Desorption of emulsifiers from polystyrene latices followed by spectroscopic techniques

The desorption of emulsifier from the particle surface of latices prepared by emulsion polymerisation has been followed by spectroscopic techniques: transmission IR, X‐ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS) ‐fast atom bombardment mass spectrometry (FAB‐MS). In IR spectra, the extra band at 1710 cm −1 due to carboxylic groups originating from the emulsifier is fortunately visible because it is located within a window of the polystyrene peaks. XPS is a valuable surface method of analysis (contrary to IR). Nevertheless, for the latices considered here, it is impossible to extract from the very intense carbon peak information concerning variation in the carboxyl groups, which amount to less than 1%. Another important method for surface analysis is static‐SIMS, which allows detection of elements and molecular species present in the first few layers with a detection limit which is less than 10 −4 %. FAB‐MS permits the detection of the parent ion of the emulsifier employed. Freeze‐dried powders of latices extensively purified with mixed‐bed ion‐exchange resins were studied for us using FAB‐MS at UMIST in Manchester (UK). A comparison is made of the results obtained with these three spectroscopic techniques.