Morphology of Langmuir Monolayer Phases
Micrometer-scale domains formed during the first-order ‘main’ phase transition within Langmuir monolayers show characteristic shapes that are a consequence of the molecular interactions within the surface film. The relevant Hamiltonian includes the (one-dimensional) line tension, long-range dipole-dipole repulsion and a spontaneous curvature deriving from the chirality of the constituent molecules. Experimental observations have been compared with computer models in which domains were approximated by finite segments and their energy minimized with respect to the layout of the segments within the plane. Several levels of sophistication have been analyzed: (a) Elongated domains that are isolated within the film area, such that domain-domain interactions may be neglected; (b) isolated domains with non-trivial shapes; (c) elongated domains in a crowded situation where domain-domain interactions have been taken into account. Since nucleation events lead to a random distribution of individual domains within an ensemble in the latter case, the experimental results and the segmented models are at best similar in their pattern formation. These similarities are quantitatively compared using Minkowski functionals.
KeywordsLine Tension Lipid Monolayer Langmuir Monolayer Spontaneous Curvature Domain Shape
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