Search results for "Radical"
showing 10 items of 1401 documents
Synthesis and radical polymerization of novel methacrylates with mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates as photosensitive components
2001
New polymerizable mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates 5a-f have been synthesized using tosylated 2-hydroxymethyl methacrylate and various thioureas and malonic acids. Radical polymerization of the mesoionic derivatives 5a, c, d, e with AIBN as initiator resulted in soluble polymers, which were used for the preparation of photosensitive films.
Synthesis of polymeric 1-iminopyridinium ylides as photoreactive polymers
2010
Two synthetic routes to polymeric 1-imino pyridinium ylides as new photoreactive polymeric architectures were investigated. In the first approach, polymerization of newly synthesized 1-imino pyridinium ylide containing monomers yielding their polymeric analogues was achieved by free radical polymerization. Alternatively, reactive precursor polymers were synthesized and converted into the respective 1-imino pyridinium ylide polymers by polymer analogous reactions on reactive precursor polymers. Quantitative conversion of the reactive groups was achieved with pentafluorophenyl ester containing polymers and newly synthesized photoreactive amines as well as by the reaction of poly(4-vinylbenzoy…
Cyclodextrins in polymer synthesis: Free radical polymerization of cyclodextrin complexes withN-methacryloyl-11-aminoundecanoic acid orN-methacryloyl…
1998
The hydrophobic monomers N-methacryloyl-11 -aminoundecanoic acid (1) or N-methacryloyl-1-aminononane (2) were incorporated as guests into the cavity of heptakis(2,6-di-O-methyl)-β-cyclodextrin (Me 2 -β-CD) as a host, yielding the water compatible monomers N-methacryloyl-l 11-aminoundecanoic acid/ Me 2 -β-CD-complex (1a) and N-methacryloyl-1 -aminononane/Me 2 -β-Cl complex (2a). These complexes were polymerized radically in aqueous medium. The resulting polymers 1b and 2b which were obtained from the complexes 1a and 2a, are insoluble in water because of the unthreading of the cyclodextrin during the polymerization. The polymerization rate of 1a and 2a is high in comparison to the rate of th…
Cyclodextrins in polymer synthesis: free radical polymerisation of cyclodextrin complexes of cyclohexyl and phenyl methacrylate in aqueous medium
1998
The polymerisation mechanism of 2,6-dimethyl-β-cyclodextrin (Me2-β-CD) complexes of phenyl methacrylate (1) and cyclohexyl methacrylate (2) is described. The polymerisation of the complexes 1 a and 2a was carried out in water with potassium peroxodisulfate/potassium hydrogensulfite as initiator. The unthreading of the Me2-β-CD during the polymerisation led to water-insoluble poly(phenyl methacrylate) (1b) and poly(cyclohexyl methacrylate) (2b). By comparison, analogously prepared polymers from uncomplexed monomers 1 and 2 in homogeneous organic solvent (THF) with AIBN as radical initiator showed significantly lower viscosities and were obtained in lower yields in both cases.
Cyclodextrins in polymer synthesis: Free radical polymerization of methylated β-cyclodextrin complexes of methyl methacrylate and styrene, controlled…
2000
Methylated β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers methyl methacrylate (1) or styrene (2) yielding the water-soluble 1 : 1-host/guest complexes methyl methacrylate/me-β-CD (1 a) and styrene/me-β-CD (2 a), respectively. In addition, the hydrophobic chain-transfer agent dodecanethiol (3) was complexed by two equivalents of me-β-CD yielding the water-soluble dodecanethiol/me-β-CD (3 a). The included monomers were polymerized in water by a free-radical mechanism in the presence of 3 a as the chain-transfer agent. The chain-transfer constants were determined. In order to evaluate these results, the chain-transfer constants of 3 were also determined in the case of th…
Cyclodextrins in Polymer Synthesis: Synthesis and Influence of Methylatedβ-Cyclodextrin on the Radical Polymerization Behavior of 1,1-Disubstituted 2…
2001
The chemical and enzymatic hydrolyses of 1,1-diethoxycarbonyl-2-vinylcyclopropane (1) were investigated. The product of the pig liver esterase (PLE)-catalyzed hydrolysis of 1 is a chiral trans monoester of 2-vinylcyclopropane dicarboxylic acid. New 1,1-disubstituted 2-vinylcyclopropane monomers (2a, b) were synthesized by the esterification of this ester. Methylated β-cyclodextrin was used to complex monomers 2a, b, yielding water-soluble 1 : 1 host/guest complexes. These complexes were polymerized in aqueous media by a free-radical ring-opening mechanism.
New Perspectives of HPMA-based Copolymers Derived by Post-Polymerization Modification
2014
Poly[N-(2-hydroxypropyl) methacrylamide] (HPMA) was one of the first polymers applied as polymer drug conjugate in the clinics. Since then many attempts have been made to expand the functionality of HPMA-based copolymers from advanced synthetic pathways to multiple biomedical applications. This Feature Article highlights multifunctional HPMA based copolymers prepared by controlled radical polymerization and subsequent post-polymerization modification of activated ester precursor polymers via aminolysis. This approach combines precise control of the polymer's microstructure (molecular weight, dispersity, block copolymer formation, end group functionalization) with an easy introduction of var…
Influence of the irradiation parameters on the molecular modifications of an isotactic polypropylene gamma-irradiated under vacuum
2000
Isotactic polypropylene was irradiated under vacuum in a complete set of experimental conditions. The influence of the irradiation parameters, total absorbed dose, D, and dose rate, I, was analysed in order to verify the theoretical predictions of a simple kinetic model, already presented (Sarcinelli L, Valenza A, Spadaro G. Polymer 1997;38:2307), based on the rates of the main reactions occurring during irradiation, i.e. β-scission, addition to double bonds and termination. The concentration of free radicals and double bonds formed during irradiation is detected together with a comparison to their dependence on the irradiation parameters. A quantitative determination of the “inversion curv…
Synthesis, characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsiv…
2009
Abstract A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly( N -2-hydroxyethyl)- dl -aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance ( 1 H NMR), Fourier-Transformed Infrare…
Comparison of living polymerization systems
1994
Recent developments in the field of living polymerization are surveyed. Comparison of the available mechanistic and kinetic information is made for living anionic, cationic, free radical, group transfer, ring-opening metathesis, Ziegler-Natta and immortal polymerizations. This evaluation indicates that the majority of living polymerizations involve quasiliving equilibrium between active (propagating) and dormant (nonpropagating) polymer chains. On the basis of the kinetics of a general model for quasiliving and ideal living polymerizations it is concluded that ideal living polymerization is a special subclass of quasiliving polymerizations. Classification of living polymerization systems is…