STRUCTURAL AND DYNAMICAL STUDIES OF HYBRID SILOXANE-SILICA MATERIALS

Hybrid siloxane-silica coatings have been prepared by hydrolysis and c ondensation of N-[3-triethoxysilylpropyl]-2,4-dinitrophenylamine (TSDP ) and tetramethoxysilane (TMOS) precursors. Hetero- and home-condensat ions between both precursors have been demonstrated to occur in the ea rly stages of the process via O-17 and Si-29 nuclear magnetic resonanc e (NMR) in solution. These hybrids can be described as nanocomposites made of polysiloxane-based domains cross-linked by silica-based nanopa rticles, as evidenced bd solid-state NMR, differential scanning calori metry (DSC) and Fourier-transform infrared (FTIR) studies. Moreover, t he high degree of interpenetration occurring in these materials is evi denced by the presence of some Q and T subunits sequestered within the se polysiloxane and silica-based domains, respectively. The high-resol ution solid-state C-13 NMR technique has shown that the mobility of th e propyl 2,4-dinitrophenylamine chromophores is correlated with the gl ass-transition phenomenon of the matrix.