Now showing 1 - 10 of 38
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    Synthesis and characterization of a novel, water-soluble polymer with pendant groups carrying cis-platinum complex
    (01-07-2004)
    Raja, S.
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    The synthesis and characterization of a polymer with pendant groups carrying a cis-platinum complex by the chemical modification route is discussed. Diethyloxomalonate functionalized polystyrene (DPS) is synthesized by the Friedel-Crafts acylation of polystyrene with diethyloxomalonate in the presence of SnCl4, by a batch-wise addition process. The reaction of DPS with cis-diaquo(trans-l,2-diaminocyclohexane)-platinum(II) results in the formation of a cis-platinum chelated polymer (PtDPS). Proton NMR and IR spectroscopies are used to confirm the transformation. The polymer synthesized is further characterized using thermogravimetric analysis (TGA) as well as UV and fluorescence spectroscopic techniques. PtDPS thus synthesized is further modified into a water-soluble polymer by another polymer modification reaction resulting in the introduction of thiobarbituric acid moieties.
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    Ambient temperature polymerization of styrene by single electron transfer initiation, followed by reversible addition fragmentation chain transfer control
    (08-01-2008)
    Harihara Subramanian, S.
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    Prakash Babu, R.
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    Controlled polymerization of styrene was carried out using ambient temperature single electron transfer initiation and propagation through the radical addition fragmentation chain transfer (SET-RAFT) method. SET-RAFT method was expected to have much wider applicability, especially for monomers that polymerize very rapidly by free/living radical polymerization. The typical RAFT polymerization required thermal/photochemical initiation and one of the end groups was required to be a fragment from the initiator. Under the SET-RAFT conditions, the ambient temperature initiation and the use of functional initiators would overcome some of the limitations of RAFT. SET-RAFT condition is expected to be very effective for monomers with a slower rate of initiation compared to the rate of propagation and those with a very high rate of propagation that require control.
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    ATRP of methyl methacrylate using a novel binol ester-based bifunctional initiator
    (15-02-2004)
    Dayananda, K.
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    Novel bifunctional initiators [1,1′-Bi-2-naphthol bis(2-bromo-2-methylpropionate); (R)-, (S)-, and racemic-] were synthesized from the esterification of 1,1′-bi-2-naphthol and used as initiators in atom transfer radical polymerization (ATRP) in conjunction with N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA), and copper (I) bromide or copper (I) chloride. The initiators synthesized were completely characterized by UV, FTIR, NMR, and Mass spectroscopies. A detailed investigation of the ATRP of methyl methacrylate (MMA) with the bifunctional initiators (BBiBN) along with CuBr or CuCl/PMDETA catalyst system in anisole was carried out at 30°. Thus, MMA polymerization is shown to proceed with first-order kinetics, with predicted molecular weight, and narrow polydispersity indices. The ATRP of glycidyl methacrylate (GMA) and tert-butyl acrylate (tBA) were also performed with BBiBN initiator in conjunction with CuBr/PMDETA catalyst system. The polymerization of GMA was carried out at 30°C, but tBA was polymerized at 60°C. Gel permeation chromatography (GPC), FTIR, NMR, UV spectroscopies, and TGA were used for the characterization of the polymers synthesized. © 2004 Wiley Periodicals, Inc.
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    Grafting of poly(methyl methacrylate) brushes from magnetite nanoparticles using a phosphonic acid based initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)
    (01-01-2008)
    Babu, Kothandapani
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    Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic-inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.
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    Interactive redox polymerization and characterization of poly(N-vinyl-2-pyrrolidinone) in the gallery of vermiculite: a novel inorganic-organic hybrid material
    (01-01-2000)
    Nisha, A.
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    Rajeswari, M. K.
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    In this article we present the synthesis of poly(N-vinyl-2-pyrrolidinone) (PNVP)-vermiculite hybrid material and its characterization by various spectroscopic techniques, X-ray diffraction (XRD), and thermal analysis. The polymer was synthesized by intercalative redox polymerization of the monomer at 110°C, using copper (II) ion-exchanged vermiculite. XRD analysis following intercalative polymerization indicates the presence of two prominent peaks with corresponding d (002) spacing of 14.3 (intercalated) and 9.9 (not intercalated) angstrom, suggesting the formation of a partially intercalated hybrid material. Electron spin resonance studies of the intercalated material show values of 'g' different from that of the Cu (II)-ion-exchanged vermiculite, indicating that polymer formed in the gallery of vermiculite complexes with the unreacted Cu (II). Thermogravimetric analysis indicates the amount of polymer in the gallery spacing to be approx. 20 mass %, which is confirmed by I2 labeling of the PNVP in the nanocomposite, followed by UV spectroscopy. The IR absorption peaks corresponding to PNVP, along with the XRD and thermal analysis data confirms that the gallery expansion is due to the formation of a partially intercalated inorganic-organic hybrid material.
