含不同柔性链的(甲基)丙烯酸酯类液晶高分子的合成及其液晶行为研究

通过改变侧链中柔性间隔基的长度,合成了一系列含有两个手性中心的侧链液晶（甲基）丙烯酸酯类聚合物.红外、核磁和GPC表征各中间体、单体及聚合物的结构和分子量.通过DSC和热台偏光显微镜系统地研究了单体和聚合物的液晶态织构.结果表明,含有六个碳的柔性间隔基的丙烯酸酯类聚合物表现为近晶SA和手性近晶SC^＊液晶相.     

具有不同柱状结构的苯并菲盘状液晶化合物的合成及自组装

合成了3种含有不同长度烷基链的苯并菲盘状液晶化合物; 通过1H NMR 和 MALDI-TOF MS对其结构进行了表征; 利用差示扫描量热法(DSC)、热台偏光显微镜(POM)和小角X射线散射实验(SAXS)对3种液晶化合物的自组装行为进行了研究. 结果表明, 烷基链的长度对苯并菲盘状液晶化合物自组装结构的影响显著. 柔性链为辛基的苯并菲盘状液晶化合物自组装成六方柱状液晶相; 柔性链为十二烷基的化合物自组装成倾斜柱状液晶相; 而柔性链为十六烷基的化合物则未形成液晶相.     

点击化学合成盘-棒-盘状液晶三聚体

本文设计并合成了一系列盘-棒-盘状液晶三聚体.此类三聚体由两个相同的苯并菲盘状介晶基元和一个联苯棒状介晶基元通过CuI-NEt3体系催化端基炔和端基叠氮化合物的点击反应连接形成.该三聚体结构通过核磁、红外和高分辨质谱表征;介晶性通过偏光显微镜(POM)、差示扫描量热法(DSC)和X射线衍射(XRD)进行了研究.结果显示:此类液晶三聚体均为室温液晶,呈现四方柱状相(Colr).连接3个介晶基元的柔性间隔基的长度对化合物的相转变温度具有明显影响.     

侧基甲壳效应和甲壳型液晶高分子

侧链液晶高分子体系里,液晶基元可以通过尾接或腰接的方式与主链相连.一般认为,在液晶基元与主链间插入一段长度合适的＂柔性间隔基＂可有效实现主、侧链间的动力学去偶合,从而有利于侧基液晶基元之间的有序排列.作为一类特殊的腰接型侧链液晶高分子,甲壳型液晶高分子中体积较大的侧基（如棒状液晶基元）通过非常短的间隔基或仅通过一个碳-碳键直接横挂至主链上,这导致了强烈的甲壳效应,使得主链被迫伸展.因此,可从与＂柔性间隔基＂完全不同的角度出发,充分利用主链和侧基间的偶合作用,设计甲壳型液晶高分子.本文综述了腰接型侧链液晶高分子中的侧基甲壳效应、甲壳型液晶高分子中由主链与侧基相互作用所导致的特殊构象以及液晶相结构.研究表明,侧基甲壳效应在调控甲壳型液晶高分子的形状、尺寸以及螺旋结构等方面有重要作用.甲壳型液晶高分子可作为刚-柔嵌段共聚物的刚性链段,也可作为主/侧链结合型液晶高分子的主链部分参与到多层次分级超分子有序结构的构筑之中.     

含联苯结构侧链液晶聚合物的合成及相行为的研究

液晶聚合物从结构上可分为3种:侧链型、主链型和主侧链型。侧链型液晶聚合物主要是聚丙烯酸酯类、聚硅氧烷类以及磷腈聚合物类。Gray等对聚丙烯酸酯类含不同取代基的联苯结构液晶聚合物进行了研究,结果表明无间隔基且取代基为氰基和饱和脂肪基时,该聚合物呈现近晶型液晶行为。为了增加介晶单元的长径比及刚性,本文在聚甲基丙烯酸酯侧链     

液晶二聚体

液晶二聚体作为半柔性主链型液晶聚合物的简化模型, 通过对其液晶性质的研究, 有助于理解更复杂聚合物体系的液晶行为. 另外, 液晶二聚体作为一类特殊的液晶也有其自身的相结构和相行为. 以分子结构与液晶态的相互关系为主线, 系统介绍了目前文献报道的对称及非对称棒状液晶二聚体(线形、H形、U形、T形)、盘状液晶二聚体(对称的盘-盘状液晶二聚体和非对称的盘-棒状液晶二聚体)和香蕉形液晶二聚体(对称的香蕉-香蕉形液晶二聚体和非对称的香蕉-棒状液晶二聚体)等各种不同类型的液晶二聚体的研究进展, 以期为新型液晶二聚体的分子设计提供一些借鉴.     

