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    Modified carrageenan. 5. Preparation, swelling behavior, salt- and pH-sensitivity of partially hydrolyzed crosslinked carrageenan-graft-polymethacrylamide superabsorbent hydrogel [electronic resource]

    , Article Polymers for Advanced Technologies ; Volume 15, Issue 11, pages 645–653, November 2004 Pourjavadi, A. (Ali) ; Sadeghi, M ; Hosseinzadeh, H
    Abstract
    The polysaccharide, kappa-carrageenan (κC) was chemically modified to achieve a novel superabsorbent hydrogel via graft copolymerization of methacrylamide (MAM) onto the substrate followed by alkaline hydrolysis. Ammonium persulfate (APS) and N,N′-methylene bisacrylamide (MBA) were used as a free-radical initiator and a crosslinker, respectively. The saponification reaction was carried out using sodium hydroxide aqueous solution. Either κC-g-PMAM or hydrolyzed κC-g-PMAM (PMAM: polymethacrylamide) was characterized by FT-IR spectroscopy. The effect of grafting variables (i.e. concentration of MBA, MAM, and APS) and alkaline hydrolysis conditions (i.e. NaOH concentration, hydrolysis time and... 

    Modified carrageenan. 5. Preparation, swelling behavior, salt- and pH-sensitivity of partially hydrolyzed crosslinked carrageenan-graft-polymethacrylamide superabsorbent hydrogel

    , Article Polymers for Advanced Technologies ; Volume 15, Issue 11 , 2004 , Pages 645-653 ; 10427147 (ISSN) Pourjavadi, A ; Sadeghi, M ; Hosseinzadeh, H ; Sharif University of Technology
    2004
    Abstract
    The polysaccharide, kappa-carrageenan (kC) was chemically modified to achieve a novel superabsorbent hydrogel via graft copolymerization of methacrylamide (MAM) onto the substrate followed by alkaline hydrolysis. Ammonium persulfate (APS) and N,N'-methylene bisacrylamide (MBA) were used as a free-radical initiator and a crosslinker, respectively. The saponification reaction was carried out using sodium hydroxide aqueous solution. Either kC-g-PMAM or hydrolyzed kC-g-PMAM (PMAM: polymethacrylamide) was characterized by FT-IR spectroscopy. The effect of grafting variables (i.e.concentration of MBA, MAM, and APS) and alkaline hydrolysis conditions (i.e. NaOH concentration, hydrolysis time and... 

    Modified Chitosan. 2. H-chitoPAN, a novel pH-responsive superabsorbent hydrogel [electronic resource]

    , Article Journal of Applied Polymer Science ; Volume 90, Issue 11, pages 3115–3121, 9 December 2003 Pourjavadi, A. (Ali) ; Mahdavinia, G. R ; Zohuriaan-Mehr, M. J
    Abstract
    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... 

    Modified Chitosan. 3. Superabsorbency, Salt- and pH-Sensivity of Smart Ampholitic hydrogels from Chitosan-g-PAN [electronic resource]

    , Article Polymers for Advanced Technologies ; Volume 15, Issue 4, pages 173–180, April 2004 Mahdavinia, G. R. (Golam Reza) ; Zohuriaan-Mehr, M. J ; Pourjavadi, M. J
    Abstract
    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... 

    Modified carrageenan. 1. H-carragPAM, a novel biopolymer-based superabsorbent hydrogel [electronic resource]

    , Article Journal of Bioactive and Compatible Polymers ; September 2005 Vol. 20 no. 5 475-490 Hosseinzadeh, H. (Hossein) ; Pourjavadi, A ; Mahdavinia, G. R ; Zohuriaan-Mehr, , M. J
    Abstract
    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... 

