高性能工程塑料——液晶聚合物

介绍了液晶聚合物作为优异工程塑料的发展概况,叙述了热致性液晶聚合物的优异性能、合成及加工方法,提出了热致性液晶聚合物可通过与填料、纤维掺混或分子工程得到自身增强。并叙述了近年来国外开发热致性液晶聚合物新品种的方向。     

高性能聚芳酯纤维的研制和表征

介绍了热致性液晶聚芳酯纤维的制备。选用双酚A、对苯二甲酸、间苯二甲酸为单体进行熔融聚合,制得具有不同相对分子质量的双酚A-对/间苯二甲酸共聚酯,探索了后续固相聚合工艺,研究了后续固相聚合对原熔融聚合物相对分子质量、热性能以及力学性能的影响。原聚合物再经固相聚合及不经固相聚合的两种聚芳酯在不同的纺丝和热处理工艺条件下,可以获得力学性能相近的聚芳酯纤维,为进一步研制热致液晶型聚芳酯纤维生产路线提供可靠的工艺数据。     

热致性液晶聚合物改性环氧树脂的研究进展

本文介绍了热致性液晶聚合物的结构、性能及其应用,在理论上阐述了热致性液晶聚合物改型环氧树脂的机理,介绍了国内热致性液晶聚合物改性环氧树脂的研究进展。     

共聚芳酯的合成及其液晶性能研究

本文是合成并研究带有酯基的热致性液晶共聚芳酯,该共聚芳酯液晶聚合物具有高强度、高模量的特性。以对羟基苯甲酸、双酚A、对苯二甲酸为基体原料,先分别以前两种基体原料各别制得对乙酰氧基苯甲酸、双酚A醋酸酯,再与对苯二甲酸以熔融缩聚反应制备共聚芳酯。对熔融缩聚反应条件进行讨论,用X衍射、DSC对其结晶性、熔点等进行表征,并作了热台偏振显微镜观察、摄相。结果表明:合成所得的共聚芳酯具有良好的结晶性,为热致性液晶聚合物,液晶熔程较宽,利于在液晶态下熔融成型加工。     

热致性液晶聚合物种类对环氧树脂性能的影响研究

利用自行合成的多种热致性高分子液晶聚合物对CYD -12 8环氧树脂进行共混改性 ,用FTIR方法研究了液晶聚合物对环氧树脂固化反应程度的影响 ,用DSC、TGA研究了液晶聚合物对环氧树脂固化物Tg 和热失重温度的影响 ,测试了共混物的力学性能 ,并用扫描电镜观察了共混物冲击断面的形貌。结果表明 :端基含有活性反应基团的液晶聚合物可以提高固化反应程度、提高固化物的韧性和强度 ,同时还使固化物的Tg 和热失重温度提高 ,SEM观察表明 ,加入液晶聚合物的材料断裂面面积增大 ,逐渐出现韧性断裂的特征。     

热致性液晶聚合物各类对环氧树脂性能的影响研究

利用自行合成的多种热致性高分子液晶聚合物对CYD－128环氧树脂进行共混改性,用FTIR方法研究了液晶聚合物对环氧树脂固化反应程度的影响,用DSC、TGA研究了液晶聚合物对环氧树脂固化物Tg和热失重温度的影响,测试了共混物的力学性能,并用扫描电镜观察了共混物冲击断面的形貌。结果表明：端基含有活性反应基团的液晶聚合物可以提高固化反应程度、提高固化物的韧性和强度,同时还使固化物的Tg和热失重温度提高,SEM观察表明,加入液晶聚合物的材料断裂面面积增大,逐渐出现韧性断裂的特征。     

溶液法液晶离聚物的制备及表征

以对苯二酚、复合二元酰氯、4-羟基萘偶氮对苯磺酸钠为反应基元,采用溶液缩聚法合成液晶离聚物(LCI)。用红外光谱仪、偏光显微镜、广角X射线衍射仪及热重分析仪对产物进行了分析,结果表明:在波数为1213,1017cm-1处出现了磺酸基团的特征峰,说明离子基团已成功引入到液晶聚合物中,合成了目标产物;LCI的熔点为197℃,相对分子质量为5607,具有热致液晶性,液晶织构为向列型,其清亮点高于分解温度,具有较宽的液晶态温度范围;LCI具有良好的热稳定性,初始分解温度可达296℃,热失重速率仅为0.71%/℃。     