含1,3,4-噁二唑甲壳型液晶聚合物的合成与表征

甲壳型液晶聚合物（mesogen-jacketed liquid crystal polymer,MJLCP）是1987年由周其凤教授[1]首先提出的概念.从化学结构看,甲壳型液晶聚合物属于侧链型,由烯类单体经链式聚合制得,容易得到高分子量的产物,具有一般柔性侧链型液晶聚合物的一些优点.但是与柔性侧链型液晶聚合物不同的是,MJLCP分子中的刚性液晶基元是通过腰部或重心位置与主链相联结的,在主链与刚性液晶基元的侧基之间只有很短或者没有柔性间隔基.由于在这类液晶聚合物的分子主链周围空间内刚性液晶基元的密度很高,分子主链被由液晶基元形成的外壳所包裹并被迫采取相对伸直的刚性链构象.因此,这类液晶聚合物又和主链型刚性链液晶聚合物相似,具有较明显的链刚性.近年来,周其凤课题组围绕甲壳型液晶聚合物深入开展了分子设计与合成、分子结构与性能等多方面的研究.其中,设计合成具有特定功能的甲壳型液晶聚合物是在以往研究工作和学科交叉融合的基础上发展起来的一项新的研究工作.将一些有特殊功能的基团引入到甲壳型液晶聚合物中会使其具有崭新的特性.     

梳状聚合物研究进展

梳状聚合物是一类具有高接枝密度的接枝型共聚物。由于高密度接枝的侧链之间相互排斥,导致梳状聚合物主链被迫伸直,整个梳状聚合物表现出棒状构象。同时,相比于一般线形聚合物而言,梳状聚合物分子量较容易达到很高,形成几十到上百纳米尺寸的结构,因此有着广泛的应用前景。目前,人们对于梳状聚合物的研究集中于其合成、结构以及性能等领域,其中主要基于对柔性侧链、柔性主链梳状聚合物的研究。本文对于梳状聚合物的合成、刚性主链和刚性侧链梳状聚合物发展现状以及梳状聚合物的性质和应用进行了总结。     

液晶性9-苯亚甲基取代芴-苯共聚物的设计合成及催化剂对聚合物链立构规整性、液晶性和光学性质的影响

为了制备适于制造有机发光场效应管的高分子材料, 通过Suzuki偶联反应, 采用不同Pd催化剂, 合成了一种侧基横挂偶极基团的液晶9-苯亚甲基取代芴-苯共聚物. 考察了不同催化剂对合成的聚合物的分子量、聚合物链中单体单元的结构排列及液晶性质和光学性质的影响. 结果表明, 2种不同的Pd催化剂对合成的聚合物的分子量影响不大, 但对聚合物链的立构规整性以及聚合物的液晶态温度范围有较大的影响. Pd(PPh3)4作催化剂合成的聚合物(PA)中单体单元的结构排列较单一, 立构规整性好, 有较宽的液晶态温度范围. Pd(OAc)2为催化剂合成的聚合物(PB)链中单体单元的结构排列相对复杂, 液晶态温度范围较窄. 聚合物链的立构规整性对其光学性质影响很大. PA具有较高的溶液及固体膜的紫外最大吸收峰值和溶液荧光效率, 其退火膜的激发和发射光谱的半峰宽均比PB的窄, 并且光学性质不随加热条件的变化而变化.     

