Far-from-equilibrium thermodynamic systems that are established as a consequence of coupled equilibria are the origin of the complex behavior of biological systems. Therefore, research in supramolecular chemistry has recently been shifting emphasis from a thermodynamic standpoint to a kinetic one; however, control over the complex kinetic processes is still in its infancy. Herein, we report our attempt to control the time evolution of supramolecular assembly in a process in which the supramolecular assembly transforms from a J-aggregate to an H-aggregate over time. The transformation proceeds through a delicate interplay of these two aggregation pathways. We have succeeded in modulating the energy landscape of the respective aggregates by a rational molecular design. On the basis of this understanding of the energy landscape, programming of the time evolution was achieved through adjusting the balance between the coupled equilibria.

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Rising atmospheric CO2 levels have triggered recent research into the science of amine materials supported on hard, porous materials such as mesoporous silica or alumina. While such materials can give high CO2 uptakes and good sorption kinetics, they are difficult to utilize in practical applications due to difficulty in contacting large volumes of CO2-laden gases with powder materials without significant pressure drops or sorbent attrition. Here, we describe a simple approach based on the impregnation of a permanently microporous polymer, PIM-1, with poly­(ethylene imine) (PEI), removing the need for use of the hard oxide. PEI/PIM-1 composites demonstrate comparable performance to more traditionally studied oxide sorbents, with the benefit that PIM-1 is soluble in common solvents, making it eminently more viable for processing into morphologies that can facilitate heat and mass transfer and fabrication into low pressure drop contactors. In addition to adsorption studies performed on a variety of PEI/PIM-1 architectures, spin diffusion NMR studies were performed to suggest that PEI is well-dispersed within the PIM-1, allowing for rapid CO2 adsorption.

The combination of appreciable swelling at unit activity sorption, weak polymer−penetrant interactions, and high vapor pressure allows methanol to be effective at restoring free volume to glassy polymers compared to similar organics. Polymers of intrinsic microporosity (PIMs) are often soaked in methanol and then dried before permeation and sorption analysis to improve reproducibility and eliminate processing history. Here, surface area, pore volume, thermogravimetric analysis, sorption, and diffusion data are used to demonstrate the effectiveness of methanol treatments at removing nonsolvent-induced changes to PIM-1, specifically using dimethylformamide (DMF) as a candidate conditioning molecule. DMF clearly plasticizes PIM-1 while methanol does not. In addition, diethyl ether-conditioned PIM-1 showed marked increases in surface area and free volume higher than that found from methanol conditioning. Strongly plasticizing nonsolvents with low vapor pressures can be used as conditioning agents that promote polymer relaxations, accelerate chain packing, and remove additional nonequilibrium free volume. ■ INTRODUCTIONMicroporous polymeric materials have attracted significant interest for a variety of potential molecular separation applications due to their combination of synthetic tunability and unusually facile processability in the case of linear polymers. The most well-studied linear microporous polymer, PIM-1 (polymer of intrinsic microporosity 1, shown in Figure 1), has a characteristic spirocenter between cyclopentane rings that hinders efficient chain packing. These 90°bends in the polymer chain impart "intrinsic" microporosity and high free volume that is uncommon for amorphous, solution processable polymers. As a result, PIM materials have high permeabilities with moderate selectivities that helped redefine the Robeson upper bounds for many of the commonly studied gas pairs. 1 As polymers are cooled below their glass transition temperature (T g ), they retain excess free volume between the chains due to nonequilibrium packing defects. The concentration and nature of these free volume elements have been successfully used to describe the sorption, diffusion, and permeation of guest molecules through glassy polymers. 2−4 However, high free volume glassy polymers such as PIMs are particularly susceptible to aging and conditioningthe loss of permeability and concomitant gain in selectivity with time. After membrane formation, PIM-1 naturally begins to lose some of its excess free volume due to slow relaxations of the polymer chains toward their equilibrium packing. Lau et al. have shown that the CO 2 permeability of PIM-1 decreases by 62% over a period of eight months storage at ambient conditions. 5 However, not all of the free volume was lost, and there remained intrinsic microporosity to the polymers even after a year under ambient storage. 6 Moreover, PIMs are unusual linear polymers because they do not exhibit a measurable T g before decomposition. 7 As a result, near-T g annealing techniques used to alt...

The electrosynthesis of value‐added multicarbon products from CO2 is a promising strategy to shift chemical production away from fossil fuels. Particularly important is the rational design of gas diffusion electrode (GDE) assemblies to react selectively, at scale, and at high rates. However, the understanding of the gas diffusion layer (GDL) in these assemblies is limited for the CO2 reduction reaction (CO2RR): particularly important, but incompletely understood, is how the GDL modulates product distributions of catalysts operating in high current density regimes > 300 mA cm−2. Here, 3D‐printable fluoropolymer GDLs with tunable microporosity and structure are reported and probe the effects of permeance, microstructural porosity, macrostructure, and surface morphology. Under a given choice of applied electrochemical potential and electrolyte, a 100× increase in the C2H4:CO ratio due to GDL surface morphology design over a homogeneously porous equivalent and a 1.8× increase in the C2H4 partial current density due to a pyramidal macrostructure are observed. These findings offer routes to improve CO2RR GDEs as a platform for 3D catalyst design.

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Carbon molecular sieve (CMS) membranes are candidates for the separation of organic molecules due to their stability, ability to be scaled at practical form factors, and the avoidance of expensive supports or complex multi‐step fabrication processes. A critical challenge is the creation of “mid‐range” (e.g., 5–9 Å) microstructures that allow for facile permeation of organic solvents and selection between similarly‐sized guest molecules. Here, we create these microstructures via the pyrolysis of a microporous polymer (PIM‐1) under low concentrations of hydrogen gas. The introduction of H2 inhibits aromatization of the decomposing polymer and ultimately results in the creation of a well‐defined bimodal pore network that exhibits an ultramicropore size of 5.1 Å. The H2 assisted CMS dense membranes show a dramatic increase in p‐xylene ideal permeability (≈15 times), with little loss in p‐xylene/o‐xylene selectivity (18.8 vs. 25.0) when compared to PIM‐1 membranes pyrolyzed under a pure argon atmosphere. This approach is successfully extended to hollow fiber membranes operating in organic solvent reverse osmosis mode, highlighting the potential of this approach to be translated from the laboratory to the field.

Stimuli-responsive materials offer new opportunities to resolve long-standing materials challenges and are rapidly gaining pivotal roles in diverse applications. For example, smart protective garments This article is protected by copyright. All rights reserved. 2 that rapidly transport water vapor and autonomously block chemical threats are expected to enable an effective new paradigm of adaptive personal protection. However, the incorporation of these seemingly incompatible properties into a single responsive system remains elusive. Herein, we demonstrate a bistable membrane that can rapidly, selectively, and reversibly transition from a highly breathable state in a safe environment to a chemically protective state when exposed to organophosphate threats such as sarin. Dynamic response to chemical stimuli is achieved through the physical collapse of an ultrathin copolymer layer on the membrane surface, which efficiently gates transport through membrane pores composed of single-walled carbon nanotubes (SWNT). The adoption of nanometer-wide SWNTs for ultrafast moisture conduction enables a simultaneous boost in size-sieving selectivity and water-vapor permeability by decreasing nanotube diameter, thereby overcoming the breathability/protection trade-off that limits conventional membrane materials.Adaptive multifunctional membranes based on this platform greatly extend the active use of a protective garment and present exciting opportunities in many other areas including separation processes, sensing, and smart delivery.