FINE SILICA POWDER MODIFIED WITH QUATERNARY AMMONIUM GROUPS - REACTIVITY AND CHARACTERISTICS

Fine silica powders were modified with quaternary ammonium groups, and the products were characterized in various respects. 1,3,5,7-Tetramet hylcyclotetrasiloxane was deposited on fine silica powder at 80 degree s C by a chemical vapor deposition method, where it was catalytically polymerized to form a surface coating of polymethylsiloxane. Fine sili ca powder modified with quaternary ammonium groups (XNm, m is the carb on number of the alkyl chain, 4-18) was synthesized from polymethylsil oxane-SiO2 by hydrosilylation with p-chloromethylstyrene and subsequen t treatment with N,N-dimethyl-n-alkylamine. XN4, 6, and 8 were found t o be hydrophilic; XN10, 12, 14, 16, and 18 were hydrophobic. The conta ct angle of XNm showed a tendency to increase with increasing carbon n umber (XN10-->37.7 degrees; XN18-->121.0 degrees).