Nanotemplating of Calcium Phosphate Using a Double-Hydrophilic Block Copolymer

Abstract

Atom transfer radical polymerization technique was used to synthesize poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-b-PMAA) copolymer, which was employed as a template for the controlled precipitation of calcium phosphate from aqueous solution at different pH values. The interactions between polymer and inorganic ions were studied using Ca2+ ion selective electrode, which indicated a possible weak interaction between Ca2+ and PEO segments, in addition to the interaction between Ca2+ and MAA segments. Two interesting superstructures consisting of an organized inorganic/organic hybrid material were characterized by electron microscopy. At pH ∼4.0 a nested structure consisting of hybrid nanofilaments was obtained. The fibers originate from a core of a size similar to that of the primary polymer aggregates, suggesting that cooperative interactions at a local level between dissolving calcium phosphate clusters and disassembling polymer segments may be responsible for the highly anisotropic character of the secondary growth process. At pH ∼9.0 fractal growth morphology was obtained through the mineralization process. Such calcium phosphate/polymer nanohybrids with complex morphologies are interesting and might also be useful as novel ceramic precursors, reinforcing fillers, or biomedical implants.