Triple and Two-Way Reversible Shape Memory Polymer Networks with Body Temperature and Water Responsiveness

Shape memory polymers (SMPs), as a class of intelligent materials, have shown great potential in biomedical and robotic fields. Although efforts have been made to design and fabricate SMPs in the past decades, most of the SMPs are not suitable for use in the human body due to their unpleasant triggering conditions. Furthermore, it is of great importance to diversify the shape memory effect (SME) of SMPs to extend their applications. In this work, through thiol-ene chemistry, SMPs based on random cross-linked hydrophobic polytetrahydrofuran (PTHF) and hydrophilic poly(ethylene glycol) (PEG) oligomers were facilely fabricated. These SMPs showed a body temperature-triggered two-way SME with a reversible strain of up to 25.2%. Besides, the SMPs exhibited a good body temperature- and water-triggered one-way triple-SME. These features bestowed the polymers with a bright future in biomedical applications. Polymer P60-G40 was applied as a new type of esophageal stent, and the in vitro assessment showed that the stent was adjustable, self-expandable, and had the ability to release drugs, which were attributed to the one-way triple-SME and two-way SME.