Investigating the Effective Interaction between Silica Colloidal Particles near the Critical Point of a Binary Solvent by Small Angle Neutron Scattering
Zhiyuan Wang, Hongyu Guo, Yun Liu, Xuewu Wang
An effective attractive potential can be introduced between colloidal particles dispersed in a binary solvent when the solvent condition approaches its demixing temperatures. Despite the debate of its physics origins of this effective attraction, it is widely termed as the critical Casimir force, and is believed to be responsible for the colloidal stability in a wide range of particle concentration at both critical and near-critical solvent concentrations. Here, we study this effective attraction and equilibrium phase transition of charged spherical silica particles in the binary solvent of 2,6-lutidine and water as a function of particle volume fraction and temperature at the critical solvent concentration. By analyzing our SANS data, we found that at relatively small particle volume fraction, the density fluctuation introduced attraction between silica particles can be satisfactorily explained by the function form commonly used for the critical Casimir interaction. However, at large silica particle volume fractions, an additional attractive component with much longer range has to be introduced to satisfactorily fit our SANS data and explain the large shift of the phase transition temperature. Therefore, while at the low volume fraction, the solvent introduced
, Guo, H.
, Liu, Y.
and Wang, X.
Investigating the Effective Interaction between Silica Colloidal Particles near the Critical Point of a Binary Solvent by Small Angle Neutron Scattering, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926008
(Accessed May 30, 2023)