Phase-Transitions in Crystals of Chain Molecules. Relation between Defect Structures and Molecular Motion in the four Modifications of n-C33H68

Abstract

n-Tritriacontane (n-C33H68) exhibits three solid–solid phase transitions before melting. Applying a variety of experimental techniques, including X-ray scattering, Raman spectroscopy, n.m.r., dielectric relaxation and quasielastic neutron scattering, it was possible to specify for all four modifications defect structures and the corresponding molecular motions.Each phase transition is accompanied by a step-like decrease in the degree of order resulting from the successive onset of rotational jumps, translational jumps in chain direction and the creation and diffusion of intrachain defects.