Abstract
The copolymerization of ethylene‒diene conjugates (butadiene (BD), isoprene (IP) and nonconjugates (5-ethylidene-2-norbornene (ENB), vinyl norbornene VNB, 4-vinylcyclohexene (VCH) and 1, 4-hexadiene (HD)), and terpolymerization of ethylene-propylene-diene conjugates (BD, IP) and nonconjugates (ENB, VNB, VCH and HD) using two traditional catalysts of C2-symmetric metallocene—silylene-bridged rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (complex A) and ethylene-bridged rac-Et(Ind)2ZrCl2 (complex B)—with a [Ph3C][B(C6F5)4] borate/TIBA co-catalyst, were intensively studied. Compared to that in the copolymerization of ethylene diene, the catalytic activity was more significant in E/P/diene terpolymerization. We obtained a maximum yield of both metallocene catalysts with conjugated diene between 3.00 × 106 g/molMt·h and 5.00 × 106 g/molMt·h. ENB had the highest deactivation impact on complex A, and HD had the most substantial deactivation effect on complex B. A 1H NMR study suggests that dienes were incorporated into the co/ter polymers’ backbone through regioselectivity. ENB and VNB, inserted by the edo double bond, left the ethylidene double bond intact, so VCH had an exo double bond. Complex A’s methyl and phenyl groups rendered it structurally stable and exhibited a dihedral angle greater than that of complex B, resulting in 1, 2 isoprene insertion higher than 1, 4 isoprene that is usually incapable of polymerization coordination. High efficiency in terms of co- and ter- monomer incorporation with higher molecular weight was found for complex 1. The rate of incorporation of ethylene and propylene in the terpolymer backbone structure may also be altered by the conjugated and nonconjugated dienes. 13C-NMR, 1H-NMR, and GPC techniques were used to characterize the polymers obtained.
Highlights
The design and production of well-defined, single-site catalysts from coordination compounds has generated new opportunities for academic and industrial researchers for the synthesis of polyolefin with the precise control of the chain structure and physical properties [1,2,3,4]
We performed a comparative analysis of metallocene-based ethylene/conjugated and ethylene/nonconjugated dienes’ copolymerization under the same reaction conditions
The copolymerization of ethylene/diene and ethylene/propylene/diene terpolymerization were successfully symmetrically performed by the complexes, namely, rac-Me2 Si (2-Me-4-Ph-Ind)2 ZrCl2 - and rac-Et(Ind)2 ZrCl2, in combination with 2 equiv. of borate
Summary
The design and production of well-defined, single-site catalysts from coordination compounds has generated new opportunities for academic and industrial researchers for the synthesis of polyolefin with the precise control of the chain structure and physical properties [1,2,3,4]. Ethylene propylene diene monomer (EPDM) elastomeric materials are a promising class of thermoplastics with versatile applications widely used in outdoor applications like the roofing of buildings, sealing of automotive windows/doors, and drinking water due to chloramine and chlorine resistance. These properties depend on several parameters, such as co/ter monomer type, composition, and chain distribution. Wang and co-workers determined that the long-chain branching in metallocene-catalyzed olefins polymerizations was the determining factor in controlling the rheological properties of the EPDM [9,10,11]
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