Synthesis of polymer/zirconium hydroxide core–shell microspheres and the hollow porous zirconium oxide microspheres

Narrow-disperse poly(N,N′-methylenebisacryamide-co-methacrylic acid)/zirconium hydroxide (P(MBA-co-MAA)/Zr(OH)4) core–shell composite microspheres were synthesized by the controlled sol–gel hydrolysis of inorganic zirconium n-butoxide (Zr(OBu)4) precursor in ethanol and acetonitrile mixed solvent with P(MBA-co-MAA) microspheres as templates. The thickness of the outer inorganic Zr(OH)4 shell-layer was well-controlled via altering the mass ratio of Zr(OBu)4 to P(MBA-co-MAA) core particles as well as the water used for the hydrolysis. The corresponding hollow porous zirconium oxide (ZrO2) microspheres were obtained after the selective removal of P(MBA-co-MAA) core via the calcination of P(MBA-co-MAA)/Zr(OH)4 core–shell microspheres under 550 °C for 4 h in air. The structure and morphology of the resultant core–shell microspheres and the hollow porous ZrO2 microspheres were characterized by transmission electron microscopy (TEM), STEM together with EDX spectrum, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, micromeritic analyzer, and thermogravimetric (TGA) analysis.