    Modified carrageenan. 4. Synthesis and swelling behavior of crosslinked kappa C-g-AMPS superabsorbent hydrogel with antisalt and pH-responsiveness properties [electronic resource]

    , Article Journal of Applied Polymer Science ; Vol.98, No.1, 255-263, 2005 Pourjavadi, A. (Ali) ; Hosseinzadeh, H ; Mazidi, R
    Abstract
    To synthesize a novel biopolymer-based superabsorbent hydrogel, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was grafted onto kappa-carrageenan (KC) backbones. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator, N,N,N',N'-tetramethyl ethylenediamine (TMEDA) as an accelerator, and N,N'-methylene bisacrylamide (MBA) as a crosslinker. A proposed mechanism for KC-g-AMPS formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The affecting variables on swelling capacity, i.e., the initiator, the crosslinker, and the monomer concentration, as well as reaction temperature,... 

    Partially hydrolyzed crosslinked alginate-graft-polymethacrylamide as a novel biopolymer-based superabsorbent hydrogel having pH-responsive Properties [electronic resource]

    , Article Macromolecular Research ; January 2005, Volume 13, Issue 1, pp 45-53 Pourjavadi, A. (Ali) ; Aminfazl, M. S ; Hosseinzadeh, H
    Abstract
    In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacrylamide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator andN,N′-methylenebisacrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g-PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-polymethacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the... 

    Batch equilibrium and kinetics studies of Cd (II) ion removal from aqueous solution using porous chitosan hydrogel beads

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 28, Issue 3 , 2009 , Pages 81-89 ; 10219986 (ISSN) Mohammad Beigi, S ; Babapoor, A ; Maghsoodi, V ; Mousavi, S. M ; Rajabi, N ; Sharif University of Technology
    Abstract
    In this study chitosan hydrogel beads with porosity ∼ 0.86 and diameter ∼ 2 ± 0.07 mm were prepared from 85 % deacetylated chitosan for removal of Cd2+ ions from aqueous solutions. Chitosan powder was dissolved into dilute acetic acid as solvent and formed into spherical beads using a phase inversion technique. The effect of temperature, initial concentration of Cd2+ ions, and the period of agitation were perused to achieve the best isotherm model. Freundlich model was better fitted than Langmuir model (R2 > 0.99 and R2> 0.93 respectively, at pH of 6.3, and shaker speed of 200 rpm), the constants of Langmuir and Freundlich models were calculated, which RL value and qmax (mg/g wet weight) at... 

    Novel synthesis route for preparation of porous nitrogen-doped carbons from lignocellulosic wastes for high performance supercapacitors

    , Article Journal of Alloys and Compounds ; Volume 827 , 2020 Pourjavadi, A ; Abdolmaleki, H ; Doroudian, M ; Hosseini, S. H ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Porous nitrogen-doped carbons derived from biomass wastes are considered as promising materials for energy storage devices. Herein, a novel and scalable synthesis route for preparation of these materials from sugarcane bagasse waste is demonstrated. The synthesis process includes a hydrogel intermediate in which delignified bagasse and polyacrylamide networks are interlaced in molecular scale and calcium acetate serves as a hard template within the polymeric chains. After pre-carbonization and chemical activation of the hydrogel, porous nitrogen-doped carbon with high surface area of 1834.3 m2 g−1 and considerable pore volume of 1.03 cm3 g−1 was obtained with nitrogen and oxygen contents of... 

    Modified carrageenan. 6. Crosslinked graft copolymer of methacrylic acid and kappa-carrageenan as a novel superabsorbent hydrogel with low salt- and high pH-sensitivity

    , Article Macromolecular Research ; Volume 13, Issue 6 , 2005 , Pages 483-490 ; 15985032 (ISSN) Pourjavadi, A ; Harzandi, A. M ; Hosseinzadeh, H ; Sharif University of Technology
    Polymer Society of Korea  2005
    Abstract
    A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan (κC), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for κC-g-polymethacrylic acid (κC-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were... 

    Modified chitosan III, superabsorbency, salt- and pH-sensitivity of smart ampholytic hydrogels from chitosan-g-PAN

    , Article Polymers for Advanced Technologies ; Volume 15, Issue 4 , 2004 , Pages 173-180 ; 10427147 (ISSN) Mahdavinia, G. R ; Zohuriaan Mehr, M. J ; Pourjavadi, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2004
    Abstract
    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... 

