XPS analysis of polymer brush coatings.

X-ray photoelectron spectroscopy (XPS) is a powerful surface-sensitive technique widely used for the chemical characterization of thin films and interfaces. XPS detects the outermost ∼10 nm of organic films, making it useful for studying the surface of polymer-brush coatings. Despite the widespread use of XPS for polymer brushes, data interpretation and reporting practices often remain inconsistent, particularly for chemically complex or beam-sensitive systems. This tutorial review provides a practical overview of XPS analysis of polymer-brush coatings, with emphasis on experimental considerations, spectral interpretation, and common pitfalls. Key aspects of sample preparation are discussed, including contamination control, charge compensation, and strategies to minimize beam-induced degradation in radiation-sensitive polymers. The interpretation of survey spectra is examined with a focus on elemental quantification, background selection, and complications arising from spin-orbit splitting. Strategies for estimating polymer-brush thickness from substrate signal attenuation are outlined together with the assumptions and limitations inherent to attenuation-based analysis. Detailed guidance is provided for high-resolution C 1s analysis, including background modeling, chemically consistent peak fitting, and assignment of common carbon environments, while highlighting common overfitting artifacts. The complementary role of density functional theory (DFT) calculations in supporting chemically meaningful peak assignment and validating spectral interpretation is also discussed. By combining practical recommendations with critical discussion of common sources of error, this tutorial aims to support more reliable and reproducible XPS characterization of polymer brush coatings.