Strain-induced dielectric anisotropy of polymers for rapid and sensitive monitoring of the small elastic strain

Stretching is the most important way of forming polymer films, and the mechanism of stretch-induced structural evolution is a long-standing fundamental issue in the stretching process of polymer films. Current methods are limited in sampling frequency or transparent materials and difficult to in situ measure the molecular chain structure evolution. In this study, we proposed a new principle for measuring the stretching process of polymer materials based on dielectric anisotropy. Firstly, the strain-dielectric anisotropy linear relation during small elastic deformation was found, and an extremely small strain (∼0.1%) can be measured with a high sampling frequency (∼8.3 Hz). Then, the molecular chain orientation-induced dielectric anisotropy for the underlying mechanism was confirmed by molecular dynamics simulations and in situ polarized Raman spectroscopy experiments. The proposed method was successfully applied in measuring tube compliance and dynamic health monitoring by measuring small elastic strain accurately, exhibiting the potential for wide applications.