Charakterisierung von disperisionen durch gekopplete H2O/D2O‐ultrazentrifugenmessungen

The particle size distribution is one of the most important characteristics of aqueous polymer dispersions (diameter range 20 < D < 2000 nm). In addtion, the knowledge of the average particle density ρPM, the density distribution, and the particle refractive index nPM gives information about the chemical composition of dispersions. We report of an ultracentrifuge method which allows to determine all these values simultaneously in one single run. For that purpose the dispersion is measured simultaneously in 3 media of different density, i.e., in H2O, H2O/D2O (1:1, by wt.), and D2O. We use a preparative ultracentrifuge with an analystical rotor with trubidity optics, but instead of an 1‐cell‐rotor an 8‐cells‐rotor and a multiplexer are used. In order to measure very small and very large particles simultaneously in one single run we do not work at the usual constant number of rotor revolutions, but at a rate of revolutions increasing from 0 to 40000 min−1. The ultracentrifuge is connected with a computer on‐line. The calculations are based on Stokes' law and Mie's light scattering theory for homogeneous isotropic spherical particles.