Effect of an anionic surfactant on the complexation of some nonionic polymers with iodine in aqueous media

Complexation of some water soluble nonionic polymers, namely, polyvinylalcohol (PVA), polyvinylpyrrolidone (PVP), and hydroxypropyl cellulose (HPC), with iodine has been studied in aqueous and aqueous sodiumdodecylsulfate (SDS) solution. While the complexation was indicated by a red shift of the tri-iodide band in case of PVP or HPC, the PVA-iodine complex showed its characteristic band around 500 nm. It was observed for the first time that presence of SDS led to complete break down of the PVA-iodine complex and its characteristic blue color. The presence of monomers of SDS, however, appeared to favor the formation of the iodine complex with PVP or HPC. Addition of n-propanol, which is known to prevent the formation of gels or microgels in polymer solutions, was found to enhance the polymer-iodine complex. Gels of pure HPC and HPC with iodine both in presence and absence of SDS have been prepared and studied.     

Adsorption kinetics measurements of some nonionic surfactants

Dynamic surface tension values of aqueous surfactant solutions were measured by using the ring and plate method. The mean diffusion coefficients calculated on the basis of the purely diffusion controlled adsorption model vary between 2 · 10^–6 to 7 · 10^–6 cm²/s for all surfactants studied:n-alkanols,n-alkanoic acids, dimethyl and diethyln-alkyl phosphine oxides. That means the surfactants investigated adsorb with a purely diffusion controlled adsorption mechanism and no barriers excist to hinder sorption processes.Nomenclature c ₀ surfactant bulk concentration - D diffusion coefficient - surface concentration - ₀ equilibrium surface concentration - ¯ (t)/ ₀ reduced surface concentration - maximum surface concentration - K ₀/c₀ - surface tension - t time - Dt/K ² reduced time - a _L coefficient of the Langmuir isotherm     

Multimodal sorption of nonionic dyes with two amino groups by various polymers from water

Sorption isotherms of nonionic dyes with two amino groups (one anthraquinone dye and two azo dyes) on various polymers from water were measured at 40–90°C (Nylon-6 and cellulose film) and at 95°C (polyester microfiber). The isotherms were curved, convex to upward, in the range of low dye concentration C_s in water and almost linear in the range of medium to saturated C_s. The isotherms measured at low temperature (40°C for cellulose, 40–60°C for Nylon-6, and at 95°C for polyester) were satisfactorily described by considering three concurrent modes of sorption. They are Nernst type partitioning and bimodal Langmuir sorption (sorption by the higher affinity sites with a small saturation value and that by the lower affinity sites with a large saturation value). However, for the sorption of the anthraquinone dye and one azo dye by Nylon-6 film at high temperature (80–90°C), the amount of dye sorbed by the high affinity site decreased to negligibly small. Accordingly, the isotherms were expressed well by simple dual-sorption model. © 1995 John Wiley & Sons, Inc.     

Intermacromolecular interactions involving linear and network polyacids and nonionic polymers

Interactions between linear and network polymers are studied in the case when one component is a polyacid and the other component is an uncharged polymer. It is shown that, under different reaction conditions, swelling or contraction of the polymer network can be observed for the same pair of reagents. It is found that, during consideration of the formation of an interpolymer complex between network and linear polymers, a distinction should be made between a semi-interpenetrating network and a hydrogel with a modified surface. The latter forms under conditions when the linear polymer practically does not penetrate the network and the complexation occurs predominantly on the sample surface.     

Extraction-spectrophotometric determination of tungsten with thiocyanate and some amidines

The procedure is based on reduction of W(VI) to W(V) by tin(II) chloride in 6 M hydrochloric acid, and extraction of the resultant thiocyanate complexes with a benzene solution of amidine. The complex coagulates and is dissolved in the benzene by addition of 1-pentanol. The maximum molar absorptivities of the complexes with 8 amidines in benzene/1-pentanol (9:1, v/v) are in the range 12 100–18 400 mol^?1 cm^?1. The simplest compound, N,N-diphenylbenzamidine gives the best sensitivity; the linear range covers 5–90 μg W in 10 ml of final solution; the detection limit is 2 ng W ml^?1. The method is applied to alloy steels.     

Aqueous biphasic systems formed by nonionic polymers I. Effects of inorganic salts on phase separation

The effect of salts KSCN, KI, KBr, KCl, KClO₄, KF, K₂SO₄ and NH₄Cl, LiCl, NaCl, KCl, CsCl on the binodials of the phase diagrams for aqueous biphasic dextranpolyvinylpyrrolidone, dextran-polyvinyl alcohol, dextran-ficoll and dextran-polyethylene glycol systems was studied. It is established that the K-salts present at the concentrations of 0.1 and 0.5 mol/kg alter the binodials of the phase diagrams for the above systems. The effect of a salt is found to be related to the lyotropy of the salt quantified by the salt molal surface tension increment. It is assumed that phase separation in an aqueous polymer biphasic system is affected by the presence of a salt mainly due to the effect of the salt on the structure and/or state of water in the system.     

