Synthesis and characterization of thermotropic liquid crystalline poly(azomethine ether)s

Two series of monomers, namely 4,4′-diformyl-α,ω-diphenoxydecane and 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane, were prepared from 1,10-dibromodecane with p-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde (vanillin), respectively. The poly(azomethine ether)s were prepared by solution polycondensation using 4,4′-diformyl-α,ω-diphenoxydecane, 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane with various diamines. The monomers and polymers were characterized by intrinsic viscosity, FT-IR, ¹H, and ¹³C NMR spectroscopy. The thermogravimetric analysis reveals that the polymers are stable up to 320-500 °C and decomposed with good char yield. The thermotropic liquid crystalline properties of the polymers were examined by differential scanning calorimetry (DSC) and their textures observed under hot stage optical polarized microscopy (HOPM). All the polymers were exhibited thermotropic liquid crystalline properties except tetramethylene diamines-based polymers.     

Synthesis and characterization of thermotropic liquid crystalline poly(ester‐imide‐ketone)

A series of poly(ester imide ketone)s derived from N,N′‐hexane‐1,6‐diylbis(trimellitimide), 4,4′‐dihydroxybenzophenone, and p‐hydroxybenzoic acid (PHB) were synthesized by the direct polycondensation method in benzene sulfonyl chloride, dimethylformamide, and pyridine with varied PHB contents. The liquid crystalline behavior and thermal properties of the poly(ester imide ketone)s were characterized by polarized‐light microscopy, wide‐angle X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and temperature‐modulated differential scanning calorimetry (MDSC). The results showed that the synthesized polymers possessed a nematic thermotropic liquid crystalline characteristic and high thermal stability. The liquid crystalline polymers, with a PHB content ranging from 0 to 50 mol %, exhibited multiple phase transitions as evidenced by the MDSC results. A transitional smectic phase from solid state to nematic thermotropic liquid crystalline state was observed, and a transition model is proposed. Under certain conditions, the polymer with 33 mol % PHB content showed two significantly different liquid crystalline textures. This type of liquid crystalline polymer exhibited excellent fiber forming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1045–1052, 2003     

The infulence of aromatic diols on thermotropic Poly(ester-amide)s synthesized by direct polycondensation

Thermotropic Poly(ester-amide)s containing triethyleneglycol bis(4-carboxyphenyl) ether (PEG₃), o-Tolidine (OT) and various aromatic diols such as hydroquinone (HQ) and 4,4-biphenol (BP) were synthesized by direct polycondensation with DPCP (diphenyl chlorophosphate) as direct condensation agent in the presence of pyridine and LiCl. The polymer structures were characterized by infrared spectroscopy and elemental analysis. The influence of structure, substituents and contents of various aromatic diols on the phase transitions were studied by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy. These revealed that the structure and substituents of diols affected the mesophase while most of the synthesized polymers exhibit nematic mesophase. Addition of HQ decreased the melting temperature of the polymers, but, in contrast to others diols, did not affect thermal resistance.     

Effect of carbon nanofibers on the anisotropy of an aromatic thermotropic liquid crystalline polymer

The microstructure of a thermotropic liquid crystalline polymer (TLCP, Vectran V400 P) was investigated in the presence of vapor-grown carbon nanofibers. Percolation threshold was observed at ∼5 wt% carbon nanofibers. During processing, strong flows resulted in severe anisotropy of the semirigid rod-like TLCP molecules. For a given type of flow, however, the nanofibers were found to reduce the overall anisotropy of the TLCP nematic phase in the nanocomposite. We believe that nanofibers provide surface anchoring for the nematic phase that helps disrupt the high degree of molecular order in the TLCP matrix and reduces its anisotropy in the nanocomposite.     

Synthesis and characterization of cholesteric thermotropic liquid crystalline polyesters

Cholesteric liquid crystalline polyesters were successfully synthesized from isosorbide, methyl hydroquinone, and isophthaloyl chloride. Homo/copolyesters were synthesized by the solution polycondensation method, for which a mild organic base such as pyridine was employed. Inherent viscosities of polyesters P‐3–P‐5 were in the range of 0.31–0.39 dL/g at 25°C in chloroform, and polyesters P‐1 and P‐2 were insoluble in chloroform. Homo/copolyesters based on isosorbide, methyl hydroquinone, and isophthalic acid had thermal stability at more than 300°C on the basis of 10% weight loss. The thermotropic liquid crystalline properties were examined by differential scanning calorimetry and polarizing optical microscopy. Wide‐angle X‐ray diffraction study demonstrated that polyesters P‐1, P‐2, and P‐3 were semicrystalline, whereas the degree of crystallinity of polyesters P‐4 and P‐5 was less than 5%. Copolyester P‐4 showed formation of a yellow iridescent streak at 209°C on heating and development of a Grandjean texture at 270°C on heating. These are typical textures of the cholesteric liquid crystalline phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1232–1237, 2007     

