Generation of metal nanoparticles in spherical polyelectrolyte brushes and their application in heterogeneous catalysis
type: CreativeWork
description: This thesis describes synthesis of spherical cationic polyelectrolyte brushes by “grafting from” technique. The spherical polyelectrolyte brushes have been used as “nanoreactors” for the synthesis of metal nanoparticles (Gold, Platinum and Silver). The catalytic activity of the resulting metal/polymer nanocomposites has been tested by heterogeneous hydrogenation of carbonyl groups. The synthesis of the cationic spherical polyelectrolyte brushes is achieved by a three-step procedure. Firstly, cationic polystyrene core particles are synthesized by emulsion polymerization by using a cationic surfactant and a cationic thermal initiator. In the second step, a thin layer of photoinitiator is generated around the particles by addition of the photoinitiator under “starved conditions” . The photoinitiator is a monomer, which is added when the formation of core particles is in the last stage. The photoinitiator polymerizes with the styrene to give a covalently bound photoinitiator. In the third and last Step, the brushes are grafted on the core particles by photoemulsion polymerization, where the initiation is triggered by UV/VIS radiation. The important parameters of the brushes- contour length and grafting density are determined by the cleavage of the chains from the surface by alkaline hydrolysis. The ester functionality within the photoinitiator is hydrolyzed under the harsh conditions of hydrolysis. The cleaved chains are analyzed to determine the molecular weight. The grafting of the charged polymeric chains stabilizes the colloids even under unfavorable conditions like high ionic strength and high pH. The behavior of brushes is investigated at different ionic strength and pH. At different ionic strengths brushes show three regimes- osmotic, salted and neutral regime. At increasing ionic strength, a shrinking in brush thickness is observed due to the screening of ionic charges. The cationic brushes (polyamino ethylmethacrylate hydrochloride and poly vinylbenzylamine hyd…
abstract: This thesis describes synthesis of spherical cationic polyelectrolyte brushes by “grafting from” technique. The spherical polyelectrolyte brushes have been used as “nanoreactors” for the synthesis of metal nanoparticles (Gold, Platinum and Silver). The catalytic activity of the resulting metal/polymer nanocomposites has been tested by heterogeneous hydrogenation of carbonyl groups. The synthesis of the cationic spherical polyelectrolyte brushes is achieved by a three-step procedure. Firstly, cationic polystyrene core particles are synthesized by emulsion polymerization by using a cationic surfactant and a cationic thermal initiator. In the second step, a thin layer of photoinitiator is generated around the particles by addition of the photoinitiator under “starved conditions” . The photoinitiator is a monomer, which is added when the formation of core particles is in the last stage. The photoinitiator polymerizes with the styrene to give a covalently bound photoinitiator. In the third and last Step, the brushes are grafted on the core particles by photoemulsion polymerization, where the initiation is triggered by UV/VIS radiation. The important parameters of the brushes- contour length and grafting density are determined by the cleavage of the chains from the surface by alkaline hydrolysis. The ester functionality within the photoinitiator is hydrolyzed under the harsh conditions of hydrolysis. The cleaved chains are analyzed to determine the molecular weight. The grafting of the charged polymeric chains stabilizes the colloids even under unfavorable conditions like high ionic strength and high pH. The behavior of brushes is investigated at different ionic strength and pH. At different ionic strengths brushes show three regimes- osmotic, salted and neutral regime. At increasing ionic strength, a shrinking in brush thickness is observed due to the screening of ionic charges. The cationic brushes (polyamino ethylmethacrylate hydrochloride and poly vinylbenzylamine hyd…
author: Sharma, Geeta
date published: 2005-07-05
date modified: 2026-07-27T18:49:29Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth