Sharif Digital Repository

Deep wells suffer from the instability and disintegration of natural polymers and other commonly used additives under high pressure and high temperature condition. As a result, serious problems such as hydraulic loss, stuck pipe, and high torque and drag are expected to take place which leads to a dramatic increase in cost and time. This study presents the functionality of a novel synthetic based acrylamide-styrene copolymer (SBASC) as a supersede additive for water-based drilling mud. First, the SBASC was synthesized using an emulsion polymerization process and its particle morphological and polymer chain structural properties were determined by Field Emission Scanning Electron Microscopy... 

In this work, a novel method to synthesis of an acrylic superabsorbent hydrogel was reported. In the two stage hydrogel synthesis, first copolymerization reaction of acrylonitrile (AN) and acrylamide (AM) monomers using ammonium persulfate (APS) as a free radical initiator was performed. In the second stage, the resulted copolymer was hydrolyzed to produce carboxamide and carboxylate groups followed by in situ crosslinking of the polyacrylonitrile chains. The results from FTIR spectroscopy and the dark red-yellow color change show that the copolymerization, alkaline hydrolysis and crosslinking reactions have been do take place. Scanning electron microscopy (SEM) verifies that the synthesized... 

The incorporation of modified β-cyclodextrin (β-CD) into a poly(N-isopropylacrylamide) (PNIPAAm)/chitosan (PNCS) nanohydrogel was studied. β-CD was functionalized with acrylic groups, with different numbers of vinyl bonds added per β-CD molecule. The surfactant-free dispersion polymerization (SFDP) semi-batch method was used to synthesize the nanohydrogel. Increasing the number of vinyl groups per β-CDAC (β-CD acrylate) molecule induced the formation of smaller nanogels with diameters ranging from 142 to 68 nm. The cyclodextrin-modified dual-responsive nanogels obtained presented an LCST (lower critical solution temperature) in aqueous medium at around 31 C. The incorporation of β-CDAC into... 

Inclusion of nano-clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano-clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydro-gels based on kappa-carrageenan were synthesized using sodium montmorillonite as nano-clay. Acrylamide and meth-ylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium... 

Gelcasting is a novel forming method in fabricating complex three dimensional ceramic parts, and has many parameters and characteristics required to be specified. Up to now, few articles have been published on determination of the idle time of gelation precisely. In this work the chemorheology of gelation in aqueous solution of acrylamide and N, N′ methylenebisacrylamide monomer, and zirconia (PSZ) suspensions of this solution was investigated. As the viscosity of gel system increases abruptly in gelation point, idle time can be determined precisely by measurement of viscosity against time. Idle time can also be determined through temperature measurement against time since the reaction of... 

In this research a novel controlled anticancer drug delivery system with dual pH and thermal responses was designed based on magnetic mesoporous silica nanoparticles that were anchored by β-cyclodextrin and coated by poly(N-isopropylacrylamide) (PNIPAM). Results demonstrated that the behavior of doxorubicin (anticancer drug) release depended on pH and temperature conditions. At endosomal pH (pH 5.5) the amount of drug release enhanced because the cap was removed from the pores. Furthermore, PNIPAM shell collapsed above the lower critical solution temperature and the releasing of drug increased. Thus, this nanocarrier would have the potential to be applied in the tumor therapy. © 2017 Taylor... 

The influx of solid or liquid particles of drilling mud into the pores of rock or mud loss phenomenon and clay swelling can sometimes lead to severe productive formation damage and cause to wettability alterations of reservoir rock from hydrophilic to oleophilic. Therefore, designing an appropriate fluid that is compatible with formation fluids and could reduce reservoir damage and increase the productivity of wells is very important. The two main mechanisms of surfactants are reduction of the surface tension and wettability alteration of rock reservoir that are effective in taking the oil. Regarding the importance of the wettability in reservoir productivity, this article is aimed to study... 

In this report, the synthesis of a novel superabsorbent hydrogel via γ-irradiation graft copolymerization of acrylamide onto sodium alginate and kappa-carrageenan hybrid backbones in a homogeneous solution is described. The Taguchi method was used as a powerful experimental design tool for synthesis optimization. A series of superabsorbent hydrogels was synthesized by proposed conditions of Qualitek-4 software. Considering the results of nine trials according to analysis of variance, optimum conditions were proposed. The swelling behavior of optimum superabsorbent hydrogels was studied in various solutions, with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in... 

Temperature-sensitive hydrogels based on N-t-butylacrylamide (TBA), acrylamide (AAm), and sodium alginate were prepared by free radical polymerization method. Methylenebisacrylamide (MBA) and amonium persulfate (APS) were applied as water soluble crosslinker and initiator, respectively. The chemical structure of the hydrogels was confirmed by FT-IR spectroscopy and thermogravimetric analysis (TCA) methods. Morphology of the samples was examined by scanning electron microscopy (SEM). By changing the initial TBA/AAm mole ratios, hydrogels with different swelling properties were obtained. The rate parameters were found to be 2.0, 2.4, and 3.5 min for the superabsorbents with AAm/TBA weight... 

