Shape Memory Behavior of a Polyethylene-Based Carboxylate Ionomer

Shape memory behavior of a partially zinc-neutralized, poly(ethylene-co-methacrylic acid) ionomer was investigated. The ionomer was a semicrystalline ionomer with a broad melting transition in the range 60–100 °C. Physical crosslinks in the ionomer due to an ionic nanodomain structure provided a “permanent” crosslinked network, while polyethylene crystallinity provided a temporary network. The broad melting transition allowed one to tune the dual-shape memory behavior by choosing a switching temperature, T c, anywhere within the melting transition. Similarly, multiple-shape memory behavior was achieved by choosing two or more switching temperatures within the melting transition, though the effectiveness of fixing ( F ) depended on how much material was melted and recrystallized to support the specific temporary shape. Crosslinking improved the recovery efficiency ( R ), and the crosslinked ionomer exhibited nearly ideal shape memory behavior in the dual-shape memory cycle.