长侧基甲壳型液晶高分子的合成及性质研究

设计并合成了一系列尾链为不同长度烷氧基的长侧基甲壳型液晶高分子聚[2,5-二(4 ′-烷氧基联苯氧羰基)苯乙烯]( PnCbiPCS,n=4,6,8,10,14).这些聚合物都具有良好的热稳定性.偏光显微镜及一维和二维广角X射线衍射等研究结果表明PnCbiPCS这一系列聚合物均能形成稳定的近晶A相结构,所对应的层间距随...     

含聚乙二醇柔性间隔段的主链型液晶聚酯的合成

分子结构与液晶行为间的关系是液晶性高分子物理问题研究的核心,通常的液晶性高分子中除液晶性基元外还引入一些相对来说很柔顺的链段,称作柔性间隔段．这是因为人们认识到高分子的液晶行为不只决定于液晶性基元的结构,也受到这些基元间以及基元和间隔段间相互作用的影...     

侧链胆甾液晶聚合物及弹性体的液晶性能研究

把胆甾液晶单体 4 烯丙氧基苯甲酸胆甾醇酯 (Mch)分别和向列液晶单体 4 烯丙氧基苯甲酰氧基 4′ 甲氧基苯 (Mn) ,向列液晶交联剂 2 叔丁基对苯二酚双 [4 (6 丙烯酰氧基己氧基 )苯甲酸酯 ](Mnc)接枝到聚硅氧烷链上 ,得到系列侧链液晶聚合物Pn 系列和液晶弹性体Pe 系列 .通过热分析、偏光显微分析和X 射线分析等手段分别研究了向列液晶单体和向列液晶交联剂对含同一胆甾液晶基元聚合物的影响 .结果表明 ,向列液晶单体的摩尔百分比在 80 %以下 ,液晶聚合物Pn 系列为胆甾型液晶 ,在研究的范围内 ,液晶弹性体Pe 系列也为胆甾型液晶 ,Pn 系列和Pe 系列都具有较宽的液晶相范围 ,热分解温度均在 2 80℃以上 .     

Effect of smectogenicity of the ionic groups on the thermotropic liquid crystalline behavior of pyridinium and poly(4-vinylpyridinium) salts quaternized with mesogenic groups

In order to demonstrate the important smectic power of the ionic functions present in mesogenic molecules, a series of N-alkylpyridinium bromides ω-substituted with (4-cyanobiphenylyl)oxy or [4-(2-methyl-1-butoxy)biphenylyl]oxy mesogenic group and their analogous 4-vinylpyridinium polymers were synthesized and characterized. The liquid crystalline behavior was studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Smectic mesophases, namely A, B, and E, were identified for the low molecular weight compounds, whereas smectic A and E mesophases were identified for the analogous polymers. Both structures were found to be very similar. They consist of single layers of upright molecules laterally arranged head-to-tail; the polymer backbone is inserted in between the layers. The monolayer smectic ordering observed in spite of the presence of the interacting cyano and chiral groups demonstrates the prevailing effect of the electrical interactions upon the structural organization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2569–2577, 1997     

Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers

Three series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene-1,4-di(4-iminophenoxy-n-hexanol), which also acted as a chain extender. Three diols: 1,10-decanediol,poly(oxytetramethylene) glycol (PTMEG) M _n = 1000 and PTMEG M _n = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30?50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2-ethylene glycol or 1,4-butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2-A-12 and H2-A-7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide-angle x-ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley & Sons, Inc.     

A Novel Pentaerythritol-based Carbosilane Liquid Crystalline Dendrimer Containing 12 Nitroazobenzene Groups on the Periphery

A novel liquid crystalline dendrimer with peripheral mesogenic units was successfully prepared. Azo-reaction and Williamson synthesis were employed in the preparation of the mesogenic unit 4-[4-(6-hydroxyhexyloxy)-phenylazo]nitrobenzene (M-NO2). A terminal Si-Cl functional carbosilane dendrimer based on pentaerythritol was used as dendritic scaffold and subsequently functionalized with the aforementioned groups. Investigation of the liquid crystalline properties of the mesogen-functionalized dendrimer PCSi-IG-NO2 by polarizing optical microscopy, DSC, and X-ray diffraction showed that it exhibits smectic E (SE) phase, different from the corresponding mesogenic unit, which shows nematic phase. Furthermore, the temperatures of both the melting point and the clearing point of the mesogen-functionalized dendrimer decrease, and the temperature region of the SE phase is wider than that of the nematic phase.     

