热致液晶性聚酯酰胺的研究进展

热致液晶性聚酯酰胺由于其独特的化学结构，形成了一新的液晶聚合物体系，本文就类热致性晶聚合物体系的研究进展作进行了述评。     

热致型液晶共聚与聚烯烃的原位复合

用热致型液晶共聚酯作为成纤材料、聚烯烃为基体进行复合，在复合中引入界面改性剂。对共混体的熔体流动性、基体聚合物的结晶性能进行了研究，对两相界面结合原位复合材料的力学性能进行了分析测试。     

含热致液晶性共聚酯的聚砜共混物

将一种含萘环的热致液晶性共聚酯与聚砜材脂熔融共混并挤塑成条．毛细管流变性测试表明，这一共聚酯降低了共混物的表观粘度，甚至低于其本身的粘度．共混物受剪切作用形成了各向异性的微纤增强结构，并具有皮芯结构．在液晶聚合物含量低到２％与０．５％的样条中仍有共聚酯微纤形成．共聚酯微纤提高了聚砜的力学性能，含２０％共聚酯共混物挤塑条的位伸模量为聚砜树脂的二倍半．     

以热致液晶聚合物微纤增强的原位复合材料

用４种热致液晶聚合物分别与聚丙烯,聚对苯二甲酸丁二酯,聚碳酸酯,聚醚砜和聚砜搭配,在各聚合物对的“加工窗口“温度范围内熔融共混并挤塑得到６种共混物。藉流变仪,扫描电子显微镜,偏光显微镜,动态力学谱仪等重点研究了原位复合材料中微纤结构的形成,组分特性,熔体粘度,挤塑温度和浓度等因素对各向异性结构形成的贡献,以及液晶聚合物对聚合物结晶的诱导作用和两相间的相互作用。     

热致液晶含氯侧基聚芳醚酮的单晶状条带织构

通常主链液晶高分子在受到剪切作用时 ,分子微纤呈周期性锯齿状排列 ,其光学效应表现为在偏光显微镜下可观察到相互平行且与剪切方向垂直的条带织构 [1] .而厚度适中的主链液晶聚合物薄膜经过热处理 ,即使没有受到剪切取向的作用 ,介晶微区的尺寸发展到一定大小时也会形成条带织构 ,即所谓结晶诱导[2 ] 和固化诱导 [3,4 ] 的条带织构 .在所报道的条带织构中 (包括剪切和非剪切 ) ,分子链均平行于膜平面 .本文研究发现 ,热致液晶氯代聚芳醚酮的薄膜样品在其高有序液晶温区经热处理 ,可形成结晶诱导的单晶状条带织构 ,其分子链垂直于膜平面 .…     

热致性液晶嵌段共聚酯的合成及表征

以对羟基苯甲酸甲酯和乙二醇为原料，通过熔融酯交换反应合成中间体（Ⅰ）：双（对一羟基苯甲酸）乙二醇酯．用溶液缩合法合成了三种不同嵌段长度的液晶嵌段共聚酯（Ｐ２４７、Ｐ２７７、Ｐ２７４）作为液晶聚合物与热塑性聚合物的“增容剂”．ＦＴＩＲ，Ｈ ＮＭＲ分析表明，嵌段共聚酯的结构和组成与分子设计基本相符；偏光显微镜证实，嵌段共聚酯在一定温度范围内为热致性向列型液晶，在较低温度为均相，在较高温度为两相结构．     

热致液晶共聚酯的熔融行为及结晶结构研究

采用ＤＳＣ及ＷＡＸＤ手段对含对羟基苯甲酸热致液晶共聚酯的相变行为及结晶结构进行了初步研究。结果表明，聚合物中存在两种同属于正交晶系的不同堆积形态结晶结构，在相变上表现为双重熔融峰。     

热致液晶共聚酯与聚酯热塑弹性体复合物的制备与性能

原位缩聚法制备了一系列(对羟基苯甲酸-对苯二甲酸-间苯二酚)(HB-TA-RES)热致液晶共聚酯与聚对苯二甲酸丁二酯-聚四亚甲基醚热塑弹性体(PBT-PTMG)复合物,并用POM,TGA,WAXD,SEM及动态应力流变仪等手段进行了表征.复合物在较宽的共聚酯含量范围(30 wt%~70 wt%)或共聚酯组成不同时(共聚酯中HB含量20 mol%~80 mol%)均具有热致液晶行为.当复合物中共聚酯含量≤50 wt%以及共聚酯中对羟基苯甲酸(HB)含量≤60 mol%时,共聚酯分子的结构更加均匀化,结晶组分的结晶行为受到限制,基体与液晶组分具有较好的复合效果,不表现明显的相分离行为.复合物与相应的纯共聚酯相比,具有较好的热稳定性;其粘度均比基体PBT-PTMG小.当复合物中共聚酯含量≥30 wt%时,其粘度下降尤为显著,表明其具有较好的加工性.     

