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Membrane technologies can offer dramatically higher energy efficiency than thermally driven separations such as distillation. The fabrication of robust, solvent-stable active layers on inexpensive supports is essential for the widespread utilization of this technology by industry. Here we show that polymer membranes incorporating a perfluoroalkyl side chain onto a hydrocarbon backbone provide remarkable enhancements in performance and stability in the dehydration of ethanol by pervaporation, even surpassing commercial perfluoropolymers. To rapidly generate these robust thin film composite membranes, we use a method termed spin coating ring-opening metathesis polymerization (scROMP) that combines the polymerization and deposition of the membrane selective layer into a 2-min process with under 1 mL of solvent per 36 cm2 of polymer. Here, the scROMP of 5- (perfluoro-n-alkyl)norbornenes (NBFn) with perfluoroalkyl side chain lengths (n) of 4, 6, 8, and 10 is used to generate semifluorinated films on polyacrylonitrile (PAN) supports. pNBFn membranes exhibit greater solvent stability than their nonfluorinated polynorbornene (pNB; n =0) counterpart while retaining excellent thermal stability, as evidenced by reduced swelling in polar and nonpolar solvents and <1 % mass loss in thermogravimetric analysis up to 130 ◦C. Molecular simulations show that the fluorocarbon side chains orient parallel to the surface in the bulk but more normal to the surface at the interface, consistent with experimental IR spectroscopy and wetting measurements. Of the polymers studied, pNBF8 shows the greatest performance in ethanol dehydration, obtaining a selectivity of 180 and a water permeance of 1000 GPU, while sustaining high performance for >40 h of continuous operation. 

Functionalized alkylsilane films exhibit switching interfacial behavior in response to different solvents. Image shows exposed oxygen (red) and carbon atoms (green). Hydroxyl films switch more favorably than carboxyl counterparts. 

Monolayer films have shown promise as a lubricating layer to reduce friction and wear of mechanical devices with separations on the nanoscale. These films have a vast design space with many tunable properties that can affect their tribological effectiveness. For example, terminal group chemistry, film composition, and backbone chemistry can all lead to films with significantly different tribological properties. This design space, however, is very difficult to explore without a combinatorial approach and an automatable, reproducible, and extensible workflow to screen for promising candidate films. Using the Molecular Simulation Design Framework (MoSDeF), a combinatorial screening study was performed to explore 9747 unique monolayer films (116 964 total simulations) and a machine learning (ML) model using a random forest regressor, an ensemble learning technique, to explore the role of terminal group chemistry and its effect on tribological effectiveness. The most promising films were found to contain small terminal groups such as cyano and ethylene. The ML model was subsequently applied to screen terminal group candidates identified from the ChEMBL small molecule library. Approximately 193 131 unique film candidates were screened with approximately a five order of magnitude speed-up in analysis compared to simulation alone. The ML model was thus able to be used as a predictive tool to greatly speed up the initial screening of promising candidate films for future simulation studies, suggesting that computational screening in combination with ML can greatly increase the throughput in combinatorial approaches to generate in silico data and then train ML models in a controlled, self-consistent fashion. 

Cross-linked chemisorbed n-alkylsilane (CH3(CH2)n−1Si(OH)3) monolayers on amorphous silica surfaces have been studied and their structural properties and frictional performance were compared to those of equivalent monolayers without cross-linkages. The simulations isolated for the first time the effects of both siloxane cross-linkages and the fraction of chains chemisorbed to the surface, providing insight into a longstanding fundamental question in the literature regarding molecular-level structure. The results demonstrate that both cross-linkages and the fraction of chemisorbed chains affect monolayer structure in small but measurable ways, particularly for monolayers constructed from short chains; however, these changes do not appear to have a significant impact on frictional performance.