High molecular weight poly(ethylene oxide)/silica hybrids by the sol-gel process

We prepared inorganic/organic hybrids by the sol-gel process, using tetraethyl orthosilicate (TEOS) in an aqueous solution of poly(ethylene oxide) (PEO) under acidic conditions (HCl). The hybrids represent so-called sequential interpenetrating networks with PEO (polymer I) and silica (polymer II). The PEO content was between 0.25 and 1.0 g of PEO for every 50 ml of TEOS. The PEO molecular weight was either 100 000 or 300 000. The water-to-alkoxy ratio (R) was either R = 3 or R = 8. Among these variables, the water-to-alkoxy ratio had the largest influence on physical properties, such as density and hardness. The types of behavior were divided into two categories, one for the gels prepared with less than stoichiometric water (R < 4) and the other for those prepared with excess water (R > 4).