Conductive, Monodisperse Polyaniline Nanofibers of Controlled Length Using Well‐Defined Cylindrical Block Copolymer Micelles as Templates

Abstract

Stable colloidal dispersions of polyaniline (PAni) nanofibers with controlled lengths from about 200 nm-1.1 μm and narrow length distributions (Lw/Ln < 1.04; Lw = weight average micelle length, Ln = number average micelle length) were prepared through the template-directed synthesis of PAni using monodisperse, solution-self-assembled, cylindrical, block copolymer micelles as nanoscale templates. These micelles were prepared through a crystallization-driven living self-assembly method from a poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine) block copolymer (PFS25 -b-P2VP425). This material was initially self-assembled in iPrOH to form cylindrical micelles with a crystalline PFS core and a P2VP corona and lengths of up to several micrometers. Sonication of this sample then yielded short cylinders with average lengths of 90 nm and a broad length distribution (Lw/Ln = 1.32). Cylindrical micelles of PFS25 -b-P2VP425 with controlled lengths and narrow length distributions (Lw/Ln < 1.04) were subsequently prepared using thermal treatment at specific temperatures between 83.5 and 92.0 °C using a 1D self-seeding process. These samples were then employed in the template-directed synthesis of PAni nanofibers through a two-step procedure, where the micellar template was initially stabilised by deposition of an oligoaniline coating followed by addition of a polymeric acid dopant, resulting in PAni nanofibers in the emeraldine salt (ES) state. The ES-PAni nanofibers were shown to be conductive by scanning conductance microscopy, whereas the precursor PFS25-b-P2VP425 micelle templates were found to be dielectric in character.