Molecular motion and conformational defects in odd-numbered paraffins

A small-angle x-ray diffraction study using synchrotron radiation of paraffins ${\mathrm{C}}_n{\mathrm{H}}_{2n+2}$ with $19\le n\le 27$ as a function of the temperature allowed us to characterize the molecular disorders of the rotator phases, associated with longitudinal molecular motions and conformational defects of the molecular chains. The magnitude of these disorders increases with the molecular length, in agreement with previous infrared-spectroscopy results. Indications of correlations between the concentration of conformational defects, amplitude of the longitudinal motion, and orientational molecular disorder were established.