一类可纺丝的全芳香热致性液晶共聚酯的合成和表征

利用Higashi芳香聚酯直接缩聚法的原理 ,采用一步混合投料直接缩聚的方法 ,以对羟基苯甲酸(PHB)、间苯二甲酸 (MPA)、4 ,4′ 二羟基二苯酮 (DHBP)和对苯二酚 (HQ)为单体原料 ,合成了全芳香共聚酯 .该合成方法反应条件温和 ,简单易控 ,产物分子量高 .用差热分析 (DSC)、热重分析 (TA)、偏光显微镜 (PLM)、广角X 射线衍射 (WAXD)等测试分析手段对共聚酯的热性能和液晶特性进行了表征 .研究结果表明 ,利用此方法合成所得的聚合物呈明显的向列型热致液晶特性 ,热稳定性高 ,并具有极易成纤的特点 ,有望成为一种可用于纺丝的全芳香热致液晶共聚酯材料     

偶氮苯为探针的液晶聚合物聚集形态研究

利用紫外-可见光谱,对比研究了尾挂侧链液晶聚合物和腰挂侧链液晶聚合物在结晶相和液晶相转变过程中的液晶基元取向情况.研究表明,石英基材表面倾向于诱导偶氮液晶基元垂直于基材排列;观察到了在液晶态尾挂侧链液晶聚合物和腰挂侧链液晶聚合物的不同取向行为.在室温下重新结晶数天后,腰挂液晶聚合物的紫外可见光谱缓慢回复.     

Isothermal crystallization kinetics of poly(ethylene terephthalate) in blends with a liquid crystalline polyester (Vectra A)

The isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) in blends with a fully aromatic liquid crystalline copolyester (Vectra A) were studied with differential scanning calorimetry. PET crystallization rates decreases with increasing Vectra fractions in the blends, and the percentage of PET that is crystalline also decreases with increasing Vectra. The equilibrium PET melting temperature for blends containing 40% or more Vectra is unambiguously below that of pure PET. Attenuated total reflectance Fourier-transform infrared spectroscopy measurements indicate that PET/Vectra transesterification does not take place. The results are consistent with a scenario based on prior NMR data in which there is some interphase mixing between the liquid crystalline and flexible polymers and an increase in the fraction of gauche conformers in the PET.     

An optical study of phase transitions of poly (ethylene terephthalate-co-p-hydroxybenzoic acid) liquid crystal

The copolyester containing 40 mol % ethylene terephthalate (PET) and 60 mol % p-hydroxybenzoate (HB) units has been reported by several investigators to be biphasic in the solid and the liquid states. The reported thermal transitions in the two phases, however, are in part contradictory, perhaps partly due to different polymerization conditions. The present work is a study of the transitions in each of the two phases of this copolyester by polarized light microscopy and by light transmission measurements. By light transmission measurements, the two phases were found to have two different glass transition temperatures for the onset of segmental motion, consistent with two assignable temperatures (T.). Cold crystallization and melting in each of the two different phases was also detected. The results help clarify the nature of transitions and agree with the results of dynamic mechanical analysis on the same thermotropic liquid crystalline copolyester.     

The crystallization characteristics of polypropylene and low ethylene content polypropylene copolymer with copolyesters

The crystallization characteristics of polypropylene (PP) and low ethylene content PP copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC). PP and PP copolymers was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 5 to 15 wt.%. All samples were prepared by solution blending in hot xylene solvent at 50 °C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PP and PP copolymers in a manner similar to that of a nucleating agent. The acceleration of crystallization rate was most pronounced in these blend systems with a maximum level at 5 wt.% of B28. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends.     

