Poly(N-octadecylaniline) Synthesized at the Air-Water Interface: Aligned Nanofibers and Gold Nanocomposite Assembly via the Langmuir-Blodgett Technique

Abstract

Morphological and organizational control afforded by polymerization at the air-water interface, and the unique structural features of poly(N-alkylaniline)s are exploited in the fabrication of the polymer and polymer-nanoparticle composites in micro and nanofiber (ultrathin film) forms. While ammonium peroxodisulfate as the oxidizer provides poly(N-octadecylaniline) (PNOA), chloroauric acid leads to the nanocomposite, PNOA_Au. Experiments using relatively larger amounts of the monomer in a petri-dish produced PNOA and PNOA_Au microfibers that could be characterized using spectroscopy, microscopy and electrical conductivity measurement. Polymerization in monolayer Langmuir films under surface pressure control in a Langmuir-Blodgett (LB) trough, allowed the kinetics to be monitored, and ultrathin films of PNOA and PNOA_Au to be fabricated. The PNOA LB film shows nanofibers with twists, turns and helical segments, aligned parallel to the direction of monolayer compression; a computational model suggests a helical chain structure for PNOA formed at the interface. The polymer nanofibers are decorated with Au nanoparticles in the PNOA_Au film.