Shape Memory Polymer

Shape Memory Polymers (SMPs) are polymeric materials which have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger), such as e.g. temperature change.

Besides temperature change, as in the case of thermally activated SMPs, specific SMPs can also be triggered by an electric or magnetic field, light or a change in pH. As well as polymers in general, SMP also cover a wide property-range from stable to biodegradable, from soft to hard and from elastic to rigid depending on the structural units that constitute the SMP. SMP include thermoplastic and thermoset (covalently cross-linked) polymeric materials. Shape memory polymers differ from shape memory alloys by their glass transition or melting transition from a hard to a soft phase which is responsible for the shape memory effect. In shape memory alloys Martensitic/Austenitic transitions are responsible for the shape memory effect.

The most recent developments are triple shape memory materials which can store two shapes in memory.