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本文以对笨二甲酰氯(TC)、对苯二酚(HQ)及不同分子量的端羟基聚砜低聚物(PSF)为原料,通过熔融缩聚法制得了一系列含有聚砜间隔段的三组分嵌段共聚酯。对产物用偏光显微镜下的双折射、搅动乳光和X-光衍射等手段研究了其液晶行为。分别以分子量为1.05×10~3和2.05×10~3的PSF为原料,所得其聚酯出现液晶性所需介晶单元的最小用量各为30和50mol%,若以双酚A(BPA)或双酚S(BPS)残基单元代替PSF基元计算,则为8.3和9.9mol%。 相似文献
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4,4’-对苯二甲酰基二氧二苯甲酸与脂二醇的共聚及液晶性能研究 总被引:1,自引:0,他引:1
以对苯二甲酸和对羟基苯甲酸为起始原料合成了液晶单体4,4’-对苯二甲酰二氧二苯甲酰氯(TOBC),用TOBC分别与癸二醇-1,10,己二醇-1,6,戊二醇-1,5,丁二醇-1,4和乙二醇进行缩聚反应,生成了一系列主链型热致液晶共聚酯。用DSC、热台偏光显微镜和X-射线衍射仪等对合成的共聚酯的液晶行为进行了表征,结果表明,合成的共聚酯均为向列型热致液晶,其液晶温度范围在20℃-68℃之间,并随着脂肪族二醇中亚甲基(CH2)单元的增加,共聚酯的熔融转变温度(Tm)和各向同性温度(Ti)均有规律的变化。表明主链型液晶共聚酯分子中柔性间隔基的大小对共聚酯的液晶性质有着明显的影响。 相似文献
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以对羟基苯甲酸、对苯二甲酸和对苯二酚为共聚单体,经乙酰化和熔融缩聚两步法合成三元热致液晶共聚酯。引入长链脂肪族化合物1,8-辛二酸作为改性单体,按不同比例代替对苯二甲酸,制备了一系列含柔性链段的新型四元热致液晶共聚酯。通过傅里叶红外光谱(FT-IR)和核磁共振碳谱(13C-NMR)对共聚酯结构进行表征,采用差示扫描量热(DSC)和热失重分析(TGA)表征其热性能,采用偏光显微镜(POM)和X射线衍射(XRD)分析其液晶性能。研究表明,三元液晶共聚酯熔点达407℃,热稳定性优异。随着1,8-辛二酸含量增加,四元共聚酯熔点显著降至214℃,热稳定性较好,最大热分解温度达到428℃。该系列共聚酯显示了典型的向列型液晶织态结构。1,8-辛二酸的引入显著改善了液晶共聚酯的可加工性。 相似文献
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本文利用DSC研究了热致液晶性序列嵌段共聚酯在不同升温速率时的多重熔融转变,和不同冷却速率对结晶与熔融过程的影响。发现T_(kn)和T_(ni)与热历史、升温速率及成形条件均无关,T_(kn)=425.86K,T_(nt)=480.60K;而T_(in)与T_(nk)随冷却速率增大而降低。 相似文献
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以对苯二甲酸和对羟基苯甲酸为起始原料合成了液晶单体4,4’-对苯二甲酰地氧二苯甲酰氯(TOBC),用TOBC分别与癸二醇-1,10,己二醇-1,6,戊二醇-1,5,丁二醇-1,4和乙二醇进行缩聚反应,生成了一系列主链型热致液晶共聚酯。用DSC、热台偏光显微镜和X-射线衍射仪等对合成的共聚酯的液晶行为进行了表征。结果表明,合成的共聚互均为向列型热致液晶,共液晶温度范围在20℃ ̄68℃之间,并随着脂肪 相似文献
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A series of four block copolymers based on aromatic acetoxy-polysulphone (Ac-PSF), terephthalic acid (TPA), m-phthalic acid (MPA), acetoxy-benzoic acid (Ac-HBA), and a di(acetoxy)bisphenol monomer were synthesized. Their structures were determined by IR, thermal mechanical analyses and solubility tests. They all exhibit liquid crystalline behaviour. 相似文献
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本文以对乙酰氧基苯甲酸(pHB)、4,4′—二乙酰氧基二苯基丙烷(BPA)、对苯二甲酸(TPA)为单体,研究了制备液品共聚酯的熔融缩聚反应历程。通过用NaOH标准溶液滴定缩聚反应过程中析出的醋酸来间接地测定反应程度,讨论了无外加催化剂条件下合成液晶共聚酯的反应动力学。最后,对共聚合过程中的相态变化进行了观察。 相似文献
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F. Lynn Hamb 《Journal of polymer science. Part A, Polymer chemistry》1972,10(11):3217-3234
A new process for the preparation of copolyesters of glycols and bisphenols is described. Employing a preformed polyester, an acid, and a bisphenol diacetate, the procedure is useful for a variety of copolyesters. It is illustrated with the preparation of copolyterephthalates of ethylene glycol and 4,4′-isopropylidenediphenol. The reaction is proposed to proceed by an initial cleavage of the polyester, followed by polymerization of the acid- and acetate-terminated products. Intermediate heterogeneous structures then equilibrate. 相似文献
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A series of copolyesters were synthesized by melt‐polycondensation reaction of poly(ethylene terephtalate) (PET) with various proportions of equimolar compositions of p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephtalic acid (TPA). Viscosity, liquid crystallinity, thermal properties, degree of crystallinity and thermal stabilitiy of these copolyesters were investigated by Ubbelohde viscometer, hot‐stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD) and thermogravimetric analysis (TGA), respectively. On the basis of viscosity measurement, it was observed that intrinsic viscosity values of the copolyesters are increased regularly with increasing amounts of aromatic units (p‐ABA, HQDA and TPA) in the polymer chain. Thermotropic liquid crystalline behavior was observed in the copolyesters containing over 50 mol% of rigid p‐ABA/HQDA/TPA aromatic units. DSC analysis of the anisotropic copolyesters revealed broad and weak endotherms associated with the nematic phases, and the melting temperatures were found to be in the processable region. As the mol% of PET in the polymer chain increased, the specific enthalpies of fusion and the degree of crystallinity of the copolyesters were also increased regularly. 相似文献
