Showing papers in "Reactive & Functional Polymers in 2008"

Chitosan-modifications and applications: Opportunities galore

Abstract: Of late, the most bountiful natural biopolymer chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However applications of chitin are limited due to its inherent insoluble and intractable nature. Chitosan, alkaline hydrolytic derivative of chitin has better solubility profile, less crystallinity and is amenable to chemical modifications due to presence of functional groups as hydroxyl, acetamido, and amine. The chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. In view of rapidly growing interest in chitosan its chemical aspects and chemical modification studies is reviewed. The several chemical modifications such as oligomerization, alkylation, acylation, quternization, hydroxyalkylation, carboxyalkylation, thiolation, sulfation, phosphorylation, enzymatic modifications and graft copolymerization along with many assorted modifications have been carried out. The chemical modification affords a wide range of derivatives with modified properties for specific end use applications in diversified areas mainly of pharmaceutical, biomedical and biotechnological fields. Assorted modifications including chitosan hybrids with sugars, cyclodextrin, dendrimers, and crown ethers have also emerged as interesting multifunctional macromolecules. The versatility in possible modifications and applications of chitosan derivatives presents a great challenge to scientific community and to industry. The successful acceptance of this challenge will change the role of chitosan from being a molecule in waiting to a lead player.

Preparation of phosphorylated bacterial cellulose as an adsorbent for metal ions

Abstract: Bacterial cellulose is extracellular cellulose synthesized by some bacteria. The thickness of the microfibrous structure of bacterial cellulose is much less than that of plant cellulose. In the present paper, phosphorylated bacterial cellulose is prepared as an adsorbent for metal ions. Phosphorylation conditions were screened to increase the substitution degree and to retain the microfibrous structure. The degree of phosphorylation of bacterial cellulose is higher than that of plant cellulose under the same conditions. Scanning electron microscopy images of the phosphorylated bacterial cellulose indicated that the final product exists as an aggregated ribbon structure. Batchwise adsorption tests of lanthanide ions and transition metal ions on the phosphorylated bacterial cellulose were performed. The metal ions were adsorbed on the phosphorylated bacterial cellulose and selectivity was based on the characteristics of the phosphoric acid groups. These results suggest potential for phosphorylated BC as a new adsorbent for metal ions.

Heavy metals adsorption on some iminodiacetate chelating resins as a function of the adsorption parameters

Abstract: The adsorption properties of some novel chelating resins (CRs) bearing iminodiacetate groups for removal of heavy metal ions like: Cu(II), Co(II) and Ni(II) from aqueous solutions comparative with the commercial resin Amberlite IRC-748 have been studied in this work by a batch equilibrium technique Quantitative analysis for adsorption was conducted using UV–vis spectroscopy to investigate the kinetics, adsorption isotherm and thermodynamics of the removal process considering equilibration time, pH, metal ion concentration and temperature as controlling parameters The metal adsorption capacities, at pH 5, were in the order Cu(II) > Ni(II) > Co(II), for both the CR with 10 wt% DVB (CR-10) and the commercial resin Amberlite IRC-748 The adsorption capacities on CR-10 were higher for Ni(II) and Co(II) ions, but lower for Cu(II) ions compared with Amberlite IRC-748 Both Freundlich and Langmuir isotherms well fitted on the adsorption results of Cu(II), Ni(II) and Co(II) ions on all iminodiacetate resins

Synthesis and characterization of polythiophene/titanium dioxide composites

Abstract: Polythiophene/titanium dioxide (PT/TiO2) composites were prepared by the in situ chemical oxidative polymerization method. The resulting PT/TiO2 composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). UV–Vis diffuse reflectance spectra measurements show that the PT/TiO2 composites can adsorb light of wavelengths ranging from 200 nm to 800 nm. The PT/TiO2 composites showed good adsorption properties and were more efficient in removing dye from solution than pure PT and pure TiO2. The PT/TiO2 composites exhibited photocatalytic activities to some extent under UV light illumination.

