含有不同侧链的聚降冰片烯类液晶聚合物的合成及其相结构研究

发布时间：2018-06-07 14:28

本文选题：侧链 + 液晶聚合物　；参考：《苏州大学》2016年硕士论文

【摘要】：在侧链型液晶聚合物中,侧链扮演了一个十分重要的角色,它将影响组装结构,并表达出丰富的功能性。因此本论文从侧链的分子结构设计出发,通过系统变化侧链的结构来考察侧链与主链之间的相互作用对聚合物组装结构的影响。合成了一系列以聚降冰片烯为主链,侧链包含刚性联苯结构和柔性尾链(CmBA)的液晶聚合物。具体的研究内容如下:(1)合成了一系列介晶单元个数、位置、烷基尾链长度各不相同的降冰片烯类液晶小分子单体NB-4-Cm BA,NB-3,5-CmBA,NB-3,4-CmBA和NB-3,4,5-CmBA(m=12,16),通过氢核磁共振(1H NMR)、碳核磁共振(13C NMR)以及高分辨质谱的表征验证了结构的准确性,同时通过差示扫描量热法(DSC)、偏光显微镜(POM)对单体的液晶相行为进行研究。结果表明对于同一个系列,在烷基尾链较长时,烷基尾链碳原子个数的增加可以提高清亮点(Ti)的温度;CmBA个数、取代位置的变化会较大的影响单体的相结构,形成不同的液晶织构。(2)采用三代Grubbs催化剂进行开环易位聚合反应(ROMP),得到对应的聚降冰片烯类侧链型液晶聚合物(PNB-4-CmBA,PNB-3,5-CmBA,PNB-3,4-CmBA和PNB-3,4,5-CmBA,m=12,16)。通过1H NMR、凝胶渗透色谱法(GPC)对分子结构进行了表征,热重分析(TGA)结果表明分子热稳定性较好。结合DSC、POM、小角X射线散射(SAXS)、同步辐射SAXS、二维X射线广角衍射(WAXD)研究了聚合物的相结构和相转变行为。侧链只含一个CmBA的PNB-4-CmBA表现出SmA相;当侧链含两个CmBA,且为邻位取代时,PNB-3,4-CmBA表现出具有带心长方点阵结构的受挫近晶相(Φr-c);当两个CmBA为间位取代时,聚合物PNB-3,5-CmBA不表现出液晶性;当侧链含有3个CmBA时,聚合物PNB-3,4,5-CmBA表现出六方柱状相(Φh)结构。结果表明随着侧链部分CmBA的数量增加,聚合物发生了从SmA到无定型、Φr-c再到Φh相的变化。具有刚柔嵌段结构的CmBA之间倾向于彼此平行排列,形成层状结构,而当侧链部分同时接入两个以上的CmBA后,相邻CmBA之间由于空阻的作用存在一定夹角,在一定程度上抑制了平行排列的稳定性,导致层状结构受挫;另一方面,随着侧链部分CmBA数量的增加,非极性脂肪链部分所占的体积百分含量随之增加,导致相分离界面曲率发生变化,最终形成了之前所述的相结构演变过程。(3)合成了PNB-6-3,4-CmBA(m=8,12),研究了柔性间隔基、非极性脂肪链长度变化对邻位取代双液晶基元聚合物的液晶行为的影响,DSC、POM和SAXS研究表明柔性间隔基增加后,这类聚合物仍然可形成Φr-c相,表现出邻位取代双液晶基元型侧链在聚合物形成这类特殊液晶相态时起了重要作用。采用原子力显微镜(AFM)方法研究了薄膜样品的相结构形貌。
[Abstract]:Side chain plays a very important role in the side chain liquid crystal polymer, which will affect the assembly structure and express rich functionality. Therefore, from the molecular structure design of the side chain, the influence of the interaction between the side chain and the main chain on the polymer assembly structure is investigated by changing the structure of the side chain. A series of liquid crystalline polymers with rigid biphenyl structure and flexible tail chain (CmBA) were synthesized with polynorbornene as the main chain. The specific research contents are as follows: (1) the number and position of a series of mesocrystalline units have been synthesized. The molecular monomers of norbornene liquid crystal with different alkyl tail chain lengths, NB-4-Cm BANB-3, 5-CmBABA-4-CmBA and NB-3O45-CmBAMN 1216, were characterized by 1H NMR, 13C NMRs and high resolution mass spectrometry (HRMS) to verify the accuracy of the structure. At the same time, the liquid crystal phase behavior of monomers was studied by differential scanning calorimetry (DSC) and polarizing microscope (POM). The results show that for the same series, when the alkyl tail chain is longer, the increase of the number of carbon atoms in the alkyl tail chain can increase the temperature of CmBA, and the change of substitution position will greatly affect the phase structure of the monomer. The third generation Grubbs catalyst was used to carry out ring-opening and translocation polymerization. The corresponding side chain liquid crystal polymers (PNB-4-CmBAPNB-3-CmBAPNB-3-CmBA4-CmBA and PNB-345-CmBAmB) were obtained. The molecular structure was characterized by 1H-NMR-gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) showed that the molecular thermal stability was better. The phase structure and phase transition behavior of the polymer were studied by means of DSC-POM, small-angle X-ray scattering, synchrotron radiation (SAXS) and two-dimensional X-ray wide-angle diffraction (WAXD). When the side chain contains only one CmBA, the PNB-4-CmBA exhibits SmA phase, when the side chain contains two CmBAs and is the adjacent substitution, the PNB-3PNB-34-CmBA exhibits a frustrated near crystalline phase (桅 r-che) with a central rectangular lattice structure, and when two CmBA are intersite substituted, the polymer PNB-35-CmBA does not exhibit liquid crystal properties. When the side chain contains three CmBA, the polymer PNB-3CmBA exhibits a hexagonal columnar phase (桅 h) structure. The results show that with the increase of the number of CmBA in the side chain, the polymer changes from SmA to amorphous, 桅 r-c to 桅 h phase. The CmBA with rigid and flexible block structure tends to be arranged parallel to each other and cambiform structure. However, when the side chain part is connected to more than two CmBA at the same time, there is a certain angle between the adjacent CmBA due to the effect of air resistance. On the other hand, with the increase of the number of CmBA in the side chain, the percentage of the volume of the non-polar fat chain increases. As a result, the curvature of the phase separation interface changed, resulting in the formation of the evolution process of the phase structure. The PNB-6-3 4-CmBAMN 812N was synthesized, and the flexible spacer base was studied. Effect of the length of nonpolar fat chain on the liquid crystal behavior of ortho substituted double liquid crystalline polymer the results of DSC-POM and SAXS show that the 桅 r-c phase can still be formed when the flexible spacer is increased. It is shown that the side chains of ortho substituted double liquid crystal units play an important role in the formation of such special liquid crystal phase states. The phase structure and morphology of thin films were studied by atomic force microscopy (AFM).
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O753.2;O631

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