title: Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers.
abstract: A self-assembled phospholipid monolayer at an air-water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir-Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics.
authors.affiliation: Department of Mechanical Engineering, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.|Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii , Honolulu, Hawaii 96826, United States.
authors.forename: Yi Y
authors.initials: YY
authors.lastname: Zuo
authors.affiliation: Department of Mechanical Engineering, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.
authors.forename: Rimei
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.|College of Electronic Engineering, South China Agricultural University , Guangzhou, China 510642.
authors.forename: Xianju
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.
authors.forename: Jinlong
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto , Toronto, Ontario Canada , M5S 3G8.
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Policova
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto , Toronto, Ontario Canada , M5S 3G8.
authors.forename: A Wilhelm
authors.initials: AW
authors.lastname: Neumann