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Native alpha-cyclodextrin (alpha-CD) is found to spontaneously form films at aqueous solution/air interfaces. Shape-response measurements to volume perturbations on drops hanging from a capillary indicate that temperature and sodium dodecyl sulfate (SDS) concentration strongly modify the viscoelastic properties of such films. By using isothermal titration calorimetry (ITC), Brewster angle microscopy (BAM), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, it is shown that the films consist of self-assembled nanotubes whose building blocks are cyclodextrin dimers (alpha-CD2) and alpha-CD2-SDS1 complexes.

We present the pressure area isotherms for Langmuir films made of calix[8]arene, the calix[8]arene/C60 complex, and the calix[8]arene/C70 complex, all of them measured at 306.1 K. A Brewster angle microscope was used to observe the phases shown by the π−A isotherms. In these three cases, we found a solid phase and its solid−gas coexistence but no expanded liquid phases. The Langmuir films made of calix[8]arene and the calix[8]arene/C60 complex are very similar. The experimental information is consistent with the assumption that C60 is situated inside the cavity of calix[8]arene. The Langmuir films of calix[8]arene and the calix[8]arene/C70 complex are not very similar; we present a discussion to explain the origin of this difference.

The phase diagram of dioctadecylamine Langmuir monolayer has been determined from pressurearea isotherms and from direct observations of the monolayer using Brewster angle microscopy. We describe the observed domains, textures, and phase boundaries for the mesophases presented by this system between 5°C and 45°C, at pHϭ3. The phases were named as G, LE, S 1 , and S 2 according to their apparent texture. Contrast between domains of condensed phases is quite low, indicating small tilting of the amine tails. The G -S 1 , G -S 2 , G -LE, and LE-S 1 transitions seem to be of first order; meanwhile, the S 1 -S 2 transition seems to be of second order. We observed how the froths changed when the area density increases at constant pressure, along the G -L, G -S 1 , and G -S 2 phase transitions. In the L -S 1 transition, the shape of the domains of the emerging phase is of sixfold dendrites. The phase diagram obtained is very different from those obtained for single chain amphiphiles. In this system, the extent of the phases depends on the acid used to fix the pH. In addition, all our observations indicate that dioctadecylamine does not form a monolayer above pHϳ3.9.

The phase diagrams of Langmuir monolayers of heptadecanoic (C17), nonadecanoic (C19), and heneicosanoic (C21) acids have been determined from pressure-area isotherms, and from direct observations of the monolayers using Brewster angle microscopy. In this paper, we describe the observed domains, textures and phase boundaries for all mesophases presented by these fatty acids between 2° and 45 °C. The phase diagrams of the three fatty acids can be superposed moving the temperature scale according to the number of carbons in the tail of the fatty acids. The L2/Ov phase transition, which is not detected through isotherms, was observed in all the fatty acids under study. At low temperatures, CS,L2′, and L2″ phases of C21 were observed, as well as, the transitions among them. Also, we observed in C21 a new phase located among the phases L2,L2′, and L2″. This phase was found recently, in the relative same place, in the fatty acid C20 with a tilting azimuth between the nearest-neighbor and the next nearest-neighbor directions. In the crystalline phases of the monolayer of C21, L2″ and CS, we observed localized oscillations. These localized oscillations can be observed by long periods of time. The number of localized oscillations in the monolayer can be modified by long periods of relaxation or by heat treatment. Our results seem to indicate that these localized oscillations are areas with high density of defects, expelling material out of the monolayer. Therefore, they could be important in the events previous to the collapse.