热致液晶聚合物的热增强及应用

基于各种正式发表的文献 ,澄清了热致液晶聚合物发展过程中的一些问题 ,并对各种形式热致液晶聚合物的热增强属性作一系统阐述。     

环氧树脂增韧改性研究进展

综述了环氧树脂(EP)增韧改性的主要方法,分别阐述了通过热致性液晶聚合物、纳米粒子聚合物、超支化聚合物、核壳结构聚合物、互穿网络聚合物、柔性链聚合物等方式增韧EP的原理,并分析现阶段这些技术所面临的问题,最后对其将来的发展趋势进行了展望。     

碳纤维增强液晶高聚物复合材料的研究

研究了碳纤维(CF)增强热致性液晶聚合物(TLCP)制备高性能复合材料;探讨了不同纤维含量、不同纤维类型对复合材料力学性能、微观结构的影响;扫描电镜(SEM)结果证实了液晶聚合物在加工过程中自取向,形成了微纤结构,具有自增强作用,使复合材料表现出非常高的力学性能。     

热致性液晶聚氨酯的合成研究

合成了两种含聚酯液晶基元的液晶聚氨酯,研究了反应时间、不同原料对产物结构的影响,利用红外光谱（IR）、偏光显微镜（POM）、差示扫描量热分析仪（DSC）等手段确认其结构,正交偏光场观察证实,该液晶聚氨酯在一定温度范围内为热致性向列型液晶。     

Blends of liquid crystalline polyester–polyurethane and epoxy: Preparation and properties

A novel liquid crystalline polyester–polyurethane (LCPU) that contains polyester mesogenic units was synthesized in the present work. Through a careful investigation of the structure and morphology of the LCPU, it was found that the home‐synthesized LCPU is a highly birefringent thermotropic nematic liquid crystal. After being blended with bisphenol‐A epoxy, the liquid crystalline polymer can, simultaneously, improve the impact strength and the glass transition temperature as well as the tensile strength and the tensile modulus of the blends. It was proved to be an efficient toughening agent for epoxy without the expense of other properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 783–787, 2003     

Thermotropic liquid crystalline polyesters containing naphthalenic mesogenic groups

Summary Recently, the use of naphthalene in liquid crystalline compounds has become more commonplace primarily in the industrial research into LC polymers with wholly aromatic structures. A large number of compositions have appeared in the patent literature, and have been well summarized in several recent articles. Even though a large number of LC naphthalene-containing copolyesters have been prepared and reported, much of this work deals with wholly aromatic systems which include no flexible spacers. In order to investigate the effects that the naphthalene structure has on liquid crystalline behaviour, a series of low molecular weight model compounds and polymers with flexible spacers were synthesized and characterized.     

含液晶基元聚氨酯对普通聚氨酯性能的影响

合成了一类既含有刚性液晶基元又含有柔性链段的主链型含液晶基元聚氨酯(LCPU)，以端羟基四氢呋喃-环氧乙烷共聚醚为基体材料，多异氰酸酯N-100为固化剂，探讨这类含液晶基元聚氨酯对聚氨酯弹性体力学性能的影响。结果表明，5种含液晶基元聚氨酯随着柔性链段长度的变化和在聚氨酯弹性体中加入比例的变化。表现出对聚氨酯弹性体力学性能的影响有较大的差异。与未改性聚氨酯弹性体相比，改性后聚氨酯弹性体共混物垃伸强座量大提高71％倍．断裂伸长率最大提高8．7倍．     

Synthesis and characterization of optically active liquid crystalline polyacrylates containing mesogenic phenylbenzoate groups

A series of novel side chain liquid crystalline polyacrylates with pendant chiral groups were synthesized. It was found that monomers with electron releasing -OC₄H₉ terminal groups seem beneficial for the formation of liquid crystalline phases. Copolymerization of the monomers was carried out and the physical properties of the copolymers were investigated. All synthesized polymers revealed liquid crystalline phases and appeared highly thermally stable with decomposition temperatures (T_d) at 10% weight loss greater than 384 °C and about 50% weight loss occurred beyond 442 °C under nitrogen atmosphere. Two miscible chiral compounds were also synthesized and used as chiral dopants to induce cholesteric liquid crystalline phases of polymers. Liquid crystalline phases of the polymers were investigated using DSC and XRD, and confirmed with POM technique. The optical properties of the induced cholesteric liquid crystalline polymers were investigated using UV-vis spectrometer. The appearance and the color variation of the polymer films before and after UV irradiation were also investigated. Typical helical morphology of the cholesteric liquid crystalline film was analyzed by SEM technique.     

