Scientists in Germany observed platelets of mono-lamina polyethylene crystal dispersed in water under cryo-TEM (Nano Lett. ASAP Article. DOI: 10.1021/nl070859f).

The polyethylene is synthesized via a newly developed nickel-catalyzed aqueous polymerization. The growing polymer chains fold into mono-crystalline hexagonal platelets, with monodispersed diameters and thickness of 25 nm and 6.3 nm, respectively, as observed under cryogenic transmission electron microscope (cryo-TEM) which is suited for in situ observation of object in water. Wide and small X-ray scattering results confirmed the crystallinity of these nano-crystallites and, most significantly, obtain a larger thickness, 9 nm, than the value from cryo-TEM observation. The additional thickness invisible under cryo-TEM is interpreted as the amorphous layer of the polymer chain.

According to Fischer’s model of polymer chain folded single crystal (check your Polymer Physics textbook), the surface of the lamina consists of the bending sites of the folded polymer chain, which is much less ordered compared with the inner region of the crystallite. so the two sides of the crystalline platelet should be covered with amorphous layers.

So the cryo-TEM image and SAXS of this paper is the best supporting figure for the a Polymer Physics textbook, beside the scheme describing Fischer or Flory’s folded chain model of polymer crystal.