Micro-Phase Separation in Binary Mixed Langmuir Monolayers of n-Alkyl Fatty Acids and a Perfluoropolyether Derivative

Abstract

Micro-phase separation in binary mixed Langmuir monolayers of cadmium salts of n-alkyl fatty acids (CH3(CH2)n-2COOH; Cn (n ) 18, 20, 22, 24)) and a perfluoropolyether surfactant (F(CF(CF3)CH2O)3CF-(CF3)COOH, PFPE) is studied by film balance measurement and atomic force microscopy (AFM). At different temperatures, mixtures of Cn/PFPE in chloroform were spread onto the aqueous Cd 2+ subphase and deposited on silicon wafers. AFM images showed that Cn and PFPE separate into microscopic domains of condensed phase and a surrounding matrix of expanded phase, respectively, in their mixed monolayers. The morphological feature of phase-separated structures was characterized by characteristic length (λ) expressing the periodicity of two-phase distribution and fractal dimension (D) of Cn domains reflecting the complexity of domain shape, which were determined through AFM image analyses. It was found that the monolayer morphologies systematically vary with alkyl chain length of Cn and temperature of the water surface; circular-shaped condensed phase microdomains with D of about 1.1 are formed at λ of 7-9 µm when the mixed monolayers are prepared using a shorter alkyl chain fatty acid and/or at a higher temperature, whereas branched narrow domains with D close to 2 are formed at λ of approximately 4 µm when a longer chain fatty acid is used at a lower temperature.

Adsorption of Dimethyl Silicone onto Hair-surface Models Prepared with Micro-phase Separated Monolayers

“…The image shows that round shaped micro-domains with a size from one to a few μm were dispersed in an expandedphase matrix. This morphological feature was very similar to micro-phase separated structures typically formed in the mixed monolayer systems of condensed phase and expanded phase-forming amphiphiles such as n-octadecyltrichlorosilane and a partially fluorinated silazane derivative 19,20 , and n-alkyl fatty acids and PFPE 20,21 , respectively. The height of the micro-domains from the surrounding region was typically about 1.8 nm according to a height profile along the white line in the image.…”

Surface Morphology of Cosmetic Film Consisting of PEG-Diisostearate Amphiphilic Random Copolymer, Xanthan Gum, and Solvents

“…It seems likely that the phase separation occurred via the spinodal decomposition when considering the good regularity. These characteristic morphologies have been similarly observed for n-alkyl fatty acids/perfluoropolyether 21 , polystyrene/poly methylmethacrylate 22 26 , and deuterated polys t y r e n e / p o l y i s o p r e n e 27 d e r i v a t i v e s . T h e s u r f a c e morphologies of these systems are dependent on several factors including the interfacial or line tension of the two phases, electrostatic repulsive force within the domains, viscosity of the two liquid phases, solubility of the polymer in the solvents, nature of the substrate, etc.…”

Control of Two‐Dimensional Nanopatterns by Adjusting Intermolecular Interactions

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Self-assembly enables exquisite control over the structures of various materials such as ultrathin organic films, [1][2][3][4] polymer films, [5][6][7] and inorganic nanoparticle assemblies. [8] Organic molecules are particularly suited for exploiting self-assembly because of the controllability of their molecular properties and intermolecular interactions using molecular design.

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“…[8] Organic molecules are particularly suited for exploiting self-assembly because of the controllability of their molecular properties and intermolecular interactions using molecular design. Lateral patterning of organic materials has been performed using both top-down [6,9] and bottom-up [1][2][3][4][5]7] methods. However, construction of controllable nanostructures consisting of small organic molecules is difficult using bottom-up methods.…”

“…Phase separation often occurs in mixed-Langmuir and LB films, the structures of which are governed by two competing interactions of line tension and dipole-dipole interactions. [1,3,10] Line tension favors the formation of large circular domains. Dipole-dipole interactions in monolayers is repulsive because each molecule is aligned in a parallel manner.…”