Loading...
Search for: polymeric
0.008 seconds
Total 340 records

    Applications of polymeric reagents in organic synthesis

    , Article Monatshefte fur Chemie ; Volume 138, Issue 4 , 2007 , Pages 363-379 ; 00269247 (ISSN) Salimi, H ; Rahimi, A ; Pourjavadi, A ; Sharif University of Technology
    2007
    Abstract
    Polymer supported reagents have found many applications in recent years. Scientists in research laboratories of agrochemical and pharmaceutical industries now routinely utilize these compounds to prepare ensembles of small organic molecules for screening. This review is aimed to highlight some of the most important applications of these promising materials in organic synthesis. Furthermore, an extensive listing of polymeric reagents that were recently used in organic synthesis is included. © Springer-Verlag 2007  

    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 CMC: part 1- optimized synthesis of carboxymethylcellulose-g-polyacrylonitrile [electronic resource]

    , Article Iranian Polymer Journal ; Vol. 14, No 2, 131-138, 2005 Zohurian Mehr, M. J. (Mohammad Jalal) ; Pourjavadi, A ; Sadeghi, M
    Abstract
    As the first part of a continued research on conversion of carboxymethyl cellulosesodium salt (CMC) to useful biopolymer-based materials, large numbers of cyanide functional groups were introduced onto CMC by grafting with polyacrylonitrile (PAN). The graft copolymerization reactions were carried out under nitrogen atmosphere using ceric ammonium nitrate (CAN) as an initiator. Evidence of grafting was obtained by comparing FTIR spectra of CMC and the graft copolymer as well as solubility characteristics of the products. The synthetic conditions were systematically optimized through studying the effective factors including temperature and concentrations of initiator, acrylonitrile monomer,... 

    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... 

    Synthesis, characterization, and catalysis of recyclable new piperazine-bridged Mo(VI) polymers [MoO 2(Salen)(piperazine)] n in highly selective oxygenation of alkenes and sulfides

    , Article Journal of Coordination Chemistry ; Volume 66, Issue 16 , 2013 , Pages 2885-2900 ; 00958972 (ISSN) Bagherzadeh, M ; Zare, M ; Sharif University of Technology
    2013
    Abstract
    This study reports synthesis and characterization of polymeric [MoO2(Salen)] complexes that combine MoO2(acac)2 and polymeric ligands bearing N2O2 coordination sites, abbreviated herein as [piperazinCH2{MoO2(Salen)}]n (6), [piperazinCH2{MoO2(Salophen)}]n (7), and [piperazinCH2{MoO2(Salpn)}]n (8). The epoxidation of alkenes using tert-butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were enhanced with excellent selectivity under the catalytic influence of these coordination polymers. No relevant difference in activity was found due to change in the diamine in the Schiffs base ligands. The stability of polymeric catalysts was assessed by recycling a sample... 

    Preparation of conductive polyaniline/graphene nanocomposites via in situ emulsion polymerization and product characterization

    , Article Synthetic Metals ; Vol. 196 , 2014 , pp. 199-205 Baniasadi, H ; Ramazani, S. A ; Mashayekhan, S ; Ghaderinezhad, F ; Sharif University of Technology
    Abstract
    This work, which is a part of our ongoing studies on developing conductive scaffolds for nerve tissue engineering, reports synthesis of highly conductive binary-doped polyaniline nanoparticles and polyaniline/graphene nanocomposites. The samples were synthesized through chemical oxidation of aniline via in situ emulsion polymerization method in presence of hydrochloric acid and sodium dodecyl sulfate. Graphene nanosheets were also prepared via modified Hummer's method followed by chemical reduction using hydrazine monohydrate. Electrical conductivity measurements using a standard four-point probe technique with FTIR and UV-vis studies revealed that conductive binary-doped emeraldine salt... 

