Douglas L. Gin

Functional Nanostructured Polymers Based on Liquid Crystal Building Blocks

One of the most important frontiers in materials chemistry is the architectural control of synthetic materials on the nanometer-scale (1 nm = one-billionth of a meter). Nanometer-scale architecture is primarily responsible for the impressive properties of many biological structural materials (e.g., bone) and the unique reactivity of many inorganic supercage catalysts (e.g., zeolites). Unfortunately, very few techniques for constructing man-made materials offer compositional or architectural control on this size regime. One of the principal questions that we are addressing is whether materials with unique or superior bulk properties can be generated if nanometer-scale architectural control could be achieved in organic materials and polymer design to enhance or generate new functional materials properties.

We have developed a successful research program directed at constructing functional materials with controlled nanostructures by designing self-organizing monomers based on thermotropic (i.e., temperature-dependent) and lyotropic (i.e., amphiphilic; solvent-dependent) liquid crystals (LCs). Through molecular design, we have been able to incorporate functional properties into the LC assemblies and subsequently polymerize them into robust polymer networks with preservation of their nanostructure. These ordered matrices serve as the basis for our new materials synthesis, as well as a platform for investigating structure–property relationships on this size regime. These new LC monomers and assemblies also serve as novel platforms for examining the effect of nanostructure on polymerization kinetics, connectivity, etc., in addition to functional properties.

We are interested not only in the design of organic monomers with self-assembly properties but also intensely interested in the effects of engineered order on their useful bulk properties. We tailor our chemistry to provide control over nanoarchitecture, chemical composition, and processing in our new materials. These factors are crucial if these strategies are to evolve into potentially viable technologies.

Our research program in LC-based, nanostructured polymers is divided into three main directions. The first area is the development of polymerizable lyotropic LCs for the construction of functional, nanostructured polymeric materials. In this research area, we are interested in designing polymerizable LCs to produce nanoporous polymer networks that can be used in several important materials applications areas. One area is their use as templates for making ordered nanocomposites with enhanced bulk performance. Another area is their use as catalytic organic analogues to zeolite and molecular or mesoporous sieves for heterogeneous catalysis with better activity and/or reaction selectivity as a result of their tunable nanopore sizes and environments. A third area is their development into tunable molecular size-selective membranes for applications such as water desalination and toxic vapor filtration from air. A more recent area is their use as enhanced solid ion conductors for Li battery membrane/electrolyte applications, with the possibility of expanding this new work into enhanced proton-conductors and nanostructured fuel cell membranes.

The second area involves the design of monomers based on functional thermotropic LCs to control order, symmetry, and symmetry-based bulk properties in the final polymer assembly. In this research direction, we are interested in designing new functionalized LCs and cross-linked dense polymer networks based on them for energy transducer and property amplification.

The third area is the development of new strategies for the synthesis of LCs that exhibit functional properties and new supramolecular architectures to serve as building blocks for new materials. In this area, we are primarily interested in exploring new strategies for incorporating new functional groups and properties into LCs and polymerizable LCs with preservation of their desired self-assembly properties. These molecules will be used to design new and better LC-based polymers for some of the specific applications mentioned above.

Architectures Based on Room-Temperature Ionic Liquids

In addition to the design and development of new nanoporous polymer materials based on LC starting materials, our research group has recently been involved in the design and synthesis of new type of ionic organic materials based at room-temperature ionic liquids (RTILs), in collaboration with Prof. Rich Noble in the Dept. of Chemical & Biological Engineering at CU Boulder. RTILs are typically molten organic salts at room temperature, and they have a unique combination of properties as liquid materials, including negligible vapor pressure, high ionic conductivity, usual gas solubility properties, and even intrinsic accelerating properties for certain chemical reactions. Consequently, RTILs have been shown to be valuable as new reaction solvents and catalysts, as ion-conducting media, and as new media for light gas separations in supported liquid membranes.

