¹⁹F NMR investigation of mixed surfactants partitioning and kinetic stability of fluorinated nanodroplets in water

Oil-in-water fluorinated microemulsion aggregates were diluted at high water content, thus taking the system outside the regime of thermodynamic stability. The kinetic stability of aggregates was studied by an analysis of ¹⁹F NMR chemical shifts. The microemulsions were formed from mixtures of three homologous perfluoropolyether (PFPE) sodium carboxylates of high purity. They had a Cl-terminated perfluoroalkyl group and differed in the number of perfluoro-isopropoxy units in the chain. Two PFPE oils having different chain lengths and n-perfluorooctane were used to obtain the o/w fluoro-nanodroplets. The partitioning of the individual surfactants between aqueous phase and mixed fluoro-nanodroplets as a function of total surfactant concentration was determined.