    Temperature control of styrene bulk polymerization in a tubular reactor

    , Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) Ghafoor Mohseni, P ; Shahrokhi, M ; Sharif University of Technology
    2006
    Abstract
    Due to advantages of tubular polymerization reactors, a tubular reactor was used as the postpolymerizer for thermal bulk polymerization of styrene. By solving the mathematical model, static and dynamic simulations were carried out to study the reactor's behavior. In order to have a desired product regarding the monomer conversion and polydispersity at the reactor outlet, a specific temperature profile must be kept along the reactor's length. Based on the desired profile and using the system model, a trajectory for the jacket temperature was obtained. To apply the desired jacket temperature, the jacket is divided into three zones. The set-point of each zone has been obtained by discretizing... 

    Manufacturing and Investigating of Nano carbon/Polyethylene Nanocomposites via In-situ Polymerization

    , M.Sc. Thesis Sharif University of Technology Sadrani, Alaleh (Author) ; Ramezani Saadatabdi, Ahmad (Supervisor)
    Abstract
    In this research UHMWPE/CB nanocomposites were prepared via in situ polymerization using Bi-supported Ziegler-Natta catalytic systems. Magnesium etoxide and carbon black were used as supports of catalyst. TiCl4 accompanied by triisobutyl aluminum and diisobutyl phthalate (DIBP) constituted Ziegler-Natta catalytic system. Preparation of catalyst and polymerization were done in slurry phase under the argon atmosphere. Then, structural, thermal and mechanical properties of produced nanocomposites with different CB content were evaluated by SEM, DSC, TGA, DMTA and tensile tests. Scanning Electron Microscopy (SEM) images also certified very good dispersion of CBs throughout PE matrix.... 

    Microwave-induced Cannizzaro reaction over neutral γ-alumina as a polymeric catalyst [electronic resource]

    , Article Reactive and Functional Polymers ; 01/2002; 51(1):49-53 Pourjavadi, A. (Ali) ; Soleimanzadeh, B ; Marandi, G. B
    Abstract
    γ-Alumina is used to catalyze the Cannizzaro reaction in the absence of any base under microwave irradiation in high yields. In the case of terephthalaldehyde the reaction is carried out with high selectivity  

    Modified CMC.2. Novel carboxymethylcellulose-based poly (amidoxime) chelating resin with high metal sorbtion capacities [electronic resource]

    , Article Reactive and Functional Polymers ; Volume 61, Issue 1, August 2004, Pages 23–31 Zohurian Mehr, M. J. (Mohammad Jalal) ; Pourjavadi, A ; Sadeghi, M ; Sharif University of Technology
    Abstract
    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... 

    Optimization of operating conditions in ultrafiltration process for produced water treatment via Taguchi methodology

    , Article Desalination and Water Treatment ; Volume 54, Issue 10 , June , 2015 ; ISSN: 19443994 Reyhani, A ; Sepehrinia, K ; Seyed Shahabadi, S. M ; Rekabdar, F ; Gheshlaghi, A ; Sharif University of Technology
    Abstract
    This paper describes how to find optimal operating conditions of three controlling parameters, i.e. temperature, transmembrane pressure (TMP), and cross-flow velocity (CFV) for maximizing the permeate flux and total organic carbons (TOC) rejection, and minimizing the fouling resistance using Taguchi method in ultrafiltration (UF) treatment of the real produced water. At first, the optimal operating conditions were found at a temperature of 45°C, TMP = 4 bar, and CFV of 2.25 m/s. To determine the most significant parameters affecting the response parameters, an analysis of variance was employed. In the second stage, performance of applied polymeric membrane in the UF system was studied under... 

    Functionalized poly(amidoamine) dendrimer as a strong ionic Brønsted acid organocatalyst for protection/deprotection of aldehydes

    , Article Phosphorus, Sulfur and Silicon and the Related Elements ; Vol. 189, issue. 12 , 2014 , pp. 1794-1801 ; ISSN: 10426507 Pourjavadi, A ; Hosseini, S. H ; Sharif University of Technology
    Abstract
    Poly(amidoamine) dendrimer (PAMAM) was successfully functionalized by chlorosulfonic acid to form an strong ionic acid catalyst. The resulting polymeric catalyst was shown to be an efficient catalyst for the synthesis of 1,1-diacetyl from aldehydes under free solvent conditions at room temperature. Also, the deprotection of the resulting aldehydes was investigated under catalytic conditions. The Hammett acidity function of catalyst showed that catalyst is a strong Brønsted acid. Due to the multi-functional nature of PAMAM, the catalyst has high loading level of acidic protons  

