Plasma treatment of polyaniline films: Effect on the intrinsic oxidation states
- PDF / 141,011 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 18 Downloads / 153 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Plasma treatment of polyaniline films: Effect on the intrinsic oxidation states E. T. Kang Department of Chemical Engineering, National University of Singapore, Kent Ridge, Singapore 0511
K. Kato, Y. Uyama, and Y. Ikada Research Center for Biomedical Engineering, Kyoto University, 53 kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606, Japan (Received 3 November 1995; accepted 11 January 1996)
Surface modification of emeraldine (EM) and nigraniline (NA) base films by argon plasma treatment was investigated by x-ray photoelectron spectroscopy (XPS). Argon plasma treatment, followed by atmospheric exposure, results in the oxidation of some °° carbon atoms, first to C–O species and then to C ° ° O and COOH species for samples with extended plasma treatment time. Most important of all, Ar plasma treatment and the accompanied carbon oxidation readily cause a decrease in the intrinsic oxidation state ([°° N °° ]y[°° NH °° ] ratio) of the aniline polymers.
I. INTRODUCTION
II. EXPERIMENTAL
The synthesis and characterization of electroactive polymers have quickly become one of the most important research areas in polymer science in recent years.1 Among the electroactive polymers, the N-containing polymers, such as polyaniline (PAN) and polypyrrole (PPY), have been of particular interest. They have controllable electrical conductivity,2,3 environmental stability,4–6 and interesting redox properties associated with the chain heteroatoms.7,8 The aniline polymers also exhibit crystallinity9,10 and solutionor counterion-induced processability.11–16 The aniline polymers have the general formula [(°° B °° NH °° B °° NH °° )y (°° B °° N °° Q °° N °° )12y ]x , in which B and Q denote the C6 H4 rings in the benzenoid and quinonoid forms, respectively.2 Thus, the intrinsic oxidation states of the polymer can range from that of the fully oxidized pernigraniline (PNA, y 0) through that of the 75% oxidized nigraniline (NA, y 0.25), or that of the 50% oxidized emeraldine (EM, y 0.5) to that of the fully reduced leucoemeraldine (LM, y 1). The applications of PAN in electronic devices and as conductors, sensors, and active electrodes, etc. will require substantial surface modification and functionalization to improve, for example, the biocompatibility, hydrophilicity, and surface adhesive properties of the polymer. In this paper we report on the surface modification of PAN films by Ar plasma treatment, as plasma treatments have been widely used to modify the surface of conventional polymers.17–21 Using x-ray photoelectron spectroscopy as the main analytical tool, the effects of Ar plasma treatment on °° ° N °° ]y[°° NH °° ] ratios) the intrinsic redox states ([° of the polymer can be precisely tracked.
The chemical polymerization of aniline was carried out at about 5 ±C using ammonium persulfate as the oxidant, similar to the method reported in the literature,2 except that 1 M H2 SO4 was used instead of 1 M HCl. The polyaniline (PAN) salt was converted to the 50% intrinsically oxidized emera
Data Loading...
