Mechanochromic Building Blocks with a Dynamic Chemical Cross-Linking Network in Shape Memory Polycaprolactone: A Model Strategy for Integrating Reversibility, Repeatability, and Recoverability into a Single Multiresponsive Material

To date, various responsive behaviors in solution states, such as thermal, pH, and light responsiveness, have been reported. However, achieving multiresponsive functionalities in bulk materials, especially those that are reversible, repeatable, and self-healable, remains a challenge once damaged or torn apart by external stimuli. This study presents a strategy combining mechanochromic and dynamic covalently bonded building blocks at both network points and soft segments of a shape memory polymer (SMP) to create a bulk material with multiresponsive capabilities. By employing polycaprolactone (PCL) as the SMP matrix with a switching segment containing spiropyran (SP) and network point branching units based on furan-maleimide Diels–Alder (DA) chemistry, the resulting material exhibits mechanochromic color changes under mechanical stress, shape recovery due to the SMP effect, and self-healing through thermally triggered reversible DA reactions. This work demonstrates simultaneous color change, shape memory, and self-healing properties, enabled by the functions of each building block.