Small-angle X-ray scattering of n-hexacontane as a function of temperature

Journal Article · Mon Apr 11 04:00:00 EDT 1994 · Macromolecules; (United States)

DOI:https://doi.org/10.1021/ma00086a054· OSTI ID:7198186

Mandelkern, L; Alamo, R G ^[1]; Sokolov, E L; Li, Y; Chu, B ^[2]

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1. Florida State Univ., Tallahassee, FL (United States)
2. State Univ. of New York at Stony Brook, NY (United States). Dept. of Chemistry

Although the n-alkanes have a rather simple chemical repeat, they exhibit a variety of different crystalline structures and phase transitions between them. This is true not only for the different alkanes but within a given alkane, depending on the crystallization mode. Premelting, even for very pure alkanes, further complicates structural analyses. The premelting of interest here involves the conformational disordering of the end sequences and has been demonstrated to occur in a large number of n-alkanes by a variety of experimental methods. Hexacontane, C[sub 60]H[sub 122], is a key alkane in studying the crystalline structures and the premelting phenomenon. It is a sufficiently long chain that does not display the hexagonal structure, or rotator phase. Thus, this complicating feature is removed from consideration. A variety of studies such as vibrational spectroscopy, small-angle X-ray scattering (SAXS), solid-state [sup 13]C NMR, and thermal expansion of this alkane can be interpreted in terms of premelting. However, different ordered structures can develop in n-hexacontane at ambient temperature, depending on the method of crystallization. Of additional interest is the origin of the small endothermic peak that is observed subsequent to crystallization from the pure melt. To correlate the results of different measurements and to examine the nature of this endothermic transition, the authors have studies the SAXS temperature dependence of n-hexacontane. The two samples investigated were crystallized under the exact same conditions as those previously studied by solid-state [sup 13]C NMR, differential scanning calorimetry (DSC), and thermal expansion.

• DOE Contract Number: FG02-86ER45237; FG05-89ER75515
• OSTI ID: 7198186
• Journal Information: Macromolecules; (United States), Journal Name: Macromolecules; (United States) Vol. 27:8; ISSN MAMOBX; ISSN 0024-9297
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ALKANES
CRYSTAL STRUCTURE
DATA
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
MELTING
NUMERICAL DATA
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
TEMPERATURE DEPENDENCE
THERMAL ANALYSIS