Solid-phase behavior of several long-chain n-paraffins, esters, and a ketone

Sullivan, Peter K.

doi:10.6028/jres.078a.009

Cited by 36 publications

(13 citation statements)

References 14 publications

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“…18,19 Single crystals grown from solution show a monoclinic crystal structure with a d-spacing of roughly 52 Å. 21,[23][24][25] When exposed to temperatures near the alkane melting temperature, a transformation into an orthorhombic structure 7,18,[23][24][25][26][27] with an increased d-spacing of roughly 58 Å can be achieved. In addition, a triclinic phase 21 and also a rotator phase 28 have been reported.…”

Section: Introductionmentioning

confidence: 99%

Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

Pithan

Meister

Jin

et al. 2015

The Journal of Chemical Physics

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We use thermal annealing to improve smoothness and to increase the lateral size of crystalline islands of n-tetratetracontane (TTC, C44H90) films. With in situ x-ray diffraction, we find an optimum temperature range leading to improved texture and crystallinity while avoiding an irreversible phase transition that reduces crystallinity again. We employ real-time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of TTC across monomolecular step edges which causes the unusual smoothing of a molecular thin film during annealing. We show that the lateral island sizes increase by more than one order of magnitude from 0.5 μm to 10 μm. This desirable behavior of 2d-Ostwald ripening and smoothing is in contrast to many other organic molecular films where annealing leads to dewetting, roughening, and a pronounced 3d morphology. We rationalize the smoothing behavior with the highly anisotropic attachment energies and low surface energies for TTC. The results are technically relevant for the use of TTC as passivation layer and as gate dielectric in organic field effect transistors.

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Section: Introductionmentioning

confidence: 99%

Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

Pithan

Meister

Jin

et al. 2015

The Journal of Chemical Physics

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“…A sharp increase in intensity as well as a change in the long period was observed at the solidsolid transition temprature. 3 On the other hand, these changes occurred for n-C 94 H 190 with no thermal indication of the first-order transition. 6 A similar observation was reported for hexacontane (n-C60H122), heptacontane (n-C70H142), and octacontane (n-C 80 H 162 ).…”

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confidence: 94%

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

Takamizawa

Ogawa

Oyama

1982

Polym J

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ABSTRACT:The general principle for synthesizing higher n-alkanes of the highest purity is described briefly. Thermal behavior of the synthesized n-alkanes from n-C32H66 to n-C80H162 were examined by means ofDSC, small-and wide-angle X-ray scattering and optical microscopy. All the crystalline n-alkanes except for n-C80H162 , when crystallized from solution, showed transitions to high-temperature monoclinic modifications (M. 01 , h =I or 2) before the rotator transition or the melting, irrespective of the number of carbon atoms (n) being odd or even and the difference in room-temperature modifications of even n-alkane. One feature of the transition was its bility. The odd n-alkanes of n-C33H68, n-C37H76, and n-C45 H92 showed also another type of solidsolid transition below the transition mentioned above. Both types of the transitions were thermally proved to be of the first-order. Although no simple functional forms were generally given to the relationships between the transition temperature and n, the temperatures for the transition of orthorhombic higher n-alkanes to the M.0. 1 phase increased with n, reaching about 90°C for n-C69H140. The transition to M•01 was accompanied by a morphological change on the crystal surface, in the form of characteristic striations parallel to the b, subcell axis. This suggests that the solid-solid transition proceeds successively from a nucleating site with a staggering of molecules in the chain direction. If the slow rate of the process and complicated behavior of the M•01 phase are taken into account, the kinetical view point of the phase transition leads to the working hypothesis that the molecular motion of the long chains in the n-alkane crystals, which consists of rotational and longitudinal motions or a flip-flop motion, takes place only in this transformation process.KEY WORDS Higher n-Alkanes I Synthesis I DSC I Small-Angle X-Ray Diffraction I Thermal Behaviors I Solid-Solid Phase Transition I Crystalline n-alkane homologues have been studied as a simple model system to obtain insight into the thermal behavior of the polyethylene crystal in particular and polymeric crystals in general. Of particular interest is the first-order solid-solid transition observed for solution-grown crystals of heptacosane (n-C27 H 56 ), 1 tritriacontane (n-C33H68),2 hexatriacontane (n-C36 H74)1.3· 4 and tetratetracontane (n-C 44 H 90 ), 3 besides (if present) a transition to a phase generally called as the rotator phase. The heat of this transition is much smaller than the heat of fusion and even than that of the rotator transition. Another feature of the transition is its irreversibility.Transformations in the crystalline forms may be schematically described in terms of the model structures proposed by Keller 5 for crystalline n-alkanes. For then-alkanes discussed below, four methylene groups in the two chains are considered to occupy an identical orthorhombic subcell, irrespective of the . differences in modification and chain length. End methyl groups form a terminal plane indexable in te...

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“…As seen in Figure (a), butyl stearate and OCBS‐1 have three peaks during melting or freezing processes: the largest peak α and two small peaks β and γ. Peak α is attributed to the solid–liquid phase‐transition process, while the two small peaks are attributed to the solid–solid phase transition of butyl stearate . Since OCBS‐1 contains the largest proportion of butyl stearate among the OCBS series, it also shows three peaks in melting or freezing processes, while these two small peaks are too weak to be seen in OCBS‐2 and OCBS‐3.…”

Section: Resultsmentioning

confidence: 99%

Investigations on thermal properties of microencapsulated phase‐change materials with different acrylate‐based copolymer shells as thermal insulation materials

Yan

Xie

Wang

2019

J of Applied Polymer Sci

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A series of microencapsulated phase‐change materials (micro‐PCMs) with binary cores and acrylate‐based copolymer shells were prepared. The micro‐PCMs contained octadecane and butyl stearate as binary‐core materials. Allyl methacrylate, ethylene glycol dimethacrylate, 1,4‐butanediol diacrylate (BDDA), and 1,6‐hexanediol dimethacrylate were respectively introduced to copolymerize with divinylbenzene (DVB) to form different microcapsule shells. In this work, the influence of the types of core and shell materials and core–shell weight ratios on the thermal properties of micro‐PCMs was studied. The chemical structures, morphologies, thermal properties, and thermal insulation properties of the wallboards were all tested and discussed. Scanning electron microscope photographs show that these micro‐PCMs have relatively spherical profiles and compact surfaces with diameters ranging from 10 to 80 μm. Differential scanning calorimetry results indicated that their microencapsulation efficiency ranged from 48 wt % to 80 wt %. A thermogravimetric analysis demonstrated that these micro‐PCMs can ensure their thermal stability below 210°C. Finally, a thermal insulation wallboard fabricated with synthesized P(BDDA‐co‐DVB) micro‐PCMs showed excellent thermal energy storage performance, keeping the temperature fluctuation within 2.5°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47777.

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Solid-phase behavior of several long-chain n-paraffins, esters, and a ketone

Cited by 36 publications

References 14 publications

Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

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

Investigations on thermal properties of microencapsulated phase‐change materials with different acrylate‐based copolymer shells as thermal insulation materials

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