Chlorine-resistant membrane for reverse osmosis. I. Correlation between chemical structures and chlorine resistance of polyamides

Correlation between the chemical structure of polyamides and the reactivity to hypochlorous acid was investigated to evaluate their chlorine resistance as a membrane material for reverse osmosis. Modes of interaction of polyamides with hypochlorous acid were classified into three; no reaction, reversible chlorination at the amide nitrogen, and irreversible chlorination at the aromatic nucleus. These modes of interaction were dependent upon the amine component of polyamide. Secondary amines such as piperazine and N-methylaniline gave amides which were quite stable against hypochlorous acid. Thus, poly(isophthaloyl piperazine) was most stable among the polyamides investigated in this study. Polyamide derived from aliphatic primary diamines such as polyethyleneisophthalamide gave an N-chlorinated amide, which could be reversibly dechlorinated by the treatment with a reducing agent such as sodium hydrosulfite. Polyamides comprised of aromatic primary diamines such as poly(m-phenyle-neisophthalamide), on the other hand, gave a product with chlorinated m-phenylene nucleus which could not be dechlorinated by a reducing agent.     

Oxyethylated secondary amides as soil wetting agents

Polydisperse adducts, RCONR’ (CH₂CH₂O)_xH, with attractive wetting properties were prepared by oxyethylating aliphatic and aromatic secondary amides to calculated x values of 5 to 20. Moderate wetting profiles were observed with adducts where R and R’ contained 15 to 18 carbon atoms and had short ethylene oxide chains. These products, however, contained unreacted amide and/or ester contaminants. Consequently, the products showed high water solubility, fairly flat surface tension curves and average wetting ability. In the transition of adducts derived from aliphatic amides to those from aromatic amides, unreacted amide concentration decreased and ester contaminant increased.     

Preparation and properties of three novel poly(phosphazene‐aryl amide)s containing cyclotriphosphazene structures

1,1,3,5‐tetraphenoxy‐3,5‐bis(4‐aminoanilino)cyclotriphosphazene, 1,1,3,5‐tetraphenoxy‐3,5‐bis[4‐(4‐aminophenysulfone)anilino)]cyclotriphosphazene, and 1,1,3,5‐tetraphenoxy‐3,5‐bis(N,N′‐ethanediamine)cyclotriphosphazene were synthesized in two steps from the p‐Phenylenediamine, 4,4′‐diaminodiphenylsulfone, and ethylenediamine via nucleophilic substitution and catalytic reduction with hexachlorocyclotriphosphazene. Three novel aromatic polyamides such as poly(cyclotriphosphazene‐p‐phenylene amide), poly(cyclotriphosphazene‐p‐sulfuryl amide), and poly(cyclotriphosphazene‐ethyl amide) were synthesized from these diamines by direct polycondensation reaction with terephthaloyl chloride and pyridine in N‐methyl pyrrolidone, respectively. The chemical structures of the diamine monomers and three novel poly(cyclotriphosphazene‐aryl amide)s were characterized by Fourier Transform Infrared, (¹H and ³¹P) Nuclear Magnetic Resonance, and Elemental Analysis. The thermal properties of the polyamides were determined by Differential Scanning Calorimetry and Thermogravimetric Analysis (TGA). The crystallization behaviors of the polyamides were studied by Wide‐ray X‐ray diffraction, and the morphology of the pyrolysis residues were observed by Scanning Electron Microscope. The three poly(cyclotriphosphazene‐aryl amide)s with amorphous structure would exhibit an enhanced solubility in polar aprotic solvents and a superior thermal stability with initial decomposition temperature being at about 198–259°C. TGA curves of the poly(cyclotriphosphazene‐aryl amide)s exhibit mainly three thermal decomposition steps, and the poly(cyclotriphosphazene‐p‐phenylene amide) presents the highest solid residue rate 62.6% heated to 600°C. In the morphology analysis of the poly(cyclotriphosphazene‐aryl amide) solid residues, organophosphorus gelatum forms in the surface layer were observed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyaddition of o- and p-phenylenedioxydiacetic acids to diisocyanates

o- and p-Phenylenedioxydiacetic acid (o-, p-PhDDA) undergo in presence of 1,6-hexamethylene (HMDI)-,2,4-toluylene (TDI)-,4,4′-dibenzyl (DBDI)- and 1,5-naphthylene (NDI)-diisocyanates polyaddition reactions. These reactions being accompanied by CO₂ evolution finally give polyamides. These syntheses were carried out based on preliminary studies regarding the reactivity of o- and p-PhDDA with aromatic isocyanates. When o- and p-PhDDA acids react with aromatic isocyanates N,N′.-disubstituted diamides are formed. Both reaction partners show bands in their IR-spectra characteristic to V_CO and V_NH. The intrinsic viscosities of some polymers were measured and thermogravimetric curves were obtained.     