    The control of morphological and size properties of carbamazepine-imprinted microspheres and nanospheres under different synthesis conditions

    , Article Journal of Materials Research ; 2013 ; 08842914 (ISSN) Esfandyari Manesh, M ; Javanbakht, M ; Shahmoradi, E ; Dinarvand, R ; Atyabi, F ; Sharif University of Technology
    2013
    Abstract
    Potential applications of the molecularly imprinted polymers (MIPs) demand physical configurations in different size ranges. Nowadays, research on MIPs is focused on the development of new or improved morphologies, which involves control and modification of the different parameters during the synthesis. In this study, the effect of different synthesis conditions on the particle size and morphology is investigated. Carbamazepine-imprinted polymers were prepared using precipitation polymerization under various conditions such as: the amounts of cross-linker and functional monomers, initiator, porogen, temperature and time of polymerization. We studied the polymerization conditions to obtain... 

    Simulation, optimization & control of styrene bulk polymerization in a tubular reactor

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 32, Issue 4 , 2013 , Pages 69-79 ; 10219986 (ISSN) Padideh, G. M ; Mohammad, S ; Hossein, A ; Sharif University of Technology
    Jihad Danishgahi  2013
    Abstract
    In this paper, optimization and control of a tubular reactor for thermal bulk post-polymerization of styrene have been investigated. By using the reactor mathematical model, static and dynamic simulations are carried out. Based on an objective function including polymer conversion and polydispersity, reactor optimal temperature profile has been obtained. In the absence of model mismatch, desired product characteristic can also be obtained by applying the corresponding reactor wall or jacket temperature profile. To achieve this temperature trajectory, reactor jacket is divided into three zones and jacket inlet temperatures are used as manipulated variables. Effectiveness of the proposed... 

    Optimization of operating conditions in ultrafiltration process for produced water treatment via Taguchi methodology

    , Article Desalination and Water Treatment ; Volume 54, Issue 10 , May , 2015 , Pages 2669-2680 ; 19443994 (ISSN) Reyhani, A ; Sepehrinia, K ; Seyed Shahabadi, S. M ; Rekabdar, F ; Gheshlaghi, A ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    This paper describes how to find optimal operating conditions of three controlling parameters, i.e. temperature, transmembrane pressure (TMP), and cross-flow velocity (CFV) for maximizing the permeate flux and total organic carbons (TOC) rejection, and minimizing the fouling resistance using Taguchi method in ultrafiltration (UF) treatment of the real produced water. At first, the optimal operating conditions were found at a temperature of 45°C, TMP = 4 bar, and CFV of 2.25 m/s. To determine the most significant parameters affecting the response parameters, an analysis of variance was employed. In the second stage, performance of applied polymeric membrane in the UF system was studied under... 

    A study of a polymeric membrane performance in an ultrafiltration system to use in industrial application

    , Article Desalination and Water Treatment ; Volume 53, Issue 2 , Sep , 2015 , Pages 340-351 ; 19443994 (ISSN) Reyhani, A ; Rajaei, F ; Shahmoradi, M ; Kahkesh, A ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    The performance of a polymeric membrane in an ultrafiltration system under the chosen optimum conditions was studied. To achieve this, four real produced waters were dealt with. To find the optimum conditions, Taguchi method was applied. Results showed that PAN350 membrane is a potential candidate for industrial applications for three feeds which contained oil and total organic carbon (TOC) less than 1,500 and 300 ppm, respectively. The values of oil/grease, total suspended solids, and turbidity rejections were approximately 100%. Although TOC could not be entirely removed, the removal values for TOC were acceptable in this study. For the fourth feed due to the values of oil and TOC which... 

