Mochizuki Yuki, Imai Hiroaki, Oaki Yuya
Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
ACS Appl Mater Interfaces. 2023 Oct 18;15(41):48725-48735. doi: 10.1021/acsami.3c12043. Epub 2023 Oct 5.
When mechanical stresses, such as tensile, compressive, and frictional stresses, are applied to objects by various motions, they are accumulated in materials. Conventional mechanoresponsive materials and sensors detect one-time applied stress. However, the accumulated stresses are not visualized or measured in previous works. The present study demonstrated imaging and sensing of not only one-time but also accumulated tensile, compressive, and frictional stresses. Polyurethane (PU) film was combined with 2D layered polydiacetylene (PDA), a stimuli-responsive color-changing polymer. PDA generally exhibits no color changes with the application of tensile and compression stresses because the molecular motion leading to the color change is not induced by such mechanical stresses. Here the versatile mechanoresponsiveness was achieved using a block copolymer guest partially intercalated in the layered PDA. As the interlayer and outerlayer segments interact with PDA and PU, respectively, the applied stresses to the film are transferred from PU to PDA via the block copolymer guest. The color changes of the film imaged and quantified the accumulated work depending on the number and strength of the applied multiple stresses such as tensile, compressive, and frictional stresses. The design strategy of materials and methodology of sensing can be applied to the development of new sensors for accumulated mechanical stresses in a wide range of length and strength scales.
当通过各种运动对物体施加拉伸、压缩和摩擦等机械应力时，这些应力会在材料中积累。传统的机械响应材料和传感器只能检测一次性施加的应力。然而，在以往的研究中，累积应力并未得到可视化或测量。本研究展示了对一次性和累积的拉伸、压缩及摩擦应力的成像和传感。聚氨酯（PU）薄膜与二维层状聚二乙炔（PDA）相结合，PDA是一种对刺激有响应的变色聚合物。通常，由于这种机械应力不会引发导致颜色变化的分子运动，所以在施加拉伸和压缩应力时，PDA一般不会发生颜色变化。在此，通过部分插层在层状PDA中的嵌段共聚物客体实现了多功能机械响应性。由于层间和外层链段分别与PDA和PU相互作用，施加到薄膜上的应力通过嵌段共聚物客体从PU传递到PDA。薄膜的颜色变化根据施加的多种应力（如拉伸、压缩和摩擦应力）的数量和强度对累积功进行成像和量化。材料的设计策略和传感方法可应用于开发适用于各种长度和强度尺度下累积机械应力的新型传感器。
