[nanoPost] Shape-memory polymers

Research Centre Germany

Shape-memory polymers are an emerging class of active polymers, having the capability of changing their shape between distinctive shapes. When exposed to an appropriate stimulus they can change their shape in a predefined way from shape (A) to a shape (B). While shape (B) is given by the initial processing step, shape (A) is determined by applying a process called programming.

Initially founded on the thermally-induced dual shape-effect the concept of shape-memory polymers has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups on the molecular level. By the incorporation of reversibly photoreacting molecular switches, light-induced stimulation of shape-memory polymers has been realized.

Remote actuation of the thermally-induced shape-memory effect in magnetic fields was enabled by the incorporation of magnetic nanoparticles of iron(III)oxide cores in a silica matrix into shape-memory thermoplasts (figure 2). Here the sample temperature is increased by inductive heating of the nanoparticles in an alternating magnetic field.

Complex movements of shape-memory polymers had been realized by triple-shape polymers. Here the incorporation of second switching segment into the molecular architecture of the shape-memory polymer network enabled three distinctive shapes.