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The features of syndiotactic polypropylene
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AbstractThe mechanism of stereoselectivity of propylene insertion in propylene‐ethylene copolymerization on a CS symmetrical zirconium complex i‐Pr(Cp) (Flu) ZrCl2 catalyst is discussed. Calculation results indicate that not only the β‐carbon in the growing chain end of the polymer but also the substituent of the β‐carbon play an important role in the selectivity of the prochiral face of the next‐coming propylene monomer. The stereoregularity of propylene units connected to an ethylene unit (PPE) in propylene‐ethylene copolymer was observed to be lower than that in propylene sequences (PPP) in the 13C NMR spectrum, which supports the calculation results. Furthermore, the structure and properties of propylene‐olefin (ethylene, 1‐butene, 1‐pentene, 1‐hexene, and 4‐methyl‐1‐pentene) copolymers prepared with the i‐Pr(Cp) (Flu) ZrCl2 catalyst system were studied. Propylene‐1‐butene copolymer exhibits peculiarly lower melting point depression because 1‐butene units enter into the unit cell of the crystal structure of syndiotactic polypropylene.
Title: The features of syndiotactic polypropylene
Description:
AbstractThe mechanism of stereoselectivity of propylene insertion in propylene‐ethylene copolymerization on a CS symmetrical zirconium complex i‐Pr(Cp) (Flu) ZrCl2 catalyst is discussed.
Calculation results indicate that not only the β‐carbon in the growing chain end of the polymer but also the substituent of the β‐carbon play an important role in the selectivity of the prochiral face of the next‐coming propylene monomer.
The stereoregularity of propylene units connected to an ethylene unit (PPE) in propylene‐ethylene copolymer was observed to be lower than that in propylene sequences (PPP) in the 13C NMR spectrum, which supports the calculation results.
Furthermore, the structure and properties of propylene‐olefin (ethylene, 1‐butene, 1‐pentene, 1‐hexene, and 4‐methyl‐1‐pentene) copolymers prepared with the i‐Pr(Cp) (Flu) ZrCl2 catalyst system were studied.
Propylene‐1‐butene copolymer exhibits peculiarly lower melting point depression because 1‐butene units enter into the unit cell of the crystal structure of syndiotactic polypropylene.
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