Optimization of cryo‐XPS analyses for the study of thin films of a block copolymer (PS‐PEO)

The water‐induced surface reorganization of a thin film of a block copolymer [polystyrene‐b‐poly(ethylene oxide), PS‐PEO], was studied by cryogenic X‐ray photoelectron spectroscopy (cryo‐XPS). Experimental parameters were examined with a view to optimize the analysis. The absence of artifacts due to the low temperature of analysis was checked, and the influence of the procedure used for sample hydration before analysis was investigated. Adequate timing of the different steps of the analysis and temperature program was also established. With this optimized protocol, an important reorganization of the block copolymer was detected, showing more pronounced exposure of the PEO block at the outermost surface in hydrated compared to dry environment. As this type of polymer surface is prone to be used for biomedical applications, an accurate knowledge of the chemical composition of the outermost surface in aqueous environments is crucial. The development of this technique is therefore promising for related systems. Copyright © 2011 John Wiley & Sons, Ltd.

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