一种新型热致性液晶聚酯酰亚胺的合成与表征

在Higashi直接缩聚法的基础上,利用分步投料法,以N,N-己二撑-1,6-双苯偏三酸酰亚胺二胺(IA6)、对羟基苯甲酸(PHB)和对苯二酚二对羟基苯甲酸酯(PHQ)为主要原料,合成了一种新型三元共聚液晶聚酯酰亚胺(IA6PP)。采用FTIR、DSC、TGA、POM和WAXD等方法研究了单体种类对所合成的聚合物结构和性能的影响。结果表明:IA6PP呈现出典型的向列型液晶的特征,液晶温度区间为252~365℃,热稳定性明显高于由4,4-二羟基二苯甲酮(DHBP)、IA6和PHB合成的液晶聚酯酰亚胺(IA6PD)。     

Syntheses and characterization of poly(ethylene terephthalate) modified with p-acetoxybenzoic acid

Though the structure and properties of a copolyester of 40 mole % of polyethylene terephthalate (PET) and 60 mole % p-hydroxybenzoic acid (PHB) (PET/60PHB) and their blends have been well documented, no work has been reported in an open literature on the systematic investigation of the PET copolymers modified with broad range of p-acetoxybenzoic acid (PABA) composition as yet. In this study, several PETA-x copolyesters having various PABA compositions from 10 to 70 mole % were prepared by the melt reaction of PABA and PET without a catalyst, where x denotes the mole % of PABA. And the modified polyesters obtained were characterized by ¹H-NMR spectrophotometry, X-ray diffraction pattern, polarizing microscopy, thermal analysis, and rheometry. The anisotropic phase appeared when x is above 50 mole % of PABA, and especially for the x's of 60 and 70 mole %, the nematic liquid crystalline texture appeared clearly on the whole matrix. As the mole % of PABA increased, melting temperature, heat of fusion, crystalline temperature, degree of crystallinity, and the glass transition temperature of the modified PET were decreased, but the thermal stabilities of those copolyesters were increased. The dependence of melt viscosity on the shear rate for PETA-50 ∼ 70 followed the typical rheological behavior of liquid crystalline polymers. Finally, it was concluded that the PETA-x copolyesters having compositions of higher than 50 mole % of PABA exhibit the behavior of thermotropic liquid crystalline polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1707–1719, 1999     

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     

Analysis of the tensile modulus of poly(p‐hydroxybenzoate)/poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) ternary polyester composite fibers

Liquid crystalline polymer reinforced plastics were prepared by compounding (PHB/PEN/PET) blends. A fibrillar PHB structure was formed in situ in the PEN/PET matrix under a high elongational flow field during melt‐spinning of the composite fibers. The formation of PHB microfibrils in the composite fiber with different PHB contents and winding speeds was observed. The PHB microfibril reinforced PEN/PET composite fibers exhibited an unexpectedly low tensile modulus. We have evaluated the tensile modulus of the fibers using the non‐modified 22 and a modified 23 Halpin–Tsai model. From the analysis of both models, large differences were found between the theoretical and experimental values of the tensile modulus, and the low value of the tensile modulus of the composite fiber could not adequately be explained by either model. Thus, we analyzed the observed modulus values using the Takayanagi model, 24 which describes the concept of mechanical discontinuities in semi‐crystalline polymers. Using the Takayanagi model, the effective fraction of continuous or discontinuous microfibrils was evaluated. Consequently, we could successfully explain the very low modulus of the PHB/PEN/PET composite fiber, having a large number of PHB microfibrils, using the Takayanagi model. Copyright © 2003 Society of Chemical Industry     

Structure and properties of novel PMDA/ODA/PABZ polyimide fibers

A series of random copolyamic acid were synthesized from various ratios of two diamines 4, 4′‐oxydianiline (ODA) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (PABZ) by polycondensation with pyromellitic dianhydride (PMDA) in N‐methyl‐2‐pyrrolidone (NMP). Their inherent viscosities were in the range of 1.89–2.91 dl/g. The polyamic acid (PAA) solution drops were spun into fibers by the wet spinning process. The polyimide (PI) fibers were obtained from PAA fibers after drawn and treated in heating tube. The fibers were characterized by fourier transform infrared (FTIR), wide X‐ray diffraction (WAXD), scanning electron microscope (SEM), thermal gravimetry analysis (TGA), dynamic mechanical analysis (DMA), and tensile testing. WAXD showed these PI fibers were basically amorphous. The tensile strength and initial modulus of the PI fiber reached 1.53 and 220.5 GPa when diamine ratio of PABZ/ODA was 7/3, which were almost three times and 30 times over that of the PMDA/ODA PI fibers. TGA showed that the PI fibers were thermally stable with 10% weight losses recorded in the range of 492–564°C under nitrogen atmosphere, and their glass transition temperature (T_g) were found to be 410–440°C by DMA with increasing PABZ content from 30 to 70%. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Effect of composition and molecular structure on the LC phase of PHB-PEN-PET ternary blend

