Tomoshige Naoya, Goto Shota, Mizuno Hideyuki, Mori Tatsuya, Kim Kang, Matubayasi Nobuyuki
Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.
J Phys Condens Matter. 2021 May 28;33(27). doi: 10.1088/1361-648X/abfd51.
Amorphous materials exhibit peculiar mechanical and vibrational properties, including non-affine elastic responses and excess vibrational states, i.e., the so-called boson peak (BP). For polymer glasses, these properties are considered to be affected by the bending rigidity of the constituent polymer chains. In our recent work [Tomoshige,2019,19514], we have revealed simple relationships between the variations of vibrational properties and the global elastic properties: the response of the BP scales only with that of the global shear modulus. This observation suggests that the spatial heterogeneity of the local shear modulus distribution is insensitive to changes in the bending rigidity. Here, we demonstrate the insensitivity of elastic heterogeneity by directly measuring the local shear modulus distribution. We also study transverse sound wave propagation, which is also shown to scale only with the global shear modulus. Through these analyses, we conclude that the bending rigidity does not alter the spatial heterogeneity of the local shear modulus distribution, which yields vibrational and acoustic properties that are controlled solely by the global shear modulus of a polymer glass.
非晶态材料表现出独特的力学和振动特性，包括非仿射弹性响应和过量振动态，即所谓的玻色子峰（BP）。对于聚合物玻璃，这些特性被认为受构成聚合物链的弯曲刚度影响。在我们最近的工作[友重，2019，19514]中，我们揭示了振动特性变化与整体弹性特性之间的简单关系：玻色子峰的响应仅与整体剪切模量的响应成比例。这一观察结果表明，局部剪切模量分布的空间不均匀性对弯曲刚度的变化不敏感。在此，我们通过直接测量局部剪切模量分布来证明弹性不均匀性的不敏感性。我们还研究了横向声波传播，结果表明其也仅与整体剪切模量成比例。通过这些分析，我们得出结论，弯曲刚度不会改变局部剪切模量分布的空间不均匀性，这使得聚合物玻璃的振动和声学特性仅由其整体剪切模量控制。
