Polyimides and ionic liquids (ILs) are two classes of materials that have been widely studied as gas separation membranes, each demonstrating respective advantages and limitations. Both polyimides and ILs are amenable to modification/functionalization based on selection of the requisite precursors. However, there have been but a handful of reports considering how polyimides and ILs could be integrated to obtain fundamentally new materials with synergistic properties. In this manuscript, we demonstrate a new and versatile way to synthesize polyimides with imidazolium cations directly located within the polymer backbone to form polyimide−ionene hybrids, or "ionic polyimides". Our strategy for synthesizing ionic polyimides does not require the use of amino-functionalized ILs. Instead, the imidization reaction occurs prior to polymerization in the formation of an imidazole-functionalized diimide monomer. This monomer is then reacted via step-growth (condensation) polymerization with p-dichloroxylene via Menshutkin reactions, simultaneously linking the monomers and creating the ionic components. The resultant ionic polyimide is amenable to thermal processing (e.g., extrusion, melt-pressing) and capable of forming thin films. Upon soaking thin films of the ionic polyimide in a widely used IL, 1butyl-3-methylimidazolium bistriflimide ([C 4 mim][Tf 2 N]), a stoichiometric absorption of the IL into the ionic polyimide was observed, forming an ionic polyimide + IL composite. The gas separation performances of ionic polyimide and ionic polyimide + IL composite membranes were studied with respect to CO 2 , N 2 , CH 4 , and H 2 . The neat ionic polyimide exhibits low permeability to CO 2 and H 2 (∼0.9 and ∼1.6 barrers, respectively) and very low permeability to N 2 and CH 4 (∼0.03 barrers for both). For the ionic polyimide + IL composite, the permeabilities of CO 2 , N 2 , and CH 4 increase by 1800−2700%, while H 2 permeability only increased by ∼200%. The large increases in permeability for CO 2 , N 2 , and CH 4 are due to greatly increased gas diffusivity through the material, with gas solubility essentially unchanged with the IL present. The ionic polyimide and ionic polyimide + IL composite were characterized using a number of techniques. Most interestingly, X-ray diffractometry (XRD) of the films reveals that the ionic polyimide + IL composite displays a sharp peak, indicating that the ionic polyimide may experience supramolecular assembly around the IL. Although the performances of these first ionic polyimide and ionic polyimide + IL composite membranes fall short of Robeson's Upper Bounds, this work provides a strong foundation on which ionic polyimide materials with more sophisticated structural elements can be developed to understand the structure−property relationships underlying the ionic polyimide platform and ultimately produce high-performance gas separation membranes.

1,2,3-Trimethoxypropane (1,2,3-TMP) is the trimethyl ether of propane-1,2,3-triol, better known as glycerol, which can be derived from triglycerides originating from either plant or animal sources. Despite its simple structure and the ubiquity of its glycerol precursor, successful synthesis of 1,2,3-TMP was only recently reported in the literature, with studies suggesting it may be a "green" and nontoxic alternative to solvents such as diglyme, a constitutional isomer. However, no thermophysical properties of 1,2,3-TMP have yet been reported. Furthermore, the structure of 1,2,3-TMP is also analogous to polyether solvents used in the Selexol process for removal of CO 2 and other "acid" gases from CH 4 , H 2 , etc. As such, examining the solubility of CO 2 in 1,2,3-TMP is also of interest. This work details our initial studies and characterization of 1,2,3-TMP as a physical solvent for CO 2 absorption, as well as the characterization of its density, viscosity, and vapor pressure with respect to temperature. 1,2,3-TMP exhibits favorable properties, and glycerol-derived triethers warrant deeper consideration as new solvents for CO 2 absorption and other gas treating applications.

Abstract:The manipulation of particulates in microfluidics is a challenge that continues to impact applications ranging from fine chemicals manufacturing to the materials and the life sciences. Heterogeneous operations carried out in microreactors involve high surface-to-volume characteristics that minimize the heat and mass transport resistances, offering precise control of the reaction conditions. Considerable advances have been made towards the engineering of techniques that control particles in microscale laminar flow, yet there remain tremendous opportunities for improvements in the area of chemical processing. Strategies that have been developed to successfully advance systems involving heterogeneous materials are reviewed and an outlook provided in the context of the challenges of continuous flow fine chemical processes.

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Etherification with high selectivity and yield has been one of the challenges for expanding the realm of glycerol transformations. In this work, a small glycerol triether molecule, 1,2,3-triethoxypropane (1,2,3-TEP, CAS 162614-45-1), was designed and synthesized through a two-step strategy using epichlorohydrin as the starting material with ethanol and bromoethane as etherification reagents. The overall yield (after rigorous distillation) was 43.9%, higher than those of methods previously published in the literature. Thermophysical properties for 1,2,3-TEP are herein reported for the first time. Densities and viscosities measured at 1 atm from 20 to 80 °C show that 1,2,3-TEP is a less dense and less viscous liquid than glycerol and the corresponding 1,3-diether intermediate, 1,3-diethoxypropan-2-ol (1,3-DEP, CAS #4043-59-8). CO 2 solubility in 1,2,3-TEP was investigated under pressures of 2−8 atm at 30, 45, 60, and 75 °C with respective K H values of 46.2, 57.4, 69.4, and 81.7 atm, enabling reliable predictions on CO 2 solubility within this range of temperature and pressure conditions. Comparison of Henry's law constants and vapor pressure between 1,2,3-TEP and diglyme from 0 to 75 °C has indicated its potential as an alternative CO 2 capture solvent to those used in the Selexol process. 1,2,3-TEP showed broad miscibility with common solvents except water. The dipole moment of the minimum energy structure in the gas phase is calculated to be 1.47 D, but this value increases to 2.5−2.7 D in common solvents. The data obtained in this work are meaningful in guiding the further synthesis of a series of glycerol triether derivatives and developing uses for 1,2,3-TEP and related compounds.