The intensity as a function of temperature of the low-angle x-ray diffraction maxima of the n-paraffins: Hexatriacontane, tetratetracontane, and tetranonacontane

Abstract

The diffrac tion of x-rays by the crystalline n-paraffin s, C36 H ' 4 , C4.H"o, and C". H ",o, was examin e d a t s mall angles -be low se ve n deg re es 2IJ -as a fun c tion of te mp e rature. The Bragg maxima (001) that occ ur at these ang les res ult from a la mell a r re peat di sta nce whic h de pe nd s on th e molec ul a r length. I n ge ne ral the inte nsity of th ese maxim a was found to inc rease with increas ing te mp e rature in a n approximately re versible manne F. All the samp les exp e rie nce d so lid-so lid ph ase tra nsitions in th e te mperature ran ge of observa tion. S eve ral possibl e mecha ni s ms co ns iste nt with th e te mp e rature d e pendence of the inte nsity are considered .

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.…”

“…23 All these forms have the same space group [4][5][6]23 ͑P 21/a , Z 2͒ but differ by the shift of adjacent molecules in the planes (b ‫ء‬ c for M 011 and M 012 and a ‫ء‬ c for M 201 and M 101 ) of a whole number of CH 2 units. In the M hkl notation, the ͑hkl͒ describes the plane formed by the methyl end groups (CH 3 ) in the referential of the orthorhombic subcell.…”

Thermal Behavior of n-Alkanes from n-C32H66 to n-C80H162, Synthesized with Attention Paid to High Purity

“…14, No. 6,1982 radiation. A strip I mm thick and 10 mm long, cut from a single crystal mat was fitted to a holder and covered with a metal block having beryllium windows and a thermostat installed.…”

“…This form has been denoted as M101 according to the Sullivan-Weeks ··notation. 6 In the phase C, disorders alongside the chain axis are introduced. The superposition of "flip-flop" screw jumps, which were proposed by Olf and Peterlin, 29 • 30 onto the pure rotational jumps was first assumed.…”

“…14, No. 6,1982 number of carbon atoms differed by 40. Methods for obtaining pure higher n-alkanes are given.…”