Design strategies for shape memory polymers

Shape memory polymers (SMPs) are polymeric materials capable of recovering from a 'fixed' temporary shape to a 'memorized' permanent shape upon exposure to an external stimulus. Two structural elements are required for a polymer to exhibit useful shape memory: a network structure that defines the permanent shape (the 'memory'), and a switching segment that induces a significant change in the mobility of the network chains. Four common strategies based on various chemical/physical principles and with different advantages/disadvantages have been established for the design and preparation of SMPs. A new design strategy, based on the concept of functional composite materials, allows for a greater control over material properties and functions and has shown great promise in designing SMPs for a wide variety of applications.