Synthesis and properties of aromatic polyazomethines and of yarns based on them

Conclusions A series of aromatic poly- and copolyazomethines have been synthesized, based on bisaldehydes (terephthalaldehyde, chloroterephthalaldehdye, or isophthalaldehyde) and diamines (p-phenylenediamine, m-phenylenediamine, chloro-p-phenylenediamine, bromo-p-phenylenediamine, and so forth).The effect of the structure of the monomers and of the proportions of these on polymer solubility, viscosity characteristics, fusibility, and ability to form a liquid crystal phase in the melt have been investigated.It has been shown that the use of monomers of the m-structure or of monomers containing bridging insulators (-O-, for example) is not a sufficient condition for reducing the melting point of polymers which is necessary for satisfactory processing into article from the melt. Only the introduction of substituents into the diamine ring, -C1 for example, ensures the preparation of fusible polymers (t_m 150–300°C) which form anisotropic melts.Strong fibres have been obtained from high-molecular polyazomethines based on chloro-p-phenylenediamine and terephthalic aldehyde by the method of spinning from a melt.Translated from Khimicheskie Volokna, No. 4, pp. 30–32, July–August, 1986.     

Synthesis of thermo- and pH-responsive polysilsesquioxane with carboxylic acid group

The thermoresponsive polysilsesquioxanes containing N-(methoxyethyl)methylamide structures with carboxylic acid groups were newly prepared. In the syntheses of the polysilsesquioxanes, the silane coupling reagent, obtained from the reaction of (3-isocyanatopropyl)trimethoxysilane and (2-methoxyethyl)methylamine, was used for the co-condensation with (3-mercaptopropyl)trimethoxysilane to give the polysilsesquioxane with mercapto group (MMEPSQ). MMEPSQ was employed as the intermediary compound to introduce carboxylic acid group through thiol-ene reaction. The polysilsesquioxane, which was prepared from the reaction of MMEPSQ and methacrylic acid showed the expected amphiphilic and thermoresponsive properties in an aqueous solution with addition of sodium hydroxide. The lower critical solution temperature (LCST) owing to hydrophobic aggregation increased with pH value of the aqueous solution. Furthermoe, the use of MMEPSQ for the reactions with maleic anhydride and successive ring-opening reaction by the amines, which contained pyridine or 15-crown-5-ether ring, enabled the formations of multi-functionalized polysilsesquioxanes. In the case of the polysilsesquioxane containing carboxylic acid groups and pyridine rings, the pyridinium salt structure was favorable to keep an enough solubility in water and the reversible thermoresponsive behavior. The polysilsesquioxane containing the crown ether and carboxylic acid groups, the selective ion recognition property to alkali metal ion was observed.     

Electrical conductivity of coal and coal char

The electrical conductivity of coal, at either 1 kHz or d.c., was measured at 24 °C on samples recovered from pyrolysis experiments aimed at modelling conditions during in situ gasification of coal. From an initial value of 10⁻³ S/m (when the coal is saturated with formation water), the conductivity decreases to 10⁻⁸ S/m when the coal is heated to 110 °C in vacuum. This low value, presumably due to dehydration of the coal, prevails for samples heated as high as 500 °C in dry argon. Samples of char recovered after pyrolysis to 800 °C or more have a conductivity of 10² S/m. Capitalizing on the large contrast between the conductivities of coal and char produced during gasification, electrical probing may be a sensitive tool for monitoring ‘burn-front’ progress during in situ coal gasification.     

The catalytic effect of boric acid on polyacrylonitrile-based carbon fibers and the thermal conductivity of carbon/carbon composites produced from them

The catalytic effect of boric acid on the graphitization and surface structure of polyacrylonitrile-based carbon fibers was investigated by dipping fibers in boric acid before heating at 2500 °C. The thermal conductivity of carbon/carbon composites produced from the modified carbon performs by chemical vapor infiltration was also studied. The results show that the treatment by boric acid has a catalytic-graphitization effect on the fibers that increases the crystallinity and changes the surface state of carbon fibers during high temperature treatment. The modified carbon fibers induce the deposition of pyrocarbon with high crystallinity and an obvious transition interface between the carbon fiber and pyrocarbon during chemical vapor infiltration. By changing the microscopic structure of the carbon fibers, the interface bonding between fibers and pyrocarbon is improved and the microstructure of pyrocarbon is regulated. The thermal conductivity of the carbon/carbon composites is therefore improved, especially that in the direction perpendicular to fiber axis.     

