Complexation of Cd2+, Ni2+, and Ag+ metal ions with 4,13-didecyl-l,7,10,16-tetraoxa-4,13-diazacyclooctadecane in acetonitrile-ethylacetate binary mixtures

Conductometric titrations have been performed in acetonitrile-ethylacetate (AN-EtOAc) binary solutions at 288, 298, 308, and 318 K to obtain the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of Cd²⁺, Ni²⁺, and Ag⁺ cations with 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (cryptand 22DD). The stability constants of the resulting 1: 1 complexes formed between the metal cations and the ligand were determined by computer fitting of the conductance-mole ratio data. There is a non-linear relationship between the logK _f values of complexes and the mole fraction of ethylacetate in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the Cd²⁺, Ni²⁺, and Ag⁺ cations with the ligand changes with the nature of the solvent. The standard enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, the complexation processes of the metal cations with the C22DD, is mainly entropy governed and the values of thermodynamic parameters are influenced by the nature and composition of the binary mixed solvent solutions.     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

Thermosensitive and control release behavior of poly(N-isopropylacrylamide-co-acrylic acid)/nano-Fe3O4 magnetic composite latex particle that is synthesized by a novel method

In this study, a novel method was used to synthesize the poly(N-isopropylacrylamide-co-acrylic acid)/Fe₃O₄ (poly(NIPAAm-AA)/Fe₃O₄) magnetic composite latex. The crosslinked poly(NIPAAm-AA) polymer latex particles were first synthesized by the method of soapless emulsion polymerization, then Fe²⁺ and Fe³⁺ ions were introduced to bond with the -COOH groups of AA segments in poly(NIPAAm-AA) polymer latex particles. Further by a reaction with NH₄OH, Fe₃O₄ nanoparticles were generated in situ. The concentrations of acrylic acid (AA), crosslinking agent (N,N′-methylene bisacrylamide (MBA)), and Fe₃O₄ nanoparticles were important factors to influence the morphology and lower critical solution temperature (LCST) of poly(NIPAAm-AA)/Fe₃O₄ magnetic composite latex particles. The poly(NIPAAm-AA)/Fe₃O₄ latex particles were used as a thermosensitive drug carrier to load caffeine. The control release of caffeine was studies. Morphology-based schematic models were proposed to explain the control release behavior of the composite particles with different compositions. Moreover, the protein (albumin, acetylated from bovine serum (BSA)) was bound on the surface of poly(NIPAAm-AA)/Fe₃O₄ composite latex particles. The effects of AA, crosslinking agent and Fe₃O₄ contents on the amount of BSA binding were investigated at different temperatures and pH values. The composition-morphology-BSA conjugation relationship was established.     

Synthesis and properties of clay-based superabsorbent composite

A novel superabsorbent composites based on acrylic acid, acrylamide, and inorganic clay mineral-attapulgite were synthesized through a solution polymerization to improve water and saline absorbencies. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The effects of saline solutions, amount of initiator, crosslinker and attapulgite on the water absorbency of superabsorbent composites were investigated. The water retention test of superabsorbent composites were also carried out. The superabsorbent composite exhibited improved water and saline absorbencies compared with that of crosslinked poly(acrylic acid-co-acrylamide) superabsorbent polymer. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% reaches more than 1400 g H₂O/g and 110 g H₂O/g in distilled water and 0.9% NaCl solution, respectively.     

Peleg and Weibull models for water absorption of copolymer gels crosslinked on polyethylene glycol dimethacrylates

In this study, the super-absorbent copolymer gels were obtained from the aqueous solution of monomers dispersed in a continuous organic phase. The inverse suspension polymerization was accomplished with the use of aqueous solutions of partly neutralized acrylic acid with a predetermined crosslinker agent, polyethylene glycol dimethacrylates (PEGDMA)/monomer ratio in cyclohexan. The copolymer gels synthesized using PEGDMA crosslinker with three different molecular weights (PEGDMA₃₃₀, PEGDMA₅₅₀, and PEGDMA₇₅₀) were characterized by ?nfrared spectroscopy and scanning electron microscopy. Water absorption capacities of the copolymer gels were determined. The water absorption capacity of 1 g copolymer gels in water was respectively obtained as 232, 255, and 316 g water/g polymer gel for PEGDMA₃₃₀, PEGDMA₅₅₀, and PEGDMA₇₅₀, respectively. The Peleg and Weibull models were used to describe the water absorption behavior of the copolymer gels. The highest values of R ² and the lowest values of χ ² and RMSE for copolymer gels were observed with the Weibull model.     

