Regulating the Morphology of Calcite through Selective Binding of Polymers with Carboxylic Acids

Abstract

Calcite is one of the anhydrous polymorphs of calcium carbonate. When it is found in biominerals, they often have complex morphologies controlled by associated proteins. Asprich, rich in carboxylic acid groups, is one of the representative proteins. In previous studies, peptides originated from Asprich showed extensive modification abilities of calcite morphologies, especially in the presence of magnesium ions. In the present study, synthetic polymers with carboxylic acid groups were utilized to regulate the morphologies of calcite. Poly(acrylic acid) and poly(methacrylic acid) were able to reproduce the controlling ability of Asprich peptides, but poly(ethylene imine) and poly(N-isopropylacrylamide) could not. The observed phenomenon can be explained through selective binding of the anionic polymers to the {hk0} planes of calcite.