The effect of different carbon fillers on the electrical conductivity of ethylene vinyl acetate copolymer-based composites and the applicability of different conductivity models

Conducting carbon black (CCB), short carbon fiber (SCF), and multi-walled carbon nanotube (MWCNT)-filled conductive composites were prepared from ethylene vinyl acetate copolymer (EVA). Percolation thresholds of electrical conductivity in volume fraction (and in phr) for different carbon fillers were for CCB ∼0.14 (30 phr), for SCF ∼0.07 (15 phr) and for MWCNT mixed with solution process ∼0.03 (5 phr). No percolation threshold was observed for EVA–MWCNT composites mixed with dry process. Electrical conductivities at the percolation threshold for EVA–CCB, EVA–SCF and EVA–MWCNT (solution mix) composites were 2.5 × 10⁻⁶, 5.0 × 10⁻⁵, 2.5 × 10⁻⁴ S/cm, respectively. The applicability of different theoretical models to predict the conductivity of these composites was verified. The Scarisbrick model exhibited better agreement between theoretically calculated and experimentally determined conductivities for EVA–CCB and EVA–SCF composites at higher concentrations of filler but not at lower concentrations of filler. None of the models was found suitable for EVA–MWCNT composites. Deviations between the theoretical and experimental conductivities were substantially high for McCullough and Bueche models. Possible limitations in framing of different models were discussed. We have proposed a modified model, which exhibited better agreement between theoretical and experimental conductivities over wide range of concentrations for all three fillers.     

有机羧酸改性氧化铝纳米颗粒在聚丙烯中的成核效果研究

利用正庚酸、硬脂酸、环己基甲酸和苯甲酸对氧化铝纳米粒子表面进行化学改性,研究了改性粒子表面的基团结构以及接枝量对其在聚丙烯(iPP)基体中成核效果的影响。结果表明：与直链烷基和环烷基羧酸相比,苯甲酸改性颗粒(BA-Al₂O₃)具有优异的成核效果,当BA-Al₂O₃的添加量为0.1%(质量)时,成核聚丙烯的结晶温度和弯曲模量相对于纯iPP分别提高了9.4℃和21.9%。改性纳米颗粒BA-Al₂O₃的苯甲酸接枝量对复合材料的结晶温度和力学性能也有重要影响,接枝量小于1.3 mmol/(g Al₂O₃)时,BA-Al₂O₃的成核效果随接枝量增加而显著增加;接枝量大于1.3 mmol/(g Al₂O₃)时,成核效果略微增加。所以,通过调控改性颗粒的表面结构,可以有效提升iPP复合材料的结晶和力学性能。     

Synthesis, characterization and hydrolysis of aromatic polyazomethines containing non-coplanar biphenyl structures

New polyazomethines containing electron-withdrawing trifluoromethyl group and non-coplanar biphenyl structures were prepared at room temperature under reduced pressure. It was found that these polyazomethines would undergo hydrolysis in DMSO solution at temperature higher than 50 °C. The hydrolysis, evidenced by ¹H NMR spectra and GPC chromatograms, was resulted from the reverse reaction of azomethine formation and was facilitated at higher temperature. The GPC results also suggested that post-polymerization would be possible if polyazomethine films were heated at elevated temperature (200 °C) under reduced pressure (0.27 torr). The HOMO (−5.69 to −5.96 eV) and LUMO (−3.04 to −3.18 eV) energy levels of the new polyazomethines are much lower than those of other polyazomethines. Combined with the excellent solubility and good thermal stability, non-coplanar biphenyl structure containing electron-withdrawing trifluoromethyl group could be a new candidate as electron acceptor for the structure design of new conjugated polymers.     

不同羧酸根含量对双官能团聚降冰片烯质子交换膜性能影响的分子动力学模拟

基于Material Studio（MS）软件平台,构建了含有磺酸根和羧酸根双功能化基团的新型聚降冰片烯类质子交换膜模型。通过改变3种结构单元NBSC、DCNM以及DCNM-N的不同配比,探究了不同羧酸根含量对质子交换膜性能的影响,同时分析了质子交换膜的微观结构以及H₂O和H₃O⁺等小分子的输运特性。计算结果显示,H₂O和H₃O⁺的均方位移和扩散系数随着羧酸根含量的增加而逐渐减小。在298 K条件下,3种质子交换膜的质子传导率分别为22.75、46.14、56.77 mS·cm^-1。表明随着羧酸根个数的增加,质子传导率不断增大,但增幅先增大后减小。     

Introduction of carboxylic acid group to polypropylene fabric for battery separator

Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto a polypropylene (PP) nonwoven fabric for a battery separator. The AAc-grafted PP nonwoven fabric was characterized by IR, SEM, and TGA. The wetting speed, electrolyte retention, electrical resistance, and tensile strength were evaluated after grafting of AAc. It was found that the wetting speed, electrolyte retention, thickness, and ion-exchange capacity increased, whereas the electrical resistance decreased with increasing grafting yield. The elongation of AAc-grafted PP nonwoven fabric decreased with increasing grafting yield in dry state, whereas the elongation increased in wetting state.     

