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

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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.

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Authors
Organisations
External organisations
  • University of Bath
  • Lund University
  • Rutherford Appleton Laboratory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Chemistry
Original languageEnglish
Pages (from-to)6732-6742
Number of pages11
JournalPhysical Chemistry Chemical Physics
Volume21
Issue number12
Publication statusPublished - 2019
Publication categoryResearch
Peer-reviewedYes