There is an intense interest in design simple strategy to synthesize hollow-structured spheres. Hollow calcium carbonate particles have attracted considerable attention owing to their excellent properties such as low density, high specific surface areas, and drugs, inks or pigments microencapsulation. Previous studies showed that the nucleation mechanism requires the presence of calcium-binding acidic groups on the polymer, thus providing the template upon which crystallization could occur. The formation of hollow shells of calcium carbonate, by the principle of controlled nucleation and growth on a polyanion substrate, is discussed in this paper. To initiate the nucleation mechanism, which required the presence of calcium-binding acidic groups, a strong/weak anionic copolymer, poly(2-acrylamido-2-methylpropanesulfonic acid–co-acrylic acid), was used. The influence of polyanion concentration (0.2 and 0.4 wt.%) on the CaCO₃ hollow microparticles growth from supersaturate aqueous solutions, at pH = 10.5 and after 8 h crystallization time, has been followed. The products were characterized by scanning electron microscopy, laser diffraction, X-ray powder diffraction, X-ray photoelectron spectroscopy, particle charge density, and zeta potential. In the presence of the copolymer, hollow-structured spherical particles, with medium sizes of 4 – 6 μm and containing just calcite polymorph, were obtained. The small increase of particles charge density, comparative with blank sample, showed that the polymer is located mainly inside the hollow particles and the calcite crystals on their surface.

Acknowledgment: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n°264115 - STREAM.

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