One major goal of this new area of work in our group is generate and explore new types of RTILs containing unusual or unprecedented functional groups, capabilities, and properties in order to expand the applications potential of these unique ionic solvents and liquid materials. A second major goal of our work in the RTIL materials design area is to explore new morphologies of RTIL-based organic materials, such as new polymer and LC architectures based on ionic RTIL building blocks, RTIL-based solid-liquid composites, and nanostructured polymer-RTIL solid-liquid composites. The premise of this latter work is to obtain unique materials systems and morphologies with the desirable properties of RTILs but with more robust solid-like properties for materials applications and a degree of liquid-like mobility for good transport behavior. Our initial application target for these materials is gas separations (i.e., as sorbents and membranes) because of the unique solubility selectivity properties of conventional RTILs for gases such as CO2. We also intend to examine the potential of these new types of RTIL-based materials in other application areas where fluid ions in a solid matrix would be beneficial (e.g., lubrication under extreme conditions, non-aqueous ion conduction, catalysis of organic reactions in unusual environments).

Functional Nanostructured Polymers Based on Liquid Crystal Building Blocks:

• Dwulet, G. E.; Coscia, B. J.; Shirts, M. R.; Gin, D. L. “A Nanostructured Bifunctional Acid-Base Catalyst Resin Formed by Lyotropic Liquid Crystal Monomers,” Can. J. Chem. 2020, 98 (7), 332–336.
• Dischinger, S. M.; Rosenblum, J.; Gin, D. L.;* Noble, R. D.* “Evaluation of a Nanoporous Lyotropic Liquid Crystal Polymer Membrane for the Treatment of Hydraulic Fracturing Produced Water via Cross-Flow Filtration,” J. Membr. Sci. 2019, 592, 15 December 2019, Article 117313, published on-line August 27, 2019 (https://doi.org/10.1016/j.memsci.2019.117313).
• Dwulet, G. E.; Dischinger, S. M.; McGrath, M. J.; Basalla, A. J.; Malecha, J. J.; Noble, R. D.; Gin, D. L. “Breathable, Polydopamine-Coated Nanoporous Membranes that Selectively Reject Nerve and Blister Agent Simulant Vapors,” Ind. Eng. Chem. Res. 2019, 58 (47), 21890–21893.
• Feng, X.; Kawabata, K.; Cowan, M. G.; Dwulet, G. E.; Toth, K.; Sixdenier, L.; Haji-Akbari, A.; Noble, R. D.; Elimelech, M.; Gin, D. L.; Osuji, C. O. “Single crystal texture in a soft mesophase by directing molecular assembly along dual axes,” Nat. Mater. 2019, 18, 1235–1243.
• McGrath, M. J.; Hardy, S. H.; Basalla, A. J.; Dwulet, G. E.; Manubay, B. C.; Malecha, J. J.; Zhi, Z.; Funke, H. H.; Gin, D. L.; Noble, R. D. “Polymerization of Counteranions in the Cationic Nanopores of a Cross-linked Lyotropic Liquid Crystal Network to Modify Ion Transport Properties,” ACS Materials Lett. 2019, 1 (4), 452–458.
• Dwulet, G. E.; Gin, D. L. “Ordered nanoporous lyotropic liquid crystal polymer resin for heterogeneous catalytic aerobic oxidation of alcohols,” Chem. Commun. 2018, 54 (85), 12053–12056.
• Dischinger, S. M.; Rosenblum, J.; Noble, R. D.; Gin, D. L.; Linden, K. G. “Application of a lyotropic liquid crystal nanofiltration membrane for hydraulic fracturing flowback water:  Selectivity and implications for treatment,” J. Membr. Sci. 2017, 543, 319–327.
• Dischinger, S. M.; McGrath, M. J.; Bourland, K. R.; Noble, R. D.; Gin, D. L. “Effect of post-polymerization anion-exchange on the rejection of uncharged aqueous solutes in nanoporous, ionic, lyotropic liquid crystal polymer membranes,” J. Membr. Sci. 2017, 529, 72–79.
• Robertson, L. A.; Gin, D. L. “Effect of an n-Alkoxy-2,4-hexadiene Polymerizable Tail System on the Mesogenic Properties and Cross-linking of Mono-Imidazolium-Based Ionic Liquid Crystal Monomers,” ACS Macro Lett. 2016, 5 (7), 844–848.
• Kerr, R. L.; Edwards, J. L.; Jones, S. C.; Elliott, B. J.; Gin, D. L. “Effect of Varying the Composition and Nanostructure of Organic Carbonate-containing Lyotropic Liquid Crystal Polymer Electrolytes on Their Ionic Conductivity,” Polym. J. 2016, 48 (5), 635–643.

