Phase Diagram ofn-Tricosane andn-Pentacosane Mixtures

Normal Alkanes, Multialkane Synthetic Model Mixtures, and Real Petroleum Waxes: Crystallographic Structures, Thermodynamic Properties, and Crystallization

“…From the structural observations of Smith 143 and Gerson and Nyburg 26 and the phase diagrams determined by Lüth et al (C 20 /C 22 ), by Achour et al , (C 22 /C 24 and C 24 /C 26 ), , by Denicolo et al and Nouar et al (C 22 /C 23 ), by Nouar et al (C 23 /C 24 ), and by Jouti et al ,,, (C 21 /C 23 and C 23 /C 25 ), Dirand et al , established a generalization of the thermodynamic and structural behavior of the binary mixtures of consecutive C n 's (Δ n c ≤ 2) (20 ≤ n c ≤ 26) as follows.…”

“…(1) Binary Mixtures of Consecutive C n 's ( Δ n c ≤ 2). The binary mixtures of C n 's have been the subject of numerous articles. ,,,,− ,,, Many phase diagrams have been presented with an orthorhombic continuous solid solution at room temperature even if the two pure C n 's displayed a ( n c − n c ‘ )/ n c relative gap between the chain lengths of molecules which was too high, according to Kravchenko's rule (Table ), and/or a triclinic or monoclinic phase not compatible with Palatnik and Landau's rule: for instance, (C 18 /C 20 ; C 19 /C 21 ; C 21 /C 23 ; C 22 /C 23 ; C 22 /C 24 ; C 24 /C 26 ; C 30 /C 35 ; C 35 /C 36 ), (C 21 /C 23 ), (C 19 /C 21 ), (C 24 /C 28 ) …”

Phase Transition Behavior of a Series of Even n-Alkane Cn/Cn+2 Mixtures Confined in Microcapsules: From Total Miscibility to Phase Separation Determined by Confinement Geometry and Repulsion Energy

“…However, the temperature hysteresis between the bulk and microcapsule for C n /C n +2 = 90/10 mixtures is larger than that for C n /C n +2 = 10/90 mixtures. As we all know when mixing two n -alkanes with different chain lengths, the terminal CH 3 –CH 3 interactions of crystal phases are greatly weakened due to the chain length difference. , For C n /C n +2 = 90/10 mixtures, a small amount of C n+2 with longer chain length can easily destroy the layered structure. Therefore, the CH 2 –CH 2 intermolecular interactions become dominant, and the formation of an orthorhombic rotator phase is preferred, leading to a more stable rotator phase and less stable triclinic phase. , Otherwise, for C n /C n +2 = 10/90 mixtures, the C n with a shorter chain length is the minor component, the crystal lattice of the C n +2 will be less affected by the mixing, and the C n molecules can be easily excluded from the crystal lattice of C n +2 .…”

“…However, n -alkane mixtures are more common in practical applications such as the phase change materials (PCMs) and are frequently used as model systems at the molecular level, especially for polydisperse polyethylene. Some previous work indicated that mixing different chain lengths of alkanes reduces the interaction of interlayer coupling and increases void volume and lamellar surface roughness, thus leading to a dramatic influence on the phase behaviors of n -alkane mixtures. − One of the specific phase behaviors in these systems is that the stability of the rotator phase is enhanced. , In addition, binary n -alkane mixtures have been proven to undergo a phase separation process in low-temperature ordered crystals, which endows the mixtures with particular desirable properties. It has been shown that chain length difference is one of the major factors that can greatly affect the phase separation .…”

“…As we all know when mixing two n-alkanes with different chain lengths, the terminal CH 3 −CH 3 interactions of crystal phases are greatly weakened due to the chain length difference. 12,13 For C n /C n+2 = 90/10 mixtures, a small amount of C n+2 with longer chain length can easily destroy the layered structure. Therefore, the CH 2 −CH 2 intermolecular interactions become dominant, and the formation of an orthorhombic rotator phase is preferred, leading to a more stable rotator phase and less stable triclinic phase.…”