聚合物分子量对其阻垢分散性能的影响

以苯乙烯磺酸钠、丙烯酸、丙烯酸甲酯为单体合成了一系列不同分子量的聚合物,探讨了分子量对阻碳酸钙垢、磷酸钙垢,分散氧化铁、锌盐的影响.结果表明：随着分子量的增大,聚合物对碳酸钙和磷酸钙的抑制能力增加,但当聚合物的浓度较大时,分子量对性能的影响减小.     

Thermotropic liquid‐crystalline polymers: Synthesis,characterization, and properties of poly(azomethine esters)

A series of poly(azomethine ester) copolymers were synthesized by the solution polycondensation method with different diamines. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), hot‐stage polarized microscopy, wide‐angle X‐ray diffraction, and solution viscosity. All polymers showed good thermal stability. The thermotropic liquid‐crystalline properties were examined by DSC and by microscopic observations. Except for one, all of the polymers showed nematic liquid‐crystalline behavior. The effects of temperature on crystallinity and the substituent on solubility, thermal stability, melting temperature, and viscosity were also studied. The voluminosity and shape factor were also computed from the viscosity data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 153–160, 2003     

Preparation and properties of azobenzene-containing amphiphilic miktoarm star polymers

Summary A series of novel miktoarm star polymers composed of a poly(ethylene oxide) (PEO) and two side-chain liquid crystalline azobenzene-containing polymethacrylate (PEO-(PMMAZO)₂) were prepared using atom transfer radical polymerization (ATRP). Bifunctional macroinitiator PEO-Br₂ was synthesized by condensation reaction in two steps and characterized by ¹H NMR, ¹³C NMR and IR. Kinetic study showed that it was a first order reaction referred to the monomer MMAZO, namely, 6-(4-methoxy-4’-oxy-azobenzene)hexyl methacrylate. The liquid crystalline behaviors of the miktoarm star polymers were studied by differential scanning calorimetry (DSC) and polarized optical microscope (POM). They exhibited smectic and nematic mesophases when Mn was beyond 9.4×10³ g/mol. The phase transition temperatures of the smectic and nematic phases increased while the melting temperature of PEO decreased with increasing molecular weight of the LC block. Compared with diblock polymer PEO-PMMAZO, the melting temperature of PEO in miktoarm star polymer decreased more rapidly.     

Investigation on stilbene‐ and azobenzene‐based liquid crystalline organophosphorus polymers

Two series of combined liquid crystalline polyphosphates bearing dual photoreactive mesogenic units (stilbene and azobenzene/α‐methylstilbene and azobenzene) were synthesized by solution polycondensation method. The structures of the synthesized polymers were confirmed by various spectroscopic techniques. Thermogravimetric analysis reveals that they are stable between 230 and 320°C. Differential scanning calorimetry studies were done to study the liquid crystalline property, and glass‐transition, melting, and isotropization temperatures for all the polymers. Polarizing optical microscope shows the birefringent melt for all the polymers exhibiting liquid crystalline property. The photochemical response was studied by UV–visible and fluorescence spectroscopy for all the polymers. The photocrosslinking reaction of the stilbene containing polymers was ascertained by spectroscopic and photolysis studies. The rate of the switching time for the conversion of trans to cis form of azobenzene unit was investigated by UV spectroscopy. The terminal substituents in the side chain affects the texture of liquid crystalline phase for all the polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Influence of two liquid crystalline polysiloxanes with different average molecular weight as new β-nucleator on crystallization structure of isotactic polypropylene

Two liquid crystalline polymers (LC-N1 and LC-N2) with different average molecular weight were designed and synthesized as a new β-nucleator in isotactic polypropylene (iPP). The main aim of this work was to investigate the influence of LC-N1 and LC-N2 on the crystallization structure and β nucleating activity of the iPP with wide angle X-ray diffraction and polarized optical microscopy. The β nucleation activity not only depended on the nucleator content, mesogenic molecular structure, and thermal processing history, but also on average molecular weight of the liquid crystalline polymers. LC-N1 or LC-N2 has been found to be an effective β-nucleator for the iPP. The experimental results indicated the relative content of β-crystal first increased and then decreased with increasing the nucleator content or crystallization temperature. The addition of LC-N1 or LC-N2 could provide a large number of nuclei, enhance the crystallization rate, reduce the spherulite size, and lead to a more uniform morphology; moreover, the colorful β-crystal was also induced. In addition, LC-N2 with higher average molecular weight is more effective than LC-N1 in inducing β heterogeneous nucleation under same crystallization conditions.