Ultralong phosphorescence visualization of dynamic behavior in shape-memory materials at high temperature
image: (a) Schematic illustration of the components of the shape memory polymer and the diagram of 3D butterflies fabricated by increasing photo-crosslinking time. Phosphorescent spectra (b), emission decay curves (c) and DSC curves (d) of Cor-EP with different photo-crosslinking time of 365 nm UV light. (e) Time-dependent wing opening angles (°) of Cor-EP-4, Cor-EP-15, Cor-EP-60 at 200 °C, respectively. (f) Wing opening angle and luminance changes of Cor-EP-60 at 200 °C in 60 times shape-memory cycles. (g) Demonstrations of the wing opening angles and luminescent properties of 3D butterflies Cor-EP-4, Cor-EP-60 at 35 and 200 °C, respectively. Cor-EP-4, Cor-EP-15 and Cor-EP-60 mean Cor-EP samples are photo-crosslinked for 4, 15 and 60 s, respectively. Scale bar, 10 mm. Data are presented as mean values ± SD, n = 3.
Credit: ©Science Bulletin
Shape memory materials exhibit broad application prospects in fields such as actuators and flexible robots by virtue of their programmable actuation properties. However, there is still a lack of monitoring methods that can directly observe their dynamic actuation processes in certain extreme environments like darkness and high temperatures. Therefore, realizing real-time visualization of the dynamic behaviors of such materials is of great significance for expanding their practical application scenarios. Ultralong organic phosphorescent materials feature ultralong afterglow luminescence. They can emit stable optical signals in dark environments without continuous excitation from external light sources, making them ideal functional media for the visualized monitoring of shape configuration changes.
This study focuses on the synergistic thermal response of ultra-long phosphorescence and shape memory effect. By precisely regulating the degree of double bond cross-linking, the synergistic regulation of phosphorescence lifetime (2.36-5.87 s) and glass transition temperature (27.46–75.37 °C) is achieved simultaneously, and intelligent polymer materials with tunable ultra-long afterglow and controllable shape configurations are constructed. Long-afterglow 3D butterfly configurations with different flapping angles are fabricated by adjusting the photo-crosslinking time, and their entire dynamic flapping deformation processes are visually monitored in a wide temperature range from room temperature to 200 °C under dark conditions. Furthermore, relying on the synergistic regulation of ultralong phosphorescence and shape memory behavior near body temperature, a 3D information encryption system with dynamically reconfigurable patterns is established, which displays distinct information in planar and three-dimensional configurations. Apart from realizing multi-level information encryption, benefiting from the synergistic response characteristics of long afterglow and shape memory at high temperatures, it can quantitatively monitor the overheating state of circuit switches after being coated with encapsulated conductive metal wires. The expansion of such application scenarios provides novel strategies and ideas for the design and application of self-sensing and self-indicating intelligent materials in extreme environments.