Synthesize procedures, mechanical and thermal properties of thiazole bearing poly(amid-imide) composite thin films containing multiwalled carbon nanotubes

This research is aimed at characterizing the thermal, mechanical, and morphological properties of carbon nanotubes (CNTs) reinforced poly(amide-imide) (PAI) composites having thiazol and amino acid groups which were prepared by sonication-assisted solution compounding. To increase the compatibility between the PAI matrix and CNTs, carboxyl-functionalized multiwall CNTs (MWCNTs-COOH) were used in this study. The MWCNTs were dispersed homogeneously in the PAI matrix while the structure of the polymer and the MWCNTs structure are stable in the preparation process as revealed by transmission electron microscopy. MWCNT/PAI composite films have been prepared by casting a solution of precursor polymer containing MWCNTs into a thin film, and its tensile properties were examined. The thermal stability, Young’s modulus, and tensile strength of PAI were greatly improved by the incorporation of MWCNTs and their good dispersion. Composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis.     

Preparation, characterization, and thermal properties of organoclay hybrids based on trifunctional natural amino acids

Nanohybrid materials prepared by the nanoscale incorporation of organic moieties into the interlayer spaces of layered inorganic hosts have attracted a great deal of interest because of their wide applications in industry and environmental protection. In this investigation, a simple and green method is reported for the preparation of novel trifunctionalized organoclays (OCs) using protonated form of acidic (aspartic and glutamic acid) and hydroxyl (serine and tyrosine) functionalized α-amino acids with Cloisite Na⁺. The synthesized OCs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and dispersibility measurement. X-ray diffraction results show that the basal spacing of the OCs increased with amino acids loading that affirm that the intercalation was successful. The morphology of these novel materials was examined by scanning electron microscopy, field emission scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis show that the quantity of organic modifier in the organo-bionanoclays is in good agreement with the theoretically calculated stoichiometric content expected for approximately entire exchange of Na⁺ ions by amino acid cations. These results are very important and relevant to the preparation of low-cost, biocompatible and biodegradable organo-nanoclays for industrial applications.     

Progress in Synthetic Polymers Based on Natural Amino Acids

α-Amino acids are one type of the main building blocks of living systems, being the primary components of all naturally occurring peptides and proteins. They are the simplest optically active compound in the nature and have multiple functional groups, which enable them to be transformed into a wide variety of optically active substances. The resulting materials show a wide variety of functions such as electron transfer, information transfer, photo reactivity and selective catalytic function, which cannot be imitated by synthetic compounds. Functional macromolecular materials using biological chiral resources such as amino acids have been drawing much interest due to their biocompatibility and biodegradability easing the ecological trouble because amino acid residues can be targeted for cleaving by different enzymes. Also, this type of polymer contains nitrogen, which the organism needs for their growth and shows excellent hydrophilic character, reasonably high melting points and good materials properties even at relatively low molecular weights. However, polymers composed of amino acids alone have limited thermal stability and are insoluble in many common organic solvents, which make these materials difficult to fabricate and utilize. Preparation of hybrid systems between conventional synthetic polymers and linear sequences of amino acids are interesting because amino acid segments possess unique properties, such as directional polarity, chirality and their capability to undergo specific noncovalent interactions. These properties can potentially be used for designing novel hierarchical superstructures with tunable material properties for a wide variety of applications. Herein, the synthesis and properties of synthetic macromolecules having natural amino acids are reviewed in details up to now with excluding polypeptides.     

Molten salt ionic liquid-assisted synthesis of nano-structured poly(amide imide)s based on 4,4′-methylenebis(3-chloro-2,6-diethyl trimellit imidobenzene) via microwave process as an environmentally friendly methodology

In this paper, for the first time, 4,4′-methylene-bis(3-chloro-2,6-diethyl trimellit imidobenzene) was prepared by the condensation reaction of 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) and trimellitic anhydride. A series of novel poly(amide imide)s was prepared by the direct polycondensation of the synthesized diimide diacid and various commercial diamines using tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent under microwave irradiation. Tetra-n-butylammonium bromide acts both as a solvent and a catalyst to mediate clean polymerization reactions to yield the desired polymers. The obtained polymers were characterized with FTIR, ¹H NMR, X-ray diffraction, field emission scanning electron microscopy, elemental and thermogravimetric analysis. The poly(amide imide)s were generally soluble in polar organic solvents, such as N,N′-dimethyl acetamide, N,N′-dimethylformamide, N-methyl-2-pyrrolidone and sulfuric acid at room temperature, and are insoluble in methylene chloride, cyclohexane and water. Morphology probes showed these macromolecules were non-crystalline and nano-structured polymers. The effect of ultrasonic irradiation on the surface morphology of polymers was studied and the results demonstrated that the morphology of macromolecules after ultrasonication became more homogenous than it is before ultrasonic radiation. On the basis of thermogravimetric analysis data, such polymers are thermally stable and can be classified as self-extinguishing polymers.     

