Shape-Memory Effects in Biopolymer Networks with Collagen-Like Transient Nodes

In this article we study shape-memory behavior of hydrogels, formed by biodegradable and biocompatible recombinant telechelic polypeptides, with collagen like end blocks and a random coil-like middle block. The programmed shape of these hydrogels was achieved by chemical cross linking of lysine residues present in the random coil This led to soft networks; which can be stretched tip to 200% and pinned in a temporary shape by lowering the temperature and allowing the collagen like end blocks to-assemble into physical nodes, The deformed shape of the hydrogel can be maintained, at room temperature, for several days, or relaxed within a few minutes upon heating to 50 degrees C or higher. The presented hydrogels could return to their programmed shape even after several thermomechanical cycles, indicating that they remember the programmed shape. The kinetics of shape recovery at different temperatures was studied in more detail and analyzed using a mechanical model composed of two springs and a dashpot.