Yoon Ki-Young, Noh Jinkyung, Gan Quan, Edwards Julian P, Tuba Robert, Choi Tae-Lim, Grubbs Robert H
Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA.
Ashland Specialty Ingredients, Bridgewater, NJ, USA.
Nat Chem. 2022 Nov;14(11):1242-1248. doi: 10.1038/s41557-022-01034-8. Epub 2022 Sep 5.
Cyclic polymers are topologically interesting and envisioned as a lubricant material. However, scalable synthesis of pure cyclic polymers remains elusive. The most straightforward way is to recover a used catalyst after the synthesis of cyclic polymers and reuse it. Unfortunately, this is demanding because of the catalyst's vulnerability and inseparability from polymers, which reduce the practicality of the process. Here we develop a continuous circular process, where polymerization, polymer separation and catalyst recovery happen in situ, to dispense a pure cyclic polymer after bulk ring-expansion metathesis polymerization of cyclopentene. It is enabled by introducing silica-supported ruthenium catalysts and newly designed glassware. Different depolymerization kinetics of the cyclic polymer from its linear analogue are also discussed. This process minimizes manual labour, maximizes the security of vulnerable catalysts and guarantees the purity of cyclic polymers, thereby showcasing a prototype of a scalable access to cyclic polymers with increased turnovers (≥415,000) of precious catalysts.
环状聚合物在拓扑结构上很有趣，并被设想为一种润滑材料。然而，纯环状聚合物的可扩展合成仍然难以实现。最直接的方法是在环状聚合物合成后回收使用过的催化剂并重新使用。不幸的是，这很困难，因为催化剂易受影响且与聚合物难以分离，这降低了该过程的实用性。在此，我们开发了一种连续循环过程，其中聚合、聚合物分离和催化剂回收在原位进行，以便在环戊烯的本体开环易位聚合后得到纯环状聚合物。这是通过引入二氧化硅负载的钌催化剂和新设计的玻璃器皿实现的。还讨论了环状聚合物与其线性类似物不同的解聚动力学。该过程最大限度地减少了人工操作，最大限度地提高了易受影响催化剂的安全性，并保证了环状聚合物的纯度，从而展示了一种可扩展获得环状聚合物的原型，其中珍贵催化剂的周转率提高（≥415,000）。
