‐containing compounds of a ketonic type after crosslinking. Rates of SBS and SIS C‐H abstraction were comparable and found to decrease when the high‐pressure, mercury xenon irradiation source was filtered to allow only light of λ \u3e 390 nm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 200

Dispersion of Gold Nanoparticles in UV-Cured, Thiol-Ene Films by Precomplexation of Gold-Thiol

Alkyl thiols and alkenes (enes) polymerize via an extremely rapid step-growth, free-radical chain process, uninhibited by air, to give high-density networks with excellent mechanical and physical properties. These thiol−ene coatings are potentially useful for a wide variety of coatings, adhesives, and optical applications. In this work, a series of nanogold-containing UV-cured, thiol−ene coatings were prepared from trimethylolpropane tris(3-mercaptopropionate) (trithiol) and pentaerythritol allyl ether (triene) monomers using a unique procedure which facilitates precomplexation of the gold−thiol prior to photocuring. Irgacure 651 (1 wt %) was used as a photoinitiator, and nanogold was incorporated at 0−1 wt %, average ∼10 nm size particles by TEM. Physical and mechanical properties were characterized using bulk tack analysis and other standard techniques: DSC, TGA, pencil hardness, and gel fractions. In general, films were found to be low absorbing in the visible range and highly uniform and to contain well-dispersed nanogold particles. Although the rate of polymerization was modestly retarded by the presence of gold nanoparticles, functional group conversions (C═C and S−H) and gel fractions were high. Increasing nanogold content resulted in an increase in Tg measured by DSC (−15 to −8 °C for 0−1 wt % nanogold, respectively) due to the increasing number of physical gold−thiol cross-links created. TGA analysis revealed a small negative impact of increasing nanogold composition on relative thermal stability. The 1 wt % nanogold-containing samples possessed appreciable electrostatic discharge (ESD) character, with ESD times of 1−10 s measured using a commercial charge plate analyzer

Evolution of the diatoms: insights from fossil, biological and molecular data

Molecular sequence analyses have yielded many important insights into diatom evolution, but there have been few attempts to relate these to the extensive fossil record of diatoms, probably because of unfamiliarity with the data available, which are scattered widely through the geological literature. We review the main features of molecular phylogenies and concentrate on the correspondence between these and the fossil record; we also review the evolution of major morphological, cytological and life cycle characteristics, and possible diatom origins. The first physical remains of diatoms are from the Jurassic, and well-preserved, diverse floras are available from the Lower Cretaceous. Though these are unequivocally identifiable as centric diatoms, none except a possible Stephanopyxis can be unequivocally linked to lineages of extant diatoms, although it is almost certain that members of the Coscinodiscophyceae (radial centrics) and Mediophyceae (polar centrics) were present; some display curious morphological features that hint at an unorthodox cell division mechanism and life cycle. It seems most likely that the earliest diatoms were marine, but recently discovered fossil deposits hint that episodes of terrestrial colonization may have occurred in the Mesozoic, though the main invasion of freshwaters appears to have been delayed until the Cenozoic. By the Upper Cretaceous, many lineages are present that can be convincingly related to extant diatom taxa. Pennate diatoms appear in the late Cretaceous and raphid diatoms in the Palaeocene, though molecular phylogenies imply that raphid diatoms did in fact evolve considerably earlier. Recent evidence shows that diatoms are substantially underclassified at the species level, with many semicryptic or cryptic species to be recognized; however, there is little prospect of being able to discriminate between such taxa in fossil material

Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc\u3csub\u3e3\u3c/sub\u3eN@C\u3csub\u3e80\u3c/sub\u3e(CF\u3csub\u3e3\u3c/sub\u3e)\u3csub\u3e\u3cem\u3en\u3c/em\u3e\u3c/sub\u3e (\u3cem\u3en\u3c/em\u3e=2â16) and Their Radical Anions

A family of highly stable (poly)perfluoroalky-lated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, 19F NMR, UV−vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc3N@C80(CF3)10 and Sc3N@C80(CF3)12, single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental (19F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc3N@C80(CF3)n (n = 2-16). Electrochemical studies revealed that Sc3N@C80(CF3)n derivatives are easier to reduce than Sc3N@C80, the shift of E1/2 potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc3N@C80(CF3)n were generated in solution and characterized by ESR spectroscopy, revealing their 45Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc3N@C80 making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance