Poly(ethylene oxide)- poly(propylene oxide)- poly(ethylene oxide) ((EO)(20)-(PO)(72)-(EO)(20)) and 0(hydroxy isopropyl) chitosan (HPCHS) were employed as control agents of calcium carbonate crystal growth. The effect of the concentrations of polymers, [Ca2+] and [CO32-], the ratios of [Ca2+]-[CO32-] and the initial pH of the solutions were investigated. The obtained CaCO3 particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The particles are mainly calcite with various morphologies; their size and morphologies are influenced by the polymer content. For (EO)(20)-(PO)(72)-(EO)(20) systems, the initial pH has a notable influence; but in the HPCHS solution pH shows little influence. The ratio of [Ca2+]-[CO32-] clearly affects the CaCO3 particle size and aggregation degree. HPCHS showed more significant influence on CaCO3 crystallization than (EO)(20)-(PO)(72)-(EO)(20). The mechanisms of the CaCO3 crystallization as controlled by (EO)(20)-(PO)(72)-(EO)(20) and HPCHS are proposed and demonstrated by the molecular dynamics simulations. (C) 2009 Elsevier B.V. All rights reserved.