Study of particle interaction in a highly concentrated latex by turbidimetry

A study of the low-angle region of the static structure factor S(q) (q=(4 pi/lambda) sin(theta/2); theta:scattering angle, lambda:wavelength of the radiation in the medium) of a concentrated (44 wt.%) poly(methyl-methacrylate) (PMMA) latex by turbidimetry is presented. It is demonstrated that S(0), i.e., the structure factor extrapolated to vanishing scattering angle can be obtained in excellent accuracy up to the highest concentrations. Since S(0) reflects the balance between long-range attractive and short-range repulsive forces between the latex particles, this quantity can be used to assess the stability of the latex against flocculation. Special attention has been paid to the influence of polydispersity on S(0). The analysis of S(q) in the vicinity of q = 0 for the system under consideration indicates the absence of attractive forces between the particles.