Abstract
Core-shell polystyrene-silica spheres with diameters of 800 nm and 1.9 μm were synthesized by soap-free
emulsion and dispersion polymerization of the polystyrene core, respectively. The polystyrene spheres were used as
templates for the synthesis of silica shells of tunable thickness employing the Sto¨ber method. The polystyrene template was removed by thermal decomposition at 500 °C, resulting in smooth
silica shells of well-defined thickness (15-70 nm). The elastic response of these hollow spheres was probed by atomic
force microscopy (AFM). A point load was applied to the particle surface through a sharp AFM tip, and successively
increased until the shell broke. In agreement with the predictions of shell theory, for small deformations the deformation
increased linearly with applied force. The Young’s modulus (18 + - 6 GPa) was about 4 times smaller than that of
fused silica [Adachi and Sakka J. Mater. Sci. 1990, 25, 4732] but identical to that of bulk silica spheres (800 nm)
synthesized by the Stöber method, indicating that it yields silica of lower density. The minimum force needed to
irreversibly deform (buckle) the shell increased quadratically with shell thickness.
Original language | Undefined/Unknown |
---|---|
Pages (from-to) | 2711-2717 |
Number of pages | 7 |
Journal | Langmuir |
Volume | 25 |
Issue number | 5 |
Publication status | Published - 2009 |