Main‐Chain Linear Polyrotaxanes: Synthesis,Characterization, and Conformational Modulation

Two functional main‐chain linear polyrotaxanes, one a covalent polymeric chain that threads through many macrocycles ( P1 ) and the other a polyn]rotaxane chain that is composed of many repeating rotaxane units ( P2 ), were synthesized by employing strong crown‐ether/ammonium‐based ( DB24C8 / DBA ) host–guest interactions and click chemistry. Energy transfer between the wheel and axle units in both polyrotaxanes was used to provide insight into the conformational information of their resulting polyrotaxanes. Steady‐state and time‐resolved spectroscopy were performed to understand the conformation differences between polymers P1 and P2 in solution. Additional investigations by using dynamic/static light scattering and atomic force microscopy illustrated that polymer P1 was unbending and had a rigid rod‐like structure, whilst polymer P2 was curved and flexible. This flexible topology facilitated the self‐assembly of polymer P2 into relatively large ball‐shaped particles. In addition, the energy transfer between the wheel and axle units was controlled by the addition of specific anions or base. The anion‐induced energy enhancement was attributed to a change in electrostatic interactions between the polymer chains. The base‐driven molecular shuttle broke the DB24C8 / DBA host–guest interactions. These results confirm that both intra‐ and intermolecular electrostatic interactions are crucial for modulating conformational topology, which determines the assembly of polyrotaxanes in solution.