This article describes an experimentally versatile strategy for producing inorganic/organic nanocomposites, with control over the microstructure at the nano-and mesoscales. Taking inspiration from biominerals, CaCO 3 is coprecipitated 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 X-ray diffraction 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, it is shown 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 atomic force microscopy studies of worm occlusion in calcite, which reveal fl attening 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 reveal that they have hardnesses approaching those of biogenic calcites.

Recently, it has become clear that a range of nanoparticles can be occluded within single crystals to form nanocomposites. Calcite is a much-studied model, but even in this case we have yet to fully understand the details of the nanoscale interactions at the organic-inorganic interface that lead to occlusion. Here, a series of diblock copolymer nanoparticles with well-defined surface chemistries were visualized interacting with a growing calcite surface using in situ atomic force microscopy. These nanoparticles comprise a poly(benzyl methacrylate) (PBzMA) core-forming block and a non-ionic poly(glycerol monomethacrylate) (Ph-PGMA), a carboxylic acid-tipped poly(glycerol monomethacrylate) (HOOC-PGMA), or an anionic poly(methacrylic acid) (PMAA) stabilizer block. Our results reveal three modes of interaction between the nanoparticles and the calcite surface: (i) attachment followed by detachment, (ii) sticking to and "hovering" over the surface, allowing steps to pass beneath the immobilized nanoparticle, and (iii) incorporation of the nanoparticle by the growing crystals. By analyzing the relative contributions of these three types of interactions as a function of nanoparticle surface chemistry, we show that ∼85% of PMAA-PBzMA nanoparticles either "hover" or become incorporated, compared to ∼50% of the HOOC-PGMA-PBzMA nanoparticles. To explain this difference, we propose a two-state binding mechanism for the anionic PMAA-PBzMA nanoparticles. The "hovering" nanoparticles possess highly extended polyelectrolytic stabilizer chains and such chains must adopt a more "collapsed" conformation prior to successful nanoparticle occlusion. This study provides a conceptual framework for understanding how sterically stabilized nanoparticles interact with growing crystals, and suggests design principles for improving occlusion efficiencies.

This article addresses recent advances in the application of microscopy techniques to characterize crystallization processes as they relate to biomineralization and bio-inspired materials synthesis. In particular, we focus on studies aimed at revealing the role organic macromolecules and functionalized surfaces play in modulating the mechanisms of nucleation and growth. In nucleation studies, we explore the use of methods such as in situ transmission electron microscopy, atomic force microscopy, and cryogenic electron microscopy to delineate formation pathways, phase stabilization, and the competing effects of free energy and kinetic barriers. In growth studies, emphasis is placed on understanding the interactions of macromolecular constituents with growing crystals and characterization of the internal structures of the resulting composite crystals using techniques such as electron tomography, atom probe tomography, and vibrational spectromicroscopy. Examples are drawn from both biological and bio-inspired synthetic systems.

Binary mixtures of RAFT macromolecular chain transfer agents are utilized to rationally design anionic diblock copolymer nanoparticles via PISA. The role of carboxylate groups in directing calcite growth within copolymer worm gels is investigated.