聚酯液晶高分子的开发及应用

介绍了液晶高分子的结构以及分类,着重阐述了以芳香族聚酯为主链的液晶高分子的合成,工业化产品,以及其性能,应用领域和改性研究等。     

功能液晶聚酯

在1888年,奥地利植物学家莱尼茨尔（Reiniter)在将胆甾醇苯甲酸酯加热到145．5度时变成一种粘稠,浑浊的液体,进一步加热到178．5度时变为透明的液体,将其冷却,在相同温度范围内会出现相反的变化,这一现象被认为是除物质的三态以外的另一个稳定状态,命名为液晶。     

液晶聚酯的液晶行为与加工性能

液晶聚酯由于具有特异的液晶行为和高强高模性能而越来越受到人们的关注。本文对液晶聚酯的液晶态形成原因、液晶态类型与链结构的关系、液晶态热稳定性及其成型加工性能进行了讨论，指出了提高液晶态热稳定性的方法及液晶聚酯的发展趋势。     

PET/PHB液晶共聚酯的合成及液晶性能

将对羟基苯甲酸（ＰＨＢ）单元引入聚对苯二甲酸乙二酯（ＰＥＴ）中,合成液晶共聚酯,１步法工艺优于２步法。就１步法工艺研究缩聚温度、时间、催化剂用量及ＰＨＢ含量对ＰＥＴ／ＰＨＢ共聚酯对数比浓粘数的影响。用偏光显微镜研究结果表明,ＰＥＴ／ＰＨＢ共聚酯呈丝纹形结构,属向列型液晶。用差示扫描量热仪研究的结果也反映出向列型液晶的特征。     

液晶聚酯的研究概况

概述了聚酯类液晶高分子材料的发展,对其分子设计、合成方法、应用及发展前景进行了比较详细的分析。     

功能液晶聚酯

综述了新型功能液日聚酯材料的大分子链结构、液晶相变温度与应用前景。这类功能液晶聚酯或者其主链含有大量碳碳双键,或者其侧链上含有大量氟碳链节或偶氮链节。功能液日聚酯的玻璃化转变温度和液日相变温度通常比传统高强度、高模量液日聚酯要低,尤其具有高强度、高模量液晶聚酯所不具备的特殊性能,如交联化、凝胶和感光作用,使其可以作为全息储存膜和其他功能材料。     

液晶高分子新型材料：Ⅱ 液晶高分子的合成

1 液晶基元、连接基团和液晶单元合成的任务在于先用适当的聚合方法将小分子的液晶基元通过刚性连接基团连接成较大分子量的液晶单元,将这些液晶单元再通过刚性连接基团连接成刚性液晶大分子链或通过亚甲基连接基团连接成重复单元并进而聚合成为半刚性液晶性大分子链,最后由这些大分子链构成聚合物本体并赋予其液晶性。     

热致规则全芳液晶聚酯酰胺的合成和液晶相转变

本工作采用含酯键的全芳复合二酰氯在 NMP-LiC1 溶剂体系中,分别和 H_2N 进行低温溶液缩聚反应,合成了五种全芳规则聚酯酰胺:PEA-Ar-SO_2、PEA-Ar-M、PEA-Ar-P、PEA-Ar-OHP、PEA-Ar-MeOP。用 DSC 和偏光显微镜研究了这五种 PEA 的热致液晶行为,发现只有 PEA-Ar-MeOP 具有热致液晶特性,其 T_m=330℃,T_d=415℃。由于刚性单元空间构型的非线性,PEA-Ar-SO_2不具备热致液晶特性。而 PEA-Ar-M、PEA-Ar-P、PEA-Ar-OHP 三种聚合物的 T_m>T_d,同样不具备热致液晶的相转变特性。     

PBT-PHB热致性液晶共聚酯的合成研究

以对羟基苯甲酸甲酯和1,4-丁二醇为原料,在稳定剂、催化剂存在条件下,合成双-对羟基苯甲酸丁二酯（BBHB）;以对苯二甲酸二甲酯和1,4-丁二醇为原料,合成对苯二甲酸二丁二酯（DBT）;采用熔融缩聚法由BBHB和DBT合成含柔性间隔基的液晶共聚酯PBT—PHB。由正交实验确定最佳反应条件和实验配方。用带有偏光显微镜的熔点仪、傅立叶红外光谱仪分别测定熔点、液晶温度范围和结构,并利用粘度与粘均相对分子质量间的对应关系计算出该液晶共聚酯的粘均相对分子质量。     

