CO2-triggered reversible transformation of soft elastomers into rigid and highly fluorescent plastics.

Polymers that alter their properties and functions in response to carbon dioxide (CO2) exposure offer significant potential for the development of smart technologies and innovative CO2 utilization approaches. Nonetheless, effectively regulating the behavior of solid-state polymers using CO2 remains a considerable challenge, highlighting the need for robust and reliable strategies to address this issue. This study presents elastomers that feature nanophase-separated morphologies composed of CO2-vitrifiable polyethyleneimine and CO2-permeable polydimethylsiloxane components. The elastomers (Young's modulus (E) of approximately 1 MPa) reversibly transform into hard plastics (E > 2 GPa) in the presence of CO2. In addition to bulk stiffening, their surface adhesion and friction rapidly shift, and the material's fluorescence is significantly amplified. Here, we show that these multifunctional responses to CO2 position the materials as innovative platforms for responsive mechanical systems and CO2-activated optical devices, with potential applications in sensing, display, and data storage technologies.