Temperature effect on stearic acid monolayers on water

Abstract

Measurements are described for the force-area curve of stearic acid on pure water at temperatures of 1.6, 3.0, 5.0, 10.0 and 20.0°C. The A₀ values for both solid and liquid films increase with temperature at the same rate, which is greater than for the corresponding cross-sectional areas in the B and C states of solid stearic acid. There are minima in the compressibilities of both solid and liquid films around 5°C. Taken together, these data point to an interaction between water molecules and the stearic acid head groups, related to the water structure as manifested in the temperature of maximum density of 4°C.