Removal of Pb2+, Cu2+, and Fe3+ from battery manufacture wastewater by chitosan produced from silkworm chrysalides as a low-cost adsorbent

Abstract: In this work, it was investigated the best ChSC deacetylation time (DT) for the removal of Pb2+ and Cu2+ from battery manufacture wastewater. Bath experiments were used to determine the best adsorption conditions. The best DT for Cu2+ removal was 180 min (92% deacetylation) and for Pb2+ removal was 90 min (80% deacetylation). The maximum adsorption capacities of Pb–ChSC and Cu–ChCS were 0.4247 mmol g−1 and 1.5953 mmol g−1, respectively, for contact time of 24 h, pH 5.0, particle size from 300 to 425 μm, and temperature of 20 ± 0.1 °C. Metal adsorption onto ChSC was evaluated by Langmuir and Freundlich isotherms. An experimental column packed with ChCS was used to remove Fe3+, Cu2+, and Pb2+ from battery wastewater. Experimental column results were obtained by plotting C/C0 against time. Metal adsorption onto ChSC in column was higher at pH 5.0 than pH 3.0. The results of this work support the use of ChSC in battery wastewater treatment.

Chitosan crosslinked with a metal complexing agent: Synthesis, characterization and copper(II) ions adsorption

Abstract: In this study, chitosan was crosslinked using the complexing agent N-N′-[bis(2-hydroxy-3-formyl-5-methylbenzyl-dimethyl)]-ethylenediamine (H2fmbme). The chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis (TGA). The new chelating polymer was used in batch processes to study Cu(II) ion adsorption in aqueous solution. The results showed that adsorption was dependent on the pH of the solution, with a maximum capacity at around pH 6.0. The adsorption kinetics data were best fitted with the pseudo second-order model, which gave a correlation coefficient of 0.999 and a 1.53% deviation between experimental and calculated qe values. The adsorption equilibrium data were fitted with the Langmuir isotherm (R = 0.999), which revealed that the maximum capacity for monolayer saturation was 113.6 mg Cu(II) per gram of the new adsorbent material (1.79 mmol/g).

Reprotonation of polyaniline: A route to various conducting polymer materials

Abstract: Polyaniline (PANI) is one of the most studied conducting polymers. Its properties can be modified by controlling the way of protonation. Polyaniline base was immersed in aqueous solutions of 42 inorganic or organic acids in order to find out, which is able to constitute a salt with the PANI base and what are the properties of products. The conductivity of the reprotonated PANI bases is determined especially by the pH of acid solutions. The highest conductivity, 1.22 S cm −1 , was found after reprotonation of PANI base with 50% tetrafluoroboric acid. The reaction with most strong inorganic acids yielded samples with a conductivity of 10 −1 S cm −1 . Sulfonic acids gave products having conductivity of the order of 10 −2 –10 −1 S cm −1 . Carboxylic acids were less efficient in protonation, and their ability to produce a conducting polymer depended on increasing the acid concentration. Acids containing an acidic hydroxyl group, like picric acid, also protonated PANI to a good level of conductivity. The lowest conductivity, 1.8 × 10 −10 S cm −1 , was observed in the absence of any acid. The density of reprotonated PANI varied between 1.19 and 2.06 g cm −3 , the contact angle between 29° and 102°, and volume change between −14% and +33%, depending of the acid used. The reprotonation of PANI base with various acids offers the opportunity to prepare materials with great variability and versatility in properties.

Polyaniline/magnetic ferrite nanocomposites obtained by in situ polymerization

Abstract: Polyaniline (PANI)–Zn 0.6 Cu 0.4 Cr 0.5 Fe 1.5 O 4 nanocomposites with magnetic properties were synthesized by in situ polymerization of aniline in the presence of Zn 0.6 Cu 0.4 Cr 0.5 Fe 1.5 O 4 nanoparticles. The structure and morphologies of nanocomposites were characterized by X-ray diffraction (XRD), infrared spectra, UV–vis absorption spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ferromagnetic behaviors of nanocomposites were investigated as a function of the content of Zn 0.6 Cu 0.4 Cr 0.5 Fe 1.5 O 4 particles. The SEM and TEM images showed that nanocomposites presented the core-shell structure with a magnetic core of ferrite and a conducting shell of PANI. The nanocomposites under applied magnetic field exhibited the hysteresis loops of the ferromagnetic nature. The saturation magnetization and coercivity of nanocomposites varied with the content of Zn 0.6 Cu 0.4 Cr 0.5 Fe 1.5 O 4 particles.

