Structure and physical properties of sol-gel derived polypropyleneglycol/silica hybrid

Polypropyleneglycol (PPG) oligomer with amino groups on the chain ends (Mn= 2000) was reacted with isocyanatopropyltriethoxysilane. and triethoxysilane groups were end-capped onto PPG. Transparent PPG/silica hybrid films could be obtained by mixing TEOS with the triethoxysilane end-capped PPG. The te nsile strength and modulus of the PPG/silica hybrid increased with increasi ng amount of mixed TEOS. The temperature dependence of the dynamic viscoela stic measurements gave the double peaks of tan delta at -50 degrees C and 3 0 degrees C. The peak at-50 degrees C was caused by the glass transition of PPG matrix. The peak at 30 degrees C may be due to the glass transition of the silica rich domains, which were formed by the micro-phase separation d uring soi-gel process. This morphology was confirmed by the SAXS measuremen t, showing a large and sharp peak at the scattering vector q=1.3 nm(-1); th is peak shifted to the higher temperatures with increasing amounts of initi al TEOS content.