Easily Tunable Membrane Thickness of Microcapsules by Using a Coordination Assembly on the Liquid-Liquid Interface

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Nanotechnology

Background:

• Coordination assembly offers a versatile route for fabricating functional materials.
• Tannic acid, a natural polyphenol, can form stable complexes with various metal ions.
• Controlling the architecture of microcapsules is crucial for their performance in encapsulation and release applications.

Purpose of the Study:

• To investigate the encapsulation of 1,3,5-trimethylbenzene using coordination assembly of metal ions and tannic acid.
• To characterize the deposition of coordination complexes and the resulting microcapsule structure.
• To demonstrate the tunability of microcapsule membrane thickness through controlled deposition cycles and metal ion choice.

Main Methods:

• Coordination assembly utilizing metal ions (Fe3+, Ca2+) and tannic acid.
• Characterization techniques including zeta potential, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
• Atomic force microscopy (AFM) for membrane thickness analysis and dissolution testing to evaluate release kinetics.

Main Results:

• Successful encapsulation of 1,3,5-trimethylbenzene within microcapsules formed via coordination assembly.
• Confirmation of coordination complex deposition at the liquid-liquid interface using spectroscopic methods.
• Linear increase in microcapsule membrane thickness with sequential deposition cycles, demonstrated with the Fe3+-TA system (e.g., 254.8 ± 24.0 nm for 8 cycles).
• Significantly thinner membranes observed for the Ca2+-TA system, highlighting the influence of metal ion choice.
• Release profiles followed Higuchi kinetics, indicating diffusion-controlled release.

Conclusions:

• The coordination assembly strategy provides a facile and tunable method for fabricating microcapsules with controlled membrane thickness.
• Adjusting metal ions and deposition cycles allows for precise control over microcapsule properties.
• This approach holds significant potential for broad applications requiring tailored encapsulation and release functionalities.