Dispersion and stabilizing effects of n-hexadecane on tetralin and benzenemetastable 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-tetrahydronaph thalene), benzene, n-hexadecane, and their mixtures under surfactant-free c onditions. For pure tetralin, droplets appeared with multiple peak distribu tions, first at sizes around 5 x 10(2) to 2 x 10(3) nm, and shortly coalesc ed to grow discretely to 3 mu m within 30 min. On the contrary, for pure n- hexadecane, droplets appeared with a single location at 40- 120 nm and thei r sizes remained unchanged for several hours. The addition of a small amoun t of n-hexadecane, even at 1:1000 and 1:100 molar ratios, to tetralin signi ficantly improved the dispersion and stability of tetralin droplets. Peculi arly, 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 hexadecan e. Expulsion of n-hexadecane onto the droplet surfaces and the related surf ace modification seem to be responsible for the stabilization effects.