Study On Preparation And Mechanism Of The Liquid Crystal Displays Based On 3D Gel Networks

Liquid crystal(LC)compounds have special stimuli-responsive properties towards light,electric current,magnetic field,heat etc.,and are widely used in the field of display materials.But their basic properties could not satisfy the demand of the coming new display devices.This paper took liquid crystal molecules(5CB,4'-Pentyl-[1,1'-biphenyl]-4-carbonitrile)as guests molecules,and regarded POSS-based dendrimer(POSS-G1-BOC)as gelators,and introduced photosensitizer(2Azo2,4,4'-diethoxyazobenzene)or phosphors to prepare LC physical gels with new-style stimuli-responsive properties and so on.At the same time,the paper systematically studied the relationship between structure and performance about LC gels.Meanwhile a series of LC light scattering displays with excellent performances were prepared.In addition,the 3D radially symmetrical organic-inorganic hybrid gelator POSS-G1-BOC had good gel ability and could assemble gel network structure with unique “loofah-like” morphology in normal organic solvent.The so-called “loofah-like” network was performed as a unique Y-limb,which was shown that one thick mother-fiber branches off into two relatively thin daughter-fibers.And the unique structure was truly induced by the self-assembly of gelators,and not by chance.It revolved around four aspects to spread out,which were preparations,properties,mechanisms and applications of supermolecule LC gels.Firstly,a high-performance,photo-responsive stretchable LC light scattering display based on sol-gel process was successfully prepared with LC gel(0.5wt%POSS-G1-BOC/5wt%2Azo2/5CB).The gelation behaviors,UV light responsiveness and gel network of LC gel were characterized by sol-gel transition,rotary rheometer,UV-Vis spectrophotometer and SEM.The study found that LC gel had properties of strong mechanical strength,good thermal stability,and fast UV light responsiveness and so on.And the prepared stretchable light scattering displays exhibited good stretchability at room temperature and could be clearly shown the pictorial information at strains as large as 45%.Secondly,a kind of body temperature controlled fluorescent light scattering display based on LC physical gel with special “loofah-like” gel network was successfully prepared,and it was prepared with fluorescent LC gel containing additional 5 wt% phosphors on the basis of photo-responsive LC gel.The mechanical strength of LC gel was studied by the method of tube inversion and rotary rheometer.And its fluorescence properties were studied by fluorescent spectrum and fluorescent fading rate.SEM and TEM showed that the gel network had spiral loofah-like status.The optical and thermal information storage display prepared by the LC gel showed its best contrast ratio at around human body temperature or under UV light because of the phosphors' fluorescence effect.And the display also had strong mechanical strength,even under the forcing conditions as hush as being centrifuged for 10 min at the speed of 2000 r/min in centrifuge.Thirdly,electroresponsive stretchable LC light scattering device was successfully prepared through introducing flexible conductive films(PU/AgNWs)into light scattering display device with LC gel(0.5wt%POSS-G1-BOC/5CB).Mechanical properties were studied by rheological measurements,and electrooptical properties were tested through polarizing microscopy and LCD parameter tester.The display device was prepared using flexible conductive polyurethane film as a basement and LC gel as middle layer to form sandwich structure,which could realize the high-constrast flexible display at low voltage.And the device could be stretched to 45% with its property of flexibility.Finally,the change situation of LC gels' network during LC gels'(0.5wt%POSS-G1-BOC/5CB)deformable tensile process had been studied,and “spiral dissipate energy” model was also established.Through the methods of surface morphology,XRD,microscopic mechanical analysis and self-assembly mechanism,the changes of gel network before and after being stretched were vividly shown.The whole process was functioned by hydrogen bond,and the rule between draw ratio and morphological change was good.This new stretchable gel network and its change rule might be helpful to explain and guide other changes of deformable fibers,and also played a supplementary role in the preparation of another deformable device.