Water sorption in poly(ammonium sulfopropylbetaines). II. Sorption isotherms

Water sorption by four amorphous acrylic and methacrylic poly(zwitterions) bearing ammonium sulfopropylbetaine side groups () was studied at a constant temperature of 23°C and over a broad range of water activity (0.14-0.90). Whatever the physical state of the hydrated polymer, glassy or viscoelastic, water diffusion is Fickian (average diffusion coefficient D?_s in the range 2-16 × 10^?8 cm² s^?1), and the sorption isotherms may be quantitatively analyzed according to the Guggenheim-Anderson-De Boer amended BET equation for multilayer sorption processes. The number of sitebound water molecules per monomeric unit is in the range 1.5–2.0, and apparently there is no great energy difference between direct site binding and indirect binding in the successive solvation layers. The polymer-water interaction parameter (?0.6 < χ Flory < 0.6) is an increasing function of the water content of the hydrated poly(zwitterions) over the whole composition range (water volume fraction < 0.5), without any clear transition from the glassy to the viscoelastic state. Clustering of water molecules (Zimm-Lundberg theory) is never observed, even at high water content. Because of the charged structure of their dipolar units, the poly(zwitterions) show a water sorption process similar to that of the corresponding poly(electrolytes) of the tetra-alkylammonium sulfonate type. © 1992 John Wiley & Sons, Inc.     

Sorption of alkali metals and silver nitrates from binary and multicomponent solutions by a crown-containing polymer

The equilibrium in the systems containing a polymer based on dibenzo-18-crown-6 and binary or multicomponent aqueous solutions of NaNO₃, KNO₃, RbNO₃, and AgNO₃ was studied. The constants of the sorption of the individual electrolytes from solution into the polymer were determined. Preliminary calculations of the phase composition on sorption of 11 mixtures of electrolytes with a common anion from the data on the equilibria in the systems with one electrolyte are possible.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 464–466, March, 1993.     

Interaction of acridine orange and sodium poly-α, L-glutamate

Summary The interaction of acridine orange and sodium poly-, L-glutamate in the pH range of 3.8–6.8 was studied by a spectral method and viscosity measurement. From the binding data, the molar change in entropy, enthalpy and the number of binding sites on polymer were calculated. The values of S° were positive. S° for binding decreasing extensively in pH range of 5.0. These results are explained by the transition of helix coil of the polymer. The intrinsic viscosity reduction in the presence of the dye, in pH 3.8 is due to the formation of dye bridges between the polymer helix.

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Zusammenfassung Die Wechselwirkung zwischen Natriumsalz-, L-Glutamin-Säure wurde mit den Methoden der Spektroskopie und der Viskositätsmessung untersucht. Aus den Bindungsdaten wurde die molare Änderung von Entropie und Enthalpie und die Zahl der Brückenstellen des Polymeren berechnet. Die Werte von S° sind positiv. Für die Binding ergibt sich für S° eine starke Verminderung im Bereich pH 5.0. Diese ist durch die Änderung der Konformation der Polymerketten (Helix Knäuel-Umwandlung) zu erklären.

     

Sorption and diffusion of organic vapors in amorphous Teflon AF2400

Vapor sorption in amorphous Teflon AF2400 of various organic solutes was studied in a wide range of activity at 25 °C by means of the gravimetric technique. The sorption isotherms of hexane, toluene, and chloroform were shown to be concave to the pressure axis and are consistent with the dual mode sorption model (DMS). The parameters of the DMS model k_D and b reveal a linear correlation with squared critical temperature of solutes T. The third model parameter, the Langmuir sorption capacity C′_H decreases when the size of solutes (critical volume) increases. Sorption isotherms of methanol and ethanol were shown to be convex to the pressure axis and are consistent with cluster formation in this strongly hydrophobic polymer. Concentration‐dependent diffusion coefficients D were determined using a linear implicit difference scheme in analysis of sorption kinetics. It was shown that D values increase exponentially with concentration for all the solutes, except alcohols for which exponential reduction of D(C) was observed. The partitioning of the thermodynamic and mobility contributions in D indicated that the reduction of D values of alcohols is consistent with clustering phenomena in AF2400. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 832–844, 2006     

Amidoamine calix[4]resorcinarene-based oligomers and polymers as efficient sorbents of azo dyes from water

