TY - JOUR

T1 - Semifluorinated alkanes and alkanes

T2 - A phase study of the perfluorohexyloctane - Tetradecane system

AU - Runnsjo, Anna

AU - Kocherbitov, Vitaly

AU - Graf, Gesche

AU - Pettigrew, Anthony

AU - Scherer, Dieter

AU - Mortensen, Kell

AU - Engblom, Johan

PY - 2017/2

Y1 - 2017/2

N2 - The binary system perfluorohexyloctane (F6H8)–tetradecane (C14) was investigated in order to increase understanding of interactions of semifluorinated alkanes (SFAs) with hydrophobic molecules. The thermalphase 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 phasebehavior 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 moleculesin an oblique subunit cell.

AB - The binary system perfluorohexyloctane (F6H8)–tetradecane (C14) was investigated in order to increase understanding of interactions of semifluorinated alkanes (SFAs) with hydrophobic molecules. The thermalphase 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 phasebehavior 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 moleculesin an oblique subunit cell.

KW - Semifluorinated alkane

KW - Perfluorohexyloctane

KW - Tetradecane

KW - Thermal phase behavior

KW - Calorimetry

KW - Small angle X-ray scattering

U2 - 10.1016/j.jct.2016.10.032

DO - 10.1016/j.jct.2016.10.032

M3 - Journal article

VL - 105

SP - 352

EP - 361

JO - Journal of Chemical Thermodynamics

JF - Journal of Chemical Thermodynamics

SN - 0021-9614

ER -