Regular copolyamides. IV. Characterization of membrane morphology

Asymmetric copolyoxamide films prepared via a solution-casting/gelation process have been characterized by scanning electron microscopy, small-angle light scattering, and measurements of surface area and hydrophilicity. The polymer selected for study is a regular copolyamide prepared from N,N-bis(2-aminoethyl) oxamide and isophthaloyl chloride, and shows promise as a membrane material for desalination by reverse osmosis. Scanning electron microscopy reveals a unique capillary structure in films cast from N,N-dimethylacetamide-LiCl mixtures, plus a variety of structures in trifluoroacetic acid-cast membranes. Light-scattering experiments on water-swollen films have substantiated microscopic observations of desiccated samples; the gel structures of the copolyoxamide films do not appear to suffer severe collapse on dehydration. Measurements of surface area and water sorption have been conducted in an attempt to assess membrane-water interaction.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.     

A facile and general method for the preparation of diaryltellurium dicarboxylates

Diaryltellurium dicarboxylates can be prepared by treatment of the corresponding dichlorides with carboxylic acids in the presence of silver oxide. The conversion of the dichlorides to the carboxylates can also be achieved through a more practical method employing a carboxylate anionic exchange resin. IR and PMR data are given.     

A facile and convenient method for the preparation of macrocyclic diamides

A number of macrocyclic diamides have been synthesized from the reaction of a diacid dicarboxylic dichloride with primary diamino compound in the presence of magnesium oxide-silica gel at room temperature in good yields. Using urea and thiourea as well as diamines to produce the corresponding macrocycles in the range of 52–56% yields are also included in this paper. One of the major advantages of this method is simple regeneration of inorganic solid and its reuse through several cycles without a decrease in activity.     

A facile method for the preparation of bishomopropargylic alcohols from acyl chlorides

Controlled dilithiation of propargyl bromide with two equivalents of n-butyllithium, in the presence of TMEDA, produces the operational equivalent of the dianion 1,3-dilithiopropyne. The latter reacts efficiently with acid chlorides to produce bishomopropargylic alcohols in a single step route and with high regioselectivity and moderate yields.     

Regular copolyamides. II. Preparation and characterization of regular aliphatic copolyoxamides

Regular copolyoxamides were prepared from diamine-oxamides and aliphatic diacid chlorides by interfacial and solution polymerization. Interfacial polymerization is preferred with diamineoxamides where the diamine portion has two to six methylene groups and the diamine-oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine-oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine-oxamides with more than six methylene groups in the diamine portion of the molecule are better prepared by solution polymerization in dimethyl acetamide. Regular aliphatic oxamides are soluble in trifluoroacetic acid and hexafluoroisopropanol and show a considerable alternation of the melting point behavior in the diamine portion of the polyamides with up to five methylene groups. Copolyoxamides with two and four methylene groups melt higher than the copolyoxamides with three and five methylene groups. Aliphatic copolyoxamides/adipamides melt at approximately 260°C and show a steady decrease in melting points to about 220°C for polyoxamides with twelve methylene groups.     

Simple and facile method for the preparation of vinyl azides

A synthetic utility of [bis(trifluoroacetoxy)iodo]benzene on α,β-unsaturated carboxylic acid is described. This is the first example of preparation of vinyl azide using α,β-unsaturated carboxylic acids directly by using hypervalent iodine reagent. The advantage of this protocol is characterized with non-toxicity of starting material and shorter reaction times to obtain good preparative yields. The method is also useful for the preparation of acyl azides.     

The use of 2-0xazolidinone as a latent aziridine equivalent. I. A facile method for the preparation of 2-substituted oxazolines

Ring-opening reaction of 2-oxazolidinone with acid chlorides followed by treatment with aqueous sodium hydroxide yields 2-substituted oxazolines.     

A facile method for the preparation of thermally remendable cross‐linked polyphosphazenes

Novel cross‐linked polyphosphazenes with remendable capacity have been synthesized through the Diels‐Alder reactions. Their structure and properties were characterized by NMR, FT‐IR, GPC, DSC, TGA SEM, and polarizing microscope. The process of Diels‐Alder reaction (D‐A reaction) and retro‐Diels‐Alder reaction (retro‐D‐A reaction) have been investigated by FT‐IR, UV, and DSC. The cross‐linked polyphosphazenes exhibited remendable capability only need a thermal treatment when they were cut by blade, any other treatments such as additional monomer or catalyst, surface treatment or pressure were not needed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

A facile spectrophotometric method for the determination of selenium.

