Tkach V. The critical phenomena in the electrochemical synthesis of conducting polymers

The thesis is dedicated to the theoretical investigation of the critical phenomena in the processes of the electrochemical synthesis of conducting polymers. It is realized by analysis of corresponding mathematical models by using of linear stabilidy theory and bifurcation analysis. Basing on the results of the models of the processes of electropolymerization in different modes, it was shown that in the neutral-mode electropolymerization over an inert anode the steady-state stability is maintained by one of the next factors, like, the prevaluation of the desorption over the adsorption, or the increasement of the its unit velocity. The oscillatory behavior in such systems is caused by surface and electrochemical factors. For the case of the electropolymerization of acydophobic monomer in strong acid media, the third factor, responsible for the oscillatory behavior, besides of two mentioned, will be the autocatalytic protons? formation. The same factors are responsible for the oscillatory behavior in galvanostatic electropolymerization. The factor of the passivity of the formed polymer is also responsible for the oscillatory behavior in the case of the constant voltage mode. It?s shown that, for the case of the potentiostatic overoxidation, the monotonic instability isn?t possible. The system may be only in stable steady-state and in oscillatory mode, that may be possible only in the case of the autocatalytic protons formation. The same case remains for the galvanostatic polymerization process. The monotonic instability may be realized in the case of the equality of the influences of overoxidation and reaction of the overoxidized polymer with protons. The oscillatory behavior in the system of polythiophene paradox is caused by the action of the surface, electrochemical and autocatalytic factors. In the case of the work of the sensors and biosensors based on conducting polymers, the oscillatory behavior may be caused by electrochemical, autocatalytic (if any) and passivation (in constant-voltage mode) factors. The pH decreasing influences the work of the sensors negatively, because it makes the steady-state less stable.