This study describes the effects of mixed anionic/ cationic polyelectrolytes on the crystallization of calcium carbonate in supersaturated solutions in comparison with polyanion-based CaCO_3 composite structures. Two simple methods of introducing the polycation in the crystallogenesis of calcium carbonate are proposed: preformed nonstoichiometric polyelectrolyte complexes (NPECs) or in situ mixing of complementary polyelectrolytes, with a very large range of ratios between complementary polyions. For this purpose three polyanionspoly(acrylic acid) sodium salt, poly(sodium 4-styrenesulfonate) and poly(sodium vinylsulfonate)and poly-(diallyl-dimethylammonium chloride) as polycation were used. The molar ratio between complementary polyelectrolytes used in CaCO_3 composite synthesis varied between 0 (just polyanions) up to 0.95 (close to the equimolar ratio between ionic charges of complementary polyelectrolytes). The polymer presence into the composite particles, as a function of polyanion structure and the preparation mode, was evidenced by energy dispersive X-ray diffraction and particle charge detection in the supernatant fraction. Scanning electron microscopy was used to provide the particles’ morphology, and Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy was used to determine the polymorph content ratio. The enhanced CaCO_3/ polyanion/polycation microparticles stability in ethylenediamine tetraacetic acid has been also shown compared to CaCO_3/ polyanion microparticles as a function of the molar ratio between complementary polyelectrolytes and the method of introducing the polycation in the crystallogenesis system.
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