Oxidative degradation of polyamide reverse osmosis membranes: Studies of molecular model compounds and selected membranes

Selected aromatic amides were used to model the chemical reactivity of aromatic polyamides found in thin‐film composite reverse osmosis (RO) membranes. Chlorination and possible amide bond cleavage of aromatic amides upon exposure to aqueous chlorine, which can lead to membrane failure, were investigated. Correlations are made of the available chlorine concentration, pH, and exposure time with chemical changes in the model compounds. From the observed reactivity trends, insights are obtained into the mechanism of RO membrane performance loss upon chlorine exposure. Two chemical pathways for degradation are shown, one at constant pH and another that is pH‐history dependent. An alternative strategy is presented for the design of chlorine‐resistant RO membranes, and an initial performance study of RO membranes incorporating this strategy is reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1173–1184, 2003     

Poly(aryl ether amides): Self polymerization of an A-B monomer via amide-activated ether synthesis

Summary A synthetic approach for the preparation of poly(aryl ether amides) has been developed where the generation of an aryl ether linkage was the polymer-forming reaction. The amide moiety was found to be sufficiently electron withdrawing to activate halosubstituents, towards nucleophilic aromatic substitution polymerizations, analogous to conventional activating groups (i.e, sulfone, ketone etc.). Several new A-B monomers, 4-fluoro-N-(4-hydroxyphenyl)benzamide, 1, and 4-fluoro-N-(3-hydroxyphenyl)benzamide, 2, which contain both an amide-activated fluoro group and a phenol group were prepared and their self polymerization studied. Compounds 1 and 2 were prepared by the condensation of 4-fluorobenzoyl chloride with either 4-or 3-aminophenol, respectively. The polymerizations were carried out in an N-methyl-2-pyrrolidone (NMP)/N-cyclohexyl-2-pyrrolidone (CHP) solvent mixture in the presence of potassium carbonate. Several new high molecular weight poly(aryl ethers) were prepared by this route with Tg's in the 225 °C range.     

Rhodium(I)‐Catalyzed Arylation of β‐Chloro Ketones and Related Derivatives through Domino Dehydrochlorination/ Conjugate Addition

Highly efficient arylations of β‐chloro ketones and their ester and amide derivatives were achieved by means of domino dehydrochlorination/Rh(I)‐catalyzed conjugate addition. In situ generated vinyl ketones and their analogues were identified as the reaction intermediates. The present synthetic protocol provides a concise route to (chiral) β‐aryl ketones, esters, and amides.     

Synthesis and Properties of Noncoplanar Rigid-rod Aromatic Polyamides Containing Phenyl or Naphthyl Substituents

A series of novel aromatic polyamides having noncoplanar biphenylene units in the main chain and bulky naphthyl or phenyl pendant group at 2,2′-disubstituted position were prepared from the two rigid-rod aromatic dicarboxylic acid monomers, 2,2′-diphenylbiphenyl-4,4′-dicarboxylic acid (1) and 2,2′-dinaphthylbiphenyl-4,4′-dicarboxylic acid (2), and various aromatic diamines. These polyamides were readily soluble in many organic solvents and showed excellent thermal stability associated with high glass-transition temperatures in the range of 229–292°C. These polymers also exhibited strong UV–Vis absorption bands at 262–353 nm in NMP solution, and their photoluminescence spectra showed maximum bands at 440–462 nm in the purple to blue region. The poly(amine–amide) IId derived from the diamine with triphenylamine moieties revealed excellent electrochromic contrast and coloration efficiency, changing color from the pale yellowish neutral form to green then to the blue oxidized forms when scanning potentials positively from 0.00 to 1.30 V. Figure Graphical Abstract. A series of novel aromatic polyamides having noncoplanar biphenylene units in the main chain and bulky naphthyl or phenyl pendant group at 2,2′-disubstituted position were prepared from the two dicarboxylic acids and various aromatic diamines. These polyamides were readily soluble in many organic solvents and showed excellent thermal stability associated with high glass-transition temperatures in the range of 229–292°C. These polymers also exhibited strong UV–Vis absorption bands at 262–353 nm in NMP solution, and their photoluminescence spectra showed maximum bands at 440–462 nm in the purple to blue region. The poly(amine–amide) IId derived from the diamine with triphenylamine moieties revealed excellent electrochromic contrast and coloration efficiency, changing color from the pale yellowish neutral form to green then to the blue oxidized forms when scanning potentials positively from 0.00 to 1.30 V.     

