Polystyrene (30-40 nm) is produced using a cationic surfactant through emulsion polymerisation followed by centrifugation to remove any surfactant bound on the polystyrene. How to determine, at the end of centrifugation, that the surfactants have been removed? What are the possible tests?
Maybe it will be not possible to remove (fully) the cationic surfactant. If there is anionic initiator it will complex.
You maybe able to determine content of cationic surfactant by elemental analysis (N).
You mean drop weight method for surface tension? Could be done better with a tensiometer, however, surface active impurities would interfere. One could try surfactant sensitive electrodes. I thought of elemental analysis of the polymer particles not for solution. You would need to check whether you may be satisfied with detection limits.
Cationic surfactants can eaisly be removed by repeated washing with methanol and deionized water, peaks in FTIR spectra related to stretching mode of surfactant content can reveal the presence of surfactant easily, just compare it with parental polymer prepared without surfactant, it is difficult to remove anionic surfactants as compared to cationic. (proper washing will be sufficient).
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