Unveiling Texture and Topography of Fatty Acid Langmuir Films : Domain Stability and Isotherm Analysis

• 3D texturing by self-assembly at the air-water interface has recently been proposed. The hypothesis of this work is that, if this is true, such domain formation should be inferable directly from pressure-area isotherms and be thermodynamically stable. Monolayers of branched fatty acid mixtures with straight chain analogues and their stability are thus studied using a combination of pressure-area isotherms, thermodynamic analysis, in situ Brewster angle microscopy, and atomic force microscopy of both LB-deposited and drop-cast films on silicon wafers. Isotherms reflecting the behavior of monodisperse 3D domains are shown to be independent of compression rate and display long-term stability. Gibbs analysis further confirms the thermodynamic rather than kinetic origin of such novel species by revealing that deviations from ideal mixing can be explained only a priori by differences in the topography of the water surface, thus also indirectly confirming the self-assembly deformation of the water interface. The intrinsic self-assembly curvature and miscibility of the two fatty acids is confirmed by drop-casting, which also provides a rapid, tunable thin-film preparation approach. Finally, the longevity of the nanostructured films is extraordinary, the long-range order of the deposited films increases with equilibration time at the water interface, and the integrity of the nanopatterns remains intact on the scale of years.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Keyword

Air; Drops; Film preparation; Isotherms; Phase interfaces; Silicon wafers; Textures; Thermoanalysis; Thin films; Topography; fatty acid; nanofilm; silicon; surface water; water; 3D texturing; Air/Water Interfaces; Atomic-force-microscopy; Brewster angle microscopy; Domain formation; Fatty acid mixture; Pressure-area isotherms; Thermo dynamic analysis; Thermodynamically stable; Water interface; article; atomic force microscopy; Brewster angle microscopy; compression; controlled study; isotherm; kinetics; longevity; miscibility; pressure; thermodynamics; topography; Fatty acids

Publication and Content Type

ref (subject category)

art (subject category)