The (E) isomer in mixtures of (E) and (Z) 1,3-hexadiene was polymerized with the system CoCl2(PiPrPh2)2-MAO, a highly active and stereospecific catalyst for the preparation of 1,2 syndiotactic polybutadiene. A new crystalline polymer with a melting point of 109 8C was obtained. The polymer was characterized by IR, NMR (13C, 1H in solution and 13C in the solid-state), X-ray diffraction, DSC, GPC and it was found to have a trans-1,2 syndiotactic structure with a 5.18 6 0.04 A ˚ fiber periodicity. Since only the (E) isomer was polymerized, at the end of the reaction we were able to separate the (Z) isomer, which was ultimately polymerized with CpTiCl3-MAO at low temperature, obtaining a low molecular weight, stereoregular polymer that, characterized by IR and NMR methods, was found to exhibit a cis-1,2 syndiotactic structure, never reported before. Molecular mechanics calculations were carried out on the trans-1,2 syndiotactic polymer and structural models consistent with the Xray diffraction data are proposed
Synthesis and structural characterization of syndiotactic trans-1,2 and cis-1,2 polyhexadienes / G. RICCI, A. BOGLIA, T. MOTTA, F. BERTINI, A.C. BOCCIA, L. ZETTA, E. ALBERTI, A. FAMULARI, P. AROSIO, S.V. MEILLE. - In: JOURNAL OF POLYMER SCIENCE. PART A, POLYMER CHEMISTRY. - ISSN 0887-624X. - 45:22(2007), pp. 5339-5352. [10.1002/pola.22279]
Synthesis and structural characterization of syndiotactic trans-1,2 and cis-1,2 polyhexadienes
P. ArosioPenultimo
;
2007
Abstract
The (E) isomer in mixtures of (E) and (Z) 1,3-hexadiene was polymerized with the system CoCl2(PiPrPh2)2-MAO, a highly active and stereospecific catalyst for the preparation of 1,2 syndiotactic polybutadiene. A new crystalline polymer with a melting point of 109 8C was obtained. The polymer was characterized by IR, NMR (13C, 1H in solution and 13C in the solid-state), X-ray diffraction, DSC, GPC and it was found to have a trans-1,2 syndiotactic structure with a 5.18 6 0.04 A ˚ fiber periodicity. Since only the (E) isomer was polymerized, at the end of the reaction we were able to separate the (Z) isomer, which was ultimately polymerized with CpTiCl3-MAO at low temperature, obtaining a low molecular weight, stereoregular polymer that, characterized by IR and NMR methods, was found to exhibit a cis-1,2 syndiotactic structure, never reported before. Molecular mechanics calculations were carried out on the trans-1,2 syndiotactic polymer and structural models consistent with the Xray diffraction data are proposedPubblicazioni consigliate
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