(524g) Computational Characterization of Ultrathin Amorphous Polymer Films in Liquids

Polymer materials have a wide variety of important applications in chemical processes. The ability to accurately predict the fundamental properties of polymers is the key to their optimization and rational design of new polymers. In this study, the material properties of an amorphous polymer in liquids are computationally characterized from a molecular perspective. In order to achieve this objective, molecular simulations and defined characteristic lengths are integrated to analyse the dynamic and equilibrium properties of amorphous polymer in liquids. The polymer of intrinsic microporosity (PIM-1) is used as an illustrative polymer as it has shown great potential in various gas and liquid separations. Molecular simulations of PIM-1 swelling in liquids such as organic solvents and water are explored. Solvent-induced swelling of PIM-1 is observed in organic solvents while the polymer structure remains intact in water. In view of the glassy nature of PIM-1, the polymer swelling is attributed to both solvent occupation of free volume and dilation of polymer matrix. With defined characteristic lengths, swelling process has been validated against a predictive model. In addition, gravimetric swelling degree of PIM-1 in solvents and their correlation with solubility parameters are in good agreement with experimental findings. Detailed analyses on the equilibrium structures of swollen PIM-1 offer further molecular insights. Lastly, the performance of PIM-1 as membrane material in seawater is assessed through the same characterization procedure. This study illustrates the usefulness of the characterization procedure in estimating material properties of PIM-1 in liquids. This procedure can potentially be applied to other polymers in liquids to gain fundamental understanding of their performances as membranes in liquid separations such as reverse osmosis and organic solvent nanofiltration.