Intramicellar Glass Transition and Liquid Dynamics in Soft Confinement

Abstract

We explore the dynamics of viscous propylene glycol (PG) near its glass transition for the case of soft spatial confinement. The supercooled liquid is geometrically restricted by the reverse micelles of a glass-forming PG/AOT/decalin microemulsion, with the intramicellar dynamics being probed by triplet state solvation dynamics. While hard confinement by porous solids is known to result in slower dynamics and an increased glass transition temperature T(g) of PG, the nanodroplets suspended in a more fluid environment display faster structural relaxation, equivalent to a reduction of T(g) as observed in freestanding polymer films.

Water confined in self-assembled ionic surfactant nano-structures

“…Size, shape and connectivity of the confining matrix, together with the nature of the charged interfaces and the interplay among hydrophobic, electrostatic and Van der Waals forces, have been shown to significantly alter the fluid properties compared to those of the bulk [7][8][9][10][11][12] . Most part of these studies has focused on confinement in hard matrices but, more recently, the interest in soft confinement, where boundaries mobility cannot be neglected, has substantially grown 13,14 . Much more complex ionomer membranes, like Nafion, have also been extensively scrutinized 15 .…”

Dynamics of Materials at the Nanoscale: Small‐Molecule Liquids and Polymer Films

“…It is clear that such macroscopic effects cannot fully account for the observed behaviors, although they may contribute. The second important factor is the exact nature of the confinement as "hard" or "soft", and this is an aspect of the confinement properties that has been emphasized by Richert and co-workers [Wang et al, 2004;He et al, 2005He et al, , 2007. The important point to be taken away from the work of Richert is that there does seem to be an influence of the actual "hardness" of the confinement on the dynamics (or the T g ) of the confined fluid of interest and how strongly the slowing due to this interaction is transmitted into the interior of the liquid.…”

“…The important point to be taken away from the work of Richert is that there does seem to be an influence of the actual "hardness" of the confinement on the dynamics (or the T g ) of the confined fluid of interest and how strongly the slowing due to this interaction is transmitted into the interior of the liquid. This is contrasted to the "soft" microor nanoemulsions [Wang et al, 2004;He et al, 2005] that were also mentioned above [MacFarlane and Angell, 1982;Angell et al, 1984] and where the dynamics of the confined fluid have been interpreted to take on the rapid dynamics of the soft wall. Needless to say, these results continue to be widely discussed.…”

Salt‐Acid‐Surfactant Lyotropic Liquid Crystalline Mesophases: Synthesis of Highly Transparent Mesoporous Calcium Hydroxyapatite Thin Films

“…This confinement in nanoscale space is known as the soft confinement effect (SCE). [3][4][5][6] In these assemblies, the metal ions have either a hydration sphere or are coordinated by water coordination. [1,2] For instance, aqua complexes of most first-row and some second-row transition metals undergo self-organization with non-ionic surfactants into various mesostructures.…”