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    Controlled growth of PMMA brushes on silicon surfaces at room temperature
    (24-07-2002)
    Ramakrishnan, A.
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    Rühe, Jürgen
    The atom-transfer radical polymerization of methyl methacrylate at room temperature starting from monolayers of initiators, which are covalently anchored to silicon substrates, is described. The control of layer thickness and molecular weight, a constant graft density, and a narrow molecular weight distribution of the polymers produced provide evidence for a controlled surface-initiated polymerization, and dense surface-attached polymer brushes on the SiO2 surfaces are obtained under mild reaction conditions.
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    Synthesis and characterization of block copolymers, of P(MMA-b-n-BA-b-MMA) via ambient temperature ATRP of MMA
    (01-04-2005)
    Dayananda, K.
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    Ramakrishnan, A.
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    A binol ester initiator was used as a bifunctional ATRP initiator in combination with PMDETA/copper bromide catalyst system in DMF to synthesize n-butyl acrylate macroinitiator at 50° C. The resulting macroinitiator was used for a detailed investigation of the ATRP of methyl methacrylate (MMA) with CuCl/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) catalyst system in anisole at 30° C. Thus, the MMA polymerization is shown to proceed with first order kinetics, with predicted molecular weight and narrow polydispersity indices. Gel permeation chromatography (GPC) and NMR were used for the characterization of the polymers synthesized. Copyright © Taylor & Francis, Inc.
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    Synthesis and characterization of nitroglycerin-functionalized polystyrene
    (15-04-2001)
    Raja, S.
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    The synthesis and characterization of diethyl oxomalonate-, glycerol-, and nitroglycerin-functionalized polystyrene (DPS, GPS, and NGPS) from polystyrene (PS) by the chemical-modification route were explored. DPS was synthesized by the Friedel-Crafts acylation of PS with diethyl oxomalonate in the presence of SnCl4 by a batchwise-addition process. Proton NMR studies indicate that the acylation was essentially quantitative. IR spectroscopy was additionally used to confirm the transformation. The reduction of DPS was carried out using various reduction agents and reaction conditions. The sodium hydride reduction in tetrahydrofuran resulted in a quantitative conversion to GPS as estimated by 1H NMR spectroscopy. Treatment of GPS with a nitrating mixture of nitric and sulfuric acids results in the formation of NGPS. All the polymers were characterized using gel permeation chromatography, IR, UV, 1H spectroscopic techniques, pyrolysis-mass spectrometry, and thermogravimetric analysis. This is the first investigation on the syntheses of DPS, GPS, and NGPS. © 2001 John Wiley & Sons, Inc.
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    A novel and simple method of preparation of poly(styrene-B-2-vinylpyridine) block copolymer of narrow molecular weight distribution: Living anionic polymerization followed by mechanism transfer to controlled/"living" radical polymerization (ATRP)
    (01-01-2000)
    Ramakrishnan, A.
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    A novel and simple method of preparation of a block copolymer of styrene and 2-vinylpyridine with narrow molecular weight distribution is reported. The novelty lies in the transformation of the polymerization mechanism from living anionic to controlled/"living" radical polymerization (ATRP). Thus, anionic polymerization of styrene is carried out in benzene using secbutyllithium as the initiator followed by termination with ethylene oxide to prepare hydroxy-terminated polystyrene (PS-OH). PS-OH is converted to chloride-terminated polystyrene (PS-Cl) by a displacement reaction involving thionyl chloride and pyridine in benzene. PS-Cl is used to initiate the heterogeneous ATRP of 2-vinylpyridine in p-xylene with CuCl/2,2'-bipyridine system. The polymers synthesized are characterized by gel permeation chromatography (GPC), thin layer chromatography (TLC), IR and proton NMR spectroscopies. Copyright © 2000 by Marcel Dekker, Inc.
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    A robust method for the immobilization of polymer molecules on SiO 2 surfaces
    (12-02-2008)
    Raghuraman, G. K.
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    Prucker, Oswald
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    Rühe, Jürgen
    In this work, we describe the use of hydridosilanes for the attachment of polymer monolayers to SiO2 surfaces. In one approach, first a benzophenone group containing hydridosilane is self-assembled on the SiO 2 surface followed by photochemical attachment of polymer chains deposited onto the monolayer. In a second approach an ATRP initiator is self-assembled to the substrate surface, again using hydridosilane anchor groups. The surface-attached initiator groups are subsequently used for the growth of surface-attached polymer chains in a surface-initiated polymerization reaction. It is shown that, while chlorosilanes require rather stringent exclusion of moisture during self-assembly, the hydridosilanes are rather robust and functional monolayers are formed even under ambient conditions. That in turn allows for the use of silanes in standard printing processes. In contrast to printing of chlorosilanes, which must be carried out under strictly anhydrous conditions, printing of hydridosilanes thus represents a simple and versatile technique for the generation of microstructured surfaces. © 2008 American Chemical Society.