Flexible hybrid film of polypyrrole incorporated chitosan as a biomimetic multistep electrochemical sensor of working temperature: a potentiodynamic study

A polypyrrole/hydrogel hybrid film composed of macromolecular electrochemical machines fabricated through an in situ chemical polymerization of pyrrole is considered here as a flexible model material of the intracellular matrix of ectothermic muscle cells which is aware of ambient thermal energy. The polypyrrole component imparts excellent electroactivity and good electronic conductivity for the hybrid film. The hybrid film can go through n consecutive fundamental conformational energetic states progressively and reversibly under electrochemical control and acts as a multi-step macromolecular motor. Under constant electrochemical stimulus (cyclic voltammetry), increasing available thermal energy promotes deeper conformational movements of the polymeric chains due to the cooperative actuation of the constitutive electrochemical machines leading to the exchange of greater amounts of counterions and solvent for charge compensation and osmotic balance. The closed coulovoltammetric responses of the hybrid film guarantee the reversible nature of the polypyrrole redox reactions and reveal the absence of simultaneous irreversible reactions taking place in the studied potential window. At any reaction time, the extension of the reaction defined by the coulovoltammetric charge varies as a semilogarithmic function of the inverse of the temperature and acts as a self-sensor of reaction thermal conditions (reaction self-awareness). The results offer the potential for biomimetic sensing motors (intelligent devices) based on a polypyrrole/chitosan hybrid film imitating biological functions in which the driving and sensing signals can be read at any time during the reaction, through the same two connecting wires.