【作者】 刘伟；

【导师】 杨洪；

【作者基本信息】 东南大学 ， 化学， 2017， 硕士

【摘要】 液晶弹性体是一种具有各向异性和软弹性的交联聚合物,在外界(如热、光、电场、磁场等)刺激下可以发生可逆的形变,具有独一无二的形状记忆功能。近红外响应的液晶弹性体由于其在生物领域的广泛应用前景,已经成为新的研究热点。目前科研工作者主要通过掺杂无机光热转换材料来制备近红外响应的液晶弹性体材料,但是无机光热转换材料在有机材料中分散性差,造成液晶弹性体机械性能下降和响应速度减慢等问题。本文首次选用有机共轭聚合物作为光热转换材料掺杂到液晶弹性体中,制备了单畴取向的聚苯胺/液晶弹性体复合材料,该材料稳定性高、响应近红外刺激速度快。Finkelmann的二次交联法是目前制备单畴取向液晶弹性体最为广泛的方法。但是该方法存在:反应温度高(长时间保持在60℃左右)、制备时间过长(1～2天)等缺点。为了改进该方法,本文报道了一种基于硫-烯点击化学的快速光交联两步法,该方法可以高效地制备聚硅氧烷单畴取向的液晶弹性体材料;整个制备过程在室温条件下,空气敞开体系中,用时不超过30分钟,即可将液晶小分子单体直接转化为单畴取向的液晶弹性体;该方法为目前报道过的制备方法中,能够最快得到液晶弹性体的方法。具体的研究工作内容主要分为以下两个方面:1.本文制备了一种具有光热转换效应的共轭聚合物纳米粒子(聚苯胺);选用聚甲基氢硅氧烷(PMHS)作为主链,混合单末端带烯键的液晶单体MBB和含双末端烯键的交联剂11UB,掺杂不同比例的聚苯胺,在Pt的催化条件下,采用Finkelmann二次交联法制备了聚苯胺/液晶弹性体复合材料;借助核磁共振谱(NMR)、傅里叶变换红外光谱(FTIR)、紫外-可见光吸收光谱(UV-Vis)、差示扫描量热法(DSC)、偏光显微镜(POM)、电子扫描显微镜(SEM)详细地研究了该复合材料的物理性能;通过一系列的近红外光照对比实验,研究掺杂不同含量(0.5 wt%或1.0 wt%)的掺杂态聚苯胺(ES)和本征态聚苯胺(EB)的液晶弹性体的光致形变性能。研究表明:这些共轭聚合物/液晶弹性体复合材料具有良好的光热转换效率和光致形变性能;其在近红外光的照射下发生可逆的收缩形变,可以提升自身重量200倍的物体。2.本文选用聚(3-巯丙基甲基硅氧烷)(PMMS)作为主链,混合液晶单体MBB、交联剂11UB和光引发剂安息香二甲醚(DMPA),通过控制紫外光照时间从而控制交联程度,利用硫烯点击化学分两步制备了单畴取向的聚硅氧烷类液晶弹性体薄膜;借助核磁共振谱(NMR)、傅里叶变换红外光谱(FTIR)、傅里叶变换衰减全反射红外光谱法(ATR-FTIR)、差示扫描量热法(DSC)、偏光显微镜(POM)、动态力学分析(DMA)和小角XRD散射(SAXS)详细地研究了该材料的物理性能。研究表明,该液晶弹性体膜具有优异的热致形变性能和良好的力学性能。与传统的二次交联法相比,本论文发展的新方法避免了贵金属催化剂的使用,反应时间短,反应条件温和,有利于未来单畴取向液晶弹性体材料的大规模生产,具有广阔的应用前景。更多还原

【Abstract】 Liquid crystalline elastomers(LCEs)are anisotropic,elastic,crosslinked polymeric materials,possessing a unique shape memory function that can perform reversible shape transformations under the external stimulus(such as heat,light,electric,magnetic,etc.).Recently,NIR-stimulus-responsive LCEs have become an important research topic due to its prospective applications in the biotechnology field.NIR-responsive LCEs can be prepared by doping inorganic photothermal conversion fillers.The poor dispersion of inorganic nanoparticles will inevitably weaken materials’ mechanical properties and the photo-actuation rates.In this work,we report the first example of monodomain polysiloxane-based LCE composite material by doping polyaniline nanoparticles.This material has excellent stability and photo-actuation rates.The most widely used method to prepare monodomain LCEs is a one-pot,two-stage hydrosilylation process invented by Finkelmann.But this traditional method towards monodomain LCEs requires complicated procedures,elevated reaction temperatures,and a prolonged preparation time ranging from several hours to even several days.Herein,we report an ultrafast one-pot,two-stage thiol-ene photoaddition method to synthesize monodomain polysiloxane-based LCE films.Starting from mesogenic monomers,the whole preparation process can be finished in less than 30 minutes,and all the preparation experiments are performed at room temperature,in an open air environment..This thesis can be divided into two parts:1.We first synthesize polyaniline nanoparticles which show excellent photothermal conversion efficiency.We choose polymethylhydrosiloxanes(PMHS)as the main chain,MBB as monomer,11UB as crosslinker,Pt as the catalyst to produce conjugated polymer/liquid crystalline elastomers by doping polyaniline nanoparticles and using Finkelmann two-stage crosslinking protocol.Their properties are characterized in detail by a combination of NMR,Fourier transform infrared spectra(FTIR),ultraviolet and visible spectrophotometry(UV-Vis),differential scanning calorimetry(DSC),polarized optical microscope(POM)and scanning electron microscope(SEM).A series of comparative experiments are performed to investigate the photo-responsive properties of these polyaniline/LCE samples in correspondence to the two different conjugation forms(emeralidine salt(ES)or emeralidine base(EB))and the varied doping concentrations(0.5 wt%or 1.0 wt%)of the incorporated polyaniline nanoparticles.In summary,these conjugated polymer/LCE composite materials show excellent photothermal conversion efficiency and mechanical property.Also,these LCEs can lift up materials which are ca.200 times weights compared to their own weights under the NIR illumination driving force,and such a photo-stimulated muscle-like actuation behavior is fully reversible after NIR light is removed.2.We choose poly(3-mercaptopropylmethylsiloxanes)(PMMS)as the main chain,MBB as monomer,11UB as crosslinker,benzoin dimethyl ether(DMPA)as the catalyst,using a two-step photocrosslinking method by thiol-ene click chemistry to prepare polysiloxane-based liquid crystalline polymers and elastomers.By controlling the time of the mixture under the UV irradiation,we get the pre-crosslinked polymer.The polymer main chain is aligned unixially.After a second UV irradiation for 15 minutes,the desired monodomain LCE film is prepared.We study their properties in detail by a combination of NMR,Fourier transform infrared spectra(FTIR),differential scanning calorimetry(DSC),polarized optical microscope(POM),dynamic mechanical analyzer(DMA)and small angle X-ray scattering(SAXS).The results suggest that this monodomain LCE material exhibits excellent thermoelasticity,anisotropic property and mechanical property.In comparison with the traditional hydrosilylation method which takes more than 24 hours to prepare LCEs and requires using noble metal catalyst platinum,this two-step photocrosslinking method can produce polysiloxane-based monodomain LCEs in less than 30 minutes,and all the preparation experiments are performed at room temperature,in open air.更多还原