Temperature-Controlled Switchable Photochromism in Solid Materials.

Area of Science:

• Materials Science
• Photochemistry
• Polymer Chemistry

Background:

• Photochromism enables reversible color changes in materials upon light exposure.
• Controlling photochromic states in solid materials, especially for on-demand switching, remains a challenge.
• Existing methods often require chemical modifications or external additives.

Purpose of the Study:

• To introduce a novel strategy for achieving thermally switchable photochromism in solid-state materials.
• To enable selective stabilization of photochromic states based on thermal phase transitions.
• To demonstrate a general and versatile approach applicable to various photochromic systems and material fabrication.

Main Methods:

• Preparation of polymeric core-shell capsules encapsulating photochromic dyes within acidic phase-change materials.
• Utilizing the phase transition (solid-liquid) of the encapsulated medium to control photochromic states.
• Thermally cycling the system through the melting temperature of the phase-change material to induce reversible photochromism.

Main Results:

• Demonstrated thermally switchable photochromism by selectively stabilizing direct and reverse photochromic states.
• Achieved reversible interconversion between photochromic states by thermal scanning across the phase-change material's melting temperature.
• Confirmed the generality of the strategy for different spiropyran photochromes and its applicability to various functional materials.

Conclusions:

• The developed strategy offers a new pathway for creating solid materials with thermally controlled photochromic properties.
• This approach provides on-demand control over photochromism without chemical modification of dyes or addition of external agents.
• The core-shell capsule system is versatile and can be integrated into diverse solid matrices for advanced functional material applications.