On the induction period in polyacrylamide electrogeneration from DMF solutions

Abstract

The influence of the initial pH on the acrylamide electropolymerization in solution was determined by gravimetric studies. The empirical kinetics were found to be dependent on [H +] 0.25. The electrochemical polymerization rates were obtained by substraction of the overall process and the chemical polymerization rates. The simultaneous presence of monomer oxidation, nitrate discharge and residual water oxidation on the electrode explains the experimental results. A lower initial pH hinders water oxidation, favouring monomer oxidation and electrolyte discharge: the induction time decreases and the polymerization rate increases. The increase of the temperature favours monomer oxidation and electrolyte discharge at the expense of water oxidation: the induction time decreases. All the variables able to produce a decrease in water discharge favour a fast production of a polyacrylamide film on the electrode during the induction time. The presence of this film was not enough to avoid the induction time and the anolyte acidification was needed to hinder water discharge. The acidification was produced by proton liberation during the induction time.