Hengzhong Zhuang

Spectroscopic Characterization of Polymer Surfaces

The surface science of polymer materials has recently grown to a dynamic field, largely because of application in such areas as composite materials, wetting, coatings, adhesion, friction, and biocompatibility. The synthesis of new polymer materials, resulting in desired polymer-surface structures and composition, has become more sophisticated and is driving the development of new spectroscopic probes and continuing evolution of more established methods. A good example of how instrumentation development has led to better applications in polymer-surface science is to follow the growth of studies using x-ray photoelectron spectroscopy (XPS)—also called electron spectroscopy for chemical analysis (ESCA). ESCA is now routinely used to obtain surface composition of polymers, and to follow processing steps and degradation chemistry. Advances in instrumentation have driven many of these more sophisticated applications. Nevertheless, to improve the understanding of polymer-surface chemistry, more information is needed about surface structure with further sophistication, at a higher level of precision. For example, the knowledge of orientation and subsequent reactive availability of functional groups and of monomer ar rangement along a chain in copolymers and intrachain interactions is important. Macromolecular chain arrangement, termination, branching, and micromorphological information (i.e., domain size and distribution), molecular-weight distributions at or near the surface (in comparison with the average, bulk distribution), and higher degrees of spatial resolution in all three dimensions are all important in determining sophisticated surface structure-property relationships. To approach this level of structural and reactivity information at surfaces and interfaces, evolution of established methods and development of new methods must both be accomplished.