LCC, CNRS & University of Toulouse (UPS, INPT), 205 route de Narbonne, 31077, Toulouse, France.
CIRIMAT, CNRS & University of Toulouse (UPS, INPT), 118 Route de Narbonne, 31062, Toulouse, France.
Adv Mater. 2018 Feb;30(8). doi: 10.1002/adma.201705275. Epub 2018 Jan 8.
Spin crossover particles of formula Fe{(Htrz) (trz)} (NH -trz) and average size of 20 nm ± 8 nm are homogeneously dispersed in poly(vinylidene fluoride-co-trifluoro-ethylene), P(VDF-TrFE), and poly(vinylidene fluoride) (PVDF) matrices to form macroscopic (cm-scale), freestanding, and flexible nanocomposite materials. The composites exhibit concomitant thermal expansion and discharge current peaks on cycling around the spin transition temperatures, i.e., new "product properties" resulting from the synergy between the particles and the matrix. Poling the P(VDF-TrFE) (70-30 mol%) samples loaded with 25 wt% of particles in 18 MV m electric field results in a piezoelectric coefficient d = -3.3 pC N . The poled samples display substantially amplified discharges and altered spin transition properties. Analysis of mechanical and dielectric properties reveals that both strain (1%) and permittivity (40%) changes in the composite accompany the spin transition in the particles, giving direct evidence for strong electromechanical couplings between the components. These results provide a novel route for the deployment of molecular spin crossover materials as actuators in artificial muscles and generators in thermal energy harvesting devices.
具有化学式 Fe{(Htrz)(trz)} (NH -trz) 的自旋交叉粒子，平均粒径为 20nm ± 8nm，均匀分散在聚(偏二氟乙烯-三氟乙烯) (P(VDF-TrFE))和聚偏二氟乙烯 (PVDF) 基质中，形成宏观的(cm 尺度)、独立的、灵活的纳米复合材料。这些复合材料在围绕自旋转变温度的循环过程中表现出热膨胀和放电电流峰值的同时出现，即由于颗粒和基质之间的协同作用而产生的新的“产品性能”。在 18 MV m 电场中对负载有 25wt%颗粒的 P(VDF-TrFE)(70-30 mol%)样品进行极化，得到压电系数 d = -3.3 pC N 。极化后的样品显示出明显增强的放电和改变的自旋转变特性。对力学和介电性能的分析表明，复合材料的应变(1%)和介电常数(40%)变化都伴随着颗粒中的自旋转变，这为组件之间的强机电耦合提供了直接证据。这些结果为将分子自旋交叉材料作为人工肌肉中的致动器以及在热能收集装置中的发电机的应用提供了新途径。
