Effect of Poly(acrylic acid) on Crystallization of Calcium Carbonate in a Hydrogel
In a biological system, biomineral is regulated by a controlled mass transfer as well as an assistance of soluble and insoluble macromolecules. Inspired by biomineralization, calcium carbonate morphologies were controlled by addition of anionic polyelectrolytes in a diffusion-limited matrix. As carbonate ions were slowly diffused into the agarose hydrogel containing calcium ions and poly(acrylic acids) (PAA), either elliptical or spherical calcite were formed depending on the concentration of PAA and the position of the hydrogel. It was proposed that calcium carbonate morphologies could be determined by chain conformation of polyelectrolytes resulted from initial pH. In a low PAA concentration, a steep increase of initial pH led to anisotropic templates composed of stretched PAA, resulting in elliptical calcite. In contrast, in a high PAA concentration of PAA, slow increase of pH led to gradual growth of isotropic precursors, resulting in spherical calcite. Control of calcium carbonate in a diffusion-limited system is beneficial to understand the biomineralization process in organic matrices, but also to produce calcite particles applicable to the industrial fields.