Accelerating SAXS Data Interpretation: A Comparative Assessment of Backbone-Dependent Morphology in Radiation-Grafted Anion-Exchange Membranes

Abstract

Anion exchange membranes (AEMs) are key components in electrochemical energy devices, where nanoscale morphology governs water and ionic transport and overall performance. In the growing interest toward radiation-grafted AEMs, the influence of polymer backbones on properties remains insufficiently explored. Here, we investigate how differences in backbone chemistry between ethylene tetrafluoroethylene (ETFE) and low-density polyethylene (LDPE) affect the AEMs bearing identical functional groups. Small-angle X-ray scattering (SAXS) is combined with ex situ characterization to provide an overview of bulk properties. LDPE-based membranes show ∼30 percentage points higher water uptake and swelling compared to ETFE films, which is consistent with the typically reported crystallinity for LDPE relative to ETFE and the correspondingly greater chain mobility of its matrix. The d-spacing values extracted from SAXS profiles (22−35 nm) do not always mirror bulk hydration behavior: higher degrees of functionalization of LDPE membranes show greater swelling yet reduced spacing, demonstrating that bulk and nanoscale structural responses are decoupled. Additionally, to reduce the barrier to adopting SAXS in the membrane community, we developed TRAMA. This Jupyter Notebook-based platform guides researchers through the data analysis workflow without prior expertise. This work highlights the critical role of the polymer backbone in determining AEM morphology and the value of SAXS as a characterization tool, providing an accessible means of processing scattering data.