NAMS 2002 Workshop - ICOM 2008

membranes. The analysis of the light scattering intensity did not make it possible
to separate the bulk states of these components. That is why the polarimetric
behavior of each sample was studied. The analysis of the scattered wave
polarization state at low resolution measurements clearly revealed that the origin
of the light scattering lies essentially in the bulk. Indeed, the polarimetric phase
shift varies very quickly, which is representative of bulk scattering. With low angle
resolution, comparison of different membrane cut off is not significant. To analyze
statistically the oscillations of the polarimetric phase shift as a function of the
scattering angle, the same measurements were run at high angle resolution. By
representing the standard deviation of the polarimetric phase shift, it is possible
to identify a difference in membrane behavior. Logically, the phase shift standard
deviation increases with the porosity. To confirm this result, some theoretical
investigations were run. Simulations were performed using the differential
method, which is a rigorous method for the resolution of Maxwell’s equations.
The polarimetric phase shift of the wave scattered by a porous structure with a
defined volumic structure (pore size and material) was calculated. The
membranes were modeled by a volume 8 μm in width and 1 mm in depth, filled
with a mixture of air (optical refraction index:1) and zircone (optical refraction
index: 2.2, absorption neglected). In the case of membranes with porosities
ranging from 20 to 400 nm, modelling step shows that the standard deviation
increases with the sample porosity. These numerical calculations confirm the
evolution observed for the experimental results.
The ellipsometry of angle resolved scattering can be used for the structural
characterization of the organic membranes whatever the membrane geometry.
The study of these membranes must allow to develop a methodology in order to
improve the understanding of the fouling mechanisms, to correlate the
membrane properties (membrane cut- off, membrane material) to the fouling and
to minimize the membrane fouling.