EFFECTS OF TEMPERATURE AND ALKYL CHAIN-LENGTH ON THE ASSOCIATIONS OF N-FATTY ACIDS IN 1,2-DICHLOROETHANE

The association of saturated fatty acid (FA) with carbon number (n) of 12-18 has been investigated in 1,2-dichloroethane by measuring the fl uorescence spectrum and intensity of ammonium 8-anilino-1-naphthalenes ulfonate as a fluorescent probe at 25, 40, 50 and 60-degrees-C, and th e effects of n and temperature on the association of FA were also stud ied. A simple phase diagram of octadecanoic acid in 1,2-dichloroethane was constructed. The critical concentration at which the dimers or th e trimers of FA began to appear, C1, was approximately the same for al l cases; C1 did not depend on n or temperature. On the contrary, the c ritical concentration at which the reversed micelles of FA were formed , C2, decreased regularly as n increased. The relationship between log C2 vs. n thus indicated a linearity.