NOVEL PHASE-BEHAVIOR IN NORMAL ALKANES

X-ray scattering studies on aligned films of binary mixtures of the normal alkanes C23H48 and C28H58 reveal, for the first time in such materials, the existence of a new equilibrium phase having the symmetry of a smectic liquid crystal, possibly a hexatic. This phase occurs between the hexagonally packed R(II) and the lower-temperature orthorhombic R(I) plastic crystalline, layered, rotator phases. We argue that this loss of order is due to local distortion fluctuations in the hexagonal phase. Furthermore, we have identified an ABC-to-ABAB restacking transition within the ordered R(II) phase.