Control of crystal growth processes by block-copolymers

In crystallization processes from solution, parameters like crystal habit, grain size, grain size distribution, concentration and type of impurities/dopants can be controlled by addition of admixtures. Amphipolar diblock-copolymers (DBCP's) are shown to have unique effects on crystallization processes from solution. With poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-b-PMAA) as admixture in concentrations in the 100 ppm range, control of nucleation density and crystallization of calcium carbonate (CaCO3) is possible. Crystal growth perpendicular to {hk0}-faces of calcite is retarded, whereas the growth perpendicular to {104}-faces remains undisturbed. In the case of growth of zincite (ZnO), the grain size distribution is narrowed and crystal growth in [001]-direction is slowed down. To explain the special effect of the DBCP's on crystal growth, a simple model is proposed.