Poly(p-hydroxybenzoic acid) (PHB)–poly(ethylene terephthalate) (PET) 8/2 thermotropic liquid crystalline copolyester, poly(ethylene 2,6-naphthalate) (PEN), and PET were mechanically blended to pursue the liquid crystalline (LC) phase of ternary blends. The torque values of blends with increasing PHB content abruptly decreased above 40 wt % of PHB content because the melt viscosity of ternary blends dropped. Glass transition temperature and melting temperature of blends increased with increasing PHB content. The tensile strength and initial modulus of blends were low at 10 and 20 wt % PHB. However, the blends containing above 30 wt % PHB were improved with increasing PHB content due to the formation of fibrous structure. The blend of 20 wt % PHB formed irregularly dispersed spherical domains, and the blends of 30–40 wt % PHB showed LCP ellipsoidal domains and fibrils. In the polarized optical photographs, the blends of 40 wt % PHB showed pseudo LC phases. The degree of transesterification and randomness of blends were increased with blending time. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1065–1073, 1998     

Synthesis and melt spinning of fully aromatic thermotropic liquid crystalline copolyesters containing m‐hydroxybenzoic acid units

Fibers of fully aromatic thermotropic copolyesters based on p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m‐acetoxybenzoic acid (m‐ABA) were prepared by a high‐temperature melt‐spinning technique. Two types of the copolyesters were prepared by a high‐temperature melt polycondensation reaction using 33 mol % of kink (m‐ABA) and 67 mol % linear monomer units (p‐ABA, TPA, HQDA), and characterized by differential scanning calorimetry (DSC), polarized optical microscopy, wide‐angle X‐ray diffraction (WAXD), and intrinsic viscosity measurements. The mechanical properties and the morphology of the fibers were also determined by tensile tester, WAXD, and scanning electron microscopy (SEM). The copolyesters exhibited phase‐separated nematic liquid crystalline morphology within a broad temperature range in an isotropic matrix. DSC analysis of the copolyesters revealed broad endotherms associated with the nematic phases. The melting and spinning temperatures were in a processable region. Fibers exhibit well‐developed fibrillar structure parallel to the fiber axis. The highly oriented morphology of the fibrils is slightly dependent on the type of the linear monomer. The strength and modulus values determined for the fibers that contain equal molar composition of the linear p‐ABA, HQDA/TPA units are comparable to other reported rigid systems containing fully aromatic species. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2580–2587, 2002     

PHB/PET/HQ-TPA液晶共聚酯纤维的制备及结构性能研究

对所合成的ＰＨＢ／ＰＥＴ／ＨＱ－ＴＰＡ三元液晶共聚酯进行纺丝实验，制备了初生纤维并对其进行了热处理。利用ＤＳＣ，ＷＡＸＤ，密度，Ｓ－Ｓ曲线等方法对初生纤维及热处理后纤维的结构与性能进行了研究。结果表明：该体系的液晶共聚酯具有较好的可纺性，初生纤维在ＤＳＣ升温过程中有冷结晶峰和熔融双峰现象产生，初生纤维经热处理后，可使其微晶尺寸有较大提高，力学性能得到一定程度改善，但未使其取向性能得到进一步改善。     

Effect of composition on molecular alignment in polyethylene terephthalate copolymers

In this study molecular alignment in copolymers of polyethylene terephthalate (PET) and p-hydroxybenzoic acid (PHB) was examined by means of differential radial distribution function (DRDF) analysis of wide angle X-ray scattering data. The study was carried out using two representative copolymers with the PHB content of 30 and 60 mol%. The DRDF curves for the amorphous and the partially crystalline samples of these copolymers showed periodic intermolecular peaks up to various radial distances. The appearance of these peaks at $\text{～5}\text{A}\text{?}$ periodicity suggested the existence of more-or-less parallel chain segments in the copolymers. The extent of the lateral molecular organization was $\text{～15}\text{and}\text{30}\text{A}\text{?}$ for the amorphous copolymers containing 30 and 60 mol% PHB, respectively. A substantial structural difference was therefore shown for the copolymers in this composition range. The DRDF curve for the amorphous copolymer with 30 mol% PHB was found to be very similar to that for the previously reported glassy PET with 0 mol% PHB, indicating that the two materials had almost the same intermolecular structure. The structural information revealed by these DRDF results was in agreement with the various property changes caused by varying PHB contents of the copolymers.     