Synthesis of comb type and semi-interpenetrating networks of acryloyl-l-proline methyl ester and poly (acrylic acid) for Cu (II) immobilization

Graft copolymer hydrogels and semi-interpenetrating networks (s-IPN) of acryloyl-l-proline methyl ester (A-ProOMe) and poly (acrylic acid) (PAAc) were synthesized in methanol solutions, by ionizing radiation (γ rays from a Co⁶⁰ source at room temperature). These systems are thermo and pH-sensitive and the pH sensitivity increases from acidic to basic solutions. The Lower Critical Solution Temperature (LCST), due to presence of poly (acryloyl-l-proline methyl ester) (PA-ProOMe) has been found between 18 and 20 °C and an unexpected Upper Critical Solution Temperature (UCST) due to poly acrylic acid (PAAc) has been found between 21 and 22 °C. Preliminary studies on the immobilization of Cu²⁺ for both hydrogels were done at several pH values at room temperature. Other techniques employed to characterize the comb type hydrogels and sIPN included scanning electronic microscopy (SEM) and infrared (FTIR-ATR).     

Probing the effects of external species on poly(acrylate acid) chain dynamics by using cationic AIE-active fluorophore

We report here our results on the investigation of the chain dynamics of poly(acrylic acid) in aqueous solution. The concentration of poly(acrylic acid) was approximately 3.8×10~(-4) mol/L, two orders of magnitude higher than that reported in the literature. The p H value of the solution was 3.9, and the hydrogen bonds between the intrinsic and ionized carboxylic acid groups formed dynamic networks, which captured aggregation-induced emission-active molecules(a tetra-quaternary ammonium modified tetraphenylethene derivative) inside the polymer coils and induced fluorescence emission. The hydrogen bonds can be classified as intra- or intermolecular; both can be probed based on the emission change of the tetra-quaternary ammonium modified tetraphenylethene probes. The effects of different external stimuli on the polymer chain dynamics were investigated using different metal cations(including Na~+, Li~+, Zn~(2+), Ni~(2+), Ca~(2+), and Co~(2+)), different cation concentrations(1×10~(-6) to 4×10~(-4) mol/L), different poly(acrylic acid) molecular weights(5, 240, and 450 k Da), and different copolymers. The experimental results indicate that the long poly(acrylic acid) chains(high molecular weight) tend to form dense globular coils and exclude the probe molecules outside, which are robust and unsusceptible to water-soluble metal cations. However, the shorter poly(acrylic acid) chains tend to form intermolecular hydrogen bonds, which are helpful in capturing more probe molecules inside the networks, thus inducing stronger emission. Because of the dual functions of forming hydrogen bonds with carboxylic groups and acting as an acceptor of protons from the carboxylic acid group to form cationic species, copolymerization with acrylate amide [poly(acrylic acid)-co-poly(acrylamide)] can greatly affect the chain dynamics of poly(acrylic acid) segments, which is reflected by the drastically decreased emission intensity from the fluorescent probes.     

Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica

Chitosan (CS) and poly(acrylic acid) (PAA) were crosslinked by an ionic gelation method to form super absorbent polymers (SAPs). CS and PAA form amide bonds between the amino and carboxyl groups. The CS-PAA copolymers were synthetically engineered by varying the feed ratios of the prepolymer units. The copolymer materials possess tunable sorption and mucoadhesive properties with a backbone structure resembling proteinaceous materials. The sorption properties of the copolymers toward methylene blue (MB) in aqueous solution were studied using UV-Vis spectrophotometry at ambient pH and 295 K. The copolymers showed markedly varied interactions with MB, from physisorption- to chemisorption-like behavior, in accordance with their composition, surface area, and pore structure characteristics. The sorption isotherms were evaluated with the Sips model to provide estimates of the sorption properties. The sorbent surface area (271 and 943 m²/g) and the sorption capacity (Q_m = 1.03 and 3.59 mmol/g) were estimated for the CS-PAA copolymer/MB systems in aqueous solution.     

