Liquid Expanded and Condensed Films

Strong hydrogen bonding with subphase water 

This means that such deviations thus allow one to estimate these interactions. 

Liquid condensed films (Lcq) As the area per molecule (or the distance between molecules) is further decreased, there is observed a transition to a so-called liquid condensed (L o) state. These states have also been called solid expanded films (Adam, 1930 Adamson and Cast, 1997 Birdi, 1989, 1999 Gaines, 1966), which will be later discussed in further detail. The n versus A isotherms of n-pentadecylic acid (amphiphile with a single alkyl chain) have been studied, as a function of temperature. II-A isotherms for two chain alkyl groups, as lecithins, also showed a similar behavior. 

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The surface pressure (jt) is the difference in surface tension between that of the pure sub-phase liquid surface and that when the surface is covered by a film. Surface pressure isotherms for materials of low relative molecular mass are values of Jt plotted as a function of the area of surface available per molecule. For spread films of materials of low relative molecular mass, the surface pressure isotherm may display a number of transitions as the area available is decreased. The classification of these isotherms into various types is discussed in various texts on surface and interfacial chemistry (Jaycock and Parfitt 1981, Adamson 1990, MacRitchie 1990). Spread polymer films do not show the same range of isotherm behavioxu as that for compounds of low relative molecular mass. Generally only two types are observed, namely liquid expanded and condensed films. Schematic surface pressure isotherms of these two types are shown in figure 8.1 these are plotted in the manner most common for spread... 

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