Douglas L. Gin

Room-Temperature Ionic Liquids and Composite Materials: Platform Technologies for CO2 Capture

Clean energy production has become one of the most prominent global issues of the early 21st century, prompting social, economic, and scientific debates regarding energy usage, energy sources, and sustainable energy strategies. The reduction of greenhouse gas emissions, specifically carbon dioxide (CO(2)), figures prominently in the discussions on the future of global energy policy. Billions of tons of annual CO(2) emissions are the direct result of fossil fuel combustion to generate electricity. Producing clean energy from abundant sources such as coal will require a massive infrastructure and highly efficient capture technologies to curb CO(2) emissions. Current technologies for CO(2) removal from other gases, such as those used in natural gas sweetening, are also capable of capturing CO(2) from power plant emissions. Aqueous amine processes are found in the vast majority of natural gas sweetening operations in the United States. However, conventional aqueous amine processes are highly energy intensive; their implementation for postcombustion CO(2) capture from power plant emissions would drastically cut plant output and efficiency. Membranes, another technology used in natural gas sweetening, have been proposed as an alternative mechanism for CO(2) capture from flue gas. Although membranes offer a potentially less energy-intensive approach, their development and industrial implementation lags far behind that of amine processes. Thus, to minimize the impact of postcombustion CO(2) capture on the economics of energy production, advances are needed in both of these areas. In this Account, we review our recent research devoted to absorptive processes and membranes. Specifically, we have explored the use of room-temperature ionic liquids (RTILs) in absorptive and membrane technologies for CO(2) capture. RTILs present a highly versatile and tunable platform for the development of new processes and materials aimed at the capture of CO(2) from power plant flue gas and in natural gas sweetening. The desirable properties of RTIL solvents, such as negligible vapor pressures, thermal stability, and a large liquid range, make them interesting candidates as new materials in well-known CO(2) capture processes. Here, we focus on the use of RTILs (1) as absorbents, including in combination with amines, and (2) in the design of polymer membranes. RTIL amine solvents have many potential advantages over aqueous amines, and the versatile chemistry of imidazolium-based RTILs also allows for the generation of new types of CO(2)-selective polymer membranes. RTIL and RTIL-based composites can compete with, or improve upon, current technologies. Moreover, owing to our experience in this area, we are developing new imidazolium-based polymer architectures and thermotropic and lyotropic liquid crystals as highly tailorable materials based on and capable of interacting with RTILs.

Designing the Next Generation of Chemical Separation Membranes

New materials can be prepared as membranes that may allow their performance to beat long-standing limits. Synthetic membranes are used in many separation processes, from industrial-scale ones—such as separating atmospheric gases for medical and industrial use, and removing salt from seawater—to smaller-scale processes in chemical synthesis and purification. Membranes are commonly solid materials, such as polymers, that have good mechanical stability and can be readily processed into high–surface area, defect-free, thin films. These features are critical for obtaining not only good chemical separation but also high throughput. Membrane-based chemical separations can have advantages over other methods—they can take less energy than distillation or liquefaction, use less space than absorbent materials, and operate in a continuous mode. In some cases, such as CO2 separations for CO2 capture, their performance must be improved. We discuss how membranes work, and some notable new approaches for improving their performance.

Ending Aging in Super Glassy Polymer Membranes

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.

New Type of Li Ion Conductor with 3D Interconnected Nanopores via Polymerization of a Liquid Organic Electrolyte-Filled Lyotropic Liquid-Crystal Assembly

A new type of polymer electrolyte material for Li ion transport has been developed. This material is based on a polymerizable lyotropic (i.e., amphiphilic) liquid crystal (1) that forms a type-II bicontinuous cubic (Q(II)) phase with the common liquid electrolyte, propylene carbonate (PC), and its Li salt solutions. The resulting cross-linked, solid-liquid nanocomposite has an ordered, three-dimensional interconnected network of phase-separated liquid PC nanochannels and exhibits a room-temperature ion conductivity of 10(-4) to 10(-3) S cm(-1) when formed with 15 wt % 0.245 M LiClO(4)-PC solution. This value approaches that of conventional gelled poly(ethylene oxide)-based electrolytes blended with larger amounts of higher-concentration Li salt solutions. It is also similar to that of a bulk 0.245 M LiClO(4)-PC solution measured using the same AC impedance methods. Preliminary variable-temperature ion conductivity and NMR DOSY studies showed that liquidlike diffusion is present in the Q(II) nanochannels and that good ion conductivity ( approximately 10(-4) S cm(-1)) and PC mobility are retained down to -35 degrees C (and lower). This type of stable, liquidlike ion conductivity over a broad temperature range is typically not exhibited by conventional gelled-polymer- or liquid-crystal-based electrolytes, making this new material potentially valuable for enabling Li ion batteries that can operate more efficiently over a wider temperature range.

