One of the most efficient methods for solid surface refinement is modification with thin organic polymer films. A very promising class of polymers for such surface modifications is the group of so called switchable polymers. These macromolecular compounds undergo very sharp reversible phase transitions in response to external stimuli such as light irradiation or temperature and enable so a simple way for rapid variations of surface properties, for example wettability. Different non-electrochemical methods have already been used in investigating switching phenomena of thermoresponsive polymers on solid surfaces. In this study it is shown how the structural changes in the polymer film on gold electrodes can be followed by electrochemical means.

For this purpose a thermally switchable polymer (copolymer of 2-(2-methoxyethoxy)ethyl methacrylate, oligo(ethylene glycol) methacrylate and 3-(2-methyl-acryloylamino)-propyl-ammonium chloride) with a lower critical solution temperature (LCST) around 38 °C was prepared  and covalently bound to the surface of gold wire electrodes. Subsequently cyclic voltammetric and impedimetric measurements with so prepared working electrodes were realised in aqueous potassium ferro-/ferricyanide solutions at different temperatures. The results of these studies show successful immobilisation of the polymer on the surface of gold, since the interfacial impedance is clearly enlarged with the polymer film present on the surface (increased resistance and decreased capacitance). Furthermore, significant changes of the temperature dependence of the voltammetric peak current and the peak separation values at LCST clearly demonstrate the thermally induced phase transition on the gold surface. Thus, first results can be presented, showing the potential usefulness of electrochemical methods to follow structural polymer changes on surfaces.     

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