Intramicellar Glass Transition and Liquid Dynamics in Soft Confinement

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.