Quantification of the Structure of Colloidal Gas–Liquid Interfaces

[Image: see text] We have quantified the structure of the colloidal gas–liquid interface using synchrotron X-ray reflectivity measurements on a model colloid–polymer mixture. The interfacial width shows mean-field scaling with the colloid density difference, and the density profiles appear to be monotonic. Furthermore, our measurements allow us to distinguish between different theoretical polymer descriptions commonly used to model colloid–polymer mixtures. Our results highlight the importance of capturing the correct polymer physics in obtaining a quantitative theoretical description of the colloidal gas–liquid interface.