Shape-Morphing Thermoactuators: Tetrathiafulvalene-Based Polymer Networks with an Effective Phonon Conduction Pathway

The development of a shape memory polymer (SMP) with high thermal conductivity should precede the fabrication of fast-responsive soft thermoactuators because the effective heat transfer in thermoactuators expedites the shape-morphing process. A tetrathiafulvalene (TTF)-based monomer (TTF-SH) containing four flexible chains and thiol reactive functions is newly designed and synthesized for the development of SMP with excellent thermal conductivity. Thanks to the thermally induced chemical bond formation of TTF-SH from thiol to disulfide, TTF-based SMP is simply prepared without the addition of any catalyst or initiator. The TTF SMP exhibits not only high thermal conductivity (1.12 W/(m K)) but also high fixing and recovery ratios (99.42 and 99.98%). The correlation between heat transfer and shape-morphing speed of the TTF SMP is established by examining shape memory characteristics over time. The TTF SMP shows a fast shape-morphing response due to its excellent thermal conductivity. With the newly developed TTF SMP thermoactuator, we demonstrate a warning sensor to alarm the device overheating as well as a smart sunshade to automatically cut off solar energy.