Structural control of self-healing silica–poly(tetrahydropyran)–poly(ε-caprolactone) hybrids

In some biomaterial applications, the device needs to resist cyclic loading. Recently, self-healing hybrid systems with interpenetrating network of organic and inorganic components have been discovered. In this work, we clarify the structure-mechanical property relations in a new series of silica-poly(tetrahydropyran)-poly(ε-caprolactone) (SiO₂-PTHP-PCL) materials, which were prepared through a three-step synthesis, including one-pot cationic ring-opening polymerization, sol-gel reaction, and polymer-silica cross condensation. We applied THP as the main constituent of the organic phase and achieved successful polymerization under mild conditions, while the hybrid structures were controlled by the degree of silica-crosslinking and the organic/inorganic ratio. The thermal stabilities, densities, Young's modulus as well as hardness could also be regulated through such control. Notably, we find that the hybrid materials with organic polymer content above 73% are able to self-heal induced damages, including under body temperature conditions and the mechanical properties of the self-healed material are similar to those of the fresh samples. We ascribe this primarily to the reversible intermolecular interactions and hydrogen bonding among the polymer chains. Finally, we discover that the PTHP-SiO₂networks are stable in a simulated bio-environment although PCL underwent biodegradation. The present structural control approach could lead to the design of tailored functional hybrid materials, with potential applications within areas such as soft robotics and bone regeneration.