    Modified chitosan. II. H-chitoPAN, a novel pH-responsive superabsorbent hydrogel

    , Article Journal of Applied Polymer Science ; Volume 90, Issue 11 , 2003 , Pages 3115- ; 00218995 (ISSN) Pourjavadi, A ; Mahdavinia, G. R ; Zohuriaan Mehr, M. J ; Sharif University of Technology
    2003
    Abstract
    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... 

    Taguchi optimized synthesis of collagen-g-poly(acrylic acid)/kaolin composite superabsorbent hydrogel

    , Article European Polymer Journal ; Volume 44, Issue 4 , 2008 , Pages 1209-1216 ; 00143057 (ISSN) Pourjavadi, A ; Ayyari, M ; Amini Fazl, M. S ; Sharif University of Technology
    2008
    Abstract
    A novel biopolymer-based hydrogel composite was synthesized through chemical crosslinking by graft copolymerization of partially neutralized acrylic acid onto the hydrolyzed collagen. The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis based on the swelling capacity of the hydrogels. This method was applied for the experiments and standard L16 orthogonal array with five factors and four levels. In the synthesis of the composite superabsorbent, N,N′-methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, acrylic acid (AA) as monomer, neutralization percent (NU), and collagen/kaolin weight ratio were used as... 

    Swelling and mechanical behavior of nanoclay reinforced hydrogel: single network vs. full interpenetrating polymer network

    , Article Polymer Bulletin ; Volume 72, Issue 7 , March , 2015 , Pages 1663-1681 ; 01700839 (ISSN) Kheirabadi, M ; Bagheri, R ; Kabiri, K ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    Despite the various uses of hydrogels, one of their weaknesses is the poor gel strength. To overcome this restriction, the current study has focused on simultaneously employing an interpenetrating polymer network (IPN) structure and nanocomposite hydrogels. Through this approach, the influence of nanofiller in the single network and IPN hydrogel properties was also studied in detail. For this purpose, a novel full interpenetrating polymer network (IPN) hydrogel nanocomposite based on 2-acrylamido-2-methylpropane sulfonic acid (AMPS)/acrylic acid (AA)–sodium acrylate (AANa) was synthesized in two steps through a facile solution polymerization with incorporation of modified bentonite (MBE) as... 

    Adsorption characteristics of malachite green dye onto novel kappa-carrageenan-g-polyacrylic acid/TiO2-NH2 hydrogel nanocomposite

    , Article Journal of the Iranian Chemical Society ; Volume 11, Issue 4 , August 2014 , Pages 1057-1065 Pourjavadi, A ; Doulabi, M ; Doroudian, M ; Sharif University of Technology
    Abstract
    Batch adsorption experiments were carried out for the removal of malachite green (MG) cationic dye from aqueous solution using novel hydrogel nanocomposite that was prepared by graft copolymerization of acrylic acid (AA) onto kappa-carrageenan (κC) biopolymer in the presence of a crosslinking agent, a free radical initiator and aminosilica-functionalized TiO2 nanoparticles (κC-g-PAA/TiO2-NH2). The factors influencing adsorption capacity of the adsorbents such as initial pH value (pH0) of the dye solutions, TiO2-NH2 content (wt%), initial concentration of the dye, amount of adsorbents, and temperature were investigated. The adsorption capacity of hydrogel nanocomposite for MG was compared... 

    Gamma irradiation mediated synthesis of a new superabsorbent hydrogel network based on poly(acrylic acid) grafted onto salep

    , Article Journal of the Iranian Chemical Society ; Volume 7, Issue 3 , 2010 , Pages 652-662 ; 1735207X (ISSN) Rezanejade Bardajee, G ; Pourjavadi, A ; Soleyman, R ; Sheikh, N ; Sharif University of Technology
    2010
    Abstract
    A novel and smart biopolymer-based hydrogel was synthesized by graft copolymerization of acrylic acid onto the salep backbones. The new superabsorbent hydrogel was synthesized via simultaneous crosslinking and graft copolymerization of acrylic acid (AA) monomer onto salep backbones using radiochemical methods. In radiochemical methods, γ-rays as initiator, energy source and crosslinker are applied. In our experiments, the effects of reaction variables such as relative contents of salep and AA, as well as γ-rays total dose were examined. According to water absorbency of the entitled network, the best synthesis condition is reported. FTIR spectroscopy, SEM photograph and TGA analysis were used... 

