Investigation into the structures of some normal alkanes within the homologous series C13H28 to C60H122 using high-resolution synchrotron X-ray powder diffraction

Abstract

High-resolution X-ray powder diffraction using synchrotron radiation has been used to determine the unit-cell parameters of some of the n-alkanes within the range C, , H2, -C, , H, 22.These have, in general, been found to conform to the structural patterns predicted by Nyburg and Potworowski (Acta Crystallogr., Sect. B, 1973, 29, 347). Polymorphic behaviour has been observed for the n =even alkanes associated with increasing symmetry from a triclinic structure (space group Pl), to a monoclinic structure (space group P2,/a) and to an orthorhombic structure (mostly space group Pca2,) as the chain length increases. The n-alkanes C38H78, C4,,Hs2 and C44H90 were found to crystallize in the polytypic orthorhombic polymorph (space group Pbca) proposed by Boistelle et a/.

Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

“…Also, for both substrates at sufficiently high coverage, preferentially oriented bulk particles coexist with the film, as in Stranski-Krastanov growth. On the SiO 2 surface, two series of bulk Bragg peaks are observed, corresponding to particles of a surface stabilized orthorhombic phase as well as the previously reported monoclinic structure [7], both oriented with the ab-plane parallel to the film plane, as shown schematically in figure 3 [6].…”

Nanoscale observation of delayering in alkane films

“…These features cannot be indexed by the bulk monoclinic structure reported for C32 at room temperature [15].…”

New insights on the crystalline forms in binary systems of n-alkanes: Characterization of the solid ordered phases in the phase diagram tricosane + pentacosane

“…C (1) 0.014 0.186 0.0239 0.90 C (2) 0.092 0.314 0.0435 1.00 C (3) 0.014 0.186 0.0631 1.00 C (4) 0.092 0.314 0.0827 1.00 C (5) 0.014 0.186 0.1023 1.00 C (6) 0.092 0.314 0.1219 1.00 C (7) 0.014 0.186 0.1415 1.00 C (8) 0.092 0.314 0.1611 1.00 C (9) 0.014 0.186 0.1807 1.00 C (10) 0.092 0.314 0.2003 1.00 C (11) 0.014 0.186 0.2199 1.00 C (12) 0.092 0.314 0.2395 1.00 C (13) 0.014 0.186 0.2591 1.00 C (14) 0.092 0.314 0.2788 1.00 C (15) 0.014 0.186 0.2987 1.00 C (16) 0.092 0.314 0.314 1.00 C (17) 0.014 0.186 0.3376 1.00 C (18) 0.092 0.314 0.314 1.00 C (19) 0.014 0.186 0.3770 1.00 C (20) 0.092 0.314 0.3964 1.00 C (21) 0.014 0.186 0.4160 1.00 C (22) 0.092 0.314 0.4356 1.00 C (23) 0.014 0.186 0.4552 1.00 C (24) 0 and binary mixed samples do not change significantly with chain length), and z͞c coordinates were obtained by extrapolation along the z-axis of the chain model used by Dorset. 51 The fractional atomic occupancies (see Table I) which are applied to the chain ends have no effect on the angular position of the diffraction lines if not on the intensities and specially those of the 00l lines.…”