Structural and dynamical studies of hybrid siloxane-silica materials

Hybrid siloxane-silica coatings have been prepared by hydrolysis and condensation of N-[3-triethoxysilylpropyl]-2,4-dinitrophenylamine (TSDP) and tetramethoxysilane (TMOS) precursors. Hetero- and home-condensations between both precursors have been demonstrated to occur in the early stages of the process via O-17 and Si-29 nuclear magnetic resonance (NMR) in solution. These hybrids can be described as nanocomposites made of polysiloxane-based domains cross-linked by silica-based nanoparticles, as evidenced bd solid-state NMR, differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR) studies. Moreover, the high degree of interpenetration occurring in these materials is evidenced by the presence of some Q and T subunits sequestered within these polysiloxane and silica-based domains, respectively. The high-resolution solid-state C-13 NMR technique has shown that the mobility of the propyl 2,4-dinitrophenylamine chromophores is correlated with the glass-transition phenomenon of the matrix.