Shape-reconfigurable transparent wood based on solid-state plasticity of polythiourethane for smart building materials with tunable light guiding, energy saving, and fire alarm actuating functions

Abstract

Transparent wood (TW) is a promising light and thermal management material that has enormous potential for energy-efficient engineering applications. However, almost all the polymers currently used to fabricate TW fall under the thermosetting or thermoplastic category, exhibiting extremely monotonous performance and lack of intelligence. Herein, a smart shape-reconfigurable TW is developed through infiltration the polythiourethane covalent adaptable networks (PTU CANs) into the delignified wood (DW) scaffolds. Benefiting from the solid-state plasticity and thermadapt shape-memory behavior of PTU CANs and the highly aligned cellulose nanofibers of the DW scaffolds, the resulting TW exhibits reconfigurable shape memory behavior, excellent optical properties (transmittance of ∼90% and tunable light guiding effects), and low thermal conductivity (212.8 mW m−1K−1). In addition, the tensile strength, modulus, and toughness of TW are 60.14 MPa, 2.09 GPa, and 1.19 MJ m−3, respectively. Moreover, the reconfigurable shape-memory performance of the TW allows it to be used as a smart actuator for designing a fire alarm system. Compared with traditional TW, the TW reported in this work not only maintains high optical transmittance, but also exhibits excellent reconfigurable shape memory properties, which can promote the high-value utilization for TW. The incorporation of the shape reconfiguration, light guiding, energy saving, and fire alarm actuating properties to the TW opens a new avenue for the design and development of advanced functional and intelligent building materials.