Investigation of metal ion removal selectivity properties of the modified polyacrylamide hydrogels prepared by transamidation and Hofmann reactions

Modified crosslinked polyacrylamides having different functional groups prepared by transamidation reaction in aqueous and non-aqueous medium and by Hofmann reach. on were used as chelating agents for removal of Cu(II), Cd(II) and Pb(II) ions from aqueous solutions' at different pH values. Under non-competitive conditions, polymers adsorbed different amounts of metal ions, depending on their functional groups and swelling abilities. The metal ion adsorption capacities of polymers changed between 0.11 - 1.71 mmol/g polymer. Under competitive conditions, while the polymers having mainly secondary amine groups were highly selective for Cu(II) ions (99.4%), those having mainly secondary amide and carboxylate groups have shown high selectivity towards Pb(II) ions (99.5%). The selectivity towards Cu(II) ion decreased and Job(II) ion selectivity increased by the decrease of the pH of the solutions. The high initial adsorption rate (< 10 min) suggests that the adsorption occurs mainly on the polymer surface. A regeneration procedure by treatment with dilute HCl solution showed that the modified polymers could be used several times without loss of their adsorption capacities

A novel type of Si-containing poly(urethane-imide)s: synthesis, characterization and electrical properties

A novel type of a Si-containing poly(urethane-imide) (PUI) was prepared by two different methods. In the first method, Si-containing polyurethane (PU) prepolymer having isocyanate end groups was prepared by the reaction of diphenylsilanediol (DSiD) and toluene diisocyanate (TDI). Subsequently the PU prepolymer was reacted with pyromellitic dianhydride (PMDA) or benzophenonetetracarboxylic dianhydride (BTDA) in N-methyl pyrolidone (NMP) to form Si-containing modified polyimide directly. In the second method, PU prepolymer was reacted with diaminodiphenylether (DDE) or diaminodiphenylsulfone (DDS) in order to prepare an amine telechelic PU prepolymer. Finally, the PU prepolymer having diamine end groups was reacted with PMDA or BTDA to form a Si-containing modified polyimide. Cast films prepared by second method were thermally treated at 160 degrees C to give a series of clear, transparent PUI films. Thermogravimetric analysis indicated that the thermal degradation of PUI starts at 265 degrees C which is higher than degradation temperature of conventional PU, confirming that the introduction of imide groups improved the thermal stability of PU

Synthesis of silicone-acrylic-modified high-ortho novolac resin with enhanced thermal resistance and surface coating properties

In the present study, vinyltrimethoxysilane was used to modify high-ortho novolac resin (NR) to obtain a vinyl silicone-modified phenolic oligomer (Si-mod NR). Subsequently, this oligomer is polymerized with methyl methacrylate. The mid-products (NR and Si-mod NR) and synthesized silicone-modified phenolic/acrylic resin (Ac/Si-mod NR) were characterized by Fourier transform infrared spectroscopy, and thermal properties were investigated by using thermal gravimetric analysis and differential scanning calorimetry techniques. In addition, the surface coating properties, including drying, hardness, adhesion, impact resistance, gloss, acid, alkaline, water, and solvent resistance of the films prepared from these products, were comparatively investigated. The results showed that the modification reactions yield a novel resin (Ac/Si-mod NR), which can be easily used as a surface coating material with high thermal resistance, flexibility, and excellent film properties

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solution was investigated. The copolymers used were (1) cellulose-g-polyacrylic acid (cellulose-g-pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose-g-p(AA-NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of NN'-methylene bisacrylamide (NMBA); (3) cellulose-g-p(AA-AASO(3)H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2-acrylamido-2-methyl propane sulphonic acid (AASO(3)H) containing 10% (in mole) AASO(3)H; and (4) cellulose-g-pAASO(3)H obtained by grafting of AASO(3)H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose-g-pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g(copolymer). Although the metal removal rate of cellulose-g-p(AA-NMBA) copolymer was lower than that of cellulose-g-pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g(copolymer). Cellulose did not remove any ion under the same conditions. In addition, cellulose-g-pAASO(3)H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g(copolymer)). The presence of AASO(3)H in the graft chains of cellulose-g-p(AA-AASO(3)H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose-g-pAA. All types of cellulose copolymers were found to be selective for the removal of Pb2+ over Cu2+ and Cd2+. (C) 2003 Wiley Periodicals, Inc

Effects of the Starch Types and the Grafting Conditions on the In Vitro Mucoadhesiveness of the Starch-graft-Poly(Methacrylic Acid) Hydrogels

In the present study, grafting of poly(methacrylic acid) (PMAA) onto various types of starches (maize; rice; wheat; potato) is realized in the aqueous media for the first time using methacrylic acid as monomer and ammonium cerium-IV-nitrate as initiator system. The effects of the gelatinization pretreatment and the use of a crosslinker in the grafting reactions are investigated. The formation of the starch-graft-poly(methacrylic acid) (S-g-PMAA) is confirmed by Fourier transform infrared spectroscopy analysis. The grafting amounts (GA%) of the S-g-PMAAs are determined. The swelling and the erosion characteristics of the S-g-PMAAs are examined in deionized water and pH = 5 lactate buffer solution as an in vitro vaginal medium. Mechanical and in vitro mucoadhesiveness of the S-g-PMAAs are also investigated using ewe vaginal mucosa. The results demonstrate that the gelatinization pretreatment and crosslinking significantly affect the GA% values, swelling, erosion, mechanical, and mucoadhesive characteristics of the S-g-PMAAs depending on the types of starches. S-g-PMAAs with different mechanical and reasonable mucoadhesiveness can be obtained by manipulating the grafting conditions and using various types of starches. It is concluded that S-g-PMAAs could be appropriate candidates for applications as vaginal drug delivery systems

