The Synthesis, Self-assembly And Photophysical Properties Of Low Molecular Weight Organogelators

Nowadays, the design, synthesis and study of gelation properties of lowmolecular weight gelators have been received much attentions because of thediversity of structures of gelators, which may induce the gelators toself-assemble into various dimensional and morphologic superstructures inorganic solvents directed by noncovalent interactions such as H-bonding, vander Walls, π-π stacking ect. We may construct functional organogel withspecial nanostructures through introduction some functional groups to theorganogelators. The organogels have numerous potential applications inoptical devices, sensors, and drug delivery systems. In addition, introducinggroups that could interact with inorganic ions into the organogel system wouldgive us an opportunity to generate diverse inorganic nanostructures, such aslinear fibers, lamellar and helical fibers structures. We synthesized several series optical organogelators and investigated theirgelation morphologies. By the investigation of FT-IR, UV-vis, XRD, and CDspectra, the molecular interactions and the stacking mode in theself-assembled gel system could be obtained. The introduction of thefunctional groups in the gel could make the organogel show unique opticalproperties which have potential applications in optical nanomaterials.Furthermore, using hydrogel as templates to produce various inorganicnanomaterials were also researched. Some creative results were obtained. Themain results were outlined as follows:(1) In the first chapter, we have designed a new series of achiraldiscotic organogelators consisting of triphenylbenzene as core to preparewell-defined helical fibers by tuning the peripheral substituted alkoxy chains.The FT-IR and UV-vis absorption revealed that H-bondings and π-πinteractions were the main driving forces for the formation of theself-assembly. The XRD diagrams suggested that the self-assembled structureof the gels changed from hexagonal columnar phases to lamellar ones whenthe volume of the alkoxy chain of molecules increased. The formation of thehelical fibers was due to the helical inducement of the core cooperating withthe packing and arrangement of the alkoxy chains. The novel fluorescenceemission enhancement of the organogels was discovered, which was inducedby the aggregation of the molecules.(2) In the second chapter, we synthesized a new discotic organogelatorconsisting of π-conjugated triphenyl benzene as core and chiral groups as theperiphery. The chiral periphery of the molecule could induce the chiralityamplification and chiral self-assemblies with hexagonal columnar stacking inclockwise direction. It also showed the aggregation of the molecules resultedin the emission quenched in the gel phase.(3) In the third chapter, we described a new hydrolysis-polycondensationprocess using functional triphenyl benzene as the bridge to obtainself-template hybrid silicas. From the results of UV-vis, FT-IR spectra, itindicated that the H-bonding among urea groups and the π-π interactionamong the triphenyl benzene groups were the main factors for thepreorganization of the molecules. The results suggested that the structures ofthe hybrid silicas not only arised from the intrinsic properties of the organicfragment, but also depended on the hydrolytic conditions which couldinfluence the self-assembling behaviors of the organic moieties. Theintroduction of the functional triphenyl benzene allowed the hybrid silicas toexhibit fluorescent properties, and also provided a way to mould newnanomaterials which were programmed to self-assemble and exhibitedtargeted physical properties by design.(4) In the fourth chapter, a series of functional binary gels with goodgelated capability based on L-tartaric acid and stilbazoles were prepared andshowed good gelated capability in most chlorinated solvents. Herein,L-tartaric acid not only introduced the functional groups (fluorescentstilbazole group) into the gel system but also provided main motif for theformation of gel phase via multiple hydrogen bondings, which provide asimple and more extensive way for the fabrication of functional gels throughnon-covalent interactions. The obtained gels showed strongly enhancedemission and the longer lifetime due to the supramolecular self-assembling. Itis hoped that such fluorescence modulated organogel may be useful for somesensors. In addition, it provides an extensive way to prepare functional gelsvia non-covalent interactions.(5) In the fifth chapter, we synthesized three series of glucose-basedhydrogels and investigated the self-assembled properties. The resultedsuggested that the H-bonding and π-π interaction were the main drive forcesfor the generation of hydrogels and the molecules stacked into a bilayerstructures in the hydrogels. Because of the water system, the introduction ofinorganic precursors was easy and economic, and then using the hydrogels astemplate to mineralize inorganic nanostructures.