A Crown Ether-Based LCST Molecule With Cation Size Selective Matching Capability for Efficient Management of Solar Radiation.

Supramolecular matter exhibiting a lower critical solution temperature (LCST) represents a typical class of thermo-responsive systems with controllable phase separation performance, and they have attracted widespread attention. Herein, we report a novel crown ether-based supramolecular material with tunable LCST properties. The crown ether compound itself, namely CG, is composed of a long ethylene glycol (EG) chain conjugated with dibenzo-24-crown-8 (DB24C8). Compound CG exhibits good solubility in aqueous solution (20 mg/mL) and demonstrates excellent LCST performance, demonstrating a cloud point temperature (Tcp) = 30°C, with a thermal hysteresis ΔT = 0.2°C and good reversibility. Interestingly, the LCST properties can be further modulated through supramolecular complexation between CG and certain cations, enhancing the tunability of the CG molecule. A smart window was thus fabricated for efficient management of solar radiation, achieving ∆Tlum (luminous transmittance), ∆TIR (IR transmittance) and ∆Tsol (solar modulation) values of 97.2%, 79.4%, and 86.4%. Notably, the reduced freezing point of the CG solution upon the addition of cations also offers the application potential of such smart windows in cold regions.