Crystallization and morphological control of calcium carbonate by functionalized triblock copolymers

A systematic investigation on the influence of a series of synthesized triblock copolymers (PEG-b-PAA-b-PS, poly(ethylene glycol)-block-poly(acrylic acid)-block-poly(styrene)) on the crystallization, morphology and size of CaCO3 crystals was reported. The crystallization of vaterite is favored in the presence of copolymer 1 (PEG112-b-PAA40-b-PS37), which strongly depends on the polymer concentration. The fraction of spherical vaterite increased with the increase of the concentrations of copolymer 1. The molecular dynamics minimized structure of copolymer 2 (PEG112-b-PAA18-b-PS55) showed a close match between the spacings of the parallel-oriented carboxylate groups and the spacings of calcium ions in the calcite surface, which is favorable to the crystallization of calcite at all determined concentrations. The triblock copolymers could prohibit the phase transformation of vaterite to calcite, depending upon the block length of PAA middle segment and the concentration of the copolymers.