title: Study of relaxation process of dipalmitoyl phosphatidylcholine monolayers at air-water interface: effect of electrostatic energy.
abstract: The instability of organic monolayer composed of polar molecules at the air-water interface has been a spotlight in interface science for many decades. However, the effect of electrostatic energy contribution to the free energy in the system is still not understood. Herein, we investigate the mechanical and electrical properties by studying the isobaric relaxation process of a dipalmitoyl phosphatidylcholine monolayer on water subphase with various concentrations of divalent ions to reveal the effect of electrostatic energy on thermodynamics and kinetics of the collapse mechanism. Our results demonstrate that electrical energy among the dipolar molecules plays an important role in the stability of monolayer and enhances the formation of micelles into subphase under high pressure. In addition, to confirm the electrostatic energy contribution, the well-known thermal effect on the stability of the film is compared. Hence, the general description of the monolayer free energy with contribution of electrostatic energy is suggested to describe the phase transition.
authors.affiliation: Department of Physical Electronics, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan.
authors.forename: Wei
authors.initials: W
authors.lastname: Ou-Yang
authors.forename: Martin
authors.initials: M
authors.lastname: Weis
authors.forename: Takaaki
authors.initials: T
authors.lastname: Manaka
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Iwamoto
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000388:Air; D011312:Pressure; D055672:Static Electricity; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine