Novel poly(allylaminocarboxylate) ligands, which have a carboxylate and the neighboring arttide group in the same side-chain, were synthesized as model ligands for crystalline CaCO3 biominerals. Poly{N-allyl-malonamate}, poly{N-allyl-succinamate} and poly{4-allylcarbamoyl-butyrate} form 6-, 7- or 8-membered ring intra-side-chain NH.O hydrogen bonds, respectively, between the carboxylate and the neighboring amide NH in the carboxylate anion state, although the formation of each intra-side-chain NH.O hydrogen bond is independent on the stereoisomers of the polymer main-chain. In the polymer ligand-CaCO3 composites, strong binding of polymer ligands to CaCO3 crystals is caused by stabilizing a Ca-O (carboxylate) bond due to the pK(a) shift of carboxylic acid by the NH.O hydrogen bond. Furthermore, the strong Ca binding in CaCO3 composites stabilizes the meta-stable morphology of CaCO3 vaterite crystals. (C) 2004 Elsevier B.V. All rights reserved.