Swelling and dye sorption studies of acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid/bentonite highly swollen composite hydrogels

Abstract: Water uptake and the sorption properties of polyelectrolyte composite hydrogels made by the polymerization of acrylamide (AAm) with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and a clay such as bentonite (Bent) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with AMPS as comonomer and a multifunctional crosslinker such as ethylene glycol dimethacrylate (EGDMA). FT-IR analyses were made. Swelling experiments were performed in water and dye solution at 25 o C, gravimetrically. Highly swollen AAm/AMPS and AAm/AMPS/Bent hydrogels were used in experiments on sorption of water–soluble monovalent cationic dye such as Lauths violet “LV, (Thionine)”. Swelling of AAm/AMPS hydrogels was increased up to 2282–12,603% in water and 921–3575% in LV solutions, while AAm hydrogels swelled 927% in water and swelling of AAm/AMPS/Bent hydrogels was increased up to 3225–15,421% in water and 1360–4189% in LV solutions, while AAm/Bent hydrogels swelled 828% in water. Some swelling kinetic and diffusional parameters were found. Water and LV diffusion into hydrogels was found to be non-Fickian in character. For sorption of cationic dye, LV into AAm/AMPS and AAm/AMPS/Bent hydrogel was studied by batch sorption technique at 25 o C. AAm/AMPS and AAm/AMPS/Bent hydrogels in the dye solutions showed coloration. The amount of the dye sorbed per unit mass removal efficiency and partition coefficient of AAm/AMPS and AAm/AMPS/Bent hydrogels was investigated. The influence of AMPS content in hydrogels to sorption was examined.

Extraction of phenols from aqueous solutions by β-cyclodextrin polymers. Comparison of sorptive capacities with other sorbents

Abstract: The removal of phenols from aqueous solutions by crosslinked β-cyclodextrin polymers has been studied. For cresols, the position of the methyl group influences the interaction with cyclodextrin polymers crosslinked with epichlorohydrin, being p-cresol the most adsorbed one. The isosteric heat of adsorption is almost constant with the surface coverage in the case of phenol, but varies for the cresols. When compared with other typical sorbents used to extract phenol from water (activated carbon, the macroporous resin Lewatit OC 1064, and calcium alginate), cyclodextrin polymers crosslinked with different reagents (epichlorohydrin, succinyl chloride and two diisocyanates) show high sorption capacities, especially at high phenol concentrations.

A novel strategy for the synthesis of polyaniline nanostructures with controlled morphology

Abstract: Polyaniline (PANI) nanostructures with sheets-, fiber- and spherical-like morphologies were synthesized from p-toluene sulfonic acid (p-TSA) aqueous solution. The results demonstrate that the morphology of PANI nanostructures was significantly influenced by the molar ratio of aniline to p-TSA. Other experimental parameters, such as polymerization temperature and the concentration of ammonium peroxydisulfate (APS), also have an influence on the morphology of PANI nanostructures. A rational mechanism based on the self-assembly of micelles is proposed for the formation of PANI nanostructures. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV–visible spectroscopy (UV–vis) and X-ray diffraction (XRD) were applied to characterize the products.

Surface modification of a synthetic polyurethane by plasma glow discharge: Preparation and characterization of bioactive monolayers

Abstract: In the present study, a surface functionalization of a synthetic polyurethane was carried out by using biofunctional moieties to obtain a material with the appropriate mechanical properties and processing conditions and, at the same time, the advantages of a bioactive material. The polyurethane (PU) was synthesised from poly(e-caprolactone) diol, 1,6-diisocyanatohexane and 1,4-cyclohexane dimethanol as chain extender. PU films were grafted with acrylic acid using argon plasma. The carboxyl groups formed were used to covalently bind model biomimetic/bioactive macromolecules (gelatine and poly ( l -lysine). All characterizations (attenuated total reflection Fourier transform infrared spectroscopy, ATR-FTIR; X-ray photoelectron spectroscopy, XPS; atomic force microscopy, AFM; scanning electron microscopy, SEM) confirmed the surface changes at each stage of treatment, both in morphology and in chemical composition. Besides, achieved treatment allowed to obtain a very thin layer of both PAA and macromolecules. Moreover, preliminary in vitro tests were performed using NIH-3T3 fibroblasts as cell model. Both materials showed to support cell adhesion and growth, with poly ( l -lysine) performing better in activating cellular processes, as it can be seen by cell shape, which appears elongated on poly ( l -lysine) coating, whereas on gelatine, cells are more spherical and not uniformly distributed on the polymer surface.

