Fast synthesis of optically active polyamides containing l-methionine linkages in ionic liquid via a microwave-assisted process
ABSTRACT Several optically active aromatic polyamides have been synthesized via direct polycondensation of chiral diacid monomer 1 containing l-methionine moiety with diverse aromatic diamines 2a–2h in a green medium, namely 1,3-dipropylimidazolium bromide as a room temperature ionic liquid. In order to evaluate the advantages
of microwave promotion of these polymerization reactions, we compared microwave irradiation (method I) with conventional oil
bath heating (method II) by means of reaction rates, conversions, and inherent viscosities. The inherent viscosities of resulting
polymers were ranging between 0.47–0.65 and 0.35–0.57dL/g in methods I and II, respectively. These polymers were characterized by means of 1H-NMR, FT-IR, elemental, organosolubility, differential scanning calorimetry, and thermal gravimetric analysis techniques.
The obtained polymers show thermal stability up to 273 °C under nitrogen atmosphere and good solubility in polar organic solvents.
Polymerization reactions proceeded in higher yields and moderate inherent viscosities under microwave irradiation conditions
besides the dramatically shorter reaction times and achieving the more pure products.
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ABSTRACT: Electrochemical characterization of two different samples of an activated membrane, which consists of a polymeric support containing different amounts of Di-(2-ethylhexyl) phosphoric acid as a carrier, was made by measuring the electrical resistance, salt diffusion and membrane potential for the activated membranes and the polymeric support in contact with NaNO3 solutions. Transport parameters such as the ion transport numbers and concentration of fixed charge in the membrane, salt and ionic permeabilities at different NaNO3 concentrations were obtained. A comparison of the different electrochemical parameters obtained with both activated membranes and the polymeric support shows how the carrier affects the transport of NaNO3 solutions across the activated membranes. On the other hand, chemical composition of the membrane surfaces as a function of the amount of carrier was determined by X-ray photoelectron spectroscopy technique, which also allows an envisagement of the chemical bonding between the carrier and the membrane top layer (polyamide).Journal of Membrane Science 01/1999; 156(2):241-250. · 4.09 Impact Factor
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ABSTRACT: 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.Colloid and Polymer Science 01/2007; 285(15):1749-1754. · 2.16 Impact Factor
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ABSTRACT: Various approaches have been carried out in the synthesis of poly(amide-imide)s. A well-developed solution polycondensation method has been used to prepare such copolymers either from a dianhydride containing a preformed amide group with a diamine or from a dicarboxylic acid containing a preformed imide ring with a diamine. Direct polycondensations of carboxylic acids and aromatic diamines can be a more useful technique for synthesis of poly(amide-imide)s PAIs. In this work, direct polymerization reaction of N,N’-(4,4’-hexafluoroisopropylidendiphthaloyl)-bis-L-isoleucine with several aromatic diamines such as 4,4’-diaminodiphenylsulphone (4a), 4,4’-diaminodiphenylmethane (4b), 4,4’-diaminodiphenylether (4c), 1,4-phenylenediamine (4d), 4,4’-diaminobiphenyl (4e), 1,3-phenylenediamine (4f), 2,4-diaminotoluene (4g), was performed in the presence of tosyl chloride (TsCl)/dimethylformamide (DMF)/pyridine (Py) as a condensing agent. The resulting PAIs were obtained in high yield and inherent viscosity. Some structural characterization and physical properties of these polymers have been studied and will be reported.Polymer Bulletin 01/2006; 56(4):339-347. · 1.33 Impact Factor