Competitive Polymerization between Organic and Inorganic Networks in Hybrid Materials

Hybrid organic−inorganic materials derived from 3-glycidoxypropyltrimethoxysilane have been synthesized via sol−gel using BF 3 etherate as a catalyst of organic polymerization. Different amounts of BF 3 etherate have been used, from B/Si = 0.01 up to B/Si = 0.1, to prepare powder samples. The materials have been characterized by Fourier transform infrared spectroscopy (FTIR) and multinuclear solid-state NMR spectroscopy. FTIR and NMR spectra have shown that with a B/Si = 0.03 molar ratio a complete opening of epoxy in 3-glycidoxypropyltrimethoxysilane is achieved. The different amounts of BF 3 etherate employed have been found to affect the degree of inorganic cross-linking and the length of the ethylene oxide chains. Larger amounts of BF 3 enhance the inorganic network cross-linking and give oligo(ethylene oxide) derivatives. Boron has been found to remain in the matrix as a network former of the inorganic side. The formation of Si−O−B bonds has been observed by the FTIR spectra.