Synthesis, characterization, and water sorption properties of new aromatic polyamides containing benzimidazole and ethylene oxide moieties

Ultrahigh strength and modulus copolyamide films with uniaxially cold-drawing induced molecular orientation

The tensile strength of polymer films is generally lower than 200 MPa. Copolyamide (CPA) films with ultrahigh strength (approximately 317–865 MPa) and high modulus (approximately 3.96–11.76 GPa) were obtained by uniaxial cold-drawing and heat treatment. The relationship between structures and properties in the orientation state was also investigated. The results of Fourier transform infrared (FTIR) spectroscopy indicate that hydrogen bonding interactions change a little with drawing. Wide-angle X-ray diffraction patterns show orientational stretch induces π–π ordered packing after drawing 100%. The tensile strength and modulus of the drawn CPA films are improved approximately 41%–173% and 9%–197% compared to undrawn films. Dichroic ratios obtained under polarized FTIR spectroscopy represent overall orientation factors. The decrease of dichroic ratios at about 3300 cm−1 and 1650 cm−1 and the increase of dichroic ratios at 1515 cm−1 prove that the orientation of macromolecular chains is improved along stretch direction. What’s more, the degree of orientation is further increased after heat treatment, which is the phenomenon of spontaneous orientation. The degree of spontaneous orientation increases with the increase of cold-drawing ratio. Thus, the initial orientation in cold-drawing and spontaneous orientation during heat treatment leads to ultrahigh modulus and high strength.

Highly CO2-Selective Gas Separation Membranes Based on Segmented Copolymers of Poly(Ethylene oxide) Reinforced with Pentiptycene-Containing Polyimide Hard Segments

Poly(ethylene oxide) (PEO)-containing polymer membranes are attractive for CO2-related gas separations due to their high selectivity toward CO2. However, the development of PEO-rich membranes is frequently challenged by weak mechanical properties and a high crystallization tendency of PEO that hinders gas transport. Here we report a new series of highly CO2-selective, amorphous PEO-containing segmented copolymers prepared from commercial Jeffamine polyetheramines and pentiptycene-based polyimide. The copolymers are much more mechanically robust than the nonpentiptycene containing counterparts due to the molecular reinforcement mechanism of supramolecular chain threading and interlocking interactions induced by the pentiptycene structures, which also effectively suppresses PEO crystallization leading to a completely amorphous structure even at 60% PEO weight content. Membrane transport properties are sensitively affected by both PEO weight content and PEO chain length. A nonlinear correlation between CO2 permeability with PEO weight content was observed due to the competition between solubility and diffusivity contributions, whereby the copolymers change from being size-selective to solubility-selective when PEO content reaches 40%. CO2 selectivities over H2 and N2 increase monotonically with both PEO content and chain length, indicating strong CO2-philicity of the copolymers. The copolymer film with the longest PEO sequence (PEO2000) and highest PEO weight content (60%) showed a measured CO2 pure gas permeability of 39 Barrer, and ideal CO2/H2 and CO2/N2 selectivities of 4.1 and 46, respectively, at 35 °C and 3 atm, making them attractive for hydrogen purification and carbon capture.

Highly efficient microwave-assisted synthesis of photoactive polyamides bearing 5-(3-acetoxynaphthoylamino)benzamide moieties

A novel aromatic dicarboxylic acid monomer, 5-[4-(3-acetoxynaphthoylamino)benzoylamino]isophthalic acid, was prepared in five steps. The direct polycondensation of this dicarboxylic acid with several aromatic diamines was performed under microwave irradiation and conventional heating in the presence of triphenyl phosphite/pyridine/ N-methyl-2-pyrrolidone/calcium chloride. The polymerization reactions were effectively preceded, and the resulting novel photoactive polyamides (PAs) were obtained in high yields and moderate inherent viscosities in the range of 0.32–0.58 dL g−1. Thermogravimetric analysis results showed that polymers were thermally stable, 10% weight loss temperatures were in excess of 430°C and 488°C, and char yields at 800°C under nitrogen atmosphere were higher than 62%. The resulting polymers exhibited ultraviolet–visible absorption bands at 268 and 312 nm in N,N-dimethylformamide (DMF) solution. Their photoluminescence in DMF solution demonstrated fluorescence emission bands maxima around 367 and 429 nm for all of the PAs.

Synthesis and characterization of aromatic poly(amides) based on 3,5-diamino-N-cyclopropylbenzamide

Three aromatic poly(amides) (PAs) were prepared, one of them containing a dimethyldiphenylsilane unit from a new aromatic diamine monomer with a bulky pendant polar group.

Silicon-containing oligomeric poly(imido-amides) with amino moieties. Synthesis, characterization and thermal studies

Silicon-containing oligomeric poly(imido-amides) (PIAs) were synthesized from dicarboxylic imido-acids containing a Si atom, which were obtained from dianhydrides, amino acids and p-aminobenzoic acid, were polymerized with the diamine bis(4-aminophenyl)diphenylsilane.

