The carboxyl group interacts strongly with calcium ions, indicating that the hydrophilic polymers with the functional groups of -COOH should exert a great impact on the crystal design of calcium carbonate (CaCO3). In this paper, three copolymers were synthesized and subsequently used as additives to control the crystallization and aggregation behaviors of CaCO3. The results show that: (1) the hard-segmented copolymer could be employed as a crystal modifier of calcite; and (2) the introduction of soft segments into the hard-segmented backbone could prohibit the phase transformation of vaterite to calcite, depending upon the structure and the concentration of the synthesized copolymers. The relationship between the properties of the dispersed copolymers and the polymorphism of CaCO3 has also been discussed. (C) 2007 Elsevier B.V. All rights reserved.