Phase behavior of 2,3-disubstituted methyl octadecanoate monolayers at the air-water interface.
The phase behavior of 2,3-disubstituted methyl octadecanoate monolayers at the air-water interface is studied by film balance and a Brewster angle microscope (BAM). The comparison of the surface pressure-molecular area (pi-A) isotherms with the corresponding BAM images provides information on the phase behavior of the monolayers. Variations in the phase behavior of different 2,3-disubstituted methyl octadecanoate monolayers can be correlated with the size of the headgroups, the interactions between the polar molecular moieties and the subphase, and the intermolecular interactions. The enlarging of the headgroups makes forming a condensed monolayer difficult for the molecules, even after introduction of substituents giving rise to the formation of hydrogen bonds between the molecules, which may balance the steric repulsion and stabilize the monolayers. Model calculations of the two-dimensional lattice structure of the 2,3-disubstituted methyl octadecanoates on basis of the pg and p1 space group are performed and correspond well with the experimental results.
Chen
Xiaodong
X
Physikalisches Institut, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
Wiehle
Susanne
S
Chi
Lifeng
L
Mück-Lichtenfeld
Christian
C
Rudert
Rainer
R
Vollhardt
Dieter
D
Fuchs
Harald
H
Haufe
Günter
G
D000388:Air; D006860:Hydrogen Bonding; D007700:Kinetics; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008968:Molecular Conformation; D010316:Particle Size; D013228:Stearates / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water
C512255:2,3-dimethyl octadecanoate; D008567:Membranes, Artificial; D013228:Stearates; D014867:Water