Alternating Silica/Polymer Multilayer Hybrid Microspheres Templates for Double-shelled Polymer and Inorganic Hollow Microstructures

Alternating silica/polymer tetra- and penta-layer hybrid microspheres were first prepared via combined inorganic sol-gel reaction and distillation-precipitation polymerization, pH-responsive poly(methacrylic acid) (PMAA) hollow microspheres with asymmetric double-shells were produced after HF etching of the silica layers in the SiO2/PMAA tetra-layer microspheres with different degrees of cross-linking in the two PMAA layers. On the other hand, silica core-double shell hollow microspheres were obtained by calcination of the alternating silica/PMAA penta-layer microspheres. The resulting hollow polymer and silica microspheres with hierarchical structures were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis, dynamic laser scattering (DLS), and confocal laser scanning microscopy (CLSM) measurements.