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Dai L, Chakraborty S, Wu G, Ye J, Lau YH, Ramanarayan H, Wu DT. Molecular simulation of linear octacosane via a CG10 coarse grain scheme. Phys Chem Chem Phys 2022; 24:5351-5359. [PMID: 35169819 DOI: 10.1039/d1cp05143a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Following our previous work on the united-atom simulation on octacosane (C28H58) (Dai et al., Phys. Chem. Chem. Phys., 2021, 23, 21262-21271), we developed a coarse grain scheme (CG10), which is able to reproduce the pivotal phase characteristics of octacosane with highly improved computational efficiency. The CG10 octacosane chain was composed of 10 consecutive beads, maintaining the fundamental zigzag chain morphology. When the potential functions were set up and the coefficients were parameterized, our CG10 models yielded solid phase diagrams and transitions during an annealing process. We also detected the melting point by various means: direct observation, bond order, density tracking, and an enthalpy plot. Furthermore, our CG10 successfully reproduced the liquid density with only 2% underestimation, indicating its applicability across the solid and liquid phases. Therefore, with the ability to reproduce critical structure and property characteristics, our CG10 scheme provides an effective means of numerically modelling octacosane with highly improved computational efficiency.
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Affiliation(s)
- L Dai
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - S Chakraborty
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - G Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - J Ye
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - Y H Lau
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - H Ramanarayan
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - D T Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
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Dai L, Rutkevych PP, Chakraborty S, Wu G, Ye J, Lau YH, Ramanarayan H, Wu DT. Molecular dynamics simulation of octacosane for phase diagrams and properties via the united-atom scheme. Phys Chem Chem Phys 2021; 23:21262-21271. [PMID: 34543374 DOI: 10.1039/d1cp02720d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We used the united-atom scheme to build three types of crystalline structures for octacosane (C28H58) and carried out molecular dynamics simulations to investigate their phase properties. By gradually heating the three polymorphs, we managed to reproduce the sequence of experimentally reported crystalline phases and rotator phases. By studying the system density, molecule morphology, chain tilt angle and cell anisotropy, we hypothesized three mechanisms behind the observed system deformations and phase transformations during the annealing process. Furthermore, our model successfully predicted the melting temperature and heat of fusion. We also reproduced the characteristics of the rotator phases and the liquid phase, validating the transferability of the united-atom scheme among the different condensed phases of octacosane. Our methodology represents an effective and efficient means of numerical study for octacosane and may be used for other members of the n-alkane family.
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Affiliation(s)
- L Dai
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - P P Rutkevych
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore
| | - S Chakraborty
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - G Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - J Ye
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - Y H Lau
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - H Ramanarayan
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - D T Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
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Collett JA, Martinez Zambrano D. Using dislocations to probe surface reconstruction in thick freely suspended liquid crystalline films. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:040501. [PMID: 26565149 DOI: 10.1103/physreve.92.040501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 06/05/2023]
Abstract
Surface interactions can cause freely suspended thin liquid crystalline films to form phases different from the bulk material, but it is not known what happens at the surface of thick films. Edge dislocations can be used as a marker for the boundary between the bulk center and the reconstructed surface. We use noncontact mode atomic force microscopy to determine the depth of edge dislocations below the surface of freely suspended thick films of 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) in the crystalline B phase. Here, 3.0±0.1 nm high steps are found with a width that varies with temperature between 56 and 59°C. Using a strain model for the profile of liquid crystalline layers above an edge dislocation to estimate the depth of the dislocation, we find that the number of reconstructed surface layers increases from 4 to 50 layers as the temperature decreases from 59 to 56°C. This trend tracks the behavior of the phase boundary in the thickness dependent phase diagram of freely suspended films of 7O.7, suggesting that the surface may be reconstructed into a smectic F region.