Cadmium extraction from hydrochloric acid solutions using Amberlite XAD-7 impregnated with Cyanex 921 (tri-octyl phosphine oxide)

Abstract: Cyanex ® 921 (tri-octyl phosphine oxide, TOPO) was successfully used for the impregnation of Amberlite ® XAD-7 to prepare an extractant-impregnated resin (EIR). This EIR was used for the recovery of cadmium from concentrated HCl solutions. Though the maximum loading of Cyanex 921 in the EIR can reach 580 mg g −1 , a lower concentration (below 400 mg g −1 ) enabled better use of the extractant. The Langmuir equation was used to model the sorption isotherms and the maximum sorption capacity was found to be 13 mg Cd g −1 , for a EIR with 366 mg Cyanex 921 g −1 in a 3 M HCl solution (containing about 60 mg Cd L −1 ), in which equilibrium was reached within 8 h contact time. The extraction mechanism involved various solvating reactions with neutral CdCl 2 and ion pairs (involving associations between protons and anionic cadmium chloro-species). It was difficult to determine the extracted species due to the simultaneous co-extraction of HCl on the EIR. Cadmium can be efficiently desorbed using a diverse range of eluents and the possibility of re-using the resin was demonstrated over four cycles.

Photoreversible poly(ethylene glycol)s with pendent coumarin group and their hydrogels

Abstract: The novel photosensitive chain extender (ICM) was prepared by condensation of 5-hydroxyisophthalic acid (I) and 7-chlorocarbonylmethoxycoumarin (CM). ICM acid chloride was polycondensed with poly(ethylene glycol)s (PEG)s of different molecular weights (Mn = 1000, 3000, 8300 g/mol). The resulting high-molecular-weight PEGs having a coumarin moiety in the pendent group (ICM) underwent rapid reversible photo-cross-linking upon exposure to alternating wavelength of irradiation (>280/254 nm) in the absence of photoinitiators. The melt-pressed PEG films were exposed to the wavelength of >280 nm to produce a hydrogel. Gel contents attained over 90% for ICME3000 and 80% for ICME8300, respectively, within 5 min, These gels were swollen in water and showed characteristic properties of a hydrogel. The degree of swelling could be controlled by the irradiation time as well as MWs of PEG.

Studies on graft copolymerization of 2-hydroxyethyl acrylate onto chitosan

Abstract: Graft-polymerization of 2-hydroxyethyl acrylate (HEA) onto chitosan (CS) using ammonium persulfate (APS) as an initiator was carried out in an aqueous solution. Evidence of grafting was obtained by comparing 1 H NMR and FT-IR spectra and scanning electron microscopy images of chitosan and the grafted copolymer as well as solubility characteristics of the products. The effects of APS, HEA concentration, reaction temperature and duration of graft-polymerization were studied by determining the grafting parameters, such as grafting percentage and grafting efficiency. The HEA-grafted chitosan product is soluble in a wide pH range, while the original unmodified chitosan is water-soluble only in a narrow pH range. A mechanism for the free-radical grafting was proposed.

Rebinding and recognition properties of protein-macromolecularly imprinted calcium phosphate/alginate hybrid polymer microspheres

Abstract: Calcium phosphate/alginate hybrid polymer microspheres with bovine serum albumin (BSA) embedded and coated on the surface were prepared with sodium alginate (SA) and (NH4)2HPO4 by using CaCl2 as the gelling agent in an inverse suspension. The morphology and pore structure of imprinted hybrid polymer microspheres was observed by optical microscopy, ESEM, TEM and SEM. Infrared spectrum analysis demonstrated that new hybrid components were produced in the polymer microspheres. Rebinding dynamic and thermodynamic behaviors of the two imprinted microspheres were evaluated, resulting in a higher BSA affinity for imprinted microspheres relative to non-imprinted ones. The factors influencing the imprinting efficiency (IE) of imprinted microspheres were also studied, including the concentration of CaCl2, template content and pH in rebinding solution, etc. All the results indicated that the surface imprinted microspheres exhibited better imprinting efficiency and higher rebinding capacity. Selectivity tests showed that the imprinted beads exhibited good recognition properties for the template protein versus others.

