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1.
K. Dayananda R. Dhamodharan K. Vijayakumaran T. Rajamannar 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5413-5423
A monolayer of covalently anchored, novel, binaphthyl ketone is used as a surface‐confined photochemical radical generator (PRG) for anchoring a variety of polymers to silicon surfaces. The precursor PRG is synthesized by the application of a facile and novel method for the oxidation of sterically hindered benzylic hydrocarbons to carbonyl compounds. Oxidation was carried out with a stoichiometric amount of potassium peroxydisulfate, in the presence of a catalytic amount of copper sulfate in an acetonitrile/water mixture. The PRG synthesized is characterized by 1H NMR, UV, and Fourier transform infrared (FTIR). The covalently attached monolayers are characterized by X‐ray photoelectron spectroscopy, ellipsometry, and water contact angle measurements. The method developed is applicable to the preparation of a monolayer of a variety of polymers on a wide range of substrates carrying surface hydroxyl groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5413–5423, 2004 相似文献
2.
P. Govindan A. Palamalai K. S. Vijayan K. Dhamodharan S. Subbuthai S. V. Mohan R. V. Subba Rao 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):571-574
A method is developed for the selective leaching of 233U from a thorium oxalate cake. The leaching capacity of ammonium carbonate and nitric acid have been investigated, showing that (NH4)2CO3 leads to higher recovery. The maximum leaching efficiency is obtained using 0.5% ammonium carbonate, with a minimal thorium pick-up. A uranium recovery of 94% is obtained after three consecutive contact experiments in carbonate media, with minimal thorium uptake in the leachate. This process was applied to an actual plant stream, allowing the reduction of the 233U -activity from 5.64 to 0.3 Ci/g of thorium oxalate cake. 相似文献
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G. K. Raghuraman Jürgen Rühe Raghavachari Dhamodharan 《Journal of nanoparticle research》2008,10(3):415-427
Stable dispersion of titania nanoparticles in organic solvents are obtained by grafting poly(methyl methacrylate) layer on
to the surface. Titania nanoparticles are synthesized through the hydrolysis of titanium (IV) isopropoxide. The average size
of the titania particles is found to be 15 ± 2 nm. The polymer layer was introduced onto the surface by immobilizing the initiating
moiety. Azo initiator moiety required for surface-initiated conventional free radical polymerization and a tertiary bromide
initiator moiety required for ATRP are attached covalently to the titania nanoparticulate surface through the surface hydroxyl
groups. The “encapsulation” of PMMA layer results in the steric stabilization of the titania nanoparticles. Another important
finding is that it is possible to grow polymer layer in a controlled fashion. 相似文献
5.
Kannapiran Rajendrakumar R. Dhamodharan 《Journal of polymer science. Part A, Polymer chemistry》2011,49(10):2165-2172
Isobornyl methacrylate (IBMA), a bulky hydrophobic methacrylate, undergoes very fast polymerization, in bulk, with Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA)/ethyl‐2‐bromoisobutyrate system, at ambient temperature. IBMA also undergoes a spontaneous initiator‐free polymerization, at ambient temperature, with Cu(I)Br/PMDETA catalytic system in dimethyl sulfoxide–water mixtures. The rate of the polymerization is seen to increase with the water content up to 80 mol % of water. A possible intervention of air in initiation is proposed. The active Cu(0) formed by the disproportionation of Cu(I) species in aqueous medium probably plays a vital role for a possible air‐initiation of IBMA via single electron transfer‐living radical polymerization (SET‐LRP) mechanism. A high tolerance level to water under SET‐LRP conditions is demonstrated. The poly(IBMA) samples obtained exhibit low molecular weight distributions (1.1–1.3). Similar behavior was not observed with other common methacrylates such as methyl methacrylate, t‐butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
6.
