基于氢键交联的偶氮型液晶弹性体的相行为及光致形变的研究

发布时间：2018-01-03 03:08

本文关键词：基于氢键交联的偶氮型液晶弹性体的相行为及光致形变的研究　出处：《湘潭大学》2016年硕士论文　论文类型：学位论文

【摘要】：光致形变液晶弹性体材料在驱动器、人造肌肉、微流控系统等方面有着潜在的应用前景。然而,液晶弹性体材料在使用过程中,往往会造成局部缺陷将导致其在应用中其机械性能减弱。本论文中,我们采用了无规自由基聚合的方法制备了一系列以多重氢键为交联剂的具有自愈合能力的光致异构液晶弹性体。在此弹性体中,通过共聚丙烯酸丁酯调节弹性体的玻璃化转变温度,同时通过改变聚合物的主链,构筑了以丙烯酸和以甲基丙烯酸为主链的具有自愈合能力的光响应型偶氮苯液晶弹性体。1、设计合成了以丙烯酸为主链的液晶均聚物PAAZo(S1)和共聚物液晶弹性体PAAZo-co-PBA-co-HUUx(Sn,n=2,3,4,5),通过GPC和核磁积分对组分含量和分子量进行了表征,DSC、POM、1D WAXD测试表明,交联剂及丙烯酸丁酯的加入,降低了体系的玻璃化温度(Tg),对液晶的发育产生了较大的影响,液晶均聚物PAAZo(S1)常温呈现近晶B相结构,交联剂及丙烯酸丁酯的加入破坏了液晶织构的发育,且共聚物的引入阻碍了液晶基元的有序排列。流变测试表明,该系列聚合物在常温下呈现弹性的性质,损耗因子-温度的变化曲线中出现多个松弛峰,则分别代表了弹性体的玻璃化转变温度和氢键的开始逐渐解离的温度,弹性拉伸测试表明其具有优异的弹性性能,此外,光响应测试说明了其具有一定的光致形变,但其光致形变量较弱。2、在上述基础上,我们进一步设计合成了以甲基丙烯酸为主链的均聚物PMAZo(P1)和共聚物液晶弹性体PMAZo-co-PBA-co-HUUx(Pn,n=2,3,4,5),通过GPC和核磁积分对组分含量和分子量进行了表征,利用DSC、POM、1D WAXD、2D WAXD等测试方法对系列弹性体的进行了相行为和相结构表征。结果表明,交联剂及丙烯酸丁酯的加入,降低了体系的玻璃化温度(Tg),对液晶织构产生了较大的影响,但增大了液晶相畴区,并且随着氢键组分的增加,畴区大小稍有降低,此外,系列弹性体呈现近晶A相结构,流变测试表明系列弹性体动态温度与模量的变化中的模量增加过程主要是由于液晶相的发育与氢键导致的。同时,系列液晶弹性体自愈合测试表明,该系列弹性体具有较为优异的自愈合性能,愈合效率能达到92%以上,并采用了拉丝与热压两种简单的方法制备的具有自愈合能力的光致形变驱动器展示了较好的光致形变能力,同时,两种方法所制备的样品在暴露在紫外光下时,呈现了靠近光源弯曲和远离光源弯曲两种不同的形变现象,最后,利用了2D WAXD对其产生不同结果的机理进行了研究,结果表明:两种相反的实验现象是由于液晶基元的在分子内的排布不同导致的。
[Abstract]:Photodeformed liquid crystal elastomer materials have potential applications in actuators, artificial muscles, microfluidic systems and so on. However, liquid crystal elastomer materials are used in the process of application. Often cause local defects will lead to its mechanical properties in the application of weakened. In this paper. A series of photoisomerized liquid crystal elastomers with self-healing ability using multiple hydrogen bonds as crosslinkers were prepared by random radical polymerization. The glass transition temperature of the elastomer was adjusted by copolymerization of butyl acrylate and the main chain of the polymer was changed. A photo-responsive azobenzene liquid crystal elastomer with self-healing ability was constructed with acrylic acid and methacrylic acid as the main chain. The liquid crystal homopolymer PAAZoS1 with acrylic acid as the main chain and the copolymer liquid crystal elastomer PAAZo-co-PBA-co-HUxUxHXUxUxHXUxUxS1) were designed and synthesized. The content and molecular weight of the component were characterized by GPC and NMR integral. The results of WAXD test showed that the crosslinking agent and butyl acrylate were added. The glass transition temperature (TG) of the system was reduced, which had a great influence on the development of liquid crystal, and the liquid crystal homopolymer PAA Zos _ 1 showed a near-crystalline B phase structure at room temperature. The addition of crosslinking agent and butyl acrylate destroyed the development of liquid crystal texture, and the introduction of copolymers hindered the ordered arrangement of liquid crystal units. Rheological tests showed that the series of polymers showed elastic properties at room temperature. There are several relaxation peaks in the curve of loss factor-temperature, which represent the glass transition temperature of elastomer and the temperature at which the hydrogen bond begins to dissociate gradually. The elastic tensile test shows that it has excellent elastic properties. In addition, the photo-response test shows that it has some photo-induced deformation, but the amount of photo-deformation is relatively weak, on the basis of above mentioned. We further designed and synthesized the homopolymer PMAZo-P1 with methacrylic acid as the main chain and the copolymer liquid crystal elastomer PMAZo-co-PBA-co-HUxUxUxUxUxUxUxUxUxUxUxUxUxPnO2. The content and molecular weight of the components were characterized by GPC and NMR integration, and the DSC-POM1D WAXD was used. The phase behavior and phase structure of the elastomers were characterized by 2D WAXD and other methods. The results showed that the glass transition temperature was decreased by adding crosslinking agent and butyl acrylate. The liquid crystal texture was greatly affected, but the liquid crystal phase domain region was increased, and with the increase of hydrogen bond composition, the domain size decreased slightly. In addition, the series of elastomers showed a near-crystalline A phase structure. The rheological tests show that the increasing process of moduli in the dynamic temperature and modulus of series elastomers is mainly due to the development of liquid crystal phase and hydrogen bond. Meanwhile, the self-healing test of series liquid crystal elastomers shows that the increasing process of modulus is mainly due to the development of liquid crystal phase and hydrogen bond. The series of elastomers have excellent self-healing performance and the healing efficiency can reach more than 92%. The photodeformed driver with self-healing ability prepared by two simple methods of wire drawing and hot pressing showed good photodeformability. At the same time, the samples prepared by the two methods were exposed to ultraviolet light. There are two different deformation phenomena: bending near the light source and bending away from the light source. Finally, the mechanism of the different results is studied by 2D WAXD. The results show that the two opposite experimental phenomena are due to the different arrangement of liquid crystal units in the molecule.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O631

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