Ionic cocrystals with hydrogen bonding can form exciting materials with enhanced optical and electronic properties. We present a highly moisture-stable ammonium salt cocrystal [CH₃C₆H₄CH(CH₃)NH₂][CH₃C₆H₄CH(CH₃)NH₃][PF₆] ((p-TEA)(p-TEAH)·PF₆) crystallizing in the polar monoclinic C2 space group. The asymmetry in (p-TEA)(p-TEAH)·PF₆ was induced by its chiral substituents, while the polar order and structural stability were achieved by using the octahedral PF₆^– anion and the consequent formation of salt cocrystal. The ferroelectric properties of (p-TEA)(p-TEAH)·PF₆ were confirmed through P–E loop measurements. Piezoresponse force microscopy (PFM) enabled the visualization of its domain structure with characteristic “butterfly” and hysteresis loops associated with ferro- and piezoelectric properties. Notably, (p-TEA)(p-TEAH)·PF₆ exhibits a large electrostrictive coefficient (Q₃₃) value of 2.02 m⁴ C^–2, higher than those found for ceramic-based materials and comparable to that of polyvinylidene difluoride. Furthermore, the composite films of (p-TEA)(p-TEAH)·PF₆ with polycaprolactone (PCL) polymer and its gyroid-shaped 3D-printed composite scaled-up device, 3DP-Gy, were prepared and evaluated for piezoelectric energy-harvesting functionality. A high output voltage of 22.8 V and a power density of 118.5 μW cm^–3 have been recorded for the 3DP-Gy device. Remarkably, no loss in voltage outputs was observed for the (p-TEA)(p-TEAH)·PF₆ devices even after exposure to 99% relative humidity, showcasing their utility under extremely humid conditions.

中文翻译：

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高电致伸缩盐共晶及其3D打印聚合物复合材料在压电纳米发电机中的应用


具有氢键的离子共晶可以形成具有增强的光学和电子性能的令人兴奋的材料。我们提出了一种高度水分稳定的铵盐共晶 [CH ₃ C ₆ H ₄ CH(CH ₃ )NH ₂ ][CH ₃ C ₆ H ₄ CH(CH ₃ )NH ₃ ] [PF ₆ ] ((p-TEA)(p-TEAH)·PF ₆ ) 在极性单斜晶系 C2 空间群中结晶。 (p-TEA)(p-TEAH)·PF ₆ 的不对称性是由其手性取代基引起的，而极性有序和结构稳定性是通过八面体 PF ₆ 实现的 ^– 阴离子和随后形成的盐共晶体。通过P-E环路测量证实了(p-TEA)(p-TEAH)·PF ₆ 的铁电特性。压电响应力显微镜 (PFM) 使其域结构可视化，具有与铁和压电特性相关的特征“蝴蝶”和磁滞回线。值得注意的是，(p-TEA)(p-TEAH)·PF ₆ 表现出 2.02 m 的大电致伸缩系数 (Q ₃₃ ) 值 ⁴ C ^–2 ，高于陶瓷基材料，与聚偏二氟乙烯相当。此外，还制备了(p-TEA)(p-TEAH)·PF ₆ 与聚己内酯(PCL)聚合物的复合薄膜及其螺旋状3D打印复合材料放大装置3DP-Gy。准备并评估压电能量收集功能。 3DP-Gy 器件记录了 22.8 V 的高输出电压和 118.5 μW cm ^–3 的功率密度。 值得注意的是，即使暴露在 99% 的相对湿度下，(p-TEA)(p-TEAH)·PF ₆ 器件也没有观察到电压输出损失，这展示了它们在极端潮湿条件下的实用性。