Semifluorinated alkanes and alkanes: A phase study of the perfluorohexyloctane - Tetradecane system

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

  • Anna Runnsjo
  • Vitaly Kocherbitov
  • Gesche Graf
  • Anthony Pettigrew
  • Dieter Scherer
  • Mortensen, Kell
  • Johan Engblom
The binary system perfluorohexyloctane (F6H8)–tetradecane (C14) was investigated in order to increase understanding of interactions of semifluorinated alkanes (SFAs) with hydrophobic molecules. The thermal
phase behavior for F6H8 and C14 and their mixtures was determined using DSC. The activity coefficients for both components in the mixtures were calculated and Gibbs energy of mixing was determined. Furthermore, enthalpies of mixing were determined with ITC and structural investigations of the solid and the liquid phases were performed with SAXS and SWAXD. It was found that F6H8 displays one solid-solid transition at 42.3 C (DH = 1.1 kJ/mol) and one solid-liquid transition at 5.9 C (DH = 16.6 kJ/mol). Due to the low enthalpy of the solid-liquid transition it is likely that F6H8 is not fully crystallized in the solid phase but partly amorphous. The F6H8–C14 system displays a eutectic phase
behavior and the liquid mixtures display a positive deviation from ideal mixing. C14 crystalizes in a triclinic unit cell as shown before, whereas crystallization of F6H8 in a lamellar rippled phase is shown for the first time. This ripple phase comprises a bilayer of tilted alternating heavily interdigitated F6H8 molecules
in an oblique subunit cell.
OriginalsprogEngelsk
TidsskriftJournal of Chemical Thermodynamics
Vol/bind105
Sider (fra-til)352-361
ISSN0021-9614
DOI
StatusUdgivet - feb. 2017

ID: 187623278