Melt-Crystallization of Hexatriacontane (n-C₃₆H₇₄) in a Temperature Gradient

Abstract

In order to study conformational change through a phase transition, the bulk sample of n-hexatriacontane (n-C₃₆H₇₄) was investigated by the X-ray diffraction method during crystallization in a temperature gradient. In the first stage of crystallization, the monoclinic rotator phase arises from a melt state, whose crystalline constants are a=4.98 Å, b=8.62 Å, c=48.10 Å, β=107.0°. By the second transition from the rotator phase, the monoclinic crystal is formed, whose unit cell dimensions are a=7.76 Å, b=4.90 Å, c=48.27 Å, β=106.0°. The both crystalline structures show that the chain axes are tilted from the layer plane.The second transition is performed by the change in the tilt direction of the molecules and by the anisotropic contraction of the intermolecular distances.