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Synthesis of a Gelator Containing Azobenzene and Its Application on Photoresponsive Liquid-crystalline Physical Gels

Author: JiangMan
Tutor: JieXiaoLin
School: Huazhong University of Science and Technology
Course: Polymer Chemistry and Physics
Keywords: liquid crystal physical gel photoresponsive azobenzene hydrogen bond electro-optic properties rheological behavior
CLC: O648.17
Type: Master's thesis
Year: 2013
Downloads: 13
Quote: 0
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Abstract


Self-assembly of small functional molecules into supramolecules is a new approach toprepare new materials and nanoscale devices. Liquid crystals (LCs) have attracted muchattention due to their anisotropic molecular alignment with potential applications on theinformation and mass transport, sensing, catalysis, electro-optical displays, etc. Recently,the combination of LCs and gelators into liquid-crystalline physical gels (LC physical gels)made out its unique electro-optic properties.In this thesis, we designed and synthesized a new azobenzene-containing gelator (AG)due to the photoisomerization behavior of azobenzene under UV and visible lights. Itsmolecular structure were characterized by Fourier transform infrared (FT-IR), nuclearmagnetic resonance (NMR) and mass spectra. The photoisomerization and crystallizationbehaviors of AG were investigated by ultraviolet-visible (UV-vis) spectra, and differentialscanning calorimetry (DSC) and polarized optical microscopy (POM), respectively.The nematic liquid crystallines P0616A were gelled by AG. The formed P0616A/AGgel was photo-and temperature dually responsive. DSC and POM results showed themicrophase-separation of LC physical gels and the chiral nematic texture of P0616A.Field emission scanning electron microscopy (FE-SEM) images of the xerogels showedentangled fibrous aggregates of gelators in a3D network. Rheological measurementsshowed that the melting onset of gels (Tgel) increased with its content. Electro-opticmeasurements showed that with the increasing of the content of gelator, the thresholdvoltages (Vths) were similar, while the saturation voltages (Vsat) and the contrast increased. onof all samples were similar and much quicker than off. Variable temperature FT-IRspectra indicated that the driving force for the self-assembly of gelators was hydrogenbond from–CONH-in that the N-H vibration was weaker at70oC than at20oC andshifted to higher wavenumber.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Colloid chemistry ( physical and chemical dispersion system ) > Colloid > Gel and soft
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