Synthesis and characterization of thermotropic liquid crystalline poly(aryl ether ketone) copolymers with pendant 3‐(trifluoromethyl) phenyl groups

Novel poly(aryl ether ketone) copolymers with pendant 3‐(trifluoromethyl)phenyl groups were synthesized by the reaction of a crystal‐disrupting monomer, 3‐(trifluoromethyl)phenylhydroquinone (FH) and a mesogenic monomer, 4,4′‐biphenol (BP) with 1,4‐bis(p‐fluorobenzoyl)benzene (BF). Thermotropic liquid crystalline behavior of the copolymers was investigated by means of differential scanning calorimetry, polarized optical microscope and wide‐angle X‐ray diffraction. As a result, the copolymers with the respective molar ratios of FH/BP/BF of 0/100/100–10/90/100 and 80/20/100–100/0/100 were semi‐crystalline without liquid crystalline properties, and amorphous polymers, respectively. In contrast, copolymers with the molar ratio of FH/BP/BF of 20/80/100–70/30/100 had liquid crystalline characteristics. Interestingly, the formation of a highly ordered smectic phase was confirmed for copolymers with the molar ratio of FH/BP/BF of 20/80/100–50/50/100, respectively. All the liquid crystalline copolymers had a wide liquid crystalline temperature range (57–75 °C). Copyright © 2006 Society of Chemical Industry     

Conjugated polymers for nonlinear optics. 1. Synthesis and properties of poly(aryleneethynylenevinylene)s

Rigid-rod conjugated poly(aryleneethynylenevinylene)s were prepared from diethynyl aromatic compounds containing alkoxy groups and trans,trans-1,4-bis(β-bromoviny ])benzene by palladium-catalyzed coupling reaction. Polymerizations were carried out in THF in the presence of Pd catalyst, CuI and diethyl amine and gave a series of poly(aryleneethynylenevinylene)s with weight average molecular weight up to 56,000. The characterization of polymers by IR, NMR, UV-Vis, thermogravimetry, DSC, optical microscopy and X-ray are reported. The polymers exhibited intense fluorescence in solution (THF) and absorption band shifted to longer wavelength in films of the polymers. Polymers with long alkoxy side chains showed good solubility in THF, CH₂Cl₂ and CHCl₃.     

超支化聚(酰胺-酯)的合成及其光致变色性能研究

采用丁二酸酐、三羟甲基氨基甲烷为主要原料,在冰水浴条件下合成AB_3型单体,然后进行熔融缩聚制得超支化聚(酰胺-酯)(HBP);再将含羧基的螺吡喃光致变色基元通过反应活性基团羧基与AB_3超支化聚合物末端羟基的反应而引入到AB_3超支化聚合物末端上,得到具有光致变色性能的超支化聚合物(MHBP)。利用红外、核磁等对其结构进行了表征,利用紫外可见分光谱对超支化聚合物光致变色性进行了研究。结果表明:MHBP同时具有超支化聚合物的性能和光致变色性能。     

聚苯硫醚/热致性液晶聚芳酯的流变性及其纤维的性能研究

将自制热致性液晶聚芳酯(PEE)与聚苯硫醚(PPS)共混,通过熔融纺丝制备了PPS/PEE纤维。采用高压毛细管流变仪研究了PPS/PEE共混物的流变行为,利用扫描电子显微镜观察了PPS/PEE纤维的形态结构,通过差示扫描量热仪、热重分析仪、X射线衍射仪等表征了PEE的含量对PPS/PEE纤维热性能及结晶行为的影响。结果表明:PEE的加入大幅度降低了PPS树脂的表观黏度,减小了其对剪切速率的敏感性,提高了PPS基体的结晶速率,加快了其结晶过程,在一定程度上提高了PPS纤维的热稳定性;PEE在共混纤维中起到异相成核剂的作用,对PPS的晶型没有影响;PEE与PPS相容性较差,PEE以大尺寸微纤的形式分布于基体中。     

Influence of the monomer feeding sequence on the structure and properties of thermotropic liquid‐crystalline poly(ester imide)s

A series of poly(ester imide)s mainly derived from N,N′‐hexane‐1,6‐diylbistrimellitimides, 4,4′‐dihydroxybenzophenone, and p‐hydroxybenzoic acid were synthesized by a direct polycondensation method in benzenesulfonyl chloride, N,N′‐dimethylformamide, and pyridine with different monomer feeding sequences. The molecular structures and properties of the resultant poly(ester imide)s were characterized with NMR, IR spectrometry, polarized light microscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The results showed that the monomer feeding sequences had a great effect on the sequential structure of the molecular chains of the copolymers and consequently on their liquid‐crystalline (LC) properties, fiber‐forming capability, and other properties. Thus, it is probable that one could obtain an LC poly(ester imide) with given properties by controlling the monomer feeding sequence during the polycondensation process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and thermotropic liquid‐crystalline behavior of novel main‐chain poly(aryl ether ketones)

