Soft Confinement Effects on Dynamics of Hydrated Gelatin

Soft materials under geometrical confinement are ubiquitous and known to exhibit fascinating properties, sometimes even antagonistic to their bulk counterpart. Here, we explore the structural relaxation dynamics (α-relaxation) of the biopolymer gelatin dissolved in water (bulk form) and under soft spatial confinement using dielectric relaxation spectroscopy over a wide frequency range starting from 1 Hz up to 2 GHz. The gelatin-water mixture (hydrated gelatin) is geometrically restricted by the soft fluctuating surfactant monolayer of water-AOT (sodium bis(2-ethylhexyl)sulfosuccinate)-n-decane reverse microemulsions (MEs), where the core size of microemulsion droplets varies from 3.7 to 5.0 nm. The stability of the droplet phase of microemulsion after the incorporation of gelatin is confirmed by the small-angle neutron scattering (SANS) experiment. Notably, the hydrated gelatin in soft confinement exhibits faster relaxation dynamics in comparison to its bulk counterpart, and it further gets accelerated with reduction in the confining volume. Our combined results imply that the properties of confining boundary strongly influence the dynamics of the enclosed material.