can distinguish sorption-driven or kinetics-driven separation. Colloquially speaking, sorption-driven separation exploits different levels of affinity of the components of the mixture towards the polymer material. Higher concentration of the stronger binding component in the membrane should lead to a higher flux of this component across the membrane, and, hence, the permeate stream should be enriched in this component. Conversely, kinetics-driven separation can be thought of as a sieving mechanism that discriminates between species based on their molecular size and the resulting free energy barriers to cross narrow windows in the polymer structure. In the kinetics-driven separations, the permeate product should be enriched in the component with a smaller molecular size. This component is also expected to have weaker interactions with the polymer material compared to the component with larger molecular size.