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Mechanism and Effect of Polar Styrenes on Scandium‐Catalyzed Copolymerization with Ethylene
Author(s) -
Liu Bo,
Qiao Kening,
Fang Jian,
Wang Tiantian,
Wang Zichuan,
Liu Dongtao,
Xie Zhigang,
Maron Laurent,
Cui Dongmei
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201808836
Subject(s) - copolymer , comonomer , substituent , electrophile , chemistry , ethylene , scandium , monomer , polar effect , polar , polymer chemistry , styrene , catalysis , stereochemistry , photochemistry , organic chemistry , polymer , physics , astronomy
Abstract Copolymerization of ethylene (E) and polar vinyl monomers remains a problem because E propagation is hindered. Herein, for the first time, we report the copolymerization of E and polar styrenes (S R ) by using an oxophilic scandium catalyst that exhibits higher turnover frequencies than both E and S R homopolymerizations when R is an electron‐withdrawing group. This positive comonomer effect was elucidated through computing reaction profiles of E/S F copolymerization at the DFT (B3PW91) level of theory. It reveals that the secondary interaction between Sc 3+ and phenyl of the last and penultimate inserted S F units leads to a decrease of the E insertion barrier, because the electron‐withdrawing substituent enhances the electrophilicity of Sc 3+ by an inductive effect mediated by the secondary interaction. After three consecutive insertions of the E units, the secondary interaction is lost and the S F insertion is kinetically preferred over the E insertion. This process is in line with the NMR spectrum analyses which show that the resultant copolymers mainly contain S R (E) x S R sequences where x≤3.