Sorption and permeation behaviour of metal thiocyanate complexes on cellulose acetate polymers

Various metal thiocyanate complexes in aqueous solution were sorbed on solid cellulose acetate polymers. The sorption selectivity increased in the order Zn(2+) > Fe(3+) > Cu(2+) > Co(2+) > Ni(2+). The sorption behaviour followed a Langmuir-type adsorption isotherm, and the maximum adsorption capacity was 6.1 x 10(-5) mole of complex per g of polymer under optimum conditions. The zinc species sorbed appear to be NH(4)Zn(H(2)O)(SCN)(3) or (NH(4))(2)Zn(SCN)(4) according to analysis of the sorption equilibrium. The ion-association species formed by the complex zinc anion and the ammonium ion was supposed to be sorbed (or "extracted") onto the polymer matrix. As an application of sorption of metal complexes, a new hyperfiltration process was proposed for selective separation of metal ions. Thus, a mixture of metal thiocyanate complexes was hyperfiltered through cellulose acetate membranes. Permeation of certain metal complexes was preferred, and the selectivity was found to be similar to the sorption selectivity. These findings lead to a generalized idea that hyperfiltration separation of ionic species, particularly anionic metal complexes, can be attained by using polymer membranes which selectively adsorb or extract such ionic species as ion-association complexes onto the polymer matrix.     

Aqueous biphasic systems formed by nonionic polymers II. Concentration effects of inorganic salts on phase separation

Concentration effects of KSCN, KClO₄, KI, KBr, KNO₃, KCl, KF and K₂SO₄ on the compatibility of dextran with ficoll, polyvinylpyrrolidone and poly(ethylene glycol) at fixed polymer concentration ratios were studied in aqueous solution. The results obtained are considered in terms of the Patterson theory of-effect. It is assumed that phase separation in an aqueous solution of two nonionic polymers results from the appearance of two different water structures in the vicinity of the phase polymers. The data obtained are considered in terms of the concept of salting-in-salting-out effects of neutral salts on aqueous solubility of biopolymers. The salt effects observed are attributed to two antagonistic influences of salts on the electrostatic (dipole-dipole) polymer-water interactions and on the water-water interactions in the vicinity of the phase polymers.     

Thermal diffusivity of some linear polymers

Summary Thermal diffusivity of several linear polymers and cross-linked polyester was measured as Function of temperature between 10‡ and 100 ‡C. Thermal diffusivity is lowered by reducing the interaction between chain molecules in amorphous polymers. In partially crystalline polymers, the crystallinity has a considerable effect on unsteady-state heat conduction. The variation of diffusivity with crystallinity was studied for polyethylene and polytrifluorochloroethylene.

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Zusammenfassung Die Temperaturleitf?higkeit verschiedener linearer Polymeren und vernetzter Polyester wurde als Punktion der Temperatur zwischen 10 und 100 ‡C gemessen. Die Temperaturleitf?higkeit wird durch Reduzierung der Wechselwirkung zwischen den Kettenmolekülen in amorphen Polymeren erniedrigt. In partiell kristallinen Polymeren spielt die Kristallinit?t in betr?chtlicher Weise bei der nichtstation?ren W?rmeleitung eine Rolle. Die Variation der Temperaturleitf?higkeit mit der Kristallinit?t wurde für Poly?thylen und Polytrifluorchlor?thylen untersucht.

     

Thermal degradation of some coordination polymers

Coordination polymers of Co(II), Ni(II) and Cu(II) were synthesized using two ligands, 5- benzylidene pseudothiohydantoin and 5-cinnamylidene pseudothiohydantoin. These polymers were characterized by dynamic and static TG, and their relative thermal stabilities were compared. The thermal stabilities found by dynamic and static TG were in harmony. The structure of the polymeric unit for each polymer was predicted with the help of thermoanalytical data. The data reveal one pattern for Co(II) and Cu(II), i.e. an (ML ₂ ) _n -type polymerkc unit, and another pattern for Ni(II), i.e. an (ML ₂ · 2H ₂ O)_n-type polymeric unit. The static (isothermal) TG data were analysed by use of (i) the difference equation method, and (ii) the Avrami-Erofeyev method. The activation energies of the coordination polymers were calculated, and it was observed that the chelate polymers of Ni(II) with both ligands were more stable than those of Co(II) and Cu(II). This prediction on the basis of static TG data is in agreement with the prediction based on the activation energies and initial decomposition temperatures calculated from the dynamic TG curves.

