Study On Preparation And Properties Of Laser Blinding Protection Materials Based On Liquid Crystals

Lasers have been widely applied in medical,industrial and military fields and bring enormous convenience to people' life.However,potential hazards may be caused and lead to extensive damages in human eyes,photoelectric sensors,optical systems and satellites.Therefore,development of high-performance laser protection system has become a hotspot topic for researchers.Typically,laser protection technology is classified into two types:linear and nonlinear protection.However,some bottlenecks such as complex fabrication process,high cost,low transmittance(in linear protection)and inferior solubility of materials,liquid disperse media with poor practicability(in nonlinear protection),still remain and severely hamper their practical applications.In light of these deficiencies,this thesis aims to develop a novel laser protection system that integrates excellent protective effect,good processibility and cost-efficiency simultaneously from the three aspects of material synthesis,system preparation,and effect improvement.The main research contents are listed as follows:(1)A series of mesogenic dichroic anthraquinone dyes with different structures have been elaborately designed and synthesized.It is found that adjustments of the conjugation length and lateral substituents are effective ways to modulate the optical property of the dyes from the molecular level.The prepared anthraquinone dyes can collectively shield the light in a wide range of 200-500 nm.This series of dyes are all mesogenic in a wide temperature range.Meantime,these dyes exhibit excellent dichroic properties that the dichroic ratio is as high as 13.26,which is in the top level of the dichroic anthraquinone dyes reported so far.(2)A novel dichroic anthraquinone dye-cholesteric liquid crystal composite laser protection system is prepared by doping the anthraquinone dyes with different structures into the cholesteric liquid crystals.It is found that this composite system is a high-performance laser protection approach that integrates high optical density,good visibility,angle-independence,good processibility,cost-efficiency and tunable wavelength simultaneously.The dichroism of the doped dyes plays a key role in the elimination of the angle-dependency problem of cholesteric liquid crystals.The protective effect of this composite protection system is controllable that increasing the doped dye concentration,sample thickness and cholesteric liquid crystal reflection efficiency can improve the optical density values.(3)Mesogenic[60]fullerene derivatives with different structures have been designed and synthesized.It is found that functionalization of the C60 core with a mesomorphic framework via Bingel reaction is an effective way to obtain mesogenic[60]fullerene derivatives.The prepared fullerene derivatives with different branch structures(azobenzene and biphenyl)both exhibit mesogenic properties in a wide temperature range.Furthermore,the azobenzene derivative is also endowed with the photo-responsive property.The prepared fullerene derivatives both display superior solubility characteristics that in E7,an enhancement of solubility as high as 200 time-of-magnitude is obtained compared with pristine C60.(4)A high-performance laser protection system of fullerene-cholesteric liquid crystals based on the nonlinear/linear dual-mechanisms is prepared by doping the mesogenic fullerene derivatives with different branch structures into the liquid crystal matrix.It is found that this composite system integrates excellent optical limiting response,broadband protection range,good visibility,good processibility,and high practicability simultaneously.These two fullerene derivatives both display reverse saturable absorption and self-defocusing behaviors,and show 17 time-of-magnitude enhancements of the nonlinear susceptibility compared with pristine C60.The azobenzene fullerene is photo-responsive and endowed with photoswitching-induced modulation of nonlinear optics.This composite system can shield broadband IR laser of 1040-1905 nm with optical density of 2.0.Moreover,the samples have advantages of flexibility and shape diversity with greater practicability than those dispersed in liquid media.(5)A novel composite laser protection system of Fe3O4 nanoparticle-cholesteric liquid crystals is prepared.It is found that this composite system is a high-performance protection approach that integrates infrared broadband reflection and controllable temperature under high-frequency electric field.This composite system exhibits electromagnetic-thermal effect,which is controllable by the factors of the doped Fe304 concentration and the applied electric field parameters(duration time,magnitude and frequency).Hence,besides the broadband infrared laser protection,this composite system has electromagnetic-thermal effect which may melt off the frost and snow attached on the protection glass under low temperatures for high transmittance and good safety.