Brewster angle microscopy study of supersaturated monolayers of long chain fatty acid methyl esters before and beyond the collapse pressure

Abstract

The constant surface pressure relaxation of supersaturated methylarachidate and methylbehenate monolayers between the equilibrium surface pressure and the collapse point is analyzed quantitatively on the basis of the general nucleation-growth-collision theory. In all cases, the calculated nucleation rate constants are quite low corresponding to the conditions for progressive nucleation. The transformation kinetics of monolayer material into three-dimensional (3D) aggregates before and beyond the collapse pressure is visualized by Brewster angle microscopy. Both methylester monolayers evolve compact, irregularly shaped 3D aggregates of microscopic scale within the homogeneously reflecting monolayer. An abrupt increase in growth rate for the 3D nuclei beyond the collapse pressure determines the special morphological features of the 3D aggregates formed in this range.