title: Anisotropic aggregation and phase transition in Langmuir monolayers of methyl/ethyl esters of 2,3-dihydroxy fatty acids.
abstract: We studied interfacial properties of a series of methyl and ethyl esters of enantioenriched syn-2,3-dihydroxy fatty acids with different chain lengths at the air-water interface, using a Langmuir type film balance and a Brewster angle microscope (BAM). After analyzing their surface pressure (Pi)-area (A) isotherms, we inferred that these molecules existed as an E conformation in the liquid-expanded (LE) phase of monolayers, and the E conformation of molecules changed into a Z conformation during the LE-LC transition in a monolayer. BAM images evidenced the formation of elongated LC aggregates. This is possibly induced by the intermolecular hydrogen bonds, leading to the anisotropic growth of LC domains, on the basis of the FT-IR spectroscopy data. The enthalpy change of the LE-LC phase transition is considered to result from the three types of intermolecular interactions at the air-water interface during compression of these amphiphiles. These findings are discussed in terms of various physical factors that influenced intermolecular interactions and macroscopic aggregations of these amphiphiles.
authors.affiliation: Physikalisches Institut, Westfaelische Wilhelms-Universitaet Muenster, D-48149 Muenster, Germany.
authors.forename: Liyan
authors.initials: L
authors.lastname: Wang
authors.forename: Sandra
authors.initials: S
authors.lastname: Jacobi
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Michael
authors.initials: M
authors.lastname: Overs
authors.forename: Harald
authors.initials: H
authors.lastname: Fuchs
authors.forename: Hans Juergen
authors.initials: HJ
authors.lastname: Schaefer
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Jiacong
authors.initials: J
authors.lastname: Shen
authors.forename: Lifeng
authors.initials: L
authors.lastname: Chi