D. Hoebbel et al., The effect of nanoscaled metal oxide sols on the structure and properties of glycidoxypropyltrimethoxysilane derived sols and gels, J SOL-GEL S, 19(1-3), 2000, pp. 305-309
Glycidoxypropyltrimethoxysilane (GPTS) is frequently used as precursor for
the preparation of sol-gel derived nanoscaled hybrid polymers. The influenc
e of nanoscaled metal oxide sols of silica, boehmite, zirconia and ceria on
reactions of GPTS in ethanolic hydrolysates and in corresponding gels (epo
xide ring-opening, condensation degree) was examined by liquid- and solid-s
tate C-13 and Si-29 NMR with regard to a better correlation between structu
re and material properties. Generally, a higher condensation degree of RSi(
O-0.5)(3) units of GPTS is found after addition of metal oxide sols compare
d to GPTS without additives. The metal oxide sols (10 mole% series) cause a
n epoxide ring-opening up to 20% in GPTS hydrolysates after 24 h. A nearly
complete ring opening was found in the boehmite and silica containing hybri
d gels whereas gels containing ceria and other types of silica only show a
low degree of ring-opening. The results show an accelerated ring-opening wi
th increasing content of AlO/OH-species in silica sols. C-13 NMR studies re
veal that the epoxide ring-opening does not completely lead to polyether st
ructures but to considerable amounts (up to 40%) of ethylether groups which
can influence the material properties (hardness).