Stability and behaviour in aqueous solutions of the anionic cubic silsesquioxane substituted with tetramethylammonium

Emelie J. Nilsson, Marina Huber, Göran Carlström, Olle Söderman, Daniel T. Bowron, Karen J. Edler, Viveka Alfredsson

Research output: Contribution to journalArticlepeer-review

2 Citations (SciVal)

Abstract

The aqueous behaviour of the anionic octa-tetramethylammonium substituted cubic silsesquioxane, [N(CH 3 ) 4 ] 8 [Si 8 O 20 ], was studied with quantitative 29 Si-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.

Original languageEnglish
Pages (from-to)6732-6742
Number of pages11
JournalPhysical Chemistry Chemical Physics
Volume21
Issue number12
DOIs
Publication statusPublished - 2019

Subject classification (UKÄ)

  • Physical Chemistry

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