The presence and effect of water on calcium carbonate nanoparticles used in engine additives, stabilized with a sulfonate surfactant, is investigated using small-angle neutron scattering, dynamic light scattering, Fourier transform infrared spectroscopy, and rheometry. These techniques provide complementary data that suggests the formation of a layer of water around the core of the particles ensuring continued colloidal stability yet increasing the dispersion viscosity. Through the use of small-angle neutron scattering, the dimensions of this layer have been quantified to effectively one or two water molecules in thickness. The lack of a significant electrostatic repulsion is evidence that the water layer is insufficient to cause major dissociation of surface ions.
Tavacoli, J., Dowding, P. J., Steyder, D. C., Barnes, D. J., & Routh, A. F. (2008). Effect of water on overbased sulfonate engine oil additives. Langmuir, 24(8), 3807-3813. https://doi.org/10.1021/la703680e