Radial structure of commercial styrene-co-butyl acrylate latex particles by means of synchrotron small-angle X-ray scattering under contrast-variation conditions

The structural information of commercial styrene-co-butyl acrylate latex particles along radial direction was observed via the contrast-variation technique using synchrotron small-angle X-ray scattering (SAXS). By manipulating the electron density of the dispersion medium, the microstructural parameters of the latex dispersion were evaluated based on quantitative discussion of the scattering intensity distribution profiles. Four isoscattering points could be identified in the contrast-variation measurements, located at the scattering vectors corresponding to the position of the sharp minima of the scattering curve of homogenous spheres. This suggests that the shape and structure of particles were not affected by adding a certain amount of sucrose and salt. This phenomenon was attributed to the existence of the thin surface layers around particle core in the system. The data indicate that the latex particles exhibit a core–shell structure, and the average thickness of the shell is about 2 nm.