Dissertation > Mathematical sciences and chemical > Crystallography > Amorphous and class crystalline > Class crystalline > Liquid crystal

Synthesis and Properties of Novel Bent-core Nematic Liquid Crystal with Ether

Author DuQiong
Tutor ZhangKaiCheng; ZhangZhiYong
School Wuhan Polytechnic University
Course Applied Chemistry
Keywords bent-core ether nematic liquid crystals synthesize difluorooxy-methylene-bridged low melting point low nematic temperatures wide nematictemperature range
CLC O753.2
Type Master's thesis
Year 2012
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Liquid crystal display has become the mainstream of flat-panel displayindustry.The present rod-like (unixial) liquid crystal materials possess theproblem that the response speed is not fast enough either at room temperature orlow temperature that has not been resolved,so the application is restricted in theoutdoor.The bent-shaped liquid crystal discovered in recent years is a new kind ofliquid crystal with special electro-optical properties,which has become a mewbranch of thermotropic liquid crystal after the rode-like and discotic liquidcrystal. Moreover, as the obvious characteristics different from rod-like anddiscotic liquid crystal and potential value in planar display device and other fields,it has already caused the wide attention.However,these molecules with bent-corenematic phase based on the substituted resorcinol,oxadiazole etc as the central unitand-COO-,-C=N-,-N=N-etc as the bridge bonds commonly have high meltingpoint,wide temperature range of smetic phase,narrow nematic temperature rangeand high nematic temperature which hindered the properties and applicationresearch of bent-core nematic liquid crystal.Designing and synthesizing novelbent-core liquid crystal possessing low melting point and visicosity,low transiationtemperature and wide range of nematic phase is one of the key processes thatpromote the development of flat-panel display techniques.In this paper,we designed and synthesized5PE-(3F)ODBP,mBn-ODBP,mBn-3FODBP, mP-CF2O-ODBP and mP-CF2O-2FODBP five series of26newtarget compounds with1,3,4-oxadiazole,all of them have not been reportedyet.Structures of the titled compounds were confoirmed by IR,1HNMR,13CNMR,19FNMR and MS techniques,their transition temperatures and phase transition wereinvestigated using differential scanning calorimetry (DSC)and polarizing opticalmicroscopy(POM);influences of different bridge bondings(-COO-,-CH2O-,-CF2O-)and lateral fluorine substitution on the nematic liquid crystal behavior were given.It was found that difluorooxymethylene-bridged bent-core liquid crystalpossessed low melting point and nematic temperatures,and exhibited wide nematictemperature range;the melting point could be decrased by introducing lateralfluorine.

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