Growth and morphology in Langmuir monolayers

Abstract

We show that domain growth of condensed phases from a metastable phase in Langmuir monolayers presents several stages. At the very beginning, depending on the supersaturation level, structures evolve through a tip-splitting dynamics. If supersaturation levels are high, there is a morphological transition, domains grow with needle tips that show as growth proceeds, side branching. The way in which the instability starts at round domains when a small lateral pressure jump is applied to the monolayer is also shown. A model for a monolayer interacting with the subphase is presented. This model can be related to the theory of dynamic phase transitions, where morphological structures and morphological transitions are predicted.

Domain Growth, Pattern Formation, and Morphology Transitions in Langmuir Monolayers. A New Growth Instability

“…(c) A model where a Laplacian equation in the chemical potential can be recovered from the hydrodynamic model with Marangoni flow, including the necessary boundary conditions, to explain the morphology structures and the morphology transitions, as previously reported. 27,28 Our experiments agree with the kinetic morphology diagram. [6][7][8][9][10][11] However, the underlying physics involved in LM is different from the underlying physics in the Mullins-Sekerka instability; diffusional processes are not involved.…”

“…Apparently, we have lost the general picture given by the diffusional model proposing the existence of a diffusion zone, which with eq 7 and the boundary conditions given by eqs 1 and 2, successfully explains the pattern formation and the morphology evolution in LMs. 27,28 In the same way, apparently, we have also lost the connection with the morphology diagram with regions of different morphological structures, [6][7][8][9][10][11] determined by the control parameters ∆ and ε, as explained above. Here, we will assess in what conditions the 2D hydrodynamic eq 4 can recover that picture related to pattern formation and to the morphology diagram.…”

Self-assembly of metastable langmuir monolayers on planar solid surfaces

“…The morphologies of nonequilibrium two dimen sional (2D) mesophases are structurally diverse and vary from so called circular (compact) domains with isotropic boundaries [41,42] to dendrite type [33], branched (free of orientational order) [43], and fractal [20,44] structures, which are rather similar to those resulting from nonequilibrium 3D crystallization. The mechanisms of nonequilibrium structuring in bulk and at the interface are, however, fundamentally dif ferent.…”

“…Nevertheless, at present, most authors of the relevant studies agree that the instability that arises in a mono layer is mainly determined by the difference between the structures of condensed and liquid phases [43,44]. Being in a liquid expanded state, a monolayer exhibits the compressibility of a gas, while the intermolecular interactions in it are as strong as those in liquids [14].…”

“…Recently, Flores et al studied the evolvement of the instability of interfaces by the examples of nonequilib rium phase transitions in monolayers of dioctadecy lamine, sodium ethylpalmitate, and sodium ethyl stearate [41,43]. They related the development of this instability to the interplay between the chemical potential gradient at the interface between liquid and condensed phases (destabilizing factor) and the linear tension of a condensed phase domain being formed (stabilizing factor).…”