Studies on thermotropic liquid crystalline polyurethanes. III. Synthesis and properties of polyurethane elastomers by using various mesogenic units as chain extender

Four series of thermotropic polyurethane elastomers (TPUEs) were synthesized in this study. The hard segments were formed by using 4,4′-methylenedicyclohexyl diisocyanate (H₁₂MDI) reacted with various mesogenic units, such as benzene-1,4-di(4-iminophenoxy-n-hexanol), benzene-1,4-di(4-iminophenol), and 3,3′-(4,4′-biphenylene)dipropanol, which also acted as the chain extender. Poly(oxytetramethylene)glycols (PTMEGs), PTMEG-2000 (M_n 2,000) and PTMEG-1000 (M_n 1,000) were used as a soft segment. The structures of all synthesized thermotropic liquid crystalline polyurethanes (TLCPUs) were characterized by FTIR spectroscopy. The effects of mesogenic units on the LC properties and elastic behaviors of LCPUs were studied. It was difficult to show LC behaviors for the PU elastomers derived from the mesogenic units with a lower aspect ratio, such as 3,3′-(4,4′-biphenylene)dipropanol, or the long soft segments, PTMEG-2000. In addition, these PU elastomers show better elastic properties by using a higher aspect ratio mesogenic unit as the chain extender, such as benzene-1,4-di(4-iminophenoxy-n-hexanol and benzene-1,4-di(4-imino-phenol)). The thermal properties were investigated by DSC measurements, thermal optical polarized microscopy, wide angle X-ray diffraction, dynamic mechanical analysis, and thermogravimetric analysis. The mechanical properties were measured by a tensilemeter. © 1996 John Wiley & Sons, Inc.     

Syntheses and properties of liquid crystalline N-substituted pyrroles and their polymers

Three liquid crystalline N-substituted pyrroles were synthesized from 6-(1-pyrrolyl)hexanol with phenolic derivatives having a mesogenic core of cyclohexylbenzene or biphenyl by Mitsunobu reaction. These pyrroles had two anodic peaks at 1.4 and 1.8 V (vs. SCE). The former was due to an oxidation of the pyrrole moiety and the latter was due to an oxidation of the mesogenic moiety. These pyrrole monomers were polymerized by electrochemical and chemical methods. The potentiostatic method and the chemical method using FeCl₃ gave a soluble and fusible polymer, respectively. A polymer having a mesogenic core of cyclohexyl benzene obtained by the chemical method and a polymer having a mesogenic core of biphenylketone obtained by the potentiostatic method had a liquid-crystalline phase. The phase was identified as smectic A by polarizing microscopy and XRD analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2691–2698, 1998     

Molecular engineering of photoactive liquid crystalline polyester epoxies containing benzylidene moiety

A series of photoactive liquid crystalline polyester epoxies incorporating bisbenzylidene segments as photoactive mesogenic cores were synthesized by polyaddition of diepoxy monomers and terephthalic acid/trimesic acid. To investigate the influence of structural parameters such as, molecular architecture, structural rigidity of mesogenic unit and substituents on thermal, mesogenic, and photoactive properties, the bisbenzylidene segment was incorporated into one acyclic and two cycloalkanone units with two and four substituents, respectively in both linear and hyperbranched architectures. Degree of branching of hyperbranched polymers was found to be in the range of 0.49–0.62. All polymers exhibited nematic mesophase (nematic droplets). Photo induced (2π + 2π) cycloaddition reaction, upon exposure to light at 365 nm, was examined. Inter molecular photocycloaddition was confirmed by photoviscosity measurement of UV irradiated polymer solutions. Faster photo induced reactivity of polymers in hyperbranched architecture was observed when compared to linear structure. Acyclic units facilitated photocycloaddition, and five‐membered ring showed higher photoactivity compared to six‐membered ring. The steric hindrance caused by substituents decreased the photoactivity of polymers. Refractive index change was found to be in the range of 0.015–0.024. Substantial variation of refractive index indicates that these polymers could be used for optical recording. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7637–7655, 2008     

