Directed nucleation of calcite at a crystal-imprinted polymer surface

The finely tuned properties of natural biominerals and composites reflect the remarkable level of control that is exercised over the size, shape and organization of the constituent crystals(1-4). Achieving this degree of control over synthetic materials might therefore lead to superior material properties. Organic small molecules, polymers or surfactant mesophases have been used to guide the growth and morphology of inorganic materials via steric constraints or structure-directing interactions(5-16). Here we show that synthetic polymers can be imprinted with motifs of crystal surfaces so as to template the growth of specific crystal phases. Our polymers, imprinted with calcite, are able to induce the nucleation of calcite under conditions favouring the growth of aragonite (another polymorph of calcium carbonate). The synthesis of the polymers, based on the principles of molecular imprinting(17-20), involves the adsorption of functional monomers to a calcite surface, followed by co-polymerization with a cross-linker to create an imprint of the crystal surface. Subsequent removal of the calcite template yields a polymer matrix with a surface functionality mirroring the crystal face and able to promote the nucleation of calcite. We expect that the molecular-imprinting approach to directed nucleation can be applied to crystals other than calcite.