Zhang Song, Koizumi Masato, Cao Zhiqiang, Mao Keyou S, Qian Zhiyuan, Galuska Luke A, Jin Lihua, Gu Xiaodan
School of Polymer Science and Engineering, Center for Optoelectronic Materials and Device, The University of Southern Mississippi, Hattiesburg, Mississippi 39406, United States.
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
ACS Polym Au. 2021 Jun 22;1(1):16-29. doi: 10.1021/acspolymersau.1c00005. eCollection 2021 Aug 11.
Understanding fracture mechanics of ultrathin polymeric films is crucial for modern technologies, including semiconductor and coating industries. However, up to now, the fracture behavior of sub-100 nm polymeric thin films is rarely explored due to challenges in handling samples and limited testing methods available. In this work, we report a new testing methodology that can not only visualize the evolution of the local stress distribution through wrinkling patterns and crack propagation during the deformation of ultrathin films but also directly measure their fracture energies. Using ultrathin polystyrene films as a model system, we both experimentally and computationally investigate the effect of the film thickness and molecular weight on their fracture behavior, both of which show a ductile-to-brittle transition. Furthermore, we demonstrate the broad applicability of this testing method in semicrystalline semiconducting polymers. We anticipate our methodology described here could provide new ways of studying the fracture behavior of ultrathin films under confinement.
理解超薄聚合物薄膜的断裂力学对于包括半导体和涂层行业在内的现代技术至关重要。然而，到目前为止，由于处理样品的挑战和可用测试方法的限制，100纳米以下聚合物薄膜的断裂行为很少被研究。在这项工作中，我们报告了一种新的测试方法，该方法不仅可以通过超薄薄膜变形过程中的起皱模式和裂纹扩展来可视化局部应力分布的演变，还可以直接测量它们的断裂能。使用超薄聚苯乙烯薄膜作为模型系统，我们通过实验和计算研究了薄膜厚度和分子量对其断裂行为的影响，两者均表现出韧性到脆性的转变。此外，我们证明了这种测试方法在半结晶半导体聚合物中的广泛适用性。我们预计这里描述的方法可以为研究受限条件下超薄薄膜的断裂行为提供新的途径。
