Selective nucleation of calcium carbonate polymorphs: Role of surface functionalization and poly(vinyl alcohol) additive

A model system involving a synthetic polyamide fiber and a water-soluble polymer for the selective nucleation of polymorphs of calcium carbonate crystals under specific experimental conditions is described. The functional groups at the surface of both commercially available and chemically modified polyamide fibers induced calcite nucleation. A water-soluble additive, poly(vinyl alcohol) (PVA), enhanced the selectivity of the polymorph nucleation. The unmodified fiber preadsorbed with PVA molecules induced vaterite nucleation, whereas the chemically modified fiber surface in the presence of PVA nucleated aragonite crystals. Morphological characterization of the polymorphs was done using scanning electron microscope (SEM), and the nature of the crystal lattice was identified using X-ray diffraction studies. Elemental analyses of the crystals indicated the absence of a soluble macromolecular additive inside the crystal lattice. On the basis of these results, a possible mechanism for the nucleation of CaCO3 polymorphs is proposed.