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Polymer hollow particles with controllable holes in their surfaces


Colloidal particles with hollow interiors play important roles in microencapsulation—a process that has found widespread use in applications such as controlled release of drugs, cosmetics, inks, pigments or chemical reagents; protection of biologically active species; and removal of pollutants1,2,3,4,5. The hollow particles are most commonly prepared by coating the surfaces of colloidal templates with thin layers of the desired material (or its precursor), followed by selective removal of the templates by means of calcination or chemical etching5. This simple and straightforward approach works for a variety of materials that include polymers, ceramics, composites and metals5,6,7,8,9,10,11,12,13,14. For polymers, methods such as emulsion polymerization, phase separation, crosslinking of micelles and self-assembly have also been demonstrated for generating hollow structures15,16,17,18,19,20. However, diffusion through these closed shells with pores <10 nm is often a slow process. To solve this problem, macroporous capsules have been fabricated by organizing colloids around liquid droplets to form colloidosomes or by controlling the mixing of liquid droplets21,22,23. Here we report the preparation of another class of macroporous capsules—polymer shells with controllable holes in their surfaces. After loading of functional materials, the holes can be closed by means of thermal annealing or solvent treatment.

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Figure 1: Schematic illustration of three major steps involved in the formation of PS hollow particles with holes in their surfaces.
Figure 2: Electron microscopy images of PS hollow particles with holes in their surfaces that were derived from PS solid beads.
Figure 3: Fluorescence and electron microscopy images of PS beads loaded with various functional materials.
Figure 4: SEM images of PMMA solid beads and their bowl-shaped derivatives.

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This work was supported in part by an AFOSR-MURI grant on smart skin materials awarded to the University of Washington and a fellowship from the David and Lucile Packard Foundation. Y.X. is a Camille Dreyfus Teacher Scholar (2002–2007). S.H.I. and U.J. were also partially supported by the Post-Doctoral Fellowship Program of the Korean Science and Engineering Foundation (KOSEF). This work used the Nanotech User Facility at the University of Washington, a member of the National Nanotechnology Infrastructure Network funded by the NSF.

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Correspondence to Younan Xia.

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Supplementary figures S1 and S2; supplementary table S1 (PDF 106 kb)

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Hyuk Im, S., Jeong, U. & Xia, Y. Polymer hollow particles with controllable holes in their surfaces. Nature Mater 4, 671–675 (2005).

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