Study of polyanilines by high-resolution electron microscopy

A chemically prepared emeraldine chloride powder has been studied by high-r esolution electron microscopy. Two kinds of grains with varying degrees of crystallinity were observed: (i) Rolled sheets (20-100 nm in diameter) (agg regates, disks, or ribbons ?) with an amorphous surface layer are identifie d as the EB-II polymer polymorph because of the centering of the cell and c haracteristic interreticular distances. A periodicity (similar to 5 nm) asc ribed to the growth irregularity of the pristine polymeric aggregate is obs erved around the catalytic center. (ii) Crystalline grains (20-50 nm) exhib iting well-characterized 0.59-nm interreticular spacing are identified as t he ES-I emeraldine salt. The interchain structural order appears stronger t han the order along the polyaniline chain, according to the bond angle flex ibility. The observed concentric nanostructure supports both the sketch of ordered islands and the paracrystal descriptions.