Fade-resistant photochromic reactions in a self-healable polymer

Area of Science:

• Materials Science
• Polymer Chemistry
• Photochemistry

Background:

• Photochromic materials undergo degradation during repeated coloration-decoloration cycles.
• Diarylethene molecules are susceptible to damage, impacting their performance.
• Polydimethylsiloxane (PDMS) is a polymer matrix investigated for its potential in stabilizing photochromic reactions.

Purpose of the Study:

• To investigate molecular diffusion in a polymer matrix to prevent photochromic degradation.
• To enhance the longevity of photochromic diarylethene dispersed in polydimethylsiloxane.
• To evaluate the impact of polymer swelling on diffusion coefficients and photochromic stability.

Main Methods:

• Dispersing photochromic diarylethene in cured polydimethylsiloxane.
• Evaluating the diffusion coefficient by measuring the distribution of colored dye molecules.
• Analyzing temporal changes in molecular distribution using 2-D solutions of Fick's equation.
• Examining photochromic fading by repeated irradiation with violet and green laser beams.

Main Results:

• A fifteen-fold enhancement in the diffusion coefficient (0.0015 mm²/s) was observed when the polymer was swollen with toluene.
• Temporal changes in dye molecule distribution fitted well to theoretical Fick's equation solutions.
• Non-swollen polymers showed significant fading within 1,000 photochromic cycles.
• Swollen polymers maintained excellent photochromic function after 30,000 cycles.

Conclusions:

• High molecular diffusivity in swollen polymers facilitates the exchange of damaged and fresh photochromic molecules.
• Swelling polydimethylsiloxane with toluene dramatically improves the stability and durability of photochromic diarylethene.
• This approach offers a viable strategy for creating robust photochromic materials for long-term applications.