PREFACE
Downloaded by 80.82.77.83 on December 27, 2017 | http://pubs.acs.org Publication Date: August 13, 1981 | doi: 10.1021/bk-1981-0162.pr001
T
he last decade witnessed a dramatic growth in the use of energetic beam techniques to elucidate the electronic structures of atoms and molecules. Photon, electron, and ion spectroscopies applied to solids gave birth to a new level of surface sensitivity for studies of chemical structure and bonding. The time was right to provide a benchmark for the state of current knowledge and future possibilities in the field. Thefirstobjective of the symposium upon which this book is based was to focus attention on the experimental and theoretical techniques currently being used to describe anion and cation states in large molecules and polymeric solids, with special emphasis being placed on the consequences to electronic structure incurred upon condensation from the gaseous into the solid state. It is, therefore, appropriate to begin with a review of the state of knowledge of anion states in large, isolated molecules as revealed by elastic and inelastic electron scattering, electron swarm, mass spectrographic, and ion-cyclotron resonance experiments. Insight into the effects of condensation on the nature of the lowest energy excitations that govern many of the chemical and physical properties of polymers is provided by results from high-energy electron energy loss spectroscopic studies on representative saturated polymers. Energy and charge transport in saturated and conjugated polymeric solids represent limiting cases in the applicability of the precepts of band theoretical descriptions of the electronic structure of solids. Discussions of the nature of intrinsic localized electronic states and their consequences to treatments of transport phenomena in such materials comprise an important section of these proceedings. Experimental studies of fundamental excitations in conjugated polymers are interpreted within the framework of current theoretical electronic structural calculations and physical structure characterizations. The instabilities peculiar to this class of materials that are responsible for their departure from metallic behavior are identified explicitly. Considering the valence levels, the synergistic effect of combining spectroscopic measurements with theoretical calculations is illustrated by two pairs of chapters: (1) ultraviolet photoemission and optical absorption data compared to a spectroscopically parameterized CNDO/S3 model, and (2) x-ray photoemission compared to ab initio and intermediate approximation MO calculations. ix Dwight et al.; Photon, Electron, and Ion Probes of Polymer Structure and Properties ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Downloaded by 80.82.77.83 on December 27, 2017 | http://pubs.acs.org Publication Date: August 13, 1981 | doi: 10.1021/bk-1981-0162.pr001
The firm theoretical understanding of the spectra of model molecules has been a major impetus to apply the techniques to complex, unknown solid-state structures of technological importance. Characterization of atomic composition, structure, and bonding in the surface and subsurface of "practical" specimens is thefirststep. Most studies interpret changes in the core-level spectra in terms of surface-chemical mechanisms involved in, for example, processing conditions, exposure to inert or reactive gas plasmas, chemical reactions, or aggressive service environments. Five chapters treat the basics as well as new developments in analytical methodology, emphasizing x-ray photoelectron spectroscopy for the identification of structure and bonding in polymer surfaces of increasing complexity. Each of the seven important levels of information available in the core-level data is illustrated in detail, with special emphasis upon: (1) Auger peak positions for chemical state identification; (2) angular and kinetic energy dependence of peak intensities for information on compositional variation with depth; and (3) enhanced resolution of functional groups with chemical derivatives. Explicitly developed are models of several theoretical multiphase distributions, with corresponding depth-profile results on thin-film plasma polymers, phase-separated block copolymers, and chemical reactions on fiber surfaces. Ion impact is treated from three points of view: as an analyticalfingerprinttool for polymer surface analysis via secondary ion mass spectroscopy, by forming unique thinfilmsby introducing monomers into the plasma, and as a technique to modify polymer surface chemistry. New experimental results on specific polymer material problems are presented in the last nine chapters. Several cases involve the study of polymers from commercial sources. The topics include: (1) surface chemistry as induced by (a) outdoor weathering, (b) chemical reactions, and (c) plasma exposure; (2) chemical bond formation at the polymer -metal interface; and (3)biomaterials characterization and relationship to blood compatibility. In summary, these proceedings provide a survey of the fundamentals and applications of photon, electron, and ion probes to polymers up to 1980. The contributors include many pioneers—from the basic studies performed with specialized, custom apparatus on small, gas-phase molecules to those utilizing standard commercial spectrometers to characterize practical polymer systems. We hope this work will contribute to the attainment of the ultimate objective of a unified description of the electronic structures and properties of polymeric solids. Acknowledgment is made to the donors of the Petroleum Research Fund (PRF #12290-SEO), administered by the American Chemical Society, for support in the way of travel expenses of the seven invited foreign speakers. Also Dr. Dwight gratefully acknowledges the support of x Dwight et al.; Photon, Electron, and Ion Probes of Polymer Structure and Properties ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
the Polymer Program of the Materials Division, National Science Foundation (Grant DMR 78-05429) and the Army Research Office (Grant DAAG29-80-K-0093) for partial support during the organization of the meeting and the preparation of the manuscript. Drs. Fabish and Thomas gratefully acknowledge support from Ashland Chemical Company and Xerox Webster Research Center, respectively. The editors are indebted to Kathy Fuller for typing and organizing the manuscripts in this book.
Downloaded by 80.82.77.83 on December 27, 2017 | http://pubs.acs.org Publication Date: August 13, 1981 | doi: 10.1021/bk-1981-0162.pr001
DAVID W. DWIGHT
Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 THOMAS J . FABISH
Ashland Chemical Company Columbus, Ohio 43216 H . RONALD THOMAS
Xerox Webster Research Center Rochester, New York 14644 March 27, 1981
xi Dwight et al.; Photon, Electron, and Ion Probes of Polymer Structure and Properties ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
