Facile Fabrication of Silica Nanocapsules with Well-Defined Mesoporous Shell via a Poly(N, N-dimethylaminoethyl methacrylate)-Assisted Self-Template Etching Process

The success of self-template methods for fabrication of hollow silica microspheres largely depends on the stabilization of the outmost silica layer by a polymer ligand. In this study, the cationic polyelectrolyte poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA), combining the synergistic electrostatic attractions and hydrogen bonding interactions, was found to be able to form a robust protective layer on the surface of silica spheres. The structural characteristics of obtained PDMAEMA-coated silica microspheres were detailedly characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR) and Transmission Electron Microscopy (TEM). The etching process was monitored by TEM and the shell features of prepared hollow silica nanocapsules were characterized by nitrogen adsorption–desorption isotherm technique. The results show that the PDMAEMA protective layer not only can effectively stabilize the outmost silica layer against etching, but also actively capture the negative silicate oligomers for shell-growth, allowing more effective transformation of silica spheres into yolkshell or hollow nanoparticles with pronounced hollow nature and well-defined mesoporous shell structure.