Design and development of poly(caprolactone)-based shape-memory networks: structure-property relationships and 4D-printing

The growing interest in shape-memory polymers (SMPs) over the past decade has opened new frontiers in materials science, particularly in the field of soft robotics, which aims at developing materials capable of programmable and reversible motions triggered by external stimuli such as temperature or light. Chemically crosslinked semicrystalline polymer networks are well known for their shape-memory behavior, and increasing attention has been devoted to additive manufacturing technologies for producing customized architectures with pre-defined actuation capabilities. This thesis contributes to the advancement of SMPs by investigating the structure–property relationships governing shape-memory effects in crosslinked multi-crystalline networks, as well as by optimizing extrusion-based 4D-printing processes for the fabrication of thermo-responsive reversible actuators. In particular, the correlation between the semicrystalline topology of polymer networks and their thermo-activated shape-memory behavior was systematically studied by comparing crosslinked systems derived from blends and copolymers of poly(ε-caprolactone) (PCL) and poly(butylene succinate) (PBS). Distinct behaviors were identified: crosslinked copolymers emerged as promising materials for reversible, stress-free shape-memory applications, whereas PCL/PBS blend-based networks exhibited a pronounced one-way triple shape-memory effect. These findings provide valuable guidelines for the rational design of polymer networks tailored for specific shape-memory functionalities. Within the framework of the ERC CoDe4Bio project, in collaboration with the University of Pavia, the influence of photo-crosslinking conditions and manufacturing routes on the shape-memory properties of PCL-based systems was investigated. A comparison between film-molded and Fused Particle Fabrication (FPF). Although complex 3D-printed structures exhibiting one-way and two-way shape-memory effects under load were successfully demonstrated, reversible stress-free behavior was not achieved. Finally, during a six-month research stay at Helmholtz-Zentrum Hereon (Germany), previously developed PCL–PBS copolymer networks were further optimized. The integration of FPF with photo crosslinking enabled the fabrication of fine-tuned 3D-printed actuators capable of thermo-activated, reversible stress-free movements.