Immobilization of Cyphos IL-101 in biopolymer capsules for the synthesis of Pd sorbents

Abstract: Cyphos® IL 101, a tetraalkyl-phosphonium chloride salt, (ionic liquid, IL) was immobilized in capsules prepared by ionotropic gelation in calcium chloride solutions. These resins were tested for Pd recovery from HCl solutions. The sorption performance is slightly controlled by the concentration of HCl, in the range 0–2 M, with maximum sorption capacities close to 130–145 mg Pd g−1 resin (i.e. 1.2–1.4 mmol Pd g−1 resin or 0.96–1.07 mmol Pd mmol−1 Cyphos IL-101). Palladium, essentially present in the form PdCl 4 2 - is probably bound to the resin through anion exchange with protonated phosphonium groups (ion pair formation). Decreasing the amount of IL immobilized in the resin improves the rational use of the IL (higher molar ratio Pd/IL). The presence of other anions, for example nitrate, or other chloro-metal complexes, ZnCl 4 2 - decreases Pd binding, while other metals that do not form anionic complexes under the selected experimental conditions (for example Cu or Ni) do not interfere with Pd uptake. The pseudo-second-order rate equation was successfully used to model the kinetic profiles. Kinetics are mainly controlled by intraparticle diffusion resistance (low effect of agitation speed on the kinetic profiles). Crank’s equation was used to model intraparticle diffusion, giving intraparticle diffusivities close to 0.7–1.5 × 10−12 m2 min−1 for dry material and up to 5 × 10−12 m2 min−1 for wet resin. Drying the resin has a significant impact on mass transfer: uptake kinetics are improved by using raw resins. Desorption of the metal loaded resins can be performed using thiourea (in 0.1 M HCl solution) or HNO3 (5 M). The recycling and re-use of the resin was successfully demonstrated over three cycles; at the third desorption step a partial degradation of the resin was observed.

Inkjet printing of 3D metal-insulator-metal crossovers

Abstract: The inkjet deposition of a single functional material on a substrate is well developed, however, little attention has been paid to the sequential printing of different functional elements to generate complex 3D structures. The successful all additive manufacture of electronics circuits requires the printing of features such as crossovers and interconnections, the passive elements in electronics where metal–insulator–metal must be sequentially deposited with retained function. We describe the inkjet printing of both a commercial silver nanoparticle metal and a cationic/thermally cured epoxy insulator, SU8, and discuss the role of print strategy and surface treatment on retaining functionality. The issues to be addressed in the successful all inkjet printing of such features are discussed.

Fully biodegradable poly(3-hydroxybutyrate-co-hydroxyvalerate)/poly(ethylene succinate) blends: Phase behavior, crystallization and mechanical properties

Abstract: Poly(3-hydroxybutyrate- co -hydroxyvalerate) (PHBV) and poly(ethylene succinate) (PES) are both biodegradable semicrystalline polyesters. Phase behavior, crystal structure, crystallization kinetics, and mechanical properties of fully biodegradable PHBV/PES blends were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), wide angle X-ray diffraction (WAXD), and tensile tests in detail. PHBV is immiscible with PES as evidenced by the two composition independent glass transition temperatures corresponding to those of neat components. Moreover, the biphasic melt further confirms the immiscibility between PHBV and PES. Nonisothermal and isothermal crystallization of PHBV/PES blends were studied by DSC. In the case of isothermal crystallization the crystallization rates of PHBV and PES decrease with increasing the content of the other component for both PHBV-rich and PES-rich blends; however, the crystallization mechanisms do not change. The mechanical properties of PHBV/PES blends were examined by tensile testing. It is found that the tensile strength, elongation at break, Young’s modulus, and toughness of PHBV blends can be adjusted by changing blend composition. For PHBV-rich blends, blending some amount of PES can improve the elongation at break significantly while still keeping considerably high tensile strength and Young’s modulus.

