Shape- and Color-Switchable Polyurethane Thermochromic Actuators Based on Metal-Containing Ionic Liquids

Abstract

Many creatures have excellent control over their form, color, and morphology, allowing them to respond to the interaction of environmental stimuli better. Here, the bioinspired synergistic shape–color-switchable actuators based on thermally induced shape-memory triethanolamine cross-linked polyurethane (TEAPU) and thermochromic ionic liquids (ILs) were prepared. The thermochromic ILs with various metalized anions, including bis­(1-butyl-3-methylimidazolium) tetrachloro nickelate ([Bmim]2[NiCl4]) and bis­(1-butyl-3-methylimidazolium) tetrachloride cobalt ([Bmim]2[CoCl4]), are investigated. The actuators exhibit thermochromic response, as evidenced by a shift in the color of the composites, which is due to the formation of the tetrahedral complex MCl4 2– (M = Ni and Co) after dehydration. The shape–color-switchable thermochromic actuators have strong molecular interaction between TEAPU and ILs and can mimic natural flowers and change the color and shape quickly in a narrow temperature range (30–70 °C). In addition, these thermochromic actuators can lift more than 50 times their weight and withstand strains of more than 1100%. The results represent the potential application in artificial muscle actuators and intelligent camouflages.

Development of Leather Fiber/Polyurethane Composite with Antibacterial, Wet Management, and Temperature-Adaptive Flexibility for Foot Care

“…The two bands observed between 2939 and 2854 cm –1 are attributed to symmetric and nonsymmetric stretching of the C–H bond with carbonyl . Sharp absorption peaks at 1713 and 1238 cm –1 are typical bands for the stretching vibrations of CO and C–O (from −N–CO−), respectively . The peak at 1535 cm –1 is associated with the bending vibration of N–H (from −CONH−) .…”

“…15 Sharp absorption peaks at 1713 and 1238 cm −1 are typical bands for the stretching vibrations of C�O and C−O (from −N−CO−), respectively. 16 The peak at 1535 cm −1 is associated with the bending vibration of N−H (from −CONH−). 17 A broad and strong peak at 1100 cm −1 is attributed to ether bond C−O−C stretching.…”

Poly(ionic liquid)‐Based Energy and Electronic Devices

“…[ 51 ] Recently, we synthesized a series of shape‐color‐switchable actuators based on triethanolamine cross‐linked polyurethane (TEAPU) and thermochromic ILs with various metalized anions, including bis(1‐butyl‐3‐ methylimidazolium) tetrachloro nickelate ([Bmim] 2 [NiCl 4 ]) and bis(1‐butyl‐3‐methylimidazolium) tetrachloride cobalt ([Bmim] 2 [CoCl 4 ]) (Figure 5). [ 52 ] The shape recovery properties are mainly originated from the TEAPU, and the thermochromic responses are majorly ascribed to the formation of the tetrahedral complex MCl 4 2– (M = Ni or Co) after dehydration. These fascinating works provide new routes for the diverse functionality application of PILs in advanced sensors and functional materials for the inscription of information.…”

“…Color fading happens when the composite films are cooled to the phase transition temperature due to octahedron (O h ) to tetrahedron (T d ) conversion of [Bmim] 2 [MCl 4 ] and shape memory because of polycaprolactone, which is reversible after heating. [ 52 ]…”

Three-Dimensional Printable, Highly Conductive Ionic Elastomers for High-Sensitivity Iontronics

“…Different from electronic conductors, ionic conductors transmit signals by ion migration. − Hydrogels are the most frequently studied ionic conductors due to their high flexibility and transparency, but their applications are limited because of the evaporation of water at high temperatures and its crystallization at low temperatures. , The water retention capacity can be improved by incorporating a salt into the hydrogel, , but it cannot prevent the dehydration of hydrogels under long-term work. Ionic liquids (ILs) are organic salts composed of an organic cation and an inorganic anion. , In recent years, ILs have been widely studied because of their low volatility, high conductivity, wide electrochemical window, and high thermal stability. − Based on these advantages, IL-based ionic conductors have attracted increasing attention. However, ILs may leak when a flexible device is stretched or compressed many times, which significantly reduces the service life of such devices; thus, there is a need to develop new ionic conductors to overcome the shortcomings of hydrogels and ionic gels.…”