Phenylacetylene (PA) and 1-hexyne (HX) were copolymerized in solution using two kinds of Ziegler-Natta catalysts, Ti(On-Bu),-AlEts and Fe(acac)s-AlEt,, in toluene and by metathesis with the WC16-Ph$n initiating system in toluene and 1, 4-dioxan. The compositions of copolymers, obtained under various monomer charge ratios in the range of 5-95 mol% of PA or HX, were determined from their 200 MHz 'H n.m.r. spectra. The experimental data processed according to the Kelen-Ttidos approach and, for comparison, by using a non-linear least squares curve-fitting procedure indicated that, for the four investigated systems, the copolymerization process of the PA/HX-pair can be adequately described by the terminal-unit model. The reactivity ratio values calculated from both methods were the same. Based on these findings, the relative reactivity of two acetylenic monomers was discussed. Interestingly, the results obtained with the Ziegler-Natta catalysts showed that the propagation step mechanisms changed greatly not only with the type of transition metal compound [Ti(On-Bu)4 and Fe(acac)J, but also with the chemical nature of ligands bonded to transition metal [Fe(acac)s and Fe(propionate)s]. On the other hand, the reaction promoted by W-containing metathesis initiator was found to be strongly dependent on the polymerization solvent. The numberaverage molecular weights of copolymer samples and the number-average sequence lengths of PA and HX-units were also reported.
Посилання на статтю:
Copolymerization of phenylacetylene and 1-hexyne using Ziegler-Natta and metathesis catalyst systems: copolymer compositions and reactivity ratios by 'H n.m.r. spectroscopy / Sandrine Duel, Alain Petit // Polymer. – 1999. – N 40. – P. 589–597.