Preparation of conducting polyaniline/TiO2 composite submicron-rods by the γ-radiolysis oxidative polymerization method

Abstract: Conducting polyaniline (PAni)–titanium dioxide (TiO2) composite micron-sized rods have been synthesized using an in situ gamma radiation-induced chemical polymerization method. Aqueous mixtures of aniline, a free-radical oxidant and/or titania nanoparticles were irradiated with γ-rays. The formation of PAni–TiO2 composite submicron-rods is the result of free aniline cation-radicals and adsorbed aniline cation-radicals on the surface of TiO2 nanoparticles growing together with the aid of high-energy gamma irradiation. SEM and TEM images represent the PAni–TiO2 composite rods as having a diameter range of 0.2–0.5 μm. Electrical conductivities were checked by the standard four-point probes method and found to be 0.28 S/cm for bulk PAni and 0.15 S/cm for PAni–TiO2 composite submicron-rods. UV–visible absorption spectroscopy showed two electronic bands at about 320 and 596 nm for bulk PAni and blue-shifted bands due to the formation of PAni–TiO2 composites. Thermogravimetric analysis revealed that the composites have a higher degradation temperature than polyaniline alone.

Biocidal polymers (I): Preparation and biological activity of some novel biocidal polymers based on uramil and its azo-dyes

Abstract: Biocidal polymers were prepared by reacting uramil with polyacrylonitrile and polyethylacrylate, and also by co-polymerizing heterocyclic monomers based on uramil azo-dyes with tolylene-2,6-diisocyanate and toluene-2,4-diisocyanate. The prepared polymers were converted to their quaternary salts and N-halamine forms. Prepared N-halamine polymers were designed to contain multi-available positions for halogenation and quaternarization and to tune the stability of halogens attached to the polymers. Antimicrobial activity of the prepared polymers against examples of Gram-positive and Gram-negative bacteria was examined.

Synthesis and characterization of superabsorbent composite by using glow discharge electrolysis plasma

Abstract: A convenient and effective technique for polymerization to produce the poly(acrylic acid-co-acrylamide)/montmorillonite superabsorbent composite in aqueous solution was developed, in which the reaction was initiated by the glow discharge electrolysis (GDE) plasma rather than chemical initiators. The resulted superabsorbent has higher water absorbency, for example, 1024 g g −1 for distilled water and 56 g g −1 for 0.9% NaCl solution. To optimize the synthesis conditions, the following parameters were examined in detail: the discharge voltage, discharge time, ratio of acrylic acid to acrylamide, neutralization of acrylic acid, amount of crosslinking agent and montmorillonite added. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Results indicated that montmorillonite was effectively bonded with polymer. Moreover, the water absorbency, water retention and thermal stability of the superabsorbent composite prepared by GDE were higher than those of the superabsorbent composite by conventional chemical method under the same polymerization conditions.

Adsorption properties of amidoxime resins for separation of metal ions from aqueous systems

Abstract: In this study, the acrylonitrile (AN)–divinylbenzene (DVB)–methylacrylate (MA) resin was synthesized via suspension polymerization in the presence of toluene as diluent, and benzoylperoxide (BPO) as initiator. The effects of MA as a hydrophilic agent and toluene as a diluent on the anion and cation exchange capacity of the synthesized amidoxime resins were investigated before and after alkaline treatment. The results showed that the anion exchange capacity decreased with an increase in the amount of MA while alkaline treatment had no significant effect. Also, the cation exchange capacity increased with an increase in the amount of hydrophilic agent and reached a maximum point. The sorption equilibrium was achieved relatively fast within 40 min, and the resin exhibited affinity towards lead (II), copper (II) and in particular U(VI), and the order of adsorption affinity were UO 2 2 + > Pb2+ ≫ Co2+ > Cu2+ ≫ Cd2+. The adsorption of uranium was directly depended up on the pH value. Furthermore, the macroreticular chelating resin, containing amidoxime group had higher adsorption of uranium (VI) than other metal ions studied. Finally, the alkaline treatment enhanced the potential for much faster adsorption and the highly porous chelating resin provided a more favorable pore structure for the rapid rate of diffusion of metal ions.

