Polymorph control of calcium carbonate films in a poly(acrylic acid)-chitosan system

We successfully controlled the crystal structure of calcium carbonate films grown on a 260 degrees C-baked chitosan using a single chemical species of poly( acrylic acid) (PAA) as a soluble agent. The planar morphology of the calcium carbonate films was basically ascribed to the guided growth by PAA molecules anchored to chitosan on a glass substrate. Selective production of a particular crystal structure, such as calcite, aragonite, or vaterite, was achieved by variation of the molecular weight of PAA and the temperature of the solution. The control of the polymorphs was ascribed to a templating effect due to the arrangement of PAA molecules anchored on the surface of chitosan.