Simulation study of the collapse of Langmuir monolayers

PHYS 580

Christian D. Lorenz, cdlorenz@iastate.edu, Alex Travesset, trvsst@ameslab.gov, David Vaknin, vaknin@ameslab.gov, and Wei Bu, weibu@iastate.edu. Department of Physics and Astronomy, Ames Laboratory and Iowa State University, 12 Physics Hall, Ames, IA 50011
The collapsed regime of Langmuir monolayers follows when the film is compressed beyond the point of densely packed chains. Recent experimental work has found very interesting structures formed by the collapse of arachidic acid. We have used all-atom molecular dynamics simulations to gain a better understanding of the observed structures after collapse. We study systems in which the arachidic acid monolayers are on pure water and also on CaCl2 solutions. Using both constant surface area and compression simulations, we compare the behavior of the monolayer on pure water (nonionic) and on CaCl2 solutions (ionic). In both systems, physical properties (i.e. tilt angle and packing order) of the monolayer molecules are tracked as a function area per molecule. Also, we present a possible pathway through which the monolayer molecules take in order to form the collapsed structures observed experimentally.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006