Self‐Adhesive Self‐Healing Thermochromic Ionogels for Smart Windows with Excellent Environmental and Mechanical Stability, Solar Modulation, and Antifogging Capabilities

Abstract

especially visible and near-infrared light), by dramatically and reversibly modulating their transparency upon exposure to an external stimulus, have attracted significant attention and have proved effective in saving building energy consumption. [2] To date, numerous responsive materials, such as inorganic oxides, organic photochromic dyes, inorganic nanoparticles, and hydrogels have been used to fabricate smart windows. [3,4] Compared with chromic materials that respond to electricity, mechanical force, or magnetic field, thermochromic materials that can be triggered by solar heating are more suitable for smart window applications, as they do not require additional manual intervention or energy consumption. [5] While thermochromic materials show great promise, some shortcomings limit their application in smart windows. [1] For instance, inorganic semiconductor oxides and dyes have unsatisfactory transparency, solar modulation capacity, and poor oxidation resistance. [1] On the other hand, emerging hydrogel-based thermochromic materials, such as poly N-isopropylacrylamide hydrogel, driven by the lower critical solution temperature (LCST) phenomenon, have attracted significant attention due to their high transparency and good solar modulation capability. [6] At temperatures lower than the LCST, water is uniformly dispersed in the polymer network, ensuring good transparency. As the temperature increases, favorable interactions between polymers and water molecules weaken, leading to phase separation that results in opacity. [7] However, these thermochromic hydrogels have inherent disadvantages of water freezing and evaporation. [8] As a result, they have issues concerning environmental stability, which limits their practical application in smart windows.Ionic liquids (ILs) are a class of room-temperature molten salts. [9] Ionogels, a new generation of gels, prepared by immobilizing ILs in 3D polymer networks, are semisolid materials that can retain vital properties of both ionic liquid and polymer networks. [10,11] Compared with hydrogels or organogels, ionogels have exceptional environmental stability that originates from the nonvolatility and wide liquid temperature range of ILs. [12][13][14] Current thermochromic materials used in smart windows still face challenges, such as poor mechanical and environmental stability, unsatisfactory solar modulation capacity, and low transparency. Herein, the first self-adhesive self-healing thermochromic ionogels with excellent mechanical and environmental stability, antifogging capability, transparency, and solar modulation capability by loading binary ionic liquids (ILs) into rational-designed selfhealing poly(urethaneurea) with acylsemicarbazide (ASCZ) moieties that have reversible and multiple hydrogen bonds are reported and their feasibility as smart windows with reliability and long service life is demonstrated. The selfhealing thermochromic ionogels can switch between transparent and opaque without leakage or shrinkage, by the constrained reversible phase separation of ...

Stretchable, Self-Healing, and Remodelable Ionogel via In Situ Phase Separation as a Highly Sensitive Multimode Sensor

“…The fracture strength increased first and then decreased (20 KPa to 1.7 MPa). It was noted that I-6% was brittle, which was caused by excessive phase separation. , In view of the sensor’s stretchability and flexibility, I-2% was selected for the subsequent test. First, cyclic tension with different strains was performed on I-2% (Figure d), and it exhibited certain recovery.…”

“…In addition, adhesion, self-healing, and transparency are essential for the assembly of ionogel-based sensors. − Adhesion allows the gel sensor to be attached to the surface of the material so that it follows the movement of the material to transmit signals accurately. Adhesion comes from the interaction of the gel with the surface of other substances, such as electrostatic interaction, coordination interaction, ion–dipole interaction, etc. , The self-healing property can cause the gel to self-repair when it is damaged by an external force so as to ensure normal signal transmission and extend the service life of the device. , Ionogels hold good conductivity due to IL as a medium.…”

Skin-inspired gradient ionogels induced by electric field for ultrasensitive and ultrafast-responsive multifunctional ionotronics

“…41 Commonly, ionic liquids (ILs), as a class of organic melt salts, can form by combining different ions and show unique diversity and designability, which give the ionogels designable physicochemical properties (hydrophilicity/hydrophobicity, solubility, and polarity). [42][43][44][45][46][47][48] Ionogel-based humidity sensors are oen prepared using hydrophilic ILs and polymers. [49][50][51] Some ambient stable ionogels can also be fabricated using hydrophobic ILs and polymers, which can be used in environments with different humidities or underwater.…”

Strong and Ultratough Ionogel Enabled by Ingenious Combined Ionic Liquids Induced Microphase Separation

“…Phase separation is a new powerful strategy to improve the mechanical properties and self-healing capacity of ionogels, which allows the polymer chains to intertwine tightly, improving toughness of the ionogel. [28][29][30] Block copolymers are the most advantageous candidates for phase separation materials, and the coexistence of hard and soft segments endows the ionogel excellent stretchability and considerable toughness. In situ phase domains occur through the random copolymerization of two monomers with different polarity.…”