ABSTRACT
A nanoporous, bicontinuous cubic, lyotropic liquid crystal polymer resin with sulfonic acid groups is presented that exhibits high catalytic activity and is capable of molecular-size-selective heterogeneous acid catalysis.
ABSTRACT
Correction for 'Cross-linkable, phosphobetaine-based, zwitterionic amphiphiles that form lyotropic bicontinuous cubic phases' by Lauren N. Bodkin et al., Soft Matter, 2023, 19, 3768-3772, https://doi.org/10.1039/D3SM00269A.
ABSTRACT
The design, synthesis, and lyotropic liquid crystal phase behaviour of six cross-linkable, phosphobetaine-based, zwitterionic amphiphiles are described. Two form a QII phase with aq. NH4Cl solution, giving 3D-nanoporous membrane materials that can be used for water desalination and are not susceptible to ion exchange like traditional ionic analogues.
ABSTRACT
A single-head/single-tail surfactant with a polymerizable group at each end is presented as a new simplified motif for intrinsically cross-linkable, gyroid-phase lyotropic mesogens. The resulting nanoporous polymer networks exhibit excellent structural stability in various solvents and are capable of molecular size discrimination.
ABSTRACT
Seven homologues of an amphiphilic gemini monomer were synthesized and screened for the ability to form a bicontinuous cubic (Q) lyotropic liquid crystal phase. Four of these homologues form a Q phase with glycerol or water that can be cross-linked with retention of the nanoporous structure, with one exhibiting a well-ordered Q phase with a wider phase window than the parent monomer.
ABSTRACT
Direct, living ring-opening metathesis polymerization of a highly paramagnetic, norbornene-based imidazolium FeCl4- ionic liquid monomer was achieved using the Grubbs third-generation catalyst and starting the polymerization off with an uncharged, nonparamagnetic norbornene monomer in a sequential block copolymerization. Preparing the paramagnetic norbornene imidazolium FeCl4- monomer in high purity was found to be crucial for enabling living polymerization behavior and generating paramagnetic diblock copolymers with predictable block lengths and compositions.
ABSTRACT
Creating well-defined single-crystal textures in materials requires the biaxial alignment of all grains into desired orientations, which is challenging to achieve in soft materials. Here we report the formation of single crystals with rigorously controlled texture over macroscopic areas (>1 cm2) in a soft mesophase of a columnar discotic liquid crystal. We use two modes of directed self-assembly, physical confinement and magnetic fields, to achieve control of the orientations of the columnar axes and the hexagonal lattice along orthogonal directions. Field control of the lattice orientation emerges in a low-temperature phase of tilted discogens that breaks the field degeneracy around the columnar axis present in non-tilted states. Conversely, column orientation is controlled by physical confinement and the resulting imposition of homeotropic anchoring at bounding surfaces. These results extend our understanding of molecular organization in tilted systems and may enable the development of a range of new materials for distinct applications.
ABSTRACT
Periodic, nanostructured porous polymer membranes made from the cross-linked inverted hexagonal phase of self-assembled lyotropic liquid crystals (LLCs) are a promising class of materials for selective separations. In this work, we investigate an experimentally characterized LLC polymer membrane using atomistic molecular modeling. In particular, we compare simulated X-ray diffraction (XRD) patterns with experimental XRD data to quantify and understand the differences between simulation and experiment. We find that the nanopores are likely composed of five columns of stacked LLC monomers which surround each hydrophilic core. Evidence suggests that these columns likely move independently of each other over longer time scales than accessible via atomistic simulation. We also find that wide-angle X-ray scattering structural features previously attributed to monomer tail tilt are likely instead due to ordered tail packing. Although this system has been reported as dry, we show that small amounts of water are necessary to reproduce all features from the experimental XRD pattern because of asymmetries introduced by hydrogen bonds between the monomer head groups and water molecules. Finally, we explore the composition and structure of the nanopores and reveal that there exists a composition gradient rather than an abrupt partition between the hydrophilic and hydrophobic regions. A caveat is that the time scales of the dynamics are extremely long for this system, resulting in simulated structures that appear too ordered, thus requiring careful examination of the metastable states observed in order to draw any conclusions. The clear picture of the nanoscopic structure of these membranes provided in this study will enable a better understanding of the mechanisms of small-molecule transport within these nanopores.
ABSTRACT
An ordered, nanoporous, TEMPO-based polymer resin formed from lyotropic liquid crystal monomers catalyzes the hetereogeneous oxidation of alcohols with high activity and substrate size selectivity under transition-metal-free, aerobic conditions.
ABSTRACT
A new type of poly(ionic liquid) membrane, which shows switchable hydrated states via lower critical solution temperature-type phase behaviour, enables concentration of some water-soluble proteins from aqueous media.
