| Supramolecular gels (physical gels), formed by the low molecular mass organic gelators (LMOGs) self-assemble in organic solvents through the non-covalent bonds such as intermolecular hydrogen bonding,Ï€-Ï€stacking, van der Waals interactions, donor-acceptor interactions, coordination, solvophobic forces (hydrophobic forces for gels in water) and so on to form the supramolecular structure aggregates with fiber-like, rod-like, tube-like, disk-like, tape-like and other morphology, have generated enormous interest rencently for scientific research and application. Organogelators and their organogels have been used for smart materials, drug delivery systems, templates for nanomaterial preparation, gel electrolytes, chiral separation, catalysis other fields as a result of their thermo-reversibility, chemical sensitivity and diversity of nanostructures.Three kinds of reactable gelators with different alkyl chains were synthesized by using the high activity of isocyanate and alkylamine, and supramolecular gels could be obtained at room temperature. The thermodynamic properties and rheological behavior of gels and the mechanism of self-assembly were investigated. The effect of the centrifugal force field and shear field on morphology and thermodynamic properties of the supramolecular structure aggregates formed by gelator in solvents was investigated. We reported herein new aggregates of low molecular mass organic gelators confined within the nano-scale interlayer space of the mineral organo-montmorillonite (OMMT), the thermodynamic properties and the possible mechanism of self-assembly were studied.This thesis is consisted of several sections as the following:1 Three kinds of reactable gelators 1-methyl-2,4-bis(N'-octadecylureido)benzene (MBB-18), 1-methyl-2,4-bis(N'-dodecaneureido)benzene (MBB-12) and 1-methyl-2,4- bis(N'-octanaureido)benzene (MBB-8) were synthesized, which could aggregate and self-assembly at room temperature, and forming thermal reversible gels with several organic solvents at very low concentrations. The thermodynamic and rheological properties of the supramolecular gels were investigated.2 Field emission electron microscopy (FE-SEM) revealed a three-dimensional (3D) network consisting of fiber-like aggregates. Moreover, various lengths of alkyls led to different morphology of fiber-like aggregates and different thermodynamic properties as Differential scanning calorimetry (DSC) showed. FT-IR and 1HNMR demonstrated that intermolecular hydrogen bonding was the main driving force for the self-assembly and formation of the gels. Finally, a self-assembly mode was proposed through the results of X-ray diffraction (XRD) and molecular stimulation by Spartan and HyperChem software.3 The aggregates of MBB-18 occur under the influence of centrifugal force and shearing force fields was investigated. The minimum gelation concentrations of MBB-18 in organic solvents under a centrifugal force field were significantly higher than those in the absence of a centrifugal force field, indicating a significant effect of the external field on the self-assembly of MBB-18. The oriented aggregation of MBB-18 in solvents induced by centrifugal and shearing forces, as well as the thermotropic behavior of oriented organogels has been investigated by FE-SEM, XRD and DSC respectively.4 Two bisurea gelators MBB-18, MBB-12 and tow acylamide gelators bis(4'- stearamidophbeyl)methane (BSM-18) and bis(4'-octanamidophenyl)methane (BOM-8) were affused into the interlayers of organo-montmorillonite (OMMT) by heating and ultrasonication to investigate the gelation of chlorobenzene and poropylene carbonate (PC) confined within the nano-scale interlayer space. Based on an analysis of the DSC and XRD data for the gels confined within the organo-montmorillonite and formed in the bulk space, we argued that the gelators self-assembled in an unusual manner when confined within the interlayer space of OMMT in comparison with that in bulk space. This novel route for self-assembling of gelators in confined space might offer new insights into the mechanism of natural self-assembling processes, which occured in nano-scale environments.5 Chiral separation films were prepared through the supramolecular structure aggetates formed by MBB-18 in acrylate monomer using Boc-L-phenylalanine as template molecule for the separation of racemic phenylalanine. Adsorption efficiency of D- or L-phenylalanine on the films with different concentration of gelator and template molecule, and with different monomer ratio was carried out by the UV spectra.
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