El-Sayed M. E. Mansour

Synthesis and characterization of thermally stable aromatic polyamides and poly (1,3,4-oxadiazole-amide)s nanoparticles containing pendant substituted bezamides

BackgroundThe introduction of pendent bulky groups along the polymer backbone results in a less ordered polymer matrix and increases the solubility characteristics without affecting thermal properties. The inclusion of chromogenic chemical moieties in the chains can give rise to the luminescent converter material which permits the preparation of materials with potential applications. Aromatic polymers containing heterocyclic rings in the main chain are known for their high thermal resistance, good hydrolytic stability, low dielectric and tough mechanical properties. There is currently much research directed towards the discovery of new blue light-emitting polymers, with characteristics of high efficiency and high reliability. Herein, we describe the preparation of aromatic polyamides and poly (1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups, where the acetoxybenzamide groups act as signaling units due to their fluorescent and chromogenic characteristics.ResultsAromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups were successfully prepared and characterized using different analytical methods. Most polyamides were obtained as well-separated spherical nanoparticles while aramide containing pyridine produced aggregated particles attributed to the molecular self assembly via H-bond directed organization of molecular precursors. The thermal behavior of all polymers exhibited two major thermal decompositions due to the subsequent breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Photoluminescence studies revealed that the blue emissions for the polyamide derived from benzidine were blue-shifted (shifted to a lower wavelength) compared to that of polyamides containing flexible linkages.ConclusionsWe report the synthesis of aromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups. The thermal behavior of all polymers exhibited two major decompositions due to breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Structure- photoluminescence correlation demonstrated an interesting connection between structural modification and optical properties. The blue emissions for the polyamide derived from benzidine, attributed to the highly conjugation system, was blue shifted with the introduction of flexible linkages. The prepared polymers dissolved in warm polar aprotic solvents. Further investigations to obtain films with reasonably good mechanical properties for different applications are in progress.

Synthesis of carbohydrate-containing polyamides and study of their properties☆

Abstract Carbohydrate-containing polyamides were prepared using low-temperature solution polycondensation of 2,3,4,5-tetra-O-acetylgalactaroyl dichloride (3) with various aromatic and aliphatic diamines viz. p- phenylenediamine ( 4 ) ; m-phenylenediamine; benzidine; 4,4′-diaminodiphenylmethane; 1,5-diaminoanthraquinone; 2,6-diaminoanthraquinone; 4,4′-diaminodicyclohexylmethane; hexamethylenediamine; and ethylenediamine (12). The four O-acetyl groups in 3 protect the hydroxyl functions and give good solubility as a result of increasing lipophilicity. The optimum conditions for the best yield and viscosity of the polyamide were determined by study of the factors affecting the polycondensation. These conditions for reaction of 3 with 4 were reached with reactant concentrations of 0.5 mol/l at −10°. On the other hand, the optimum conditions for reaction of 3 with 12 involved concentrations of 1.0 mol/l at 0°. Polyamides containing the unacetylated carbohydrate chains were obtained by de-O-acetylation of the synthesized acetylated carbohydrate-containing polyamides. Structures of the acetylated and de-O-acetylated carbohydrate-containing polyamides were confirmed by elemental analysis, i.r. and 1H-NMR spectroscopy. Their thermal degradations were studied by differential thermal analysis and thermogravimetric analysis.

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.

Selective cyclisation of 2,3,4,5-tetra-O-acetylgalactaric acid bis[alkylthio(thiocarbonyl)]hydrazides to saccharide 1,3,4-oxadiazole, thiadiazole, and thiadiazoline derivatives

The syntheses of galactaric acid acetate bis[alkylthio-(thiocarbonyl)]hydrazides (1,2) are described. Selective cyclisation of both hydrazide 1 and 2 was investigated. Using phosphorous oxychloride as a cyclising agent, loss of water produced 1,2,3,4-tetra-O-acetyl-1,4-bis(5-S-methyl or benzyl)-1,3,4-thiadiazol-2-yl)galacto-tetritol (3) or (4). Use of thionyl chloride lead to dehydrosulfurization and gave 1,2,3,4-tetra-O-acetyl-1,4-bis(5-S-methyl or benzyl)-1,3,4-oxadiazol-2-yl)galacto-tetritol (5) or (6). Finally, with triethyl orthoformate as the cyclising agent, compound 1 or 2 gave 3,3′-(2,3,4,5-tetra-O-acetylgalactar-1,6-dioyl)-bis-[(2-ethoxy-2,3-dihydro-5-S-methyl or benzyl)-1,3,4-thia-diazole] (7) or (8).

Syntheses and Investigation of Some New Polyarylates and Copolyarylates. Part I

Abstract By the interfacial condensation of acid chlorides I, II, and III, respectively, with bifunctional phenols (IV-X), soluble or mold-able thermostable polyarylates were obtained. Similarly, copolyarylates were prepared from a mixture of the acid chlorides I + II or I + III. With bisphenol-A (VIII), soluble polymers are usually obtained. Methylene dichloride and/or carbon tetra-chloride-water systems were the best media for interfacial condensations, and the polymers formed showed the highest reduced viscosity values. Polyester films are useful in many industrial applications because of their broad range of mechanical, optical, and electrical properties. The aromatic polyesters‐polyarylates-dominate the field of industrial polyester films [1]. Polyarylates prepared from dihydric phenols and purely aromatic dicarboxylic acid chlorides are highly heat resistant materials [2], but they are insoluble and nonmoldable [3]. However, by the introduction of ether linkages in the aromatic dicarboxylic acid moi...

