A New Class of Nonionic Photosensitive Surfactants: Some Insights Concerning Conformations
Name
MEBCS015.pdf
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1.42 MB
Format
Adobe PDF
Checksum (MD5)
157448ddbc78b941eae92510a5d9e289
Author(s)
Smith, Kenneth A.
Hatton, T. Alan
Shang, Tiangang
Cicciarelli, Brad
Date Issued
January 2005
Series/Report no.
Molecular Engineering of Biological and Chemical Systems (MEBCS);
Abstract
We report on a new class of nonionic, photosensitive surfactants consisting of a polar di(ethylene oxide) head group attached to an alkyl spacer of between two and eight methylene groups, coupled through an ether linkage to an azobenzene moiety. Structural changes associated with the interconversion of the azobenzene group between its cis and trans forms as mediated by the wavelength of an irradiating light source cause changes in the surface tension and self-assembly properties. Differences in saturated surface tensions (surface tension at concentrations above the CMC) were as high as 14.4 mN/m under radiation of different wavelengths. The qualitative behavior of the surfactants changed as the spacer length changed, attributed to the different orientations adopted by the different surfactants depending on their isomerization states, as revealed by neutron reflection studies. The self-assembly of these photosensitive surfactants has been investigated by light scattering, small angle neutron scattering, and cryo-TEM under different illuminations. The significant change in the self-assembly in response to different illumination conditions was attributed to the sign change in Gaussian rigidity, which originated from the azobenzene photoisomerization.
Subjects
azobenzene
photosensitive surfactants
surface tension
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