Arnaldo Roggero

Sequence analysis of ethylene sulphide-propylene sulphide copolymers by carbon-13 nuclear magnetic resonance

Abstract Ethylene sulphide-propylene sulphide copolymers, prepared with anionic type catalysts, have been investigated by 13C NMR. The peaks have been assigned both in terms of diad and triad monomer sequences and in terms of tacticity. It has been shown that the propylene sulphide monomer units were directionally oriented and the tacticity was approximately random. We have also determined the effect of methyl substitution in various positions on the chemical shift of the main chain carbon atoms.

Evaluation of the reactivity ratios and sequence distribution in episulphide copolymers by 13C NMR

Abstract The microstructure (in particular the distribution of the monomeric units) has been determined by means of 13 C NMR for the three copolymers ethylene sulphide-propylene sulphide (ES-PS), ethylene sulphide-isobutylene sulphide (ES-IBS) and propylene sulphide-isobutylene sulphide (PS-IBS) prepared with anionic catalysts. Low and high conversion copolymers have been analysed. The results for the diad and triad fractions have been used for the evaluation of the reactivity ratios in the copolymerizations. The values are discussed and compared with those found using the Finemann and Ross method.

13C-{1H} NMR spectra of episulphide copolymers

Abstract Ethylene sulphide-isobutylene sulphide and propylene sulphide-isobutylene sulphide copolymers have been prepared using anionic catalysts and investigated by 13C-{1H} NMR spectroscopy. The carbon-13 NMR spectra are assigned in terms of diad and triad sequences. There is discussion of the effects of mono- or dimethyl substitution in the α, β, γ or δ positions on the chemical shift of the main chain carbon atoms. It has also been shown that for isobutylene sulphide, as for propylene sulphide, under the influence of an anionic catalyst, there is a normal ring opening only at the primary carbon atom.

On the Epimerization of endo-Dicyclopentadiene during Terpolymerization with Ethylene and Propylene

Abstract The isomerization of endo-DCP (I) to exo-DCP (II) during the synthesis of EPDM with several Ziegler-Natta catalysts has been investigated by means of IR spectroscopy and by reference to EPDM containing different levels of true exo-DCP. The I - II epimerization was absent for ail the catalysts examined. Only with the systems VC14-Et2AlCl was a trace of isomerization observed, and then only at the limit of sensitivity of the analytical method. No isomerization was detected via gas-chromatographic analysis in monomeric DCP recovered from the polymerization mixture. Ziegler-Natta catalysts having acidic character can homopolymerize I, but epimerization was observed only with the system voc13-Et3Al2Cl3. The results obtained have been interpreted in terms of a terpolymerization mechanism having a prevalent coordinated character. The poly functionality of Ziegler-Natta catalysts is sometimes responsible of the secondary isomerization process.

Syntheses and properties of ethylene sulphide-isobutylene sulphide copolymers and their unsaturated terpolymers

The synthesis with anionic catalysts and the characterization of ESIBS copolymer and ESIBSATE terpolymer are reported (ES, IBS, ATE and PS = ethylene sulphide, isobutylene sulphide, 3-allyloxy-1,2-epithiopropane and propylene sulphide respectively). For ESIBS copolymer with 35–55% ES, nearly amorphous structures, were obtained. Microstructures, investigated by 13C-NMR, have been compared with that of the ESPS copolymer; the ESIBS copolymer has greater blockiness than ESPS. Some preliminary results on the properties of ESIBSATE unsaturated terpolymer are also reported and compared with those of the known ESPSATE terpolymer. The good swelling values shown by the former are related to the possibility of obtaining amorphous structures with a high ES content.