Structure transition from hexagonal mesostructured rodlike silica to multilamellar vesicles.

Area of Science:

• Materials Science
• Nanotechnology
• Supramolecular Chemistry

Background:

• Block copolymers and surfactants are key in templating porous materials.
• Understanding structure-directing mechanisms is crucial for designing novel materials.
• Previous work has explored various templating agents for silica synthesis.

Purpose of the Study:

• To investigate the synthesis of siliceous structures using a nonionic block copolymer (Pluronic P123) and perfluorooctanoic acid (PFOA) as co-templates.
• To elucidate the structure transition mechanism induced by varying the PFOA/P123 molar ratio (R).
• To provide insights into the fabrication of novel porous materials.

Main Methods:

• Acid-catalyzed sol-gel synthesis.
• Systematic variation of the PFOA/P123 molar ratio (R).
• Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, and Fourier-transform infrared spectroscopy (FTIR).

Main Results:

• A structure transition was observed from 2D hexagonal (HEX) mesostructures to multilamellar vesicles (MLVs) with increasing R.
• Multilamellar vesicles (MLVs) were found to initiate from the ends of hexagonally mesostructured rods.
• An interaction model involving PFOA and Pluronic P123 (PEO moiety) was proposed to explain the observed structural changes, including wall thickening and the HEX to MLV transition.

Conclusions:

• The study demonstrates a novel structure transition from hexagonal mesostructures to multilamellar vesicles, driven by the PFOA/P123 ratio.
• Multilamellar vesicles (MLVs) formation is a gradual process originating from hexagonal structures, not direct cooperative self-assembly.
• The proposed interaction model between PFOA and Pluronic P123 provides a framework for understanding and fabricating new porous materials using mixed-template systems.