Morphogenetic Control of Calcite Crystal Growth in Sulfonic Acid Based Hydrogels

Abstract

In this paper the mineralization of CaCO(3) in various hydrogel matrices is presented. Sulfonic acid based hydrogels were prepared by introduction of sulfonate-containing monomers into a polyacrylamide network. The sulfonate content of polyacrylamide-co-vinylsulfonate and polyacrylamide-co-allylsulfonate decreases during elution of the copolymers in demineralized water, indicating insufficient linking of the sulfonate-bearing monomers within the hydrogel. In contrast to this, acrylamidomethylpropanesulfonate (AMPS) effectively copolymerizes with acrylamide (AAm) monomers. To study the influence of spatial arrangement of ionic functional groups within hydrogel networks on the mineralization of CaCO(3), AMPS copolymers with different degrees of AMPS cross-linking were synthesized. For the mineralization experiments the copolymers were placed into a double-diffusion arrangement. Calcite as the thermodynamically stable modification of CaCO(3) was obtained with a particular morphology. The pseudocubic habitus resembles aggregates obtained by mineralization in pure polyacrylamide. However, closer examination of the aggregates by scanning electron microscopy (SEM) shows that the crystal growth in the AMPS copolymers is different from that observed in polyacrylamide. Whereas the morphology of the calcite aggregates could be fine-tuned by using copolymers with different sulfonate content, the spatial distribution of the ionic functional groups alters the course of crystallization. Calcium ions are locally accumulated due to the heterogeneous distribution of functional sulfonate groups within the copolymer network. Thereby the nucleation of calcite is triggered, resulting in enhanced mineralization.

Mesocrystals—Ordered Nanoparticle Superstructures

“…A morphogenesis change of calcite mesocrystal products from octahedral toward cubo-octahedral can be induced by modifying the neutral polyacrylamide gels with charged acrylamidopropanesulfonate groups. [108] As to be presented in Section 5.1.2, charged groups of gelatin gels can interact with inorganic crystals, whereas polyacrylamide gels are inert and do not directly affect the crystallization. One question arising from these studies is which factors control changes in the morphology of polyacrylamide gel-generated calcite mesocrystals.…”

Calcite Mesocrystals: “Morphing” Crystals by a Polyelectrolyte

“…Interestingly and indicating generality, similar structures with rounded corners and rough surfaces were described before. [54,55] Single-crystal analysis could be used to index their outer faces. [22,55] If the PSS concentration is increased to 0.5 g L À1 at a fixed low Ca 2 + concentration of 1.25 mmol L À1 (Figure 3b), a finer texture of the primary nanoparticulate building blocks is found.…”

“…[54,55] Single-crystal analysis could be used to index their outer faces. [22,55] If the PSS concentration is increased to 0.5 g L À1 at a fixed low Ca 2 + concentration of 1.25 mmol L À1 (Figure 3b), a finer texture of the primary nanoparticulate building blocks is found. This underlines our view that the primary units are nucleated in the proximity of the polyelectrolyte, as more polyelectrolyte can then nucleate a larger number of particles.…”

A novel growth process of calcium carbonate crystals in silk fibroin hydrogel system

“…As a result of cross-linked macromolecules, the biological calcite increased solubility as compared to synthetic calcite. Similarly, calcite with the dissolved morphology was also prepared with polyacrylamide hydrogel [30]. Figure 6f shows the growth state of CaCO 3 in silk fibroin gel for 12 h. Irregular rhombohedral calcite with steps recrystallized under the control of silk fibroin gel and the final crystal size was ~21 μm.…”