Removal of heavy metals from aqueous media by cation exchange nonwoven PET coated with β-cyclodextrin-polycarboxylic moieties

Abstract: The purpose of this paper was to evaluate the capacity of new cationic exchange textiles (CET) to uptake four heavy metals (Pb 2+ , Cd 2+ , Zn 2+ , Ni 2+ ) from water. The CETs are nonwoven PET coated with a copolymer (polyester) of β-cyclodextrin and different polycarboxylic acids: citric acid (CTR), 1,2,3,4–butanetetracarboxylic acid (BTCA), polyacrylic acid (PAA M w = 2000 g/mol). The efficiencies of these three CETs (either on carboxylic or carboxylate forms) and the uncoated (βCD-citric acid) copolymer were established with respect to different experimental conditions (time, pH, metal mixture). Finally, two CETs (those coated with CTR or BTCA) gave the best results for depollution applications in terms of the metal adsorption/cost ratio.

Selective adsorption of tea polyphenols from aqueous solution of the mixture with caffeine on macroporous crosslinked poly(N-vinyl-2-pyrrolidinone)

Abstract: A macroporous polymeric adsorbent with moderate hydrophobic matrix and hydrogen-bonding moieties was prepared by free radical suspension copolymerization of N -vinyl-2-pyrrolidinone, ethylene glycol dimethacrylate and triallyl isocyanurate. SEM image and N 2 adsorption–desorption isotherm measurements of the resulting resin, defined as PVP–DEGMA–TAIC, show that the average pore diameter and specific surface area are ∼400 nm and 114 m 2 /g, respectively. The adsorption behavior of tea polyphenols and caffeine on PVP–DEGMA–TAIC resin indicates that the adsorption of tea polyphenols is driven by combined action of hydrophobic interaction and hydrogen bonding, while the adsorption of caffeine is driven by only hydrophobic interaction. The adsorption from an aqueous solution of a mixture of tea polyphenols and caffeine (initial weight concentration ratio was ∼5/1) on PVP–DEGMA–TAIC shows that the adsorption capacities for tea polyphenols and caffeine were 98 mg/g and 1–2 mg/g with removal percentages of 93% and 8%, respectively. The product eluted with ethanol contains ∼98% tea polyphenols and ∼2% caffeine. These results indicate that selective adsorption of polyphenols from the mixture with caffeine on PVP–DEGMA–TAIC resin was excellent.

Amphiphilic cellulose: Surface activity and aqueous self-assembly into nano-sized polymeric micelles

Abstract: The aim of the present study was to design amphiphilic cellulose that can self-assemble into polymeric vesicle or as nontoxic surfactants. Sulfate was firstly introduced as hydrophilic groups, then the hydrophobic groups for three cellulose derivatives. Effects of the hydrophobic length on the surface tension and critical aggregate concentration (cac) were investigated by the conventional Wilhelmy plate method. Results showed that the cac value decreased from 0.28 to 0.08 wt% and the corresponding surface tension increased from 44 to 55 mN/m when the hydrophobic chain length changed from C8 to C18. The aqueous self-assembly of the modified polymer was investigated using transmission electron microscopy (TEM) and dynamic laser scattering (DLS). Results showed that three cellulose derivatives were capable of forming polymeric micelles in water with an average particle diameter ranging from 20 to 67 nm. And the diameter of the nano-micelles was proportional to the length of hydrophobic chain under the experimental conditions. These amphiphilic polymers showed more remarkable shear shinning rheological behavior as expected since higher shear rates lead to disruptions of hydrophobic associations. These data suggest that the amphiphilic cellulose derivative may form nano-micelles and might find use as surfactant or a potential drug carrier. 2008 Elsevier Ltd. All rights reserved.

New perfluoropolyether urethane methacrylates as surface modifiers: Effect of molecular weight and end group structure

Abstract: The paper reports the synthesis and characterisation of two new series of perfluoropolyether methacrylates, characterised by increasing MW and different end groups. They were used as co-monomers in the polymerisation of Bisphenol A bis-ethylether diacrylate via a UV-curing process. Notwithstanding their very low concentration (<1% w/w), the fluorinated monomers caused a dramatic change of the surface properties of the copolymeric networks. They showed an excellent surface activity evidencing hydrophobic and lipophobic properties which could be modulated either by changing the MW and the end group of the fluorinated co-monomer or by controlling the curing process, in particular the time elapsing between the coating of the co-monomers mixtures onto the substrate and the irradiation of the systems.

