Photocatalysed (Meth)acrylate Polymerization by (Antimony-Doped) Tin Oxide Nanoparticles and Photoconduction of Their Crosslinked Polymer Nanoparticle Composites
In the absence of another (photo)radical initiator Sb:SnO2 nanoparticles ( 0 ≤ S b ≤ 1 3 at %) photocatalyze during irradiation with UV light the radical polymerization of (meth)acrylate monomers. When cured hard and transparent (>98%) films with a low haze (<1%) are required, when these particles are grafted in advance with 3-methacryloxypropyltrimethoxysilane (MPS) and doped with Sb. Public knowledge about the photocatalytic properties of Sb:SnO2 nanoparticles is hardly available. Therefore, the influence of particle concentration, surface groups, and Sb doping on the rate of C=C (meth)acrylate bond polymerization was determined with aid of real-time FT-IR spectroscopy. By using a wavelength of irradiation with a narrow bandgab ( 3 1 5 ± 5 ？nm) the influence of these factors on the quantum yield (Φ) and on polymer and particle network structure formation was determined. It is shown that Sb doping and MPS grafting of the particles lowers Φ. MPS grafting of the particles also influences the structure of the polymer network formed. Without Sb doping of these particles unwanted, photocatalytic side reactions occur. It is also shown that cured MPS-Sb:SnO2/(meth)acrylate nanocomposites have photoconduction properties even when the particle concentration is as low as 1 vol.%. The results suggest that the Sb:SnO2 ( S b > 0 at %) nanoparticles can be attractive fillers for other photocatalytic applications photorefractive materials, optoelectronic devices and sensors. 1. Introduction Spherical nanoparticles of antimony-doped tin oxide (Sb:SnO2) can be used to provide semiconducting properties to insulating polymers. This change in properties occurs when these particles form a percolating network structure through the polymer matrix [1–6] at a filler concentration higher than the percolation threshold. In a number of scouting experiments in which we studied the rate of curing of such Sb:SnO2)/acrylate formulations, we noticed that in the absence of an organic photoinitiator UV curing also occurred. Because Sb:SnO2 nanoparticles absorb UV light these results suggest that Sb:SnO2 nanoparticles can act as photoinitiator for acrylate polymerization. Photocatalytic effects have been reported for a number of semiconductive nanoparticles. For instance, FeIII doped TiO2 can act as a photocatalyst in acrylate polymerization [7] and CdS [8] or ZnO [9] in methacrylate polymerization. It was also shown that the photocatalytic properties of TiO2 can shorten the lifetime of TiO2 polymer composites [10]. Furthermore, by absorption of UV radiation SnO2 particles can oxidize
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