The role of hydrogen bonding in the cuticular wax of Hordeum vulgare L.

The role of hydrogen bonding in the cuticular wax of Hordeum vulgare L. has been investigated by comparing differential scanning calorimetry and X-ray powder diffraction results of the wax with those of n-alkane mixtures with chain-length distributions resembling that of the wax. It is concluded that hydrogen bonding prevents separation of the short and long chain-length distributions and results in the formation of an amorphous component which is large compared with that of a typical paraffinic wax. It seems that the longer ester chains (39 ≥n≥ 50) bridge the amorphous zone containing chain-ends between two adjacent layers of shorter chains (20 ≥n≥ 33), where n is the number of carbon atoms per chain. In contrast to a paraffinic wax, which has a monolayered structure, this plant wax has a bilayered structure.