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。     

Influence of different polyesters and their molecular weight on the textural and electrooptical behavior of polymer‐dispersed liquid crystals

The textural and electrooptical behavior of a nematic liquid crystal (LC) dispersed in a flexible and rigid polyester was studied. The dispersion of LC in the polymer matrix and light transmission through the polymer‐dispersed liquid crystal (PDLC) is governed by the nature of the polymer, its molecular weight, and the applied voltage. It was observed that the transmission of light and the dispersion of LC maximizes their respective values at the minimum molecular weight irrespective of the nature of the polymer and at the maximum voltage. The reason is the predominance of chain alignment over entanglement at the minimum molecular weight. As molecular weight increases, the transmission of light as well as the dispersion of LC in the polymer may increase or decrease depending on the predominance of chain entanglement or chain alignment. The alignment of LC droplets in the direction of the applied voltage is increased by an increase in the applied voltage, causing enhancement of the light transmission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 284–289, 2003     

新型液晶PVDF合金的研究

本文系统地研究了液晶聚合物(LCP)与PVDF合金共混体系的组成及加工工艺条件对共混物制件性能的影响。并用SEM观察了合金的形态结构。结果表明:在液晶含量10%左右时,加工温度为210℃,合金的拉伸强度最高,磨耗量最低,体系分散均匀并形成了较多的微纤结构。     

Crosslinkable polyesters containing styrylpyridine segments

Polyesters containing styrylpyridine segments were synthesized with the bisphenols 2,6-di[2-(2-hydroxy-1-naphthyl)vinyl]pyridine, 2-[2-(2-hydroxy-1-naphthyl)vinyl]-8-hydroxyquinoline, and 2-(4-hydroxystyryl)-8-hydroxyquinoline as starting materials. The polyesters were characterized by inherent viscosity measurements, Fourier transform infra-red, ¹H nuclear magnetic resonance, X-ray, differential thermal analysis, thermomechanical analysis, thermogravimetric analysis, and isothermal gravimetric analysis. The polymers were amorphous or microcrystalline and were soluble in hot, polar, aprotic solvents containing 5 wt % LiCl. They showed T_g at 112–175°C and T_m at 165–295°C. After heat curing, the polyesters yielded resins which were stable up to 367–335°C in N₂ and 347–329°C in air and afforded anaerobic char yields of 72–64% at 800°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1135–1141, 1997     

Aromatic polyesters based on bisphenol‐A for liquid insulating systems: A synthetic approach

This work concentrates on the area of the synthesis of polymers for liquid insulating systems. We have studied reactions of aromatic esters like diphenyl terephthalate/isophthalate, diphenyl carbonate with Bisphenol‐A, and tri functional glycerol for the synthesis of aromatic polyesters that can be used as liquid insulating systems. The process comprises a transesterification resin synthesis based on a single pot process, with a temperature profile up to 250°C and an inert atmosphere of nitrogen. The byproduct of the phenol is continuously removed under a steady flow of nitrogen to enable polycondensation. The resins obtained were tested for their physical properties, such as melting range, relative viscosity, and hydroxyl value. These resins were also used in solution film formation to establish their film forming properties. The method explored is the simplest one, and permits the use of commercial materials as the feedstock. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 606–614, 2005     

Synthesis of unsaturated polyesters of increased solubility in styrene

The present study presents the synthesis of unsaturated polyester resins using only one glycol i.e., ethylene glycol. Polyesters of inorganic solubility in styrene were prepared. Properties of the resins in the noncrosslinked state in the process of crosslinking and after curing were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3143–3150, 2006     

Synthesis of PP–LCP graft copolymers and their compatibilizing activity for PP/LCP blends

