AFM-TEM observations of effect of ``melt'' time on polytetrafluoroethylene morphology.

TEM observations of PTFE dispersion particles dispersed on glass and held at 350 \r{ }C or above for various times indicates that individual, $>$ 0.1 mm long molecules wander individually on the substrate and can, with time in the ``melt,'' aggregate and form either flat-on or on-edge, folded chain single crystals. If ``trapped'' by cooling before aggregation, on-edge, single molecule, single crystals can form. All on-edge crystals, both individually and as the shish of shish-kebabs, have a ``double-striation'' appearance, suggested to arise from nucleation of the Pt/C shadowing material, used for the TEM image, on the folds at the top edge of the crystals.\footnote{P. H. Geil, \textit{et al}., Adv. Polym. Sci., 180, 89 (2005).} AFM observations have confirmed these suggestions and, furthermore, indicate the nascent, rod-like dispersion particles of a ``nano-emulsion,'' with a volume corresponding to a single molecule, have faceted ends. Combined with the TEM and ED observations that the molecular axis is parallel with the rod axis, not only must chain-folding occur during polymerization but the chain folds must be staggered on the end surfaces.