Study of Polyanilines by High-Resolution Electron Microscopy

A chemically prepared emeraldine chloride powder has been studied by high-resolution electron microscopy. Two kinds of grains with varying degrees of crystallinity were observed: (i) Rolled sheets (20−100 nm in diameter) (aggregates, disks, or ribbons?) with an amorphous surface layer are identified as the EB-II polymer polymorph because of the centering of the cell and characteristic interreticular distances. A periodicity (∼5 nm) ascribed to the growth irregularity of the pristine polymeric aggregate is observed around the catalytic center. (ii) Crystalline grains (20−50 nm) exhibiting well-characterized 0.59-nm interreticular spacing are identified as the ES-I emeraldine salt. The interchain structural order appears stronger than the order along the polyaniline chain, according to the bond angle flexibility. The observed concentric nanostructure supports both the sketch of ordered islands and the paracrystal descriptions.