Synthesis of comb-like graft copolyamides with rigid aromatic main-chains and long flexible side-chains

Summary In this paper we report a novel method of preparing polyamide molecular composites (1) by synthesizing graft-copolymes with stiff aromatic polyamide main-chains and flexible high molecular weight (high-M) polyamides as the side chains. The unique feature of the present graft-copolyamides is that the side-chains are connected directly to the aromatic rings in the stiff polyamide chains through amide groups, and are not connected to the amide groups present in the stiff main-chains.     

A Rapid Synthesis of Fatty Acyl Urea Derivatives

Fat-based aliphatic amides react with aromatic isocyanates in refluxing xylene generally within 1 hr to form crystalline acylaryl urea compounds in 50-80% yields. The reaction appears to be general with either component being aliphatic or aromatic. Although the reaction occurs in various solvents, xylene is the preferred solvent in which the reactions were completed within 4 hr for the chosen amides and isocyanates. The progress of the reaction was conveniently monitored by infrared through the disappearance of the intense isocyanate band at 2258 cm⁻¹. Agricultural Research Service, USDA.     

Tallow alkanolamides: Preparation and effect on surfactant solutions

Oxyalkylation of N-(2-hydroxyethyl) amides and N,N-bis-(2-hydroxyethyl) amides gave products which were valuable as detergent additives and detergent intermediates. Oxyalkylation of simple amides was difficult to carry out, and the product contained large quantities of unreacted amide which had an adverse effect on surfactant properties. Amides with short oxyalkyl chains and long fatty chains were not soluble by themselves but were solubilized by aqueous detergent solutions and had characteristic “Krafft Points.” This temperature, at which the mixed solution became clear, was independent of detergent used, amide to detergent ratio up to 1.4, total concentration, and water hardness. Krafft point of poorly soluble detergents such as sodium octadecyl sulfate and disodium α-sulfostearate was lowered by mixing with alkanolamides. N,N-Bis-(hydroxyethyl)-hexadecanamide and the oxyalkylated products of N,N-bis-(hydroxyethyl) hexadecanamide and N,N-bis-(hydroxyethyl) octadecanamide increased the viscosity of solutions of linear alkylbenzene sulfonate and sodium dodecyl sulfate in the same was as the N,N-bis-(hydroxyethyl) amide prepared from coconut oil. Foam stabilizing properties ere observed for some of oxyethylated amides. One per cent N,N-bis-(2-hydroxyethyl) oleamide and 2-(2-hydroxyethoxy)-ethyloleamide formed petrolatum-water emulsions which were stable for more than a month. Presented at the AOCS Meeting, Houston, May, 1971. Deceased. E. Market. Nutr. Res. Div., ARS, USDA.     

Synthesis and characterization of novel aromatic polyamides derived from 2,2′‐bis(p‐phenoxyphenyl)‐4, 4′‐diaminodiphenyl ether

BACKGROUND: Wholly aromatic polyamides (aramids) are high‐performance polymeric materials with outstanding heat resistance and excellent chemical stabilities due to chain stiffness and intermolecular hydrogen bonding of amide groups. Synthesis of structurally well‐designed monomers is an effective strategy to prepare modified forms of these aramids to overcome lack of organo‐solubility and processability limitations. RESULTS: A novel class of wholly aromatic polyamides was prepared from a new diamine, namely 2,2′‐bis(p‐phenoxyphenyl)‐4,4′‐diaminodiphenyl ether (PPAPE), and two simple aromatic dicarboxylic acids. Two reference polyamides were also prepared by reacting 4,4′‐diaminodiphenyl ether with the same comonomers under similar conditions. M?_w and M?_n of the resultant polymers were 8.0 × 10⁴ and 5.5 × 10⁴ g mol^?1, respectively. Polymers resulting from PPAPE exhibited a nearly amorphous nature. These polyamides exhibited excellent organo‐solubility in a variety of polar solvents and possessed glass transition temperatures up to 200 °C. The 10% weight loss temperatures of these polymers were found to be up to 500 °C under a nitrogen atmosphere. The polymers obtained from PPAPE could be cast into transparent and flexible films from N,N‐dimethylacetamide solution. CONCLUSION: The results obtained show that the new PPAPE diamine can be considered as a good monomer to enhance the processability of its resultant aromatic polyamides while maintaining their high thermal stability. The observed characteristics of the polyamides obtained make them promising high‐performance polymeric materials. Copyright © 2009 Society of Chemical Industry     

