Synergistic effect of a fluorinated azobenzene for transforming spherical micelles into thread-like micelles with a disk-like cross-section
Por:
Rincon-Londono, Natalia, Luviano, Alberto S., Tavera-Vazquez, Antonio, Figueroa-Gerstenmaier, Susana, Castillo, Rolando
Publicada:
30 nov 2023
Ahead of Print:
1 sep 2023
Resumen:
The free energy in solutions of amphiphilic molecules leads to the
formation of supramolecular structures, often making spherical
aggregates, worm-like micelles, vesicles, and lamellae. In this work, we
add a fluorinated azobenzene, 4-(4-trifluoromethoxy phenyl azo) phenol
(Azo-3F) to a solution mainly made of spherical and rodlike micelles of
CetylTrimethylAmmonium Bromide (CTAB) and sodium salicylate (NaSal).
These structures transform to disk-like micelles, which concatenate
through hydrogen bridges to form long thread-like structures highly
similar to worm-like micelle structures. This conclusion was reached
after observing that NMR results suggest the formation of aggregates in
solution with Azo-3F molecules inside them. Viscosity increases by three
orders of magnitude at low shear rates when Azo-3F is added, and it
shear-thins as the shear rate increases. The viscoelastic spectra show
that the fluid changes from viscous to viscoelastic. Cole-Cole plots
follow semicircles, typical of Maxwellian behavior below similar to 35
degrees C. Cryo-TEM micrographs of the solution with Azo-3F show giant
thread-like structures, and cross-sectional analysis of SAXS and WAXS
profiles predict oblate ellipsoidal structures. In addition, MD
simulations show that the disk-like micelles interact mainly through
hydrogen bonds and electrostatics, forming micellar strings. These
strings behave similarly to worm-like micelles, explaining why the
solution behaves as a Maxwellian fluid at relatively low temperatures.
Consequently, when some specific molecules are introduced in
supramolecular structures, such as a spherical micelle, they can be
transformed into disk-like micelles that assemble into thread-like
micelles.
Filiaciones:
Rincon-Londono, Natalia:
Instituto de Física, Universidad Nacional Autónoma de México, P.O. Box 20-364, Mexico City, 01000, Mexico
Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Universidad de Guanajuato, Campus León, Gto, León, Mexico
Luviano, Alberto S.:
Departamento de Ingenierías Química, Electrónica y Biomédica, División de Ciencias e Ingeniería, Universidad de Guanajuato, Campus León, Gto, León, Mexico
Tavera-Vazquez, Antonio:
Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, United States
Figueroa-Gerstenmaier, Susana:
Departamento de Ingenierías Química, Electrónica y Biomédica, División de Ciencias e Ingeniería, Universidad de Guanajuato, Campus León, Gto, León, Mexico
Castillo, Rolando:
Instituto de Física, Universidad Nacional Autónoma de México, P.O. Box 20-364, Mexico City, 01000, Mexico
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