(181y) Multicomponent Transport in Hydrated Dense Polymer Membranes: Impact of Varied Fractional Free Volume

Membranes are utilized for a wide variety of applications due to their low carbon footprint, low energy requirement and ability to transport molecules selectively. To determine transport through a membrane (membrane permeability), a diffusion cell apparatus is used to quantify solute flux. The downstream solution must be characterized to determine the amount of solute contained, and, traditionally, aliquotic sampling was utilized to characterize ex situ which causes constantly changing downstream volume, hydrostatic pressure issues and very difficult calculations. Alternatively, in-situ single component experiments have been performed to quantify permeabilities and ideal selectivities, which is the general procedure for selecting a membrane for a process. In this work, in-situ attenuated total reflectance Fourier-transform infrared (ATR FTIR) spectroscopy quantifies multiple component concentrations in the downstream volume over time without the need for aliquotic sampling. Poly(ethylene glycol) diactrylate (PEGDA) membranes were synthesized with varying amounts of water in the pre-crosslinked mixture to vary the amount of fractional free volume within the membranes. These membranes were tested for the permeability and solubility of ethanol, methanol and sodium acetate, and from these experiments, the diffusivities were determined via the solution diffusion model (P_i = K_i x D_i where P_i is the permeability, K_i is the thermodynamic solubility and D_i is the kinetic diffusivity). Permeabilities varied from single to multicomponent experiments due to solute-solute and multiple solute-membrane interactions and these changes are shown to be kinetically or thermodynamically driven. In the end, these interactions severely impact membrane behavior which indicates that these multicomponent permeability experiments are vital when selecting a membrane for a process.