Pokhrel Geeta, Jo Hyungyung, Christ Nicholas M, Son Hyeyoung, Howarter John A, Davis Chelsea S
School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Environmental and Ecological Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Macromol Rapid Commun. 2025 Feb;46(4):e2400736. doi: 10.1002/marc.202400736. Epub 2024 Dec 31.
Examining the mechanical properties of polymer thin films is crucial for high-performance applications such as displays, coatings, sensors, and thermal management. It is important to design thin film microstructures that excel in high-demand situations without compromising mechanical integrity. Here, a polymer blend of polystyrene (PS) and polyisoprene (PI) is used as a model to explore microscale deformation behavior under uniaxial mechanical testing. Six thin film compositions ranging from pure PS to a 4.5:5.5 ratio of PS to PI are fabricated. The thin films are deformed under compression, tension, and cyclic loadings, while monitoring the behavior utilizing a micromechanical stage and optical microscopy. To calculate the plane strain modulus, a strain-induced elastic buckling instability technique is employed. The results show that as the PI concentration increases, the plane strain modulus of the films decreases while the fracture strain increases. For the 4.5:5.5 ratio of PS to PI with a continuous rubbery PI phase, the thin films show major recoverable mechanical performance. This behavior is attributed to the mechanical strength of glassy PS combined with the strain energy absorption capability of rubbery PI, enabling elastic recovery. These fundamental observations provide valuable insights for designing mechanically resilient thin films for coatings and flexible devices.
研究聚合物薄膜的机械性能对于显示器、涂料、传感器和热管理等高性能应用至关重要。设计在高要求情况下表现出色且不损害机械完整性的薄膜微观结构非常重要。在此，以聚苯乙烯（PS）和聚异戊二烯（PI）的聚合物共混物为模型，探索单轴机械测试下的微观变形行为。制备了六种薄膜组合物，从纯PS到PS与PI比例为4.5:5.5。薄膜在压缩、拉伸和循环载荷下变形，同时利用微机械平台和光学显微镜监测其行为。为了计算平面应变模量，采用了应变诱导弹性屈曲失稳技术。结果表明，随着PI浓度的增加，薄膜的平面应变模量降低而断裂应变增加。对于PS与PI比例为4.5:5.5且具有连续橡胶态PI相的情况，薄膜表现出主要的可恢复机械性能。这种行为归因于玻璃态PS的机械强度与橡胶态PI的应变能吸收能力相结合，从而实现弹性恢复。这些基本观察结果为设计用于涂料和柔性器件的机械弹性薄膜提供了有价值的见解。
