Templating nanoporosity in organosilicates using well-defined branched macromolecules

Abstract

A general route to organic-inorganic hybrids with nanophase morphologies has been elaborated with the objective of ultimately templating nanoporosity in organosilicates. A key feature of the hybrids is the preparation of well-defined macromolecules bearing significant functionality to interact with the organosilicates. The use of living polymerization methods allows the synthesis of polymers with accurate control of molecular weight, polydispersity, and chain ends. We have demonstrated living polymerizations from dendritic and hyperbranched initiators to produce controlled branched, star and hyperstar macromolecules. These polymers are used as structure directing agents to organize organosilicates into nanostructures. Once the macromolecular species has templated or organized the inorganic component, the organic polymer can be selectively removed by thermolysis to produce a nanoporous inorganic structure. The size and shape of the pores are similar to those of the initial hybrid morphology. A significant reduction in the dielectric constant of these insulating materials is achieved simply by replacing a portion of the glass matrix with air which has a dielectric constant of 1.