Structure-property relationships in multi-crystalline PCL/PBS networks: Influence of architecture on one-way and two-way shape-memory behavior

Chemically crosslinked semicrystalline networks containing multiple crystalline phases can display advanced shape-memory behavior, including multi-step one-way transitions and stress-free two-way actuation. Here, network architecture is systematically correlated with these properties in photo-crosslinked systems based on poly(ε-caprolactone) (PCL) and poly(butylene succinate) (PBS). Two series of photo-crosslinked networks were prepared: blends of dimethacrylated PCL and PBS macromonomers, and dimethacrylated PCL-PBS-PCL triblock copolymers. DSC and polarized optical microscopy show that blend networks feature well-segregated PCL and PBS phases that crystallize independently, whereas copolymer networks undergo largely coincident crystallization of the two blocks, leading to broader melting signals and modified crystallization pathways. These distinct thermal and morphological features strongly affect performance: blend networks exhibit excellent triple-shape-memory behavior with clearly separated recovery steps linked to the melting of the two phases. In contrast, copolymer networks uniquely display efficient two-way stress-free actuation, enabled by covalent interphase connectivity that enhances stress transfer during crystallization-induced elongation. This study clarifies how network constitution dictates the balance between multi-step one-way SME and reversible actuation in multi-crystalline polymer networks.