Photophysical effects between spirobenzopyran-methyl methacrylate-functionalized colloidal particles

Area of Science:

• Materials Science
• Polymer Chemistry
• Colloid Science

Background:

• Colloidal particles functionalized with polymers offer tunable properties.
• Photochromic molecules can change properties upon light exposure.
• Controlling colloidal stability is crucial for material applications.

Purpose of the Study:

• To investigate the effect of photochromic molecules on colloidal particle stability.
• To determine the optimal concentration of spirobenzopyran for aggregation control.
• To understand the influence of solvent polarity on photoswitching-induced aggregation.

Main Methods:

• Atom-transfer radical polymerization (ATRP) to grow polymer brushes.
• Synthesis of core-shell silica particles with polymethylmethacrylate brushes.
• Incorporation of spirobenzopyran photochromic molecules at varying concentrations.
• Characterization using turbidimetry, UV-vis spectroscopy, rheology, SEM, and wettability studies.

Main Results:

• Core-shell colloids remained stable in toluene with spirobenzopyran in its nonpolar form.
• UV irradiation induced aggregation due to photoisomerization to the polar merocyanine form.
• A copolymer brush with 20% spirobenzopyran and 80% methyl methacrylate exhibited the most pronounced aggregation in toluene.
• Aggregation behavior was sensitive to spirobenzopyran content and solvent polarity.

Conclusions:

• Polymethylmethacrylate brushes functionalized with spirobenzopyran enable light-induced control over colloidal stability.
• The concentration of photochromic molecules is a key factor in tuning the aggregation transition.
• This system demonstrates potential for applications requiring light-responsive materials.