Book chapter
Ultrathin polyaniline films on metal surfaces: Growth, polymerization, and conductivity
Metallized Plastics 7, pp 293-306
2001
Abstract
Early applications of High Resolution Electron Energy Loss Spectroscopy (HREELS) for the study of ultrathin polymer films and polymer-metal interfaces provided important information on bonding and electronic structure through analysis of sequentially-measured vibrational and electronic excitation spectra in the near-surface region. However, detailed analyses of vibrational spectra were limited by energy resolution >40 cm−1 which made it difficult to separate close-lying vibrational modes. Recent developments in HREEL spectrometers has made it possible to achieve <8 cm−1 energy resolution, and along with the ability to excite both optically-active and optically-forbidden transitions, virtually all the vibrational modes of complex polymer ultrathin films can be distinguished. Then the analysis of surface functionalities and interfacial bonding proceeds by comparison with reference infrared, Raman, and uv-vis spectra of molecular analogs. In this paper, we present brief highlights in the development of HREELS for the study of polymer systems and discuss our recent studies of polyaniline ultrathin films deposited on metal surfaces. These studies have (1) identified substrate-dependent effects in initial bonding and growth of vapor-deposited polyaniline oligomers, (2) shown evidence for polymerization at the surface, (3) found relatively high local conductivity in protonated films after ex-situ doping, and (4) provided new insights in the conductivity mechanisms themselves. Finally, prospects and limitations of HREELS as applied to polymer systems are noted.
Early applications of High Resolution Electron Energy Loss Spectroscopy for the study of ultrathin polymer films and polymer-metal interfaces provided important information on bonding and electronic structure through analysis of sequentially-measured vibrational and electronic excitation spectra in the near-surface region. Thin film polymers are used in a host of applications ranging from protective coatings to insulating layers in microelectronics devices. Ultrathin films deposited on conducting substrates can usually conduct well so that charging effects are minimized. Vapor-deposited ultrathin poly aniline films grown on silver(110) and gold can be compared with those grown on copper(110). No oligomer-substrate losses are observed on the silver and gold surfaces suggesting that the amino groups react only weakly with these surfaces. Significantly, similar trends in the transfer of intensity of the CH out-of-plane modes from monosubstituted rings to paradisubstituted rings are observed indicating the occurrence of a polymerization reaction.
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Details
- Title
- Ultrathin polyaniline films on metal surfaces: Growth, polymerization, and conductivity
- Creators
- N.J. DiNardoJ.M. VohsY. WeiR. PlankK. Lee
- Contributors
- K.L. Mittal (Editor)
- Publication Details
- Metallized Plastics 7, pp 293-306
- Publisher
- CRC Press
- Edition
- 1
- Resource Type
- Book chapter
- Language
- English
- Academic Unit
- Physics
- Other Identifier
- 991021862370204721