一种支氏液晶共聚酯的合成

在聚对苯二甲酸乙二醇酯与对羟基苯甲酸 (HBA)形成的共聚酯 (PET HBA)分子链中 ,引入具有分形结构的单体———三羟基苯 (TOP) ,以降低其熔点 ,改善加工性能 .考察乙酰化时间、缩聚时间、压力、TOP和HBA加入量对新型分形共聚酯的对数比浓粘度的影响规律 ,以及TOP和HBA加入量对新型分形共聚酯的熔点和液晶清亮点的影响 .TOP的加入能使PET HBA共聚酯的熔点下降 10℃以上 ,而液晶清亮点没有变化 ,拓宽了液晶区域     

THE NON—ISOTHERMAL CRYSTALLIZATION KINETICS OF A LIQUID CRYSTALLINE RANDOM COPOLYESTER WITH DIFFERENT COMPOSITIONS

The non-isothermal crystallization kinetics analysis of liquid crystalline random copolyestercomposed of p-oxybenzoate (B) and 2, 6-oxynaphthoate (N) monomers was carried out by meansof differential scanning calorimetry basing on Ziabicki and Jeziorny method. Although the compo-sition of 58/42 B-N copolyester had poorer thermodynamic crystallizability comparing with thoseof 30/70 and 75/25, its kinetic crystallizability Go was slightly larger. This fact was due to thepoorer match of sequences of 58/42 B-N in domains of nematic melt,and therefore better mobilityof chains during crystallization. The Avrami exponents of three composition species were allabout 2. 5, implying two dimensional growth in so-called non-periodic layer crystallites and a mixture of homogeneous and heterogeneous nucleation.     

Synthesis and characterization of a series of thermotropic liquid crystalline copolyester nanocomposites

A series of aromatic thermotropic liquid crystalline copolyester (TLCP) nanocomposites were prepared by the in situ intercalation polymerization of p‐acetoxybenzoic acid (ABA), terephthalic acid (TPA), and diacetoxynaphthalene (DAN) isomers in the presence of the organoclay. The DAN isomers used in this study were 2,3‐ and 2,7‐naphthylene. We examined the variation of the liquid crystallinity, morphology, and thermal properties of the nanocomposites with organoclay content in the range 0–10 wt %. All the polymer nanocomposites were fabricated with a molar ratio of ABA:TPA:DAN = 2:1:1; they were shown to consist of a nematic liquid crystalline phase for low organoclay contents (≤5 wt %), whereas the hybrids with a higher concentration of organoclay (≥10 wt %) were found not to be mesomorphic. By using transmission electron microscopy, the clay layers in the 2,3‐DAN copolyester hybrids were found to be better dispersed in the matrix polymer than those in the 2,7‐DAN copolyester hybrids. The introduction of an organoclay into the matrix polymer was found to improve the thermal properties of the 2,3‐DAN copolyester hybrids. However, the thermal properties of the 2,7‐DAN copolyester hybrids were found to be worse than those of the pure matrix polymer for all organoclay compositions tested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 387–397, 2006     

PET/HBA/TA/HQ四元共聚酯形态及相结构的研究

研制了一套蚀刻方法并对聚对苯二甲酸乙二醇酯/对羟基苯甲酸/对苯二甲酸/对苯二酚(PET/HBA/TA/HQ)体系的共聚酯液晶试样断面进行蚀刻,并用扫描电镜观察,发现此类共聚酯中存在两相结构.当PET摩尔分数小于50％时,分散相呈球状且富含PET,连续相富含全芳族链段;当PET摩尔分数等于或大于50％时,分散相和连续相结构发生颠倒,连续相富含PET,分散相球状粒子富含全芳族链段且为纤维状结构.因此可以断言,用熔融缩聚方法制备的PET/HBA/TA/HQ四元共聚酯不是无规共聚物,而是嵌段共聚物.     

芳香族共聚酯液晶熔体流变学

较全面综述了热致液晶性芳香族共聚酯(TLCP)熔体流变学的最新研究成就，指出TLCP溶体具有许多特征流变行为，存在屈服应力、低粘虞、负第一法向应力差、孔口收缩、长松弛时间及它们显著的剪切速率(振动频率)、温度、时间和热历史的依赖性。     

Study on poly(oxybenzoate-p-trimethylene terephthalate) copolymer

This study examined copolymers synthesized from poly(trimethylene terephthalate) (PTT) and p-acetoxybenzoic acid using solution proton nuclear magnetic resonance (NMR) spectroscopy. Proton NMR spectra showed that these p-oxybenzoate (POB)/PTT copolyesters were almost random copolymers because the preference factor of POB bonded to another POB unit in these copolyesters is close to 1.0 with a POB content between 20 and 80 mol%.The melting and crystallization behaviors of these copolyesters were studied by differential scanning calorimetry (DSC). In the heating DSC scan of the POB rich composition, the endothermic peak is weaker because the enthalpy of fusion decreased due to a melting transition from a crystalline to anisotropy liquid state. Thermogravimetric analysis results indicated that the decomposition temperature (T_d) increased with POB content. The crystalline morphology of the copolyester was further investigated with a polarized optical microscope, indicating that the POB/PTT copolyesters with 60 mol% POB are highly anisotropic in the liquid state.