The crystallization of CaCO3 particles from aqueous solutions in the absence and presence of a strong/weak anionic copolymer, poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid) (PAMPSAA) is discussed in this paper. Vaterite/calcite polymorphs with different sizes and spherical shapes were obtained. The products were characterized by infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, flow particle image analysis, laser diffraction technology, and SEM and optical microscopy. Oppositely charged chitosan and PAMPSAA were assembled onto carbonate colloidal particles in a layer-by-layer manner to yield core-shell structures. (c) 2012 Elsevier B.V. All rights reserved.