Laterally Controlled Template Electrodeposition of Polyaniline

Abstract

Polyaniline (PANi) was electrodeposited in gold‐coated nanoporous alumina membranes (NAMs) by anodic polymerization of aniline. PANi deposition was followed by cathodic deposition of Ag or Cu, to form a layer of PANi–metal segmented nanowires in the NAM. The compact PANi nanowires fill the entire pore volume, providing a sharp transition from the polymer to the metal segment. The deposited metal layer enables SEM visualization of the PANi nanowire length in the membrane. Deposition of Cu on PANi nanowires occurs at potentials where the PANi is in its reduced leucoemeraldine state, with no evidence for penetration of the metal into the polymer matrix. The mechanism of metal ion reduction on the nonconducting polymer wires is not yet clear. Free‐standing segmented PANi–Ag and PANi–Cu nanowires obtained by membrane dissolution show a sharp heterojunction between the polymer and metal phases and are mechanically stable. Aniline electropolymerization in the insulating NAM under a lateral potential gradient generated a thickness gradient of the PANi deposit, revealed by subsequent Cu deposition. The potential‐dependent length of the PANi nanowires follows the PANi conductivity pattern, reaching a maximum in the region of stability of the conducting emeraldine phase. The results demonstrate the possibility of obtaining nonlinear graded materials using electrochemical systems showing a complex current–voltage behavior.

Electrochemically Generated Gradients

“…Hybrid polymer/metal NWs with a gradient in the length of the polymer were also fabricated. An in‐plane potential gradient was used for the electrodeposition of polyaniline, which was followed by the electrodeposition of Ag or Cu 51…”

Elektrochemisch erzeugte Gradienten

“…Auch Polymer‐Metall‐Hybrid‐NWs mit Gradient in der Polymerlänge wurden angefertigt. Zuerst wurde an einem In‐plane‐Potentialgradient Polyanilin elektrochemisch abgeschieden, danach Ag oder Cu 51…”

Surface-Bound Gradients for Studies of Soft Materials Behavior

“…Early efforts involved the utilization of the so-called knife-edge coating technique (62)(63)(64) to form polymer layers with a gradual variation of composition and/or thickness. Other procedures included plasma polymerization on surfaces (65-68), electrodeposition (69), and chemical vapor deposition (70). A popular class of methodologies utilizes chemical grafting of polymer chains to the substrate by employing either grafting-onto or grafting-from technologies (71).…”