Mechanically Tunable Slide-Ring Polymers via Photo-Regulated Topological Control

Post-synthetic dynamic control of polymer topology to modulate material properties on demand remains a grand challenge in polymer science. Here, we demonstrate a light-responsive slide-ring polymer network whose mechanical properties can be tuned through photoisomerization of incorporated azobenzene units. In the trans-state, azobenzene enables unhindered sliding of macrocycles along the polymer backbone, yielding a softer, more ductile material. UV-induced switching to the sterically demanding cis-configuration restricts ring mobility, thereby increasing the Young's modulus by two-fold while reducing toughness. Control experiments with noninterlocked analogs revealed the opposite mechanical response—light-induced softening—highlighting the pivotal role of topology in property regulation. Furthermore, the azobenzene linkage confers controlled degradability under mild conditions. This work establishes a versatile strategy for post-synthetic topological control via molecular photoswitches, enabling the design of adaptive polymers with stimuli-responsive mechanical properties for applications in smart materials.