Thermally triggered solvent-responsive "afterglow" structural coloration system based on double-inverse opal photonic...

Solvent-responsive photonic crystals (SRPCs) show promise for advanced optical applications but are limited by single-stimulus dependency and static color responses. Here, we present a thermally triggered solvent-responsive "afterglow" coloration system based on double-inverse opal photonic crystals (DIOPCs), synergizing phase-change mediation and solvent-responsive lattice engineering. The DIOPCs were fabricated by introducing polystyrene (PS) nanospheres (n ∼ 1.59) into a stearyl acrylate-based inverse opal photonic crystals (SA-based IOPCs) skeleton (n ∼ 1.44) with phase-change ability. Thermal activation induces a crystalline-to-amorphous transition in the skeleton, which drives the directional contraction of the three-dimensional (3D) polymer network to encapsulate PS nanospheres. Subsequent cooling locks the recrystallized network, protecting the PS cores from solvent corrosion. This process creates "trap energy levels" (an analogy describing a state whose role is analogous to that of trap levels in "long-afterglow" luminescent materials, serving to highlight their functional similarity rather than actual physical energy levels) and preserves the refractive index contrast for subsequent solvent "activation", thereby completing the thermal triggering step. Guided by Hansen solubility parameters (δ_cyclohexane = 16.8, δ_polymer = 17.0), cyclohexane was employed to swell the lattice, enabling recovery of photonic periodicity. This yielded sequential photonic stop band evolution from disorder to ordered coloration and finally a redshift beyond the visible spectrum. Precise modulation of lattice spacing (d₁₁₁) via swelling duration achieved wide-range color tuning, creating an "afterglow" effect. The patterned SRPCs demonstrated a dynamic information encryption application, while the thermally triggered solvent-responsive cascaded regulation mechanism overcame traditional SRPCs' limitations, offering new avenues for advanced optical materials.