Slow relaxation in conducting polymers

Potentiostatic oxidation of poly(3-methylthiophene): Influence of the prepolarization time at cathodic potentials on the kinetics

“…Fig. 4 shows that, whatever the cathodic potential of prepolarization two different slopes, two different c, are attained, corroborating similar previous results with polypyrrole [34] or polyaniline [33] films. For any prepolarization time lower than 25 s c ranges between 0.1 and 0.3, whatever the cathodic potential of prepolarization.…”

“…The presence of two different structures is being -6.000 Table 2 Charge consumed to pack one mol of polymeric segments by prepolarization at À1500 mV for different times (t w ) obtained from poly(3-methylthiophene) films, following the methodology described by Refs. [2][3][4] t w (s) ln t w (s) z c (C mol À1 ) deduced from different experimental procedures in the literature [34][35][36][37][38], the origin being controversial. Here we have obtained a magnitude characteristic of their energetic changes.…”

“…3) for rising prepolarization times, also known in the literature as waiting time (t w ), we should need to include this variable into the ESCR model. The rate coefficients were obtained from the current (oxidation rate) at the chronoamperometric maxima; and the oxidation time at the maximum is an empirical function, as was obtained by Nechtschein [24,34], of the prepolarization time, or waiting time (t w ):…”

Electrochemically induced ageing of polyaniline monitored by the changes in its voltammetric response

“…When they are brought to the reduced state and held at that condition, their ulterior electrochemical response change linearly with the logarithm of the time spent at that potential, t a [2]. This process has received several names in the electrochemical literature, such as ''slow relaxation'' [3][4][5][6][7][8][9], ''memory effect'' [10][11][12][13][14], and ''first cycle effect'' [15,16]. During the ageing there seems to be not only chemical processes, such as additional reduction of the material, but physical transformations as well.…”

Electrochemical Relaxation Study of Polythiophene as Conducting Polymer (Ii)

“…Since the discovery of polythiophene as an excellent conducting polymer, there have been intensive studies on its industrial applications such as electrodes of capacitors and photodiodes, antistatic coating, electrochromic windows, field effect transistors [3,[7][8][9][10][11], sensors and biosensors as well as for biomedical applications such as synthetic bones and artificial muscles [1,[11][12][13][14][15]. In cyclic voltammetry experiments the oxidation peak of the first run after the sample has been left for a wait-time in the neutral state, is narrower and shifted towards more positive potential than the peak observed in steady-state conditions [16]. This process is reported as the slow relaxation effect or memory effect by most of researchers.…”