含X-型和棒型两种液晶基元的主链型共聚酯

采用高温溶液缩聚方法,合成了一系列不同配比的含X-型和棒型两种液晶基元的主链型芳族共聚酯。经检测,所有样品均具有热致液晶性。本文对这类共聚酯的液晶行为进行了研究。     

BLENDS OF THERMOTROPIC LIQUID CRYSTALLINE POLYESTER AND POLY(ETHYLENE TEREPHTHALATE)

Two kinds of blends of thermotropic liquid crystalline polymers (LCPs) and poly(ethylene terephthalate) (PET) were prepared by solution and melt blending, respectively. Crystallization behavior of the blends was observed by differential scanning calorimetry (DSC). The LCP in both blends considerably decreased the cold crystallization temperature of PET and increased the crystallization rate in the low-temperature region, but did not show any significant effect on crystallization in the high-temperature region. Phase behavior of samples prepared by melt blending was investigated with the scanning electronic microscope (SEM). It was found that LCP/PET blends display a biphasic structure with an aromatic unit-rich phase as a dispersed domain, and a highly oriented fibrous structure was formed on the fracture surface of the blends. During the melt blending process, PET reacted with LCP through transesterification, as indicated by both DSC and SEM measurements.     

Molecular orientation in sheared molten thermotropic random copolyester

The macromolecular alignment and texture orientation in sheared thermotropic copolyester were investigated using in situ wide-angle X-ray scattering (WAXS) and polarizing optical microscopy (POM). The molecular behavior was correlated with viscoelastic properties. The polymer is a random copolyester based on 60 mol% 1,4-hydroxybenzoic acid (B) and 40 mol% ethylene terephthalate (ET) units. X-ray scattering showed that the molecular chains were aligned along the flow direction. The degree of molecular orientation, , is an increasing function of the applied shear rate. However, rheo-optics showed that shear flow could not orient the polydomain texture, i.e., neither defect stretching nor elimination of defects was observed. Instead, shear compressed the microdomains and gave rise to long-range orientation correlations. Rheology showed that the nematic melt is viscoelastic, the loss modulus G″ dominates the elastic modulus G′, and the dynamic viscosity η* is shear thinning. Moreover, the steady shear viscosity, η, also behaved shear thinning, while the first normal stress difference N ₁ remained positive. The empirical Cox–Merz rule did not hold, , within the shear rate range studied. The microscopic and rheological properties suggest that B–ET is a flow-aligning nematic polymer.     

Orientation dynamics in commercial thermotropic liquid crystalline polymers in transient shear flows

In situ X-ray scattering measurements of molecular orientation under shear are reported for two commercial thermotropic liquid crystalline polymers (TLCPs), Vectra A950® and Vectra B950®. Transient shear flow protocols (reversals, step changes, and flow cessation) are used to investigate the underlying director dynamics. Synchrotron X-ray scattering in conjunction with a high-speed area detector provides sufficient time resolution to limit the total time spent in the melt during testing, whereas a redesigned X-ray capable shear cell provides a more robust platform for working with TLCP melts at high temperatures. The transient orientation response upon flow inception or flow reversal does not provide definitive signatures of either tumbling or shear alignment. However, the observation of clear transient responses to step increases or step decreases in shear rate contrasts with expectations and experience with shear-aligning nematics and suggests that these polymers are of the tumbling class. Finally, these two polymers show opposite trends in orientation following flow cessation, which appears to correlate with the evolution of dynamic modulus during relaxation. Specifically, Vectra B shows an increase in orientation upon flow cessation, an observation that can only be rationalized by the assumption of tumbling dynamics in shear. Together with prior observations of commercial LCP melts in channel flows, these results suggest that this class of materials, as a rule, exhibits director tumbling.     