    Porous Carrageenan-g-polyacrylamide/bentonite superabsorbent composites: swelling and dye adsorption behavior

    , Article Journal of Polymer Research ; Volume 23, Issue 3 , 2016 , Pages 1-10 ; 10229760 (ISSN) Pourjavadi, A ; Bassampour, Z ; Ghasemzadeh, H ; Nazari, M ; Zolghadr, L ; Hosseini, S. H ; Sharif University of Technology
    Springer Netherlands  2016
    Abstract
    A novel superabsorbent composite based on kappa-Carrageenan (κC) was prepared by graft copolymerization of acrylamide (AAm) onto κC in the presence of bentonite powder using methylenebisacrylamide (MBA) as a crosslinking agent, ammonium persulfate (APS) as an initiator, and sodium carbonate as a pore-forming agent. The swelling behavior in distilled water and in solutions with different pH values was investigated. The results indicated that with increasing carrageenan/bentonite weight ratio, the swelling capacity is increased but the gel content is decreased. The swelling rate of the hydrogels was improved by introducing sodium carbonate as pore-forming agent. The prepared superadsorbent... 

    In-situ formation and entrapment of Ag/AgCl photocatalyst inside cross-linked carboxymethyl cellulose beads: A novel photoactive hydrogel for visible-light-induced photocatalysis

    , Article Journal of Photochemistry and Photobiology A: Chemistry ; Volume 398 , 2020 Heidarpour, H ; Golizadeh, M ; Padervand, M ; Karimi, A ; Vossoughi, M ; Tavakoli, M. H ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this work, a novel photoactive cellulose-based hydrogel was prepared by simultaneous AgCl formation and entrapment inside Al (III) and Fe (III) cross-linked carboxymethyl cellulose beads. Physio-chemical and optical properties of the synthesized composites were well characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, elemental mapping, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), and diffuse reflectance spectroscopy (DRS). The photocatalytic activity of hydrogels was evaluated by the degradation of rhodamine B (RhB), as a model environmental pollutant. A comparative study showed that... 

    Kinetics of swelling of cylindrical functionally graded temperature-responsive hydrogels

    , Article Journal of Computational Applied Mechanics ; Volume 51, Issue 2 , December , 2020 , Pages 464-471 Namdar, A. H ; Sharif University of Technology
    University of Tehran  2020
    Abstract
    Cylindrical hydrogels have a wide variety of applications in microfluidics; for example, they serve as micro-valves, micro-mixers, and micro-lenses. The main advantages of them can be mentioned as their autonomous functionality due to their responses to environmental stimuli and simple geometry. Furthermore, functionally graded hydrogels have recently found applications in hydrogel actuators. Therefore, in this work, the kinetics of swelling, shrinking, and force generation of cylindrical functionally graded temperature-responsive hydrogels are investigated. Kinetics of cylindrical structure is investigated analytically by developing a mathematical model based on available constitutive... 

    Kinetics of swelling of cylindrical temperature-responsive hydrogel: a semi-analytical study

    , Article International Journal of Applied Mechanics ; Volume 12, Issue 8 , 2020 Namdar, A. H ; Mazaheri, H ; Sharif University of Technology
    World Scientific  2020
    Abstract
    Cylindrical hydrogels have a wide variety of applications, especially in microfluidics as micro-valves, micro-mixers, and micro-lenses. Main advantages of them can be mentioned as their simple geometry and autonomous functionality due to their responses to the environmental stimuli. In current research, kinetics of swelling, shrinking and force generation of cylindrical temperature-responsive hydrogels have been investigated analytically. According to this, models of fluid permeation and large deformation of the hydrogels were considered and an analytical solution was performed. In order to study the behavior of the cylindrical hydrogels, the temperature is changed between higher and lower...