Chemistry Reference
In-Depth Information
Fig. 2.
Schematic sketch of the IRRAS setup: S
1
, S
2
,S
3
, and S
4
are mirrors
3. Results and Discussion
As an illustration of the versatility of BAM, examples of the investigation
of two problems will be given:
x the morphology changes during the compression of a slick on an
undulating water surface.
x the different morphologies attained by different spreading pro-
cedures of slick-forming material.
A sequence of BAM images obtained in the course of compression of a
slick consisting of hexadecanoic acid methyl ester (Palmitic acid Methyl
Ester = PME) is shown in Figs. 3-5. At large area per molecule, relatively
small domains prevail (Fig. 3), which, under compression, combine so that
kidney-like shapes are being formed (Figs. 4 and 5). A completely differ-
ent situation is encountered when the same slick material is being spread
from ethanol (Fig. 6). Already at large areas per molecule a foam-like
structure is being formed, i.e., a two-dimensional network that is expected
to exhibit quite different viscoelastic characteristics compared to those of
the morphological structures of the PME film displayed in Figs. 3-5.
The versatility of IRRAS for the
in situ
investigation of slick structures
on the air/ water interface is demonstrated in Fig. 7, which summarizes the
results of a relaxation experiment: a PME monolayer was generated at a
water surface and then compressed to 0.272 nm
2
/molecule. In the course of