含聚碳酸酯、4-羟基苯甲酸、己二醇和1,4-苯二甲酸结构的嵌段共聚物的合成与表征

以端酰氯基团的热致液晶共聚酯ＨＴＨ ６和端酚羟基的聚碳酸酯（ＰＣ）齐聚物为原料，通过溶液缩聚法制备了含ＰＣ和ＨＴＨ ６的嵌段共聚物，并用ＩＲ、ＰＯＭ、ＤＳＣ、ＷＡＸＤ等手段对共聚物结构、热行为和结晶行为进了表征．ＤＳＣ和ＰＯＭ结果证明这些嵌段共聚物都属向列型热致性液晶．在２８０℃以下的温度范围内无相分离，而在较高温度（＞２８０℃）为两相结构．共聚物的结晶结构与ＨＴＨ ６相同，结晶度随ＨＴＨ ６含量增加而增加，结晶速度也受到ＰＣ含量的影响．     

Lipid and Protein Thermotropic Transition of Porcine Stratum Corneum by Microscopic Calorimetry and Infrared Spectroscopy

Microscopic differential scanning calorimetry and Fourier transform infrared spectrometry (DSC-FTIR) were combined to investigate the thermal response and IR spectra of lipid and protein in the process of a phase transition in porcine stratum corneum (SC) by KBr disc method. The alterations of bands associated with the CH₂ stretching vibrations near 2850 and 2920 cnv^?1 were used to determine the phase transformation of lipid with temperature. The peaks of amide I and II of protein were used to investigate the thermal conversion of protein. A reheating process was performed. The results indicate that the bands of lipid near 2900 cm^?1 shifted to greater wavenumber with increased temperature, but reversibly. The band due to deformation mode of the lipid altered from shoulder to smooth with increased temperature. During heating, α-keratin of the protein transformed gradually to p-keratin, but irreversibly. Thermal transitions that occurred near 78 °C and 115 °C for the sample on first heating were associated with phase transition of the lipid-protein complex and the protein in porcine SC, respectively. After reheating, this phase transitional temperature of the lipid-protein complex in porcine SC decreased from 78 to 68 °C, and the transition of protein near 115 °C almost disappeared. This behaviour indicates that porcine SC after heating might alter its structure. The thermally altered proportion of lipid was 43.98% and the thermally induced proportion of protein was 41.48% during the first heating process, but the restoration of lipid during the cycle of heating, cooling and reheating was 37.64%. The variation is attributed to the denaturation of protein to alter the structure of lipid-protein complex after first heating. This technique was simple, precise and reproducible for simple determination of stratum corneum or biological samples in a brief period.     

一种全芳香热致液晶聚芳醚酮

聚芳醚酮由于熔融粘度大和加工温度高而影响了其进一步工业化，因此降低熔融粘度和加工温度是研究聚芳醚酮的新课题[1]．目前在工程塑料中热致液晶高分子是一种具有低熔融粘度而性能优异的材料，其熔融粘度比一般高分子材料低得多，并且具有优异的机械性能[2]本文采用无现...     

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．     

新型侧链液晶聚甲基丙烯酸酯研究

以横向取代的液晶基元为侧基合成了聚甲基丙烯酸酯,并对此聚合物进行初步表征.在玻璃化温度(170℃)以上样品进入液晶态.样品较高的玻璃化温度以及能形成液晶态的特性被认为是棒状液晶基元使聚合物分子链刚性化的结果.     

含二羟基二苯酮系列热致液晶共聚酯的合成与表征──Ⅱ．含4，4＇－二羟基二苯酮，对苯二甲酸，对羟基苯甲酸，间苯二酚的共聚酯

采用直接熔融缩聚及固相聚合方法由４，４’－二羟基二苯酮（ＢＨＰ），对苯二甲酸（ＴＰ），对羟基苯甲酸（ＰＨＢＡ），间苯二酚（ＲＥＳ）成功地合成了四元共聚酯高分子，该聚酯的组成结构及性质由偏光显微镜、广角Ｘ－射线衍射、ＤＳＣ等手段进行表征，结果表明共聚酯具有向列型液晶特征．