The sorption behaviour of three kinds of macrocyclic sorbents – amidoamine tetradodecyloxyphenylencalix[4]resorcinarene 1 and tetramethyloxyphenylencalix[4]-resorcinarene 2; composition of calix[4]resorcinarene 1+2, and novel P.1 and P.2 polymers with amidoamine calix[4]resorcinarene units towards three water-soluble azo dyes – methyl orange (MO), acid orange (AO5) and Congo red (CR) was studied. All sorbents form supramolecular complexes with the aforesaid dyes. The best sorbent for MO was shown to be polymer P.1, for the AO5 – composition 1+2 and for the CR – macrocycle 2, with high sorption capacities (373, 497 and 625 mg/g, respectively). The main factor in the binding of dyes by all studied sorbents proved to be surface electrostatic interactions. In addition to the Coulomb interactions, the most important factor for the polymers appeared to be the ‘net’ structure of the polymer with a high concentration of binding sites, providing electrostatic, hydrogen, dipole–dipole and hydrophobic interaction. Hydrophobic substituents in the sorbents exert a significant influence on the dye sorption. The increase of the sorbents' hydrophobicity leads to a lower sorption capacity for MO and CR and a higher sorption capacity for AO5. It was shown that sorption efficiency of the sorbent depends on the ‘dye–sorbent’ structure conformity.     

Crown-containing butadienyl dyes. 5. Structure and photoisomerization of a butadienyl dye containing a 15-crown-5 fragment

The structure of the E,E isomer of a butadienyl dye of the benzothiazole series containing a 15-crown-5 fragment was established by X-ray diffraction analysis. The stacking motif of the dye molecules in the crystal structure is, apparently, attributable to intermolecular -interactions between the large conjugated fragments. The possibility of [2+2] photocycloaddition occurring in the crystal is discussed. Reversible geometrical photoisomerization of the dye and its complex with Mg²⁺ in acetonitrile solution was studied by spectrophotometry and ¹H NMR spectroscopy. Photoirradiation of the complex of the E,E isomer with Mg²⁺ leads predominantly to isomerization of the C=C bond adjacent to the benzothiazole fragment. Regioselective E,EZ,E photoisomerization occurs via a singlet mechanism with a quantum yield of about 0.45. The quantum yield of reverse Z,EE,E photoisomerization is approximately 0.52. The structures of different geometrical isomers of the dye complex with Mg²⁺ were calculated by the quantum-chemical density functional theory (DFT).     

Characterization of the sorption of uranium(VI) on different complexing resins

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs–Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions.The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log_110i=–1.16, in more acidic solution, and ML₂ with log_120i=–5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML₂, in more acidic solution, with log_120i=–3.16. In the presence of the ligand EDTA, the complex ML₂(OH)₂ was characterized with log_12–2i=–5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered.     

Quartz Microbalance Microcalorimetry: A new method for studying polymer-solvent thermodynamics

We have developed a sensitive method of determining enthalpy changes for gas-surface interactions: quartz microbalance microcalorimetry. We mount in an isoperibol environment both sample and reference combinations of a quartz crystal microbalance (QCM) in intimate thermal contact with a heat flow sensor. We coat the sample QCM with a thin (1 µm) polymer film. By exposing the film to ethanol vapor, we measure simultaneously the change in mass per unit area (to ±0.25 ng cm^–2) and the resulting heat flows (to ±50 nW) when the polymer adsorbs or desorbs ethanol. The molar enthalpies of sorption of ethanol vapor in Tecoflex, an aliphatic polyurethane elastomer, are _adsorptionH= –53±8 kJ mol^–1 and _desorptionH=52±3 kJ mol^–1.This revised version was published online in November 2005 with corrections to the Cover Date.     

Sorption of C6 Alkanes in Aluminophosphate Molecular Sieve, AlPO4-5

Sorption of C₆ alkanes viz.,n-hexane, 2-methylpentane, 2,2-dimethyl butane, 2,3-dimethyl butane, cyclohexane and methyl cyclopentane in AlPO₄-5 is studied and sorption capacity and thermodynamic parameters (H⁰, H, G, S and S_a) at various sorption coverage for these sorbates have been estimated. The initial heat of sorption (H⁰) is found to increase with the degree of branching in the alkane chain. The sorbate-sorbate interactions are found to be more prominent during the sorption of doubly branched alkanes and cyclic alkanes and a higher sorption capacity has been observed for cyclic alkanes. Based on the results obtained, a packing model has been proposed for various C₆ alkanes inside the AlPO₄-5 channel.     

