A carbonate controlled-addition method for size-controlled calcium carbonate spheres by carboxylic acid-terminated poly(amidoamine) dendrimers

Abstract

Size-controlled calcium carbonate particles were obtained using a ‘carbonate controlled-addition method’ with G0.5 poly(amidoamine) (PAMAM) dendrimer with carboxylate groups at the external surface. An aqueous ammonium carbonate solution was added to an aqueous solution of the dendrimer and CaCl2 at different time periods (3 min, 1 h or 24 h) and was stirred for 1 day. Both crystal phases obtained at incubation times of 1 and 24 h were vaterite. The dendrimer–CaCl2 solution incubated for 3 min produced vaterite particles that coexisted with calcite. The average particle size of the spheres decreased from 2.2±0.2 to 0.61±0.24 μm with an increase in the incubation time of the dendrimer–CaCl2 solution. When the products were kept in the reaction mixtures for 3 days, the CaCO3 phase of the precipitates obtained after incubating the dendrimer–CaCl2 solution for 3 min and 1 h was calcite. However, the product obtained after incubating for 24 h was vaterite. The present results demonstrate that the interaction and the reaction kinetics of the dendrimer–Ca2+ complex have an important role in the mineralization and stabilization of CaCO3 particles. Vaterite particles were obtained by a ‘carbonate controlled-addition method’ by G0.5 poly(amidoamine) (PAMAM) dendrimer with carboxylate groups at the external surface. The average particle sizes of the spheres decreased from 2.2±0.2 to 0.61±0.24 μm and the stability of the spheres increased with an increase in the incubation time of the G0.5–CaCl2 solution from 3 min to 24 h. The interaction and reaction kinetics of the dendrimer–Ca2+ complex have an important role in the mineralization of CaCO3.