Design,Synthesis And Self-assembly Of Barbituric Acid Based Taper Shaped Rodlike And Bent-core Polycatenar Like Liquid Crystal Compounds

Liquid crystal combines both periodic order of crystal and mobility of liquid at the molecular level.Liquid crystal is a kind of excellent soft material with self-healing,adaptive and stimulating response.It plays an important role in areas such as optics,electro-magnetism,material science,biology and so on.The first chapter introduces the synthesis and liquid crystal behavior of barbituric acid based taper shaped rodlike compounds and their hydrogen-bonded complexes with triazine derivatives.By using Knoevenagel reaction as the key step,a series of barbituric acid based taper shaped rodlike compounds(BC~3/n,BC~3/14 and BT3/12)consisting of a styrene conjugate rodlike core with the barbituric acid at one end,and triple alkyl chain at the other end were synthesized.All these compounds can self-assemble into columnar liquid crystalline phase with c2mm lattice in its pure state.The spectral investigation revealed that extention the conjugated length of molecular structure,the photoelectric properties of the compound would become more excellent.Meanwhile,this complex BC/T showed both liquid crystalline property in its pure state and supramolecular organgels with three-dimensional networks in organic solvents.The gels can be reversible to the external heat and mechanical vibration stimulation,and the three-dimensional network structure of the gels is confirmed by SEM.These results suggested that the excellent properties of gels originated from their highly ordered structures resulting from the synergistic effect of intermolecular hydrogen bonding,?-?stacking and van der Waals.In addition,the fluorescence of 1T2/12 was strongly quenched with the addition of BC~3/12.Therefore,these barbituric acid based taper shaped rodlike liquid crystals may have potential applications in photoelectric sensors and nanoscale devices.The second chapter introduces two kinds of bent-core polycatenar liquid crystalline molecules containing a methylene(CH2)or carbonyl(CO)central unit coupled at both sides with 1,2,3-triazole linked dendronic arms,such as ?C2/n,IC4/12,?C4/12,?C6/n,?E6/n.The liquid crystal behavior of the compounds was studied by POM,DSC and XRD.It was found that all the compounds in series ? with flexible bent-core were unable to form liquid crystal.Compounds in series ? with polar rigidbent-core have liquid crystallinity with wider hexagonal columnar phase ranges in their pure states due to the polarity between the dipole-dipole interaction of the central carbonyl groups.In addition,the compound ?C4/12 with the central carbonyl group tends to form a polar column phase.Also experiments on cation recognition have been done,the results clearly indicated that ?C~3/16 was selective to bind with Hg2+ and Fe3+ ion,and ?E~3/16 was selective to bind with Fe3+ ion.In addition,the gelation abilities of the compounds were examined in various organic solvents,and gelation was easier to form with the elongation of the alkoxyl chain.The result indicated that the length of the alkyl chain had certain influence on the formation of the organic gels.This low molecular weight organogel has potential applications in many ways,such as nanomaterials,drug delivery systems,sensors,and so on.The third chapter is the experimental section including the synthetic route and spectral data.