Preparation of novel pyridine-based poly(ether amide)s via three different routes and investigation of their properties

A new diamine was prepared via two successive reactions: 6-chloronicotinoyl chloride was reacted with 4,4′-oxydianiline and the obtained dichloro product was reacted with 5-amino-1-naphthol. A novel series of poly(ether amide)s containing flexible ether groups, pyridine polar units, and bulky naphthyl units was prepared through polycondensation reactions of the diamine with four diacids via three different routes. Polyamides were prepared by phosphorylation reaction, indirect diacid chloride reaction, and using ionic liquid medium. The effect of reaction conditions on the physical and thermal properties of the polymers such as solution viscosity, solubility, crystallinity, thermal stability, and thermal behavior were investigated.

Antioxidant activity of new aramide nanoparticles containing redox-active N-phthaloyl valine moieties in the hepatic cytochrome P450 system in male rats

We report the synthesis of aramide nanoparticles containing a chiral N-phthaloyl valine moiety and their antioxidant activities on hepatic contents of cytochrome P₄₅₀, amidopyrene N-demethylase, aniline-4-hyroxylase and induced the hepatic content of cytochrome b5 and nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C-reductase. Polymers were obtained as well-separated spherical nanoparticles while highly aggregated particles via H-bonding organization of the aramide-containing pyridine led to a thin layer formation. The effects of the nanoparticles and CCl₄ on enzyme activities and thiobarbituric acid reactive substances (TBARS) levels of male rat liver were studied. Pretreatments of rats with the polyamides prior to the administration of CCl₄ decreased the hepatic content of the tested enzymes. Doses reduced the toxic effects exerted by (•CCl₃) upon the liver through inhibition of the cytochrome P₄₅₀ system. Inhibition of such metabolizing enzymes could reduce the carcinogenic effects of chemical carcinogens.

Silicon-containing oligomeric poly(amides) with phthalimidyl-amide side groups: synthesis, characterization and thermal studies

Oligomeric poly(amide)s (PAs) were synthesized from monomeric diacids, which were obtained from phthalic anhydride and the amino acid glycine, l-alanine, l-phenylalanine, l-valine, l-leucine, l-isoleucine and p-aminobenzoic acid. The phthalimidyl acids (IA-1 to IA-7) reacted with 5-amino-isophthalic acid in order to obtain the monomeric diacids (1-7). Furthermore, the monomeric diacid 8 was obtained by direct reaction between phthalic anhydride and 5-amino-isophthalic acid. The isophthalic acid derivatives were reacted with bis(4-aminophenyl)diphenylsilane in order to obtain the PAs. Monomers and polymers were characterized by infrared and 1H-, 13C- and 29Si-NMR spectroscopy, elemental analysis and, when necessary, optical rotation. The results were in agreement with the proposed structures. The yields were generally good, but the ηinh values were low, indicating that the polymers were of oligomeric nature, namely, a chain of moderate molecular weight. The polymers were soluble in polar aprotic solvents and some of them were soluble in m-cresol and tetrahydrofuran. The glass transition temperatures ( Tg) values were obtained by differential scanning calorimetry, showing, in general, a decrease in value when the volume of the side chain of the amino acid moiety was increased. The thermal stability of the polymers was determined by dynamic thermogravimetry, showing good values of thermal decomposition temperatures (TDT), especially for those with aromatic residue in the amino acid, and for PA without amino acid. For PAs in which the side chain of the amino acid was larger, the TDT values were lower, probably due to the lack of symmetry and the length of the side chain, both of which have influence on the thermal stability.

Synthesis and characterization of new organosoluble aromatic polyamides and polyazomethines containing pendent pentadecyl chains

New aromatic polyamides and polyazomethines containing pendent pentadecyl chains were synthesized by polycondensation of pentadecylbenzene-1,3-diamine with (i) four commercially available aromatic diacids, viz., biphenyl-4,4′dicarboxylic acid, 4,4′-oxybisbenzoic acid, terephthalic acid and isophthalic acid, and (ii) dialdehydes, viz., terephthaldehyde, isophthaldehyde and a 50 : 50 mol% mixture of terephthaldehyde, and isophthaldehyde, respectively. Inherent viscosities of polyamides and polyazomethines were in the range 0.35–0.56 dL g−1 and 0.33–0.38 dL g−1, respectively, indicating the formation of medium molecular weight polymers. The presence of pendent pentadecyl chains in polyamides and polyazomethines led to an improvement in their solubility in organic solvents. Polyamides could be cast into flexible, transparent and tough films from their solution in N, N-dimethylacetamide while polyazomethines could be solution cast into transparent, flexible and stretchable films from their CHCl3 solution. 1H-NMR studies based on amide proton signals and azomethine proton signals indicated the presence of constitutional isomerism in the polyamides and polyazomethines. Wide-angle X-ray diffraction patterns exhibited broad halo indicating that the polymers were amorphous in nature. X-ray diffractograms also displayed sharp reflections in the small angle region (2 θ ≈ 3°) indicating the formation of layered structure arising from packing of flexible pentadecyl chains. The glass transition ( Tg) temperatures of polyamides were in the range 169–215 °C while Tg values for polyazomethines were in the range 16–55 °C. The temperature for the 10% weight loss of polyamides and polyazomethines were in the range 430–460 °C and 425–440 °C, respectively, in a nitrogen atmosphere, which indicated their good thermal stability. Polyazomethines were also characterized by UV-Vis and photoluminescence spectroscopy and optical band gap ( Eg) values, calculated according to the maximum of the UV absorption, were found to be in the range 2.82–3.10 eV.