Subject(s)
Cytochromes c/analysis , Horseradish Peroxidase/analysis , Ionic Liquids/chemistry , Myoglobin/analysis , Polymers/chemistry , Temperature , Animals , Horseradish Peroxidase/metabolism , Horses , Molecular Structure , Water/chemistryABSTRACT
Ionic liquid (IL)-based ion-gel membranes were prepared from a curable poly(IL)-based materials platform with the free ILs 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), bis(fluorosulfonyl)imide ([EMIM][FSI]), 1-butylimidazolium bis(trifluoromethylsulfonyl)imide ([C4 IMH][TFSI]), and ethylmethylammonium nitrate [EAN][NO3 ] and evaluated for their ionic conductivity performance at ambient and elevated temperatures. The resulting cross-linked, free-standing ion-gel membranes were found to have less than 1 wt% water (with the exception of [EAN][NO3 ] which contained ≈20 wt% water). Increasing free IL content from 50 to 80 wt% produces materials with ionic conductivity values ≥10(-2) S cm(-1) at 25 °C and ≈10(-1) S cm(-1) at 110 °C. Additionally, ion-gels containing 70 wt% of the protic ILs [C4 IMH][TFSI] and [EMIM][FSI] display ionic conductivity values of ≈10(-3) to 10(-2) S cm(-1) over the temperature range of 25-110 °C.
Subject(s)
Cross-Linking Reagents/chemistry , Imidazoles/chemistry , Ionic Liquids/chemistry , Polymers/chemistry , Cross-Linking Reagents/chemical synthesis , Electric Conductivity , Gels/chemical synthesis , Gels/chemistry , Molecular Structure , Polymers/chemical synthesis , TemperatureABSTRACT
The recycling or sequestration of carbon dioxide (CO2) from the waste gas of fossil-fuel power plants is widely acknowledged as one of the most realistic strategies for delaying or avoiding the severest environmental, economic, political, and social consequences that will result from global climate change and ocean acidification. For context, in 2013 coal and natural gas power plants accounted for roughly 31% of total U.S. CO2 emissions. Recycling or sequestering this CO2 would reduce U.S. emissions by ca. 1800 million metric tons-easily meeting the U.S.'s currently stated CO2 reduction targets of ca. 17% relative to 2005 levels by 2020. This situation is similar for many developed and developing nations, many of which officially target a 20% reduction relative to 1990 baseline levels by 2020. To make CO2 recycling or sequestration processes technologically and economically viable, the CO2 must first be separated from the rest of the waste gas mixture-which is comprised mostly of nitrogen gas and water (ca. 85%). Of the many potential separation technologies available, membrane technology is particularly attractive due to its low energy operating cost, low maintenance, smaller equipment footprint, and relatively facile retrofit integration with existing power plant designs. From a techno-economic standpoint, the separation of CO2 from flue gas requires membranes that can process extremely high amounts of CO2 over a short time period, a property defined as the membrane "permeance". In contrast, the membrane's CO2/N2 selectivity has only a minor effect on the overall cost of some separation processes once a threshold permeability selectivity of ca. 20 is reached. Given the above criteria, the critical properties when developing membrane materials for postcombustion CO2 separation are CO2 permeability (i.e., the rate of CO2 transport normalized to the material thickness), a reasonable CO2/N2 selectivity (≥20), and the ability to be processed into defect-free thin-films (ca. 100-nm-thick active layer). Traditional polymeric membrane materials are limited by a trade-off between permeability and selectivity empirically described by the "Robeson upper bound"-placing the desired membrane properties beyond reach. Therefore, the investigation of advanced and composite materials that can overcome the limitations of traditional polymeric materials is the focus of significant academic and industrial research. In particular, there has been substantial work on ionic-liquid (IL)-based materials due to their gas transport properties. This review provides an overview of our collaborative work on developing poly(ionic liquid)/ionic liquid (PIL/IL) ion-gel membrane technology. We detail developmental work on the preparation of PIL/IL composites and describe how this chemical technology was adapted to allow the roll-to-roll processing and preparation of membranes with defect-free active layers ca. 100 nm thick, CO2 permeances of over 6000 GPU, and CO2/N2 selectivity of ≥20-properties with the potential to reduce the cost of CO2 removal from coal-fired power plant flue gas to ca. $15 per ton of CO2 captured. Additionally, we examine the materials developments that have produced advanced PIL/IL composite membranes. These advancements include cross-linked PIL/IL blends, step-growth PIL/IL networks with facilitated transport groups, and PIL/IL composites with microporous additives for CO2/CH4 separations.
