Supramolecular Liquid Crystals For Ion Transport Materials And Their Structures Studied By Synchrotron Radiation Technique

Ion transport through nanochannels or microchannels plays an important role in cell membranes, biosensor/actuator, molecular switches, biomedical, energy materials (proton and Li+transport materials) and etc. The ions in the life system (K+and Na+) play an important role in tuning the physiological functions such as nerve and musculature. Peter Agre, professor of the Johns Hopkins University, and Roderick MacKinnon, a Rockefeller University scientist shared the 2003 Nobel Prize in Chemistry for their discovery of "channels" that regulate and facilitate water molecule transport through cell membranes, and the spatial structure of ionic channels, relatively. Li+transport in lithium batteries and H+transport in fuel cell have a direct effect on the performance and lifespan of the battery. The unique molecular structure with special ion channels designed from the chemical molecular scale will offer a possible reasonable explanation on how the ion transport in the solution, life system and energy materials, which also offer some ways for designing the ion transport materials with high performance. Herein we designed and prepared a series of aromatic aramid electrolytes, which can be formed lyotropic supramolecular liquid crystals in the water by the secondary interactions of supermolecule such as hydrogen bonding,Ï€-Ï€stacking interactions and steric factors. The structure of the supramolecular liquid crystals were studied by Polarized Light Microscopy (POM) and Synchrotron-based small and wide angle x-ray scattering (SAXS/WAXS). The property of ion transport was systematically studied by tuning the anisotropic nature, photo-reversible molecular structure and effective lithium ion'dissociation enhancers' of supramolecular liquid crystals. The main results of this dissertation are described as follows:(1) We designed and prepared a new organic discotic molecule (P106) consisting of 10 phenyl rings joined symmetrically with amide linkages, which is functionalized at the periphery with sulfonic acid groups. The structure of the supramolecular liquid crystals was studied by POM, SAXS/WAXS and computer simulation. The discotic molecule exhibits a hexagonal supramolecular columnar liquid crystalline phase in the aqueous solution with a wide range of concentration from 0.086 g/mL to 0.28 g/mL at room temperature. The cross section of the columns is constructed with seven discotic molecules instead of single discotic molecule. As far as the authors aware no exception has been reported because the disc-shaped molecules possess the right symmetry to stack into columns directly. Combining the symmetry sulfonic acid groups at the periphery of the discotic molecule and the clusters formed by the seven discotic molecules, the sulfonic acid groups in columns of the hexagonal liquid crystalline phase tend to self-organize into ionic channels. The combination of ionic channels and liquid crystalline properties leads to the achievement of anisotropic ionic conductivity through macroscopically aligning the ionic nanochannels. In parallel to the success of anisotropic conductivity in thermotropic liquid crystals, the new lyotropic supramolecular liquid crystals may serve as mode system for the understanding of ion transportation and have potential application in fuel cell, lithium batteries and etc.(2) The designed discotic molecule P106 of (1) can be formed mutil-sacle fibers (the diameter of fibers from nanometer to microns, or submillimeter) by the hierarchical supermolecular self-assemble in the water. In low concentration (10-3-10-2 g/mL), the discotic aromatic aramid molecules in water can be self-assmbled into nanofibers. In supramolecular liquid crystalline phase (0.086-0.280 g/mL), it can be self-assmbled into macrofibers. The solid of discotic molecule in the atmosphere of KBr salt saturation, it can be self-assmbled rods with sub-millimeter size. Although, the state of discotic molecule was changed, it still tends to form fibers. The unique property of discotic molecule will make it become a novel fiber-forming materials. Due to the sulfonic acid groups of the fibers, it can be used as ionic fibers, ion transport materials, sensors and etc.(3) We designed and prepared a new photo-responding molecule with three-ways junctions (azo-P73) consisting of 7 phenyl rings joined symmetrically with amide linkages, which is functionalized at the periphery with sulfonic acid groups. The structure of the supramolecular liquid crystals was studied by POM, SAXS/WAXS and calculation. The azo-P73 molecule exhibited a hexagonal supramolecular columnar liquid crystalline phase in the aqueous solution with a range of concentration from 0.05 g/mL to 0.076 g/mL at room temperature. In a range of concentration from 0.076 g/mL to 0.12 g/mL, it formed the hexagonal liquid crystalline gel. The cross section of the columns is constructed with three azo-P73 molecules instead of single azo-P73 molecule. The clusters formed by three azo-P73 molecules stack into columns of the hexagonal liquid crystalline phase, which have helical structure. The combination of ionic channels and liquid crystalline properties leads to the achievement of anisotropic ionic conductivity through macroscopically aligning the liquid crystalline. The ionic conductivity can also be reversiblly tuned by UV light. The azo-P73 molecule has potential application in transport materials, photo-and ion-responding sensor, molecular switches and etc.(4) According to the latest research reports, zwitterionic molecules can be used as extremely effective lithium ion'dissociation enhancers'of lithium polyelectrolyte systems, and helpful to prepare the high-conductivity polyelectrolyte materials. We designed and prepared a series of polyelectrolyte containing zwitterionic parts. First, we designed and prepared a novel lithium polyelectrolyte with self-enhance dissociation of lithium ions. Second, we designed and prepared a zwitterionic molecule, which was used to exzamin if the zwitterionic molecule has ability to enhance dissociation of lithium of complexes like lithium polyelectrolyte systems. Third, we designed and prepared some discotic liquid crystal molecules with zwitterionic parts at its periphery, which have potential function with self-enhance dissociation of lithium channels.