The 1-octanol/water (In P-o/w) and perfluoro(methylcyclohexane)/toluene (In P-PFMC/Tol) partition coefficients were measured for four fluorinated rhodamine-based fluorescence dyes (F-rhodamines) functionalized with F-ponytails of various lengths CnH2n-CmF2m+1 (n = 1,2 and m = 3,7,8,10) at both amine groups. Here, the In P-o/w accounts usually for the lipophilic-hydrophilic ratio in ageous (biological) media whereas the In P-PFMC/Tol is a standard value for the description of the fluorophilic-lipophilic ratio. Both partition coefficients correlated with the CmF2m+1/CnH2n ratio, but not directly with the length of the F-ponytails. The ability of the F-rhodamines to incorporate into the hydrophobic part of the bilayer of giant unilamellar vesicles (GUVs) of 1,2-dioleoyl-sn-glycero-3-phosphbcholine (DOPC) mixed with 1H,1H,2H,2H-perfluoro-1-octanol (F6H2OH) using confocal laser scanning microscopy was tested and the partitioning of the F-rhodamines into the mixed GUVs could not be explained exclusively using the two In P values mentioned above. Two other partition coefficients between F6H2OH/W (In P-F6H2OH/W) and perfluoro-n-octane/n-octane (In PF-oct/oct) were measured. The In PF-oct/oct correlated in a comparable way with the In P-PFMC/Tol, whereas In P-F6H2OH/W accounting for the fluorophilic-hydrophilic ratio correlated with the length of the F-ponytails and additionally clarified the different staining abilities of the synthesized F-rhodamines in the mixed GUVs. (C) 2016 Elsevier B.V. All rights reserved.