ABSTRACT
Membrane separations are critically important in areas ranging from health care and analytical chemistry to bioprocessing and water purification. An ideal nanoporous membrane would consist of a thin film with physically continuous and vertically aligned nanopores and would display a narrow distribution of pore sizes. However, the current state of the art departs considerably from this ideal and is beset by intrinsic trade-offs between permeability and selectivity. We demonstrate an effective and scalable method to fabricate polymer films with ideal membrane morphologies consisting of submicron thickness films with physically continuous and vertically aligned 1 nm pores. The approach is based on soft confinement to control the orientation of a cross-linkable mesophase in which the pores are produced by self-assembly. The scalability, exceptional ease of fabrication, and potential to create a new class of nanofiltration membranes stand out as compelling aspects.
ABSTRACT
We demonstrate that an ether-based n-alkoxy-2,4-hexadiene polymerizable tail system is an effective and modular alternative to traditional ester-based polymerizable tail groups (i.e., acrylate, methacrylate, sorbate) and alkyl-1,3-diene tails for the design of radically polymerized ionic liquid crystal (ILC) monomers. Several series of nonsymmetric 1-vinylimidazolium-bromide-based ILC monomers containing these different polymerizable tail systems were synthesized and compared for their ability to form thermotropic liquid crystal (TLC) phases and to be photo-cross-linked with TLC phase retention. The n-alkoxy-2,4-hexadiene tail system was found to be more favorable/conducive to TLC phase formation than acrylate, methacrylate, and sorbate tails. It was more similar to the alkyl-1,3-diene tail system in terms of its more favorable effect on TLC behavior; however, it is more modular/easier to synthesize, more resistant to thermal Diels-Alder side reaction, and more isomerically pure, making it better for ILC monomer design. Also, the n-alkoxy-2,4-hexadiene tail system was found to be very amenable to radical photo-cross-linking with TLC phase retention. To demonstrate this feature, an example cross-linkable ILC monomer with this tail system was synthesized and polymerized in the smectic A TLC phase, and the monomer and polymerized material were characterized for their ionic conductivity behavior.
ABSTRACT
Following removal of coordinated CH3 CN, the resulting complexes [Ag(I) (2,2'-bipyridine)][BF4 ] (1) and [Ag(I) (6,6'-dimethyl-2,2'-bipyridine)][OTf] (2) show ethene/ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18â mmol g(-1) when tested at an applied gas pressure of 90â kPa and a temperature of (20±1) °C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2, ethene sorption reached 90 % of equilibrium capacity within 15â minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes.
ABSTRACT
There is long-standing interest in developing membranes possessing uniform pores with dimensions in the range of 1 nm and physical continuity in the macroscopic transport direction to meet the needs of challenging small molecule and ionic separations. Here we report facile, scalabe fabrication of polymer membranes with vertically (i.e., along the through-plane direction) aligned 1 nm pores by magnetic-field alignment and subsequent cross-linking of a liquid crystalline mesophase. We utilize a wedge-shaped amphiphilic species as the building block of a thermotropic columnar mesophase with 1 nm ionic nanochannels, and leverage the magnetic anisotropy of the amphiphile to control the alignment of these pores with a magnetic field. In situ X-ray scattering and subsequent optical microscopy reveal the formation of highly ordered nanostructured mesophases and cross-linked polymer films with orientational order parameters of ca. 0.95. High-resolution transmission electron microscopy (TEM) imaging provides direct visualization of long-range persistence of vertically aligned, hexagonally packed nanopores in unprecedented detail, demonstrating high-fidelity retention of structure and alignment after photo-cross-linking. Ionic conductivity measurements on the aligned membranes show a remarkable 85-fold enhancement of conductivity over nonaligned samples. These results provide a path to achieving the large area control of morphology and related enhancement of properties required for high-performance membranes and other applications.
ABSTRACT
A metal-containing ionic liquid (MCIL) has been prepared in which the [Co(II)(salicylate)2](2-) anion is able to selectively coordinate two water molecules with a visible colour change, even in the presence of alcohols. Upon moderate heating or placement in vacuo, the hydrated MCIL undergoes reversible thermochromism by releasing the bound water molecules.
Subject(s)
Cobalt/chemistry , Coordination Complexes/chemistry , Ionic Liquids/chemistry , Salicylates/chemistry , Water/chemistry , Models, Molecular , Molecular Structure , TemperatureABSTRACT
Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.
ABSTRACT
New ionic amphiphiles with a hexyl-bridged bis(imidazolium) headgroup; Br(-), BF4(-), or Tf2N(-) anions; and a long n-alkyl tail can form thermotropic bicontinuous cubic liquid crystal phases in neat form and/or lyotropic bicontinuous cubic phases with several non-aqueous solvents or water.
