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Microphotonics for monitoring the supramolecular thermoresponsive behavior of fatty acid surfactant solutions

  • Castro-Beltrán, R.
  • Garnier, Lucas
  • Saint-Jalmes, A.
  • Lhermite, Hervé
  • Cormerais, H.
  • Fameau, Anne-Laure
  • gicquel, Eric
  • Bêche, Bruno
Publication Date
Mar 19, 2020
Kaleidoscope Open Archive
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The development and the ability of an optical integrated polymeric resonator, acting as a surface lightprobe, for monitoring temperature-induced supramolecular phase transitions is presented in this work. Thehomogeneous detection of the transitions between different self-assembled structures in an aqueous solutionof fatty acids (12-hydroxystearic acid, in association with amino-pentanol) was studied by investigating thecoupling between the solution and the integrated photonic micro-cavity. Tuning the self-organized assembliesof surfactant is very attractive for many applications, such as cosmetic products, food, drug delivery andmedical, and the development of alternative tools – especially those requiring minute amount of solution – tomonitor their structural changes are essential. These original studies at temperatures ranging from 17 to 24 ◦C,based on a statistical treatment of optical resonance spectra, have evidenced the thermoresponsive nature ofthe optical features, and that different regimes occur with temperature. The optical results were corroboratedwith the measurement of the solution viscosity as a function of temperature, confirming that we can ascribethe optically-detected regimes to a surfactant assembly shifting reversibly from a tubular shape to a micellarone. The comparison between the optical and the rheological responses showed different accuracies: whilethe viscosity data exhibited a rather smooth and monotonous transition, the behavior changes were sharperand non-monotonous in terms of optical properties, allowing us to unambiguously identify in intermediateregime between 18.5 and 20 ◦C. These morphological transition experiments represent a unique opportunityto extend the numbers of available techniques studying these systems through integrated optical techniqueswith potential opportunities of real time detection and working on low sampling volume.

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