Local dynamic mechanical properties in model free-standing polymer thin films.
Local dynamic mechanical properties in model free-standing polymer thin films.
复制标题
模型独立式聚合物薄膜的局部动态机械性能。
DOI：
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发表时间：
2005
影响因子：
4.4
通讯作者：
J. D. de Pablo
中科院分区：
文献类型：
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作者：
K. Yoshimoto;Tushar S. Jain;P. Nealey;J. D. de Pablo
利用一个粗晶聚合物模型的高频正弦振动，计算了自支撑聚合物薄膜的局部动态力学性能。研究了储能模数G(‘)和损耗模数G(“)随垂直于自由表面位置的变化.发现在玻璃薄膜的自由表面附近出现了机械软化层，并且随着温度接近玻璃化转变温度T(G)，它们的厚度与整个薄膜厚度相当.结果是，玻璃薄膜的整体硬度随着薄膜厚度的增加而减小.还发现在薄膜的主体部分T(G)处有两个区域共存；在薄膜的中间有一个类似熔体的区域(G(’)G(”)).我们关于DMPs在自支撑聚合物薄膜中存在异质分布的发现为最近对玻璃化聚合物薄膜的力学性能的实验测量提供了见解。
High-frequency sinusoidal oscillations of a coarse-grained polymer model are used to calculate the local dynamic mechanical properties (DMPs) of free-standing polymer thin films. The storage modulus G(') and loss modulus G(") are examined as a function of position normal to the free surfaces. It is found that mechanically soft layers arise near the free surfaces of glassy thin films, and that their thickness becomes comparable to the entire film thickness as the temperature approaches the glass transition T(g). As a result, the overall stiffness of glassy thin films decreases with film thickness. It is also shown that two regions coexist in thin films just at the bulk T(g); a melt-like region (G(')G(")) in the middle of the film. Our findings on the existence of a heterogeneous distribution of DMPs in free-standing polymer thin films provide insights into recent experimental measurements of the mechanical properties of glassy polymer thin films.