(646e) Molecular Design of Polymeric Membranes with Tunable Gradient Pores for Organic Solvent Nanofiltration

Organic solvent nanofiltration (OSN) is a robust separation technology for the recovery of organic solvents in the chemical and pharmaceutical industries. A handful of polymeric membranes have been tested for OSN; the pore size and pore size distribution are found to play a key role in membrane performance. Recently, there is increasing interest to develop membranes with gradient pores for separation, which however has not been realized for OSN membranes. Based on molecular simulations, we propose a strategy to computationally design polymer membranes with gradient pores by merging a series of layers of polymers with different chain lengths, and examine their performance for OSN. To illustrate, the polybenzimidazole (PBI) and polymer of intrinsic microporosity (PIM-1) membranes are constructed. For each membrane, the density, pore size distribution, swelling behavior are examined. Compared with the layer composed of shorter chains, the layer of longer chains possesses a lower density, larger pores and a higher swelling degree, thus offering more free volume for permeation. This computational study provides a proof-of-concept study to assess the effects of gradient pores on membrane structures and properties, and suggests that the pore sizes can be tuned via adjusting chain length to develop high-performance OSN membranes.