Crystallography of waxes - an electron diffraction study of refined and natural products

Abstract

The crystal structure of four waxes has been investigated by electron crystallography. Two of these waxes, including a refined petroleum product (Gulfwax) and a material from lignite (montan wax), form well ordered crystals and their structure could be solved quantitatively from the observed diffraction patterns. As also found previously for simpler binary n-paraffin solid solutions, the average structure resembles that of a pure paraffin (e.g. n-) but with a Gaussian distribution of atomic occupancies near the chain ends to account for the statistical distribution of chain lengths within a lamella. Two other waxes from living organisms, South African bee honeycomb and the leaves of the Brazilian carnauba palm, are much less ordered, even though they share the same methylene subcell packing of the most crystalline parts of the previous materials. It appears that these waxes cannot fully separate into distinct lamellae, perhaps due to the presence of very long `tie' molecules, and are therefore `frustrated' crystal structures.