Synthesis and characterization of self-assembled block copolymer templated calcium phosphate nanocomposite gels

Abstract

Self-assembled macroscale calcium phosphate–copolymer nanocomposite gels were prepared using a bottom-up approach from aqueous solutions. Amphiphilic block copolymer micelles in aqueous solutions were used as templates for the growth of calcium phosphate nanocrystals and then allowed to self-assemble in solution to form thermoreversible nanocomposite gels. NMR and XRD showed that calcium phosphate precipitation in a Pluronic^® F127 copolymer gel resulted in a disordered brushite phase while the calcium phosphate–poly(2-diethylaminoethyl methacrylate) (PDEAEM) modified Pluronic^® F127 pentablock copolymer nanocomposite contained the same brushite phase along with a calcium dihydrogen phosphate second phase. TEM, SAXS, and NMR experiments confirmed that the calcium phosphate precipitated on and interacted with the polymer micelles forming an organized network of ∼20 nm diameter nanospheres. The resulting polymer–calcium phosphate nanocomposite gels contained between 6.5 and 15 weight percent calcium phosphate, which could be controlled by manipulating the pH of the constituent solutions.