Preparation of micron-sized aromatic polyamide particles using ultrasonic irradiation

Aromatic polyamide particles were prepared by reacting p-phthalyl chloride and 4,4′-diaminodiphenyl ether in an acetone solution with a high water content, using a precipitation polymerization method with ultrasonic irradiation. The average particle diameter was ca. 712 nm, and the particles were porous and spherical with a narrow size distribution. They showed a high degree of crystallinity and excellent thermal stability. The morphology and the thermal decomposition temperature of the submicron particles were found to depend strongly on the volume of water added to the reaction system. In this polymerization method, the addition of water was essential for the formation of spherical particles. The simultaneous mixing process resulted in the formation of particles with a narrow size distribution, and the use of ultrasonic irradiation was effective in reducing particle size.     

Syntheses of aromatic polyketones and aromatic polyamide

High molecular weight aromatic polyketones were prepared from p- and m-phenoxybenzoic acid in polyphosphoric acid by heating the reaction mixture at 100°C. High molecular weight aromatic polyamide was derived from the polyketone obtained through Schmidt reaction or Beckmann rearrangement. The polyamide obtained by Schmidt reaction was found to have some regularity in an arrangement of its repeating units. The thermal stability of the polyketone and the polyamide were good.     

Synthesis and features of thermolysis of fluorine-containing aromatic 1-hydroxy-1-hydroperoxides and 1,1′-dihydroperoxides

Aromatic fluorine-containing 1-hydroxy-1-hydroperoxides and 1,1′-dihydroxyperoxides were obtained and their thermolysis features were studied. The fluorine atoms incorporation into the aromatic ring of 1-hydroxy-1-hydroperoxides was found to lead to their thermal stability increase. 1,1′-Dihydroxyperoxides are the less thermal stable than 1-hydroxy-1-hydroperoxides. Compared to the fluorine atoms, incorporation of fluoroalkyl groups into the aromatic ring exerts greater effect on the stability of the peroxide.     

Electrochemical activation and carboxylation of fluorine-containing aromatic imines

On the basis of a study of the processes involved in the electrochemical activation of a series of fluorine-containing aromatic imines with and without the presence of carbon dioxide it was shown that the initial stage of such processes is the formation of imine radical-anions, which can both undergo spontaneous transformations and react with CO₂ with the formation of fluorine-containing amino acids. A correlation was established between the effects of the electronic structure of the imines on the electrochemical characteristics of their reduction and on the stability of the radical-anions. A relationship was established between the parameters of electrochemical activation of the imines in the presence of CO₂ and the yields of the amino acids. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 265–271, September–October, 2008.     

Preparation and properties of fluorine-containing aromatic polyamides from tetrafluorophthaloyl chlorides and aromatic diamines

New fluorine-containing aromatic polyamides with inherent viscosities of 0.4–1.8 dL/g were prepared by the low temperature solution polycondensation of tetrafluoroisophthaloyl and tetrafluoroterephthaloyl chlorides with N,N′-bis(trimethylsilyl)-substituted aromatic diamines. The aromatic polyperfluoroisophthalamides were amorphous polymers with glass transition temperatures around 280°C, whereas the polyperfluoroterephthalamides were crystalline. Most of these aromatic polyamides were soluble in organic solvents, and began to decompose around 330°C in air or nitrogen atmosphere.     

Synthesis and characterization of fluorine-containing aromatic polyethers from tetrafluoroisophthalonitrile and bisphenols

New aromatic polyethers having inherent viscosities of 0.43–0.91 dL/g were synthesized by the phase-transfer catalyzed polycondensation of tetrafluoroisophthalonitrile with various hisphenols in a nitrobenzene-water system. All the polyethers were amorphous and soluble in N-methyl-2-pyrrolidone and nitrobenzene. They were cast into transparent and flexible films from the solutions. These polymers had glass transition temperatures around 130°C and dia not lose weight below 400°C in either air or nitrogen.     

Details of surface features in aromatic polyamide reverse osmosis membranes characterized by scanning electron and atomic force microscopy

In the present article, some new events on the surface morphology of the aromatic polyamide thin‐film‐composite (TFC) membranes were demonstrated in conjunction with their inherent chemical nature. In addition, the detailed, quantitative understanding of the microscopic surface features was shown to be essential in controlling the water permeability and eventually developing the high performance membranes. The surface roughness and the surface area were mainly affected by the existence or nonexistence of the crosslinking and/or the free amide groups not pertinent to the formation of the hydrogen bonding, which in turn contributed to the water permeability. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1429–1440, 1999     

Thermal expansion of aromatic polyamideimide composite films reinforced with aromatic polyamide fibers

Aromatic polyamideimide (PAI) films were reinforced by aromatic polyamide fibers as a unidirectionally oriented composite (Type I) and bidirectionally oriented laminate composite (Type II). The thermal expansion of the composite films was investigated with respect to the direction of fiber orientation. The thermal expansion behavior was anisotropic in the unidirectionally reinforced composite films, and considerably isotropic in the bidirectionally reinforced composite film. The thermal expansion coefficients based on thermoelastic models are calculated and compared with experimental data.     

