Ultrafast pH-Sensitive Supramolecular Liquid Crystal Inverse Opal Polymer Films with Tunable Porosity

Rapid response speed and structural reversibility are critical yet challenging performance metrics for practical visual photonic crystal (PC) sensor applications. This work reports a supramolecular liquid crystal-photonic crystal (LC-PC) composite film with a hierarchically porous inverse opal architecture, exhibiting ultrafast and reversible pH-responsive color change. The composite film shows a remarkable shift in reflection wavelength of up to 245 nm, with a complete color transition occurring within 1 s under both acidic and alkaline conditions. The film maintains excellent reversibility and optical stability over 50 repeated pH-response cycles, highlighting its outstanding durability and practical utility. The film also exhibits excellent rewritable ability under acidic and alkaline stimulation. A molecular templating strategy was employed to regulate porosity by varying the content and size of small-molecule hydrogen-bonding templates, thereby elucidating the impact of internal structure on responsiveness. The results confirm that the generation of appropriate pores significantly enhances response performance and spectral tunability. This work presents a practical pathway for designing fast, stable, and reusable optical sensing platforms for real-time environmental monitoring and display applications. Moreover, the molecular templating approach demonstrated here offers a promising strategy for the controllable design of materials with specific recognition capabilities in future sensing applications.