Sharif Digital Repository

Hydrogel hybrids were conveniently prepared from alkaline hydrolysis of chitosan-poly(acrylonitrile) mixture under highly practical conditions. The reaction of chitosan alkoxide anions with nitrile groups of poly(acrylonitrile) (PAN) forms crosslinking points and results in a three-dimensional network with superswelling ability in aqueous media. The hydrogel hybrid was identified using FTIR spectroscopy. The PAN content of the hydrolyzing feed affects proportionally the swelling capacity of the hydrogel hybrid. The swelling properties (capacity and rate) of the ampholytic hydrogel were investigated preliminarily. © 2005 Wiley Periodicals, Inc  

The Taguchi method, a robust experimental design, was used for the optimization of the synthesis of a novel biopolymer-based superabsorbent hydrogel, carrageenan-graft-poly(sodium acrylate). The Taguchi method was applied for the experiment and standard 16 orthogonal arrays with five factors and four levels for each factor were used. In the synthesis of the superabsorbent hydrogel, N,N′-methylene bisacrylamide (MBA) was used as crosslinker, ammonium persulfate as initiator, and acrylic acid as monomer. Neutralization percent and reaction temperature were used as important factors. The analysis of variance results showed that the most important factor in this synthesis was MBA concentration.... 

Fast-swelling highly porous superabsorbent hydrogels were synthesized through a rapid radical polymerization under normal atmospheric conditions. To synthesize a biopolymer-based superabsorbent hydrogel, 2-hydroxyethyl acrylate (HEA) and sodium acrylate (AANa) were grafted on the starch backbone in an aqueous solution. The graft copolymerization reaction was carried out in the presence of ammonium persulfate (APS) as an initiator and N, N′-methylenebisacrylamide (MBA) as a cross-linker in a homogeneous medium. The chemical structure of the hydrogels was confirmed by FT-IR spectroscopy and thermogravimetric analysis (TGA). The morphology of the samples was examined by scanning electron... 

Novel types of highly swelling hydrogels were prepared by grafting crosslinked polyacrylic acid-co-poly-2-acrylamido-2-methylpropanesulfonic acid (PAA-co-PAMPS) chains onto κ-carrageenan through a free radical polymerization method. Here, we propose a mechanism for κ-carrageenan-g-PAA-co-PAMPS formation and confirm the hydrogel structure using FTIR spectroscopy. The effect of grafting variables (i.e. concentration of methylenebisacrylamide (MBA), acrylic acid/-2-acrylamido-2-methylpropanesulfonic acid (AA/AMPS) weight ratio, ammonium persulfate (APS), κ-carrageenan, neutralization percent and reaction temperature) were systematically optimized to achieve a hydrogel with a maximum swelling... 

In the present paper, a novel superabsorbent hydrogel composite based on gelatin have been prepared via graft copolymerization of acrylic acid (AA) in the presence of kaolin powder using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. Certain variables of the graft copolymerization (i.e., the monomer, the initiator, and the crosslinker concentration as well as kaolin/gelatin weight ratio) affected on the ultimate water-swelling capacity were optimized. The composite structure was confirmed using Fourier transform infrared (FTIR) spectroscopy. A new absorption band at 1728 cm1 in the composite spectrum confirmed kaolinorganic polymer... 

A novel superabsorbent composite based on chitosan was prepared by graft copolymerization of acrylic acid (AA) in the presence of kaolin powder using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The synthetic variables (i.e. AA, MBA, and APS concentration, and the kaolin amount) affecting the water absorbency of the resulting superabsorbent composite were studied. Evidence of grafting and kaolin interaction was obtained by comparing the FTIR spectra of the initial substrates with that of the superabsorbent composite. A new absorption band at 1722 cm-1 in the composite spectrum confirmed the kaolin-organic polymer linkage. The effect of... 

A semi-interpenetrating polymer network (semi-IPN) hydrogel composed of crosslinked chitosan and Polyacrylamide (PAAm) was prepared in the presence of formaldehyde as a crosslinker. The swelling capacity of hydrogel was shown to be affected by the crosslinker and the PAAm/chitosan ratio. The PAAm/chitosan semiIPN hydrogels are swelled at low pHs that attributed to both osmotic pressure and repulsion of -NH3+ groups on chitosan backbones. The swelling of hydrogel in acidic pHs showed that with increasing of chitosan content in the hydrogel, the swelling capacity was increased. But the swelling capacity of hydrogel in neutral pH is reversed, i.e. the higher the PAAm/chitosan ratio, the higher... 

The Taguchi method, a robust experimental design, was used for optimization of synthesis of a novel biopolymer-based superabsorbent hydrogel, kappa-carrageenan (K-C)-g-acrylic acid (AA)-co-2-acrylamido-2- methylpropanesulfonic acid (AMPS). The Taguchi method was applied for the experimental and standard 18 orthogonal arrays (OA) with seven factors and three levels for each factor. In the synthesis of the superabsorbent, N,N'-methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, monomer ratio (AA/AMPS), K-C concentration, Total Monomer, neutralization percent (NU), and reaction temperature were used as important factors. After analyzing with analysis of... 

In this work, the synthesis, characterization, and kinetic investigation of the free-radical polymerization of 4-acetylaminobenzene propenoic ester (ABPE) and 4-methylbenzene propenoic ester (MBPE) were studied. The kinetic behaviors of ABPE and MBPE in the polymerization initiated by azobisisobutyronitrile in dimethylformamide solutions at temperatures between 50 and 120°C were investigated, and experimental and theoretical conversion-time curves were compared. Both monomers showed a polymerization ceiling temperature (T c ). Tc was calculated with experimental values of k pk1/2 with a constant concentration of 0.7 mol/L for monomers. Tc was about 141 and 131 °C for ABPE and MBPE,... 