Study on new chiral liquid crystalline monomers and polymers containing menthyl groups

A series of new chiral monomers (M1–M4) and the corresponding siloxane polymers (P1–P4) containing menthyl groups were synthesised to establish the relationship between their structure and liquid crystalline properties. The effect of the mesogenic core rigidity and the spacer length on the phase behaviour of the monomers and polymers obtained in this study was discussed. The selective reflection of light for the chiral monomers was studied with UV-Vis spectrometer. Polarising optical microscopy, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis were used to characterise the phase behaviour and thermal stabilities. It was found that these chiral monomers and polymers were beneficial for the formation of the mesophases when a flexible spacer was inserted between the mesogenic core and terminal menthyl groups. M1–M3 showed enantiotropic chiral smectic C phase and cholesteric phase, and monotropic cubic blue phase on cooling cycle. M4 only showed cholesteric phase. P1–P4 showed a smectic A phase. With increasing the mesogenic core rigidity or decreasing the spacer length, the corresponding melting temperatures, glass transition temperatures and isotropic temperatures all increased.     

Photoluminescence of polysiloxane containing mesogenic 4-cyanobiphenyl in solution

Photoluminescent characteristics of polysiloxane containing pendant mesogenic 4-cyanobiphenyl (CB) and its monomeric analogues were studied in THF solution. An excimer formation was observed, and the increase in CB content in polysiloxane induced the increase in the fluorescence intensity from the excimers. The fluorescence decays were analyzed by triexponential function. A high CB content induced small decay rates, indicating the decrease of nonradiational decay. Such suppression of the nonradiation decay in higher CB content was explained by a strong mesogenic interaction between CB groups in solution. © 1996 John Wiley & Sons, Inc.     

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.     

光致变色液晶高分子研究(Ⅳ)─含苯甲酸－4－甲氧基苯酯介晶基元和偶氮苯光色基元侧链共聚硅氧烷的液晶行为

用热台偏光显微镜和DSC法研究了含苯甲酸-4-甲氧基苯酯介晶基元和偶氮苯光色基元侧链共聚硅氧烷(PSⅡ)的液晶性。将非介晶基元并入液晶均聚物PSⅡ-1,共聚物PSⅡ-2、PSⅡ-3的液晶态类型不变,PSⅡ-4仅存在近晶相,PSⅡ-5～8无双折射现象,保持共聚物液晶性的最低含介晶基元单体的极限摩尔含量为80%.在液晶共聚物中,非介晶基组分含量增加时,其T_m、ΔH_m和ΔS_m降低;非介晶组分在10mol%时,T_i、ΔH_i和ΔS_i具有最小值。     

Molecular and collective relaxations of ferroelectric side chain liquid crystalline polysiloxanes

The influences of mesogenic group chemical structures on dielectric relaxation behavior were investigated for ferroelectric side chain liquid crystalline polymers (FLCPs). The relaxation time and activation energies of the Goldstone mode, α‐, and β‐relaxations decrease with increasing spacer length because of the plasticizer effect of the spacer. Moreover, the relaxation intensity increases with increasing spacer length for FLCPs. An FLCP with a longer spacer length exhibits a higher mesogenic group mobility, and subsequently leads to easier reorientation toward the alternating electrical field. An increase in mesogenic core rigidity results in an increase in the relaxation time and activation energies, and a decrease in the relaxation intensities for the Goldstone mode, α‐, and β‐relaxations. Moreover, the β‐relaxation is suppressed and cannot be observed in the glassy state for FLCPs containing naphthyl biphenylcarboxylate as the mesogenic group. Shorter relaxation time, smaller activation energies, and higher intensity of the α‐, and β‐relaxations were obtained for FLCPs containing chiral moiety with a flexible heptyl alkyl chain. However, the relaxation intensity of the Goldstone mode for FLCPs containing this chiral moiety was smaller than that for FLCPs containing the chiral moiety with a butyl alkyl chain. For FLCPs containing a chiral moiety with two asymmetrical centers, their Goldstone mode relaxation showed larger amplitude. The α‐ and β‐relaxations are suppressed for these FLCPs because of the dense packing and memory effect of the smectic phase. The relationship between the chemical structure of the mesogenic group and dielectric relaxations is discussed in great detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2035–2049, 2006     

