Electron crystallography of the polymethylene chain.: 2.: The lamellar interface of n-paraffin solid solutions

Electron diffraction measurements were made on a series of binary solid solutions formed from n-C24H50 and n-C26H54. When the longer chain is most dilute, crystal structure analyses favor a mixed-chain packing arrangement, based on an average n-C25H52 layer, a model that can incorporate the chain-end conformational disorder measured by vibrational spectroscopy. Published x-ray data from a 3.1 binary combination can also be interpreted to support this model. The alternative view, requiring an all-trans chain with methyl groups from the longer chain component protruding into the lamellar interface, is neither consistent with the spectroscopic measurements nor with independent measurements of lamellar surface flatness.