Functional Aromatic Polyamides

We describe herein the state of the art following the last 8 years of research into aromatic polyamides, wholly aromatic polyamides or aramids. These polymers belong to the family of high performance materials because of their exceptional thermal and mechanical behavior. Commercially, they have been transformed into fibers mainly for production of advanced composites, paper, and cut and fire protective garments. Huge research efforts have been carried out to take advantage of the mentioned characteristics in advanced fields related to transport applications, optically active materials, electroactive materials, smart materials, or materials with even better mechanical and thermal behavior.

The fabrication and characterization of nanocomposites containing new poly(amide–imide) based on 4,4-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) and carboxylic acid-functionalized multiwalled carbon nanotubes

In this article, a nanostructure poly(amide–imide) (PAI) was prepared from the polymerization of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) with 3,5-diamino- N-(4-hydroxyphenyl)benzamide using tetra- n-butylammonium bromide as a green media and triphenylphosphite as a condensing agent. This methodology is safe and green since toxic and volatile organic solvents were eliminated. To obtain a homogeneous dispersion of multiwalled carbon nanotubes (MWCNTs) in the PAI matrix, carboxyl-modified MWCNT (CA-MWCNT) was used. The resulting nanocomposites were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and thermogravimetric analysis. TEM and FESEM results confirm good dispersion of CA-MWCNTs in the polymer matrix.

Organosoluble and optically active polyamides based on axially asymmetric 9,9′-spirobifluorene moieties

Optically active polyamides containing axially asymmetric 9,9′-spirobifluorene units in the main chain were synthesized for the first time by low-temperature solution polycondensation of ( R)-2,2′-bis(4-amino-2-trifluoromethylphenoxy)-9,9′-spirobifluorene with various diacyl chlorides. All these polymers were obtained in quantitative yields with inherent viscosities of 0.28–0.43 dL g−1. These polyamides were amorphous and readily soluble in many organic solvents such as N-methyl-2-pyrolidone, N, N-dimethylacetamide (DMAc), dimethyl sulfoxide, and tetrahydrofuran. The glass transition temperatures of these polyamides were recorded in the range of 199–261°C by differential scanning calorimetry, and the 10% weight loss temperatures were over 410°C both under nitrogen and in air atmospheres. The specific rotations of these chiral polyamides oscillated between 65.0° and 127.8° depending on the structures of the diacid chlorides. All the optically active polymers exhibited high chiral stability in solid state or in DMAc solvent at high temperature due to incorporation of chiral spirobifluorone unit in polymer backbones. The ultraviolet–visible and circular dichroism spectroscopic properties of these chiral polyamides in solutions were also studied.

Investigating thermophysical properties of novel chiral nanostructured poly(amide-ester-imide)s containing different amino acids based on biological active N, N′-(pyromellitoyl)-bis-l-amino acids and diol

Preparation of potentially biodegradable poly(amide-ester-imide)s (PAEI)s with different amino acids was described. For the first time, the synthesis of diol N, N′-(1,3,5,7-tetraoxo-5,7-dihydropyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)bis(4-hydroxybenzamide) (diol 4) was recounted. The diol 4 was supplied by Vitas-M Laboratory, Ltd (Moscow, Russia). The key monomer applied in this project was diol 4. The direct polycondensation reaction of several chiral diacids (3A–3D) with aromatic diol 4 was carried out in a system of tosyl chloride, pyridine, and N,N-dimethyformamide. All the above PAEIs were characterized by proton nuclear magnetic resonance, Fourier transform infrared (FT-IR), elemental analysis, specific rotation techniques, x-ray diffraction, and field emission scanning electron microscopy (FE-SEM). Thermogravimetric analysis was used to study thermal properties of PAEIs. The FE-SEM of the aforementioned PAEIs indicated that these polymers were nanostructured particles. These polymers contain bioactive amino acids and diol units possibly with potential applications as biodegradable and biocompatible agents.

Study on constructional design and structural analysis of poly(amide-imide)/ZnO nanocomposites containing pyromellitoyl-bis-l-isoleucine moieties

Hybrid nanocomposites (NCs) produced by the dispersion of zinc oxide (ZnO) nanoparticles (NPs) in thermoplastic poly(amide-imide)s (PAIs) are designed and synthesized using ultrasonic-assisted technology. ZnO NPs were functionalized with 3-aminopropyltriethoxysilane (KH550) coupling agent to increase the hydrophobic nature of NPs. Reaction of diamine containing N-(4-hydroxyphenyl) benzamide and a diacid chloride comprising pyromellitoyl-bis-l-isoleucine segments at low temperature provided the polymeric matrix with well-designed groups. Surface treatments of ZnO NPs gave a better dispersion and enhancing possible interactions of NPs with functional units of polymer matrix. The surface-modified ZnO NPs were dispersed uniformly in the PAIs matrix using ultrasonic irradiation. The obtained NCs were characterized by Fourier-transform infrared spectroscopy, x-ray powder diffraction, atomic force microscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis. The FE-SEM and TEM pictures confirmed the globular-like structures for NCs.

Novel optically active poly(amide-thioester-imide)s containing l-α-amino acids and thiadiazol anticorrosion group

Here, for the first time, we report the synthesis of a new class of optically active polymers, poly(amide-thioester-imide)s (PATEI)s, containing flexible and anticorrosion linkages. Step growth polymerization of a novel diamine with diacids containing amino acid and trimellitylimide groups in tetrabutylammonium bromide, in the molten state, which acts as a molten ionic salt medium, was carried out. The obtained polymeric materials were of the nanoscale size and were assembled by filamentary particles as shown by field-emission scanning electron microscopy micrographs, which were distributed uniformly and randomly, with an average nanosize diameter of about 40 nm. The polymeric samples were readily soluble in a variety of common organic solvents and formed low-colored and flexible thin films via solution casting. The values of absorption edge wavelength ( λ0) were determined by ultraviolet–visible spectroscopy, and all of the resulting PATEI films exhibited high-optical transparency. According to x-ray diffraction patterns, all the PATEIs were amorphous. The structure of PATEIs were also characterized by Fourier-transform infrared spectroscopy, Proton-nuclear magnetic resonance, elemental, and thermogravimetric analysis techniques. The effect of ultrasound on the morphology of polymers was also investigated. This study confirmed that the size of polymer particles decreased and there was a change in their morphology.

Poly(amide-imide)s obtained from 3,5-diamino-N-(thiazol-2-yl)-benzamide and dicarboxylic acids containing various amino acid units

This study reports a green approach toward the synthesis of novel optically active poly(amide-imide)s (PAI)s bearing thiazole moiety, which was formed by the polycondensation reaction of 3,5-diamino- N-(thiazol-2-yl)benzamide and various diacids containing natural amino acids in molten tetrabutylammonium bromide. Diamine monomer was synthesized by the reduction of 3,5-dinitro- N-(thiazol-2-yl)benzamide in methanol using iron oxide hydroxide as a catalyst. This catalyst can rapidly reduce the sulfur and azo-containing aromatic nitro compounds to the corresponding amines in high yield by employing hydrazine hydrate as a hydrogen donor. Chiral diacid monomers were synthesized in high yield through the reaction of pyromellitic dianhydride and amino acids (l-isoluecine, S-valine, S-methionine, and l-phenylalanine) in acetic acid. The direct polymerization reactions of these monomers provided a series of new optically active PAIs with inherent viscosities in the range of 0.20–0.28 dL g−1. The obtained polymers were characterized by Fourier-transformed infrared spectroscopy, specific rotation measurements, and the representative of them by proton nuclear magnetic resonance and elemental analysis techniques.