Conducting poly(anilineboronic acid) nanostructures: Controlled synthesis and characterization

Self-doped poly(anilineboronic acid) (PABA) nanostructures have been prepared by chemical polymerization in an aqueous acid solution and aliphatic alcohols. In aliphatic alcohols, PABA is soluble under the polymerization conditions. According to B-11 NMR studies, the formation of anionic tetrahedral boronate ester in aliphatic alcohols in the presence of fluoride forms the basis of self-doped, soluble PABA. Transmission electron microscope images show the formation of nanostructures with different shapes and forms in different solvents after precipitation of the polymer as a result of ion exchange in the presence of 0.5 m HCl The spectroscopic and cyclic voltammetric results confirm the formation of conducting PABA nanostructures in high yield. The conductivity of PABA thin films made from the nanostructures prepared in aqueous acid, methanol, ethanol and I-propanol is approximately 15 and 3.0, 2.1 and 1.9 S . cm(-1), respectively. The conducting PABA nanostructures are processable since they are easily re-dispersed in the various solvents up to approximately 5 mg . mL(-1). UV-vis kinetic measurements, XPS and B-11 NMR results suggest that the formation of various nanostructures is influenced by the polymerization rate, the degree of self-doping versus external doping, and the polarity of the solvents used. The PABA nanostructured films produced from these structures exhibit enhanced redox stability in a wider potential window in non-aqueous media compared to polyaniline due to formation of six-member heterocyclic complexes Containing a boron- imine dative bond resulting in a self-doped self-cross- linked polymer. The degree of cross-linking depends on the nature of nanostructures. In non-aqueous media, the self-doped, self-cross-linked PABA nanostructured films are much less susceptible to cathodic and anodic degradation at extreme potentials, overcoming a major limitation of more common conducting polymers.