Sharif Digital Repository

Synthesis and swelling behavior of a new superabsorbent hydrogel based on natural salep grafted with polyacrylamide is described. The new superabsorbent hydrogel biopolymer was synthesized via radical crosslinking and graft copolymerization of acrylamide monomer onto salep backbones. Regarding to the water absorption of hydrogel, the best synthesis condition is reported. FTIR spectroscopy and thermogravimetric analysis were used to confirm the structure of the final product and a mechanism for superabsorbent hydrogel formation was also suggested. After preparing the desired hydrogels based on optimum condition, several factors affecting the swelling behavior of hydrogel including pH of... 

Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the... 

Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous... 

Chitosan was modified with polyacrylonitrile (PAN) through ceric-initiated graft copolymerization. The chitosan-g-PAN product was saponified using sodium hydroxide aqueous solution to prepare a novel superabsorbent hydrogel, H-chitoPAN. Duration of completing the saponification reaction as well as the water absorbency capacity of the hydrogel was decreased with increasing the alkaline concentration. Either chitosan-g-PAN or H-chitoPAN was characterized by FTIR spectroscopy and DSC, TGA, and DTG thermal methods. According to FTIR, all the nitrile groups were converted to carboxylate and carboxamide groups. Both modified chitosans exhibited enhanced thermal stability over chitosan. The... 

Various natural and modified polysaccharides (i.e. arabic gum, tragacanth gum, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) were modified using ceric-initiated graft polymerization of acrylonitrile under inert atmosphere. Grafting was confirmed using spectral (FT-IR) proofs. The grafting parameters were determined by conventional methods. Thermal characteristics of the homopolymer-free copolymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as the activation energy of the major decomposition stages were... 

Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a... 

Carboxymethylcellulose sodium salt (CMC) was doubly modified to prepare a novel poly(acrylamidoxime) chelating resin. Acrylonitrile was firstly graft polymerized onto CMC using cerium ammonium nitrate as an initiator. The polyacrylonitrile (PAN) grafted CMC was then amidoximized via treatment with hydroxylamine to prepare the ion exchange resin. The sorption capacity of the resin towards bivalent metal ions was evaluated while varying the pH, the loading of the PAN and the initial metal ion concentration. The adsorption kinetics were investigated for the cupric ion. The chelating resin exhibited very high metal sorption capacity in comparison with either synthetic or polysaccharide-based... 

A novel kappa-carrageenan (C)-based superabsorbing hydrogel was synthesized through graft copolymerization of acrylamide (AAm) onto a C substrate in the presence of a crosslinking agent. The crosslinked C-poly(AAm) polymer graft was partially hydrolyzed in alkaline medium to yield a superabsorbent resin, H-carragPAM. The resin structure was confirmed using FTIR spectroscopy. The variables of graft copolymerization (monomer, initiator, polysaccharide and crosslinker concentration, reaction temperature and time as well as stirrer speed) that affected on the ultimate water-swelling capacity were optimized. The time-temperature variation of the copolymerization was investigated in terms of the... 

The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two... 

The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the... 

Magnetic Fe3O4@SiO2 starch-graft-poly(acrylic acid) (SPAA) nanocomposite hydrogels were prepared and used as absorbents for removal of crystal violet from aqueous solutions. Dynamic swelling, effect of contact time, absorption kinetics and nanocomposite hydrogel mass for removal of crystal violet dyes from aqueous solutions were studied. Fourier transform infrared spectroscopy, scanning electron microscopy and vibrating sample magnetometer measurements were used for the characterization of the nanocomposite hydrogels. The nanocomposite hydrogels had high magnetic sensitivity under an external magnetic field, which allowed their magnetic separation from water, thus avoiding secondary... 

A new cationic flocculant was synthesized by graft copolymerization of acrylamide (AM) and 3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) onto salep using free radical polymerization initiated by ammonium persulfate (APS) to produce cationic salep [S-g-P(AM-co-MAPTAC)]. Reaction parameters (monomers/salep ratio, concentration of reactants, MAPTAC/AM ratio, and APS) were optimized using a full factorial experimental design to obtain the highest settling rate for cement suspensions. The best performing product was characterized by gel permeation chromatography (GPC), FTIR, 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The resulted cationic flocculant may be... 

Nanofiber membranes were fabricated by electrospinning poly(vinylidene fluoride). The electrospun nanofiber membranes were further modified by grafting of acrylic acid (AA) and methacrylic acid (MAA) over the surfaces of the membranes. Plasma AA graft was attempted only, and the results indicated the partial membrane pore filling with grafted AA. For MAA grafting, chemically induced polymerization using benzoyl peroxide and hydrogen peroxide was attempted. The combination of plasma and chemically induced MAA graft polymerization was also attempted. The membranes were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and static contact angle (SCA)... 

Synthesis of dextran-graft-poly(hydroxyethyl methacrylate) gels as a new fluoride biosorbent was considered in this work. For this propose, the Taguchi experimental design method was used for optimizing the synthetic conditions of the gels to reach high level of fluoride absorbency. The effects of three main parameters including concentrations of monomer (hydroxyethyl methacrylate), crosslinking agent (ethylene glycol dimethacrylate), and initiator (ammonium persulfate) on the final properties of the prepared gels were investigated. The proposed mechanism for grafting and chemically crosslinking reactions was proved with equilibrium water absorption, Fourier-transformed infrared, scanning... 

This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, 1H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and 1H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and... 

Salep phosphate modified biopolymers with different phosphate contents were prepared via reacting salep (a multi-component polysaccharide obtained from dried tubers of certain natural terrestrial orchids) with a solution of primary and secondary sodium phosphates under basic conditions in a semidry process. Structural characterization of salep phosphates were carried out by 31P NMR, FT-IR spectra and TGA curves. Determination of the phosphate content in samples was done by a standard spectrophotometric method. Then, novel (salep phosphate)-based hydrogels were synthesized by graft copolymerization of acrylic acid (AA) monomer onto salep phosphate backbones. Effect of the phosphate contents... 

A novel nano-porous hydrogel (NPH) was synthesized via graft copolymerization of sodium acrylate (Na-AA) and acrylamide (AAm) onto salep backbones and its application as a carrier matrix for oral delivery of tetracycline hydrochloride (TH) was investigated. The Taguchi method as a strong experimental design tool was used for synthesis optimization. The swelling behavior of optimum hydrogel was measured in various media. The hydrogel formation was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetrical analysis (TGA). The study of the surface morphology of the hydrogels using SEM and AFM showed a nanoporous (average pore size: 180. nm) structure for the sample... 

The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two... 

Novel high capacity swelling nanoporous hydrogel (NPH) was synthesized via graft copolymerization of acrylamide (AAm) onto kappa-carrageenan (kC, as a polysaccharide) and gelatin (as a protein) hybrid backbone, after hydrolysis of this system. The Taguchi method as a strong experimental design tool was used for its optimized synthesis. The Taguchi method was applied for the experimental and standard 9 orthogonal array (OA) with four factors and three levels for each factor. A series of NPHs 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...