The Photopolymerization and Characterization of Methyl Methacrylate Initiated by Nanosized Titanium Dioxide

Abstract

Polymerizations of methyl methacrylate initiated by nano‐TiO₂ semiconductors were studied in this paper. The heterogeneous polymerizations were carried out by dispersing the TiO₂ particles into MMA aqueous solutions. UV light at 365 nm was employed to stimulate photocatalysis of the TiO₂ particles. The progress of the polymerizations was investigated and the products were characterized using various tools of instrumental analysis such as NMR, TGA, DSC, and FT‐Raman spectroscopy. The nature of free radical mechanism of the polymerization was confirmed. It was found that the polymerization is of a double‐species initiation. Both the valence‐band hole and the OH‐radical work as initiators. The results from thermal analysis show that the TiO₂ particles, remained in the raw products, significantly improve the thermal stability of the PMMA polymers. It is well interpreted in terms of initiation mechanism via the valence‐band holes.

Keywords:

• Methyl methacrylate
• Nano‐sized TiO₂
• Photocatalysis
• Valence‐band hole
• Hydroxyl radical
• Polymerization mechanism
• Polymer characterization

Acknowledgments

We are grateful to Shanghai Nanotechnology Promotion Center (SNPC) for financial support, and we appreciate the assistance of Prof. Shiming Chen in the ESR analysis.