Morphological and mechanical properties of PET-LCP blend fibers

Blends of poly(ethylene terephthalate-co-p-oxybenzoate) (PET–PHB) with poly(ethylene terephthalate) (PET) have been studied in the form of as-spun and drawn fibers. Mechanical properties of drawn blend fibers (DR-6.0) up to 10 wt % liquid crystalline polymer (LCP) component exhibit significant improvement in modulus and strength. With the addition of 10 wt % LCP content in PET matrix, the modulus increases from 11.78 to 17.72 GPa, and the strength increases from 0.76 to 1.0 GPa in comparison to the PET homopolymer. With further addition of LCP content, the properties drop down. Scanning electron microscopy studies of drawn blend fibers show that up to 10 wt % LCP content the blends contain the LCP domains in the size range of 0.07–0.2 μm and are well distributed in the PET matrix. © 1995 John Wiley & Sons, Inc.     

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。     

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     

Dielectric Properties of Thermotropic Polymer Liquid Crystals

Abstract

Dielectric relaxation spectrometry is a useful tool to study molecular dynamics of macromolecular systems. Theoretical principles as well as experimental techniques are analyzed from the point of view of their capabilities. Results are reported for PET/xPHB, where PET = poly(ethylene terephthalate), PHB = p-bydroxybenzoic acid (the liquid crystalline component) and x is the mole fraction of PHB in the copolymers.     

高分子量PET／60PHB热致性液晶共聚酯的结构与性能

研究了固相缩聚过程中PET/60PHB共聚酯结构性能的变化。随着反应的进行,分子量增大,分子量分布宽度指数变小;玻璃化温度略增,熔融温度增加幅度较大;热稳定性明显提高。预聚体中主要存在PET的低共熔物或部分同二质晶,固相缩聚反应使PET结晶消失,PHB结晶形成并完善。固相缩聚大大改善了共聚酯的可纺性,用[η]为0.95dL/g的共聚酯制得断裂强度达到高强范围(1GPa)的初生纤维。     

The effect of substitution levels on the luminescent and degradation properties of fluorescent poly(ester‐anhydride)s

In this work, two kinds of diacid monomers were synthesized by a convenient scheme, where 4‐hydroxy‐3‐methoxybenzoic acid (vanillic acid) or 4‐hydroxy‐3,5‐dimethoxybenzoic acid (syringic acid) directly condensated with succinic chloride. Corresponding polyanhydrides were obtained by melt polycondensation. Copolyanhydrides composed of the new monomers and sebacic acid (SA) were further prepared and characterized by NMR, DSC, and fluorometer. The two new kinds of polyanhydride emit strong fluorescence and have similar fluorescent spectra to poly(di(p‐carboxyphenyl) succinate anhydride) (P(dCPS)). The emission wavelength (λ_em) of the copolymers could be tuned by the excitation wavelength (λ_ex). Degradation rate of the copolyanhydrides decreased as dMOCPS or ddMOCPS fraction increased, and the degradation duration could be modulated from several days to more than 3 months. It addition, the copolyanhydrides displayed typical surface‐degradation characteristics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1214–1221, 2006     

PEALT三元共聚酯的制备及其性能研究

通过聚对苯二甲酸乙二醇酯(PET)、聚己二酸乙二醇酯(PEA)、聚L-乳酸(PLLA)3种低聚物熔融缩聚反应制备聚(对苯二甲酸乙二醇酯-己二酸乙二醇酯-乳酸)(PEALT)共聚酯。采用核磁共振仪(~1H-NMR)、差示扫描量热仪(DSC)、热重分析仪(TGA)和广角X射线衍射仪(WAXD)等测试技术对共聚酯进行了表征。     

