CaCO3 was mineralized from solutions supersaturated only by poly(acrylic acid) (PAA), without bubbling any CO2 gas in the solution. For example, a layer of CaCO3 was built up on the surface of a chitosan membrane from a supersaturated aqueous solution containing CaCl2, Na2CO3, and PAA. In this newly developed method, the PAA alone suppresses the precipitation of CaCO3 from the bulk solution, and therefore, increases the supersaturated concentration. This concentration is estimated to be the same order as that attained in the method in which both CO2 gas and PAA were used. At the same time, PAA supplies nucleation fields by forming a polymer complex with chitosan. The crystal system obtained was different from those obtained when using CO2 gas. Self-organization of aragonite crystallites led to the formation of uniform, concentric, or branching patterns in the surface-domain structure. These patterns had morphologies similar to those discovered by other researchers, typically in the crystallization of ascorbic acid. Thicker layers of CaCO3 could be formed on chitosan membranes, the surfaces of which had been converted to a polyelectrolyte complex (PEC) by exposure to PAA solution before the onset of mineralization. Under certain conditions, the CaCO3 layer had a small spherical curvature, similar to a half-lens, and generated Newton's ring pattern from the interference fringes of visible light. (C) 2004 Wiley Periodicals, Inc.