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					         A time- and space-resolved neutron imaging study
                of soft and complex matter systems
    Helen E. Hermes1, Gabriel Frei2, Anders Kästner2, Eberhard Lehmann2 ,
          Burkhard Schillinger3, Michael Schulz3, Stefan U. Egelhaaf1
                  Heinrich-Heine-Universität, Düsseldorf, Germany
                             PSI, Villigen, Switzerland
                   FRM II and TU-München, Garching, Germany



Due to recent technical improvements in neutron imaging instrumentation, especially
the scintillators used, it is now possible to quantitatively investigate samples in-situ
with a resolution of a few tens of micrometers and seconds using this technique. We
have explored the application of this method to determining time- and space-resolved
solvent profiles in a variety of soft and complex matter systems including biologically-
relevant systems, nanoporous materials, amphiphiles and polymers. In this
presentation, I will focus on our studies on amphiphilic systems.

In solution, amphiphiles such as lipids and copolymers can self-assemble into a
variety of structures [1]. When a droplet of such an amphiphile is contacted with
water, the osmotic pressure difference results in an influx of water which causes a
non-equilibrium change in the concentration-dependent structure. Currently, our main
interest in this process is to develop a fundamental experimental picture of how
solvent diffuses into and dissolves a droplet. To date, much information has been
obtained using optical techniques [2]. However, the optical transmission of a sample
is dependent on both concentration and structure so that it is not possible to
differentiate between changes in these. By contrast the transmission images
obtained by neutron imaging yield concentration profiles with a high degree of
accuracy. These profiles are allowing us to investigate in detail flow in confined
geometries and the effects of phase boundaries on diffusion profiles and rates.

[1] see for example, P. Alexandridis, D Zhou, A. Khan, Langmuir, 12 (2690-2700), 1996
[2] M. Buchanan, S.U. Egelhaaf, M.E. Cates, Langmuir, 16 (3718-3726), 2000

                     JUM@P ’09: Joint Users’ Meeting at PSI, October 12-13, 2009

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