Spectroelectrochemistry of Electroactive Polymer Composite Materials

In this review, we have summarized the main advantages of the method of spectroelectrochemistry as applied to recent studies on electrosynthesis and redox processes of electroactive polymer composite materials, which have found wide application in designing organic optoelectronic devices, batteries and sensors. These polymer composites include electroactive polymer complexes with large unmovable dopant anions such as polymer electrolytes, organic dyes, cyclodextrins, poly(β-hydroxyethers), as well as polymer-inorganic nanocomposites. The spectroelectrochemical methods reviewed include in situ electron absorption, Raman, infrared and electron spin resonance spectroscopies.

Poly(N-methylaniline) vs. polyaniline: An extended pH range of polaron stability as revealed by Raman spectroelectrochemistry

A comparative study of polyaniline (PANI) and poly(N-methylaniline) (PNMA) has been performed by means of Raman spectroelectrochemical technique at 633 nm and 785 nm laser line excitations. The excitation wavelengths used fall into a resonance with the blue colored semi- and full-oxidized forms of these conducting polymers. The dependence of Raman features on electrode potential and solution acidity was studied, and relative content of polaronic and bipolaronic states was evaluated. In an acidic solution, the semioxidized emeraldine form of either PANI or PNMA exists in equilibrium between their polaronic and bipolaronic states. In a neutral or even slightly alkaline solution, this equilibrium for PANI shifts to bipolaron state, resulting in loss of its conductance. For PNMA, however, the relative content of polaron state appears high enough even in pH-neutral soulions, thus determining a higher conductivity of PNMA in pH-neutral environment as compared to that of PANI. A mechanistic interpretation for this, based on differences in the chemical structures of these polymers, is also presented.