Synthesis of monodisperse SiO2/P(DVB-SO3H)/SiO2/P(DVB-SO3H) tetra-layer polyelectrolyte microspheres and the corresponding hollow P(DVB-SO3H)polyelectrolyte microspheres with a shell-in-shell structure

The hollow poly(divinylbenzyl sulfonic acid) (P(DVB-SO3H)) polyelectrolyte (PE) microspheres with a shell-in-shell structure were prepared by selective etching of the silica core and third-layer with hydrofluoric acid from the corresponding SiO2/P(DVB-SO3H)/SiO2/P(DVB-SO3H) tetra-layer PE microspheres, which were synthesized by a combination of the controlled sol–gel hydrolysis of tetraethylorthosilicate (TEOS) for the preparation of silica core and third-layer, and the distillation precipitation polymerization of divinylbenzene (DVB) in acetonitrile for the construction of polydivinylbenzene (PDVB) layer with subsequent surface modification of the phenyl group to afford P(DVB-SO3H) PE second and outer shell-layer. The silica/poly(divinylbenzylsulfonate 4-vinylpyridinium) (SiO2/P(DVB-SO3−VPyH+) core-shell PE microspheres were prepared by the neutralization of 4-vinylpyridine (4-VPy) with sulfonic acid groups on the surface of SiO2/P(DVB-SO3H) core-shell microspheres, which were synthesized by the distillation precipitation polymerization of DVB in the presence of 3-(methacryloxy)propyl trimethacrylate (MPS)-modified silica nanoparticles as seeds to afford SiO2/PDVB core-shell microspheres with subsequent sulfonation of the phenyl groups of PDVB shell in concentrated sulfuric acid. SiO2/P(DVB-SO3H)/SiO2/P(DVB-SO3H) tetra-layer PE microspheres were synthesized by sulfonation of SiO2/P(DVB-SO3−VPyH+)/SiO2/PDVB tetra-layer microspheres in concentrated sulfuric acid, which were prepared by distillation precipitation polymerization of DVB with MPS-modified SiO2/P(DVB-SO3−VPyH+)/SiO2 tri-layer microspheres as seeds via coating of silica-layer onto SiO2/P(DVB-SO3−VPyH+) nanoparticles. The morphology and properties of the resultant microspheres, and the corresponding hollow P(DVB-SO3H) microspheres with a shell-in-shell structure were characterized by transmission electron microscopy (TEM), Fourier transform spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS).