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From:
Jissy Jose, Marlous Kamp, Alfons van Blaaderen and Arnout Imhof (Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 1, 3584 CC, Utrecht, The Netherlands),
“Unloading and reloading colloidal microcapsules with apolar solutions by controlled and reversible buckling”, Langmuir, February 19, 2014,
DOI: 10.1021/la500070s
ABSTRACT: We introduce a new experimental method to encapsulate and release oils and fluorescent molecules, into preformed elastic colloidal microcapsules of PDMS filled siloxane shells, which are cross-linked with tetraethoxysilane. The method uses controlled buckling, where the volume of the capsule is reduced by dissolving the PDMS oil inside the capsule by surfactant micelles. This results in a change in the morphology of the capsule that depends on the ratio of shell thickness to total particle radius (d⁄Rt). Microcapsules of d⁄Rt in the range 0.007–0.05 formed microbowls upon decreasing the inner volume. The amount of oil released or dissolved by the micelles can be directly related to the concentration of surfactant. By tuning the amount of oil released we can make microbowls of variable depth. In addition, we demonstrate that the microbowls can be further used to load different oils like silicone oil, hydrocarbons, and apolar dyes. The elasticity of the capsule wall and the left-over PDMS oil inside the capsule provide the principal driving forces by which one can promote the uptake of different oils, including dissolved dye molecules.
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