In this article, we report the first multiwalled carbon nanotube-polyelectrolyte gel containing vinylimidazolium-typed ionic liquid monomer as an absorbent of less-polar or nonpolar organic solvents. To prepare such MWCNT-polyelectrolyte gel, the modified MWCNTs with polymerizable vinyl groups on their surfaces were prepared and then underwent copolymerizations with dodecyl methacrylate and vinylimidazolium in the presence of AIBN as initiator, yielding a cross-linked polyelectrolyte. In order to estimate the compatibility between the solvents and the polymers, a series of vinylimidazolium-typed ionic liquid monomers ([Cnvim][X]) with different alkyl tail length (C6, C10 and C12) and counter... 

Gelcasting, as a ceramic forming technique, is getting worldwide attention, in that it can be used to make high-quality, complex-shaped ceramic parts with a wide range of powders. However, a model, which can appropriately describe the shear rate dependence behavior of the slurry in casting process simulation, is limited. Therefore, this study mainly sought to investigate the best model representing the behavior of as-prepared gelcast slurry. A premix solution was prepared with monomer/cross linker of AM/MBAM with ratio of 25:1. In this procedure, ammonium polyacrylate sodium (NHPANa) was used as the dispersant and the solid load included Al2O3/20 vol% ZrO2 powder mixture. Series of slurries... 

Novel class of polyelectrolyte gels based on the copolymer of vinylimidazolium-typed ionic liquid monomer and Dodecyl methacrylate was prepared by free radical polymerization. A small amount of 3-n-Dodecyl-1- vinylimidazolium tetrafluoroborate is incorporated into crosslinked polyacrylates to provide new lipophilic polyelectrolyte gels that evaluated for swelling in less-polar and nonpolar organic solvents. Their swelling degree becomes more than 50 times as much as their dried weights in some organic solvents. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated. The present... 

In this study, the inverse emulsion polymerization modeling of polyacrylamide with population balance equations (PBEs) was performed. The PBEs were derived on the basis of the zero-one kinetic model. The effects of the surfactant steric barrier and surfactant reaction with radicals, including monomeric radicals, on the radical entry rate into the particle were taken into account. In the modified model, the coagulation phenomenon was included through consideration of the effects of forces not included in the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory; these include hydration and steric forces in addition to DLVO forces. The effects of the surfactant and initiator concentrations on... 

The chemical modification of isotactic polypropylene was performed by the free-radical-promoted grafting of 1,1,1-trimethylolpropane trimethacrylate (TMPTMA) in the presence of dicumyl peroxide (DCP) as the initiator. The reaction was carried out both in a batch internal mixer and in a corotating twin-screw extruder; the effects of the peroxide and monomer concentrations on the extent of modification in terms of the grafting efficiency and polymer chain structure variations were investigated. The modified samples were characterized with Fourier transform infrared to determine the structure of the grafted groups and the degree of functionalization, with gel permeation chromatography and the... 

This study reports the importance of physicochemical characteristics of the core-shell structured polymer-coated Fe3O4 cluster@SiO2 nanocomposite particles for designing the biocatalysts used for transesterification of soybean oil. To demonstrate this issue, two different types of polymer molecules such as polyethylenimine (PEI) and polyacrylic acid (PAA) each with two different molecular weights are employed. The highest fatty acid methyl esters (FAMEs) synthesis yield values are achieved by the lipases immobilized onto the low- and high-molecular-weight PEI-coated particles as compared to those of the low- and high-molecular-weight PAA-coated particles (i.e., ∼64.8% and ∼73.1% versus... 

Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. In particular, adding nanoparticles to fluids may drastically benefit enhanced oil recovery (EOR) and improve well drilling, by changing the properties of the fluid, rocks wettability alteration, advanced drag reduction, strengthening the sand consolidation, reducing the interfacial tension and increasing the mobility of the capillary trapped oil. In this study, we focus on roles of clay nano-particles on polymer viscosity. Polymer-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemical components by adsorption on reservoir... 

In the present work, we report a chemically modified polyacrylamide/silica nanoporous composite adsorbent for the removal of reactive black 5 (RB5) azo dye from aqueous solutions. The composite adsorbent was synthesized in a packed bed and modified by ethylenediamine (EDA). The adsorbent was characterized by Fourier transformation infrared (FT-IR), thermogravimetric analysis (TGA), thermoporometry, Brunauer, Emmett and Teller (BET) method and scanning electron microscopy (SEM). Mechanical stability of the adsorbent was examined in a packed bed by following the back-pressure of the column. Pore diameter of the composite adsorbent in dry and wet states was estimated to be about 18.71 nm and... 

With the decline in oil discoveries over recent decades, it is believed that enhanced oil recovery (EOR) technologies will play a key role to meet energy demand in the coming years. Polymer flooding is used commonly worldwide as an EOR process. In this work, we propose the synthesis of protected polyacrylamide (PAM) nanoparticles (PPNs) with a hydrophobic polystyrene (PSt) shell by one-pot two-step inverse emulsion polymerization, in which the PSt shell was created by surface polymerization. The shell protects the active PAM chains from premature degradation caused by the harsh environment in the reservoirs, controls the release of the chains as rheological modifiers, and additionally, it...