Langmuir
Letter
ASSOCIATED CONTENT
* Supporting Information
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S
Synthesis of azosurfactants; determination of cis:trans ratios by
1H NMR and UV spectroscopy. This material is available free
AUTHOR INFORMATION
Corresponding Author
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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The authors thank J. Ruchmann for synthesis and purification
of the photosurfactants as well as A. Saint-Jalmes and E. Rio for
stimulating discussions on foam stability. This work was
supported by ANR, Grant 07-BLAN-0278 and by SESAME Ile
de France
Figure 4. Schematic drawing of the phototriggered adsorption/
desorption exchanges between subphase and interface under light
stimulation. Without stimulation, the interface of a solution prepared
either under UV light or blue light prior to measurement is mostly
covered with trans isomers. When UV light is shone on the sample, the
adsorbed trans-isomers convert into their cis form that rapidly desorbs
from the interface. Note that this desorption process occurs whatever
the initial cis−trans composition of the bulk solution, i.e., for solutions
prepared under UV or blue light. In the case where UV light is shone
on a UV-adapted solution, the composition of the bulk solution does
not change with time.
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CONCLUSION
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AzoTMA is a promising tool, tailored to achieve photo-
switchable control of the stability of foams and of interfacial
properties. Several parameters that are known to be relevant in
foam stability are effectively affected by exposure to light,
including equilibrium surface tension, CMC, and dynamic
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dx.doi.org/10.1021/la204200z | Langmuir 2012, 28, 2308−2312