Study of the thermal stabilities of some polymeric schiff-bases containing sulphur

Abstract The relationship of the thermal stabilities of some polymeric Schiff-bases to their chemical structures was studied by using thermogravimetric analysis and differential thermal analysis. Polymeric Schiff-bases were prepared by the condensation of 5,5′-methylene-bis-salicylaldehyde, terephthalaldehyde, di( p -formylphenyl) terephthalate or di( p -acetylphenyl) terephthalate with various diamines containing sulphur, such as thiocarbohydrazide, bis (4-aminophenyl) sulphone, 4,4′-diaminostilbene-2,2′-disulphonic acid and 3,5-diaminobenzene sulphonic acid. Two monomeric prototypes of these polymeric Schiff-bases were prepared in order to compare their thermal stabilities with the corresponding polymers.

Synthesis and characterization of carbohydrate-containing copolyhydrazides and copolyoxadiazoles

Abstract Carbohydrate-containing copolyhydrazides were synthesized by the reaction of 2,3,4,5-tetra-O-acetyl galactaroyl dichloride with typical dibasic aromatic and aliphatic acid dihydrazides, viz. terephthaloyl dihydrazide (4) succinoyl dihydrazide and oxalyldihydrazide (6), using low temperature solution polycondensation in N,N-dimethylacetamide. The maximum viscosity and yield of the copolyhydrazide derived from 4 were obtained for reactant concentration of 0.5 mol/l at −10°. The optimum conditions for the copolyhydrazide derived from 6 were obtained at reactant concentration of 1.0 mol/l at −5°. Copolyhydrazides containing unacetylated carbohydrate chains were obtained by de-O-acetylation of the acetylated polymers with methanolic ammonia. Copoly{1-[2-(2,3,4,5-tetra-O-acetyl-galacto-tetritoldi-1,4-yl)-5-(1,3,4-oxadizol-di-2,5-yl)]-4-[2-(1,3,4- oxadiazol-di-2,5-yl)-benzene]} was prepared by dehydrative cyclization of the corresponding copolyhydrazide using thionyl chloride. Structures of the synthesized polymers were confirmed by elemental analysis, i.r., and 1H-NMR. Thermal degradations of these polymers were studied by differential thermal analysis and thermogravimetric analysis.

Synthesis of New Thermally Stable Halopolyamides

Abstract Several new thermally stable halopolyamides were prepared by low temperature solution polycondensation from some new diacid chlorides and a number of diamines, namely p-phenylenediamine (I), m-phenylenediamine (II), benzidine (III), 4,4′-diamino-diphenylmethane (IV), 4,4′-diaminodiphenyl sulfone (V), ethylene-diamine (VI), hexamethylenediamine (VII), and 4,4′-diamino-dicyclohexylmethane (VIII). The diacid chlorides were derived from two series of some new dicarboxylic acids: (A) 2-halo-(chloro-, bromo-, and iodo-)-4-carboxyphenoxyacetic acid (K-XI); and (B) 2-halo-(chloro- and iodo-)hydroquinone-l,4-diacetic acid (XII and XIII). Dimethyl esters and diamide derivatives were prepared to confirm the structures of the diacid chlorides (Ka-XIIIa)i Nylon salts of the new dicarboxylic acids (DC-XIII) were also prepared. Some of the factors affecting the reduced viscosity of the polymers such as the effect of the concentration of initial components, temperature, and duration time were studied. In the cas...

Synthesis and Properties of Some Schiff-Base Polymers Containing Sulfur

Abstract Condensation of 5,5′-methylene-bis-salicylaldehyde with thiocarbohydrazide, bis(4-aminophenyl) sulfone, 4,4′-diaminostilbene-2,2′-disulfonic acid or 3,5-diaminobenzenesulfonic acid gave the corresponding polymeric schiff-bases (1, 2, 3, or 4). Also, condensation of terephthalaldehyde with thiocarbohydrazide or bis(4-aminophenyl) sulfone produced the schiff base polymers (5 or 6). Finally, condensation of di(p-formylphenyl) terephthalate or di(p-acetylphenyl) terephthalate produced the polymers (7, 8). Structures of these polymers (1 − 8), their properties, viscosities measurements and the effect of various reaction conditions on the yield percent are studied. These variable conditions showed no effect on the molecular weight of the present schiff polymers.

Synthesis and Characterization of Thermally Stable Ring-Shaped Nanosized Aramides Containing Pendant Substituted Arylamide: Structure-Properties Correlation

The introduction of fluorescent moieties in the polymeric chain permits the preparation of luminescent materials with potential applications. In this report, a number of aromatic nanosized polyamides containing both pendant acetoxynaphthamide and acetoxybenzamide were synthesized and characterized. The nanosized polymers were obtained as well-separated spherical and/or ring-shaped forms based on the pendent structure and the average diameter was 130 nm. Structure-properties correlations based on changing either the diamine and/or the pendent group demonstrated interesting connections. The polymers exhibited two major thermal decompositions attributed to the breakage of the main amide chain and the residual diacid-containing pendant moieties, respectively. Noteworthy, no significant change in the absorption spectra was noticed on phenylene / pyridine unit interchange.