Control on size and adsorptive properties of spherical ferric phosphate particles

Ferric phosphate particles were prepared by aging a solution dissolving Fe(ClO4)(3) and H3PO(4) at 40-80 degrees C for 16 h in a Teflon-lined screw-capped Pyrex test tube. The spherical or agglomerated fine particles were only precipitated with an extremely fast rate of reaction. The spherical particles were only produced at a very narrow region in fairly low pH solutions. TEM observation revealed that these particles grew in spherical structure by aggregation of primary small particles. The size of spherical particles was decreased by increase in the solute concentration or raising the aging temperature. Therefore, the formation of spherical particles was explained by a polynuclear layer mechanism proposed by Nielsen. The uniform spherical particles produced are amorphous, but they were crystallized to FePO(4) after calcining above 600 degrees C. It was suggested that the voids between the primary particles within the secondary agglomerated particles constitute mesopores. The Fe/P molar ratio determined and weight loss in TG curves gave the chemical formulas of the particles as Fe(PO4)x(H2PO4)y.nH2O (x: 0.93-1.00, y: 0-0.22, n: 2.4-2.7). The amorphous spherical ferric phosphate particles showed a high selective adsorption of H2O by penetration of H2O molecules into ultramicropores, produced after outgassing pretreatment, of that size is smaller than N2 molecule. The more particles grew, the more adsorption selectivity of H(2)O became remarkable.     

Thermal decomposition products of a chlorinated aromatic polyamide

Products from the thermal decomposition of a chlorinated aromatic polyamide fabric are described for conditions of pyrolysis and flaming and nonflaming oxidative degradation. Volatile degradation products were identified by gas chromatography-mass spectrometry (GC-MS) and the condensible fraction, by infrared (IR) spectroscopy, high-pressure liquid chromatography (HPLC), and MS. Nonvolatile char was characterized by IR and elemental analysis. Twenty-one compounds were identified as volatile products from pyrolysis at 550°C; the condensible material contained ammonium chloride and at least 22 organic compounds. From volatile compounds produced in flaming oxidative degradation 21 compounds were identified, of which CO, CO₂, and H₂O were prominent. Nonflaming oxidative degradation at 400 and 550°C produced 11 and 21 volatile identifiable compounds, respectively, and results from experiments at the higher temperature compared favorably with results from the flaming experiments. By comparison of data from this work with those from unchlorinated analogs (described in an earlier article), it is concluded that the incorporation of chlorine into the polymeric structure lowers the temperature for the onset of thermal degradation and alters the type and concentration of thermolytic products. The major degradation products can be explained by a mechanism similar to that proposed for aromatic polyamides with the exception of the formation of substantial amounts of ammonium chloride. It is proposed that the latter is formed by an initial acid-catalyzed hydrolysis reaction which is followed by deammoniation or by an intermolecular process that involves an isoimide intermediate.     

北京地区大气颗粒物中不同功能区多环芳烃的分布特征

用撞击式分级采样器同步采集了北京市城乡结合部、郊区的2003年四个季节的不同粒径大气颗粒物样品,用气相色谱-质谱分析了其中的多环芳烃。两个功能区的PAHs总质量浓度分布趋势均为：冬季>秋季>春季>夏季;不同环数PAHs在不同粒径颗粒物中的分配比例比较显示,粗颗粒物中2 环或3环PAHs的分配比例比其在高环PAHs的比例要大。     

Polarized infrared spectra of poled aromatic polyamide films

In connection with ferroelectric behavior of aromatic polyamides poled at a high electric field, polarized infrared spectra were studied in poled films of crystalline and amorphous aromatic polyamides consisting of ring systems to elucidate the relation between the orientation of polar groups and the ferroelectric polarization. The infrared spectra revealed that the CO and N H bonds oriented preferably along the poling direction in both crystalline and amorphous polyamides. The crystallinity of the crystalline polyamide increased with poling. In the amorphous polyamide, strong intermolecular hydrogen bonding is closely related to the retention of ferroelectric polarization in the frozen state of molecular motions below the glass transition temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 531–538, 1999     

