Zwitterions as building blocks for functional liquid crystals and block copolymers

Applications of Zwitterions and Zwitterionic Polymers for Li-Ion Batteries

A zwitterion is a neutral compound that has both a cation and an anion in the same molecule. Quaternary ammonium cations are frequently used for zwitterions. Zwitterions with quaternary ammonium cations are also common in biological molecules, such as phospholipids, which are the main components of cell membranes. Chemically, they have broad applicability because they are dielectric, non-volatile, and highly polar compounds with a large dipole moment. In addition, after salt addition, ion exchange does not occur in the presence of zwitterions. Owing to these characteristics, zwitterions have been applied as novel electrolyte materials targeting high ionic conductivity. In this review, application of zwitterions and their polymers for Li-ion batteries is addressed.

Cross-linkable, phosphobetaine-based, zwitterionic amphiphiles that form lyotropic bicontinuous cubic phases

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.

Stabilizing Differential Interfacial Curvatures by Mismatched Molecular Geometries: Toward Polymers with Percolating 1 nm Channels of Gyroid Minimal Surfaces

Soft materials with self-assembled networks possess saddle-shaped interfaces with distributed negative Gaussian curvatures. The ability to stabilize such a geometry is critically important for various applications but can be challenging due to the possibly "deficient" packing of the building blocks. This nontrivial challenge has been manifested, for example, by the limited availability of cross-linkable bicontinuous cubic (Q) liquid crystals (LCs), which can be utilized to fabricate compelling polymers with networked nanochannels uniformly sized at ∼1 nm. Here, we devise a facile approach to stabilizing cross-linkable Q mesophases by leveraging the synergistic self-assembly from pairs of scalably synthesized polymerizable amphiphiles. Hybridization of the molecular geometries by mixing significantly increases the propensity of the local deviations in the interfacial curvature specifically required for Q assemblies. "Normal" (type 1) double gyroid LCs possessing 1 nm ionic channels conforming to minimal surfaces can be formulated by simultaneous hydration of the amphiphile mixtures, as opposed to the formation of hexagonal or lamellar mesophases exhibited by the single-amphiphile systems, respectively. Fixation of the bicontinuous network in polymers via radical polymerization has been efficaciously facilitated by the presence of the bifunctional polymerizable groups in one of the employed amphiphiles. High-fidelity lock-in of the ordered continuous 1 nm channels has been unambiguously confirmed by the observation of single-crystal-like diffraction patterns from synchrotron small-angle X-ray scattering and large-area periodicities by transmission electron microscopy. The produced polymeric materials exhibit the required mechanical integrity as well as chemical robustness in a variety of organic solvents that benefit their practical applications for selective transport of ions and molecules.

Mussel-inspired biomaterials: From chemistry to clinic

After several billions of years, nature still makes decisions on its own to identify, develop, and direct the most effective material for phenomena/challenges faced. Likewise, and inspired by the nature, we learned how to take steps in developing new technologies and materials innovations. Wet and strong adhesion by Mytilidae mussels (among which Mytilus edulis-blue mussel and Mytilus californianus-California mussel are the most well-known species) has been an inspiration in developing advanced adhesives for the moist condition. The wet adhesion phenomenon is significant in designing tissue adhesives and surgical sealants. However, a deep understanding of engaged chemical moieties, microenvironmental conditions of secreted proteins, and other contributing mechanisms for outstanding wet adhesion mussels are essential for the optimal design of wet glues. In this review, all aspects of wet adhesion of Mytilidae mussels, as well as different strategies needed for designing and fabricating wet adhesives are discussed from a chemistry point of view. Developed muscle-inspired chemistry is a versatile technique when designing not only wet adhesive, but also, in several more applications, especially in the bioengineering area. The applications of muscle-inspired biomaterials in various medical applications are summarized for future developments in the field.

Zwitterionic materials with disorder and plasticity and their application as non-volatile solid or liquid electrolytes

Zwitterionic materials can exhibit unique characteristics and are highly tunable by variation to the covalently bound cationic and anionic moieties. Despite the breadth of properties and potential uses reported to date, for electrolyte applications they have thus far primarily been used as additives or for making polymer gels. However, zwitterions offer intriguing promise as electrolyte matrix materials that are non-volatile and charged but non-migrating. Here we report a family of zwitterions that exhibit molecular disorder and plasticity, which allows their use as a solid-state conductive matrix. We have characterized the thermal, morphological and structural properties of these materials using techniques including differential scanning calorimetry, scanning electron microscopy, solid-state NMR and X-ray crystallography. We report the physical and transport properties of zwitterions combined with lithium salts and a lithium-functionalized polymer to form solid or high-salt-content liquid electrolytes. We demonstrate that the zwitterion-based electrolytes can allow high target ion transport and support stable lithium metal cell cycling. The ability to use disordered zwitterionic materials as electrolyte matrices for high target ion conduction, coupled with an extensive scope for varying the chemical and physical properties, has important implications for the future design of non-volatile materials that bridge the choice between traditional molecular and ionic solvent systems.

One Dimensional Enhanced Anhydrous Proton Conduction in Well Defined Molecular Columns Induced by Non-Covalent Interactions

1D anhydrous proton conduction is enhanced significantly in ionic channels created by self-assembly of functionalized organic phosphonic acid and aromatic heterocyclic 1,2,4-triazole molecules. This study reveals high proton conduction in one dimension through a well-defined supramolecular architecture in which two different molecules undergo host-guest synergy and self-assemble to provide two-fold advantages: 1) formation of the ionic channels and 2) higher proton conduction in the absence of water. A clear correlation is found between the phenomena of ionic channels and anhydrous conductivity in the absolute dry state and we demonstrate that the one-dimensional conductivity can be as high as that recorded for 3D channels in, for instance, Nafion.

Dimension control of ionic liquids

Ionic liquids have established themselves as promising soft compounds for bringing innovation to materials science. For further developing functions and abilities of ionic liquids, one of the most important challenges is to organize ionic liquids into dimensionally ordered states. In this feature article, we will present the organization of ionic liquids by endowing them with liquid-crystalline properties. In particular, focusing on the specific abilities and properties of functional ionic liquids, a variety of nanostructured ionic materials have been developed and their unique and enhanced functions have been revealed. Some potential uses of organized ionic liquids have also been mentioned.

Functional Liquid Crystals towards the Next Generation of Materials

Since the discovery of the liquid-crystalline state in 1888, liquid crystal science has made great advances through fusion with various technologies and disciplines. Recently, new molecular design strategies and new self-assembled structures have been developed as a result of the progress made in synthetic procedures and characterization techniques. Since these liquid crystals exhibit new functions and properties derived from their nanostructures and alignment, a variety of new functions for liquid crystals, such as transport for energy applications, separation for environmental applications, chromism, sensing, electrooptical effects, actuation, and templating have been proposed. This Review presents recent advances of liquid crystals that should contribute to the next generation of materials.