Formation of Periodically-Ordered Calcium Phosphate Nanostructures by Block Copolymer-Directed Self-Assembly

Structuring ionic solids at the nanoscale with block copolymers (BCPs) is notoriously difficult due to solvent incompatibilities and strong driving forces for crystallization of the inorganic material. Here, we demonstrate that elucidating pathway complexity in the BCP-directed self-assembly of an ionic solid, amorphous calcium phosphate (ACP), is a key component in obtaining nanostructured, bulk composite materials in which the nanostructure is the result of thermodynamically controlled BCP self-assembly, i.e., exhibiting sequences of bulk morphologies as known from typical equilibrium BCP phase diagrams. Specifically, we identify three critical pathway “decision points” for the evaporation-induced self-assembly of composites from ultrasmall, organosilicate-modified amorphous calcium phosphate nanoparticles (osm-ACP-NPs) and poly(isoprene)-block-poly(2-(dimethylamino)ethyl methacrylate) (PI-b-PDMAEMA) block copolymers. Using this strategy enabled us to obtain composites with hexagonal, cubic network, and...