【作者】 李洁；

【导师】 郭金宝；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2019， 硕士

【摘要】 液晶纳米粒子(LCNPs)是纳米尺度上的多功能液晶材料。液晶的取向行为、刺激响应性(包括电场、磁场和光)以及纳米胶体中分子有序性,使这类材料在生物医学和光学方面具有巨大潜力。本研究中,利用细乳液聚合机理制备了一种具有可逆光调控性能的荧光液晶纳米粒子,并对纳米粒子的形貌及光调控性能进行研究。进一步利用喷墨打印技术使其图案化,研究其在信息加密及荧光防伪领域的应用。首先,设计并制备了一种新颖的可聚合氰芪荧光单体,将其与二芳基乙烯光敏分子一起引入到可聚合液晶单体中,采用乳液热聚合法制备了一种具有可逆光调控性能的荧光液晶纳米粒子。研究表明,二芳基乙烯组分比例的增加使得光调控性能的对比度增加但对纳米粒子成型有不利影响,而液晶单体量的少量增加对粒子成型有稳定作用。系统研究后确定了合适的组分比例制备出了可均匀分散在水相体系中、粒径约为120 nm接近单分散的球形LCNPs。其次,对LCNPs光调控性能进行了系统研究,LCNPs在365 nm紫外光的激发下发出510 nm的绿色荧光,由于荧光单体与二芳基乙烯分子之间的能量共振转移效应,该荧光会在较强的紫外光(2wm/cm2)曝光70s后有88.2%的降低,并在可见光曝光30s后完全回复到初始荧光强度。同时经过多次曝光循环后荧光强度也未有损失迹象。同时,基于荧光纳米粒子配制了水溶性的荧光墨水,采用喷墨打印得到的荧光图案在可逆光调控过程具有可见光下“显性/隐形”以及365 nm紫外光下“ON/OFF”的效果。具有这种光调控特性的荧光阵列在信息加密和防伪领域具有潜在的应用价值。最后,用LCNPs进行细胞荧光染色,发现LCNPs能经细胞吞噬作用顺利地进入细胞中,具有极低的生物毒性。本工作对于液晶纳米材料的制备及功能化研究开辟了新的思路,且为这类材料在在生物荧光标记、信息显示和记录领域的应用提供重要参考价值。更多还原

【Abstract】 Liquid crystal nanoparticles(LCNPs)is a kind of multifunctional liquid crystal materials on the nano scale.The liquid crystals’orientation behavior,stimuli responsiveness(including electric fields,magnetic fields,and light)and fixed orientation in LCNPs make it a great potential for biomedical and optical applications.In this work,we prepared a kind of photoswitchable fluorescent liquid crystal nanoparticles by the miniemulsion polymerization technique,and some studies on morphology and photoproperties of fluorescent LCNPs were carried on.And it is further patterned by inkjet printing technology to study its application in information encryption and fluorescent anti-counterfeiting.Firstly,we designed and successfully prepared a novel polymerizable dicyanodistyrylbenzene-based fluorescent monomer.Then it was introduced into the polymerizable liquid crystal monomer together with the diarylethene(DAE)photosensitive molecule to prepare a kind of photoswitchable fluorescent LCNPs by the miniemulsion polymerization technique.Studies have shown that the increase of the proportion of DAE increases the contrast of the photoswitch property but has an adverse effect on the LCNPs formation,and a small increase in the ratio of the liquid crystal monomer can stabilize the particles formation.So a suitable proportion of components was finally determined to prepare the water-dispersed,uniform spherical LCNPs with the diameter of 120 nm.Next,some studies on photoswitchable fluorescent properties of LCNPs were carried on.The LCNPs have a bright green fluorescent at 510 nm excitated by 365 nm UV light.Especially,the intensity of florescent of LCNPs have a 88.2%reduction after irradiation of UV(365 nm,2wm/cm2)for 70s,and returned to initial fluorescence intensity after visible light exposure for 30s,as a result of fluorescence resonance energy transfer(FRET)in DAE derivatives and dicyanodistyrylbenzene-based fluorescent monomer.It was identited that there was no loss of fluorescence intensity after many cycles of exposure.And a water-soluble fluorescent ink is prepared based on fluorescent LCNPs and then ink-jet-painting was introduced to prepare the fluorescent patterns on the substrate.The fluorescent patterns show a a dynamic photoswitch progress of "visible/invisible" under visible light,and fluorescent "ON/OFF" under UV light.The fluorescent arrays with such photoswitchable properties have potential applications in the field of information encryption and anti-counterfeiting.Finally,the cells were fluorescently stained with LCNPs,it was found that LCNPs can enter the cells through cell phagocytosis,have extremely low biotoxicity.This work has opened up new ideas for the preparation and functionalization of liquid crystal nanomaterials,and provides important reference value for the application of such materials in the field of biological fluorescence imaging,information display and recording.更多还原