In-situ prepared polyaniline–silver composites: Single- and two-step strategies

Conducting polymer–metal composites, such as polyaniline–silver, can efficiently be prepared by two ways: (1) by the oxidation of aniline with silver ions or (2) by the reduction of silver ions with polyaniline. Both approaches yield the composites with limited conductivity. In order to increase the content of silver, and thus increase the conductivity, two strategies are proposed: (1) an increase of oxidant-to-aniline mole ratio in the oxidation of aniline with silver nitrate above stoichiometric value in a single step, and thus reduce excess silver ions to silver metal with produced polyaniline, or (2) in two steps, by preparing polyaniline–silver composite at first and then using polyaniline for the reduction of silver ions. The second approach yields the composites of higher conductivity of the order 100 S cm−1. The role of aniline oligomers and interfacial barriers is discussed on the basis of UV–vis and FTIR spectra, and on morphology assessment. The changes in conductivity of composites after deprotonation and reprotonation of polyaniline part are also reported. Surprisingly, the conversion of conducting polyaniline salt to a non-conducting polyaniline base may be associated with an increase of composite conductivity.