Shape Programming through Hierarchic Crystallization of Semicrystalline Elastomers*

Hierarchic organization of semi-crystalline morphology has proved to be key to encoding different shapes at different stages of the crystallization process. We have studied shape transformations as a new tool to gain insights of a crystallization process and then translated the hierarchic crystallization into programmable shape transformations. Reversible transitions between multiple shapes has been achieved through partial melting of a crystalline scaffold, leaving a latent template, which inverts shape recovery by steering crystallization along kinetically preferred pathways replicating the scaffold. A composite model has been applied to interpret the relationship between shape, elastic modulus and crystallinity of semi-crystalline elastomers, assuming morphological transition between isolated crystallites, clusters, and percolated scaffold.