Water sorption in poly(zwitterions) of the ammonioalkoxydicyanoethenolate type

Water sorption by amorphous (meth)acrylic poly(zwitterions)-bearing quaternary ammonioalkoxydicyanoethenolate side groups , dipole moment μ(D) = 25.9 and 30.8 for p = 2 and 3, respectively was studied at 23°C over a broad range of water activity a (0.14–0.98). Water diffusion is nearly Fickian (D_s = 5.9 10^?7 cm².s^?1 for a = 0.63) and the sorption isotherms may be quantitatively analyzed according to the Guggenheim-Anderson-De Boer equation for a multilayer process characterized by a number of site-bound water molecules per monomeric unit, n_m ? 0.7. The Flory χ interaction parameter is a strongly increasing function of the water content in the glassy hydrated systems and it always remains higher than 0.75. Clustering of water molecules (Zimm-Lundberg theory) is never observed. Differential scanning calorimetry allows to quantify nonfreezable bound water (type I) of strong plasticization efficiency, n(I) = 2.8 mol. of water per monomeric unit, and it points out the quasisimultaneous emergence of low amounts of freezable bound water (type II) crystallizing at ?40°C and melting at ?1°C and of bulkfree water (type III, n(II)/n(III) ? 0.1). All these typical features distinguish these rather hydrophobic poly(zwitterions) from their hydrophilic homologues of the quaternary ammoniopropanesulfonate type . © 1995 John Wiley & Sons, Inc.     

Specific Sorption Sites for Nitrogen in Zeolites NaLSX and LiLSX

Specific sorption sites for nitrogen, N₂, in NaLSX and LiLSX zeolites were investigated using a DRIFT spectroscopic method. Sorption of molecular hydrogen, H₂, by NaLSX or LiLSX zeolite at 77 K with DRIFT control of perturbation of sorbed molecules allowed to discriminate two or three different types of specific sorption sites in the respective zeolites. Their H–H stretching frequencies are 4077 and 4081 cm^–1 for NaLSX, and 4061, 4084 and 4129 cm^–1 for LiLSX. With reference to an independent investigation by methods of both sorption thermodynamics and molecular modeling for N₂ sorption on LiLSX, the first two of the corresponding bands were ascribed to H₂ sorption on lithium cations, Li⁺, localized in supercages of the faujasite, FAU, zeolite framework at sites SIII and SIII, while the latter band most likely belongs to H₂ sorption on Li⁺ cations at sites SII, and on hydroxyl groups, OH. Sorption of N₂ by Li⁺ cations at sites SIII and SIII is the strongest, resulting in a decrease of intensity of the corresponding DRIFT bands that stem from subsequent H₂ sorption. Nitrogen sorption by Li⁺ cations at sites SII is much weaker. Sorption of N₂ on Na⁺ cations at sites SIII in NaLSX zeolite is also stronger than by Na⁺ cations at sites SII.     

Sorption of Cu2+ ions by chitin and chitosan from aqueous solutions. Molecular structure of complexes formed

The sorption of Cu²⁺ ions by chitin and chitosan from aqueous solutions has been investigated, as well as the molecular structure of the complexes formed. The static exchange capacities have been determined, equal to 3.5 and 0.25 mmole/g for chitosan and chitin, respectively, and the partition coefficients (5000 and 70 g/ml). It has been shown that in complex formation a bond with the amino group is formed as the result of the substitution of a proton in the latter. The EPR spectra of these complexes have been obtained and their radiospectroscopic parameters determined (g = 2.334,g = 2.054,A = 0.0156 cm^–1, andB = 0.0028 cm^–1 for chitin, andg = 2.231,g = 2.048,A = 0.0192 cm^–1, andB = 0.0025 cm^–1 for chitosan). For chitosan the ligands are two nitrogen atoms of the amino groups and two oxygen atoms of the hydroxyl groups in the position C³ of adjacent glucosamine rings; for chitin, the oxygen atoms of the acetyl groups take part in addition in the complex formation. The analysis of the radiospectroscopic parameters and their comparison with published data lead to the conclusion that the Cu²⁺ complex with chitosan has a tetragonal symmetry, while the complex with chitin most probably has an octahedral structure.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2305–2311, October, 1992.     