Scalable fabrication of polymer membranes with vertically aligned 1 nm pores by magnetic field directed self-Assembly

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.

Functional Lyotropic Liquid Crystal Materials

Lyotropic liquid crystals (LLCs) are amphiphilic molecules that have the ability to self-organize into highly ordered yet fluid, phase-segregated assemblies in the presence of an added polar liquid such as water. The resulting ordered assemblies, called LLC phases, have specific nanometer-scale geometries with periodic hydrophilic and hydrophobic features ranging in structure from bilayer lamellae to extended and interconnected channel systems. Because of their highly uniform, porous nanoscale structures, LLC phases and LLC-based materials have been proposed for use in a number of materials applications. However, only during the last two decades have LLC materials with functional properties and demonstrated applications of LLC systems been realized. This work provides an overview of functional LLC materials and the areas of application where they have made an impact. As new functional properties and capabilities are realized in LLC materials, it is almost certain that they will play more prevalent roles in nanoscience and nanotechnology in the near future.

Nanostructured materials based on polymerizable amphiphiles

Over the past 2 years, significant advances have been made in the development of nanostructured materials based on the polymerization of amphiphilic assemblies. The most notable advances include the synthesis of new nanostructured composite materials, demonstration of enhanced mechanical properties and catalytic reactivity in these systems, and a better understanding of the polymerization dynamics in these ordered assemblies. We expect this field to grow in the coming years, as it is one of the few simple, reliable routes towards nanoengineering and nanotechnology.

HETEROGENEOUS CATALYSIS WITH CROSS-LINKED LYOTROPIC LIQUID CRYSTAL ASSEMBLIES : ORGANIC ANALOGUES TO ZEOLITES AND MESOPOROUS SIEVES

Organic, nanoporous heterogeneous catalysts based on a carboxylate-containing, amphiphilic mesogen catalyze the Knoevenagel condensation (see schematic representation). These networks maintain their order in solution and can be recycled. Enhanced basicity, excellent site accessibility, and substrate size exclusion are features of these nanostructured systems.

Thermotropic liquid crystal behaviour of gemini imidazolium-based ionic amphiphiles

Thermotropic ionic liquid crystals (LCs) are useful for a number of applications such as anisotropic ion transport and as organised reaction media/solvents because of their ordered fluid properties and intrinsic charge units. A large number of different ionic LC architectures are known, but only a handful of examples of gemini (i.e. paired or dimeric) ionic LCs have been prepared and studied. In this work, a series of 20 new symmetric, imidazolium-based, gemini cationic LCs containing two bridged imidazolium cations and two pendant alkyl chains was synthesised, and the thermotropic LC behaviours were characterised. The imidazolium unit provides a highly tunable and modular platform for the design and synthesis of gemini cationic LCs which offers excellent structure control. As expected, the thermotropic LC properties of these new amphilphilic, gemini ionic LCs were found to be strongly influenced by the length of the spacer between the imidazolium units, the length of the pendant alkyl tails, and the nature of the anion. Smectic A (SmA) thermotropic LC phases were observed in more than half of the gemini imidazolium LC systems studied.

A systematic review of the management and outcome of toxic epidermal necrolysis treated in burns centres

INTRODUCTION Toxic epidermal necrolysis (TEN) is a rare condition characterised by mucocutaneous exfoliation of greater than 30% total body surface area (%TBSA), increasingly being treated in burns centres. The rate of mortality varies significantly in the literature, with recent prospective studies in non-burns centres reporting percentage mortality of approximately 45%. We undertook a systematic review of published studies that included TEN patients treated specifically in burns centres to determine a cumulative mortality rate. METHODS Electronic searches of MEDLINE, EMBASE and The Cochrane Library (Issue 4, 2010) databases from 1966 onwards were used to identify English articles related to the treatment of TEN in burns centres. RESULTS The systematic literature search identified 20 studies which specifically described patients with TEN grater than 30% %TBSA. Treatment regimens varied amongst studies, as did mortality. The overall percentage mortality of the combined populations was 30%. Risk factors commonly described as associated with mortality included age, %TBSA and delay to definitive treatment. CONCLUSION The review highlights the variation between principles of treatment and mortality amongst burns centres. It offers a standard that burns centre can use to internationally compare their mortality rates. The review supports the ongoing reporting of outcomes in TEN patients with epidermal detachment greater than 30%.