Noncovalent functionalization of boron nitride and its effect on the thermal conductivity of polycarbonate composites

Polycarbonate (PC) is an engineering thermoplastic with excellent insulation and mechanical properties. However, the low thermal conductivity restricted its application in electronic devices. Hexagonal boron nitride (h ‐BN) microparticle, a promising material with high thermal conductivity, was functionalized with cationic polyacrylamide (CPAM) and introduced into PC matrix to improve the thermal conductivity. SEM and XRD analysis showed that the modified BN (CBN) particles oriented and formed thermal conductive pathways within PC matrix. The formation of large‐area oriented CBN significantly improved the thermal conductivity and thermal stability of composites. At 20 wt % CBN loading, the thermal conductivity of 0.7341 Wm^?1 K^?1 and the temperature for 5% weight loss (T ₅) of 498.6 °C were obtained, which was 3.1 times and 77 °C higher than that of pure PC, respectively. Furthermore, outstanding electrical insulation property of matrix was retained in the composites. These results revealed that PC/CBN composite was a promising material for thermal management and electrical enclosure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44978.     

Thermogravimetric and resistivity study of Ex situ and In situ poly(methyl methacrylate)/carboxylic acid group functionalized multiwall carbon nanotubes composites

Polymer composites based on poly(methyl methacrylate) (PMMA)/carboxylic acid group functionalized multiwall carbon nanotubes (MWCNT) were prepared by the ex situ and in situ techniques with 0.05% loading by weight. Composite films were fabricated by solvent casting method. Electrical conductivity of the composites as well as of the neat PMMA polymer was measured in the temperature range 333 K to 423 K. Neat PMMA samples prepared by the same method showed complete insulating behavior. Ex situ technique leads to a lower value of percolation threshold. Infrared spectroscopy was used to analyze the effect of functionalization of MWCNT on the interfacial bonding of PMMA and MWCNT. Thermogravimetric analysis revealed that the maximum degradation temperature has been shifted to higher region for in situ composites compared to PMMA itself—and the ex situ composites indicated better thermal stability. X‐ray diffraction study of composites also indicates that in situ composites functionalization incorporated MWCNT particles in the polymer chain. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The implications of carboxylic acid properties

Some properties of carboxylic acids are reviewed, with emphasis on recent experimental data, Qualified, consistent latent heat of vaporization data were developed for the series and a two-population viewpoint is suggested. The equation of state formulated by Grenzheuser [1] is also recommended as a practical tool, and its further development is urged.     

The effect of cellulose nanowhiskers on the flexural properties of self-reinforced polylactic acid composites

Self-reinforced polylactic acid (SR PLA) composites incorporating cellulose nanowhiskers (CNWs) were produced by coating orientated PLA fibres with a polyvinyl acetate (PVAc)–CNW mixture as a binder prior to hot compaction at 95 °C. PLA fibres were produced with an average diameter of 11 (±0.9) μm via a melt-drawing process at 180 °C. Scanning electron microscopy (SEM) images revealed that the CNWs imparted roughness to the PLA fibre surface. Cross-sectional examination of the SR PLA composites after hot-pressing confirmed that the PLA fibres had maintained their morphology. Incorporation of 8 wt% CNWs within the SR-PLA composites revealed an increase in their flexural strength (48%) and modulus (39%) compared to the control composite (flexural strength ∼82 MPa and modulus ∼3.9 GPa). In addition, whilst the control SR-PLA composite revealed quite brittle characteristics, the addition of CNWs and PVAc gave the self-reinforced composite a more ductile behaviour.     

Synthesis and properties of composites of oligoazomethine with char

Conjugated aromatic oligo(azomethine) derivatives (oligo‐AMs) were prepared by the condensation of terephtaldehyde 4,4′‐diformylbiphenyl bis(4‐formylphenyl) ether and p‐phenylene diacrolein with 1,4‐diaminobenzene at room temperature. The structures of the synthesized oligomers were characterized by FTIR, ¹H‐NMR, TGA–DTG, UV–vis absorption spectra, and elemental analyses. Additionally, in this study, the oligomer composites were obtained using the carbon material (char) derived from the 450°C pyrolysis of waste polyethylene terephthalates. The conductivity measurements of the produced composites were determined at 24‐h periods by doping with iodine vapor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

