# Structural and Mechanical Dynamics of Polymer Membranes Across Multilength Scales

## TL;DR

This paper shows how polymer membranes behave differently on the surface versus inside, using advanced techniques to study their structure and mechanics at multiple scales.

## Contribution

The study introduces a multilength-scale characterization strategy combining in situ SAXS-WAXS and AFM-based nanomechanics to reveal surface-to-bulk mechanical contrasts in polymer membranes.

## Key findings

- Surface-to-bulk mechanical behavior of polymer membranes shows opposite trends.
- Nanoscale mechanical inhomogeneities were mapped using in situ atomic force microscopy.
- Structural irregularities across short- and long-range order were uncovered using scattering spectroscopies.

## Abstract

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.

Distinct surface‐to‐bulk mechanical contrasts in polymer membranes were unveiled, highlighting the need to probe both regions to fully capture their functional behavior. By integrating in situ SAXS–WAXS with AFM‐based nanomechanics, nanodomain‐level heterogeneity and real‐time structural transformations induced by thermal and mechanical stimuli were revealed, offering a deeper understanding on the structural and mechanical behavior of the membranes.