A New Method for Preparing Cross-Sections of Polymer Composite Membranes for TEM Characterization by Substrate Stripping and Double-Orientation Embedding.

Membrane technology plays a vital role in environmental protection, chemical industry, and pharmaceuticals, where understanding the "structure-property" relationship of composite membranes through transmission electron microscopy (TEM) is crucial. Conventional ultramicrotomy methods for preparing ultra-thin sections of polymer composite membranes often result in significant damage and non-uniform thickness due to interference from non-woven substrates. In this study, we developed an innovative substrate stripping and double-orientation embedding technique that overcomes these limitations. A special embedding device was designed to facilitate the preparation of polymeric membrane cross-sections for TEM analysis. The device incorporates dual functionality, enabling both non-woven substrate detachment and bidirectional alignment of functional membrane layers. TEM characterization showed that the ultra-thin sections of membrane cross-sections prepared using the improved method were damage-free (0% damage rate), had uniform thickness, and showed distinct structural clarity. This method addressed three major challenges: (i) substrate-induced section damage, (ii) orientation deviation, and (iii) interlayer separation. This advancement provides researchers with a reliable tool for accurate cross-sectional analysis of composite membranes, facilitating deeper insights into membrane microstructure-performance relationships.