LAUSR

Significance Activated penetrant diffusion in molecular and polymeric normal and supercooled liquids is of fundamental scientific interest and critical to control for materials applications, such as membrane separations, barrier coatings, drug delivery, and self-healing. How the rich chemical complexity associated with molecular and monomer shape, size, interactions, and conformational flexibility impacts transport is poorly understood. Here, we provide direct experimental support for diverse chemical systems of the novel theoretical prediction that activated transport is controlled by two key factors, matrix thermodynamic dimensionless compressibility and penetrant-to-matrix species size ratio. This finding reveals an unexpected high degree of self-averaging of angstrom-scale features and provides new guidelines for the selection of specific matrices and temperature to achieve a targeted rate of penetrant mass transport.