Hidden Structural Features of Multicompartment Micelles Revealed by Cryogenic Transmission Electron Tomography
Hidden Structural Features of Multicompartment Micelles Revealed by Cryogenic Transmission Electron Tomography
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DOI：
10.1021/nn504197y
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发表时间：
2014-11-01
期刊：
影响因子：
17.1
通讯作者：
Mueller, Axel H. E.
中科院分区：
文献类型：
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作者：
Loebling, Tina I.;Haataja, Johannes S.;Mueller, Axel H. E.
在材料和软物质纳米科学中对越来越复杂的纳米结构的需求也需要复杂的表征工具来可靠地可视化和解释内部形态特征。在这里，我们解决这两个方面，并提出了合成概念的纳米颗粒外围区室化，以及他们在原位层析表征。我们首先形成带负电荷的球形多隔室胶束从两性三嵌段共聚物在水介质中，然后由互插复合物（IPEC）形成的阴离子电晕与双亲水性阳离子/中性二嵌段共聚物。在1：1化学计量比的阴离子和阳离子电荷下，如此形成的IPEC是电荷中性的，因此与溶液（水）相分离。离子接枝物的高链密度通过接枝二嵌段共聚物的中性PEO冠提供空间稳定性，并抑制IPEC的塌陷;相反，密集接枝导致垂直于胶束核心取向的限定纳米域。我们分析了复杂的和纯有机车厢，在原位，通过低温透射电子显微镜（cryo-TEM）和断层扫描（cryo-ET）的3D安排。我们研究了阳离子和非离子嵌段的嵌段长度对IPEC形态的影响，虽然2D cryo-TEM投影显示了相似的形态，但cryo-ET和计算3D重建揭示了隐藏的结构特征，例如，平面IPEC刷从胶束核心发出。
The demand for ever more complex nanostructures in materials and soft matter nanoscience also requires sophisticated characterization tools for reliable visualization and interpretation of internal morphological features. Here, we address both aspects and present synthetic concepts for the compartmentalization of nanoparticle peripheries as well as their in situ tomographic characterization. We first form negatively charged spherical multicompartment micelles from ampholytic triblock terpolymers in aqueous media, followed by interpolyelectrolyte complex (IPEC) formation of the anionic corona with bis-hydrophilic cationic/neutral diblock copolymers. At a 1:1 stoichiometric ratio of anionic and cationic charges, the so-formed IPECs are charge neutral and thus phase separate from solution (water). The high chain density of the ionic grafts provides steric stabilization through the neutral PEO corona of the grafted diblock copolymer and suppresses collapse of the IPEC; instead, the dense grafting results in defined nanodomains oriented perpendicular to the micellar core. We analyze the 3D arrangements of the complex and purely organic compartments, in situ, by means of cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET). We study the effect of block lengths of the cationic and nonionic block on IPEC morphology, and while 2D cryo-TEM projections suggest similar morphologies, cryo-ET and computational 3D reconstruction reveal otherwise hidden structural features, e.g., planar IPEC brushes emanating from the micellar core.