Calcium carbonate films and helices grown in solutions of poly(aspartate)

Addition of charged polypeptides, in particular poly(aspartate), to supersaturated solutions of calcium carbonate (CaCO3) leads to unusual morphologies in the inorganic phase. The polymer causes deposition of CaCO3 films, which appear to act as membranous substrates that mediate the growth of CaCO3 crystals. Spherulitic vaterite aggregates with helical extensions, and distorted calcite crystals that contain spiral pits, have been produced. A correlation has been noted between the structures of the crystalline films and those of the crystal aggregates associated with them: i.e. films of spherulitic texture yield electron diffraction patterns characteristic of vaterite and support the growth of spherulitic vaterite aggregates whereas calcitic single-crystal mosaic films carry rhombohedral calicite crystals. These films and aggregates exhibit features reminiscent of the morphologies observed in biogenic minerals. (C) 1998 Elsevier Science B.V. All rights reserved.