Gelation And Liquid Crystalline Behaviour Of Bi-amide Derivatives With Different Number Of Terminal Alkyl Chains

In recent years，self-organizing behavior of small organic molecules arewidespread concern, their liquid crystalline and gel acts also has been a focus forresearchers. These soft materials that can respond to external stimuli such as light,temperature, electrical pulses and chemicals. There are potential applications intemplate synthesis, controlled release, separations, and biomimetics. Supermoleculestructures are the result of not only additive but also cooperative interactions,including hydrogen bonding, π-π stacking, donor–acceptor interactions, hydrophobicforces, metal coordination and van der Waals interactions. This context, as part of ourcontinuing research in supramolecular self-assembly, design and synthesize bi-amidederivatives of different alkyl chains on the tail based on hydrogen bonding and π-πinteractions,we probe intermolecular interactions and self-assembly behavior. Thework is as follows:1)Synthesis and molecular structural characterization of bi-amide derivativeswith different number of terminal alkyl chainsThis thesis design and synthesize bi-amide derivatives containing azobenzene.the length of the alkyl chain is same but the number is different(BNBC-8,BNBC-D8).The purity of these molecules have been confirmed by proton nuclearmagnetic resonance spectroscopy, Fourier transform infrared spectroscopy andelemental analysis.2) Liquid crystalline behavior of rod-like BNBC-8moleculeBNBC-8hydrogen bonding pattern is recognized intermolecular hydrogen bondby1H NMR and FT-IR spectroscopy with variable temperature. Under POMobservation in220℃, BNBC-8molecule exhibits two black brush point defects andfour black brush point defects.The schlieren texture has a strong fluidity,it is a nematicphase.180℃, the schlieren texture gradually turned into a fan-shaped texture, Theflowability becomes bad, The fan and in the vertical direction of the polarizing filmpresents a certain angle,it is a Smectic C phase. Differential scanning calorimetryanalyzer (DSC) results showed that the BNBC-8molecule with increasingtemperature has smectic phase and nematic phase liquid crystal state, respectively,Wemeasure the phase transition temperature and enthalpy values. The Variable Temperature XRD identifie molecule as layered structure in the smectic C phase. Weestimate the schematic arrangement of the molecule. However, with the increase inthe alkyl chain, multi-chain molecules BNBC-D8and BNBC-T8did not exhibit liquidcrystalline behavior.3) Research of gel of dovetail BNBC-D8molecular and wedge BNBC-T8molecularA single chain BNBC-8molecule does not gel in any organic solvent.So weCarried out a detailed study of gel two chain BNBC-D8molecule and three chainBNBC-T8molecule. By variable temperature1H NMR spectrum,we confirmed thetwo hydrogen bonding mode as intermolecular hydrogen bonds.Try the gel capacity ofmolecules in different organic solvents,the BNBC-D8molecular is in favor of gelationSlightly in larger polar Alcohols (Methanol, ethanol and n-butanol). In addition to theabove alcohols,BNBC-T8molecule can be into a gel,at the same time it can also beinto a gel in acetone. It cannot gel in a smaller polar solvent(such as chloroform).Wecan conclude that molecule may be gelled in more organic solvents with alkyl chainsincreasing. While using the FE-SEM to observe the morphology of the gel, each gel isbasically slender gathered fibrous. Interesting, BNBC-T8molecule include spiral inthe methanol gel, and the left-handed and right-handed co-exist. We research the driveforce of the gel in detail with UV spectrum of variable temperature and variableconcentration,1H NMR and IR spectra of variable temperature.It is the synergisticeffect of the intermolecular hydrogen bonding, π-π stacking, and van der Waals forces.Finally,the light response behavior of the BNBC-T8molecule has been exploredthrough the character of the azobenzene photoisomerization.