Synthesis and Swelling Behaviors of P(AMPS-co-AAc) Superabsorbent Hydrogel Produced by Glow-Discharge Electrolysis Plasma

Highly swelling P(2-acrylamido-2-methyl-1-propanesulfonic acid- co-acrylic acid) (P(AMPS-co-AAc)) superabsorbent hydrogel was synthesized in aqueous solution by a simple one-step using glow-discharge electrolysis plasma technique, in which N,N’-methylenebisacrylamide was used as a crosslinking agent. The structure, thermal stability and morphology of P(AMPS-co-AAc) superabsorbent hydrogel were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. A mechanism for synthesis of P(AMPS-co-AAc) superabsorbent hydrogel was proposed. The reaction parameters affecting the equilibrium swelling (i.e., discharge voltage, discharge time, macroscopic temperature of the liquid phase, mass ratio of AMPS to AAc, and content of crosslinker) were systematically optimized to achieve a superabsorbent hydrogel with a maximum swelling capacity. The hydrogel formed which absorbed about 1,685 g H₂O/g dry hydrogel of the optimized product was used to study the influence of various pH values and salts solutions (NaCl, KCl, MgCl₂, and CaCl₂) on the equilibrium swelling. In addition, swelling kinetics in distilled water and on–off switching behavior were preliminarily investigated. The results showed that superabsorbent hydrogel was responsive to the pH and salts.     

Graft copolymerization of methyl methacrylate onto lignosulfonate by H2O2–Fe(II) redox system. I. Preparation and characterization of the graft copolymer

Graft copolymerization of methyl methacrylate onto lignosulfonate in aqueous medium was investigated. It was found that the H₂O₂–Fe(II) redox system is very effective for the grafting (E_a = 4.4 kcal/mole). The H₂O₂/Fe²⁺ ratio was the most important factor in the graft copolymerization and characteristics of the resultant graft copolymers. In most cases, polymerization for 100 min at 30°C was enough to obtain 80% conversion and 50–60% grafting efficiency. The resultant polymer mixture was subjected to extraction alternately with acetone and water, and the graft copolymer was isolated free from homopolymer and unreacted lignosulfonate. With increasing H₂O₂/Fe²⁺ ratio, the grafting ratio showed a maximum at 4, whereas the yield of graft copolymer and number of poly(methyl methacrylate) branches for every building unit of lignosulfonate increased up to a ratio of 4, both values, however, remaining constant above 4. The graft copolymer obtained for the case H₂O₂/Fe²⁺ = 4 consisted of one part of lignosulfonate and five parts of poly(methyl methacrylate). The number of branches in the graft copolymer was 6 × 10^?3/OCH³ or one every 167 guaiacyl nuclei.     

Polymer films on electrodes: Part XVIII. Determination of heterogeneous electron transfer kinetics at poly(vinylferrocene) and nafion/Ru(bpy)2+3 polymer-modified electrodes by convolution voltammetry

Convolution voltammetry was used to evaluate the rates of heterogeneous charge transfer to ferrocene groups in poly(vinylferrocene) and to Ru(bpy)²⁺₃ in Nafion-modified electrodes under semi-infinite conditions. This technique allows correction for uncompensated resistance and double layer capacitance, as well as detrmination of the diffusion coefficient, D, transfer coefficient, α, and half-wave potential, E_1/2, from a single cyclic voltammogram. Vinylferrocene in solution and a bound copolymer of vinylferrocene and styrene in a ratio of 58:42 were also examined. For the polymer films, the heterogeneous charge transfer rate constants, k°, are 10^?4 ≥ k° ≥ 10^?5 cm/s; these values are about two order of magnitude smaller than those for the similar species in homogeneous solution. The values of k°/D^1/2, however, are comparable to those in soluton; 10 > (k°/D^1/2) > 0.1 s^?1/2.     

Synthesis and in vitro antitumor activity of phthalimide-based polymers containing camptothecin

To improve the therapeutic efficacy of 20(s)-camptothecin (CPT) polymeric drugs containing CPT have been designed. A new CPT-conjugate, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidoacetamidoglycine camptothecin ester (ETPA-gly-CPT), was synthesized by linking its hydroxyl group to the phthalimido monomer through a glycine-glycine spacer. Its homo- and copolymer with acrylic acid (AA) were prepared by photopolymerization using 2,2-dimethoxy-2-phenylacetophenone (DMP) as a photoinitiator. The monomer and its polymers were characterized by IR, ¹H- and ¹³C-NMR spectra. The ETPA-gly-CPT content in poly(ETPA-gly-CPT-co-AA) obtained by elemental analysis was 40 wt.%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n=15,000 for poly(ETPA-gly-CPT), M_n=18,700 for poly(ETPA-gly-CPT-co-AA). The IC₅₀ values of ETPA-gly-CPT and its polymers against cancer cells were much larger than that of CPT.     

