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R Dhamodharan
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R Dhamodharan
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R Dhamodharan
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Dhamodharan, Raghavachari
Raghavachari, Dhamodharan
Dhamodharan, R.
Iyengar, Dhamodharan R.
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5 results
Now showing 1 - 5 of 5
- PublicationAmphiphilic polystyrene-graft-poly(N,N-dimethylamino-2-ethyl methacrylate) hydrogels synthesized via room temperature ATRP: Studies on swelling behaviour and dye sorption(01-05-2008)
;Vivek, A. V.The swelling behavior and dye sorption of polystyrene-graft-poly(N,N-dimethylamino-2-ethyl methacrylate (pseudo-hydrogel) have been investigated. The grafting of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) onto the molecular surface of polystyrene through the "grafting from" approach is performed at room temperature ATRP, resulting in pseudo-hydrogels. The swelling behavior of these hydrogel at different pH and by varying the chain length of DMAEMA was carried out. The effect of altering pH and the temperature towards the swelling is also studied. The dimensional change, caused by the stimulus behavior of the hydrogel, at varying pH is also investigated. The stimulus responsive graft copolymer was studied for the adsorption of common dyes like green torquoise blue, magenta red, rhodamine, crystal violet, congo red, methylene blue, under static condition at room temperature. The graft copolymers are observed to possess a high affinity for basic, acid, and reactive dyes. © 2008 Elsevier Ltd. All rights reserved. - PublicationAmbient temperature ATRP of benzyl methacrylate as a tool for the synthesis of block copolymers with styrene(01-05-2006)
;Munirasu, Selvaraj ;Rühe, JürgenThe 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-H 2 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. - PublicationPolymer brushes via ATRP: Role of activator and deactivator in the surface-initiated ATRP of styrene on planar substrates(14-03-2002)
;Jeyaprakash, J. D. ;Samuel, S.; Rühe, JürgenThe 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. - PublicationGrowth of poly(methyl methacrylate) brushes on silicon surfaces by atom transfer radical polymerization(01-03-2006)
;Ramakrishnan, A.; Rühe, J.Poly(methyl methacrylate) (PMMA) brushes are grown by surface-initiated atom transfer radical polymerization on silicon surfaces at various polymerization temperatures. Kinetic studies show that the layer thickness scales linearly with the degree of polymerization of the polymers under some conditions, indicating a constant graft density of the surface-attached chains. At high temperatures, the layer growth is a controlled process only for short reaction times, and after a rapid increase, the film growth levels off, and a constant thickness is obtained. At lower reaction temperatures, polymers with a lower polydispersity are obtained, but at the expense of a much slower growth rate. Accordingly, intermediate temperatures yield the highest film thickness on experimentally feasible timescales. The reinitiation of these surface-grafted PMMA chains at room temperature to either extend the chains or grow a chemically different polyglycidylmethacrylate block demonstrates the presence of active ends and the living nature of the surface-grafted PMMA chains. © 2006 Wiley Periodicals, Inc. - PublicationSynthesis of silver nanoparticles using a novel graft copolymer and enhanced particle stability via a "polymer brush effect"(02-05-2008)
;Vivek, A. V. ;Pradipta, S. M.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. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.