端基含4个丁氧基苯介晶基元光致变色液晶树状物的合成、结构及液晶性研究

合成了周边含4个丁氧基偶氮苯介晶基元(M5)端基新的零代光致变色液晶树状物(D0),并用元素分析、核磁共振、基质辅助激光解吸飞行时间质谱、红外、紫外、偏光显微镜、差示扫描量热(DSC)和广角X射线衍射法(WAXD)表征.D0显示向列相,与M5相同,树状物相态由介晶基元相态所决定,D0的相行为:K138N147I145N118K.对零代(D0)、一代(D1)、二代(D2)和三代(D3)液晶树状物的清亮焓、清亮熵、熔化焓和熔化熵进行了比较.     

Novel side‐chain liquid‐crystalline polyimide for film materials

A novel side‐chain liquid‐crystalline polyimide (SLCPI) was prepared via copolycondensation from 3,5‐diamino‐benzonic‐4′‐biphenyl ester, 4,4′‐diamino‐ biphenyl ether, and 3,3′,4,4′‐oxydiphthalic dianhydride. The energy‐minimized structure and liquid crystallinity of SLCPI were investigated by molecular modeling, differential scanning calorimetry (DSC), wide‐angle X‐ray scattering, and polarized optical microscopy, respectively. The results indicated that this polyimide (PI) with side‐chain mesogenic units exhibited a nematic NI phase. Because of the in situ self‐reinforcement of side‐chain mesogenic units, the improved tensile strength and modulus of PI films reached 270% and 300%, respectively. The coefficient of thermal expansion of films decreased by 40%. DSC and thermogravimetric analyses indicated that the phase‐transition temperature of SLCPI was above 240 °C, and the 5% weight‐loss temperature was above 520 °C. Moreover, copolycondensation of two diamines with dianhydride and incorporation of pendent mesogenic units diminished the regularity and symmetry of main chains; as a result, SLCPI exhibits good film processability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 554–559, 2003     

固态后缩聚方法合成高分子量的含磷热致性液晶共聚酯

为了获得较高分子量的具有高阻燃性的热致性液晶高分子,通过固态聚合方法合成了一种基于对羟基苯甲酸、对苯二甲酸、乙二醇和含磷菲环取代二酚的高热稳定性、较低相转变温度和宽的液晶相转变温度范围的含磷液晶共聚酯(BDQTEP),并对该含磷液晶共聚酯预聚物(pre-BDQTE)在不同固态聚合条件下获得的聚合物热性能和液晶性进行了研究.对其固态反应速率控制进行了初步的探讨,当反应温度为235℃时,固态聚合反应较为理想.在聚合的初始阶段,共聚酯特性黏数[η]、黏流温度Tf和羧基浓度[COOH]均随聚合时间而明显变化,但在6 h后变化较小,几乎不变.通过固态后缩聚,将熔融聚合获得的特性黏数[η]=0.44 dL/g的含磷液晶共聚酯BDQTE的特性黏数提高了近两倍.     

