Synthesis and structure of ladder polymethylsilsesquioxanes from sila-functionalized cyclotetrasiloxanes

Highly regulated ladder-structured polymethylsilsesquioxanes soluble in solvents with high molecular weight were synthesized from sila-functionalized tetramethylcyclotetrasiloxanes [MeSiXO](4) (X = H, OEt, NCO) by the dehydrogenative condensation of [MeSiHO](4) with water in the presence of N,N-diethylhydroxylamine or the hydrolytic polycondensation of [MeSiXO](4) (X = OEt, NCO). Formation of a siloxane-ladder structure was confirmed based on the appearance of two absorption bands and a signal due to Si-O-Si linkage in the infrared spectra and a silsesquioxane unit in (29)Si nuclear magnetic resonance spectra, respectively. The narrow half-peak width of the (29)Si nuclear magnetic resonance spectra suggested the formation of a highly regulated ladder structure for polymethylsilsesquioxanes. (C) 2010 Elsevier B.V. All rights reserved.