Multiscale Filler Structure in Simplified Industrial Nanocomposite Silica/SBR Systems Studied by SAXS and TEM
Multiscale Filler Structure in Simplified Industrial Nanocomposite Silica/SBR Systems Studied by SAXS and TEM
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DOI：
10.1021/ma302248p
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发表时间：
2013-01-08
期刊：
影响因子：
5.5
通讯作者：
Oberdisse, Julian
中科院分区：
文献类型：
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作者：
Baeza, Guilhem P.;Genix, Anne-Caroline;Oberdisse, Julian
简化二氧化硅 (Zeosil 1165 MP) 和 SBR（140k 带有硅烷醇端基）纳米复合材料是通过混合较少数量的工业应用成分配制而成的。监测混合过程中样品的热机械历史并调整至相同的最终温度。通过透射电子显微镜 (TEM) 和甚小角 X 射线散射 (SAXS) 研究了大尺寸至微米的填料结构。提出了一个完整的定量模型，从初级二氧化硅纳米颗粒（半径约为 10 nm）延伸到纳米颗粒聚集体，直至典型横向尺寸为 150 nm 的微米级分支。对 TEM 图片的图像分析可得出纯聚合物区域的分数，这些区域在大型填料网络的分支之间延伸。该网络与通过散射测量的平均维度为 2.4 的分形兼容。在较小的长度尺度上，在分支内部，存在小的二氧化硅聚集体。它们的平均半径是从 Kratky 分析中推导出来的，对于此处研究的所有二氧化硅部分，其范围在 35 至 40 nm 之间（Phi(si) = 8-21% vol.）。我们分析的核心部分是通过代表聚集体的多分散球体的模拟结构因子来描述聚集体间的相互作用。假设聚集体尺寸的多分散性为 30%，并且这些聚集体之间的相互作用用硬核排斥势来描述。使用相同的尺寸分布来评估多分散形状因子。与实验强度的比较可以确定平均聚集体容量（假设分布中的所有聚集体相同，在 31% 到 38% 之间，具体取决于 Phi(si)），从而确定聚集体数量（约 45，分布范围较大）。由于骨料容量和纯聚合物区域的影响，分支中骨料的体积分数高于 Phi(si)。骨料之间的排斥力对表观等温压缩性有很大影响：它会导致特征性的低 q 值下降，这不能解释为我们数据中骨料质量的减少。此外，SBR 基体中这些二氧化硅结构的增强效果通过振荡剪切进行表征，并通过基于相同骨料容量的模型进行描述。最后，我们的结果表明，可以以自洽和定量的方式分析工业来源的纳米复合材料中相互作用聚集体的复杂结构。
Simplified silica (Zeosil 1165 MP) and SBR (140k carrying silanol end-groups) nanocomposites have been formulated by mixing of a reduced number of ingredients with respect to industrial applications. The thermo-mechanical history of the samples during the mixing process was monitored and adjusted to identical final temperatures. The filler structure on large scales up to micrometers was studied by transmission electron microscopy (TEM) and very small-angle X-ray scattering (SAXS). A complete quantitative model extending from the primary silica nanoparticle (of radius approximate to 10 nm), to nanoparticle aggregates, up to micrometer-sized branches with typical lateral dimension of 150 nm is proposed. Image analysis of the TEM-pictures yields the fraction of zones of pure polymer, which extend between the branches of a large-scale filler network. This network is compatible with a fractal of average dimension 2.4 as measured by scattering. On smaller length scales, inside the branches, small silica aggregates are present. Their average radius has been deduced from a Kratky analysis, and it ranges between 35 and 40 nm for all silica fractions investigated here (Phi(si) = 8-21% vol.). A central piece of our analysis is the description of the interaggregate interaction by a simulated structure factor for polydisperse spheres representing aggregates. A polydispersity of 30% in aggregate size is assumed, and interactions between these aggregates are described with a hard core repulsive potential. The same distribution in size is used to evaluate the polydisperse form factor. Comparison with the experimental intensity leads to the determination of the average aggregate compacity (assumed identical for all aggregates in the distribution, between 31% and 38% depending on Phi(si)), and thus aggregation number (ca. 45, with a large spread). Because of the effect of aggregate compacity and of pure polymer zones, the volume fraction of aggregates is higher in the branches than Phi(si). The repulsion between aggregates has a strong effect on the apparent isothermal compressibility: it leads to a characteristic low-q depression, which cannot be interpreted as aggregate mass decrease in our data. In addition, the reinforcement effect of these silica structures in the SBR-matrix is characterized with oscillatory shear and described with a model based on the same aggregate compacity. Finally, our results show that it is possible to analyze the complex structure of interacting aggregates in nanocomposites of industrial origin in a self-consistent and quantitative manner.