Ring-opening metathesis polymerization (ROMP) of norbornenyl macromonomers (MM) has become a preferred method to synthesize bottlebrush (BB) polymers with perfect grafting density. Prior investigations had established that fast ROMP rates were necessary to synthesize clean BB polymers and that the chemical structure of the anchor group linking the MM polymeric chain and norbornene unit had the most influence on the rate of ROMP. While the order of fastest anchor groups was predicted to be a general trend across all MM chemistry, we observed that the fastest anchor group for a poly(propylene oxide) (PPO) MM is not the fastest for a poly(lactic acid) (PLA) MM. From our kinetic analysis, we showed that PLA MMs are faster with a methylene linker and that PPO MMs are faster with a dicarboximide linker. Interestingly, however, the fast rate of the dicarboximide PPO MM did not lead to the synthesis of a PPO BB polymer with lower dispersity. While the root cause for this MM chemistry sensitivity is still unclear, this study shows that despite being far from the reactive group of the norbornene unit, the chemical structure of MM polymeric chain influences the rate of ROMP beyond the anchor group chemistry.

中文翻译：

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大分子单体化学结构对开环复分解接枝聚合速率的影响


降冰片烯基大分子单体 （MM） 的开环复分解聚合 （ROMP） 已成为合成具有完美接枝密度的瓶刷 （BB） 聚合物的首选方法。先前的研究已经确定，合成干净的 BB 聚合物需要快速的 ROMP 速率，并且连接 MM 聚合物链和降冰片烯单元的锚基的化学结构对 ROMP 速率的影响最大。虽然预测最快的锚基团的顺序是所有 MM 化学的普遍趋势，但我们观察到聚（环氧丙烷）（PPO） MM 的最快锚基团并不是聚乳酸（PLA） MM 的最快锚基团。从我们的动力学分析中，我们表明 PLA MMs 使用亚甲基连接子更快，而 PPO MM 使用二羧酰亚胺连接子更快。然而，有趣的是，双羧酰亚胺 PPO MM 的快速速率并未导致合成分散性较低的 PPO BB 聚合物。虽然这种 MM 化学敏感性的根本原因尚不清楚，但这项研究表明，尽管与降冰片烯单元的反应性基团相去甚远，但 MM 聚合物链的化学结构会影响锚基化学之外的 ROMP 速率。