Ethylene and butadiene are copolymerized with neodymocene catalysts. In this paper, a
complete 1H and 13C NMR analysis of ethylene/butadiene copolymers is reported for the first time. The
results of this study show that the microstructure of copolymers depends on the cyclopentadienyl ligands
of the catalyst. The presence of the trans-1,2-cyclohexane structure, formed by intramolecular cyclization,
is detected and fully investigated by 2D NMR 1H/13C direct and long-range correlation.
Alkylation of lanthanidocene chloride complexes was performed with BuLi, Mg(Bu)(Oct), or an equimolar mixture of BuLi and AlH(iBu)2. In the case of the latter, chain transfer reactions were observed between neodymium and aluminium, and higher activities were obtained. The use of the silylene‐bridged complex, [Me2Si(3‐Me3SiC5H3)2]NdCl, in combination with BuLi and AlH(iBu)2 provided an efficient and unique catalyst for the copolymerization of ethylene with butadiene. Copolymers with high butadiene contents (up to 62 mol‐%) were synthesized. The microstructure of butadiene units was mostly trans‐1,4, and copolymers exhibited a strong alternating character. The influence of butadiene content on the thermal properties of the copolymers was also investigated.Copolymerization of ethylene with butadiene using 4/BuLi/AlH(iBu)2 (▪) and 2/BuLi/AlH(iBu)2 (▴).magnified imageCopolymerization of ethylene with butadiene using 4/BuLi/AlH(iBu)2 (▪) and 2/BuLi/AlH(iBu)2 (▴).
The field of the copolymerization of olefins with conjugated dienes has been investigated. While the insertion of butadiene is often limited with most catalyst systems designed for olefin polymerization, lanthanide metallocene catalysts insert butadiene with good efficiency. In the present paper, the preparation of a vast range of products including new polymers is reviewed.
Summary: Ethylene and butadiene were copolymerized with a silylene‐bridged bis(fluorenyl) complex {[Me2Si(C13H8)2]NdCl} (1) in combination with various alkylating agents (BuLi/AlH(iBu)2, (Bu)MgCl, Mg(Bu)(Oct)). Copolymers have a unique microstructure since they contain 1,2‐cyclohexane rings and unsaturations along the polymer chain. An intramolecular mechanism was proposed for the formation of six‐membered rings. The influence of these cyclic structures on thermal properties of the copolymers has been investigated.Proposed mechanism for formation of 1,2‐cyclohexane rings.magnified imageProposed mechanism for formation of 1,2‐cyclohexane rings.
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