Search results for " Radical polymerization"
showing 10 items of 51 documents
Preparation of drug-polymer composites by polymerization in supercritical carbon dioxide: a new method to increase the dissolution rate of bioactive …
2008
Dispersion Copolymerization of Vinyl Monomers in Supercritical Carbon Dioxide.
2003
The thermally initiated free-radical dispersion copolymerization of methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMA) in supercritical carbon dioxide has been studied in the presence of polysiloxane surfactants. The formation of a stable latex seems to be related to the presence of at least one reactive end group in the surfactant macromolecule, thus suggesting that anchoring of the stabilizer to the surface of the growing polymer particles occurs through chemical grafting. In the case of a molar ratio of DMA to MMA lower than 0.40, microspherical copolymer particles with yields ranging from 81 to 97% were collected from batch polymerizations carried out at 65 °C and 23-28 MPa usin…
Long-Distance Magnetic Interaction of Exchange-Coupled Copper Dimers with Nitronyl Nitroxide and tert-Butyl Nitroxide Radicals
2009
To study long-distance magnetic interactions between exchange-coupled metal centers and coordinated radical moieties, two new homodimetallic Cu(II) complexes held together by the chelating ligand L(nPr) = N,N,N',N'-tetrakis(N-propyl-2-benzimidazolyl)-2-hydroxy-1,3-diaminopropane and additionally bridged by either a nitronyl nitroxide (NIT) or a tert-butyl nitroxide (NOA) radical-substituted benzoate have been prepared. The complexes have been investigated by X-ray crystallography, magnetic susceptibility measurements, electron paramagnetic resonance (EPR) spectroscopy, and density functional theory (DFT) calculations. For comparison additionally the related copper dimer with the bridging di…
Radiation curing of diacrylate glycerolate of bisphenol-A in the presence of an organically modified montmorillonite for the production of flame-resi…
2006
Polymerization of an acrylate derivative of bisphenol-A by ionizing radiation in the presence of an organically modified montmorillonite was carried out in order to produce a flame-retardant composite. The measurement of the thermal effect during irradiation indicates that radiation curing of pure resin and resin-clay mixtures occurred in both cases. Moreover, differential scanning calorimetry and dynamic mechanical thermal analysis showed that a curing completion can be obtained by thermal curing after irradiation with a significant increase of the glass transition temperature. The morphology was investigated by X-ray diffraction and transmission electron microscopy. These have indicated t…
Biocompatible Polymers and Processing Techniques in Drug Delivery and Tissue Engineering
2013
Study of Atrp Process for the Grafting of Vinyl Monomers on PVC and PVDF
2014
STUDY OF ATRP PROCESS FOR THE GRAFTING OF VINYL MONOMERS ON PVC AND PVDF Sonia Lanzalaco, Onofrio Scialdone, Alessandro Galia, Rosalia Mauro, Flavia Lazzano Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Viale delle Scienze, Palermo e-mail: sonia.lanzalaco@unipa.it ATRP (atom transfer radical polymerization) has been recently used to prepare graft copolymers with regularly-spaced polymer chains from polymeric macroinitiators that have pendant chemical groups containing radically transferable halogen atoms [1]. The halogen atom serves as initiation site for the polymerization of side chains. Furthermore, Matyjaszewsky and Gennaro showed that an externally applied ele…
Contribution of Protein Flexibility to the Foaming Properties of Casein
1990
The effect of biopolymer flexibility on the foaming properties of casein was investigated. Flexibility was altered by: (1) chemical modification (covalent binding of a monosaccharide on the lysyl residues) or (2) pH change. Electron Spin Resonance was used to measure the reorientational frequency of casein residues labeled with nitroxide radicals. High levels of glycosylation induced increased protein flexibility and improved the foaming capacity. Good agreement was observed between higher values of flexibility and improved surface properties near the isoelectric point.
Grafting of polymer chains on the surface of carbon nanotubes via nitroxide radical coupling reaction
2015
Poly(butylene succinate) (PBS) was grafted on the surface of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) modified multi-walled carbon nanotubes (MWCNTs) via a nitroxide radical coupling reaction. TEMPO functionalized MWCNTs (MWCNTs-g-TEMPO) were synthesized using the Cu(I)-catalyzed azide/alkyne click chemistry approach and the covalent bond of the nitroxide moieties onto the MWCNTs was confirmed via electron paramagnetic resonance (EPR) spectroscopy. The PBS grafting on the sidewalls of MWCNTs was carried out in solution via peroxide-induced formation of macroradicals and it was confirmed by EPR and attenuated total reflectance Fourier transform infrared analysis. Preliminary rheological …
A new approach for the synthesis of magnetic materials based on nitroxide free radicals and inorganic coordination polymers
2001
The use of nitronyl nitroxide (NN) radicals as spectators inside extended inorganic magnetic lattices is described. Two possibilities are presently being explored, namely, the design of oxalato-bridged bimetallic networks by using cationic NN radicals of the N-alkylpyridinium type as templating agents, and the design of bimetallic lattices based on hexacyanometalates and nickel(II) diaminocomplexes incorporating anionic NN radicals of the carboxyphenyl type.
Functionalization of aliphatic polyesters by nitroxide radical coupling
2014
Functionalized poly(butylene succinate) (PBS) samples were prepared by a post-polymerization method based on the coupling reaction between TEMPO derivatives bearing different functionalities and PBS macroradicals generated by H-abstraction using a peroxide. 4-Benzoyloxy-2,2,6,6-tetramethylpiperidine-1- oxyl (BzO-TEMPO) and 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO), a pro-fluorescent nitroxide, were successfully grafted on PBS, as revealed by MALDI TOF MS and UV-Vis spectroscopy. The functionalization degrees were accurately determined by UV-Vis analysis and confirmed by 1H-NMR spectroscopy. The grafting site was identified by combining theoretical calculations with e…