Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan).
Angew Chem Int Ed Engl. 2015 Jun 1;54(23):6770-4. doi: 10.1002/anie.201500578. Epub 2015 Apr 17.
Topology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three-armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring-opening polymerization of δ-valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end-capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane-linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N-acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity.
首次展示了星型聚合物到线型聚合物的拓扑转变。通过具有三个羟基的假[2]轮烷作为引发剂位点在轮组分和轴两端引发δ-戊内酯的活性开环聚合，合成了具有两个聚合物链机械连接的三臂星型聚合物。聚合后，用大体积异氰酸酯进行聚合端封反应，不仅可以防止轮组件滑脱，还可以在轴末端引入氨酯部分。所得的基于铵/冠醚相互作用的固定轮烷键的轮烷连接星型聚合物进行铵部分的 N-乙酰化，将各组分从相互作用中释放出来，使轮组件移动到氨酯末端作为相互作用位点，最终得到线型聚合物。通过流体力学体积和粘度证实了由本拓扑转变引起的物理性质变化。