New Ionic Materials and Polyelectrolyte Architectures Based on Room-Temperature Ionic Liquids:

• Malecha, J. J.; Biller, J. R.; Lama, B.; Gin, D. L. “System for Living ROMP of a Paramagnetic FeCl4–-Based Ionic Liquid Monomer: Direct Synthesis of Magnetically Responsive Block Copolymers,” ACS Macro Lett. 2020, 9 (1), 140–145.
• Dunn, C. A.; Shi, Z.; Zhou, R.; Gin, D. L.; Noble, R. D. “(Cross-linked Poly(ionic liquid) – Ionic Liquid – Zeolite) Mixed-Matrix Membranes for CO2/CH4 Gas Separations Based on Curable Ionic Liquid Prepolymers,” Ind. Eng. Chem. Res. 2019, 58 (11), 4704–4708.
• May, A. W.; Shi, Z.; Wijayasekara, D. B.; Gin, D. L.; Bailey, T. S. “Self-Assembly of Highly Asymmetric, Poly(Ionic Liquid)-rich Diblock Copolymers and the Effects of Simple Structural Modification on Phase Behavior,” Polym. Chem. 2019, 10 (6), 751–765.
• Mori, D. I.; Gin, D. L. “A Curable Ionic Liquid Prepolymer-based Ion Gel Coating System for Toxic Industrial Chemical Hazard Mitigation on Porous Substrates,” Ind. Eng. Chem. Res. 2018, 57 (47), 16012–16020.
• Shi, Z.; May, A. W.; Kohno, Y.; Bailey, T. S.; Gin, D. L. “Metal-Containing Ionic Liquid-Based Uncharged-Charged Diblock Copolymers that Form Ordered, Phase-Separated Microstructures and Reversibly Coordinate Small Protic Molecules,” J. Polym. Sci. A, Polym. Chem. 2017, 55 (18), 2961–2965.
• Mori, D. I.; Martin, R. M.; Noble, R. D.; Gin, D. L. “Cross-linked, polyurethane-based, ammonium poly(ionic liquid)/ionic liquid composite films for organic vapor suppression and ion conduction,” Polymer 2017, 112, 435–445.
• Cowan, M. G.; Lopez, A. M.; Masuda, M.; Kohno, Y.; McDanel, W. M.; Noble, R. D.; Gin, D. L. “Imidazolium-based Poly(ionic liquid)/Ionic Liquid Ion-Gels with High Ionic Conductivity Prepared from a Curable Poly(ionic liquid),“ Macromol. Rapid Commun. 2016, 37 (14), 1150–1154.
• Martin, R. M.; Mori, D. I.; Noble, R. D.; Gin, D. L. “Curable Imidazolium Poly(ionic liquid)/Ionic Liquid Coating for Containment and Decontamination of Toxic Industrial Chemical-Contacted Substrates,” Ind. Eng. Chem. Res. 2016, 55 (22), 6547–6550.
• Cowan, M. G.; Gin, D. L.; Noble, R. D. “Poly(ionic liquid)/Ionic Liquid Ion-gels with High ‘Free’ Ionic Liquid Content: Platform Membrane Materials for CO2/Light Gas Separations,” Acc. Chem. Res. 2016, 49 (4), 724–732.  (peer-reviewed review article).