Dynamic Ablative Networks: Shapeable Heat-Shielding Materials

Thermoset materials sacrifice recyclability and reshapeability for increased chemical and mechanical robustness because of an immobilized, cross-linked polymeric matrix. The robust material properties of thermosets make them well-suited for applications such as heat-shielding materials (HSMs) or ablatives where excellent thermal stability, good mechanical strength, and high charring ability are paramount. Many of these material properties are characteristic of covalent adaptable networks (CANs), where the static connectivity of thermosets has been replaced with dynamic cross-links. This dynamic connectivity allows network mobility while retaining cross-link connectivity to permit damage repair and reshaping that are traditionally inaccessible for thermoset materials. Herein, we report the synthesis of hybrid inorganic-organic enaminone vitrimers that contain an exceptionally high weight percent of polyhedral oligomeric silsesquioxane (POSS)-derivatives. Polycondensation of beta-ketoester-containing POSS with various diamine cross-linkers led to materials with facile tunability, shapeability, predictable glass transition temperatures, good thermal stability, and high residual char mass following thermal degradation. Furthermore, the char materials show notable retention of their preordained shape following decomposition, suggesting their future utility in the design of HSMs with complex detailing.

Automated summary

Thermoset materials sacrifice recyclability and reshapeability for increased chemical and mechanical robustness. However, the static connectivity of thermosets has been replaced with dynamic cross-links in covalent adaptable networks (CANs), which allows for damage repair and reshaping. Hybrid inorganic-organic enaminone vitrimers with high weight percent of polyhedral oligomeric silsesquioxane (POSS) derivatives were synthesized, showing tunability, shapeability, predictable glass transition temperatures, thermal stability, and retention of preordained shape following decomposition. These materials have potential applications in heat-shielding materials (HSMs) with complex detailing.