Optical contrast variation study of nonaqueous suspensions of polymer particles

We analyze the core-shell structure of sterically stabilized hard sphere po lymer colloids by optical contrast variation. Modified polymer particles ar e used which have the same refractive index as the suspending solvent. At l ow contrast, inhomogeneities in the core shell structure of the particles b ecome apparent. The particle form factor is shown to be a sensitive functio n of the temperature due to the interplay of scattering from the core and t he stabilizing layer. We explore the dependence of particle form factors on composition, radius, and temperature and rationalize our observations in t erms of a simple core-shell model. By exploiting the sensitivity of the for m factors we are able to independently study the two components of a binary mixture of polymer particles. (C) 1999 Academic Press.