Design,Synthesis And Self Assembly Of Two Types Of Triblock Amphiphilic Liquid Crystals Based On Cvanostyrene And Tetrathiophenen Bolaamphiphiles

Usually,matter has three states,namely crystal,liquid,gas.Liquid crystals(LCs)can be considered as a mesophase of matter which combines order and mobility in a unique way.Because LCs can respondto the external stimuli,such as temperature,electric,magnetic,light,etc,they have played important roles in a number of technologies today.Because the molecular structures have a very important influence on their properties and applications,the study of relationship between structures of liquid crystal molecules and their properties has become one of the important scientific research subjects today.Triblock amphiphilic compounds consisting of a rigid aromatic core,polarhydrophilic groups,hydrophobic flexible chains can form a number of nanostructures driven by non-covalent intermolecular forces(e.g.micro-segregation interaction,?-? interaction,hydrogen bonding interaction,and so on).Different rigid aromatic units can endow these compounds different photophysical properties,therefore the self-assembly behavior of triblock amphiphilic compounds with special rigid aromatic unit have attracted much more attendtion in recent years.In addition,bolaamphiphilic liquid crystals are also a research focus because they can self-assemble into a variety of complex novel supramolecular nanostructures.This thesis is composed of three chapters.Chapter 1 and 2 introduce the synthesis and liquid crystalline behavior of the a cyanostyrene derivatives and tetrathiophene bolaamphiphiles respectively.Chapter 3 is the experiment part.In chapter 1,a series of triblock amphiphilic liquid crystals containing a-cyanostyrenewere designed and synthesized.By changing the number,length and type of the terminal alkoxy chains,the relationshiop between the molecular structure and the liquid crystalline self-assembled structures was studied systematically.Our study found that compound I1/12 with only one alkoxy chain exhibited double layer semetic A phase(SmA2).By increaseing the number of the terminal alkoxy chain,compound I2/16 with two terminal alkoxy chains exhibited Colhex/p6mm liquid crystal phase.For compounds I3/n with three terminal alkoxy chains,only Colhex/p6mm liquid crystal phase was found.However,by replacing linear alkoxy chains with branched alkoxy chains,the compound exhibited a Cubi/Pm3n phase.In addition,compound I3/12 can form organo gel in different solvents and its morphology was investigated by SEM UV and PL investigations showed that compound I3/12 displyed cis-trans isomerization in gel and solution and liquid crystal status under the irradiation of 365 nm light and visible light.Finally,the aggregation induced enhanced emission(AIE)and mechanofluorochromic properties of I3/14 were studied,which showed that these compounds can be applied as aggregation induced enhanced emission materials and reversible pressure-sensitive materials.In chapter 2,a series of tetrathiophene bolaamphiphiles with four lateral alkyl chains attached equally on the central of the two thiophene rings were designed and synthesized.The previous study showed that tetrathiophene bolaamphiphiles with two lateral akyl chians can form different complex novel liquid crystalline phases,such as Colsqu/p4gm,Ncyb,Isocyb.Based on previous study,the purpose of designing 4T/n is to find the much more novel liquid crystalline phases between triangular cylinder phase and squarecylinder phase.Our study showed that only compound 4T/6 with shortest four lateral alkyl chains can form Colhex?/p6mm phase.The effect of the position and the volume fraction of alkyl chains on liquid crystalline behavior were discussed.The optical spectrum data and DFT calculation showed that these tetrathiophene bolaamphiphiles have lower optical energy gap(Egopt=eV)and there is a good intramolecular charge transfer along the ?-conjugated oligothiophene core.Chapter 3 is the experimental section including the synthetic route and spectral data.