用环氧乙烷低聚物为柔性间隔的手性侧链液晶高分子的合成

本文用乙氧基做为主链与侧链的柔性间隔，合成了手性侧链液晶高分子．通过ＤＳＣ，热台偏光显微镜及Ｘ－衍射等手段，研究了柔性间隔链长对液晶行为的影响．结果表明，这类液晶高分子有较宽的相变温度范围．聚合物的相变温度及液晶态的形成与柔性间隔链长有关．     

Multiple Effects Tailoring the Self-organization Behaviors of Triphenylene Side-chain Liquid Crystalline Polymers <Emphasis Type="Italic">via</Emphasis> Changing the Spacer Length

Long-alkyl tail triphenylene (TP) side-chain liquid crystalline polymers (SCLCPs) with different spacer length (P-m-TP,m =2,3,4,6,8,which is the number of carbon atom in the flexible alkyl spacers) have been successfully synthesized via free radical polymerization.The differential scanning calorimetry (DSC),polarized light microscopy (POM),ultraviolet-visible spectroscopy (UV-Vis),wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements were performed to investigate the influence of multiple effects on the self-organization behaviors of P-m-TP,including steric effect,decoupling effect and π-π stacking effect.The experimental results revealed that P-m-TP (m =2,3,4) formed the columnar phase which was developed by the TP moieties and the main chain as a whole,suggesting that the side-chains had strong steric effect even though the number of spacer length (m)exceeded 4.In addition,the clearing points (Tis) of the polymers were above 300 ℃.When m =6 and 8,the polymers displayed hexagonal columnar phase and exhibited the low Tis (91 and 80 ℃ respectively),originating from the self-assembly of triphenylene due to the decoupling effect and π-π stacking effect.This work offers a viable and inspiring pathway to control the phase transition temperature and phase structure of TP SCLCPs via simply tailoring the spacer length and increasing the alkyl tail length of TP.     

Controlled synthesis and microstructure tuning of PEG‐containing side‐chain discotic liquid crystalline block copolymers via RAFT polymerization

Liquid crystalline block copolymers (LCBCPs) are fascinating for their combining molecular level liquid crystalline orders and microphase separated multidomain morphologies. Here in this article, a series of PEG‐containing side‐chain discotic LCBCPs of PEG‐b‐P_m‐n with variant spacer length m = 6, 10 and degree of polymerization (DP) of discotic LC block from n = 10 to 45, have been well‐synthesized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The RAFT process mediated by macromolecular chain transfer agent (macroCTA) shows remarkable monomer concentration dependence. The influence of the introduced PEG block on the nano‐scale microphase‐segregation and mesophase organization is closely related to the side‐chain triphenylene (TP) discogens stacking mode dependent on the spacer length. Wherein, the PEG‐b‐P₆‐n series with a six‐methylene spacer exhibit consistent microphase separation with slightly disturbed yet ordered columnar structures. While for PEG‐b‐P₁₀‐n series with a longer ten‐methylene spacer, the columnar organization in the copolymers is even improved in contrast with the low order of randomly TP stacking in their corresponding homopolymers. This work offers a viable and inspiring pathway for controlled synthesis of block copolymers with bulky side groups, as well as enhances in‐depth understanding of the hierarchical superstructure organization in discotic units involved complex block copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2544–2553     

Influence of main chain on the phase behaviors of side-chain liquid-crystalline polymers with triphenylene mesogens of long alkyl tail substituents

A series of side-chain liquid-crystalline polymers (SCLCPs) containing triphenylene mesogen, in which the long alkyl tail Tp connected directly with main chain, were synthesized successfully. The chemical structures of the monomers were confirmed by ¹H NMR and mass spectrometry. The phase behaviors of polymers were investigated by a combination of techniques, including DSC, POM, 1D/2D WAXD, and SAXS. The experimental results suggested that the type of main chain played an important role in the LC phase structures of these polymers. Because of the steric effects of side chains and the coupling effects between the Tp moieties and the main chains, all the polymers exhibited columnar phase. However, the SCLCPs with poly(vinyl benzene methyl ether) or polynorbornene backbone displayed hexagonal columnar phase, while those with polyacrylate or polymethacrylate backbone presented columnar nematic phase, and the one with poly(vinyl benzoate) main chain showed rectangular columnar phase. Moreover, the clearing temperatures (Ti) changed with change in main chain. Especially, the Ti of the SCLCP with polymethacrylate backbone was above 300 °C. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 754–766     

Liquid Crystalline Polymers

History of Liquid Crystalline PolymersThe liquid crystalline(LC)state was first observed by Austrian botanist and chemist F.Reinitzer more than a century ago,and it was then confirmed in 1888 by German physicist O.Lehmann who named such a state of matter as"liquid crystal"in 1900.While low molecular mass(LMM)liquid crystals were successfully used in LC displays(LCDs),the development of LC polymers(LCPs)followed an independent path.Conceptually,LCPs are prepared with the incorporation of mesogenic groups that are responsible for the formation of LC mesophases,such as rod-like(calamitic)and discotic ones,into polymer chains.Depending on where the mesogens are attached,traditionally there are three major categories of LCPs.Main-chain LCPs(MCLCPs)have mesogens in the polymer backbone,while mesogens of side-chain LCPs(SCLCPs)are incorporated as side groups in a polymer with a relatively flexible main chain.In main-chain/side-chain combined LCPs(MCSCLCPs),mesogens are in both the backbone and side chains.Other classes of LCPs include mesogenjacketed LCPs(MJLCPs),dendronized LCPs,and LC networks(LCNs).     

