Ring-opening metathesis polymerization on well defined silica nanoparticles leading to hybrid core–shell particles

Abstract

The grafting and catalytic activity of a metathesis catalyst on well defined silica nanoparticles is described. The aim of this was to test the catalysis properties of a ligand-linked catalyst in ring-opening metathesis polymerization and also the possibility to obtain controlled hybrid materials. This was carried out by reaction of a synthesized hydroxy functionalized phosphine Cy₂P(CH₂)₁₀OH with Cl₂Ru(PPh₃)₂(CH–Ph), leading to a metathesis catalyst bearing a hydroxy group at the end of a ligand. This group was reacted with well defined silica nanoparticles with a diameter of 200 nm, that had acyl chloride functions at their surface. The grafting density was calculated from thermogravimetry experiments and found to be around 7 µmol m⁻². The activity of the catalyst was tested for the ring-opening polymerization of norbornene. This showed that a fraction as high as 30% of the catalyst could initiate the polymerization and that the polymerization proceeded until completion. TEM characterization revealed that in diluted solutions, core–shell morphologies could be obtained. The efficiency of the polymerization may therefore lead to control of the thickness of the polymer coating.