A tri-layered nanofibrous hydrogel thin film with temperature sensitivity is introduced as a new controlled drug release system to treat breast cancer. A simultaneous heat generation with the tunable release of dual drugs is observed in response to visible light radiation. A tri-layered nanofibrous sheet was fabricated through sequential electrospinning the blends of Au@Chit@DOX-loaded poly(N-isopropylacrylamide-co-N-methylol acrylamide) (poly (NIPAAm-co-NMA)) and Curcumin-loaded poly (vinyl alcohol) (Cu-loaded PVA), where the Cu-loaded PVA nanofibers (NFs) are sandwiched between two layers of Au@Chit@DOX-loaded poly (NIPAAm-co-NMA) NFs. After thermal crosslinking of the tri-layered... 

In this work Halloysite nanotubes were used to synthesis a series of modified acrylamide/Quince seeds-based hydrogels (Poly (AAm-co-QS)/Haln). The as-prepared Poly (AAm-co-QS)/Haln hydrogels displayed improved performance as adsorbent in elimination of methylene blue (MB) from aqueous solution. The structures of the prepared Poly (AAm-co-QS)/Haln hydrogels were identified by XRD, FT-IR, FE-SEM, BET, TGA and EDX. Effect of pH value on the swelling behavior and dye adsorption performance of as-prepared hydrogels was explored. The adsorption MB results suggested that the adsorption kinetics fitted the pseudo-second-order model. The adsorption experiments at various pH condition indicated that... 

Adsorption of Cr (VI) from aqueous solution was studied using a continuous fixed bed column which is packed with a new micro-porous composite particle developed in this study. This composite particle is composed of silica porous particle in which acrylamide is polymerized within the pore regions of the silica particles. The composite particle was supposed to maintain the mechanical properties of polyacrylamide as efficient absorbent to serve appropriately in the continuous processes. In order to enhance the adsorption capacity of the composite particle, it was modified with ethylenediamine. Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR) and... 

ZnO nanoparticles have been prepared successfully by hydrogel decomposition method (HDM). Synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), fourier transforms infrared spectroscopy (FTIR), and transition electron microscopy (TEM) techniques. Narrow distribution of sizes with a 20-30 nm diameter and regular distribution of ZnO nanoparticles are attributed to the application of poly(acrylic acid-co-acrylamide) grafted chitosan hydrogel as coating agent. The results show that the polymer thermal decomposition technique is a perfect method for the synthesis of ZnO nano particles  

The synthesis of a novel superabsorbent hydrogel with natural hybrid backbone via graft copolymerization of acrylamide (AAm) onto kappa-carrageenan (kC, as a polysaccharide) and gelatin (as a protein) under classic thermal conditions is described. The Taguchi method as a strong experimental design tool was used for synthesis optimization. A series of hydrogels were synthesized by proposed conditions of Qualitek-4 Software. Considering the results of 9 trials according to analysis of variance (ANOVA), optimum conditions were proposed. The swelling behavior of optimum hydrogel was measured in various solutions with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in... 

The influx of solid or liquid particles of drilling mud into the pores of rock or mud loss phenomenon and clay swelling can sometimes lead to severe productive formation damage and cause to wettability alterations of reservoir rock from hydrophilic to oleophilic. Therefore, designing an appropriate fluid that is compatible with formation fluids and could reduce reservoir damage and increase the productivity of wells is very important. The two main mechanisms of surfactants are reduction of the surface tension and wettability alteration of rock reservoir that are effective in taking the oil. Regarding the importance of the wettability in reservoir productivity, this article is aimed to study... 

Preformed particle gels (PPGs) in solutions have been widely used to suppress excess water production in mature oil reservoirs and, in turn, to improve the amount of oil recovery in brown oil fields. In this study, PPG solutions were meticulously formulated and synthesized in order to be utilized in harsh environments in terms of pressure, temperature, pH, and salinity from a free radical polymerization process. In this work, nanosilica gel at different weight percentages was added to improve the mechanical and thermal stability properties of the PPG at harsh condition: high pressure, temperature, and strain. Moreover, the effects of nanosilica gel at various concentrations, ranging from 0.0... 

The objective of this work is to develop a new Preformed Particle Gel (PPG) suspension to enhance oil production and monitor water production in a porous medium on micromodel scale. To achieve the above goal, the following synthetic method was used. At the outset, the PPG samples were synthesized with polyethylene amine (PEI) as a crosslinker, 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AAPH) as initiator and acrylamide (AM) and 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) monomers to improve the strength properties of PPGs by the radical polymerization method. Also, to characterize the micro and macro structural the samples, the scanning electron microscopy (SEM),... 

In the present work, an amperometric inhibition biosensor for the determination of sulfide has been fabricated by immobilizing Coprinus cinereus peroxidase (CIP) on the surface of screen printed electrode (SPE). Chitosan/acrylamide was applied for immobilization of peroxidase on the working electrode. The amperometric measurement was performed at an applied potential of -150. mV versus Ag/AgCl with a scan rate of 100. mV in the presence of hydroquinone as electron mediator and 0.1. M phosphate buffer solution of pH 6.5. The variables influencing the performance of sensor including the amount of substrate, mediator concentration and electrolyte pH were optimized. The determination of sulfide...