Determination of thermodynamic functions of sorption for cyclohexyl-, piperidyl-, morpholyl-, and thiomorpholyl-n-alkanes by capillary gas-liquid chromatography

The values of partial molar free energy (G), enthalpy (H), and entropy (S) of sorption in the homologous series ofN-alkylpiperidines,N-alkylmorpholines,N-alkyl thiomorpholines, and alkylcyclohexanes were determined. It was found that the free energy of sorption is determined to a greater extent by the enthalpy term than by the entropy one. The free energy of sorption of the first homolog decreases when then-alkyl chain is attached directly to the carbon atom of the cycle and increases in the case ofN-alkylsubstituted heterocycles. The influence of the heteroatom nature on intermolecular interactions of homologs with the nonpolar stationary phase was quantitatively estimated on the basis of thermodynamic data.Dead time necessary for calculation of the retention factor was determined by the retention of methane injected into the column simultaneously with the sample.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2030–2032, August, 1996.     

Complex Sorption Kinetics of Carbon Dioxide in NaX-Zeolite Crystals

Ad-/desorption-kinetic measurements were performed for carbon dioxide on a mono-disperse crystal sample of NaX-type zeolite (mean crystal diameter: 2R (100 ± 6) m) by a constant-volume–variable-pressure method in a differential concentration mode over ranges of temperature, (193–293) K, and pressure, (20–26,700) Pa. They revealed a complex sorption process in sorbate uptake and release during experiments of ad- and desorption, respectively, which is comprised of a slow, hitherto unknown rate mechanism superimposed on very fast intracrystalline diffusion of carbon dioxide. IR-spectroscopic data that evidence formation of chemisorption species in CO₂-NaX sorption systems may allow for a tentative interpretation of this finding. Circumstantial evidence for the correctness of this conclusion follows from sorption–kinetic experiments for carbon dioxide on BaKX-type zeolite crystals (mean crystal diameter: 2R (120 ± 6) m).     

Crystallization of low and high molecular materials

For a better understanding of the crystallization of high molecular materials the paper starts with detailed statements as to the crystallization of low molecular materials. In this way it can be shown that there exist more properties in common than supposed before. This fact becomes evident from the thermodynamical point of view if the polymer is formally considered as a 2-components-system. In this system the stable rotational isomers, viz., the trans- and the gauche-form, are the components. In that case the crystallization process of linear polyethylene (HDPE) can be regarded as a crystallization of the trans-form in a trans-gauche mixture.In the paper the critical nuclei, which build up at the beginning of the crystallization and which have so-called equilibrium shapes, as well as the complete crystals, which have so-called growth shapes influenced by the kinetics of formation, are discussed. Special attention is paid to the lamellar growth because it often occurs in polymers. It is shown that the lamellar growth can be attributed to an activated sorption of foreign substances. In many polymers the role of the foreign substance is played by the gauche-form (autogenous activated sorption).By means of electron micrographs and calorimetric measurements of HDPE samples with a bimodal distribution of the lamellar thicknesses it could be proved that the melting range of polymers is due to a distribution of the lamellar thicknesses and apparently not to a changing conformational parts _Lk of the melting entropy as supposed by other authors [1]. Values from the literature for the conformational entropys _Lk of different polymers confirm in a good approximation thats _Lk can be compared to a mean entropy of mixing of the 2-components-model for polymers. This result makes evident that Flory's model for a polymer melt of interpenetrating chain coils can indeed be replaced, in a good approximation, by an ideal mixture of independent trans and gauche units in the sense of the 2-components-model. There follows in conclusion thats _Lk is a function of the gauche-trans ratio.Dedicated to Professor Dr. F. H. Müller. Presented at the Festive Colloquium, 7 May, 1982, in Marburg/Lahn, on the occasion of the 75th birthday of Professor Dr. F. H. Müller.Presented at the 14th Europhysics Conference on Macromolecular Physics, 21–24 September, 1982, in Vilafranca del Penedès (Barcelona), Spain.     

