Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Soft Matter. 2017 Aug 9;13(31):5233-5249. doi: 10.1039/c7sm00599g.
Critical Casimir interactions between colloidal particles arise from the confinement of fluctuations of a near-critical solvent in the liquid gap between closely-spaced particles. So far, the comparison of theoretical predictions and experimental measurements of critical Casimir forces (CCFs) has focused on the critical solvent composition, while it has been lacking for off-critical compositions. We address this issue by investigating CCFs between spherical colloidal particles around the critical point of a binary solvent through a combination of experiments, previous Ising Monte Carlo simulation results and field-theoretical methods. By measuring the correlation length of the near-critical solvent and the pair potentials of the particles in terms of radial distribution functions and by determining the second virial coefficient, we test in detail theoretical predictions. Our results indicate that the critical Casimir theory gives quantitative correct predictions for the interaction potential between particles in a near critical binary mixture if weak preferential adsorption of the particle surface is taken into account.
胶体颗粒之间的临界 Casimir 相互作用源于近临界溶剂在紧密间隔颗粒之间的液体间隙中波动的限制。到目前为止，临界 Casimir 力 (CCF) 的理论预测与实验测量的比较一直集中在临界溶剂组成上，而对于非临界组成则缺乏比较。我们通过实验、以前的伊辛蒙特卡罗模拟结果和场论方法相结合，解决了这一问题，研究了二元溶剂临界点附近球形胶体颗粒之间的 CCF。通过测量近临界溶剂的相关长度和颗粒对径向分布函数的相互作用势，并确定第二维里系数，我们详细测试了理论预测。我们的结果表明，如果考虑到颗粒表面的弱优先吸附，临界 Casimir 理论可以对近临界二元混合物中颗粒之间的相互作用势进行定量正确的预测。
