Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2005
Publication Date: N/A
Technical Abstract: The polymerization of di- and tri-alkoxysilanes using conventional sol-gel techniques produces two and three-dimensional siloxane networks. The hydrolysis and condensation result in the formation of an alcohol under mild conditions which can be removed under reduced pressure and moderate temperature. Incorporation of phosphonate functionalized methoxysilanes, (CH3O)2CH3Si(CH2)3P=O(OCH3)2 or (CH3O)3Si(CH2)3P=O(OCH3)2, into the reaction mixture results in a polysiloxane bearing pendant phosphonate groups. Copolymerization of the silane-phosphonate monomers with di- and trimethoxysilane yields linear and crosslinked polysiloxanes. The linear copolymers are viscous fluids stable to relatively high temperatures (270oC). Phosphonate esters are known to coordinate metal salts via the phosphoryl oxygen. The siloxane-phosphonate copolymers in this work have been found to coordinate a variety of metal salts including lithium and uranium. Crosslinked copolymers, B, form thermally stable glasses when using sol-gel techniques. Dissolution of lithium salts in the monomer/catalyst solution prior to polymerization produced clear, colorless films which act as semiconductors. Freeze drying of similar crosslinked samples containing a high water/alcohol content has produced stable xerogels.