Optical measurements of the phase diagrams of Langmuir monolayers of fatty acid, ester, and alcohol mixtures by Brewster-angle microscopy

Abstract

Surface pressure-temperature phase diagrams have been determined by Brewster-angle microscopy for Langmuir monolayers of heneicosanoic acid with the esters methyl and ethyl heneicosanoate and octadecanoic acid with methyl, ethyl, and propyl octadecanoate. The behavior is similar to that found previously in mixtures of an acid and an alcohol. In each case with increasing ester concentration the L 2 /L 2 Ј phase boundary moves toward lower pressure and higher temperature while the L 2 /Ov boundary moves toward lower pressure and lower temperature. The L 2 Ј and Ov phases eventually merge and the boundary with the L 2 phase moves to zero pressure. The phase diagram of eicosyl acetate is similar to that of the fatty acids. We attribute the variations in the diagrams to the extent of hydrogen bonding between the head group and the subphase.

Mixed monolayers involving DPPC, DODAB and oleic acid and their interaction with nicotinic acid at the air–water interface

“…BAM analysis has been used to investigate phase diagrams of model amphiphilic molecules (Teer et al, 1997) and monolayer phase changes of more complex molecules (Balogh et al, 2001). In the present work, the nature of the first and second plateaus, observed in the π-A curve of X OA = 0.8 of system DPPC/OA ( Fig.…”

Temperature dependence of the organization and molecular interactions within phospholipid/diacetylene Langmuir films

“…The interactions and organization of two molecular components occupying the same two-dimensional space have been explored by thermodynamic [6,7] and microscopic [2,[8][9][10] approaches. Monolayers component miscibility [6], distribution [11] domain growth [12], nucleation [13], phase transition [14], and collapse [15] processes have attracted great interest ever since the early pioneering studies of Langmuir films [16,17].…”

Anisotropic aggregation and phase transition in Langmuir monolayers of methyl/ethyl esters of 2,3-dihydroxy fatty acids

“…Alexander and Schulman had reported that on compression the head group of methyl octadecanoate underwent a conformational change from the Z to the E form [23,[34][35][36]. We inferred that M-DHO underwent similar conformational change, though its head group was not the same as methyl octadecanoate.…”

“…8, which is developed from the model in Ref. [35]. On the basis of this model, the difference in molecular area in Fig.…”