The aqueous behaviour of the anionic octa-tetramethylammonium substituted cubic silsesquioxane, [N(CH3)4]8[Si8O20], was studied with quantitative 29Si-NMR. This molecule partially fragments in aqueous solutions, forming several smaller entities. The most abundant silica species are the monomer, dimer, cyclic trimer, cyclic tetramer and double three-ring. Higher concentrations are required in order to prevent complete fragmentation of the cubic structure. Additives such as alcohols and tetraalkylammonium salts have a stabilising effect on the cubic silsesquioxane, unlike sodium salts that destabilise it. A high concentration solution, containing the non-fragmented molecule as well as entities resulting from fragmentations, was investigated with neutron scattering coupled with modelling, using empirical potential structure refinement (EPSR). The modelling reveals that TMA+ ions coordinates to all different silica species, with approximately three TMA+ per cube. These are located at the faces of the cube.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry
Nilsson, E. J., Huber, M., Carlström, G., Soderman, O., Bowron, D. T., Edler, K. J., & Alfredsson, V. (2019). Stability and behaviour in aqueous solutions of the anionic cubic silsesquioxane substituted with tetramethylammonium. Physical Chemistry Chemical Physics, 21(12), 6732-6742. https://doi.org/10.1039/C8CP05682J