Self-assembly of lamellar clays to hierarchical microarrays

We uncover new self-assembled morphologies such as lengthy rods, dendrites, and rod-bundles from the lamellar clays. The unique formation of lengthy rod (ca. 0.3 mu m in diameter and up to 40 mu m in length), hierarchical rod-bundle (ca. 3 mu m in diameter) and dendrite-like arrays was observed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). These microstructures were formed by self-piling the primary units of lamellar clay stacks that were intercalated with poly(oxypropylene)-amine salts (POP) within the interlayer spaces. Depending on the clay dimensions, the high-aspect-ratio mica (300-500 nm for plate dimension) tends to form lengthy rods and rod-bundles, whereas montmorillonite (80-100 nm for average plates) often leads to less orderly dendrites. The self-assemblies, elucidated by TEM and AFM micrograms, may involve two piling directions of the primary stack units by face-to-face alignment and edge-to-edge POP interaction. These hierarchical microstructures with different morphologies are controllable by selecting the self-assembling procedures, such as direct water evaporation and toluene/water interfacial film formation.