基于四苯基乙烯发光液晶的合成、性能及结构研究

发布时间：2018-12-15 11:29

【摘要】：本文通过合理的分子设计,成功合成了一系列具有聚集诱导发光(AIE)特性的液晶分子。选择以AIE活性发光基元为核,液晶基元或多烷氧基为端基,通过改变间隔基长度、侧链数目和端基种类实现分子自组装形成AIE型发光液晶分子。文中采用了核磁共振波谱(NMR)和高分辨质谱(MS)鉴定了分子结构;采用紫外可见光谱(UV-vis)和稳态荧光光谱(PL)表征分子的光谱行为;采用差示扫描量热法(DSC)、偏光显微镜(POM)研究分子的相转变以及一维/二维广角X射线衍射(1D/2D-WAXD)确定液晶相结构。本文主要研究内容如下:1、设计并成功合成了以四苯基乙烯(TPE)为发光核,氰基联苯为液晶基元,间隔基长度和侧链数不同的一系列分子,探究其发光行为、液晶性及力致变色行为。研究结果表明,这一系列分子均具有AIE活性,但只有间隔基为12个碳长度时,连接侧链数为2和4的两个分子兼具液晶性和AIE特性,并且侧链数为4的分子能够自主装形成六方柱状相结构,在液晶相中发射较强的蓝绿色荧光,而侧链数为2的分子能自组装形成层状相结构,且液晶相发射较强的青绿色荧光。此外,间隔基为6个碳的三个分子和间隔基为12个碳且侧链数为2的分子经过力致变色现象研究,表明了结晶度的变化引起发光颜色的变化且过程是可逆的。2、设计并成功合成了一系列以共轭程度比TPE更大的1,1,2,2-四(对苯乙炔苯基)乙烯为发光核,探究了其发光行为、液晶性及力致变色行为。研究结果表明,端基为多烷氧基的分子,无论烷氧基链的长短都没有液晶性,但表现出了显著的AIE活性和力致变色室温下可逆自恢复的效应,且随着连接尾链长度的增加,自恢复速度越快,尾链长度为12个碳的分子研磨后可在25 s内自恢复。我们认为长的烷氧基尾链提供一个宽松的堆积环境,使分子容易发生堆积模式的转变,从而实现分子发光颜色在室温下发生较快的转变。但是,端基为氰基联苯和类盘状液晶基元的分子表现出了AIE特性的同时具有液晶性。其中以类盘状液晶基元为端基的分子能够自主装形成六方柱状相结构,且在液晶相中发射较强的黄绿色荧光;以氰基联苯为端基的分子能够形成扇形焦锥织构,在液晶相中发出黄色荧光。这说明了引入液晶基元确实有助于诱导扭曲的AIE核自组装形成液晶相结构,且增大中心核的共轭程度对延长发光液晶的发光波长有一定程度的贡献。
[Abstract]:In this paper, a series of liquid crystal molecules with aggregation induced luminescence (AIE) properties have been successfully synthesized by a reasonable molecular design. Using AIE active luminescent unit as nucleus, liquid crystal unit or polyalkoxy group as terminal group, the self-assembly of AIE luminescent liquid crystal molecules was realized by changing the length of spacer, the number of side chains and the type of terminal group. The molecular structure was characterized by NMR (NMR) and high resolution mass spectrometry (MS), and the spectral behavior of the molecule was characterized by UV-Vis spectroscopy (UV-vis) and steady-state fluorescence spectrum (PL). The phase transition and phase structure of liquid crystal were studied by differential scanning calorimetry (DSC) (DSC), polarizing microscope (POM) and one-dimensional / two-dimensional wide-angle X-ray diffraction (1D/2D-WAXD). The main contents of this paper are as follows: 1. A series of molecules with tetraphenylethylene (TPE) as luminescent nucleus, cyanobenzene as liquid crystal unit, spacer length and side chain number are designed and synthesized. Liquid crystal and force-induced chromotropic behavior. The results show that all of these molecules have AIE activity, but only when the spacer is 12 carbon length, the two molecules with 2 and 4 side chains have both liquid crystal and AIE properties. The molecules with side chain number of 4 can form hexagonal columnar phase structure and emit strong blue-green fluorescence in liquid crystal phase, while molecules with side chain number of 2 can self-assemble to form layered phase structure, and liquid crystal phase can emit strong turquoise green fluorescence. In addition, three molecules with 6 carbon spacers and two side chains with 12 carbon spacers were studied by force chromotropic phenomenon. The results show that the change of crystallinity leads to the change of luminous color and the process is reversible. A series of light emitting nuclei were designed and synthesized with a higher conjugated degree than TPE. The luminescence behavior, liquid crystal property and force chromotropic behavior of ethylene (p-phenylethynylphenyl) were investigated. The results show that the end group of polyalkoxy group has no liquid crystal property, but it shows remarkable AIE activity and reversible self-recovery effect at room temperature, and the length of the tail chain increases with the increase of the length of the tail chain. The faster the self-recovery rate is, the more self-recovery can be achieved within 25 seconds after grinding with 12 carbon tail chains. We believe that the long alkoxy tail chain provides a loose stacking environment, which makes the molecules prone to the transition of stacking mode, so that the color of molecular luminescence changes rapidly at room temperature. However, the molecules with terminal cyanobiphenyls and disk-like liquid crystal units exhibit both AIE properties and liquid crystal properties. Among them, the molecules with disk-like liquid crystal unit as the terminal group can form hexagonal columnar phase structure and emit strong yellow-green fluorescence in the liquid crystal phase. The molecule with cyaniphenyl as the terminal group can form the sectorial focal cone texture and emit yellow fluorescence in the liquid crystal phase. The results show that the introduction of liquid crystal unit can induce the distorted AIE nucleus to self-assemble to form the liquid crystal phase structure and increase the conjugation degree of the central nucleus to some extent contribute to the prolongation of the luminescent wavelength of the luminescent liquid crystal.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O753.2

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