Octadecylurea monolayers

Abstract

Monolayers of octadecylurea have been studied over the temperature range 14-30°C by measuring surface pressure-area isotherms and evaporation resistances. The monolayer can exist in two distinct condensed phases: the α phase, with a limiting area of about 0.195 nm2 molecule-1, and the β phase, with a limiting area of about 0.250 nm2 molecule-1. The β phase is stable at low temperatures and the α phase tends to be stable at higher temperatures. The surface pressure of the α-β transition decreases with temperature. Significant evaporation resistances were observed in both the α and β phases and in the α-β transition region. These evaporation data are not consistent with either the energy barri..