Molecular dynamics of discotic charge-transfer complexes, dielectric spectroscopy and 2H NMR studie

Using a combination of solid state ²H NMR spectroscopy on selectively deuteriated samples and dielectric spectroscopy, the molecular dynamics of discotic charge-transfer (CT) complexes were investigated. These complexes show particular thermodynamic and flow properties. Considered were mixtures of low molar mass donors and acceptors, low molar mass donors with main chain acceptor polymers and covalently linked donor-acceptor twins with different lengths of the spacer. A main result is that correlated rotational motions of discotic molecules or groups about the columnar axis are observed in all systems except for the twin with the short spacer. This type of motion seems to be a general feature of columnar phases. The non-discotic acceptor which is incorporated in the columns participates in this motion. The twin possessing a long spacer displays at high temperatures an additional process: it performs a diffusion process between the columns. A further result is that broad biphasic regions exist in CT mixtures at the transition from the discotic to the isotropic state.     

Discotic liquid crystals: a new generation of organic semiconductors

Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given.     

基于不同间隔基的含三联苯甲壳型液晶聚乙炔的合成与性能研究

设计并合成一类含三联苯液晶基元的甲壳型液晶聚乙炔(-{HC=C-[(CH2)mOOC-terpheyl(OC6H13)2]}n-,m=5,PHA5TP(OC6)2;m=9,PHA9TP( OC6)2),研究了聚合物的热稳定性、液晶性能和发光性能,考察了间隔基的长度对其性能的影响.结果表明,三联苯液晶基元赋予单体和聚合物...     

Radical polymerization behavior and molecular weight development of homologous monoacrylate monomers in lyotropic liquid crystal phases

Polymerization in highly ordered lyotropic liquid‐crystalline (LLC) media enables controllable synthesis of polymers possessing interesting nanostructure and physical properties. This study investigates the radical polymerization rate and molecular weight (MW) development of monoacrylates of different aliphatic tail length in a range of LLC phases. Polymerization rate data were acquired using photodifferential scanning calorimetry, and linear polymer MW was determined with gel permeation chromatography. Polymerization occurs much more rapidly, and higher MW is attained in the ordered LLC phases relative to isotropic solutions and neat polymerization. These properties change significantly as a function of LLC phase and monomer structure. A direct relationship is observed between polymer MW formation and the polymerization rate. Definitive changes in rate and MW were observed at phase boundaries, indicating the important role of solvent order. This study demonstrates how solvent ordering effects can be used to control polymer MW and rate of polymerization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 144–154     

Investigations of comblike polysiloxanes. I. The influence of spacer length on dielectric relaxation studies of aligned samples

Dielectric relaxation studies on aligned liquid-crystalline comblike polysiloxanes are presented. The polymers differ only in the length of the flexible spacer separating the mesogenic side groups from the polysiloxane backbone. The characteristic features of the observed relaxation process as a function of frequency and temperature, in both the liquid-crystalline and isotropic phases, are described, and the effect of the spacer length is discussed. Within the liquid-crystalline phase a narrow single loss process is observed, due to the relaxation of the mesogenic side groups around the polymer backbone, whereas in the isotropic phase a much broader loss curve is seen. The transition from an aligned polymer mesophase to the randomly aligned isotropic phase is also studied in detial, and comparison with earlier work on comblike polyacrylate and methacrylate liquid crystals is presented.     

SYNTHESIS AND PROPERTIES OF NEW MESOGEN-JACKETED LIQUID CRYSTALLINE POLYMERS*

Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, andmesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of thesepolymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Theirliquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. Theresults show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2)a flexible spacer will decrease the "Jacket Effect" and the liquid crystallinity and 3) a subtle modification of the terminalgroups on the mesogenic unit may also have a significant influence on properties of the polymers.