Preparation of inorganic-organic hybrid gels by radical exchange reaction using TiO₂ nanoparticles modified with organophosphonic acid bearing C-ON bonds

Inorganic-organic hybrid gels were prepared using TiO₂ nanoparticles modified with organophosphonic acid bearing C-ON bonds by a radical exchange reaction. The modification of TiO₂ with N-tert-butyl-N-(1-dihydroxyphosphoryl-2,2-dimetylpropyl)aminoxymethyl benzene (DEPN-BA) and isodecyl phosphonic acid (IDP) was confirmed by IR and ³¹P MAS NMR. ESR spectroscopy indicated the presence of nitroxide radicals with heating of the modified nanoparticles at 120C. Hybrid gels were prepared using TiO₂ nanoparticles, which were modified with DEPN-BA and IDP (IDP_DEPN-BA_TiO₂), and a poly(4vinylbenzyl chloride) derivative bearing C-ON bonds (PCMS-TEMPO). It was found that the radical exchange reaction with CON bonds was necessary for preparing hybrid gels. It is assumed that a three-dimensional network was formed by crosslinking between the polymers and modified TiO₂ nanoparticles.