A pendant drop technique for measuring pi - A isotherms

A co-axial tube arrangement, in conjunction with a modified version of the Axisymmetric Drop Shape Analysis (ADSA) protocol, was designed and used to investigate surface pressure - area isotherms of pentadecanol, C15, and octadecanol, C18, monolayers on pure water. This was done at several temperatures and the collapse pressure, molecular area at collapse, the limiting molecular area and the transition pressures were investigated. The error associated with the transition were also determined. Finally, we show that the shape of the isotherm does not depend on the initial monolayer structure for low molecular weight, insoluble alcohols. This was done by comparing two techniques to disperse the insoluble alcohol solutions onto a pendant drop. Octadecanol on water was used to test this approach because there was sufficient published data using the Langmuir trough and ADSA to make a comparison.