Structural and Mechanical Dynamics of Polymer Membranes Across Multilength Scales.

Understanding the mechanical and structural evolution of polymer membranes under heat and strain is important for many applications. Conventional techniques, such as dynamic mechanical analysis provide bulk mechanical information but lack the spatial resolution to capture localized variations. Similarly, X-ray diffraction spectroscopy effectively probes long-range order but has limited capability in analyzing amorphous polymer structures. Herein, we reveal the importance of mechanical and structural analyses across multilength scales. We unveiled the opposite trend in surface-to-bulk mechanical behavior of polymer membranes, necessitating the investigation of both regions to fully capture their functional behavior. We mapped nanoscale mechanical inhomogeneities across membrane surfaces with in situ atomic force microscopy quantitative nanomechanics. Further, we uncovered structural irregularities across both short- and long-range order using in situ small- and wide-angle scattering spectroscopies. We investigate key structural parameters and describe density variations in amorphous domains. Molecular dynamics simulations corroborate with the observed structural and mechanical properties at the molecular level. Our multilength-scale characterization strategy provides a robust framework for elucidating structure-property relationships from macroscopic to molecular levels. The approach is generalizable to other systems such as films, fibers, and two-dimensional materials, enabling new insights into their dynamic properties.