MORPHOLOGY OF INORGANIC-ORGANIC HYBRID MATERIALS DERIVED FROM TRIETHOXYSILYLATED DIETHYLENETRIAMINE AND TETRAMETHOXYSILANE

Triethoxysilylated diethylenetriamine (f-DETA) and its mixtures with tetramethoxysilane (TMOS) have been hydrolyzed and condensed to form abrasion resistant coatings for optical plastics such as bisphenol-A polycarbonate and CR39. In this paper, the influences of the pH and water concentration on the morphology of gels derived from f-DETA alone (f-DETA100) or equal weights of f-DETA and TMOS (f-DETA50TMOS50) were studied. For the f-DETA50TMOS50 system, with an equivalent ratio (r) of water to alkoxysilane (OH/SiOR) of 4.4, sol-gel reactions at pH 0–2 often led to a particulate gel structure. However, if the reaction was carried out pH 4–5, the resulting gel often had a uniform compact structure although some particulate features were found on the surface. For the f-DETA100 system at pH 0–2, as r increased from zero, the resulting f-DETA gels exhibited a morphological transition from a monolithic uniform structure, to a porous particulate structure, and then to a compact fine particulate structure. A simil...