Novel aromatic poly(ether ketones) containing bulky lateral groups were synthesized via nucleophilic substitution reactions of 4,4′‐biphenol and (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (CF‐PH) with 1,4‐bis(p‐fluorobenzoyl)benzene. The copolymers were characterized by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and polarized light microscopy observation. Thermotropic liquid‐crystalline behavior was observed in the copolymers containing 40, 50, 60, and 70 mol % CF‐PH. The crystalline–liquid‐crystalline transition [melting temperature (T_m)] and the liquid‐crystalline–isotropic phase transition appeared in the DSC thermograms, whereas the biphenol‐based homopolymer had only a melting transition. The novel poly(aryl ether ketones) had glass‐transition temperatures that ranged from 143 to 151°C and lower T_m's that ranged from 279 to 291°C, due to the copolymerization. The polymers showed high thermal stability, and some exhibited a large range in mesophase stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1347–1350, 2003     

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     

Synthesis of sulfonated poly(phthalazinone ether sulfone)s by direct polymerization

Sulfonated poly(phthalazinone ether sulfone)s with high molecular weight were directly prepared by polycondensation of 4-(4-hydroxyphenyl) phthalazinone with various ratios of disodium 5.5′-sulfonylbis(2-fluoro-benzenesulfonate) to 4-fluorophenyl sulfone. The resulting ionomers with high IEC showed low swelling. The low swelling originates from intermolecular hydrogen bonds, which is confirmed by variable temperature IR spectroscopy. The membranes show very good perspectives in PEMFC applications.     

Preparation and properties of poly(amideether-imide)s derived from 1,4-bis(4-aminophenoxy)benzene,trimellitic anhydride,and various aromatic diamines

An imide ring containing dicarboxylic acid, 1,4-bis(4-trimellitimidophenoxy)benzene (III), was prepared by the condensation of 1,4-bis(4-aminophenoxy)benzene and trimellitic anhydride. A series of new poly(amide-ether-imide)s were prepared by the direct polycondensation of diimide-diacid III with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents inN-methyl-2-pyrrolidone (NMP) in the presence of calcium chloride. The highest inherent viscosity value of a poly(amide-ether-imide) obtained was 1.78 dL/g (inN,N-dimethylacetamide, DMAc, at 30 °C). Flexible films with excellent tensile properties were cast from DMAc solutions. Glass transition temperatures of these poly(amide-ether-imide)s were recorded in the range of 248–297 C. These polymers do not show obvious weight loss before 400°C; the decomposition temperatures at which 10% weight loss in nitrogen and in air were observed for these poly(amide-ether-imide)s in the range of 521–564°C and 501–539°C, respectively. The polymers derived fromp-phenylenediamine or the diamines containing 1,4-bisphenoxy units exhibited a higher degree of crystallinity and higher initial decomposition temperatures but poor solubility in organic solvents.     

Studies on the synthesis and properties of poly(amide-azomethine)

Homopolymer and copolymer of poly(amide-azomethine) were synthesized from the corresponding diamines and dialdehydes. The polymerization was proceeded in the mixed solvent of o-chlorophenol and m-cresol (1: I by volume) at 0 °C for I S h. The inherent viscosities of the new aromatic poly(amide-azomethine)s are in the range of 0.51 to 2.31 dl/g. These polymers were soluble in sulfuric and formic acid. The TGA results show that no weight loss up to 400 °C under nitrogen atmosphere, which suggests the relatively good thermal stabilities.     

Rheological properties in blends of poly(aryl ether ether ketone) and liquid crystalline poly(aryl ether ketone)

Rheological properties of the blends of poly(aryl ether ether ketone) (PEEK) with liquid crystalline poly(aryl ether ketone) containing substituted 3‐trifluoromethylbenzene side group (F‐PAEK), prepared by solution precipitation, have been investigated by rheometer. Dynamic rheological behaviors of the blends under the oscillatory shear mode are strongly dependent on blend composition. For PEEK‐rich blends, the systems show flow curves similar to those of the pure PEEK, i.e., dynamic storage modulus G′ is larger than dynamic loss modulus G″, showing the feature of elastic fluid. For F‐PAEK‐rich systems, the rheological behavior of the blends has a resemblance to pure F‐PAEK, i.e., G″ is greater than G′, showing the characteristic of viscous fluid. When the PEEK content is in the range of 50–70%, the blends exhibit an unusual rheological behavior, which is the result of phase inversion between the two components. Moreover, as a whole, the complex viscosity values of the blends are between those of two pure polymers and decrease with increasing F‐PAEK content. However, at 50% weight fraction of PEEK, the viscosity‐composition curves exhibit a local maximum, which may be mainly attributed to the phase separation of two components at such a composition. The changes of G′ and G″ with composition show a trend similar to that of complex viscosity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4040–4044, 2006     