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Zusammenfassung Koordinationspolymere von Co(II), Ni(II) und Cu(II) mit 5-Benzylidenpseudothiohydantoin bzw. 5-Cinnamyliden-pseudothiohydantoin als Liganden wurden dargestellt, durch dynamische und statische TG charakterisiert und hinsichtlich der relativen thermischen Stabilität miteinander verglichen. Die durch statische und dynamische TG ermittelte thermische Stabilität stimmen überein. Ausgehend von thermoanalytischen Daten wurde die Struktur der Polymereinheit für jedes Polymer vorausgesagt. Ein Thermogrammtyp - (ML ₂ )_n - wird für Co(II) und Cu(H) und ein anderer - (ML ₂ · 2H ₂ O)_n - für Ni(II) erhalten. Die statischen (isothermen) TG-Daten wurden nach der Differenzgleichungsmethode und der Avrami-Erofeyev-Methode analysiert. Die Aktivierungsenergien der Zersetzung der Koordinationspolymere wurden berechnet, und es wurde festgestellt, daß Chelatepolymere von Ni(II) mit beiden Ligandtypen stabiler als die entsprechenden Co(II)- und Cu(II)- Komplexe sind. Diese auf Grund von statischen TG-Daten getroffene Voraussage ist in Übereinstimmung mit der, die auf aus dynamischen TG-Kurven berechneten Aktivierungsenergien und Anfangszersetzungstemperaturen beruht.

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, 5-- 5- - . . . . (ML2)_n - (ML₂ · 2H₂O)_n. - -. . , ' , . , , .

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We express our thanks to the Head of the Department of Chemistry, Nagpur University, for providing the necessary facilities. One of the authors (V. N. I.) is thankful to U. G. C., New Delhi for awarding Junior Research Fellowship.     

Adsorption of some metals on anion-exchange resins from potassium thiocyanate solutions

The adsorption of a number of metals on Dowcx-I from potassium thiocyanate solutions has been studied. Distribution coefficients were measured as a function of thiocyanate concentration for zinc, cobalt, cadmium, scandium, and silver. Some separations of metals employing thiocyanate as the complexing agent are reported.     

Mercury thiocyanate coordination polymers generated from rigid or flexible organic nitrogen donor-based ligands

Four mercury(II) thiocyanate–organic polymeric complexes, [Hg(μ-4,4-bipy)(SCN)₂]_n (1), [Hg(μ-bpa)(SCN)₂]_n (2), [Hg(μ-bpe)(SCN)₂]_n (3), [Hg(μ-bpp)(SCN)₂]_n (4) {4,4-bipy = 4,4′-bipyridine, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethene and bpp = 1,3-di(4-pyridyl)propane} were prepared from reactions of mercury(II) thiocyanate with four rigid and flexible organic nitrogen donor-based ligands under thermal gradient conditions, brunched tube method. All these compounds were structurally determined by X-ray single-crystal diffraction. The thermal stabilities of compounds 1–4 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Solid state luminescent spectra of compounds 1 and 3 indicate intense fluorescent emissions at 430 and 468 nm, respectively.     

Precipitation and solubility of some polonium compounds

Polonium was precipitated from dilute solutions with metaarsenites, dichromates, iodides, molybdates, sulphites, sulphates and metavanadates. The solubility products of polonium iodide, molybdate, sulphite and sulphate were determined to be 1.92, 3.7, 3.3 and 0.9 respectively.     

解读用重金属盐沉淀蛋白质遇到的几个问题

大家知道,用CuSO4、 Pb(Ac)2、AgNO3、HgCl2等重金属盐的溶液作沉淀剂去沉淀蛋白质,使蛋白质变性,这是中学化学讲有机化学时最简单的试管实验,可以说几乎不存在实验不成功的记录,还有什么问题可以值得去研究,去解读的呢.笔者认为,即使是没有失败的记录,也不能说这种实验就不存在值得研究的问题.例如,以CuSO4、Pb(Ac)2作沉淀剂为例.     

Polymerization of acrylamide in nonionic microemulsions: Characterization of the microlatices and polymers formed

Free radical polymerization of acrylamide was carried out in nonionic microemulsions of water, an isoparaffinic oil, Isopar M and a blend of nonionic emulsifiers: a sorbitan sesquioleate and a polyoxyethylene sorbitol hexaoleate (HLB of the mixture: 9.3). The size and the stability of the latex particles formed after polymerization were studied as a function of monomer, emulsifier and electrolyte concentration. High emulsifier and high monomer contents favor obtaining high molecular weight polyacrylamides. It is shown that both the number of polymer chains contained in each latex particle and the size of the particles are essentially controlled by the acrylamide/emulsifier weight ratio.     

Determination of thiocyanate by potassium bromate

Summary Estimation of thiocyanate, based on its titration with standard KBrO₃ solution in presence of 1.5–3.0 N hydrochloric acid, is described. The end point is determined either potentiometrically or with methyl orange as indicator.Sincere thanks of the author are due to Professor S. S. Joshi for research facilities.     

Synthesis of some graft polymers of uracil

Poly-6-(acryloyloxymethyl)uracil was prepared by radical-catalyzed polymerization of monomeric 6-(acryloyloxymethyl)uracil. The reaction of 6-chloromethyluracil with the potassium salt of polyacrylic acids of molecular weights 5000 and 90,000 gave polymers with both carboxylate groups and 50–70% pendant uraciles. Some inferences concerning the arrangement of uracil groups are drawn from the nuclear magnetic resonance (NMR) spectra of the latter polymers. No interaction between poly(A) and the synthetic polymers could be observed.