Construction, Characterization and Biological Activity of Chiral and Thermally Stable Nanostructured Poly(Ester-Imide)s as Tyrosine-Containing Pseudo-Poly(Amino Acid)s

In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, ¹H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils.     

Environmentally Friendly Methodology for Preparation of Amino Acid Containing Polyamides

A short and green method for the preparation of optically active aromatic polyamides (PAs) using tetrabutylammonium bromide (TBAB) as a molten ionic liquid is reported. Polycondensation reactions of amino acid containing diacid (2S)-5-(4-methyl-2-phthalimidylpentanoylamino)isophthalic acid with various commercially available diisocyanates in molten TBAB as a green medium or in N-methylpyrrolidone as common organic solvent with or without dibutyltin dilaurate as a catalyst under microwave irradiation were carried out. Various PAs were obtained with high yields and moderate inherent viscosities in the rang of 0.30–0.57 dL/g. The obtained polymers were characterized by FT-IR, specific rotation measurements, and representative of them by ¹H NMR and elemental analysis techniques. Thermal properties of PAs were evaluated by thermogravimetric analysis and the results showed that the 10% weight loss temperature in a nitrogen atmosphere for four representative samples were more than 258 °C, which indicates that the resulting PAs have good thermal stability as well as excellent solubility.     

Synthesis and Characterization of Novel Heat Stable and Processable Optically Active Poly(Amide–Imide) Nanostructures Bearing Hydroxyl Pendant Group in an Ionic Green Medium

Ionic liquids (IL)s have been recognized as ‘green’ alternatives to the organic solvents in a range of synthesis, catalysis and electrochemistry due to their unique chemical and physical properties. In this investigation, a series of organosoluble, thermally stable and optically active hydroxyl-containing poly(amide–imide)s (PAI)s were prepared via polycondensation reaction of an aromatic diamine, 3,5-diamino-N-(4-hydroxyphenyl)benzamide (4), and different chiral amino acid-based diacids (3a–3e) in the presence of molten tetrabutylammonium bromide as a molten IL and triphenyl phosphite under classical heating method. This process is safe and green since toxic and volatile organic solvents such as N-methylpyrrolidone (NMP) and N,N′-dimethylacetamide (DMAc) were eliminated. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.23 and 0.54 dL g^?1 and were characterized by Fourier transform infrared spectroscopy, specific rotation, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis, elemental analysis, and in some cases by ¹H-NMR techniques. The FE-SEM micrographs and XRD showed that the synthesized PAIs were nanostructured and amorphous polymers. The effect of ultrasonic irradiation on the size of polymer particles was also investigated and the results showed that the size of polymer nanoparticles after ultrasonication became smaller than the size of them, before ultrasonic radiation. All of the polymers were readily soluble in many organic solvents such as N,N′-dimethyl sulfoxide, DMAc and NMP.     

Synthesis and Properties of Biodegradable Poly(vinyl alcohol)/Organo-nanoclay Bionanocomposites

Biodegradable nanocomposites comprising of biodegradable polymers and bioactive organically modified layered silicates commonly reveal extremely enhanced mechanical and various other properties when compared to those of virgin polymers. This work was undertaken with a view to preparation of polymer bionanocomposites consisting of biodegradable poly(vinyl alcohol) (PVA) and organo-nanoclay. Cloisite Na⁺ and ammonium salt of l-isoleucine amino acid was used for the preparation of the novel chiral organo-nanoclay via an intercalation reaction in an aqueous solution. PVA/organo-nanoclay bionanocomposites of various compositions were created through the solution intercalation method by ultrasound-assisted technique. The resulting novel materials were characterized by X-ray diffraction and Fourier transform infrared spectroscopy techniques. Thermogravimetric analysis (TGA) and UV/vis spectroscopy were applied to test the properties of PVA bionanocomposites. TGA indicate that the thermal stability is enhanced distinctly, without a sacrifice in optical clarity. The improvement of thermal properties was attributed to the homogeneous and good dispersion of organo-nanoclay in polymeric matrix and the strong hydrogen bonding between O?CH groups of PVA and the oxygen atoms of silicate layers or carbonyl group as well as OH group of intercalated amino acid. The morphology of the organo-nanoclay and PVA bionanocomposites was examined by scanning electron microscopy and transmission electron microscopy techniques. Uniform distribution of clay due to intimate interaction between clay and polymer appears to be the cause for improved properties.     

Citric Acid and Vitamin C as Coupling Agents for the Surface Coating of ZrO<Subscript>2</Subscript> Nanoparticles and Their Behavior on the Optical,Mechanical, and Thermal Properties of Poly(vinyl alcohol) Nanocomposite Films

A series of bio-nanocomposites (BNC)s were fabricated through solution casting method. At first, the surfaces of ZrO₂ NPs were functionalized with citric acid and Vitamin C as green modifier agents. Then, PVA as polymer matrix was embedded with different contents (4, 8 and 12 wt%) of modified ZrO₂ (m-ZrO₂) NPs with the aim of ultrasonic irradiation process. The resulting BNCs were studied by various techniques. Thermal stability of obtained BNCs was enhanced after NPs’ addition to the PVA matrix. Optical activity of these new BNCs makes them potential candidate for UV shielding material. Lastly, the tensile strengths of the BNCs were increased in comparison to the pure PVA.     