Sorption of methanol/MTBE and diffusion of methanol in 6FDA–ODA polyimide

This article discusses the diffusion and solubility behavior of methanol/methyl tert‐butyl ether (MTBE) in glassy 6FDA–ODA polyimide prepared from hexafluoroisopropylidene 2,2‐bis(phthalic anhydride) (6FDA) and oxydianiline (ODA). The diffusion coefficients and sorption isotherm of methanol vapor in 6FDA–ODA polyimide at various pressures and film thicknesses were obtained with a McBain‐type vapor sorption apparatus. Methanol/MTBE mixed‐liquid sorption isotherms were obtained by head‐space chromatography and compared with a pure methanol sorption isotherm obtained with a quartz spring balance. Methanol sorption isotherms obtained with the two methods were almost identical. Both methanol sorption isotherms obeyed the dual‐mode model at a lower activity, which is typical for glassy polymer behavior. The MTBE was readily sorbed into the polymer in the presence of methanol, but the MTBE sorption isotherm exhibited a highly nonideal behavior. The MTBE sorption levels were a strong function of the methanol sorption level. Methanol diffusion in the polymer was analyzed in terms of the partial immobilization model with model parameters obtained from average diffusion coefficients and the dual‐mode sorption parameters. Simple average diffusion coefficients were obtained from sorption kinetics experiments, whereas the dual‐mode sorption parameters were obtained from equilibrium methanol sorption experiments. An analysis of the mobility and solubility data for methanol indicated that methanol tends to form clusters at higher sorption levels. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2254–2267, 2000     

Interaction of dye and synthetic sucrose polymer Ficoll

Summary The interaction of Ficoll and Benzopurpurine 4B was studied by spectral method and viscosity measurement. From the binding data the molar changes in entropy and enthalpy, and the number of binding sites on polymer were calculated. Both values of H ⁰ and S ⁰ were positive. The valuen increases with increasing temperature. These results may be explained by the change of the configuration of polymer chain. The intrinsic viscosity reduction in the presence of the dye is due to the formation of dye bridges.

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Zusammenfassung Die Wechselwirkung zwischen Ficoll und Benzopurpurin 4B wurde mit den Methoden der Spektroskopie und der Viskositätsmessung untersucht. Aus den Bindungsdaten wurde die molare Änderung von Entropie und Enthalpie und die Zahl der Brückenstellen des Polymeren berechnet. H ⁰ und S ⁰ sind beide positiv. Dern-Wert nimmt mit der Temperatur zu. Dies ist durch die Änderung der Konfiguration der Polymerketten zu erklären. Die Viskositätsabnahme mit Zusatz von Farbstoff ist auf die Bildung von Farbstoffbrücken zurückzuführen.

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Mit 3 figures and 2 tables     

Sorption of azo dyes from aqueous solutions by tetradodecyloxybenzylcalix[4]resorcinarene derivatives

Four water-insoluble tetradodecyloxybenzylcalix[4]resorcinarenes with various functional groups at the upper macrocycle rim (unsubstituted calix[4]resorcinarene 1, carboxylic acid derivative 2, ethyl ester derivative 3 and aminoethylamide derivative 4) were synthesized and tested as sorbents for water-soluble azo dyes methyl orange (MO), acid orange 5 (AO 5) and congo red (CR) by solid–liquid extraction method without background electrolyte. It was observed that the sorption of azo dyes reaches 99% for sorbent 4, which is partial protonated in contact with water and becomes able to electrostatic interactions with the dyes. It was demonstrates that calixresorcinarene 4 has the excellent sorption capacity for AO5 (130.5?mg dye per g of sorbent) due to effective calixresorcinarene—dye association in equal molar ratio mode.     

Adsorption and Desorption of Cr(III) on Natural and Chemically Modified Slovak Zeolites

Natural and chemically modified zeolites from the Slovak Republic and Ukraine have been investigated as the adsorbents for the uptake of Cr(III). Model water solution of low radioactivity was used. The adsorption and desorption kinetics of chromium were established with the gradual radioexchange technique (tracer ⁵¹Cr) and flame AAS. The effect of the factors studied are examined and explained. The sorption coefficient , distribution coefficient K _D , sorption capacity , sorption rate S, and leachability of Cr were calculated in neutral, alkaline and acidic aqueous solutions. The sorption capacity of the modified zeolites was found to be greater by a factor of 2 to 16 than that of the unmodified ones depending on the modifying solution applied. The leachability of chromium from loaded zeolites into the neutral solution was negligible. The leachability into alkaline and acidic solutions increased over 40%.