Reversible Thermosalience in a One-Dimensional Coordination Polymer Preceded by Anisotropic Thermal Expansion and the Shape Memory Effect

Abstract

Thermally responsive crystals hold great potential for their use as actuating materials by acting as energy transducers to convert heat energy to mechanical work. Control over defined phase transition temperature with rapid reconfiguration is of great advantage for actuation. The thermosalient (TS) effect is a rarely observed phenomenon in coordination polymers (CPs), let alone the reversibility of thermosalience in CPs. Herein, we report the reversible TS effect in a one-dimensional CP due to the martensitic phase transition during both heating and cooling cycles. The TS effect was preceded by anisotropic thermal expansion showing high expansion coefficients. In addition, the nonmolecular crystals show reversible contraction and recovery during multiple heating-cooling cycles due to the self-restorative shape memory effect. The reversible actuation of the CP could be repeated for 20 heating-cooling cycles in differential scanning calorimetry experiments, suggesting its great potential as a multicyclic actuator. Such thermal responsive behavior is unique in metal-organic materials.