H-1 MAS NMR study of structure of hybrid siloxane-based networks and the interaction with quartz filler

H-1 MAS NMR spectroscopy has been used to study the structure of hybrid sil oxane networks prepared by acid-catalyzed polycondensation of tetraethoxysi lane (TEOS), dimethyldiethoxysilane (DMDEOS) and methyltriethoxysilane (MTE OS) with or without quartz powder as a filler of resulting networks. Dynami c behavior and nature of silanol protons strongly depend on the amount of m ethyl groups in the hybrid network. It has been found that the resulting si loxane networks form very thin layers at the surface of the quartz grains. No free or highly mobile water or isolated silanols are present in these la yers. The present water molecules and silanols are very strongly hydrogen-b onded to bridging oxygen of quartz particles. Such hydrogen bonds significa ntly contribute to mechanical strength of the filled network. (C) 2001 Else vier Science B.V. All rights reserved.