RELAXATION OF SURFACE PRESSURE AND COLLAPSE OF UNIMOLECULAR FILMS OF STEARIC ACID

A study has been made of the time variations of π-A isotherms of stearic acid films at air/water interfaces using an automatic recording surface balance of the vertical pull type. The existence of coherent films below molecular areas of 22 sq. Å/molecule has been found to be dependent on the temperature, rate of compression, and the history of compression of a given film. The behavior at or near collapse, the decrease in π with time after sudden compression (relaxation), and the increase in π with time after sudden expansion (recovery) have been studied.The results have been interpreted on the basis of structural changes in the monolayer.