Polyisobutylene (PIB)-based bottlebrush polymers were synthesized via ring-opening metathesis polymerization (ROMP) of norbornene- and oxanorbornene-terminated PIB macromonomers (MM) initiated by Grubbs third-generation catalyst ((H₂IMes₂)(pyr)₂(Cl)₂Ru═CHPh) (G3). While both MMs reached greater than 97% conversion as measured by ¹H NMR, the rate of propagation of PIB norbornene was measured to be 2.9 times greater than that of PIB oxanorbornene MMs of similar molecular weight (MW). The slower rate of propagation of the oxanorbornene MM was attributed to interaction between the electron-rich oxygen bridge and the metal center of G3, which slowed but did not inhibit polymerization. Both types of MMs demonstrated controlled/“living” polymerization behavior, and brush polymers with MWs up to ∼700 kg/mol with narrow dispersity (Đ ≤ 1.04) were achieved.

中文翻译：

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开环复分解聚合法合成聚异丁烯瓶刷聚合物

通过第三代催化剂（（H ₂ IMes ₂）（pyr）₂（G）引发的降冰片烯和氧杂降冰片烯封端的PIB大单体（MM）的开环易位聚合（ROMP），合成了基于聚异丁烯（PIB）的牙刷聚合物。CL）₂ Ru═CHPh）（G3）。虽然两个MM的转化率均大于97％（按¹来衡量）在1 H NMR中，测得PIB降冰片烯的扩散速率是分子量相似（MW）的PIB氧杂降冰片MM的2.9倍。氧杂降冰片烯MM的传播速度较慢归因于富电子的氧桥与G3的金属中心之间的相互作用，这种相互作用减慢了但不抑制聚合。这两种类型的MM的证实受控/“活性”聚合行为，刷状聚合物与兆瓦高达~700千克/摩尔具有窄分散度（Đ ≤1.04）得以实现。