Experimental study of particle structuring in vertical stratifying films from latex suspensions

Two independent interference methods, based on wavelength and intensity measurements, are applied to establish the type of packing of latex particles contained within vertical stratifying films. The films are formed in a ring-shaped frame after its pulling out from a latex suspension. They exhibit a stepwise profile, which appears as a set of parallel stripes of uniform intensity varying from stripe to stripe. Both interference methods allow a study of the stratification phenomenon ''in vivo'', i.e. during the process of film drainage. To fit the data from each of these two methods, we assume a given type of particle packing, in our case hexagonal or tetragonal, and then we check which type is consistent with the data, In all cases the data indicate the presence of hexagonal packing and do not agree with tetragonal packing, The developed technique can be further applied to examine the particle structuring in stratifying films containing smaller particles, such as surfactant micelles or protein globules. The results can be helpful for a deeper understanding of the stratification phenomenon and the underlying oscillatory structural forces.