Octopus and dendrimer molecules with silsesquioxane cores

Gentle, Theresa Eileen (1995). Octopus and dendrimer molecules with silsesquioxane cores. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000e0c8

Abstract

The interest in materials with designed physical properties and controlled molecular formula is increasing. Octopus molecules, or materials with pendent groups from a core, and dendrimer molecules, or materials with a defined pattern of branching from a core are means of obtaining molecules of designed architecture. The work presented here involves the synthesis and characterization of octopus and dendrimer molecules of defined shape with molecular weights well into the thousands.

These designed molecular materials have been synthesized by placing pendant groups symmetrically about a silsesquioxane [(SiO_3/2)₈] core. A facile, one-step route to hydrocarbon and siloxane functional octopus molecules via H2PtC16 catalyzed hydrosilylation of 1-alkenes and vinyl-functional siloxanes by T₈ hydrogen silsesquioxane, (HSiO_3/2)₈, has been demonstrated. The chemistry of addition was studied, and it was found that while the addition of the I-alkenes to T₈ was, regioprecise with only a-addition being observed, both a- and ß-addition occurred with vinyl siloxanes. In addition, H/vinyl exchange on silicon was observed to occur with addition of vinyl-siloxane to T₈. The effect of the hydrosilylation catalyst, homogeneous and heterogeneous, on the regioselectivity of addition and on the extent of exchange on silicon has been evaluated via GPC and ¹³C and ²⁹Si NMR.

Investigations into the feasibility of placing a number of other moieties on the silsesquioxane core to show the almost limitless types of functional octopus molecules that can be made and to expand into dendritic molecules were also accomplished. For example polyether functional and mixed polyether/siloxane functional octopus molecules were synthesized and found to have interesting surface activity. The synthesis of an acrylate functional octopus molecule was accomplished and the product used to produce an ultra-violet curable coating.

Finally, routes other than hydrosilylation to produce octopus and dendrimer molecules with silsesquioxane cores, for instance, the reaction of ROH with SiH of (SiO_3/2)₈, were developed and used to increase the types of functional octopus possible and to produce dendrimer molecules with silsesquioxane cores. The synthesis, characterization, and possible applications of silsesquioxane-based octopus and dendrimer molecules will be discussed.