Kinetic study of acid red “dye” removal by activated carbon and hyper-cross-linked polymeric sorbents Macronet Hypersol MN200 and MN300

Abstract: The search for suitable sorbents for persistent organic pollutants (like dyes) removal from aqueous solutions has prompted the evaluation of polymeric resins incorporating new properties that solve many of the existing problems when using granular activated carbon (GAC). A new type of non-functionalized macroporous hyper-cross-linked polymers Hypersol Macronet (MN200 and MN300) has been evaluated and kinetics measurements on the extraction of azo dye (Acid red 14) were made. Analyses of the respective batch rate data with two kinetic models, the homogenous particle diffusion model (HPDM) and the shell progressive model (SPM) were carried out. Sorbent phase was confirmed as the rate-determining step of the dye sorption process. Effective particle diffusion coefficients ( D eff ) were determined from the rate data proposed by both models. The D eff values from both HPMD and SPM equations varied from 5 × 10 −13 to 4 × 10 −16 m 2 s −1 . Weber and Morris intra-particle diffusion model showed a double contribution of the surface and pore diffusivities to the sorption process. Pore and surface diffusivities were calculated using a heterogeneous model. Hyper-cross-linked polymers reported a double contribution (pore and surface) to the overall diffusion process meanwhile GAC coefficients indicate a surface diffusion as the controlling mechanism.

Synthesis and characterization of poly(dimethylsiloxane)-block-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) diblock copolymers with low surface energy prepared by atom transfer radical polymerization

Abstract: Well-defined poly(dimethylsiloxane)-block-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) (PDMS-b-PHFBMA) diblock copolymers are synthesized via atom transfer radical polymerization (ATRP). The chemical composition and structure of the copolymers are characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Gel permeation chromatography (GPC) is also used to study the molecular weight distributions of the PDMS-b-PHFBMA diblock copolymers. The microstructure of the resulting copolymers is investigated by transmission electron microscopy (TEM). The results of TEM show that the diblock copolymers are microphase-separated if the bulk contains enough PHFBMA segments. The effect of fluorine content on the surface energy and the bulk structure is investigated by static water contact angle. Surface energy of PDMS-b-PHFBMA films is indirectly obtained from contact angle.

Catalytic activity of polymer anchored N,N′-bis (o-hydroxy acetophenone) ethylene diamine Schiff base complexes of Fe(III), Cu(II) and Zn(II) ions in oxidation of phenol

Abstract: N,N′-bis (o-hydroxy acetophenone) ethylene diamine Schiff base (HPED) was synthesized to prepare unsupported and polymer supported complexes of iron(III), copper(II) and zinc(II) ions. To immobilize HPED Schiff base on polymer support, first of all N,N′-bis (4-amono-o-hydroxy acetophenone) ethylene diamine Schiff base (AHPED) was synthesized by nitrosation and reduction of HPED Schiff and then reacted with cross-linked chloromethylated polystyrene beads in methanol. The anchoring of HPED Schiff base on polymer beads was 86.21 wt% (2.313 mmol g−1). HPED Schiff base anchored polymer beads were loaded with iron(III), copper(II) and zinc(II) ions, which showed 85.0% (1.96 mmol), 83.0% (1.91 mmol) and 78.0% (1.81 mmol) efficiency for complexation for these metal ions. The unsupported and supported metal complexes were characterized by UV, IR and magnetic measurements, which showed octahedral geometry for iron(III), square planar for copper(II) and tetrahedral for zinc(II) ions complexes. Complexation of metal ions has increased thermal stability of HPED Schiff base. The effect of polymer support on catalytic activity of metal complexes was determined by studying the oxidation of phenol under different experimental conditions in presence of hydrogen peroxide as oxidant. The iron(III) ions complexes showed high activity in comparison to copper(II) and zinc(II) ions complexes. The turn over number (TON) for phenol was high with polymer supported metal complexes than unsupported complexes.