芳基撑双吡唑酮羧酸酯的合成及表征

以芳香族二元酸为原料通过3步反应合成了两个芳基撑双吡唑酮羧酸酯,用红外、核磁及质谱对其结构进行了表征。     

The effect of aromatic diboronic acid on characteristics of polybenzoxazine based on phenol and 4-aminomethylbenzoate

In this study, a polybenzoxazine, (PPab) based on phenol and 4-aminomethyl benzoate and its composites containing various amounts of 1,4-benzene diboronic acid, (BDBA) were synthesized by stepwise curing. It has been determined that both thermal stability and char yield were increased as the amount of BDBA incorporated was increased. The improvements in thermal characteristics were associated with condensation reactions of B-OH of BDBA and not only with hydroxyl groups of polybenzoxazine but also ester groups on the aniline linkages yielding a highly cross-linked structure. In addition, self-condensation reactions of B-OH groups generated boroxine net-work. Strong evidences for growth of this net-work on benzoate units of the polymer were detected.     

Interaction between carboxylic acids and the peptide group

The interaction between the peptide group and carboxylic acids is one of either protonation or hydrogen bonding. Both interactions will affect the vibrational frequency of the peptide group, resulting in changes in the characteristic amide vibrations. Infra-red spectroscopy has been used to examine the change in the amide I and II absorption bands of the model compound N-methylacetamide (NMA) when it is dissolved in deuterochloroform and various deuterochloroform/carboxylic acids, such as acetic, formic, dichloroacetic and trifluoroacetic acid. The results indicate that the interaction is one of hydrogen bonding except when NMA is dissolved in the strongest acid used, trifluoroacetic acid (TFA). Studies on the interaction between TFA and the peptide group of poly(l-alanine) various poly(dl-alanines) and poly(γ-benzyl-l-glutamate) show that the hydrogen bond interaction occurs, with little evidence of protonation taking place. In poly(γ-benzyl-l-glutamate) it was found that the TFA interacted both with the peptide group and the side chain carboxyl group.     

羧酸共聚物表面活性剂的合成及其对水泥浆流动性影响

以聚乙二醇单甲醚和马来酸酐为原料合成了大分子马来酸酐聚乙二醇单甲醚单酯,适宜的合成条件为n(聚乙二醇单甲醚):n(马来酸酐)=1:1.2,100℃下反应3 h,并用不同聚合度的马来酸酐聚乙二醇单甲醚单酯大分子单体与丙烯酸、甲基丙烯酸羟乙酯、乙烯基磺酸钠等单体进行自由基共聚合,得到了不同侧链长度的羧酸共聚物.同时,对羧酸共聚物作为水泥减水剂的减水性能进行了考察,研究结果表明,聚乙二醇单甲醚相对分子质量为1 000,引发剂z(KlX5)=2.5%时,水泥浆料的流动性最高,说明羧酸共聚物减水剂的分散效果为最好.     

The effect of different lithium salts on conductivity of comb-like polymer electrolyte with chelating functional group

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF₃SO₃, LiBr and LiClO₄ were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and ¹³C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion-cation association consistent with increasing LiCF₃SO₃ concentrations. Moreover, the ¹³C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. T_g and T_d of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.     

离子液体改性石墨烯的制备及其对ABS复合材料导热性能的影响

合成了一种氨基功能化离子液体[HAIM]BF4,并将其应用于石墨烯的改性。通过绿色直接的球磨法,将G粉与1-己基-3-氨乙基咪唑四氟硼酸离子液体[HAIM]BF4相结合,制备出离子液体功能改性石墨烯（G@ILs）。所得G@ILs使用熔融共混法加入丙烯腈-丁二烯-苯乙烯共聚物（ABS）中,制备G@ILs/ABS复合材料。使用X射线衍射分析（XRD）,X射线光电子能谱（XPS）,扫描电子显微镜（SEM）,透射电子显微镜（TEM）和拉曼测试等多种手段对G@ILs的结构和性质进行分析。结果表明,[HAIM]BF4通过阳离子-π相互作用对石墨烯进行了有效修饰,保持了石墨烯的结构完整性。由于G@ILs的独特性能,G@ILs/ABS复合材料在机械性能方面表现出相当大的改善。加入1 wt.%G@ILs的G@ILs/ABS复合材料的拉伸强度和弯曲模量为42.4 MPa和2145.1 MPa,比ABS提高了8.36%和12.76%。此外,在加入1 wt.%G@ILs的G@ILs/ABS复合材料的导热系数为0.249 W·m-1·k-1,比纯ABS提高了21.5%。