Self-assembled anionic micellar template for polypyrrole, polyaniline, and their random copolymer nanomaterials

We report an anionic surfactant approach for size and shape control in polyaniline, polypyrrole, and their polyaniline-co-polypyrrole random copolymer nanomaterials. A renewable resource azobenzenesulfonic acid anionic surfactant was developed for template-assisted synthesis of these classes of nanomaterials. The surfactant exists as 4.3 nm micelle in water and self-organizes with pyrrole to produce spherical aggregates. The sizes of the spherical aggregates were controlled by water dilution and subsequent oxidation of these templates, produced polypyrrole nanospheres of 0.5 μM to 50 nm dimensions. The anionic surfactant interacts differently with aniline and forms cylindrical aggregates, which exclusively produce nanofibers of ~180 nm in diameter with length up to 3-5 μM. The template selectivity of surfactant toward aniline and pyrrole was used to tune the nanostructure of the aniline-pyrrole random copolymers from nanofiber-to-nanorod-to-nanospheres. Dynamic light scattering technique and electron microscopes were used to study the mechanistic aspects of the template-assisted polymerization. The four probe conductivity of the copolymers showed a nonlinear trend and the conductivity passes through minimum at 60-80% of pyrrole in the feed. The amphiphilic dopant effectively penetrates into the crystal lattices of the polymer chain and induces high solid state ordering in the homopolymer nanomaterials.