Periodic Mesoporous Organosilicas Containing Interconnected$[Si(CH_2)]_3$Rings

A periodic mesoporous organosilica composed of interconnected three-ring$[Si(CH_2)]_3$units built of three$SiO_2 (CH_2)_2$tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane$[(EtO)_{2} Si(CH_2)]_3$precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of$[(EtO)_{2}Si(CHR)] [(EtO)_Z{2}Si(CH_2)]_2$(where R indicates iodine, bromine, or an ethyl group).