Semifluorinated alkanes (SFA) is a class of molecules which display several unique properties and have been proposed for use in numerous biological applications [1-3]. In this study we have investigated the interaction of perfluorohexyloctane (F6H8) with tetradecane (C14) and water.
F6H8/C14 mixtures were found to display eutectic phase behavior with an eutectic point of -8.5 °C at 6 wt% C14. F6H8 displays two transitions at -42°C (DH=1.0 kJ/mol) and -6°C (DH=16.4 kJ/mol). Due to the low enthalpy value of the first transition in F6H8 it is likely that this corresponds to a transition in solid F6H8 rather than solid-liquid transition. Similar, the main transition point indicates that F6H8 is not fully crystallized in the solid phase but rather partly amorphous. The data indicates that most probably the fluorinated part is crystal while the hydrogenated segment is in amorphous state. Pure C14 has one solid-liquid transition point at 5.9 °C (DH=48.0 kJ/mol). Titration of small amount C14 into infinite volume of F6H8 reveals an enthalpy of solution at infinite dilution of 4 kJ/mol C14.
Further, the low water solubility determined for F6H8 and F6H8-C14 mixtures promotes the ability to form an effective occlusive layer. We have shown that a film of F6H8 or F6H8-C14 mixtures significantly reduces water evaporation from a hydrogel.
References
1. Krafft MP, Riess JG. Chem Rev (2009) 109:1741-1792.
2. Tsagogiorgasa C, Jungb T, Krebsa J, Theisingerd B, Becke G, Yard BA, Quintel M. Int J Pharm (2012) 422:194-201.
3. EP 2 335 735 A1, Gunther B, Theisnger S and Theisinger B. Pharmaceutical composition for treatment of dry eye syndrome. Filed 14.12.2009.
anna.runnsjo@mah.se
