Melt Recyclable Shape Memory Elastomers through Main Chain Association

Shape memory (SM) elastomers can undergo triggered actuation from metastable, deformed states to permanent shapes, offering diverse applications. Covalently crosslinked, semicrystalline SM networks are capable of storing large amounts of elastic energy (>3 MJ/m³) with full recovery, however, these materials cannot be melt-processed or recycled. Here, we demonstrate that replacing covalent crosslinks with hydrogen bond interactions can enable fully melt recyclable SM elastomer with little performance loss. Two high molecular weight poly(caprolactone)s with interchain hydrogen bonding groups have been synthesized and show excellent strain fixation and shape recovery both before and after shredding, melt-pressing, and reannealing. Dynamic mechanical analysis reveals a stiffness plateau that persists to temperatures above the shape-triggering temperature. Stress relaxation studies suggest chain disentanglement is the primary relaxation mode. Disentanglement is sluggish just above the trigger temperature and is much faster at higher temperatures where plastic flow can occur. The role of the polymers’ hard segment associative strength and a first-cycle training effect are under continued investigation.