Bridged polysilsesquioxane-polydimethylsiloxane nanocomposites: A reactivity study

It has been demonstrated that increased strength and extensibility can be obtained in polydimethylsiloxane (PDMS) systems through the use of bimodal polymer distributions. In order to further probe short chain and linkage effects in bimodal polymer networks, we are interested in a new class of nanocomposites based on hydroxy-terminated PDMS as the long chain segments and alkylene- or arylene-bridged silsesquioxanes as the short chain segments. We have investigated tin-catalyzed coupling of the terminal hydroxy groups of the PDMS segments with bis(triethoxysilyl)arylene and alkylene monomers. The compatibility of the different silsesquioxane monomers with PDMS, and their activity with the tin-based catalyst, has been explored. A number of different hydrocarbon bridged silsesquioxane monomers have been used to determine the effect that the short segment flexibility and length, and the degree of crosslinking have on the final material properties. Findings from this study will be reported.