Epitaxy and structure of paraffin-diluent eutectics

Dorset, Douglas L.; Hanlon, J. E.; Karet, Gail B.

doi:10.1021/ma00195a029

Cited by 38 publications

(33 citation statements)

References 9 publications

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“…Typical of petroleum waxes, it would have a Gaussian distribution of chain components (Tegelaar, Matthezing, Jansen, Horsfield & de Leeuw, 1989 (Downing, Kranz, Lamberton, Murray & Redcliffe, 1961;Stransky & Streibl, 1971;Stransky, Streibl & Kubelka, 1971; Tulloch, 1970 Tulloch, , 1971 Tulloch, , 1972 and a mass spectral analysis of component chain lengths (Tulloch, 1972) was used to guide the construction of the beeswax model listed in Table 1. For electron diffraction analyses, typical crystals with long chains normal to the major crystal face were grown by evaporation from dilute light petroleum solution. The more useful orthogonal projection onto the chain axes was achieved by epitaxial orientation on benzoic acid to form microcrystals so that the chain axes are nucleated to lie parallel to the major (100) crystal face (Wittmann, Hodge & Lotz, 1983;Dorset, Hanlon & Karet, 1989). indistinguishable in this projection.]…”

Section: Methodsmentioning

confidence: 99%

The crystal structure of waxes

Dorset¹

1995

Acta Crystallogr Sect B

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Quantitative electron crystallographic studies have been carried out on epitaxially oriented multi-component waxes. Intensities from two paraffin-based samples, an artificial six-component medium wax (equimolar distribution of chain lengths) and a petroleum-based wax (Gaussian distribution of chain lengths) have been used to determine their crystal structures. As found earlier for binary paraffin solid solutions, differences in molecular volume are compensated by longitudinal molecular shifts within individual lamellae. Nevertheless, each lamellar surface must remain fiat enough, and with enough crystallographic order intact, to nucleate the next lamella, thus accounting for the observed long-range correlation in these crystals. Recrystallized beeswax also has a layer packing somewhat similar to the paraffin waxes. However, in this case, the lamellar order is 'frustrated' so that a certain amount of 'nematically' ordered material must be present, spanning the nascent lamellar interfaces. IntroductionPolydisperse combinations of linear molecules are often found in biologically and commercially significant materials, ranging from the lipids to synthetic polymers. Multicomponent paraffin solid solutions, themselves, have been significant for the study of petroleum wax crystallization, as a model for insect and plant cuticle waxes and as a model for polydisperse polyethylene lamellae.Crystallographically, the description of such polydisperse linear-chain combinations is not well advanced. Progress has been made recently in the study of binary n-paraffin solids in the form of single crystals. Low-angle X-ray diffraction measurements had often been made on such samples (Mnyukh, 1960;Fischer, 1971;Asbach, Geiger & Wilke, 1979;Craievich, Doucet & Denicolo, 1984) and, more recently, on polydisperse solids (Asbach & Kilian, 1991;Basson & Reynhardt, 1992). However, the first single-crystal characterization of an n-paraffin binary solid solution was reported only two decades ago (L0th, Nyburg, Robinson & Scott, 1974). In this qualitative description, it was proposed that the copacking of dissimilar chain lengths was compensated by longitudinal molecular disorder in individual lamellae. ©1995 International Union of Crystallography Printed in Great Britain -all rights reserved Vibrational spectroscopic (Maroncelli, Strauss & Snyder, 1985; Kim, Strauss & Snyder, 1989) as well as NMR measurements (Basson & Reynhardt, 1991) established that conformational disorder near the chain ends was also important for minimizing the average nonoverlapping volume. Recent quantitative crystal-structure analyses of such solid solutions, based on electron (Dorset, 1990a) or X-ray diffraction (Gerson & Nyburg, 1994) intensities, support the longitudinal disorder model.In an earlier electron diffraction study of binary paraffin combinations (Dorset, 1987), it was found that similar patterns could also be obtained from an oriented commercial petroleum wax. In this paper, the study of paraffin-based multicomponent waxes is extended to f...

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Section: Methodsmentioning

confidence: 99%

The crystal structure of waxes

Dorset¹

1995

Acta Crystallogr Sect B

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“…As described in an earlier paper (2), electron diffraction patterns (Fig. 1 Upper) were recorded on Kodak DEF-5 x-ray film from microcrystals of n-C32H66/n-C36H74 that had been epitaxially nucleated on benzoic acid following the procedure of Wittman et al (14), within the concentration limits of the quasi-binary phase diagram of the paraffin mixture with the carboxylic acid (15). The molar ratio of the two components is near 1:1 and will be identified as such in this paper, although XC36 = 0.47.…”

Section: Methodsmentioning

confidence: 99%

Direct structure analysis of a paraffin solid solution.

Dorset

1990

Proc. Natl. Acad. Sci. U.S.A.

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“…The second half of the mica sheet covered these components to form a sandwich, which was then placed at the hot end of a thermal gradient (metal bar spanning a hot plate and a thermoelectric cold plate), first to comelt the organic components and then to crystallize the hypo-eutectic solid. 15 The linear chains are also specifically oriented on the benzoic acid crystal surface. After cleaving the sandwich, the excess benzoic acid was removed by sublimation overnight in vacuo.…”

Section: Methodsmentioning

confidence: 99%

“…After calibrating the temperature scale with 18 known n-paraffins and n-perdeuterioparaffin standards, these transition points were used to construct binary phase diagrams, as described earlier. 15 (These diagrams, however, may not describe fully equilibrated binary systems.) Electron Diffraction and Microscopy.…”

Section: Methodsmentioning

confidence: 99%

Internal Heteroatom Substitution and the Layer Packing of Polymethylene Chains

Dorset¹,

and²,

Snyder³

1999

J. Phys. Chem. B

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In an investigation of methylene replacement by small heteroatom insertions the crystal structures of N,Ndioctadecylamine, (C 18 H 37 ) 2 NH, and dihexadecyl ether, (C 16 H 33 ) 2 O, were determined by electron crystallography and infrared spectroscopy. Crystals of the amine, epitaxially oriented on naphthalene, are characteristic of the analogous odd-chain n-paraffin in its high-energy orthorhombic B-polymorph. Cell constants are a ) 7.52-(2), b ) 5.04(1), and c/2 ) 50.0(4) Å and the extinction rules for the 0,k,l reflections (k + l ) 2n + 1) are consistent with the space group A2 1 am. Carbon and nitrogen coordinates in a paraffin-like model match observed data reasonably well (R ) 0.22). A binary phase diagram reveals that the secondary amine is continuously cosoluble with the n-paraffin of the same chain length (n-C 37 H 76 ). The ether, crystallized on benzoic acid, is polymorphic. The major monoclinic form, which forms a eutectic solid with n-C 33 H 68 , crystallizes in space group Aa with a ≈ 5.59, b ≈ 7.40, and c ) 88.66 Å and ) 116.2°. Its projected crystal structure includes a twisted chain conformation in an oblique layer (R ) 0.26). The orthorhombic form in space group A2 1 am (c/2 ) 45.1 Å) resembles the odd-chain paraffin and may be continuously co-soluble with it.

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Epitaxy and structure of paraffin-diluent eutectics

Cited by 38 publications

References 9 publications

The crystal structure of waxes

The crystal structure of waxes

Direct structure analysis of a paraffin solid solution.

Internal Heteroatom Substitution and the Layer Packing of Polymethylene Chains

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