1997 Volume 46 Issue 8 Pages 857-866,936
The coalescence of hexadecane emulsions prepared with dimyristoylphosphatidylcholine (DMPC) was investigated. Hexadecane was emulsified with DMPC dispersion aged overnight at 25 and 35°C. The time dependence of emulsion particle size was measured at 25, 29 and 35°C. Assuming coalescence to follow the rate equations of first and second order reactions and the Arrhenius relation, the rate constants (k) and the activation energy (E*) for the coalescence were determined. The values of k35 for the emulsion prepared at 35°C were several times larger than those of k25 for the emulsion prepared at 25°C, and the value of E*35 for the emulsion prepared at 35°C was about half the value of E*25 for the emulsion prepared at 25°C. These differences in kinetic parameters for the emulsion coalescence were explained in terms of the difference in the adsorbed states of DMPC at the surfaces of the emulsion particles made originally at 25 and 35°C.