A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of selenium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine, which oxidizes Variamine Blue to form a violet-colored species having an absorption maximum at 546 nm. Beer's law is obeyed in the range 2-20 g of selenium in a final volume of 10 ml. The molar absorptivity and Sandell's sensitivity were found to be 2.6 x 10(4) l mol-1 cm-1 and 0.003 microgram cm-2, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of selenium in real samples of water, soil, plant materials, human hair, and synthetic samples of cosmetics and pharmaceutical preparations.     

无水稀土氯化物的新制备方法: 从稀土氧化物出发制备无水稀土氯化物

本文报道从稀土金属氧化出发, 在THF中与TMSCl/CH3OH反应, 制备无水稀土氯化物LnCl3.nTHF的方法。此法具有产物纯度高, 产率好, 制备条件温和, 操作方便等优点, 因而具有一定的实用性。     

A facile method for the preparation of monodisperse hollow silica spheres with controlled shell thickness

This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010     

Novel and facile method for the preparation of monodispersed titania hollow spheres

The fabrication of monodispersed hollow spheres in varying sizes and shapes is very interesting and has a lot of potential applications. This paper provides a very simple route to preparing hollow titania spheres using polystyrene (PS) as a template. In this approach, the titania shells were first formed and the PS cores were dissolved subsequently, even synchronously, in the same medium; neither an additional dissolution nor a calcination process was needed to remove the PS cores. Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Barret-Emmet-Teller measurements were used to characterize the monodispersed hollow titania spheres. A possible formation mechanism of the hollow spheres was proposed.     

A facile preparation of vinyl sulfides

Vinyl sulfides are formed in high yield by the alkylation of trimethylsiloxy mercaptides.     

A facile preparation of imidazolinium chlorides

A process for the preparation of symmetric and unsymmetric imidazolinium chlorides that involves reaction of a formamidine with dichloroethane and a base (a) is described. This method makes it possible to obtain numerous imidazolinium chlorides under solvent-free reaction conditions and in excellent yields with purification by simple filtration. Alternatively, symmetric imidazolinium chlorides can be prepared directly in moderate yields from substituted anilines by utilizing half of the formamidine intermediate as sacrificial base (b).     

A facile preparation of 2,6-diarylpyrazines

2,6-Diarylpyrazines were prepared in good yields by a novel method of condensing methoxycarbonylhydrazine with N,N-bis(arylcarbonylmethyl)-p-toluenesulfonamides, unsymmetrical derivatives of which were synthesized by a new (or different) procedure. The structures of these 2,6-diarylpyrazines were established by spectral data and X-ray diffraction analysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:341–345, 1998     

A facile method for the preparation of hexafluoroisopropanol functionalized derivatives using hexafluoroacetone trihydrate via a carbonyl-ene reaction

Hexafluoroacetone trihydrate was shown to undergo an efficient carbonyl-ene reaction with a variety of alkenes in the presence of molecular sieves under microwave heating and conventional heating producing hexafluoroisopropanol functionalized derivatives in high yields.     

A facile method for the preparation of α-methylene-γ-butyrolactones from tulip tissues by enzyme-mediated conversion

We developed a facile method of enzyme-mediated conversion of 6-tuliposide to α-methylene-γ-butyrolactone (tulipalin). We used a tuliposide-converting enzyme for the conversion of 6-tuliposides extracted from tulip tissues into the corresponding tulipalins in high yields within 2 h at pH 7.0. The resulting tulipalins were selectively extracted by using several organic solvents.     

Structure-property relationships of copolyamides. I. Thermal properties and crystallization

Six nylon salts [hexamethylenediammonium adipate (6.6), hexamethylenediammonium terephthalate (6.T), hexamethylenediammonium isophthalate (6.I), p-xylylenediammonium adipate (PXD.6), m-xylylenediammonium adipate (MXD.6), and m-xylylenediammonium isophthalate (MXD.I)] were copolymerized with ε-caprolactam. The resulting random copolyamides showed different modes of crystallization as confirmed by the melting temperature depression and the decrease in the isothermal crystallization rate. By selective hydrolysis it was found that the differences in T_m depression and isothermal crystallization rate were due to partial inclusion of comonomers in the crystal lattice. The effect of comonomer structure on the crystallization rate is also discussed.