Surface modification of aromatic polyamide film by oxygen plasma

The surface of poly(p-phenylene terephthalamide) (PPTA) films was modified by oxygen plasma, and the modified film surface was analyzed by an advancing contact meter and X-ray photoelectron spectroscopy (XPS). The advancing contact measurement showed that the oxygen plasma treatment made the surface of the PPTA film hydrophilic. The XPS analyses also showed the increase in the O/C and N/C atom ratio, especially the O/C atom ratio, at the PPTA film surface by the oxygen plasma treatment. A main oxygen functionality formed by the oxygen plasma treatment is a carboxylic acid group, and a main nitrogen functionality formed is a protonated amino group. The formation of the oxygen and nitrogen functionalities formed by the oxygen plasma treatment is not restricted to the surface of the PPTA film, but penetrates at least 35 Å deep from the film surface. The formation of these carboxylic acid and protonated amino groups is a result of the bond scission of the amide linkages in the PPTA film. Interactions of photons in the oxygen plasma rather than interactions of electrons and activated oxygen atoms contribute greatly to the bond scission. © 1995 John Wiley & Sons, Inc.     

Structural changes of aromatic polyamide nanofibers upon annealing treatment

Aromatic polyamide nanofibers with trifluoromethyl groups prepared using a precipitation polymerization method were annealed at various temperatures. The X-ray diffraction patterns and infrared spectra of the annealed products depended strongly on the annealing temperature. There was a transition in the temperature region of 250–300°C, where the conformation and the mobility of molecular chains changed significantly. Furthermore, the intermolecular hydrogen bonding increased, resulting in a higher degree of crystallinity. However, the morphology was unchanged. Meanwhile, the molecular structure and degree of crystallinity depended on the reaction period. However, those obtained by the annealing treatments above 250°C were the same.     

含氟芳杂环化合物的研究 7:含氟氮、硫杂二苯并王冠化合物的合成

本文研究了苯环上含强吸电子基的间硝基对氯三氟甲苯1与一些含氮、氧、硫的亲核试剂作用,经桥接、还原、关环,分别合成了含氟氮杂、硫杂王冠化合10牧11;还得到含氟三氮杂庚环化合物9,并对其生成机理进行了探讨,各步产率都较高.     

Soluble aromatic polyamide bearing ether linkages: synthesis and characterization

Soluble aromatic polyamide chains were prepared by reacting 4–4′-oxydianiline with isophthaloyl chloride in dimethylacetamide. To quench the HCl produced during the polymerization reaction, a stoichiometric amount of triethylamine was added. The precipitates formed were separated leaving behind clear polyamide resin. Thin and transparent film was obtained by evaporating the solvent and was subjected for Fourier transform infrared (IR), nuclear magnetic resonance (NMR), gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, water absorption, and mechanical analyses. The transparent film was found to be soluble in dimethylacetamide, dimethyl sulfoxide, and dimethylformamide. IR and NMR spectroscopic analyses confirmed the structure of the polyamide while the gel permeation chromatography revealed the formation of a high-molecular-weight polymer. Thermogravimetry, differential scanning calorimetry, water absorption, and mechanical testing were also performed to further verify its physical properties. A soluble aromatic polyamide was successfully synthesized by solution polymerization and characterized. The polyamide has film-forming property, and the film is transparent, mechanically strong, and thermally stable.     

Analysis of the products of thermal decomposition of an aromatic polyamide fabric

The thermal degradation of an aromatic polyamide was studied under conditions of pyrolysis and oxidative degradation at 550°C and of flaming combustion. Techniques described elsewhere were used to determine the volatile compounds quantitatively by gas chromatography-mass spectrometry (GC–MS). The condensible material and the solid residue were characterized by infrared spectroscopy and MS, and in pyrolysis experiments 28 compounds were identified (CO, CO₂, H₂O, and C₆H₅CN were the primary products). Collectively, these compounds accounted for 79% of the sample weight loss. The remaining 21% was a condensible material that contained at least 17 compounds; the two major components were 1,3-dicyanobenzene and 3-cyanobenzoic acid. Most of the nitrogen content of the polymer remained as involatile residue. This study was sufficiently detailed to obtain a mass balance between the composition of the original polymer and the sum of the observed pyrolysis products. The major products observed in pyrolysis experiments supported a mechanism that involved the cleavage of an aromatic-NH bond and the loss of H₂O to form aromatic nitriles. Hydrolysis of the amide linkage, followed by decarboxylation of the product acid, accounted for the high concentrations of CO₂ observed. Oxidative degradation at 450°C yielded ten identifiable compounds and an additional 19 volatile compounds were formed at 550°C. The condensible fraction, which contained at least 20 compounds, was similar in composition to the fraction collected from the pyrolysis experiments. The sum of the carbon content from the two major volatile products of oxidative degradation (CO and CO₂) and from the solid residue quantitatively accounted for the carbon content in the original sample. Flaming combustion studies revealed a markedly different product distribution than was observed under nonflaming conditions, especially in regard to the higher-molecular-weight species.