Synthesis,Self-assembly And Properties Of Biphenyl,Azobenzene And BTD Compounds

Liquid crystal is an ordered fluid,in which the separation of incompatible components and the parallel arrangement of rigid cells are combined to produce a long-range order in position and direction.Increasing the complexity and stability of liquid crystals will benefit their application as multifunctional new liquid crystal materials.The fluorinated effect(incompatibility between the perfluoro chain RF and the hydrocarbon chain RH)can effectively promote the formation and stability of the liquid crystal phase.Azobenzene compounds contain a conjugated ? system,showing a strong set of ?-? * transitions in the ultraviolet region,and a weak set of n-? * transitions in the visible region.By accurately incorporating the azo element into the target compound,we can predict the light response characteristics of the azo element during the trans-cis photoisomerization process.The unique photoresponse characteristics of azobenzen compounds make them great potentials for light storage,sensors,and drug delivery.Fluorescent BTD derivatives are often effective and stable fluorophores even in the excited states.Not only BTDs have strong electron-withdrawing abilities,which are helpful for intra-molecular charge transfer(ICT),but also have highly polarized natures,which can lead to intermolecular interactions and usually provide an ordered crystal structure.Fluorescent BTD usually shows a large Stokes shift,and even if it is irradiated for a long time,the fluorescence emission usually does not disappear.Therefore,BTD derivatives have important application value in light-emitting devices,biological imaging and sensors.This thesis mainly studies the self-assembly behavior and properties of three types of compounds.The main content is divided into five chapters.In Chapter 1,we introduce the concepts of supramolecular chemistry and liquid crystal and the application background of liquid crystal compounds in the field of medicinal chemistry,and then mainly introduce the research progress of biphenyls,azobenzenes and BTDs in recent years.In Chapter 2,a series of fluorinated chain contained rod-like compounds with biphenyl and biphenol ester as the central bridge were synthesized through the Suzuki coupling reaction catalyzed by Pd(0).One side of the rod core is a fluorinated chain,another side is siloxane chain or an oxane chain.The morphological characteristics of the compounds were studied by polarized light microscope(POM),the phase transition temperature was determined by differential scanning calorimeter(DSC)and the lattice parameters were calculated by X-ray diffraction.These compounds can self-assemble into smectic phases(or lamellar phases).And such compounds can form organogels in selective solvents.In chapter 3,a series of asymmetric molecular compounds with azobenzene as the central bridge,ester groups,carboxylic acids,amides,cholesterol and other functional groups on one side,and alkyl chains of different lengths on another side were synthesized.By studying the effects of different functional groups and the volume fractions of alkyl side chains on their self-assembly properties,it was found that column phases can be observed in compounds with longer alkyl side chains containing ester groups or in compounds with shorter alkyl side chains containing carboxyl groups.It is shown that the increase in the volume of the alkyl side chain and the increase in the polarity of the functional group are helpful for the self-assembly of the compounds into a liquid crystal phase.In addition,such compounds are capable of self-assembling into gels in selective solvents.In chapter 4,Suzuki reaction was used as the key step to synthesize amphiphilic compounds based on BTD(Benzo-2,1,3-thiadiozole)as the central bridge.The two ends of the molecule were a hydrophilic flexible polyether chain and an lipophilic flexible alkyl chain.The critical micelle concentration of the compound was measured and compared with the critical micelle concentrations of several commonly used surfactants.The results showed that the critical micelle concentration of this compound was lower than the critical micelle concentrations of the most commonly used surfactants.We also preliminarily studied the encapsulation capacity and the drug loading capacity of the micelles formed by such compounds in the water environment for fat-soluble drugs,and found that the compounds have certain encapsulation capacity for podophyllotoxin.Therefore,the compound provides an important reference value for the development of new and efficient surfactants and drug carriers.The fifth chapter is the experimental part,which contains the specific synthesis steps and related nuclear magnetic spectra data etc.