    Plasticization effect on performance of polyphenylene oxide hollow fiber membrane at high concentrations of hydrogen sulfide

    , Article 19th International Congress of Chemical and Process Engineering, CHISA 2010 and 7th European Congress of Chemical Engineering, ECCE-7, 28 August 2010 through 1 September 2010 ; 2010 Savoji, H ; Niknejad, S. M. S ; Soltanieh, M ; Sharif University of Technology
    Abstract
    Natural gas contains several impurities, e.g., CO 2 and H 2S, which have undesirable effects on the performance of the glassy polymeric membranes. The plasticization effect of H 2S at high concentrations on the gas separation performance of polyphenylene oxide hollow fiber membrane has been studied at different compositions of H 2S and feed pressures. The existence of high concentrations of H 2S in CH 4 feed mixture, which is present in many natural gas sources in Iran, enhances plasticization. For a H 2S/CH 4 mixture containing 5008 ppm H 2S at ≈ 75 psig, the H 2S permeance reduces by > 45% from its initial value. H 2S acts as a plasticizer in H 2S/CH 4 membrane separation at elevated... 

    In-situ preparation and characterization of ultra-high molecular weight polyethylene/diamond nanocomposites using bi-supported Ziegler-Natta catalyst: effect of nanodiamond silanization

    , Article Materials Today Communications ; Volume 14 , March , 2018 , Pages 53-64 ; 23524928 (ISSN) Haddadi, S. A ; Ramezani Saadatabadi, Ahmad ; Amini, M ; Kheradmand, A ; Shsrif University of Technology
    Elsevier Ltd  2018
    Abstract
    In this study, reinforcement of ultra-high molecular weight polyethylene (UHMWPE) was investigated using the sol-gel surface modified diamond nanoparticles (NDs). Nanocomposite samples were synthesized via in-situ polymerization using bi-supported Ziegler-Natta catalyst. Fourier transform infrared spectroscopy, thermogravimetric analysis and contact angle measurements proved the proper silanization (∼1.9%) of NDs. Characterization of the catalysts revealed decrease in the activity of catalysts in presence of NDs which were responsible for the lower average molecular weight of the samples. Field emission scanning electron microscopy revealed an improved dispersion of the modified NDs in... 

    Practical techniques for improving the performance of polymeric membranes and processes for protein separation and purification

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 37, Issue 2 , February , 2018 , Pages 1-23 ; 10219986 (ISSN) Vedadghavami, A ; Minooei, F ; Hosseini, S. S ; Sharif University of Technology
    Iranian Journal of Chemistry and Chemical Engineering  2018
    Abstract
    Protein separation and purification technologies play an essential role in various industries including but not limited to pharmaceuticals, dairy as well as the food sector. Accordingly, a wide variety of techniques such as chromatography and electrophoresis have been developed and utilized extensively over the years for this purpose. Despite their widespread acceptance, conventional techniques still suffer from major limitations and complexities such as short lifetime, low productivity, high-pressure drop and difficulty in scale-up among others. Membrane separation processes have received significant attention in recent years as a promising alternative that can potentially overcome the... 

    Kinetic and morphological investigation on the magnesium ethoxide-based ziegler-natta catalyst for propylene polymerization using typical external donors

    , Article Macromolecular Symposia ; Volume 285, Issue 1 , 2009 , Pages 52-57 ; 10221360 (ISSN) Dashti, A ; Ramezani Saadat Abadi, A ; Hiraoka, Y ; Kim, S. Y ; Taniike, T ; Terano, M ; Sharif University of Technology
    2009
    Abstract
    Kinetic and morphological aspects of slurry propylene polymerization using a MgCl2-supported Ziegler-Natta catalyst synthesized from a Mg(OEt)2 precursor in the presence and absence of two different external donors are investigated. The kinetic profiles show similar trend in presence and absence of donors. The Mg(OEt)2-based catalyst show a mild activation and a long-standing activity with good replication of the catalyst particles. The results show that synthesized Mg(OEt)2-based Ziegler-Natta catalyst presents a highly stable polymerization activity and good replication due to the uniform Ti distribution all over the catalyst particles. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim