Polydomain Liquid Crystal Elastomers with Mechanically Switchable Opacity for Thermal Shielding.

Smart screens with adjustable optical properties represent an emerging technology for functional light management. Applications range from temperature control, both for indoor and outdoor environments, to innovative lighting solutions. To date, most of the materials employed in the field require a continuous energy supply to maintain the desired optical properties, while others directly responding to the environment are difficult to control and hardly tunable. In this work, we demonstrate an alternative solution based on polydomain liquid crystal elastomers (LCEs) with reversible mechanical modulation of their opacity. Our mechano-responsive LCEs provide optical scattering properties that are easily controllable and self-maintained without energy-consumption. The materials are prepared by a low-cost, easily scalable one-step procedure with commercially available monomers. The synthesized LCEs present a colorless, opaque appearance that can be gradually and reversibly transformed into a transparent monodomain material by applying a tensile stress. Beside shading properties, the mechano-responsive LCEs allow a strong thermal shielding effect diminishing the temperature rise up to 10 °C upon irradiation with simulated sunlight when employing the opaque state. This work establishes an important step for new smart screen technologies not needing complex fabrication techniques nor a continuous power supply for their dynamic operation.