Study on the miscibility and rheological properties of thermotropic liquid crystalline polymers in thermoplastic matrices

The interfacial properties of polymer blends of the engineering thermoplastics (TPs) polycarbonate (PC) and polyethersulfone (PES) with thermotropic liquid crystalline polymers (TLCPs) were studied using FTIR and DSC. The TLCP/TP blend systems were mainly immiscible. The viscosity properties of the TLCP/TP blends were analysed. The mechanism of the viscosity variation of the blends is discussed. Based on the assumptions given in this paper, a reasoned theoretical formula of the blend viscosity is derived to express the viscosity reduction of the TLCP/TP blends.     

Miscibility in blends of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) and polyarylate

The miscibility of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) (HIQ35) and polyarylate (PAr) coprecipitated from a mixed solvent of phenol/tetrachloroethane was investigated with differential scanning calorimetry. It was found that the amorphous phase of HIQ35 and PAr formed a partially miscible blend at low concentration of HIQ35. No measurable interaction between HIQ35 and PAr occurred when the weight fraction of HIQ35 was close to or less than that of polyarylate, as evidenced by wide-angle X-ray diffraction results. Upon annealing at 315°C for several minutes, the apparent miscibility of HIQ35 with polyarylate appeared as a result of an initial reaction between the polymers. For longer annealing time, the thermal degradation of HIQ35 joined in the reaction. This reaction or degradation in the blend was confirmed by nuclear magnetic resonance analysis and the intrinsic viscosity measurement of the blend. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1581–1589, 1998     

Effects of p‐hydroxybenzoic acid monomer units on physical properties of thermal liquid crystalline poly(ester imide ketone)s

A series of poly(ester imide ketone)s (PEIKs) with varied p‐hydroxybenzoic acid (HBA) molar fraction derived from N,N′‐hexane‐1,6‐diylbis(trimellitimide), 4,4′‐dihydroxybenzophenone, and p‐hydroxybenzoic acid were synthesized by a “step‐feeding” polycondensation method in benzene sulfonyl chloride, dimethylformamide, and pyridine. High field ¹H, ¹³C, and 2D NMR spectroscopy measurements were combined to determine the assignments of hydrogen and carbon atoms in the copolymers. ¹³C inverse gated decoupling NMR spectra were taken and used as a quantitative method to analyze the chain sequence structures of these copolymers. The liquid crystalline behaviors and thermal properties of the PEIKs were characterized by polarized light microscopy (PLM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The NMR studies show that the monomeric unit ratios of the PEIKs are very close to the ratios of the monomers added into the polycondensation process. The analytical results of sequence distribution indicate that the sequence ratios of I‐H, H‐D, and H‐H dias rise with the increase of HBA molar fraction, while that of I‐D decrease. It is worth noting that the sequence ratios of H‐H are always very small among the four sequence ratios although the HBA molar fraction varied from 0 to 50%. It was shown that the copolymers possess a typical nematic thermotropic liquid crystalline character and high thermal stability, which is strongly related with the changes in sequence structure of the molecular chains. This type of liquid crystalline polymers also exhibits excellent fiber‐forming character in the melting state, which would find its potential usages in high performance fiber and fiber modification materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3183–3193, 2007     

Miscibility study of polymer blends composed of semirigid thermotropic liquid crystalline polycarbonate,poly(vinyl alcohol), and chitosan

Miscibility of binary and ternary polymer blends composed of thermotropic liquid crystalline polycarbonate (LCPC), poly(vinyl alcohol) (PVA), and chitosan was investigated by viscosity method, FTIR spectrum, and scanning electron microscope techniques. Effect of addition of chitosan as a compatibilizer on miscibility and morphology of binary LCPC/chitosan and PVA/chitosan and ternary LCPC/PVA/chitosan polymer blends was discussed. These measurements indicated that addition of chitosan into the blends of LCPC with PVA leads to an increase of miscibility and a formation of clear fibril structures on fractured surfaces, which are due to intermolecular hydrogen‐bonding interaction between LCPC, PVA, and chitosan chains. It was suggested that side‐chain hydroxy group of PVA and amino and hydroxy groups of chitosan play an important role in the formation of miscible phase and improvement of morphology in binary and ternary blends composed of LCPC, PVA, and chitosan. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1616–1622, 2004