Dispersion and Stabilizing Effects of n-Hexadecane on Tetralin and Benzene Metastable Droplets in Surfactant-Free Conditions

The size distribution of metastable oil droplets in water was investigated by the dynamic light-scattering method for tetralin (1,2,3,4-tetrahydronaphthalene), benzene, n-hexadecane, and their mixtures under surfactant-free conditions. For pure tetralin, droplets appeared with multiple peak distributions, first at sizes around 5 × 102 to 2 × 103 nm, and shortly coalesced to grow discretely to 3 μm within 30 min. On the contrary, for pure n-hexadecane, droplets appeared with a single location at 40−120 nm and their sizes remained unchanged for several hours. The addition of a small amount of n-hexadecane, even at 1:1000 and 1:100 molar ratios, to tetralin significantly improved the dispersion and stability of tetralin droplets. Peculiarly, the interfacial tension of the mixed oils with water was raised with the n-hexadecane concentration. The dispersed solutions of benzene could be further stabilized (for as long as 1 month) with the addition of hexadecane. Expulsion of n-hexadecane onto the droplet surfaces and the related surface modification seem to be responsible for the stabilization effects.