The aim of this work was the synthesis of new graft copolymers consisting of polypropylene (PP) backbones and liquid crystalline polymer (LCP) branches, to be used as compatibilizing agents for PP/LCP blends. The PP-g-LCP copolymers have been prepared by polycondensation of the monomers of a semiflexible liquid crystalline polyester (SBH 1 : 1 : 2), that is, sebacic acid (S), 4,4′-dihydroxybiphenyl (B), and 4-hydroxybenzoic acid (H) in the mole ratio of 1 : 1 : 2, carried out in the presence of appropriate amounts of a commercial acrylic-acid-functionalized polypropylene (PPAA). The polycondensation products, referred to as COPP50 and COPP70, having a calculated PPAA concentration of 50 and 70 wt %, respectively, have been fractionated with boiling toluene and xylene, and the soluble and insoluble fractions have been characterized by Fourier transform infrared and nuclear magnetic resonance spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry, and X-ray diffraction. All analytical characterizations have concordantly shown that the products are formed by intricate mixtures of unreacted PPAA and SBH together with PP-g-SBH copolymers of different composition. Exploratory experiments carried out by adding small amounts of COPP50 or COPP70 into binary mixtures of isotactic polypropylene (iPP) and SBH while blending have demonstrated that this practice leads to an appreciable improvement of the dispersion of the minor LCP phase, as well as to an increase of the crystallization rate of iPP. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 391–403, 1998     

Study on hyperbranched polyesters as rheological modifier for Spandex spinning solution

The rheological behavior of polyurethane (PU)/N,N‐dimethylformamide (DMF) spinning solutions with various contents of hyperbranched polyesters was studied using a RS150L‐controlled stress rotational rheometer. The results showed that the viscosity of the spinning solutions could be greatly reduced by adding hyperbranched polyesters even at 0.5 wt% loading. The zero‐shear viscosity of solutions with hyperbranched polyesters was much lower than that of pure PU/DMF solution, which indicated a lower degree of entanglement when solutions were in a static state. The apparent activation energy of viscous flow and the critical shear rate for shear thinning of solutions with hyperbranched polyesters were much lower than that for pure PU/DMF solution, which indicated a weaker entanglement structure formed. In addition, the effect of hyperbranched polyesters on the mechanical properties of Spandex fiber was discussed. Copyright © 2006 Society of Chemical Industry     

Polyurethanes and polyesters from lignin

Lignin, obtained through steam explosion from straw, was completely characterized via elemental analysis, gel permeation chromatography, ultraviolet and infrared spectroscopy, and ¹³C and ¹H nuclear magnetic resonance spectrometry. Polyurethanes were obtained by treating steam‐exploded lignin from straw with 4,4′‐methylenebis(phenylisocyanate), 4,4′‐methylenebis(phenylisocyanate) –ethandiol, and poly(1,4‐butandiol)tolylene‐2,4‐diisocyanate terminated. The obtained materials were characterized by using gel permeation chromatography, infrared spectroscopy, and scanning electron microscopy. Differential scanning calorimetry analysis showed a T_g at ?6°C, assigned to the glass transition of the poly(1,4‐butandiol) chains. The presence of ethylene glycol reduced the yields of the polyurethanes. The use of the prepolymer gave the best results in polyurethane formation. Steam‐exploded lignin was used as the starting material in the synthesis of polyesters. Lignin was treated with dodecanoyl dichloride. The products were characterized by using gel permeation chromatography, infrared spectroscopy, ¹³C and ¹H nuclear magnetic resonance spectrometry, and scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1451–1456, 2005     

Fire‐retardant hybrid thermosetting resins from unsaturated polyesters and polysilazanes

This introduces an organic–inorganic thermosetting hybrid resin system based on unsaturated polyester and polysilazanes. It shows the chemical modification of unsaturated polyester structures by end capping to enable the combination of both components. In general, halogen‐free unsaturated polyesters are not fire‐retardant and have to be equipped with additives. Fillers and intumescent additives are preponderantly used in today's fire‐retardant formulations. In contrast to these fire‐retardants, polysilazanes act as ceramizing agents. Polysilazanes are suitable fire‐retardants for resin transfer molding due to their low viscosity. Both burning behavior and glass transition temperature (T_g) are investigated as important application properties. In contrast to state‐of‐the‐art fire‐retardant formulations polysilazane‐based thermosetting hybrid resins burn with high intensity and fast extinction. Therefore, total heat and smoke emission is decreased. The formation of ceramic structures during burning results in high residual mechanical properties and a low mass loss. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40375.     

蒙脱土在酯类聚合物中的应用

叙述了蒙脱土(MMT)在酯类聚合物中的应用,主要介绍了MMT在聚丙烯酸酯、聚甲基丙烯酸甲酯、聚乙酸乙烯酯、聚氨酯、环氧树脂和聚碳酸酯中的应用.