Polymer-Solvent Interactions from the Electrochemically Stimulated Conformational Relaxation Model

POLYMER-SOLVENT INTERACTIONS FROM THE ELECTROCHEMICALLY STIMULATED CONFORMATIONAL RELAXATION MODEL 

The influence of the solvent on the oxidation of film under conformational relaxation control is illustrated in Fig. 47, which shows chronoamperograms obtained by steps from -2000 to 300 mV vs. SCE at room temperature (25°C) over 50 s in 0.1 M LiC104 solutions of different solvents acetonitrile, acetone, propylene carbonate, (PC), dimethyl sulfoxide (DMSO), and sulfolane. Films were reduced over 120 s in the corresponding background solution. Despite the large differences observed in the relative shape of the curves obtained in different solvents, shifts in the times for the current maxima (/max) are not important. This fact points to a low influence of the solvent on the rate at which confor- 

The electrochemical responses were quantified through both compaction and relaxation coefficients that represent the energy required to compact or relax 1 mol of polymeric segments. A series of experiments were performed in each solvent by potential steps from different cathodic potentials (-1600, -1800, -2000, -2200, and -2400 mV vs. SCE) with the same anodic potential, changing this potential for every series (-250, 

The ESCR model allows us to derive from both Eq. (51) and the above experimental results an expression for the interchain free volume (od) left inside the polymeric structure after polarization at a given cathodic overpotential rjc  

Here x is the polymer-solvent interaction parameter defined by Flory for polymeric swelling its value becomes more negative as the interaction between the solvent and the polymer increases. By comparing Eqs. (45) and (46), we arrive at 

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