A high-temperature supramolecular-based switchable dielectric material with electrical bistability between high and low dielectric states

摘要

One new hybrid supramolecular- based phase transition compound TAPC containing macrocycle stator with electrical bistability between high and low dielectric states (TAPC =[(TAP-NH3)center dot(18-crown-6) (0.5-H2O)] (H2O)]center dot(2ClO(4)) (1), TAP-NH3 = 4-ammonio-2,2,6,6-tetramethylpiperidinium) has been prepared and characterized by variable-temperature crystal structure determination, elemental analysis, differential scanning calorimetry (DSC) and temperature-dependent dielectric spectroscopy. The DSC measurement showed a pair of sharp peaks at 357 K (heating) and 322 K (cooling), indicating that TAPC undergoes a reversible first-order phase transition. The crystal structures obtained at 293 K and 368 K are both monoclinic in the P21/m space group. The most distinct difference between room-temperature and high-temperature structures is the order-disorder transition of the ClO4- anions and the displacement of the guest water molecules, which are the driving forces of the high-temperature phase transition with electrical bistability (two incentives that synergistically induced the phase transition). This functional moiety could be a cation/anion or guest molecule solely, observed in a lot of compounds, and very few of them belong to the collaborative type (order-disorder motion and displacement) with high-temperature dielectric phase transitions. In addition, the large thermal hysteresis of 37.2 K contributes to a widely tunable transition between high and low dielectric states. Such distinctive dielectric performance suggests that 1 might be a potential hightemperature switchable dielectric material.