Competing Crystallization and Cross-Linking Behavior in Multifunctional Poly(ε-Caprolactone)-Based Dynamic Covalent Networks

Dynamic covalent networks (DCNs) combine thermoset-like performance with thermoplastic reprocessability through dynamic covalent chemistry. Their properties are dictated by their microstructure, which is determined by the interplay between reversible covalent reactions and fixation mechanisms, such as crystallization. Here, the interplay of crystallization and cross-linking in poly(ε-caprolactone)-based DCNs is investigated by varying PCL precursor functionality from linear 2-functional to star-shaped 4- and 6-functional architectures. This design enables distinct cases ranging from linear chain extension to network formation occurring on similar time scales as crystallization. Nonisothermal and isothermal studies reveal that cross-linking slows down crystallization, lowers crystallization peak temperatures, and promotes secondary crystallization. Morphological analysis shows more irregular spherulites, while kinetic evaluation confirms adverse effects of cross-linking on both nucleation and crystal growth, except in short linear chains where nucleation is enhanced. In that case, molecular weight effects during cross-linking are likely to dominate the crystallization behavior. These results provide structural insight into tailoring crystallizable DCNs.