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A mechanism for the preparation of copolyesters from a preformed polyester, diacid, and bisphenol diacetate in the melt phase is described. Utilizing copoly(ethylene:4,4′-isopropylidenediphenylene 50:50 2-methylisophthalate) as a model system, the reaction is shown to proceed through simultaneous cleavage of the preformed polyester by diacid, polymerization by condensation of carboxyl and bisphenol acetate groups, and equilibration through polyester cleavage by carboxyl polymer ends. In this model system, the rates of cleavage and polymerization are competitive, which results in a random sequence distribution early in the reaction. 相似文献
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Zekeriya Yerlikaya Serpil Aksoy Erdal Bayramli 《Journal of polymer science. Part A, Polymer chemistry》2001,39(19):3263-3277
A series of fully aromatic copolyesters based on p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m‐acetoxybenzoic acid (m‐ABA) were prepared by a modified melt‐polycondensation reaction. The copolyesters were characterized by DSC, thermogravimetric analysis, 1H NMR, polarized optical microscopy, X‐ray diffraction, and intrinsic viscosity measurements. The copolyesters exhibited nematic liquid‐crystalline phases in a broad temperature range of about 150 °C, when the content of linear (p‐ABA, HQDA, and TPA) units was over 67 mol %. DSC analysis of the anisotropic copolyesters revealed broad endotherms associated with the nematic phases, and the melting or flow temperatures were found to be in the processable region. The flow temperatures and crystal‐to‐nematic and nematic‐to‐isotropic transitions depend on the type of linear monomer units, and these transitions increased as the content of the p‐ABA units increased, as compared to the HQDA/TPA units. When the content of the p‐ABA units increased, as compared to other linear units (HQDA and TPA), the intrinsic viscosity and degree of crystallinity of the copolyesters also increased, implying a higher reactivity for p‐ABA in the p‐ABA/HQDA/TPA/m‐ABA polymer system. The aromatic region in the 1H NMR spectra of the copolyesters containing equal molar compositions of p‐ABA, HQDA, and TPA units were sensitive to the sequence distribution of aromatic rings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3263–3277, 2001 相似文献
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A series of copolyesters were prepared from chloro-hydroquinone or methyl-hydroquinone,terephthalic acid, and two kinds of comonomers, such as oxy-4,4'-diphenol and isophthalic acid.which could provide kinking and bending in chain. The four-components copolyesters in certain range of compositions have low melting point,ssteady mesophase in a broad temperature range and fiber-forming tendency. This report focuses on the relations of their molecular composition-transitions-liquid crystallinityand fiber-forming tendency and the morphologic characterizations of mesophase. 相似文献
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In this study a range of wholly aromatic copolyesters based on kink m‐acetoxybenzoic acid (m‐ABA) monomer (33 mol%) and equimolar‐linear p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephthalic acid (TPA) monomers (67 mol%) have been synthesized by melt polycondensation reaction process at 280°C and 260°C for different time intervals. Characterization of copolyesters were performed by solution viscosity measurement, wide–angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), hot‐stage polarized light microscopy, proton‐nuclear magnetic resonance analysis (1H‐NMR). According to the results obtained, copolyesters showed thermotropic liquid crystalline behavior in an appropriate temperature range. The copolyesters were prepared in high yields. It was observed that the intrinsic viscosities of the copolyesters are increased regularly with increasing polymerization time and temperature. All the copolyesters were soluble in a trifluoroacetic acid/dichloromethane (30:70 v/v) except the copolyesters which were synthesized at 280°C in 5 h. According to the WAXD results; the degree of crystallinity of copolyesters were found to be between 5–15%. DSC and hot stage polarized light microscopy results showed that all the copolyesters are melt processable and a significant molecular interaction exist in a very broad temperature range (160°C and 165°C) in the nematic mesophase. The Tg values are increased with an increasing polycondensation reaction time and temperature and they were observed between 93–126°C. Fibers prepared by a hand‐spinning technique from the polymer melt exhibit well‐developed fibrillar structure parallel to the fiber axis. 相似文献