THERMAL-PROPERTIES OF THE HOMOLOGOUS SERIES OF 8-FOLD ALKYL-SUBSTITUTED OCTASILSESQUIOXANES

The homologous series of 8-fold alkyl-substituted octasilsesquioxane h as been prepared by hydrosilation of alkenes with octakis(hydridosilse squioxane) (HSiO3/2)(8). Ethene, propene, 1-butene, 1-pentene, 1-hexen e, 1-heptene, 1-octene, 1-nonene, and 1-decene were employed either in bulk or in toluene solution. The homologous series of acyclo[9.5.1.1( 3,9).1(5,15).1(7,13)]octasiloxanes, which are interesting model compou nds for silsesquioxane-based materials was characterized by H-1, C-13, and Si-29 NMR spectroscopy, IR and mass spectroscopy, and elemental a nalysis. Melting points of the compounds were studied by DSC, revealin g a strong decrease of the melting point from the oetapropyl-substitut ed T-8 to the octapentyl derivative. Melting points for derivatives wi th longer n-alkyl chains showed an odd-even effect. TGA evidenced ther mal stability under nitrogen up to temperatures between 200 and 400 de grees C and under air up to temperatures between 200 and 250 degrees C .