Nonconjugated α,ω-Diolefin/Propylene Copolymerization to Long Chain-Branched Polypropylene by Ziegler–Natta Catalyst: Overcoming Steric Hindrance by Introducing an Extra Electronic Pulling Effect,Macromolecules

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Nonconjugated α,ω-Diolefin/Propylene Copolymerization to Long Chain-Branched Polypropylene by Ziegler–Natta Catalyst: Overcoming Steric Hindrance by Introducing an Extra Electronic Pulling Effect
Macromolecules ( IF 5.1 ) Pub Date : 2018-11-08 00:00:00 , DOI: 10.1021/acs.macromol.8b01958
Tingting Yang _{1,

2} , Yawei Qin ₁ , Jin-Yong Dong _{1,

2}

Affiliation

Synthesis of long chain-branched polypropylene (LCB-PP) by propylene copolymerization with nonconjugated α,ω-diolefin is a steric hindrance-prevailing reaction process which involves in copolymerization not only α,ω-diolefin itself (α-olefin copolymerization) but also polymeric olefin intermediate derived from the first α-olefin copolymerization (ω-olefin copolymerization). This reaction mishap reaches its extreme when Ziegler–Natta catalysts based on MgCl₂-supported TiCl₄ (MgCl₂/TiCl₄ catalysts) are considered as catalyst, which produce active sites that are highly sensitive to olefin monomer’s steric bulkiness. A proposition is put forward that such a steric difficulty may be overcome by functionalization of α,ω-diolefin with Lewis base functionality, which would usher in an extra electronic pulling effect to help with olefin coordination to the active center in both the α,ω-diolefin’s monomeric α-olefin and the polymeric ω-olefin polymerization steps. Three model compounds, including di-n-hexyldiethoxysilane, di-5-hexenyldiethoxysilane, and di-5-hexenyldimethylsilane, were synthesized and used to attest to the validity of the hypothesis. The experimental results evidently proved that the Lewis base functionality enabled the functionalized α,ω-diolefin to establish dynamic electron-donating interactions with MgCl₂/TiCl₄ catalysts, making it far more effective in prompting LCB in copolymerization with propylene due to greatly enhanced polymerization reactivity of both its monomeric α-olefin and polymeric ω-olefin in their respective polymerization steps. The electronic promotion effect was found to be so robust that it could not be offset by reducing the initial α,ω-diolefin molecular steric hindrance. This approach is promising to solve the real issue of synthesizing LCB-PP by Ziegler–Natta catalyst.

中文翻译：

Ziegler–Natta催化剂将非共轭α，ω-二烯烃/丙烯共聚为长支链聚丙烯：通过引入额外的电子拉力效应克服立体阻碍

通过丙烯与非共轭α，ω-二烯烃的共聚反应合成长链支化聚丙烯（LCB-PP）是一种位阻位阻的反应过程，不仅涉及α，ω-二烯烃本身的共聚合（α-烯烃共聚合），而且还涉及衍生自第一α-烯烃共聚（ω-烯烃共聚）的聚合物烯烃中间体。当基于MgCl ₂负载的TiCl ₄（MgCl ₂ / TiCl ₄（催化剂）被认为是催化剂，其产生对烯烃单体的空间体积高度敏感的活性位点。有人提出可以通过具有路易斯碱官能团的α，ω-二烯烃官能化来克服这样的空间困难，这将带来额外的电子拉动效应，以帮助烯烃与α，ω的活性中心配位-二烯烃的单体α-烯烃和聚合的ω-烯烃聚合步骤。三个模型化合物，包括二- Ñ-己基二乙氧基硅烷，二-5-己烯基二乙氧基硅烷和二-5-己烯基二甲基硅烷被合成并用于证明该假设的有效性。实验结果清楚地证明，路易斯碱官能团使官能化的α，ω-二烯烃能够与MgCl ₂ / TiCl ₄建立动态的供电子相互作用。催化剂，由于其单体α-烯烃和聚合ω-烯烃在各自的聚合步骤中均大大提高了聚合反应活性，因此在促使LCB与丙烯共聚方面更加有效。发现电子促进作用是如此强大，以致于不能通过降低初始α，ω-二烯烃分子的空间位阻来抵消。这种方法有望解决由齐格勒-纳塔催化剂合成LCB-PP的实际问题。

更新日期：2018-11-08

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