The mechanism of the morphogenesis of CaCO₃ in the presence of poly(ethylene glycol)-b-poly(methacrylic acid)

Abstract

The morphogenesis of crystalline CaCO3 in calcite modification was systematically investigated in the presence of poly(ethylene glycol)-b-poly(methacrylic acid) with respect to pH, polymer and mineral concentration. A variety of different particle morphologies was observed and at least two different mechanisms for the formation of the final CaCO3 structures are proposed. At low polymer concentration or pH, the basis of the mechanism is that the polymer could selectively adsorb onto specific crystal surfaces leading to morphologies elongated along the crystal c-axis. At low pH, macroscopic elongated crystals were found resulting from a slow growth process, whereas at high pH or high polymer concentration, spherical structures dominated originating from a more complicated growth scenario: polymer adsorption onto the nanocrystals with subsequent defined aggregation into a superstructure. Here, the elongated crystal is stabilized on the nanometer scale with a growth self-termination and an acting electric multipole field arranges later nucleated particles into the observed superstructures.