Synthesis of Bis(4'-hydroxyphenyl)-toluene-2, 4-diurethane for Main Chain Liquid Crystalline Poly(urethane-ester)s

Intr0ducti0nLiquidcrystallinepoIyurethaneshaveattractedconsiderableinterestsinceIimura1andhiscoworkersobtainedtheminl98l.M0stofthep0lyurethanesthathaveappearedinliteraturewerebasedonasinglemes0gen(diisocyanateordiol),whichhadbeenreactedwith0nec0unterpart(di0l0rdiisocyanate)togiveap0lyurethane.Inprevi0usinvestigations'-',compoundsusedasmesogensallhadcompletemesogeniccores,whethertheyhadliquidcrystalpropertiesornot.Thisimpliesthatthemes0geniccoresexistedbeforetheformationoftheurethanegroupsorth…     

Liquid crystalline properties of unsegmented and segmented polyurethanes synthesised from high aspect ratio mesogenic diols

A series of novel tetrad high aspect ratio mesogenic diol monomers 4-{[4-(n-hydroxyalkoxy)-phenylimino]-methyl}-benzoic acid 4-{[4-(n-hydroxyalkoxy)-phenylimino]-methyl}-phenyl ester were prepared with varying alkoxy spacer length (n=2,4,6,8,10) by reacting 4-formylbenzoic acid 4-formylphenyl ester and 4-(n-hydroxyalkoxy) anilines. Two series of thermotropic main chain liquid crystalline unsegmented polyurethanes (PUs) were obtained by the polyaddition of the mesogenic diols with hexamethylene diisocyanate (HMDI) and methylene bis(cyclohexylisocyanate) (H₁₂MDI) in dimethylformamide respectively. The effect of the incorporation of a third component namely polyol on the liquid crystalline properties of the polyurethanes was also studied. Linear segmented PUs were synthesised by a two-step block copolymerisation method. The PUs synthesised were based on six spacer mesogenic diol chain extender, soft segments poly(tetramethylene oxide)glycol (PTMG) (M_n= 650,1000,2000) and polycaprolactone diol (PCL) (M_n=530,1250,2000) of varying molecular weights and different diisocyanates including HMDI, H₁₂MDI and methylene bis(phenylene isocyanate) (MDI). Structural elucidation was carried out by elemental analysis, fourier transform infra red (FT-IR), nuclear magnetic resonance (¹H NMR and ¹³C NMR) spectroscopy. Inherent viscosity of the unsegmented polymers measured in methanesulphonic acid at 26°C was in the range of 0.13 - 0.65 dL/g while the molecular weights and molecular weight distribution of the segmented polyruethanes was determined using gel permeation chromatography (GPC). Mesomorphic properties were studied by differential scanning calorimetry (DSC) and hot stage polarising optical microscopy and the thermal stability was determined by thermogravimetric(TG)analysis. The monomeric diols and the polyurethanes exhibited nematic texture and good mesophase stability. It was observed that the partial replacement of the mesogenic diol by the polyol of varying molecular weights influenced the phase transitions and the occurrence of mesophase textures. The phase transition temperatures of the investigated polyurethanes showed dependence on the chain length of the soft segment and on the content of the mesogen moiety. A higher content of mesogenic moiety was needed to obtain liquid crystalline property when the soft segment length was increased as observed in the case of PTMG. Grained and threaded textures were observed depending on the molecular weight of the soft segment, the mesogen content and the diisocyanate. The stress-strain analyses showed that the polymers bused on high molecular weight PTMG soft segment have elastomeric property while the PCL based PUs displayed no elastomeric property.     

SYNTHESIS OF NOVEL LIQUID CRYSTALLINE POLY(METH)ACRYLATES CONTAINING SILOXANE SPACER AND TERPHENYLENE MESOGENIC UNIT*

Novel side-chain liquid-crystalline poly(meth)acrylates were synthesized using 1-(3-hydroxyl-propyl)-3-[(4"-cyano-p-terphenyloxycarbonyl)alkyl]-1,1,3,3-tetramethyldisiloxane as the key intermediate. The polymers used a disiloxanemoiety as decoupling spacer with cyano-p-terphenyl as mesogenic unit. The products were characterized by NMR, GPC,DSC and polarizing optical microscopy. All the polymers with cyano-p-terphenyl mesogens formed a stable mesophase.However, if the mesogenic unit is replaced by cyano-p-biphenyl, the liquid crystalline character will be lost. The results alsoshowed that the decoupling is incomplete even if a complex and very flexible decoupling spacer is deliberately incorporatedto obtain the highest possible decoupling effect.