MORPHOLOGY OF ELLIPSOIDAL LATEX-PARTICLES

Ellipsoidal polystyrene latex particles, a few micrometres in length a nd very suitable for use as models for colloid studies, have been prep ared and characterized. Polystyrene spheres were embedded in poly(viny l alcohol) (PVA) and the resulting film stretched at 200-degrees-C to two film draw ratios, 1.4 and 2.35. The deformed particles were examin ed by light scattering and some were extracted for transmission electr on microscopy. The light scattering results, analysed using Rayleigh-G ans theory, were in very good agreement with the electron microscopy. The ellipsoids were biaxial (within the limits of experimental effor). Those deformed to the highest draw ratio deviate slightly from true e llipsoids, having rather sharper ends. The PVA deforms by a process of necking, which is non-uniform on a large scale, so that over the whol e film there can be a considerable variation in draw ratio. However, p articles recovered from any small, local area of the PVA film show a s ize distribution almost as uniform as that of the starting material. T he effective draw ratio of the particles is found to be considerably g reater than that of the matrix.