Oriented Vaterite CaCO3Tablet-Like Arrays Mineralized at Air/Water Interface through Cooperative Regulation of Polypeptide and Double Hydrophilic Block Copolymer

Abstract

Highly oriented vaterite CaCO 3 tablet-like arrays were formed at the air/water interface through the cooperative mineralization regulated by polypeptide and double hydrophilic block copolymer under ambient conditions. The nearly parallel arrangement of CaCO 3 vaterite tablets at the air/water interface shows the remarkable resemblance to the morphology of nacreous layers. The poly(aspartic acid) (PASP) with high molecular weight (M w = 11 000) and low solubility in water promoted the formation of vaterite tablets at the air/water interface, and stabilized the vaterite tablets by aggregation at the air/water interface and adsorption at the surface of vaterite tablets. Meanwhile, the highly hydrophilic poly(ethylene glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) played an important role in regulating the arrangement and orientation of vaterite CaCO 3 tablets, leading to the oriented tablet-like arrays at the air/water interface. Detailed experiments revealed that hydrophilic PEG-b-PMAA alone did not produce any form of CaCO 3 crystals at the air/water interface, but could induce the formation of calcite CaCO 3 particles in the water phase. However, high molecular weight PASP alone led to the formation of disk-like vaterite particles composed of helically aggregated nanoplates at the air/water interface, suggesting the regulating role of PEG-b-PMAA in the growth of vaterite tablet arrays. These results reported here provide a better understanding of the growth mechanism of nacreous layers and shells in nature.