Solidification behavior and recovery kinetics of liquid crystalline polymers

The supercooling behavior of three thermotropic liquid crystalline polymers (TLCP's), 60 mole% p-hydroxybenzoic acid and 40 mole% poly(ethyleneterephthalate), 60/40 PHB/PET, 80 mole% p-hydroxybenzoic acid and 20 mole% poly(ethyleneterephthalate), 80/20 PHB/PET and a copolyester of 73 mole% p-hydroxybenzoic acid and 27 mole% of 2-hydroxy-6-naphthoic acid, Vectra A900, was studied by means of both rheological and thermal methods. 60/40 PHB/PET and Vectra A900 exhibited a degree of supercooling as high as 80°C while there was only 20°C of supercooling for 80/20 PHB/PET. The degree of supercooling for the blends of 60/40 PHB/PET and 80/20 PHB/PET also decreased with the increase in 80/20 PHB/PET content. The increase in G′ as the temperature decreased was more gradual for 60/40 PHB/PET and Vectra A900 than that for 80/20 PHB/PET, which was beneficial from a processing point of view. The solidification of the LCP melt was attributed to both the crystallization and the freezing of the mesophase. The degree of crystallinity for all three TLCP's was very small, less than 5%, as measured by the DSC. It was found that both 60/40 PHB/PET and Vectra A900 showed an induction period of a few minutes during solidification while 80/20 PHB/PET solidified continuously at the test temperature. Therefore, 60/40 PHB/PET and Vectra A900 seem to be more suitable for use in processes such as blow molding and film blowing than 80/20 PHB/PET.     

Morphology and thermal properties of two polymethacrylates modified by a polymer liquid crystal

We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures T_g determined via thermal mechanical analysis. The T_g value of the blend E is shifted towards the T_g of PLC; T_g of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity α_L values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more than 60 K Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of diblock,triblock, and multiblock copolymers containing poly(3‐hydroxy butyrate) units

A poly[(R,S)‐3‐hydroxybutyrate] macroinitiator (PHB‐MI) was obtained through the condensation reaction of poly[(R,S)‐3‐hydroxybutyrate] (PHB) oligomers containing dihydroxyl end functionalities with 4,4′‐azobis(4‐cyanopentanoyl chloride). The PHB‐MI obtained in this way had hydroxyl groups at two end of the polymer chain and an internal azo group. The synthesis of ABA‐type PHB‐b‐PMMA block copolymers [where A is poly(methyl methacrylate) (PMMA) and B is PHB] via PHB‐MI was accomplished in two steps. First, multiblock active copolymers with azo groups (PMMA‐PHB‐MI) were prepared through the redox free‐radical polymerization of methyl methacrylate (MMA) with a PHB‐MI/Ce(IV) redox system in aqueous nitric acid at 40°C. Second, PMMA‐PHB‐MI was used in the thermal polymerization of MMA at 60°C to obtain PHB‐b‐PMMA. When styrene (S) was used instead of MMA in the second step, ABCBA‐type PMMA‐b‐PHB‐b‐PS multiblock copolymers [where C is polystyrene (PS)] were obtained. In addition, the direct thermal polymerization of the monomers (MMA or S) via PHB‐MI provided AB‐type diblocks copolymers with MMA and BCB‐type triblock copolymers with S. The macroinitiators and block copolymers were characterized with ultraviolet–visible spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, cryoscopic measurements, and thermogravimetric analysis. The increases in the intrinsic viscosity and fractional precipitation confirmed that a block copolymer had been obtained. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1789–1796, 2004     

Solution copolycondensation of isophthalic acid,terephthalic acid, 4,4′‐dihydroxydiphenylsulfone,and bisphenols with a tosyl chloride/dimethylformamide/pyridine condensing agent

The solution polycondensation of a mixture of various parts of isophthalic acid (IPA) and terephthalic acid (TPA) with 4,4′‐dihydroxydiphenylsulfone (BPS) with tosyl chloride/dimethylformamide/pyridine as a condensing agent was studied. To elucidate how the reaction should be done to obtain copolymers of high molecular weights, we examined the two‐stage copolycondensation with BPS and 2,2‐bis(4‐hydroxyphenyl)propanes (BPAs) by changing the content of IPA/TPA and the amount of BPS or BPA used in the initial reaction. Controlling the reaction at an earlier stage could facilitate the copolycondensation. The polyesters of IPA/TPA and BPS of moderate inherent viscosity values up to 1.0 were obtained by the two‐stage reaction with optimal amounts of BPS first and then additional BPS. Satisfactory results were also obtained by the dropwise addition of BPS over 10–20 min in the preparation of the IPA/TPA–BPS polymers containing less than 50 mol % TPA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2607–2610, 2002