A review of shape memory polymers based on the intrinsic structures of their responsive switches.

Shape memory polymers (SMPs), as stimuli-responsive materials, have attracted worldwide attention. Based on the history and development of SMPs, a variety of reports about SMPs in recent years are summarized in this paper. The responsive switches are analyzed and divided into two kinds according to their intrinsic structures: physical switch and chemical one. Then, detailed classification and comprehensive discussion of SMPs are further elaborated, based on the intrinsic structures of responsive switches and stimulation types. Finally, the development and prospect of SMPs are objectively predicted and forecasted.