Shape memory and self‐healing behavior of styrene–butadiene–styrene/ethylene‐methacrylic acid copolymer (SBS/EMAA) elastomers containing ionic interactions

Ionic interactions were introduced to styrene–butadiene–styrene (SBS) through blending with ethylene‐methacrylic acid copolymer (EMAA) and zinc oxide (ZnO), and a following in situ neutralization reaction between the carboxyl groups of EMAA and ZnO. The resultant SBS/EMAA (60/40 wt %) blends containing zinc carboxylate crosslinks exhibited high modulus and strong long‐time relaxation characteristics. With 74% of the carboxyl groups neutralized (zinc cation fraction of 1.7 wt %), the tensile strength of the blends was increased from 14.6 to 16.6 MPa, and the stress at 100% extension was increased from 4.8 to 8.1 MPa. The melting temperature of EMAA was utilized to trigger the shape memory behavior of SBS/EMAA, and the reversible ionic bonds endowed SBS with better shape memory and self‐healing performance. The shape‐fixing ratio and recovery ratio of SBS were increased from 90.2 and 56.5% up to 93.3 and 84.2%, respectively. When the cut surfaces of SBS/EMAA/Zn samples were brought back into contact and annealed at 100 °C for 1 h, the strength and the elongation at break were recovered by 36 and 21%, respectively. This introduction of ionic interactions through the EMAA‐ZnO neutralization reactions imparts new functions to SBS thermoplastic elastomers.