Rotational diffusion in the rotator phase of n-alkanes

Abstract

From quasielastic neutron scattering experiments performed in the rotator phase of n-alkanes (CnH2n+2), as a function of both n and temperature, two types of rotational diffusion have been detected. Type B corresponds to a uniform rotational diffusion, whereas type A corresponds to a hindered rotation, probably limited to large amplitude oscillations. It is the first time that type A rotational diffusion, given by the orthorhombic symmetry phase RI, is observed. On increasing the temperature it rapidly evolves towards the type B diffusion. Correlation times τ which seem to be rather independent of the phase type are of the order of 5×10−12 s.

Structure formation of a single polymer chain. I. Growth of trans domains

“…Structure formation or self-organization of chain molecules, such as n-alkanes, polyethylene chains, and lipid molecules, has recently become the focus of attention in physics, chemistry, biology, and materials science. The crystal structure of the rotator phase of n-alkanes has been extensively studied by several experimental techniques including x-ray diffraction, 1-4 infrared and Raman spectroscopy, 5,6 neutron scattering, 7,8 and nuclear magnetic resonance. 9 The primary nucleation in the crystallization induction period of polyethylene [10][11][12] and poly͑ethylene terephthalate͒ [13][14][15][16][17][18] has been investigated by various time-resolved measurements.…”

Variation in enthalpy of the systemn-tetracosane-n-hexacosane as functions of temperature and composition

“…With increasing temperature, 7t and 5' 2 behave in the same way as n-tetracosane and n-hexacosane [2,[13][14][15]. The solutions [3{, 13" and 13~ undergo the same solid-state transitions as those observed in n-tricosane [2,[6][7][8][9][10][11][12] and in the binary system n-docosane-n-tetracosane [12,15].…”

Order-Disorder Transition during Approach and Separation of Two Parallel Surfaces

“…As the distance is decreased, ry increases, reaching a value that is 2 to 3 orders of magnitude higher than the value at large distances. The relaxation time at large distance is similar to the relaxation time in the rotator phase of n-alkanes [18,19], and the relaxation time in the rotator phase of a model n-alkyl thiol monolayer [17],and model Langmuir monolayers [15]. By analogy with crystal alkanes, the monolayer at large distances must also be in a free rotator phase.…”