Precipitated calcium carbonate hybrid hydrogels: Structural and mechanical properties

Hybrid hydrogels consisting of 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA) prepolymers, and precipitated calcium carbonate (PCC) were prepared through a two-stage photocross-linking process. To elucidate the effects of PCC morphology, size, aspect ratio, and concentration to the structural and mechanical properties of the hybrid hydrogels, two types of PCC, including rhombohedral calcite with particle size of 50-150 nm and needle-shape aragonite with particle size of 380-1250 nm and aspect ratio of 4.2-6.6, were investigated. In all cases, the PCCs were found randomly dispersed in the hydrogel network. A significant increase in both shear and Young's moduli was observed in hybrid gels with larger PCC particle size and aspect ratio 40-180 MPa from aragonite and 20-150 MPa from calcite compared, to 3 MPa in the neat hydrogels (60/40 wt % HEMA/MMA). Consistent with modulus data, the network mobility decreased with increasing particle concentration, particle size, and aspect ratio, and the hybrid gels from calcite PCC showed more efficient stress relaxation in comparison to that from aragonite PCC particles.