The polymerization of aniline at a solution–gelatin gel interface

Gelatin gel swollen with the solution of aniline hydrochloride was exposed to a solution of ammonium peroxydisulfate. The reactants met at the gel interface, and the redox reaction between them produced a polyaniline (PANI) interlayer, a PANI membrane, at first. The electrons abstracted from the aniline molecules in the gel during the oxidation are transferred through a conducting PANI membrane to oxidant molecules in the external solution. The reaction between aniline and peroxydisulfate thus takes place without the need for the reactant molecules to physically meet. PANI, therefore, grows from the interface into the gelatin gel. When the loci of reactants are reversed, i.e. the oxidant is inside the gelatin gel and aniline hydrochloride in the surrounding solution, PANI grows from the gel interface into the aniline solution but some PANI is produced inside the gelatin gel, too. Composite PANI–gelatin gels were separated and gelatin was removed from them by acid hydrolysis. The resulting PANI had a granular morphology and a conductivity of the order of units S cm−1, slightly lower compared with PANI prepared in a common way by mixing the solutions of reactants. The differences in the details of molecular structure are discussed on the basis of FTIR spectra.