REVIEW ARTICLE LONG CHAIN DISUBSTITUTED ALIPHATIC AMIDES AS EXTRACTING AGENTS IN INDUSTRIAL APPLICATIONS OF SOLVENT EXTRACTION

In comparison with tri-n-butyl phosphate (TBP), N,N'dialkyl aliphatic amides present some potential advantages as extracting agents of actinides in the reprocessing of Irradiated nuclear fuels. One of the more evident of these advantages is the benign nature of amide degradation products; solvent treatment is thus simplified, and higher irradiation doses can be tolerated- A second advantage over TBP is the greater selectivity of dialkyl amides for several important fission products thus providing higher decontamination of uranium and plutonium products. On the other hand, the tendency of amides to form slightly soluble adducts with uranium in nitric acid media restricts the number of amides suitable for practical applications. N,N'dialkyl amides may also present some interest in hydrometallurgical applications in non-nuclear fields. A review of our own research with these compounds Integrated with results obtained by other authors in previous papers is presented here.     

Preparation and surface active properties of terminal amide type of alcohol ethoxylates

Three kinds of title amide compounds with different terminal structures (N-unsubstituted amide, N,N-dimethylamide and acylmorpholine) were prepared from alkyl tetra(oxyethylene) monoethers (alkyl: decyl or dodecyl). The cloud points of the N,N-dimethylamides and acylmorpholines were higher than the other corresponding alcohol ethoxylate derivatives previously developed by us, and all these amides inclusive of N-unsubstituted amides had sufficient hydrophilicity. Surface active properties (CMC, γ_CMC and foaming properties) of these amides in pure water and in hard water (1000 ppm of total hardness as CaCO₃) were almost the same and considered excellent as nonionic surfactants. Furthermore, they showed good lime-soap dispersing ability.     

Monomeric N-hydroxyethylated amides

Oxyethylated amides that are good wetting agents have been prepared as mixtures by allowing amides to react with ethylene oxide under base catalysis. Individual components of such mixtures can be synthesized by allowing 1-alkylaziridines to react with p-toluenesulfonic acid in monomethylethers of di-, tri- and tetraethylene glycol used as solvents. The aminoethers are then acylated, and the methylether group is removed with trimethylsilyliodide from the resulting amide ethers. The sequence should allow the synthesis of specific wetting agents of quite varied structure (alkyl, aryl groups) with an option for isotopic labeling for more detailed analysis of the wetting properties.     

Self‐healing imidazolium‐based ionene‐polyamide membranes: an experimental study on physical and gas transport properties

A new series of six imidazolium‐based ionenes containing aromatic amide linkages has been developed. These ionene‐polyamides are all constitutional isomers varying in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) along the polymer backbone. The physical properties as well as the gas separation behaviors of the corresponding membranes have been extensively studied. These ionene‐polyamide membranes show excellent thermal and mechanical stabilities, together with self‐healing and shape memory characteristics. Most importantly, [TC‐API(p)‐Xy][Tf₂N] and [IC‐API(m)‐Xy][Tf₂N] membranes (TC, terephthaloyl chloride; API, 1‐(3‐aminopropyl)imidazole; Xy, xylyl; Tf₂N, bis(trifluoromethylsulfonyl) imide; IC, isophthaloyl chloride), where the amide and xylyl linkages are attached at para and meta positions, exhibit superior selectivity for CO₂/CH₄ and CO₂/N₂ gas pairs. We also demonstrate the transport properties and diverse applicability of our newly developed ionene‐polyamides, particularly [TC‐API(p)‐Xy][Tf₂N], for various industrial applications. © 2019 Society of Chemical Industry     

