Hierarchically structured microparticles formed by interfacial instabilities of emulsion droplets containing amphiphilic block copolymers.
Hierarchically structured microparticles formed by interfacial instabilities of emulsion droplets containing amphiphilic block copolymers.
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DOI：
10.1002/anie.200704863
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发表时间：
2008-02
影响因子：
--
通讯作者：
Jintao Zhu;R. Hayward
中科院分区：
文献类型：
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作者：
Jintao Zhu;R. Hayward
The extraction of organic solvent from oil-in-water emulsions is a simple and widely-used technique to prepare polymeric microparticles and microcapsules for drug delivery applications.[1, 2] Typically, a hydrophobic polymer is first dissolved in an organic solvent that is immiscible or slightly miscible with water; this solution is then emulsified with water and suitable stabilizers to form a single or double emulsion. The solvent is subsequently removed by evaporation or extraction into an excess of the continuous phase, converting the solvent droplets into solid particles or capsules with shapes that are generally spherical as dictated by the interfacial tension between water and the organic phase. Herein we show that when this process is conducted using primarily amphiphilic block copolymers dissolved in the organic phase, solvent removal gives rise to instabilities of the solvent/water interface, generating microparticles with novel hierarchical structures. We studied the behavior of polystyrene–poly (ethylene oxide)(PS-PEO) diblock copolymers, which are known to assemble into a variety of micellar and vesicular morphologies when water is added to solutions of polymer in water-miscible organic solvents.[3–6] We show that, upon removal of organic solvent from emulsion droplets containing PS-PEO, microparticles with foam-like, budding vesicle, and dendritic structures can be prepared. Although a variety of techniques for creating nonspherical particles exist (see Glotzer and Solomon s work [7] for a recent compilation of examples), the current approach offers a simple route for self-assembly of polymers into multicompartment and highsurface-area particle morphologies that may present new opportunities for applications in drug delivery,[8, 9] coatings, and catalysis.[10]To facilitate study of the structural evolution of droplets and to produce microparticles of well-defined sizes, flowfocusing [11, 12] was used in a microcapillary device (Figure 1) to generate solvent droplets with uniform, tunable sizes of 30–50 μm dispersed in water.(For details see the Supporting