Study on novel exfoliated polyampholyte nanocomposite hydrogels based on acrylic monomers and Mg-Al-Cl layered double hydroxide: Synthesis and characterization

Novel exfoliated polyampholyte nanocomposite hydrogels (NH-LDHs) based on acrylic acid (AA), 2(diethylamino) ethyl methacrylate (2-DEAEMA), N,N-methylenebisacrylamide (NMBA) and layered double hydroxide (Mg-Al-CI LDH) were synthesized using an in situ free radical addition polymerization method in aqueous media. First, Mg-Al-CI LDH with a highly crystalline structure was prepared and characterized using FTIR, XRD, TGA and SEM analyses. The formation of NH-LDHs was confirmed by FTIR and XRD analyses. The morphological structure and select properties, such as the thermal, swelling and mechanical properties, of the NH-LDHs were also investigated. NH-LDHs have an exfoliated structure and smooth and nonporous surface morphologies. They can also be used as thermally stable nanocomposite hydrogels. The results revealed that adding a small amount of exfoliated Mg-Al-CI LDH could effectively increase the compressive modulus of the polyampholyte gels. When the Mg-Al-CILDH was incorporated into the polyampholyte hydrogel matrix, two synergic effects, additional co-crosslinking and additional hydrophilicity, occur in the swelling behaviors of the gels. All NH-LDHs are sensitive to pH, and they have zwitterion characteristics at pH 5.5. It was concluded that the NH-LDHs synthesized in this study might be used as alternative water absorbents in solutions with different pH. The diffusion of water into the NH-LDHs gel systems in deionized water at room temperature is assumed to be a non-Fickian behavior. (C) 2013 Elsevier B.V. All rights reserved

Simultaneous glycolysis and hydrolysis of polyethylene terephthalate and characterization of products by differential scanning calorimetry

Simultaneous glycolysis and neutral hydrolysis of waste polyethylene terephthalate (PET) has been carried out at 170 and 190 degreesC with constant amount of ethylene glycol (EG) and increasing amounts of water, in the presence of xylene. The organic solvent made it possible to employ very low amounts of reactants as well as application of lower temperatures and pressures in contrast with previous methods, yielding intermediates suitable for PET or other polymeric materials. These intermediates were characterized by acid value (AV), hydroxyl value (HV) determinations as well as by differential scanning calorimetry (DSC). A water soluble crystallizable fraction with high purity, consisting of mono 2-hydroxy ethyl ester of terephthalic acid (monohydroxyethyl terephthalate, MHT) monomer has been obtained with significant yield and its polymerization tendency has been compared with that of bis(2-hydroxy ethyl) terephthalate (BHET) by application of multiple heating/cooling cycles in DSC. (C) 2003 Elsevier Ltd. All rights reserved

pH sensitive functionalized hyperbranched polyester based nanoparticulate system for the receptor-mediated targeted cancer therapy

The aim of this study is to develop a novel folic acid conjugated, DL-lysine modified, PEGylated, the 3rd generation hyperbranched polymer (HBP-PEG-Lys-FA) for use in receptor-mediated therapy. 5-fluorouracil, model anti-cancer drug, loaded nanoparticles were found an average size of 177 nm with loading efficiency of 23.18%. In vitro drug release studies demonstrated that nanoparticles showed pH-dependent release. HBP-PEG-Lys-FA were efficiently taken up by HeLa cells and specificity of targeted nanoparticles to folate receptors of cells was proved. It was concluded that the HBP-PEG-Lys-FA nanoparticles can provide an advantage on delivering of the drug efficiently into the cytosol for cancer therapy

Preparation, characterization and dielectric properties of 4,4-diphenylmethane diisocyanate (MDI) based cross-linked polyimide films

Four different types of cross-linked polyimides based on 4,4-diphenylmethane diisocyanate (MDI) were prepared by the reaction of different types of conventional poly(amic acid) intermediates with MDI as a cross-linking agent. Subsequently, they were thermally imidized in order to obtain corresponding cross-linked polyimide structure. The results of FTIR-ATR showed that MDI can effectively react with carboxylic acid groups of PAA to form cross-linked polyimide films. TGA, FTIR-ATR and SEM analyses were carried out for characterization of cross-linked polyimide (CPI) films. Moreover, the electrical properties such as dielectric breakdown strength, dielectric constant, I-V characteristics and loss factor of MDI based cross-linked polyimides have been checked. In addition, some physical properties such as water uptake, adhesion, hardness and solubility properties of the films were investigated

Electrical properties of conventional polyimide films: Effects of chemical structure and water uptake

A series of conventional polyimide (CPI) films, based on pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylicdianhydride (BTDA), were prepared by a two step process, and their dielectrical constant dielectrical loss, and DC conduction behaviors were studied at different frequencies and voltages. Their dielectrical breakdown voltage, water uptake, and solubility properties were also investigated. The effects of chemical structure and water uptake on the electrical properties of the films are discussed in detail. The dielectric constants of the CPI films vary between 2.93 and 3.72 at 1 MHz frequency and they are in the following decreasing order: BTDA-DDS > BTDA-DDE > PMDA-DDS > PMDA-DDE. The structure and thermal and oxidative stability of films were analyzed by FTIR-ATR and TGA, respectively. The results showed that all CPI films have good insulating properties, such as high dielectric breakdown voltage, low dielectric constant with stability for long period of frequency, and low leakage density. Our results concerning electrical properties also suggest that electron hopping is responsible for AC conduction and Poole-Frenkel mechanism is predominant for DC conduction of all CPI films. (c) 2006 Wiley Periodicals, Inc