13: Long-range Dipole Forces in Lipid Monolayers
The immiscible liquids formed in monolayers were a theoretical challenge. I had a theoretician postdoc from Berkeley at that time and proposed to him that the shapes of monolayer domains resulted from a combination of electrostatic dipolar repulsions within (and between) domains, and line tension. Initially my postdoc vigorously disagreed. However he then made the relevant calculations and proved me right. Dozens of interesting papers followed. We were unaware of the somewhat earlier work of Andelman et al. who reached a similar conclusion. Their work addressed periodic patterns, which were not our main interest. We were interested in the sizes and shapes of finite domains at thermal equilibrium. See (327). Similar effects are to be found in ferrofluids. (The work of Andelman et al., may have been stimulated by our finding of periodic structures in monolayers of cholesterol and phospholipids (288, 437).)
The long-range dipole repulsion in monolayers makes a significant contribution towards lowering the critical temperature whereas this is not the case for bilayers.