New olefin block copolymers of ethylene/1-hexene synthesized by iron and zirconocene catalysts in the presence of ZnEt2

作者：Ahmadi Mostafa; Rashedi Reza; Ahmadjo Saeid; Karimi Mahsa; Zahmaty Majid; Mortazavi Seyed Mohammad Mahdi

来源：Journal of Thermal Analysis and Calorimetry, 2018, 131(3): 2523-2533.

DOI：10.1007/s10973-017-6824-0

• Coordination polymerization
• Block copolymer
• Comonomer selectivity
• Reversible chain transfer
• Chain shuttling polymerization

Development of olefin block copolymers (OBCs) based on new catalytic systems is challenging. We evaluate the performance of rac-ethylenebis(1-eta (5)-indenyl)zirconium dichloride (Zr) and bis(imino)pyridine iron (Fe) catalysts, with different comonomer affinities, in copolymerization of ethylene/1-hexene. In-depth investigation of thermal properties reveals that chain shuttling agent (CSA) has diverse effects on the microstructure formed by the individual catalysts. Specifically, as confirmed by CNMR measurements, the comonomer affinity of the Zr catalyst is noticeably reduced while it remains unchanged for the Fe catalyst. Copolymers produced by the binary catalytic system in the presence of CSA do not show indications for formation of blocky structure at higher Zr fractions, while at lower fractions, a significantly different behavior is exposed, e.g., high melting temperature peak is replaced by broad low-temperature endotherm and lower molar mass with narrow distribution is obtained. It could be concluded that this catalyst composition can be a good candidate for operative production of OBCs.

• 出版日期2018-3