In this chapter I have briefly touched upon many, but certainly not all, of the historical developments and current issues concerning conducting polymer structure and the associated structural phase behavior. Clearly the level of knowledge is most advanced for conducting polymer hosts having extensive crystallinity and high-symmetry structures. Unfortunately very few model host systems fulfill this criteria. Still, in the less ordered materials, the most general features of the microscopic structure are reasonably well understood.
The minute details of the local intramolecular structure, especially in terms of the side chain and main chain orientational ordering, remain poorly defined. By their very nature conducting polymers exhibit an intimate coupling between the electronic states and the local structural degrees of freedom. In many instances direct quantitative measures of these attributes would contribute immensely to the level of understanding.
Classic diffraction techniques will continue to play an important role but other methodologies are necessary if this local structural response is to be fully described. For the former, i.e. diffraction, structure refinement techniques which wholly address both the crystalline and diffuse portions of the scattering profiles would be a tremendous advance. The latter component will entail a heavier reliance on a variety of powerful probes of local structure including nuclear magnetic resonance, scanning tunneling microscopy, anomalous scattering methods and radial distribution analysis . As the number of chemical/structural architectures available continues to increase, determining the fundamental nature of the structure/property interrelationships will become an ever more important issue in the future.
Much of the research by the Wisconsin group is the result of major contributions by students and collaborators. I gratefully acknowledge D. Chen, P. Davis, J.E. Fischer, F.E. Karasz, A.J. Heeger, G. Mao and T. Prosa for their efforts. This work was supported by the National Science Foundation under Grant DMR 9305289.