X-RAY STRUCTURE OF POLYANILINE

We distinguish between two classes of the emeraldine form of polyaniline. Class I emeraldine is that for which the conducting HCl salt exhibits ES-I crystal structure and the insulating base form is essentially amorphous EB-I. In general, class I materials are formed when the polymer is obtained from solution in the protonated form. Samples of polyaniline belonging to class II possess ES-II structure in the conducting HCl salt form and EB-II structure in the insulating base form. Emeraldine samples belonging to class II were prepared originally in the nonprotonated form. The crystalline components of ES-I, EB-II, and ES-II have been analyzed, and basic parameters of the structures have been derived from comparison between diffraction patterns and intensity calculations. EB-II has a structure similar to that of chemically analogous polymers such as poly(phenylene sulfide) and poly(phenylene oxide). ES-I and ES-II structures differ substantially in their compactness. In class I the increase of crystallite size and decrease in interchain separation with protonation correlate with increasing three-dimensional delocalization of charge with increasing protonation. In contrast, in partially crystalline EB-II, initially protonation occurs in amorphous regions with only subsequent doping into the crystalline areas.