Ionic Liquids as Environmentally Friendly Solvents in Macromolecules Chemistry and Technology,Part I

With the increasing emphasis on the environment and the need to find environmentally friendly solvent systems, ionic liquids (IL)s have been emerging as promising green solvents to replace conventional solvents in recent years. They possess unique properties such as nonvolatility, low toxicity, ease of handling, nonflammability and high ionic conductivity; thus they have received much attention as green media for various chemistry processes. This report provides an extensive overview of use of ILs in polymers chemistry and technology.     

Novel Biobased Polyurethanes Synthesized from Nontoxic Phenolic Diol Containing l-Tyrosine Moiety Under Green Media

Ionic liquids (ILs) have been accepted as ‘green’ alternatives to the organic solvents in a range of synthesis, catalysis and electrochemistry, because of their distinctive chemical and physical properties. In this investigation, N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a chiral bioactive diphenolic monomer was prepared in three steps. The polycondensation of this monomer with various aromatic and aliphatic diisocyanates such as 4,4′-methylene-bis-(4-phenylisocyanate) (6a), toluylene-2,4-diisocyanate (6b), isophorone diisocyanate (6c) and hexamethylene diisocyanate (6d) were carried out in the presence of tetrabutylammonium bromide as a molten IL under microwave irradiation conditions and was compared with polymerization in traditional solvent like N-methyl-2-pyrrolidone. The results show that IL efficiently absorbs microwave energy, thus leading to a very high heating rate. Thus IL method is safe and green since toxic and volatile organic solvents were eliminated. All of the novel poly(urethane-imides) (PUIs) showed good solubility in various organic solvents. The obtained new polymers were characterized with FT-IR, ¹H-NMR, elemental and thermogravimetric analysis techniques. Thermogravimetric analysis (TGA) of two representative PUIs demonstrated that they are rather thermally stable. In vitro toxicity studies showed that the synthetic materials are biologically active and they are nontoxic to microbial growth then could be classified as bioactive and biodegradable compounds.     

Ionic Liquids as Environmentally Friendly Solvents in Macromolecules Chemistry and Technology,Part II

With the increasing emphasis on the environment and the need to find environmentally friendly solvent systems, ionic liquids (IL)s have been emerging as promising green solvents to replace conventional solvents in recent years. They possess unique properties such as nonvolatility, low toxicity, ease of handling, nonflammability and high ionic coductivity; thus they have received much attention as green media for various chemistry processes. This report provides an extensive overview of use of ILs in polymers chemistry and technology.     

An electrochemical nanocomposite modified carbon paste electrode as a sensor for simultaneous determination of hydrazine and phenol in water and wastewater samples

In this study, we report preparation of a high sensitive electrochemical sensor for determination of hydrazine in the presence of phenol in water and wastewater samples. In the first step, we describe synthesis and characterization of ZnO/CNTs nanocomposite with different methods such as transmission electron microscopy (TEM) and X-ray diffraction (XRD). In the second step, application of the synthesis nanocomposite describes the preparation of carbon paste electrode modified with n-(4-hydroxyphenyl)-3,5-dinitrobenzamide as a high sensitive and selective voltammetric sensor for determination of hydrazine and phenol in water and wastewater samples. The mediated oxidation of hydrazine at the modified electrode was investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k) and diffusion coefficient (D) for hydrazine were calculated. Square wave voltammetry (SWV) of hydrazine at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 8.0 nmol L^?1. SWV was used for simultaneous determination of hydrazine and phenol at the modified electrode and quantitation of hydrazine and phenol in some real samples by the standard addition method.     

Novel Bioactive Chiral Poly(amide–imide)s Containing Different Amino Acids Linkages: Studies on Synthesis, Characterization and Biodegradability

In this paper chiral bioactive poly(amide–imide)s (PAI)s were synthesized from four different diacids containing chiral amino acids with 4,4′-methylene bis(3-chloro 2,6-diethylaniline) as a diamine via direct polycondensation reaction in a system of tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent. The structures of these polymers were confirmed by FT-IR, ¹H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA showed that the 10 % weight loss temperature in a nitrogen atmosphere was more than 378 °C, which indicates that the resulting PAIs have a good thermal stability. The biodegradability of the monomers and prepared polymers was investigated in culture media and soil burial test for assessment of the susceptibility of these compounds to microbial degradation. The results showed that the synthesized monomers and theirs derived polymers are biologically active and nontoxic to microbial growth.