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Affiliation(s)
- J A Collett
- Department of Physics, Lawrence University, 711 East Boldt Way, Appleton, Wisconsin 54911, USA
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Affiliation(s)
- Eric B. Sirota
- Corporate Strategic Research, ExxonMobil Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801
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Yang L, Fukuto M. Modulated phase of phospholipids with a two-dimensional square lattice. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:010901. [PMID: 16089928 DOI: 10.1103/physreve.72.010901] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Indexed: 05/03/2023]
Abstract
We report an observation of a modulated phase of phospholipids in which intrabilayer density modulations form an in-plane square lattice. Similar to the well-known ripple (P'(beta)) phase, this phase can be induced by either dehydration or cooling from the liquid crystalline (L(alpha)) phase. However, further lowering of hydration or temperature induces either an untilted straight-chain gel phase (L(beta)) , or the tilted L'(beta) phase after a brief appearance of the P'(beta) phase. The structural characteristics of this phase support the notion that the coupling between variations in local chain tilt and bilayer shape plays an important role in the formation of modulated phases.
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Affiliation(s)
- Lin Yang
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA
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Herhold AB, King HE, Sirota EB. A vanishing nucleation barrier for the n-alkane rotator-to-crystal transformation. J Chem Phys 2002. [DOI: 10.1063/1.1470197] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Sirota EB. Compositionally modulated phase in crystalline n-alkane mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 64:050701. [PMID: 11735885 DOI: 10.1103/physreve.64.050701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2001] [Indexed: 05/23/2023]
Abstract
We report an x-ray scattering study of the compositionally modulated microphase separated state (muPSS) of binary n-alkane (C23H48:C28H58) mixtures. By employing a quenching technique, we obtained many orders of sharp lamellar and superlattice reflections. The muPSS is a regular superstructure consisting of pure C23 layers, and layers rich in C28 but containing up to approximately 14% C23 plus voids. A monolayer of the minority component regularly alternates with one or more layers of the majority. The mechanism for thermodynamic stability of the muPSS may be related to the entropy associated with longitudinal displacements of the molecules.
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Affiliation(s)
- E B Sirota
- Corporate Strategic Research, ExxonMobil Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801, USA.
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Sirota EB, Herhold AB, Varma-Nair M. Structure, thermodynamics, and transition kinetics of nonadecylcyclohexane. J Chem Phys 2000. [DOI: 10.1063/1.1314859] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Chen C, MacKintosh FC. Theory of modulated phases in lipid bilayers and liquid crystal films. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 53:4933-4943. [PMID: 9964822 DOI: 10.1103/physreve.53.4933] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Chen C, Lubensky TC, MacKintosh FC. Phase transitions and modulated phases in lipid bilayers. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1995; 51:504-513. [PMID: 9962669 DOI: 10.1103/physreve.51.504] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Lubensky TC, MacKintosh FC. Theory of "Ripple" Phases of Lipid Bilayers. PHYSICAL REVIEW LETTERS 1993; 71:1565-1568. [PMID: 10054440 DOI: 10.1103/physrevlett.71.1565] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Sirota EB, King HE, Hughes GJ, Wan WK. Novel phase behavior in normal alkanes. PHYSICAL REVIEW LETTERS 1992; 68:492-495. [PMID: 10045910 DOI: 10.1103/physrevlett.68.492] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Amador S, Pershan PS, Stragier H, Swanson BD, Tweet DJ, Sorensen LB, Sirota EB, Ice GE, Habenschuss A. Synchrotron studies of the first-order melting transitions of hexatic monolayers and multilayers in freely suspended liquid-crystal films. PHYSICAL REVIEW. A, GENERAL PHYSICS 1989; 39:2703-2708. [PMID: 9901543 DOI: 10.1103/physreva.39.2703] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Sirota EB, Pershan PS, Deutsch M. Modulated crystalline-B phases in liquid crystals. PHYSICAL REVIEW. A, GENERAL PHYSICS 1987; 36:2902-2913. [PMID: 9899196 DOI: 10.1103/physreva.36.2902] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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