Comparative study of classical surfactants and polymerizable surfactants (surfmers) in the reversible addition-fragmentation chain transfer mediated miniemulsion polymerization of styrene and methyl methacrylate

Cationic and anionic amphiphilic monomers (surfmers) were synthesized and used to stabilize particles in miniemulsion polymerization. A comparative study of classical cationic and anionic surfactants and the two surfmers was conducted with respect to the reaction rates and molecular weight distributions of the formed polymers. The reversible addition-fragmentation chain transfer process was used in the miniemulsion polymerization reactions to control the molecular weight distribution. The reaction rates of the surfmer-stabilized miniemulsion polymerization of styrene and methyl methacrylate were similar (in most cases) to those of the classical-surfactant-stabilized miniemulsion polymerizations. The final particle sizes were also similar for polystyrene latexes stabilized by the surfmers and classical surfactants. However, poly(methyl methacrylate) latexes stabilized by the surfmers had larger particle sizes than latexes stabilized by classical surfactants. © 2005 Wiley Periodicals, Inc.Articl

Anomalies in RAFT mediated miniemulsion polymerization

No abstract

Microwave assisted graft copolymerization of N-isopropyl acrylamide and methyl acrylate on cellulose: Solid state NMR analysis and CaCO3 crystallization

Graft copolymerization of N-isopropyl acrylamide and methyl acrylate on α-cellulose was carried out under microwave irradiation at specific cut off temperatures with cerium (IV) ammonium nitrate and potassium persulfate (KPS) as the initiating system. The role of KPS was to oxidize Ce (III) to Ce (IV) which is the active species in radical formation. The reactions at a temperature cut off of 60°C were confirmed by 13C nuclear magnetic resonance cross-polarization with magic-angle spinning (13C NMR CP/MAS) and Fourier-transform infrared spectroscopy (FTIR). The extent of grafting was calculated from weight gain and 13C resonances. The grafted cellulose was thermally more stable than the parent cellulose. An attempt to do grafting at a higher cut off temperature of 80°C was made, however, no grafting was observed from 13C NMR CP/MAS but TGA results showed that a cellulose having more thermal stability resulted which was attributed to cross linking. Crystallization of CaCO3 was carried out using the grafted materials as templates showed better nucleation and different crystal structure was observed. Copyright © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.Conference Pape

Initialization behavior at various target molecular weight RAFT-mediated methyl acrylate polymerizations

In the reversible addition-fragmentation chain transfer (RAFT) mediated polymerization of methyl acrylate, a selective reaction is observed in the early stages of the polymerization. This initialization process was earlier observed in in situ 1H NMR spectroscopy experiments where extremely low target molar masses were chosen (around DP = 5). Here, for the first time, the presence of the initialization process is identified as the cause of an induction period under typical conditions of a RAFT-mediated polymerization. © 2008 Wiley Periodicals, Inc.Articl

CMC and phase separation studies of RAFT mediated amphiphilic diblock glycopolymers with methyl acrylate and styrene

Interesting new CMC and phase separation data of carbohydrate-based self-assembling core-shell nanoparticles which were synthesized via the Reversible Addition-Fragmentation Transfer (RAFT) process. The macro-RAFT agent, poly(3-O-Methacryloyl-1,2:5,6-di-O-isopropylidene-D-glucofuranose) (PMAlpGlc), was prepared by RAFT polymerization of the glycomonomer with cumyl phenyl dithioacetate as the chain transfer agent. Chain extension with styrene and methyl acrylate afforded the diblock copolymers (PMAlpGlc-b-styrene and PMAlpGlc-b-methyl acrylate) having predetermined molecular weight and narrow molecular weight distributions. Acidolysis of these diblock copolymers were undertaken and confirmed by NMR. Coreshell nanoparticles were observed by TEM. Copyright © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.Conference Pape

Anomalies in RAFT mediated miniemulsion polymerization

No abstract

Preparation of new multiarmed RAFT agents for the mediation off vinyl acetate polymerization

In this study five xanthate (Reversible Addition-Fragmentation chain Transfer (RAFT)/Macromolecular Design through Interchange of Xanthates (MADIX)) agents were synthesized, namely monofunctional, difunctional, trifunctional and tetrafunctional species of the form S=C(O-Z)-S-R, with different leaving groups and different activating moieties some of which are completely novel. Polyvinyl acetates (PVAc) in the form of linear, three armed and four armed star shaped polymers were then successfully synthesized in reactions mediated by these xanthate RAFT/MADIX agents. Copyright © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.Conference Pape

Initialization behavior for high target molecular weight polymers using various dithiobenzoates

In the reversible addition-fragmentation chain transfer (RAFT) mediated polymerization of methyl acrylate, a selective reaction is observed in the early stages of the polymerization. This initialization process was earlier observed in in situ 1H NMR spectroscopy experiments where extremely low target molar masses were chosen (around DP = 5). Here, for the first time, the presence of the initialization process is identified as the cause of an induction period under typical conditions of a RAFT-mediated polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2500-2509, 200