Novel comb-type hydrogels of net-[PP-g-AAc]-g-4VP synthesized by gamma radiation,with possible application on Cu2+ immobilization

A novel comb-type grafted hydrogel system of net-[PP-g-AAc]-g-4VP was synthesized by gamma radiation in three steps. In the first step a pH sensitive graft copolymer of AAc onto PP film was obtained by radiation grafting of acrylic acid (AAc) onto polypropylene (PP) films in aqueous solution at radiation doses of 10 kGy with a ⁶⁰Co source. The grafted side chains of poly (acrylic acid) (PAAc) were then cross-linked with gamma radiation at different radiation doses to give net-[PP-g-AAc]. Finally, 4-vinylpyridine (4VP) was grafted into the net-[PP-g-AAc]. The comb-type grafted hydrogel obtained, net-[PP-g-AAc]-g-4VP, has been studied through determination of graft yield and swelling behavior at room temperature. Two critical pH values were found for net-[PP-g-AAc]-g-4VP at 4.5 and 7.2. Initial studies on the immobilization of Cu²⁺ ions from solution into net-[PP-g-AAc]-g-4VP films were performed.The comb-type grafted hydrogel, grafted onto PP was also characterized by differential scanning calorimetry (DSC), scanning electronic microscopy (SEM) and FTIR-ATR.     

An improved one-step method to prepare some diaza-crown ethers and the cation complexation properties of 4,10-diaza-18-crown-6 with two transition metal ions

4,10-Diaza-15-crown-5, 4,10-diaza-18-crown-6, 4,13-diaza-21-crown-7, and 4,16-diaza-24-crown-8 were prepared by an improved method from the appropriate oligothylene glycol diiodides and diamines. The thermodynamic values of log K, ΔH and ΔS for the interaction of 4,10-diaza-18-crown-6 with Pb²⁺ and Ag⁺ were determined by a calorimetric titration method and compared with thermodynamic values for interactions of 4,13-diaza-18-crown-6 with the same cations. The thermodynamic values were found to be different for the two diaza-crown ligands. 4,10-Diaza-18-crown-6 and its 4,13-diaza-crown analog formed precipitates when treated with Co²⁺, Cd²⁺, Cu²⁺, and Ni²⁺ so that no thermodynamic data are reported for these interactions.     

o-Cresol,thiourea and formaldehyde terpolymer – A cation exchange resin

o-Cresol–thiourea–formaldehyde terpolymer resin was synthesized through the condensation of o-cresol and thiourea with formaldehyde in the mole ratio 1:3:5 in the presence of 2 M hydrochloric acid as a catalyst. The resulting copolymer was characterized with IR and ¹H NMR spectral data. The average molecular weight of the resin was determined by Gel permeation chromatography. Thermal study of the resin was carried out to calculate the activation energy (Ea), enthalpy of activation (H³), entropy of activation (S³), free energy of activation (G³), and pre-exponential factor (A) of various steps of thermal decomposition of the terpolymer. The Dharwadkar and Kharkhanavala method has been used to calculate thermal activation energy and thermal stability. The chelation ion-exchange properties were also studied with the batch equilibrium method. The chelation ion-exchange properties of the copolymer was studied for Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. The resin was proved to be selective chelating ion-exchange copolymer for certain metals. The study was carried out over a wide pH range and in media of various ionic strengths.     

Preparation and properties of macroporous superabsorbent composite

A fast swelling macroporous superabsorbent composite was prepared by the copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS), and attapulgite (APT) using N, N′‐methylenebisacrylamide (NNMBA) and trihydroxymethyl propane glycidol ether as crosslinking agents. For fast swelling rate (SR), sodium bicarbonate, polyethylene glycol (PEG), and sodium carboxymethylcellulose (CMC) were introduced into the reaction system as foaming agent and stabilizers. Furthermore, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then blended with aluminum sulfate and sodium carbonate. The influences of the amount of NNMBA, trihydroxymethyl propane glycidol ether, PEG, CMC and sodium bicarbonate, and reaction temperature on water absorbence both under atmospheric pressure and load, and on the SR were investigated. The water absorbence of the sample in 0.9 wt% NaCl aqueous solution under atmospheric pressure and certain load (P ≈ 2 × 10³ Pa) could reach 54 and 8 g.g^?1, respectively, and the SR could reach 0.471 ml g^?1 s^?1. The excellent strength, resilience, and the dispersion of swollen hydrogel were also observed for the sample. Moreover, the surface morphology of macroporous superabsorbent composite was characterized using scanning electron microscope. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of metal ions on the alkali-swelling behavior of carboxylated acrylic polymer latexes

The alkalization of carboxylated acrylic polymer latexes by sodium hydroxide gives rise to swelling of the particles. For a poly(n-butyl acrylate) latex copolymerized with 15 wt % methacrylic acid (MAA) and 7 wt % acrylonitrile the particle volume increases by a factor of 30. The alkali-swelling does not depend on the type of monovalent cation used in the base (LiOH, NaOH, KOH, NH₄OH). In contrast, when bivalent cation bases such as Ca(OH)₂ are employed no latex swelling is observed during neutralization because of ionic crosslinking of the copolymer chains. Crosslinking also takes place when the bivalent cations (Ca²⁺, Zn²⁺, Mg²⁺) are added as chlorides to dispersions with latexes previously swollen by sodium hydroxide. In these experiments the original size of the latexes is reached again at a molar ratio MAA: bivalent metal ion of 2:1, i.e. at charge compensation of the carboxyl groups. The shrinking behavior is almost independent of the type of bivalent metal ion used. On the other hand, it is more pronounced when trivalent cations such as Fe³⁺ are added. In general, the experiments demonstrate that the alkali swelling of acrylic latexes is dominated by electrostatic forces. Received: 18 August 1998 Accepted in revised form: 26 October 1998     

POLY(ASPARTIC ACID) HYDROGEL

ABSTRACT

Stimuli-responsive hydrogels have attracted much interest recently [1]. In this paper, we report a pH- and electrolyte-responsive hydrogel based on a crosslinked poly(aspartic acid). The lightly crosslinked, high molecular weight sodium polyas-partate impart extremely high water absorbency and can be used as a superabsorbent [2], It is derived from a naturally occurring non-toxic amino acid, L-aspartic acid. A hydrogel based on poly(as-partic acid) possesses most of the features of poly(acrylic acid) hydrogels plus improved biodegradability. We expect it to be useful in a variety of applications including personal care and biomedical areas.     

Poly(2-acrylamido glycolic acid-co-acryloyl morpholine) and poly(2-acrylamido glycolic acid-co-acrylamide): Synthesis, characterization, and retention properties for environmentally impacting metal ions

Poly(2-acrylamido glycolic acid-co-acrylamide), P(AGA-co-AAm), and poly(2-acrylamido glycolic acid-co-4-acryloylmorpholine), P(AGA-co-AMo), were synthesized by radical polymerization. The water-soluble polymers containing tertiary amine, amide, hydroxyl, and carboxylic acid groups were investigated as polychelatogen, in view of their metal ion binding properties by using the liquid-phase polymer-based retention technique under different experimental conditions. The retention properties for the following metal ions were investigated: Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Al²⁺, Cr³⁺ and Fe³⁺. P(AGA-co-AMo) showed a selective retention for tri-valent cation Al³⁺ at pH 3, but no retention at higher pH. P(AGA-co-AAm) showed the highest metal ion retention capability, specially at pH 5 and pH 7 with values close to 100% to di-valent cations.     

Effects of concentration and pH on the thermosensitive behavior of a graft copolymer with polyimide backbone and poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino-2-ethyl methacrylate) side chains

Aqueous solutions of the graft copolymer with a polyimide backbone and poly(N,N-dimethylamino-2-ethyl methacrylate) side chains with a molecular mass of M = 4.7 × 10⁵ and a grafting density of side chains of 0.44 are investigated by light scattering and turbidimetry. Solutions are studied in a wide concentration range of 0.0008–0.0250 g/cm³ at рН values varying from 2 to 12 for each concentration. The temperature dependences of optical transmission, scattered light intensity, and hydrodynamic radii of scattering objects are obtained. It is shown that the copolymer is thermosensitive only at pH > 8.0. A decrease in acidity of the medium at a fixed concentration of the copolymer is accompanied by a decline in temperatures corresponding to the onset and end of phase separation Т ₁ and Т ₂, leading to the narrowing of this interval. At constant рН values, temperatures Т ₁ and Т ₂ rise with solution dilution, while the phase transition interval becomes wider.