On Perpendicular and Tilted Chains in Lamellar Crystals
| Autor: | Xiangbing Zeng, D.S.M. de Silva, Goran Ungar, Stephen J. Spells |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
education.field_of_study
Materials science Polymers and Plastics Scattering Small-angle X-ray scattering Population Infrared spectroscopy General Chemistry Condensed Matter Physics Condensed Matter::Soft Condensed Matter Crystallography Condensed Matter::Superconductivity Materials Chemistry Perpendicular Melting point Lamellar structure education Supercooling |
| Zdroj: | Journal of Macromolecular Science, Part B. 42:915-927 |
| ISSN: | 1525-609X 0022-2348 |
| DOI: | 10.1081/mb-120021615 |
| Popis: | Chain tilt and surface disorder were investigated in end-deuterated long n-alkane C12D25C192H384C12HD24 crystallized from solution and in n-alkane C162H326 crystallized from melt. Small-angle X-ray scattering and infrared spectroscopy were employed. Extended-chain crystals of C12D25C192H384C12HD24 as-grown from solution have the molecular axis perpendicular to the lamellar surface, but when heated, around 90°C, they start tilting relative to the layer normal. The tilt increases gradually to reach 35° just below the melting point. C162H326 crystallized from the melt at small supercoolings has chains tilted at 35° at the outset, as found previously for all melt-crystallized long alkanes and polyethylene. However, for the first time in long alkanes, it is found that when molten C162H326 is supercooled to ΔT≥10 K, crystals with perpendicular chains form. At still larger ΔT, the chains are once-folded, with a mixed population of tilted and perpendicular chain crystals. The use of Davydov splitting of the CH2 a... |
| Databáze: | OpenAIRE |
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