Preparation and characterization of poly(vinyl alcohol)/organo-modified cloisite Na+ with chiral L-leucine amino acid/TiO2 nanocomposites

Poly(vinyl alcohol)/organo-clay/TiO₂ nanocamposites films were prepared with 10 wt % of organo-nanoclay and various amount of TiO₂ nanoparticles. Cloisite Na⁺ has been modified via cation exchange reaction using ammonium salt of natural L-leucine amino acid as a cationic surfactant. After that poly(vinyl alcohol)/organo-nanoclay/TiO₂ nanocomposites were synthesized by dispersion of TiO₂ on the surfaces of organo-nanoclay in poly(vinyl alcohol) matrix by using ultrasonic energy. Three nanocomposites with different loading of TiO₂ were prepared and characterized by X-ray diffraction, fourier transform infrared spectroscopy, field emission type scanning electron microscope, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and ultraviolet-visible transmission spectra. The results showed that the organo-nanoclay and TiO₂ were dispersed homogeneously in poly(vinyl alcohol) matrix and also showed improvement in their thermal properties compared with the pure poly(vinyl alcohol).     

Study on biodegradability of poly(amide-imide)s containing N-trimellitylimido-L-amino acids and 3,5-diamino-N-(pyridin-3-yl)benzamide linkages

A series of novel biodegradable functional amino acid-based poly(amide-imide)s (PAI)s were designed and synthesized by the direct polycondensation reaction of chiral bioactive diacids composed of naturally occurring α-amino acids with 3,5-diamino-N-(pyridin-3-yl) benzamide in the presence of molten tetrabutylammonium bromide as a green solvent. These new biodegradable polymers were characterized with Fourier transfer infrared and ¹H NMR spectroscopy, field emission scanning electron microscopy. In addition, in vitro toxicity and biodegradability behavior of the starting diacids, diamine and obtained PAIs were investigated in culture media and the results showed that the synthesized monomers and their derived polymers are biologically active and their degradation products are probably nontoxic to microbial growth.     

A facile, microwave-assisted synthesis of novel optically active polyamides derived from 5-(3-methyl-2-phthalimidylpentanoylamino)isophthalic acid and different diisocyanates

5-(3-Methyl-2-phthalimidylpentanoylamino)isophthalic acid as a novel aromatic diacid monomer was prepared in three steps. In the first step, phthalic anhydride was reacted with l-isoleucine in acetic acid solution, and the resulting imide acid was obtained in high yield. In the second step, treatment of this imide acid with excess thionyl chloride gave aliphatic acid chloride in good yield. In the last step, this acid chloride was reacted with 5-aminoisophthalic acid to provide novel bulky chiral aromatic diacid monomer. The direct polycondensation reactions of this diacid with several aromatic and aliphatic diisocyanates such as 4,4′-methylenebis(phenyl isocyanate), toluylene-2,4-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate were carried out under microwave irradiation. In order to compare this method with classical heating, the polymerization reactions were also performed under solution polycondensation conditions. The polymerization reactions occurred rapidly under microwave conditions and produced a series of novel optically active polyamides (PA)s containing pendent phthalimide group, with good yields and moderate inherent viscosities of 0.17-0.60 dL/g. Some of the new PAs showed good solubility and are readily soluble in organic solvents. The resulting macromolecules were characterized by FT-IR, specific rotation, and representative ones by ¹H NMR, elemental and thermogravimetric analyses (TGA).     

Microwave-assisted clean synthesis of aromatic photoactive polyamides derived from 5-(3-acetoxynaphthoylamino)-isophthalic acid and aromatic diamines in ionic liquid

Dicarboxylic acid, 5-(3-acetoxynaphthoylamino)isophthalic acid was prepared in three steps. The direct polycondensation of this novel diacid with several aromatic diamines was studied in 1,3-diisopropylimidazolium bromide as an ionic liquid (IL) under microwave irradiation and conventional heating. The polymerization reaction was effectively preceded in IL, and triphenyl phosphite as an activating agent, and the resulting novel photoactive polyamides were obtained in high yields and moderate inherent viscosities in the range of 0.44-0.69 dL/g. Thermogravimetric analysis showed that polymers are thermally stable, 10% weight loss temperatures in excess of 390 and 470 °C, and char yields at 600 °C in nitrogen higher than 60%. These macromolecules exhibited maximum UV-vis absorption at 265 and 300 nm in N,N-dimethylformamide (DMF) solution. Their photoluminescence in DMF solution demonstrated fluorescence emission maxima around 361 and 427 nm for all of the polyamides. It is very important to note that, because of, high polarizability of ILs, they are very good solvents for absorbing microwaves.     

Antimicrobial,mechanical, optical and thermal properties of PVC/ZnO‐EDTA nanocomposite films

Covalent surface functionalization of synthesized ZnO nanoparticles (NP)s with ethylenediaminetetraacetic acid (EDTA) was successfully carried out. Modified ZnO‐EDTA NPs as a viable and inexpensive filler were incorporated into poly(vinyl chloride) PVC matrix after their chemical modification to investigate the agglomeration behavior. All prepared materials including modified NPs and PVC/ZnO‐EDTA nanocomposites (NC)s were analyzed by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, X‐ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. Fabricated PVC/ZnO‐EDTA NCs were reported to have high transparency and improved mechanical properties compared with PVC. Modified ZnO and the fabricated NCs were shown to exhibit excellent antibacterial activity against two bacteria species: Escherichia coli and Staphylococcus aureus. The obtained NCs could be considered as self‐extinguishing materials on the basis of the LOI values. Copyright © 2016 John Wiley & Sons, Ltd.