醛与胺均相催化合成三级酰胺研究进展

酰胺类化合物是材料科学、化学生物学及药物化学中重要的有机化合物。醛容易得到且毒性较小,出于原子经济性考虑是合成酰胺的合适原料。近年来,随着绿色化学的兴起,利用醛作为酰化试剂,通过C—H键活化方式合成酰胺键的方法得到广泛关注。研究方法中,有机小分子、过渡金属、稀土盐或配合物的催化起到重要作用,纳米催化剂的催化在酰胺键形成方法的研究也有突破。纳米粒子应用于醛与胺合成三级酰胺的反应有金属胶体纳米催化剂(准均相型)和磁性非均相型。非均相催化剂的优势在于其较高的回收使用率,易与产物分离,便于回收再利用。磁性纳米材料与以往的均相催化剂相比,分离和回收更加简单方便,重复利用率更高,但催化剂表征受到限制。探索制备方法简单、操作步骤方便和催化效果显著的普通多相纳米催化剂是未来应用于催化醛合成酰胺的新领域。综述近年来利用醛作为酰化试剂,通过C—H键活化的方式,与铵盐、二级胺、三级胺和酰胺反应合成三级酰胺化合物的方法,并总结相关反应机理。     

Novel chalcone-based aromatic polyamides: synthesis,characterization, and properties

Two novel diacid-based monomers have been synthesized by anchoring a benzylideneacetophenone (chalcone) moiety through an amide or ester bridge at the fifth position of the isophthalic acid ring. Two series of new polyamides bearing chalcone side chains were prepared by direct polycondensation reaction of the aforementioned dicarboxylic acids and various aromatic diamines in N-methyl-2-pyrrolidinone, using triphenyl phosphite and pyridine as condensing agents. Their molecular structure and the basic properties were investigated by nuclear magnetic resonance, Fourier-transform IR and UV–vis spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray diffraction. The inherent viscosity, molecular weights measurements (by gel permeation chromatography), water uptake, and solubility tests completed the research study. Introduction of the rigid and bulky chalcone units into the polymer side chains improved remarkably the solubility of the aromatic polyamides, endowed them with an amorphous nature, good thermal stability, and photosensitivity. The resulting polymers were obtained in good yields, inherent viscosities varied between 0.49 and 0.86 dL/g, and their relative high molecular weights conferred them film-forming properties. They were soluble in amide-type polar solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. These polyamides had glass transition temperatures between 219 and 264 °C, and 10% weight loss temperatures in the range of 394–436 °C and around 50% residue at 700 °C in nitrogen atmosphere. The polyamides underwent a [2 + 2] photocycloaddition reaction upon UV light irradiation both in solution and film state in the absence of a photoinitiator or photosensitizer. The polymer films became insoluble in solvents as a result of the crosslinking .     

New strategies for the Hofmann reaction

Some new strategies, such as the use of hydrotropes, surfactants, co-solvent, etc., were applied to the Hofmann reaction of fatty amides to obtain isocyanates, amines and carbamates. Additionally, some industrially important aromatic amines were synthesised.     

Polyamides containing quinoxaline moiety

A new quinoxaline moiety containing aromatic diamine; 2,3-bis[4-(4-aminophenoxy)phenyl]quinoxaline (APQ) was synthesized starting from 4-methoxybenzaldehyde and was characterized by IR, ¹H, ¹³C NMR and Mass spectrometry. Five new polyamides were synthesized by polycondensation of various aliphatic diacid / aromatic diacids namely, azelaic acid, bis(4-carboxyphenyl)dimethylsilane, 4,4′-oxybis(benzoicacid), isophthalic acid and terephthalic acid with APQ by Yamazaki’s phosphorylation method using triphenyl phosphite as condensing agent. The polyamides were characterized by IR spectroscopy, solubility tests, inherent viscosity, X-ray diffraction technique, differential scanning colorimetry and thermogravimetric analysis. The polyamides had inherent viscosities in the range 0.39–0.45 dL/g in N, N-dimethylacetamide at 30?±?0.1?°C. The polyamides were soluble in polar aprotic solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone. X-Ray diffraction studies showed that polyamides were amorphous in nature. The polyamides showed glass transition temperatures in the range 104–205?°C, according to differential scanning calorimetry. Thermogravimetric analysis exhibited initial decomposition temperatures above 348?°C; indicating that these polyamides possessed excellent thermal stability.