Showing papers by "Dante Macciantelli published in 2005"
TL;DR: In this article, the electron beam irradiation (ESR) signals were observed after irradiation of cotton, flax and viscose from textile fibres and the ESR spectra indicated the simultaneous presence of at least three carbon-centred radical species, and when quenched in a solution of glycidyl methacrylate (GMA) a significant increase of the weight was observed.
73 citations
TL;DR: In this paper, the efficiency of three isomeric pyridinyl dithioesters and their N-oxides as chain transfer agents in the RAFT (reversible addition fragmentation chain transfer) polymerization of styrene was tested.
Abstract: The efficiency of three isomeric pyridinyl dithioesters and their N-oxides as chain transfer agents in the RAFT (reversible addition fragmentation chain transfer) polymerization of styrene was tested. Ortho (dithiopicolinates), meta (ditionicotinates), and para (dithioisonicotinates) isomers controlled the polymerization of styrene although with some retardation with respect to dithiobenzoates. The retardation, which was even greater for the N-oxides, was attributed to excessive stabilization of the dormant radical species intermediate in the RAFT process by the heteroaromatic rings as inferred from the measured reduction potentials of the compounds. Styrene polymerization was actually blocked at very low conversion in the case of the dithioisonicotinate N-oxide, and on the basis of ESR (electron spin resonance) studies it is suggested that in this case the dormant radical may actually act as a scavenger of the propagating radical. Although the knowledge beforehand of the reduction potential of a given CT...
28 citations
TL;DR: On the basis of DFT calculations, the temperature dependent variations of the spectral patterns exhibited by the radicals were attributed to restricted rotation about the Calpha-SMe bond.
Abstract: The redox properties of ethyl diethoxyphosphoryldithioacetate (1), methyl diethoxyphosphorylfluorodithioacetate (2) and methyl diethoxyphosphoryldifluorodithioacetate (3) were measured by cyclic voltammetry. Addition of free radicals to the three dithioesters led to the detection of the ESR spectra of the spin adducts only with the last two compounds. Based on the reduction potentials of the three dithioacetates, this may be explained by capto-dative stabilization of the adducts. On the basis of DFT calculations, the temperature dependent variations of the spectral patterns exhibited by the radicals were attributed to restricted rotation about the Calpha-SMe bond.
6 citations