In a previous article, we proposed a surface-controlled cooperatively rearranging region (SCC) model that mimics the segmental dynamics of supercooled liquids, including polymeric materials. By introducing surface/interface effects into the SCC model, the size-dependent dynamics of nanosized polymer materials such as ultrathin films can be predicted. In this study, the SCC model is extended to various nanomaterial geometries, i.e., filled fibers (cylinders), filled spheres, hollow fibers, hollow spheres, core/shell fibers, core/shell spheres, and thin films and spheres embedded in a substrate. We formulated temperature-dependent hole (free-volume) fraction profiles with respect to local position in the nanomaterials, and evaluated the weighted average of the hole fraction to consider the coupled dynamics in nanoconfined systems. The predicted glass transition temperature ( T g ) and fragility ( m ) of filled spheres of polystyrene coincide qualitatively with experimental observations reported in literature. The geometry dependence of the dynamics was also investigated, and it was revealed that T g (filled sphere) > T g (filled fiber) > T g (free-standing film) when compared at the same surface area to volume ratio, whereas for fragility, the opposite trend was found, i.e., m (free-standing film) > m (filled fiber) > m (filled sphere). A surface-controlled cooperatively rearranging region (SCC) model mimics the segmental dynamics of supercooled liquids. By introducing surface/interface effects into the SCC model, the size-dependent dynamics of nanosized polymer materials with various geometries were predicted. The calculated glass transition temperature ( T g ) and fragility for filled spheres of polystyrene coincided qualitatively with experimental observations. The results also showed that T g (filled sphere) > T g (filled fiber) > T g (free-standing film) when compared at the same surface area to volume ratio, whereas for fragility, the opposite trend was found.

中文翻译：

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从表面控制模型预测的纳米聚合物纤维和球体的玻璃化转变和脆性

在前一篇文章中，我们提出了一种表面控制的协同重排区域 (SCC) 模型，该模型模拟了过冷液体（包括聚合物材料）的分段动力学。通过将表面/界面效应引入 SCC 模型，可以预测纳米聚合物材料（如超薄膜）的尺寸相关动力学。在这项研究中，SCC 模型扩展到各种纳米材料几何形状，即填充纤维（圆柱体）、填充球体、中空纤维、空心球体、核/壳纤维、核/壳球体以及嵌入基板中的薄膜和球体. 我们根据纳米材料中的局部位置制定了与温度相关的孔（自由体积）分数分布，并评估了孔分数的加权平均值，以考虑纳米限制系统中的耦合动力学。聚苯乙烯填充球体的预测玻璃化转变温度 (Tg) 和脆性 (m) 与文献中报道的实验观察定性一致。还研究了动力学的几何相关性，结果表明，在相同的表面积与体积比下，T g（填充球）> T g（填充纤维）> T g（自支撑膜），而对于脆性，发现了相反的趋势，即 m（自支撑薄膜）> m（填充纤维）> m（填充球体）。表面控制的协同重排区域 (SCC) 模型模拟了过冷液体的分段动力学。通过将表面/界面效应引入 SCC 模型，预测了具有各种几何形状的纳米聚合物材料的尺寸相关动力学。计算出的聚苯乙烯填充球体的玻璃化转变温度 (Tg) 和脆性与实验观察结果一致。结果还表明，当在相同的表面积与体积比下进行比较时，Tg（填充球体）>Tg（填充纤维）>Tg（自支撑膜），而对于脆性，则发现相反的趋势。