Publications Details
Formation and polymerization of cyclic disilsesquioxanes
Sol-gel polymerication of {alpha}, {omega}-bis(triethoxysilyl)alkanes normally leads to alkylene-bridged polysilsesquioxanes in the form of insoluble, highly crosslinked polymeric gels. Hydrolysis of the six ethoxide groups on each monomer gives silanols that then condense to form a network of siloxane bonds. Unlike most Sol-gel precursors, these flexible hydrocarbon-bridged monomers can participate not only in intermolecular condensation reactions that lead to polymeric networks, but in intramolecular condensation reactions leading to cyclic disilsesquioxanes as well. Partitioning between these two reaction manifolds should be an important determinant of the manner in which the network polymer is assembled and, be an important determinant of the manner in which the network polymer is assembled and, ultimately, the final morphologies of the crosslinked gels. The relative importance of the two pathways should be dependent on a variety of factors, including the reaction mechanism (acid or base catalysis), the concentration of {alpha}, {omega}(triethoxysilyl)alkane and, most importantly for this study, the length of the alkylene bridging group.