Domain memory effect in the organic ferroics

Abstract

Shape memory alloys have been used extensively in actuators, couplings, medical guide wires, and smart devices, because of their unique shape memory effect and superelasticity triggered by the reversible martensitic phase transformations. For ferroic materials, however, almost no memory effects have been found for their ferroic domains after reversible phase transformations. Here, we present a pair of single-component organic enantiomorphic ferroelectric/ferroelastic crystals, (R)- and (S)-N-3,5-di-tert-butylsalicylidene-1-(1-naphthyl)ethylamine SA-NPh-(R) and SA-NPh-(S). It is notable that not only can their ferroic domain patterns disappear and reappear during reversible thermodynamic phase transformations, but they can also disappear and reappear during reversible light-driven phase transformations induced by enol–keto photoisomerization, both of which are from P1 to P21 polar space groups. Most importantly, the domain patterns are exactly the same in the initial and final states, demonstrating the existence of a memory effect for the ferroic domains in SA-NPh-(R) and SA-NPh-(S). As far as we are aware, the domain memory effect triggered by both thermodynamic and light-driven ferroelectric/ferroelastic phase transformations remains unexplored in ferroic materials. Thermal and optical control of domain memory effect would open up a fresh research field for smart ferroic materials.

Photochromic Single-Component Organic Fulgide Ferroelectric with Photo-Triggered Polarization Response

“…Besides, the low photoisomerization conversion of the fulgide bulk crystal may also lead to less difference for their ferroelectric loops. Similar situations have been found in previously reported photoswitchable salicylideneaniline Schiff base ferroelectric crystals. − The intensity of the SHG signal for polycrystalline powder of 1E was recorded showing slight and reversible changes before and after light irradiation (Figure S11), which should correlate with the structural photoisomerization between the initial and excited states. PFM is a surface technique based on scanning probe microscopy.…”

“… Photoreaction mainly occurs at the solid sample surface but not in the core because UV light can hardly penetrate the bulk of the crystals. This commonly happens in the case of other photochromic salicylideneaniline Schiff base ferroelectrics. − As shown in Figure a (inset), the color of 1E and 1Z shows reversible changes between yellow and red under 365 and 488 nm light irradiation. The photochromism phenomenon was then recorded by solid-state UV–vis absorption spectra.…”

“…Such light-induced structural isomerization can produce electronic as well as geometrical structure changes in the molecule, which may result in repositioning the orientation of the ferroelectric domains/polarization, under the premise of ensuring a polar point group in the crystal . Very recently, optical control of polarization switching has been pioneeringly achieved in single-component photochromic organic ferroelectric salicylaldehyde Schiff base and diarylethene derivative crystals. − Such optical manipulation of polarization is of milestone significance in the development of ferroelectrics. However, the study of such photo-triggered ferroelectric polarization response by photoisomerization is still in its infancy and relatively scarce.…”

Switchable Dielectric Two-Dimensional Lead-Free Perovskite with Reversible Thermochromic Response

“…Stimuli-responsive switchable hybrid perovskite materials display reversible color changes, fluorescence, phase transition, or other physical properties under external stimulations, including temperature, light, pressure, and electricity, and play an important role in energy-saving and environmental protection. − Besides, these materials also have great potential for applications in smart windows, storage devices, sensors, optoelectronic devices, switch operations, and so on. − Among them, thermochromic hybrid perovskites, possessing the interesting stimulation response of color change under varying temperatures, have emerged as good candidates due to their wide applications in smart temperature coatings, colored clothing, smart stealth materials, and temperature sensors. − Generally, thermochromism, caused by phase transition or vibronic coupling, is a notable color-change phenomenon and is often present in Cu-based and Pb-based hybrid perovskites. − More glaringly, compared with the high toxicity of Pb-based perovskites, Cu-based perovskites are excellent candidates for thermochromic materials. The 2D [CuX 4 ] 2– layers were separated by the organic cations in 2D OIHPs. , As a result of the Jahn–Teller effect, two of the six Cu–X bonds are longer than the others combining with the distorted [CuX 4 ] 2– layer, which result in additional flexibility of the inorganic framework .…”

Nicotinic acid bromide: a simple organic salt optical-electrical ferroelastic with highTc

“…Organic ferroelastics have received special attention due to their advantages of diverse chemical composition, easy preparation, low-cost and so on. 14–16 Moreover, they have some advantages of simple structure, being metal-free, and simple synthetic method. The Curie temperature ( T c ) range limits the application of ferro materials and the property of high T c allows the materials to maintain stability at relatively high temperatures.…”