Cross-Linker-Controlled Ostwald Ripening in Emulsion Polymerization of Hollow Copolymer Nanoparticles

Area of Science:

• Polymer Chemistry
• Materials Science
• Nanotechnology

Background:

• Controlling nanoparticle size is crucial for their applications.
• Hollow polymer nanoparticles offer unique properties due to their internal void.
• Existing synthesis methods may lack precise size control.

Purpose of the Study:

• To develop a controllable synthesis method for hollow copolymer nanoparticles.
• To investigate the role of cross-linkers in nanoparticle size determination.
• To understand the mechanism of size reduction via cross-linker incorporation.

Main Methods:

• Utilized relative energy difference (RED) to design material wettability for size control.
• Synthesized hollow copolymer nanoparticles (styrene-co-methyl methacrylate) with varying divinyl benzene (cross-linker) ratios.
• Characterized nanoparticle size and core-vacancy size using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Main Results:

• Nanoparticle diameter decreased from 400 nm to 141 nm with increasing cross-linker feed ratio (0.07 to 0.43).
• Average core-vacancy size reduced from 330 nm to 71 nm.
• Higher cross-linker concentrations accelerated seed particle formation, reducing Ostwald ripening and nanoparticle size.

Conclusions:

• Cross-linker content is a key factor in controlling hollow copolymer nanoparticle size.
• The proposed method offers precise control over nanoparticle dimensions.
• Reduced Ostwald ripening due to effective seed formation leads to smaller hollow nanoparticles.