Structure and Properties of Nanocomposites Formed by the Occlusion of Block Copolymer Worms and Vesicles Within Calcite Crystals

This article describes an experimentally versatile strategy for producing inorganic/ organic nanocomposites, with control over the microstructure at the nano- and meso-scales. Taking inspiration from biominerals, CaCO3 is co-precipitated with anionic diblock copolymer worms or vesicles to produce single crystals of calcite occluding a high density of the organic component. This approach can also be extended to generate complex structures in which the crystals are internally patterned with nano-objects of differing morphologies. Extensive characterization of the nanocomposite crystals using high resolution synchrotron powder XRD and vibrational spectroscopy demonstrates how the occlusions affect the short and long-range order of the crystal lattice. By comparison with nanocomposite crystals containing latex particles and copolymer micelles, we show that the effect of these occlusions on the crystal lattice is dominated by the interface between the inorganic crystal and the organic nano-objects, rather than the occlusion size. This is supported by in situ AFM studies of worm occlusion in calcite, which reveal flattening of the copolymer worms on the crystal surface, followed by burial and void formation. Finally, the mechanical properties of the nanocomposite crystals are determined using nanoindentation techniques, which reveals that they have hardnesses approaching those of biogenic calcites.