Abstract
Vanadium complexes bearing naphthalene-bridged nitrogen-sulfonate ligand ([ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VOCl (1a) and [ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VCl2 (1b)) were synthesized. Activated by ethylaluminium sesquichloride (EASC) and in the presence of ethyl trichloroacetate (ETCA) as reactivator, complexes 1a and 1b showed activities of up to 39.1 kg polymer (mol V)−1 h−1, affording the copolymers with high molecular weights (Mw up to 28 × 104) and narrow molecular weight distributions (Mw/Mn ~ 3.0) as well as high propylene incorporation of up to 49.4%. Compared to the traditional VOCl3 system, these complexes exhibited higher propylene incorporation ability and higher catalytic activities especially at high polymerization temperatures of 50 °C and above. Determined by DSC and 13C NMR, the copolymers obtained with 1a and 1b had more random structures than that with the VOCl3 system.
Highlights
Design and synthesis of transition metal-based catalysts for olefin polymerization is a long-standing research subject since the pioneering work by Ziegler and Natta, and some of them have been successfully utilized in industrial applications [1,2,3,4,5,6,7]
Despite the unique characteristics and practical application of the classical Ziegler-type vanadium catalysts, they suffered from the decay of activity during the polymerization process as a result of reduction of active species to less active or even inactive low-valent vanadium species, which is more prevalent at elevated temperatures
The development of vanadium catalysts with high activity and stability has been recognized as an attractive target
Summary
Design and synthesis of transition metal-based catalysts for olefin polymerization is a long-standing research subject since the pioneering work by Ziegler and Natta, and some of them have been successfully utilized in industrial applications [1,2,3,4,5,6,7]. Vanadium-based catalysts, though less active than those of other systems, exhibit interesting features in olefin (co)polymerization process [8,9,10,11,12,13]. Such catalysts can produce high molecular weight polymers with narrow molecular weight distributions, ethylene/á-olefin copolymers having high á-olefin incorporation, and syndiotactic polypropylene. The development of vanadium catalysts with high activity and stability has been recognized as an attractive target
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