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Detection of Two Glass Transitions on Triton X‑100 under Confinement

Merino, Esther G. ; Neves, Paulo D. ; Fonseca, Isabel M. ; Danéde, Florence ; Idrissi, Abdenacer ; Dias, C. J. ; Dionísio, Madalena ; Correia, Natália T.

Journal of physical chemistry. C, 2013-10, Vol.117 (41), p.21516-21528 [Periódico revisado por pares]

Columbus, OH: American Chemical Society

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  • Título:
    Detection of Two Glass Transitions on Triton X‑100 under Confinement
  • Autor: Merino, Esther G. ; Neves, Paulo D. ; Fonseca, Isabel M. ; Danéde, Florence ; Idrissi, Abdenacer ; Dias, C. J. ; Dionísio, Madalena ; Correia, Natália T.
  • Assuntos: Chemical Sciences ; Condensed matter: structure, mechanical and thermal properties ; Exact sciences and technology ; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals ; or physical chemistry ; Physics ; Structure of solids and liquids; crystallography ; Theoretical and
  • É parte de: Journal of physical chemistry. C, 2013-10, Vol.117 (41), p.21516-21528
  • Descrição: Because of the strong tendency of Triton X-100 to crystallize, inclusion in a SBA-15 matrix of 5.7 nm in pore diameter was used as a means to suppress crystallization. Clear evidence that Triton X-100 exists under confinement in the amorphous and supercooled state is given by X-ray diffraction supported by differential scanning calorimetry and dielectric relaxation spectroscopy. From the thermogravimetric analysis, a loading degree of 50% (wt) was estimated; the decomposition of confined Triton X-100 follows a two-step profile, indicating that molecules are partitioned between bulklike and adsorbed, the latter fraction being in a higher proportion. This allowed the unequivocal detection by DSC of two well-resolved glass transitions (∼20 K apart), which is a remarkable result obtained by conventional calorimetric analysis in confined systems. The two molecular populations have different mobilities giving rise to two different dielectric relaxation processes: an αTr/SBA bulklike process associated with molecules located more in the center of the pores, slightly slowed down relative to bulk α-relaxation, and an S-process due to molecules absorbed at the walls with significantly hindered mobility. Moreover, an MWS process is detected due to interfacial polarization that builds up between the adsorbed Triton X-100 molecules and SBA pore walls whose temperature dependence seems to be correlated with the one of the S-process. The inclusion in SBA-15 revealed to be a good strategy to simultaneously avoid crystallization and achieve a long-term stabilization of the disordered form.
  • Editor: Columbus, OH: American Chemical Society
  • Idioma: Inglês
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