2D electrochemical methods with line micro-electrodes were used to measure lateral mobilities of several TEMPO amphiphiles at the air/water interface.An amide derivative of TEMPO with a tetradecane chain is shown in Figure 1.Our electrochemical measurements and Brewster angle microscopy showed that these types of surfactants form Langmuir monolayers exhibiting unusually low liquid/gas critical temperatures.Specifically,C_(14)TEMPO has a critical point below ca.2 deg C.In the absence of a liquid/gas phase transition,which in the cases of other surfactants is nucleated at the line micro-electrodes and leads to the disappearance of electrochemical signal,we can investigate the dependence of the lateral diffusion constant of the TEMPO amphiphiles on the water surface at extremely low surface densities.Both 2D voltammetry and the time-of-flight measurements can be used.
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