Munirasu S Karunakaran RG Rühe J Dhamodharan R 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):13284-13292
We demonstrate, for the first time, the synthesis of model poly(benzyl methacrylate) [P(BnMA)] brushes of very high thickness (>300 nm) on silicon wafer. P(BnMA) brush is also synthesized from the surface of silica nanoparticles, from a covalently anchored initiator monolayer, using ambient temperature ATRP. The kinetic studies and block copolymerization from the surface anchored P(BnMA)-Br macroinitiator showed that the polymerization was controlled in nature. AFM, ellipsometry, and water contact angle were used for the characterization of the polymer brush. The grafting density of the P(BnMA) brush, formed by immersion in a dilute monomer solution, was relatively less (~11% less) in comparison to that obtained by immersion in neat monomer under similar conditions. The P(BnMA)-Br macroinitiator brushes were used to synthesize P(BnMA-b-S) diblock copolymer brushes by the ATRP of styrene at 95 °C. The P(BnMA-b-S) brushes showed stimulus response to a selective solvent and various nanopatterns were observed according to the composition of the block copolymer. 相似文献
7.
Selvaraj Munirasu Jürgen Rühe Raghavachari Dhamodharan 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2848-2861
The rapid atom transfer radical polymerization (ATRP) of benzyl methacrylate (BnMA) at ambient temperature was used to synthesize block copolymers with styrene as the second monomer. Various block copolymers such as AB diblock, BAB symmetric and asymmetric triblock, and ABABA pentablock copolymers were synthesized in which the polymerization of one of the blocks namely BnMA was performed at ambient temperature. It is demonstrated that the block copolymerization can be performed in a controlled manner, regardless of the sequence of monomer addition via halogen exchange technique. Using this reaction condition, the composition (ratio) of one block (here BnMA) can be varied from 1 to 100. It is further demonstrated that in the multiblock copolymer syntheses involving styrene and benzyl methacrylate, it is better to start from the PS macroinitiator compared with PBnMA macroinitiator. The polymers synthesized are relatively narrow dispersed (<1.5). It is identified that the ATRP of BnMA is limited to certain molecular weights of the PS macroinitiator. Additionally, a preliminary report about the synthesis of the block copolymer of BnMA‐methyl methacrylate (MMA), both at ambient temperature, is demonstrated. Subsequent deprotection of the benzyl group using Pd/C? H2 results in methacrylic acid (MAA)–methyl methacrylate (MAA–MMA) amphiphilic block copolymer. GPC, IR, and NMR are used to characterize the synthesized polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2848–2861, 2006 相似文献
8.
Polymer‐encapsulated silver nanoparticles were synthesized and sterically stabilized by a new core‐shell type system consisting of poly(S‐alt‐MA)‐graft‐PMMA copolymer that acts as a scaffold for the synthesis of size confined nanoparticles. The graft copolymer is synthesized via ambient temperature ATRP using the CuBr/PMDETA catalytic system at ambient temperature. The graft copolymer is hypothesized to function as a scaffold with the anhydride part interacting strongly with the silver ions, while the PMMA graft functions as a polymer brush that stabilizes the dispersion and prevents the particle aggregation due to a ‘polymer brush effect’. UV absorption and TEM studies confirm that the synthesized silver composite particles have a core‐shell structure.
9.
J. D. Jeyaprakash S. Samuel R. Dhamodharan Jürgen Rühe 《Macromolecular rapid communications》2002,23(4):277-281
The role of activator and deactivator species in the surface‐initiated atom‐transfer radical polymerization of styrene using CuBr/CuBr2/pentamethyldiethylenetriamine as a model system is described. The influence of initially added deactivator with respect to the degree of controlling the layer growth and thickness is studied. Variation of the activator concentration results in changes of the kinetics as well as brush thicknesses consistent with the well‐known rate laws of ATRP. 相似文献
10.
J. D. Jeyaprakash S. Samuel R. Dhamodharan Christopher K. Ober 《Journal of polymer science. Part A, Polymer chemistry》2000,38(7):1179-1183
A solvent‐free method for the hydrosilylation of pendant double bonds in block copolymers is reported in this article. An anionically prepared block copolymer, poly(styrene‐b‐1,2‐butadiene), was heated with 1H,1H,2H,2H‐perfluorooctyldimethylhydrosilane in the presence of a nonacidic platinum catalyst for 24–26 h to obtain a quantitatively hydrosilylated block copolymer. Gel permeation chromatography, IR, and thermogravimetric analysis were used to characterize the block copolymers obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1179–1183, 2000 相似文献